Hydromax Manual

Hydromax Windows Version 11.0

User Manual

© Formation Design Systems Pty Ltd 1984 - 2004

License and Copyright Hydromax Program © 1985-2004 Formation Design Systems. Hydromax is copyrighted and all rights are reserved. The license for use is granted to the purchaser by Formation Design Systems as a single user license and does not permit the program to be used on more than one machine at one time. Copying of the program to other media is permitted for back-up purposes as long as all copies remain in the possession of the purchaser. Hydromax User Manual © 2004 Formation Design Systems. All rights reserved. No part of this publication may be reproduced, transmitted, transcribed, stored in a retrieval system, or translated into any language in any form or by any means, without the written permission of Formation Design Systems. Formation Design Systems reserves the right to revise this publication from time to time and to make changes to the contents without obligation to notify any person or organization of such changes. DISCLAIMER OF WARRANTY Neither Formation Design Systems, nor the author of this program and documentation are liable or responsible to the purchaser or user for loss or damage caused, or alleged to be caused, directly or indirectly by the software and its attendant documentation, including (but not limited to) interruption on service, loss of business, or anticipatory profits. No Formation Design Systems’ distributor, agent, or employee is authorized to make any modification, extension, or addition to this warranty.

iii

Contents

Contents License and Copyright...................................................................................................... iii Contents..............................................................................................................................v About this Manual ..............................................................................................................1 Chapter 1 Introduction........................................................................................................3 Chapter 2 Quickstart...........................................................................................................7 Upright Hydrostatics Quickstart ..............................................................................8 Large Angle Stability Quickstart .............................................................................9 Equilibrium Condition Quickstart..........................................................................10 Specified Condition Quickstart ..............................................................................11 KN Values Quickstart ............................................................................................12 Limiting KG Analysis Quickstart ..........................................................................13 Floodable Length Quickstart..................................................................................14 Longitudinal Strength Quickstart ...........................................................................15 Tank Calibrations Quickstart .................................................................................16 Chapter 3 Using Hydromax..............................................................................................17 Getting Started .......................................................................................................18 Installing Hydromax ....................................................................................18 Starting Hydromax.......................................................................................18 Hydromax Model ...................................................................................................19 Preparing a Design in Maxsurf ....................................................................20 Opening a New Design ................................................................................22 Opening an Existing Hydromax Design File ...............................................23 Updating the Hydromax Model ...................................................................25 Hydromax Sections Forming .......................................................................25 Checking the Hydromax model ...................................................................28 Analysis Input ........................................................................................................32 Setting Initial Conditions .............................................................................32 Loadcase ......................................................................................................34 Modelling Compartments ............................................................................38 Forming Compartments ...............................................................................47 Compartment Types.....................................................................................50 Damage Case Definition ..............................................................................54 Sounding Pipes ............................................................................................56 Key Points (e.g. Down Flooding Points) .....................................................58 Margin Line Points ......................................................................................60 Modulus Points and Allowable Shears and Moments .................................60 Stability Criteria...........................................................................................60 Analysis Types .......................................................................................................61 Upright Hydrostatics....................................................................................62 Large Angle Stability...................................................................................64 Equilibrium Analysis ...................................................................................67 Specified Conditions....................................................................................71 KN Values Analysis.....................................................................................73 Limiting KG.................................................................................................75 Floodable Length .........................................................................................79 Longitudinal Strength ..................................................................................82 Tank Calibrations.........................................................................................85 Starting and Stopping Analyses ...................................................................87 Batch Analysis .............................................................................................88 Analysis Settings....................................................................................................90 v

Contents

Heel..............................................................................................................90 Trim .............................................................................................................91 Draft .............................................................................................................92 Displacement ...............................................................................................92 Specified Conditions....................................................................................93 Permeability .................................................................................................93 Error Values.................................................................................................95 Analysis Environment Options ..............................................................................97 Fluids Simulation Method ...........................................................................97 Density .........................................................................................................98 Waveform ....................................................................................................99 Grounding ..................................................................................................100 Hog and Sag...............................................................................................101 Stability Criteria.........................................................................................102 Damage ......................................................................................................102 Analysis Output....................................................................................................103 Select View from Analysis Data................................................................104 Copying......................................................................................................105 Saving the Hydromax Design ....................................................................107 Exporting ...................................................................................................109 Chapter 4 Stability Criteria.............................................................................................111 Criteria Overview.................................................................................................112 Setting up Criteria - the Criteria Dialog ...............................................................113 Criteria Tree List........................................................................................115 Criteria Details...........................................................................................118 Criteria Help ..............................................................................................120 Criteria Results.....................................................................................................121 Importing and Saving Criteria Sets............................................................122 Nomenclature .......................................................................................................125 Definitions of GZ curve features: ..............................................................125 Glossary .....................................................................................................128 Parent Stability Criteria........................................................................................129 Criteria at Equilibrium ...............................................................................129 GZ Curve Criteria (non-heeling arm) ........................................................130 Heeling arm definition ...............................................................................150 Heeling arms for specific criteria - Note on unit conversion .....................156 Heeling arm criteria ...................................................................................161 Multiple heeling arm criteria .....................................................................178 Heeling arm, combined criteria..................................................................181 Other criteria ..............................................................................................188 Specific stability criteria ......................................................................................190 ISO 12217: Small craft – stability and buoyancy assessment and categorisation. ............................................................................................190 Chapter 5 Hydromax Reference .....................................................................................193 Windows ..............................................................................................................194 View Window ............................................................................................194 Loadcase Window......................................................................................196 Damage Window .......................................................................................196 Input Window ............................................................................................196 Results Window.........................................................................................198 Graph Window...........................................................................................200 Report Window..........................................................................................203 Toolbars ...............................................................................................................207

vi

Contents

Menus...................................................................................................................209 File Menu...................................................................................................209 Edit Menu ..................................................................................................210 View Menu ................................................................................................211 Analysis Menu ...........................................................................................212 Case Menu .................................................................................................216 Display Menu.............................................................................................217 Window Menu ...........................................................................................219 Help Menu .................................................................................................220 Appendix A Calculation of Form Parameters ...............................................................221 Definition and calculation of form parameters ..........................................221 Potential for errors in hydrostatic calculations ..........................................228 Reference Designs .....................................................................................229 Reference Calculations ..............................................................................230 Appendix B Criteria file format ....................................................................................232 Appendix C Reference Tables.......................................................................................236 File Extension Reference Table ...........................................................................237 Analysis settings reference table ..........................................................................238 Index...............................................................................................................................240

vii

About this Manual

About this Manual This manual describes how to use Hydromax to perform hydrostatic and stability analyses on you Maxsurf design. Chapter 1 Introduction Contains a description of Hydromax functionality and its interface to Maxsurf. Chapter 2 Quickstart Gives a quick walk through the analysis tools available in Hydromax. Chapter 3 Using Hydromax Explains how to use Hydromax's powerful flotation and hydrostatic analysis routines to best advantage. Chapter 4 Stability Criteria Gives details of the stability criteria that may be evaluated with Hydromax. Chapter 5 Hydromax Reference Gives details of Hydromax's windows and each of Hydromax's menu commands. If you are unfamiliar with Microsoft Windows® interface, please read the owner's manual supplied with your computer. This will introduce you to commonly used terms, and the basic techniques for using any computer program.

Page 1

Chapter 1 Introduction

Chapter 1 Introduction Hydromax is a hydrostatics, stability and longitudinal strength program specifically designed to work with Maxsurf. Hydromax adds extra information to the Maxsurf surface model. This includes: compartments and key points such as downflooding points and margin line. Hydromax’s analysis tools enable a wide range of hydrostatic and stability characteristics to be determined for your Maxsurf design. A number of environmental setting options and modifiers add further analysis capability to Hydromax. Hydromax is designed in a logical manner, which makes it easy to use. The following analysis steps are followed when performing analysis: • Input • Analysis selection • Analysis settings • Environment options • Output

Hydromax operates in the same graphical environment as Maxsurf; the model can be displayed using the contour lines, rendering or transparent rendering. This allows visual checking of compartments and shows intermediate stages during analysis. Input

Maxsurf design files may be opened directly into Hydromax, eliminating the need for time-consuming digitising of drawings or hand typing of offsets. This direct transfer preserves the three-dimensional accuracy of the Maxsurf model. Tanks can be defined and calibrated for capacity, centre of gravity and free surface moment. Tanks and compartments can be flooded for the purpose of calculating the effects of damage. A number of Loadcases can be created. The loadcase allows static weights and tankfillings to be specified and calculates the corresponding weights and centres of gravity. Other input consists of: sounding pipes; key points, such as downflooding points,, immersion and embarkation point; margin lines and section modulus.

Page 3

Chapter 1 Introduction Analysis

Hydromax contains the following analysis tools: • Upright hydrostatics • Large angle stability • Equilibrium analysis • Specified Condition analysis • KN values and cross curves of stability • Limiting KG analysis • Floodable Length analysis • Longitudinal Strength analysis • Tank Calibrations

Although common analysis settings are used where possible, different analyses may require different settings. For example: the upright hydrostatics analysis simply requires a range of drafts; whereas the longitudinal strength analysis requires a detailed load distribution. The analysis settings for each analysis type are explained in detail in the analysis synopsis below. Analysis Settings

The analysis settings describe the condition of the vessel to be tested. For example, a range of drafts in the case of upright hydrostatics, or a range of heel angles for a large angle stability analysis. The following analysis settings are available: • Heel • Trim • Draft • Displacement • Permeability • Specified conditions

The analysis settings are specified prior to running the analysis. Settings that are not relevant to the selected analysis type are greyed out in the Analysis menu. Environment Options

Environmental options are modifiers that may be applied to the model or its environment that will affect the results of the hydrostatic analysis. Depending on the analysis being performed, different environmental options may be applied to the Hydromax: • Type of Fluid Simulation • Density (of fluids) • Wave forms • Grounding • Hogging and sagging • Intact and Damage condition

Page 4

Chapter 1 Introduction Stability Criteria

Hydromax has an extensive range of stability criteria to check the analysis results for compliance with international stability regulations. Hydromax has a generic set of parent criteria from which most of the world’s stability criteria can be customized. Output

Views of the hull are shown for each heel and trim, complete with immersed sectional areas and actual waterlines. The centres of flotation, gravity and buoyancy are also displayed. Heeled and trimmed hull forms and water plane shapes may be printed. Results are stored and may be reviewed at any time, either in tabular form, or as graphs of the various parameters across the full range of calculation. All results are accumulated in the Report window, which can be saved, copied or printed for further reference. The criteria checks are summarised in tables listing pass/fail results of each criterion with its settings and intermediate calculation data if required.

Page 5

Chapter 2 Quick Start

Chapter 2 Quickstart This chapter will briefly describe each analysis type and its output. For each analysis type, a list of the required settings as well as the available environment options is given. Hydromax contains the following analysis types • Upright Hydrostatics • Large Angle Stability • Equilibrium Condition • Specified Condition • KN Values • Limiting KG Analysis • Floodable Length • Longitudinal Strength • Tank Calibrations

Each analysis has different settings that may be applied • Heel • Trim • Draft • Displacement • Specified conditions

• Permeability • Loadcase • Tank and compartment definition

Hydromax offers different environment options that may be applied to the analyses • Fluid Densities • Treatment of fluids in tanks: fluid simulation or corrected VCG • Wave form • Grounding • Hog and sag • Damage

Hydromax offers an extensive range of stability criteria that are applicable to equilibrium, large angle stability, limiting KG and Floodable length analysis. Chapter 3 Using Hydromax will describe each of the analysis types, settings and environment options in more detail.

Page 7

Chapter 2 Quick Start

Upright Hydrostatics Quickstart For Upright Hydrostatics, heel is fixed at zero heel, trim is fixed at a user defined value and draft is varied in fixed steps. Displacement and centre of buoyancy and other hydrostatic data are calculated during the analysis. Upright hydrostatics requirements • Range of drafts to be analysed • VCG • Trim

Upright hydrostatic options • Fluid Densities • Wave form • Hog and sag • Damage • Compartment definition (in case of damage)

The results are tabulated and graphs of the hydrostatic data, curves of form and sectional area at each draft are available. For more detailed information please see: Upright Hydrostatics on page 62.

Page 8

Chapter 2 Quick Start

Large Angle Stability Quickstart For the Analysis of Large Angle Stability, displacement and centre of gravity are specified in the loadcase. A range of heel angles are specified and Hydromax calculates the righting lever and other hydrostatic data at each of these heel angles by balancing the loadcase displacement to the hull buoyancy and, if the model is free-to-trim, the longitudinal position of centre of gravity and centre of buoyancy. Large angle stability requirements • Range of heel angles to be analysed • Trim (fixed or free) • Loadcase • Tank definition in the case of tank loads being included in the Loadcase (and/or for the definition of damage)

Large angle stability options • Fluid Densities • Treatment of fluids in tanks: fluid simulation or corrected VCG • Wave form • Hog and sag • Damage • Compartment definition (in case of damage) • Key points • Margin line and deck edge • Analysis of stability criteria

The key output value is GZ (or righting lever), the horizontal distance between the centres of gravity and buoyancy. A graph of these values at the various heel angles forms a GZ curve. Various other information is often overlaid on the GZ curve, including upright GM, curves for wind heeling and passenger crowding levers and the angle of the first downflooding point. These additional data depend on which (if any) stability criteria have been selected. The sectional area curve at each of the heel angles tested may also be displayed. If large angle stability criteria have been selected for analysis, these results will also be reported in the results table and they may lead to additional curves being added to the GZ curve. Downflooding angles for any key points, margin line and deck edge will also be computed and tabulated. For more detailed information please see: Large Angle Stability on page 64.

Page 9

Chapter 2 Quick Start

Equilibrium Condition Quickstart Equilibrium Analysis uses the Loadcase, to calculate the displacement and the location of the centre of gravity. Hydromax iterates to find the draft, heel and trim that satisfy equilibrium and reports the equilibrium hydrostatics and a cross sectional areas curve. Equilibrium analysis requirements • Loadcase • Tank definition in the case of tank loads being included in the Loadcase (and/or for the definition of damage)

• Compartment definition and damage case (in case of damage)

Equilibrium analysis options • Fluid Densities • Treatment of fluids in tanks: fluid simulation or corrected VCG • Wave form • Hog and sag • Grounding • Damage • Compartment definition (in case of damage) • Key points • Margin line and deck edge • Analysis of equilibrium criteria

Equilibrium analysis result table lists the hydrostatic properties of the model. The sectional area curve is also calculated, as is the freeboard to any defined key points margin line and deck edge. Any equilibrium criteria will also be evaluated and reported. For more detailed information please see: Equilibrium Analysis on page 67.

Page 10

Chapter 2 Quick Start

Specified Condition Quickstart In the specified condition each of the three degrees of freedom, for which the hydrostatic properties of the model are to be calculated, can be set. Specified Condition Requirements • Specified Conditions Input Dialog

If fixed trim is specified, you may enter the trim or specify the forward and aft drafts (these are at the perpendiculars as specified in the Frame of Reference dialog). Specified Conditions Options • Fluid Densities • Wave form • Hog and sag • Grounding • Damage • Compartment definition (in case of damage)

The output for the specified condition consists of a curve of cross sectional areas and hydrostatics of the vessel in the specified condition. For more detailed information please see Specified Conditions on page 71.

Page 11

Chapter 2 Quick Start

KN Values Quickstart KN values or Cross Curves of Stability are useful for assessing the stability of a vessel if its VCG is unknown. They may be calculated for a number of displacements before the height of the centre of gravity is known. The KN data may then be used to obtain the GZ curve for any centre of gravity height (KG) using the following formula: GZ = KN - KG * sin(Heel) ,where GZ is the righting lever measured transversely between the Centre of Buoyancy and the Centre of Gravity, and KG is the distance from the baseline to the vessel's effective Vertical Centre of Gravity. KN Values Analysis Requirements • Range of displacements to be analysed • Range of heel angles to be analysed • Trim (fixed or free) • Estimate of VCG

KN Values Analysis Options • Fluid Densities • Wave form • Hog and sag • Damage • Compartment definition (in case of damage)

Output is in the form of a table of KN values and a graph of Cross Curves of Stability. If an estimate of the VCG is known, this may be specified; this results in more accurate calculations of GZ from the KN data. For more detailed information please see KN Values Analysis on page 73.

Page 12

Chapter 2 Quick Start

Limiting KG Analysis Quickstart The Limiting KG analysis may be used to obtain the highest vertical position of the centre of gravity (maximum KG) for which selected stability criteria are just passed. This may be done for a range of vessel displacements. At each of the specified displacements, Hydromax runs several large angle stability analyses at different KGs. The selected stability criteria are evaluated; the centre of gravity is increased until one of the criteria fails. Limiting KG Analysis Requirements • Range of displacements to be analysed • Range of heel angles to be analysed • Trim (fixed or free) • Stability criteria for which limiting KG is to be found

Limiting KG Analysis Options • Fluid Densities • Wave form • Hog and sag • Damage • Compartment definition (in case of damage) • Key points (if required for criteria) • Margin line and deck edge (if required for criteria)

A graph of maximum permissible GZ plotted against vessel displacement is produced as well as tabulated results indicating which stability criteria limited the VCG. If limiting curves are required for each of the stability criteria individually, this may be done in the Batch Analysis mode. For more detailed information see Limiting KG on page 75.

Page 13

Chapter 2 Quick Start

Floodable Length Quickstart This analysis mode is used to compute the maximum compartment lengths based on user-specified equilibrium criteria. Floodable Lengths may be computed for a range of displacements; the LCG may be specified directly or calculated from a specified initial trim. In addition a range of permeabilities may be specified. The stability criteria used for the analysis are damage stability criteria calculated from the vessel’s flooded equilibrium status – for example: margin line immersion or angle of maximum trim. Floodable length criteria must always include either deck edge or margin line immersion criteria. Floodable Length Analysis Requirements • Range of displacements to be analysed • Range of permeabilities to be analysed • Trim (free to trim, either initial trim or specified LCG) • Floodable length criteria to be tested

• Margin line and deck edge (required for criteria)

Floodable Length Analysis Options • Fluid Densities • Wave form • Hog and sag

The output is in the form of tabulated Floodable Lengths for each displacement and permeability. The data is tabulated for each of the stations as defined in Maxsurf. The data is also presented graphically. For more detailed information please see Floodable Length on page 79.

Page 14

Chapter 2 Quick Start

Longitudinal Strength Quickstart Hydromax calculates the Net Load from the buoyancy and weight distribution of the model. That data is then used to calculate the bending moment and shear force on the vessel. Longitudinal Strength Analysis Requirements • Loadcase (including distributed loads if required) • Tank definition in the case of tank loads being included in the Loadcase (and/or for the definition of damage)

• Compartment definition and damage case (in case of damage)

Longitudinal Strength Analysis Options • Fluid Densities • Treatment of fluids in tanks: fluid simulation or corrected VCG • Wave form • Hog and sag • Grounding • Damage • Compartment definition (in case of damage) • Allowable shear and bending moment

The longitudinal strength graph and tables contain all information on weight and buoyancy distribution, the shear force and bending moment on the vessel. If defined, graphs of allowable shear and bending moment are superimposed on the graph. For more detailed information please see Longitudinal Strength on page 82.

Page 15

Chapter 2 Quick Start

Tank Calibrations Quickstart Tanks can be defined and calibrated for capacity, centre of gravity and free surface moment (FSM). Fluid densities and tank permeabilities can be varied arbitrarily. Tank calibrations are for the upright (zero heel) vessel, but the vessel's trim may be specified. Hydromax uses its fluid simulation mode to calculate the actual position of the fluids in the tanks, taking into account the vessel trim. Tank ullages are measured from the top of the sounding pipe to the free surface of the liquid within the tank along the sounding pipe. Tank calibration analysis requirements • Tank definitions • Trim

Tank calibration analysis options • Fluid Densities • Treatment of fluids in tanks: fluid simulation always selected • Hog and Sag • Damage: Intact case always selected

For each tank, a table of capacities, volumes etc. is calculated. These results are presented in both tabular and graphical forms. For more detailed information please see Tank Calibrations on page 85.

Page 16

Chapter 3 Using Hydromax

Chapter 3 Using Hydromax This chapter describes • Getting Started, installation and starting the program • Hydromax Model, opening and validating the Maxsurf model • Analysis Input • Analysis Types • Analysis Settings • Analysis Environment Options • Analysis Output

Page 17

Chapter 3 Using Hydromax

Getting Started This section contains everything you need to do to start using Hydromax • Installing Hydromax • Starting Hydromax

Installing Hydromax Install Hydromax by inserting the CD and running the Setup program, then follow the instructions on screen. Note: Before installing any program from the Maxsurf suite for the first time, please read the purchase letter (also referred to as installation manual). If you have a USB copy protection device, please ensure that you install the software before plugging in the device into the USB port on your computer.

Starting Hydromax After installation, Hydromax should be accessible through the Start Menu. Simply select Hydromax from the Maxsurf menu item under the Programs menu in the Start menu. Windows Registry

Certain preferences used by Hydromax are stored in the Windows registry. It is possible for this data to become corrupted, or you may simply want to revert back to the default configuration. To clear the Hydromax preferences, start the program with the Shift key depressed. You will be asked if you wish to clear the preferences, click OK. The following preferences are stored in the registry: • Colour settings of contours and background • Fonts • Window size and location • Size of resizing dialogs • Density of fluids • Permeabilities for floodable length analysis • Location of files • Units for data input and results output • Convergence tolerance (Error values)

Note: The default density for the fluid labelled "Sea Water" is stored in the windows registry. This is the fluid that the vessel will float in and all hydrostatic calculations are derived from. Check the density of seawater after resetting your preferences. We recommend saving your customized densities in a separate spreadsheet. If you change computer you will have to set up the preferences on the new computer.

Page 18

Chapter 3 Using Hydromax

Hydromax Model This section describes how to open a Maxsurf model in Hydromax and provides some important information to make sure Hydromax calculates the model as you intend it. • Preparing a Design in Maxsurf • Opening a New Design • Opening an Existing Hydromax Design File • Updating the Hydromax Model • Hydromax Sections Forming • Checking the Hydromax model

Page 19

Chapter 3 Using Hydromax

Preparing a Design in Maxsurf There are several important checks that must be carried out in Maxsurf before opening a design in Hydromax: • Zero Point • Frame of Reference • Surface Use • Plating Thickness • Outside Arrows • Trimming • Coherence of the Maxsurf surface model

Zero Point

Ensure that the zero point is correctly setup in Maxsurf. A consistent zero point and frame of reference should be used for the model throughout the Maxsurf suite of software. In Hydromax you have the option of displaying longitudinal measurements such as LCB or LCF from the model zero point or amidships. Frame of Reference

It is vital that the Frame of Reference is correctly setup in Maxsurf before attempting to analyse the model in Hydromax. The Frame of reference should not be changed in Hydromax. The frame of reference defines the fore and aft perpendiculars, the baseline and the datum waterline; midships is automatically defined midway between the perpendiculars. By convention, in the profile and plan views, the vessel’s bow is on the right. The perpendiculars define the longitudinal positions of the vessel’s draft marks and cannot be coincident. The base line is the datum from which the drafts are measured. Surface Use

In Maxsurf you can choose between two types of surface use • Hull – these surfaces are used to define the watertight envelope of the hull. • Internal structure – these are used for all other surfaces (any surfaces which do not make up the watertight envelope) and also surfaces which will later be used in Hydromax to define the boundaries of tasks and compartments that have complex shapes.

The following table describes the difference between each surface use in Hydromax: Included: Hull Shell Internal Structure Hydrostatic sections Selection of tank/compartment boundaries Skin thickness applied to the surface

Page 20

Chapter 3 Using Hydromax

Verify that all surfaces that are to be used as tank/compartment boundaries are defined as Internal Structure. If a surface is defined as internal structure, it is not included as part of the hull shell by Hydromax, i.e. internal surfaces will be ignored in the forming of hydrostatic sections. Note Tank boundaries made from internal structures surfaces do not have plate thickness. To model plate thickness for tank boundaries; model the surface as the inside of the compartment. Alternatively, a duplicate of the internal surface has to be made using either the offset in the duplicate surfaces dialog, the move numerical or the resize function in Maxsurf. To move/edit offset surfaces use grouped control points. Plating Thickness

If plate thickness is to be used in hydrostatic calculations, ensure that the thickness and projection direction have been specified for the hull shell surfaces. Thickness can be specified differently for each hull surface, resulting in more accurate hydrostatics. Outside Arrows

The surfaces’ outside arrows define the orientation of the surfaces. Ensure that you have used the Outside Arrows command to tell Maxsurf which direction points outwards for each surface. The surface direction may be defined using the Outside Arrows command from the Display menu in Maxsurf. The surface direction may then be toggled by clicking on the end of the arrow. Trimming

Ensure that all surfaces are trimmed correctly. You should have completely closed transverse sections or sections with at most one opening.

Correct Section with no opening.

Correct section with one opening: this section will be closed across the top.

Page 21

Chapter 3 Using Hydromax

Also see: Hydromax Sections Forming on page 25 Checking the Hydromax model on page 28 Coherence of the Maxsurf surface model

Hydromax will generally have no problem correctly interpreting your design as long as the following requirements for the Maxsurf model are observed: • Make sure that each surface touches its adjacent surfaces at its edge, preferably by bonding the edges together

• Where surfaces intersect, trim away the excess regions of the surface; e.g. the part of the keel that is inside the hull and the part of the hull that is inside the keel

• Do not have surfaces that cannot be closed in an unambiguous fashion, i.e. a maximum of one gap in a surface

• Remember that the inner portions of each intersecting contour will be trimmed off • Check surface use; internal structure surfaces are ignored when forming the hull sections in Hydromax

Note: For internal structure surfaces that will be used to define tank (or compartment boundaries) the same requirements apply. Also see: Checking the Hydromax model on page 28.

Opening a New Design File opening in Hydromax is window specific, i.e. Hydromax will automatically look for compartment definition files when you are in a compartment definition window and a loadcase in a loadcase window. To open a design for analysis, ensure that the design view window is active, then select Open Design from the File menu. Choose a Maxsurf design file (.msd) from the standard Open dialog: The following dialog will appear:

Page 22

Chapter 3 Using Hydromax Calculate Sections

Choosing Calculate Stations will calculate the specified number of sections through the hull. These will then be used for the Hydrostatics calculations. Include Plating Thickness

At this stage, any surface thickness specified in the Maxsurf Surface Properties dialog may be included. Use Trimmed Surfaces

If the Maxsurf model has trimmed surfaces, the Use Trimmed Surfaces item should be ticked. Stations

When calculating stations, you may select how many stations should be used. Reducing the number of stations will speed up the analysis time but reduce the accuracy, conversely increasing the number of stations will increase the analysis time but lead to higher accuracy results. The first option allows you to use the station grid created in Maxsurf. This first option is extremely useful for hulls that have features such as keels or bow thrusters that need to be accurately calculated and may need a locally denser station spacing to do so. It also allows designs with significant discontinuities in their volumes to have stations specified either side of the discontinuity, avoiding any errors inherent in the integration of evenly spaced stations. For example, if it was known that a design had a significant discontinuity in its sectional area curve at amidships, by specifying one station 1mm aft of amidships and one station 1mm forward of amidships this discontinuity can be modelled very accurately. The upper limit for the number of stations is 200. Surface Precision

The Surface Precision options has two functions: • Setting for calculating the hydrostatic sections • Setting used to form new compartments or tanks.

The precision used to save the file in is included in the Maxsurf design file (.msd). Hydromax recognises the precision setting the Maxsurf design file (.msd) was saved in and will and set the Surface Precision button accordingly. Note: Maxsurf surface trimming information may vary for different precisions. Therefore it is recommended not to change the precision setting when opening the Maxsurf design file in Hydromax.

Opening an Existing Hydromax Design File After saving the Maxsurf design file for the first time in Hydromax, a “Hydromax Design file” (.hmd) is created. The Hydromax design file will consist of the hydrostatic lines and all input data such as compartment definitions, key points, sounding pipes etc. Hydromax also allows saving of all input and output files into individual files. To open an existing design, there are two options:

Page 23

Chapter 3 Using Hydromax

• Double click on the .hmd file from any Windows explorer window • Use the Hydromax Open command form the file menu and select the .msd file

An existing Hydromax design consists of a number of files with different file extensions.

When Hydromax opens a .msd file, it will look for a .hmd file with the same name as the .msd file. For example: when opening OSV.msd, the OSV.hmd file is found. The calculate sections dialog now offers the option to read the sections from the file.

• Click OK.

Hydromax will now open the .hmd file. This contains hydrostatic sections information and all input information from last time the .hmd file was saved, i.e. compartment definitions, loadcases, damage cases, key points etc. Note: When selecting “read sections from file” the Maxsurf surface information is not recalculated. This means that changes to the hull shape in the Maxsurf Design file, are not automatically incorporated. See: Updating the Hydromax Model on page 25 for more information.

Page 24

Chapter 3 Using Hydromax

For more information on file properties and extensions in Hydromax, please see: File Extension Reference Table on page 237.

Updating the Hydromax Model To update the hydrostatic sections to the latest Maxsurf Design File, select “Recalculate Hull sections” in the analysis menu after reloading the Maxsurf Design File. This function can also be used to include/exclude surface thickness or change the number of sections and to change use/not use trimmed surfaces without reloading the Maxsurf Design File. The “Recalculate Hull Sections” command recalculates Hull surfaces as well as Tank Boundary surfaces (Internal Structure surfaces in Maxsurf). Any tanks and loadcases will also be updated with this command. Note: Changes to the Maxsurf design are only recalculated after the new Maxsurf design has been re-loaded into Hydromax. This means that if the model is simultaneously being edited in Maxsurf and Hydromax, it is necessary to: 1) save and close the model in Hydromax 2) save in Maxsurf 3) open in Hydromax, using “Read Sections from File” to make sure the loadcase, compartment definition etc remain part of the Hydromax design file. 3) use the “Recalculate Hull Sections” from the analysis menu.

Hydromax Sections Forming Hydromax works by applying trapezoidal integration to data calculated from a series of cross sections taken through the Maxsurf model surfaces. Hydromax will automatically form these sections, called “Hydromax sections”, “hydrostatic sections” or just “sections”. Hydromax deals only with sections that are completely closed, or can be unambiguously closed. This section outlines the section forming process in Hydromax and may be helpful whilst preparing a Maxsurf design for Hydromax. The following cases can occur: • Single surface • Multiple surface, closed section lines; e.g. via bonded edges, compacted control points, trimming etc

• Multiple surface, small gaps within tolerance • Multiple surface, one opening per surface • Multiple surface, multiple openings per surface Single Surface

Where a hull consists of an open shell (e.g. a hull surface with no deck), Hydromax will automatically close the section with a straight line connecting the opening ends.

Page 25

Chapter 3 Using Hydromax

If, however, the section is made up of two line segments, (e.g. having both a gap at the centreline as well as an open deck), an ambiguity exists as to how the two line segments will be connected. This is not an acceptable shape.

In the example above, if either the top or bottom gap had been closed in Maxsurf the design would cease to be ambiguous. Multiple Surfaces, One Closed Section

Multiple surfaces that are trimmed correctly, bonded together or use compacted control points will not cause any problems when opening in Hydromax. Hydromax will form a closed section through multiple surfaces by linking the curve segments together.

Page 26

Chapter 3 Using Hydromax

Note: Over compacted control points A common problem with compacted control points occurs when the number of compacted control points is equal to or exceeds (≥) the surface order (read: stiffness). The maximum number of compacted control points is the surface order –1. Multiple Surfaces, Small Gaps Within Tolerance

Hydromax will link curve segments together if are only separated by a small amount. The user cannot change these tolerances, because there are too many dependencies in the program. Multiple Surfaces, One Opening Per Surface

Each surface will be closed by a straight line linking the opening ends. Where surfaces intersect, each surface will be closed before being intersected with another. The excess portions of the curve will be trimmed off to form a single continuous contour.

Hydromax first closes the individual surfaces

Hydromax closes the outside contour and trims remnants

Page 27

Chapter 3 Using Hydromax Multiple Surfaces, Multiple Openings Per Surface

Same as for a single surface, Hydromax deals only with sections that are completely closed, or can be unambiguously closed. Ambiguous Sections (e.g. decks, bulwarks)

A common example of ambiguous sections is a model with multiple decks. Hydromax will have difficulties distinguishing the intended main deck.

The example above has bulwarks; generally these will be treated correctly by Hydromax and trimmed off, depending on the height of the bulwark relative to the rest of the section. To prevent ambiguities it is recommended to trim the bulwark in Maxsurf. If the bulwark’s volume is expected to influence the hydrostatic calculations, the bulwark’s volume has to be properly modelled in Maxsurf.

Checking the Hydromax model Before starting any analysis you should check whether Hydromax has been able to correctly interpret your design. The following checklist tools are available to validate the Hydromax model. • Show Single Hull Section • Show Sections Only • Checking the Sectional Area Curve • Using Rendering to Check the Model

Note: Sections that are not formed correctly cause 75% of all problems with Hydromax models. Therefore, checking your sections after opening the design in Hydromax is strongly recommended. These sections should be continuous with no gaps and no unexpected lines. In particular, look closely at intersections between surfaces to make sure that Hydromax has interpreted the shape correctly.

Page 28

Chapter 3 Using Hydromax Show Single Hull Section

In the body plan view, you can step through the sections one-by-one to verify that they have been correctly calculated. This is done by selecting Show Single Hull Section in Body Plan view from the Display menu. You can then click in the inset box to view the sections, the left and right arrow cursor keys will enable you to step through the sections one-by-one. This works the same as the Maxsurf body plan window and is an extremely powerful tool to validate your Hydromax model. For more information see the Maxsurf manual.

Show Sections Only

Checking the sections is made easy by just displaying the section contours; use the Display | Visibility dialog: (In Tank Calibration Analysis, tanks are always displayed.)

Page 29

Chapter 3 Using Hydromax

View the model in the perspective and other views. Rotating the model in the perspective view should enable you to determine whether the sections have been formed correctly:

Checking the Sectional Area Curve

Another way of checking the Hydromax model is to perform an equilibrium analysis and look carefully at the sectional area curve in the graph window. If this displays any unexpected spikes or hollows Hydromax may not have correctly interpreted the hull shape.

This Cross Sectional Area curve indicates there may be a problem with section forming from 12 m to 16 m.

Using Rendering to Check the Model

The model may also be rendered, which makes it easier to see if there are any areas of the model which have not been properly defined. Select Render from the Display menu whilst in the perspective view and turn on the sections:

Page 30

Chapter 3 Using Hydromax

Note: In rare instances incorrect rendering may occur. This does not necessarily mean that the model is incorrect. As long as the sections are formed correctly, the model is correct.

Page 31

Chapter 3 Using Hydromax

Analysis Input After checking the Hydromax model, the next step is to check the Hydromax settings and initial analysis conditions. • Setting Initial Conditions

Depending on the analysis performed, you may need to set up the following additional model data: • Loadcase • Modelling Compartments • Forming Compartments • Compartment Types • Damage Case Definition • Sounding Pipes • Key Points (e.g. Down Flooding Points) • Margin Line Points • Modulus Points and Allowable Shears and Moments • Stability Criteria

Setting Initial Conditions All Hydromax calculations are performed in the frame of reference of the model. Hydromax uses the APP and FPP together with the baseline and the zero point for all calculations and gives the results in the units specified in the display menu. Note: Before you run any analysis using Hydromax, it is important that you set up the required initial conditions for the design. Coordinate System

Hydromax uses the Maxsurf coordinate system:

Page 32

+ve forward +ve starboard +ve up

-ve aft -ve port -ve down

View window Body plan Plan Profile

View direction From the stern, looking fwd From above, Port side above the centreline From Starboard, bow to the right.

Chapter 3 Using Hydromax Frame of Reference and Zero Point

It is essential that a frame of reference be specified. Draft and trim are based on the forward and aft perpendiculars. If these are not in the correct positions, some analysis results will be meaningless. See: Zero Point and Frame of Reference on page 20 in the “Preparing a Design in Maxsurf” section. Note: Changing the zero point in Maxsurf will not update the compartment definition, loadcase and other input values. Changing the zero point after you have started analysing the model in Hydromax is not recommended. Coefficients

In Hydromax you may choose between the length between perpendiculars and the waterline length for the calculation of Block, Prismatic and Waterplane Area Coefficients. Select Coefficients from the Display menu:

Units

The units used may be specified using the Units command. In addition to the length and weight (mass) units, units for force and speed (used in wind heeling and heeling due to high-speed turn etc. criteria) and the angular units to be used for areas under GZ curves, may also be set. The angular units for measuring heel and trim angles are always degrees. Note that units can be changed at any stage during Hydromax analysis.

Other Initial Conditions

See: Page 33

Chapter 3 Using Hydromax

Fluids Simulation Method on page 97 Density on page 98

Loadcase Loadcases define the loading condition of the vessel. Static weights that make up the vessel lightship cargo, etc. are specified here as well as tank filling levels, expressed as either a percentage of the full tank capacity or as a weight. Creating a Loadcase

To create a load case, select Loadcase from the Load Case sub-menu in the Window menu. Then select New Load Case from the File menu or press Ctrl+N. A new load spreadsheet will be displayed in the Loadcase window. The default loadcase will contain a lightship entry and an entry for each tank (with a default filling of 50%).

The tabs in the bottom of the window can be used to skip though the different loadcases for the design. Naming a Loadcase

A loadcase can be given any name by saving it to a separate file. The loadcase filename will be used as the loadcase name and displayed on the tab in the loadcase window. Setting the Maximum Number of Loadcases

The maximum number of loadcases (up to twenty-five) that can be loaded in Hydromax at any one time is set by selecting Max. Number of Loadcases, from the Case menu. You may then enter the maximum number of load cases you require.

You must restart Hydromax for this change to take effect. In most cases, you will only need to set this once to the maximum number of loadcases you are ever likely to use. For convenience of use a sensible number is recommended. Each loadcase can be selected and used for analysis. Each may be saved and loaded independently, effectively allowing you as many loadcases as you require.

Page 34

Chapter 3 Using Hydromax

Note: When loading a design that has more loadcases than the maximum you have currently set in Hydromax, you will receive a warning and the file will not be loaded. You must increase the maximum number of allowable loadcases and restart Hydromax before you can load the design. Adding and Deleting Loads

To add an extra load to the spreadsheet, choose Add Load from the Edit menu or press CTRL+A. A new load will be inserted into the table. You can repeat this process for the vertical and transverse levers, and for as many loads as you wish to include. If you want to remove a load from the table, simply click anywhere in the row you want to remove, and choose Delete Load from the Edit menu. If you wish to delete several loads simultaneously, click and drag so that all of the loading rows that you wish to delete are selected, then select Delete Load. Editing Loads

Click on the cell containing the load name and type in a name for this load, for example "Lightship", and press the Tab key to go to the next column in the table (or simply click directly in the cell you wish to edit). For each item in the list, you can specify a quantity, so if the item was cargo with a weight per unit, you could use the quantity and mass columns to automatically calculate a total. The mass of each item should be entered in the next column. The mass must always be positive; if for some reason you wish to have an upward (negative) load, you can do so by entering a negative quantity – this can be useful if you want to apply a pure moment to the model by applying equal magnitude, but opposite sign loads to the vessel in the loadcase. Tab to the next column and enter the horizontal lever for this particular load item. After you type in this number, press enter and the LCG will be automatically re-calculated and displayed in the bottom row of the table. Note: Levers, as with all other measurements in Hydromax, are measured from the Zero Point. Loadcase Formatting

Hydromax allows you to improve the presentation of the Load Case window by adding blank, heading or sub-total lines in the table. Adding Component or Heading Lines Components or headings can be included in a load case by preceding the text with a period (.) character. Adding Blank Lines A blank line can be added into the load case by placing a period (.) character in the Item Name field. Adding Total Lines A subtotal can be displayed for several loads within a load case. To do this the item name field must commence with the word ‘total’.

Page 35

Chapter 3 Using Hydromax

Grouping Similar Tanks Tanks are listed in the loadcase in the order they are defined in the Compartment Definition window. If you wish to change the order in which tanks appear in the loadcase, it is necessary to reorder them in the Compartment Definition window. See: Compartment and Tank Ordering on page 46. Longitudinally Distributed Loads

Distributed loads can be entered in the Loadcase window in the aft limit and forward limit cells. The aft limit and forward limit columns only appear when Longitudinal Strength analysis is selected and the distributed loads will only have an effect on the results in this analysis mode. The “Long. Arm” column defines the longitudinal position of the centre of the load; the fore and aft limits define the longitudinal extents of the load.

If the longitudinal arm is changed in the Loadcase window, the forward and aft limits will be moved by the same amount. For an evenly distributed load, the centre of gravity should be midway between the forward and aft limits.

Evenly distributed loads. Red = green and divided in the centre.

For trapezium shaped distributed loads the centre of gravity is not midway between the boundaries, but within the middle third 1/3 of the centre.

Page 36

Chapter 3 Using Hydromax

Centre must lie within the middle 1/3 of the fore and aft limits

Trapezium shaped distributed load. Red = Green divided within middle 1/3 of centre.

Note: Since the load is distributed as a trapezium, the centre of gravity should lie within the middle third between the forward and aft limits of the load, at these extrema, the load distribution becomes triangular. Tanks will be automatically treated as distributed loads for the longitudinal strength calculations. Tank Loads

When you create tanks using the compartment definition, they will be automatically included in the loadcases. Tanks have a quantity value, expressed as a percentage of the full capacity and a weight column. Tank weights can be given as either a percentage or a weight. When either is changed, question marks will be displayed in the other and in the lever columns. This is because the calculation of each tank level is relatively slow, so it is only performed when you wish the values to be updated. To update the loadcase for changes in tank loads, select Update Loadcase from the Analysis menu or toolbar. Irrespective of whether you have updated the values in the Loadcase Condition, the Loadcase will be automatically updated as the first step of any analysis using the Loadcase information. Also see: Update Loadcase on page 214 Free surface correction

If the corrected VCG fluid option has been chosen, the Loadcase will sum the free surface moments, divide by the total displacement to obtain the VCG correction and adjust the VCG accordingly to obtain the corrected fluid VCG.

Page 37

Chapter 3 Using Hydromax

Fluid simulation If the Fluid simulation option is selected in the analysis menu, no correction is made to the upright VCG. Instead, at every step of the analysis, Hydromax calculates the actual position of the fluid in the tank taking into account heel and trim, making the tank free-surface parallel to the sea surface, thus the actual vessel CG is recalculated accounting exactly for the static shift of the fluids in slack tanks. When the corrected VCG method is selected in the analysis menu, it is possible to choose the type of free surface moment to be applied for each tank in a Hydromax Load Case. The options available are Maximum Hydromax will calculate the maximum free surface moment of the tank in upright condition for all fluid levels. Actual Hydromax calculates the free surface moment for the current fluid level of the tank in upright condition. IMO Hydromax uses IMO MSC75.(69) Ch 3.3 for the calculation of the free surface moment. This method approximates the movement of fluid due to heeling and is based on the fluid shift in a 50% full square, box-shaped-tank. For other shapes and fillings of tanks it will not correctly approximate the free surface moment. User specified A user specified value is used for all levels and heel angles. Note: All VCG correction methods, except the user specified method, set the free surface moment to zero for fillings < 2% and > 98%. This is allowed by classification societies and is an approximation of reality since the tank is almost empty or full and the shift in fluid mass is negligible.

Modelling Compartments This section will describe in detail how to model different types of tanks and compartments. Besides a general explanation on how to model tanks using the compartment definition table, this section contains a number of important sections that the user should be aware off when modelling tanks: Number of Sections in Tanks on page 49 Permeability on page 44 Linked Negative Compartments on page 51 Adding and Deleting Compartments

To start adding compartments, select the Compartment Definition table by clicking on the Compartment Definition tab at the bottom of the Input window. Select New Compartment Definition from the File menu; this will give you a new set of compartment definitions with one default tank.

Page 38

Chapter 3 Using Hydromax

Compartments may be added or deleted by selecting Add or Delete Compartment from the Edit menu. Add will add a tank after the currently selected compartment and Delete will delete the currently selected compartment(s). The accelerator keys Ctrl+A and the Delete key may also be used to add and delete entries respectively. Modelling Box Shape Tanks

Simple tanks and compartments are created by specifying six values that define a boxshaped boundary for the tank. This box will be called the Boundary Box . The boundary box is made up from the fore and aft extremities of the tank, the top and bottom, and the port and starboard limits of the tank. Each value defines one of the six planes of the tank. The column headings in the Compartment Definition window include terms such as 'F Bottom, 'A Top', 'F Port' and 'A Starboard'. The 'F' and 'A' abbreviations stand for Forward and Aft, in other words the two ends of the compartment. You will notice that aft columns contain the word "ditto". This means that the value is identical at the aft end of the tank to the forward end, resulting in a parallel tank.

Formed compartment

Box shaped compartments can be formed from the numerical values in the compartment definition table.

See Longitudinal Extents of Boundary Box on page 49 for some recommendations regarding setting the boundary box. Modelling Tapered Tanks

The default is for compartments to have parallel sides. If you wish to define tapered compartments, it is possible to enter different transverse and vertical values for the points defining the compartment ends. If a different value is entered in one of the “ditto” columns, a tapered tank will result. Tanks can be tapered or sloping in Plan or Profile views, but Hydromax does not have a mechanism for sloping the tank boundary in the Body Plan view.

Page 39

Chapter 3 Using Hydromax

Formed compartment

By changing the “ditto”-input fields, tapered tanks can be formed

Note: Tapering can be done in Plan and in Profile view. Tapered tanks in Body Plan view have to be created using a boundary surface. See Modelling Tanks Using Boundary Surfaces on page 40. Linked Tanks

Tanks, compartments and non-buoyant volumes may be linked. This means that although they are defined as separate tanks, they act as a single tank with a common free surface. To link tanks, compartments or non-buoyant volumes, first make them the same type as the parent and give them the same name. The easiest way to do this is to copy and paste the name from the Name column of the parent row into the Name column of the linked tank row. They may then be linked to the parent by typing l or linked in the Type column.

Modelling Tanks Using Boundary Surfaces

Tanks, compartments and non-buoyant volumes may have their boundaries defined by surfaces as well as being constrained to particular dimensions. This allows for the modelling of arbitrarily shaped tanks. Page 40

Chapter 3 Using Hydromax

Formed compartment

Forming tanks using boundary surfaces

The surfaces to be used to define the tank boundaries are selected by clicking in the Boundary Surfaces column in the middle of the Compartments Definition table. A dialog will appear that allows you to select which surfaces form the boundary of the tank. If a tank uses boundary surfaces, the cell in the Boundary Surfaces column is coloured blue.

If you wish to use a Maxsurf surface to define a tank or compartment, tick next to the surface name in the Boundary Surface list. Note that surfaces appear twice as there will be a starboard and a port side copy of each surface. The Starboard surface is mentioned first in the list and the Port surface last. The port surface is also identified with the suffix (P) after the name.

Page 41

Chapter 3 Using Hydromax

Note: - Only internal structure surfaces appear in the boundary surfaces list. - Symmetrical surfaces are duplicated, with the port-side surface having “(P)” appended to the surface name. - Next to selecting the internal surfaces, it is also necessary to type in the extents of the boundary box. Hydromax will automatically set the “Fore” and “Aft” limits of the boundary box to just within the longitudinal limits of the Boundary Surface. This ensures that at least 12 sections are inserted in the tank. Also see: Forming Compartments on page 47 Number of Sections in Tanks on page 49 Longitudinal Extents of Boundary Box on page 49 Modelling External Tanks

External tanks may not be modelled in Hydromax. However, it is normally possible to add "Hull" surfaces in the Maxsurf model, which will enclose the external tanks. The tanks can then be modelled in Hydromax. Note that these "external" surfaces will add to the buoyant volume of the vessel.

Additional box-shaped hull surfaces used to define deck tanks

Modelling Non-Buoyant Volumes

Non-buoyant volumes are effectively permanently flooded compartments. They can normally be modelled using trimmed hull surfaces. However, there are occasions where it is more convenient to use non-buoyant volumes. The choice whether to use trimmed surfaces or non-buoyant volumes is primarily determined by the length of the nonbuoyant volume relative to the length of the vessel. Using trimmed hull surfaces When the length of the non-buoyant volume, relative to the length of the model, is large enough; the non-buoyant volume can be calculated accurately from the hull sections. If possible, trimmed surfaces should be used. The picture below is a good example of when to use trimmed surfaces.

Page 42

Chapter 3 Using Hydromax

Propeller tunnels modelled with trimming surfaces

Using tank type: Non-buoyant volume In some cases using trimmed surfaces is just not possible. For example, when the sections of the non-buoyant volume are entirely enclosed within the hull sections (as is the case for a water jet duct) the use of a non-buoyant volume is the only way in which this can be modelled.

Water-jet ducts modelled as non-buoyant volumes

Another occasion when non-buoyant volumes should be used, is when the length of the compartment relative to the length of the hull is too small to calculate its volume from the hull sections. A good example of this is a bow thruster on a long ship. If the vessel is very long, and the thruster duct is of small diameter, there may not be sufficient sections to model it accurately (even if you use the maximum of 200 sections for the Hydromax model). In this case you are better off modelling the thruster duct as internal structure and using these surfaces to define a non-buoyant volume. For example: in the image below the bow thruster volume is only calculated with one section.

Page 43

Chapter 3 Using Hydromax

For more information, see Number of Sections in Tanks on page 49. Important: Non-Buoyant Volumes and Damage cases When the non-buoyant volume is within a compartment, a linked negative compartment has to be defined in the same position as the non-buoyant volume and then linked to the compartment and specified as a negative volume. Hence when the compartment is flooded due to damage, the negative volume that forms the non-buoyant volume is not included. (Otherwise it would be included twice, once as the non-buoyant volume and again in the compartment enclosing the non-buoyant volume.) See Linked Negative Compartments on page 51. Tip: Besides increasing the number of sections through the bow thruster from 1 to 12, modelling the thruster duct as a non-buoyant volume has the additional advantage of being able to specify a Permeability, and hence also account for the thruster.

Bow thruster tube modelled as two non-buoyant volumes

Permeability

Tanks may have two permeabilities; one, which is used when the tank is intact, and the other when it is damaged. Compartments and non-buoyant volumes use the same permeability for intact and damaged. Both the intact– and the damaged permeabilities are listed and may be edited in either permeability columns.

Page 44

Chapter 3 Using Hydromax

Permeability of Compartments As opposed to tanks, compartments typically have structure (other than plate stiffeners) and equipment inside. In case of large variations in permeability within a compartment we recommend modelling separate linked compartments with separate permeability to increase accuracy. For example an engine room with engines and auxiliaries at the tanktop could be divided up in a lower- and an upper engine room compartment. The lower compartment will have a permeability of, for example, 60% and the upper compartment a permeability of 95%. Depending on the level of accuracy required, the engines and equipment could also be modelled individually as “linked negative compartments”. Permeability of Linked Negative Compartments Since linked negative compartments are used to subtract a volume from a compartment, make sure the permeability of the negative linked tank is the same as the compartment. Also see Linked Negative Compartments on page 51. Relative Density of Tank Fluids

Relative Density (Specific Gravity) values can be typed directly into the Relative Density column of the Compartment Definition window.

Alternatively the fluid type can be entered into the Fluid Type column, either as the name or as one of the single letter codes (when entering the name, auto complete is used, so it is normally only necessary to type the first few letter of the name). If a fluid type is entered, the relative density value is obtained from the value specified in the Density dialog. Whenever values are changed in the Density dialog, all entries for that fluid in the compartment definition are automatically updated. Fuid Name Sea Water Water Ballast Fresh Water Diesel Fuel Oil Lube Oil ANS Crude Gasoline leaded Unlead. Gas. JFA MTBE Gasoil Slops Custom 1 Custom 2 Custom 3 Custom 4

Code S B W D F L C G U J M GO SL C1 C2 C3 C4 Page 45

Chapter 3 Using Hydromax

Fuid Name Custom 5

Code C5

Tanks and Surface Thickness

If you have specified that Hydromax should include the surface thickness, the tanks, compartments and non-buoyant volumes will correctly account for the surface thickness and its projection direction; the tanks will go to the inside of the hull shell. Note: Thickness of boundary surfaces are not taken into account, hence you should design these surfaces to the inside of the tank. Compartment and Tank Ordering

Tanks defined in the Compartment Definition window appear in the loadcase in the same order as they are defined in the Compartment Definition window. To reorder the tanks: • Copy the tank definition data to Excel • Sort the rows in to the desired order • Paste the data from Excel back into the Compartment Definition window.

Take care if you have linked tanks – unlink them first. Compartment and Tank Visibility

When creating complicated tank plans, it is often useful to check individual tanks. Selected tanks may be displayed in the following manner: • Define a damage case • Select only damaged tanks and compartments for display, turn off the display of intact tanks and compartments. • Select whether you want to see the tank outline or the tank sections (tanks sections are preferable when checking that tanks have been formed correctly since it is these sections which are used to determine the tank volume and other properties). • Choose the damage case from the Analysis toolbar • Set any of the tanks and compartments you wish to be visible to damaged in the damage case window.

Page 46

Chapter 3 Using Hydromax

Forming Compartments Tanks and compartments are formed automatically by Hydromax (once the tank extents and any boundary surfaces have been defined) by selecting Recalculate Tanks and Compartments from the Analysis menu. This section describes the internal tank-forming process that Hydromax uses to form tanks. First a step-by-step outline of the tank forming process is given, followed by the tank section insertion process. Understanding these processes may assist you in rare situations where the tank forming does not work as expected. Step-by-Step Tank Forming Process

As an example, the starboard waterballast tank below will be created using boundary surfaces.

An example of a port and starboard waterballast tank with a pipe tunnel at the centreline. The water ballast tanks have a margin plate on the side.

Hydromax uses three input items to form the compartment • Boundary surfaces (if defined) • Boundary box • Hydromax Hull sections

Starting position The starboard tank margin plate is modelled using an Internal Structure surface from Maxsurf.

Margin plate modelled with Internal structure surface Boundary Box

Starting point: Hydromax Hull sections with an internal surface and a bounding box

Also see: Modelling Tanks Using Boundary Surfaces on page 40 The Maxsurf manual on internal structure surfaces

Page 47

Chapter 3 Using Hydromax

Step 1: Close Internal Structure Surface

Straight line between open ends of boundary surface contour

Hydromax will close the Internal Structure Surface contour by drawing a straight line between the opening ends.

Hydromax uses the same algorithm (method) for forming the tank section from the boundary surfaces as for forming the hydrostatic sections through the hull. As with the hull sections, the surfaces selected to form the tank boundary must form closed section contours at all longitudinal positions through the tank. The area inside the selected surfaces will define the tank contour. Make sure that the boundary surfaces: • Form a closed section contour, or • There is no more than one opening – the opening will be closed with a straight line

Note: - Hydromax will close the section contour of selected boundary surfaces only. Often a tank is not formed as expected because only one side of the internal structure surface was selected for example the portside (p). - Another common cause of unexpected results is trimming. If you selected “use trimmed surfaces” while opening the Maxsurf model, Hydromax will use the trimmed internal structure surface. Usually the internal structure surfaces are best to be left untrimmed. Step 2: Clip to Boundary Surface Using the closed surface section contour Hydromax can now form a closed compartment section. The tank or compartment looks like this at this stage:

Page 48

Chapter 3 Using Hydromax

Step 3: Clip to Hull Hydromax will clip the compartment section to the hull.

Step 4: Clip to Boundary Box Finally the compartment section is clipped to the boundary box. The boundary box is formed from the numerical input in the Compartment definition table.

Number of Sections in Tanks

The volume of a tank or compartments is calculated by inserting sections between the longitudinal limits of the formed tank or compartment. Note that the formed tank or compartment is a combination of clipping to hull and boundary surfaces and numerical values. Hydromax will count the number of hull sections between the fore and aft limit of the formed tank or compartment and: • For > 12 hull sections, Hydromax uses the hull sections. For relatively long tanks, this ensures that damaged equilibrium analysis calculations will be able to converge.

• For < 12 hull sections, Hydromax inserts 12 tank sections. This is particularly useful for relatively short tanks and compartments such as bow thrusters.

Also see Longitudinal Extents of Boundary Box on page 49 Longitudinal Extents of Boundary Box

For tanks near the ship’s extremities it is good practise to set the “Fore” and “Aft” limits in the compartment table to just inside the hull surface (say 1mm). The following example illustrates why:

Page 49

Chapter 3 Using Hydromax • If the boundary box is set like this:

Boundary box

Hull sections inserted

The number of hull sections is dependent on the section spacing in the model.

• But if the boundary box is set just inside the forward limit of the bulbous bow:

Boundary box

At least 12 sections inserted

To recap – Near the ship’s extremities, the longitudinal extents should not be set to extreme values, they should be set to just inside the extents of the hull surfaces to ensure that at least 12 sections are used to calculate the tank volumes. For internal structure surfaces that are used as boundary surface, Hydromax will automatically set the “Fore” and “Aft” limits of the boundary box to just within the longitudinal limits of the boundary surface. This ensures that at least 12 sections are inserted in the tank. Note that transversely and vertically there are no such restrictions. Also see Number of Sections in Tanks on page 49 Forming Compartments on page 47

Compartment Types Six compartment types can be created using the Compartment Definition window tanks, linked tanks, compartments, linked compartments, linked negative compartments and non-buoyant volumes.

Page 50

Chapter 3 Using Hydromax

Tanks Will be included in the tank calibration output and are automatically added to the loadcase. Linked Tanks Will have their volume added to the parent tank with the same tank name. They do not have a separate entry in the loadcase. In addition, if a tank is damaged, any tank that it is linked to will also be regarded as damaged. Tanks need not be adjoining to be linked, they can be remote from one another, in this case the tank linking simulates tanks with cross connections. Compartments Are only used to specify compartmentation for damage. They are not included in the tank calibration output and will not be added to the loadcase. Linked Compartments Work in the same way as linked tanks. This allows you to damage a complex compartment configuration by linking compartments together and damaging the parent compartment. Linked Negative Compartments Allow you to subtract a volume from a compartment and are useful if tanks are defined within a compartment – see below for further details. Non-Buoyant Volumes Are only used to specify compartments of the vessel which are permanently flooded up to the static waterline. They are ideal for defining water-jet ducts, moon pools, etc. and essentially behave as damaged compartments. They are not included in the tank calibration output and will not be added to the loadcase. To change the type of a tank, type the first character of the tank type (t, c or n) in the Type column of the Compartment Definition window and then press Enter. This will automatically set the tank/compartment to the correct type. Linked Negative Compartments

Important: Read this section carefully before evaluating damage cases on models that have tanks or non-buoyant volumes within compartments. In the next section a compartment that has tanks inside it will be called the parent compartment. Tanks inside a parent compartment may be a tank, a linked tank or a nonbuoyant volume. If a tank is placed inside a compartment, its volume should be subtracted from the compartment. If this is not done, flooding the compartment in a damage case will flood the entire volume of the compartment, including the volume that is actually taken up by the tank. The next sections explain how to subtract the tank volume inside a parent compartment from the parent compartment volume. There are two ways to do this:

Page 51

Chapter 3 Using Hydromax

1: Parent compartment is modelled around the tank. Define six linked compartments, which surround the tank. A spreadsheet which automatically calculates the bounding boxes of the compartments is installed when you install Maxsurf. If you selected C:\Program Files\Maxsurf as your installation directory, the spreadsheet is installed here: C:\Program Files\Maxsurf\Utilities\Hydromax\ and the spreadsheet is called: “Tank Within Compartment.xls” The spreadsheet enables you to enter the extents of the parent compartment and the tank within that compartment. The extents of six linked compartments that tessellate around the tank are calculated and these can be copied from the spreadsheet and pasted into the Hydromax Compartment Definition window (ensure that you have sufficient blank rows in the Compartment Definition table). 2: Tank volume is subtracted using a negative linked compartment A compartment is defined in the same position as the tank or non-buoyant volume and is then linked to the compartment as a negative volume. The volume (and free surface) of the negative linked compartment is deducted from the compartment’s volume. Hence when the compartment is flooded due to damage, the negative volume that is a copy of the tanks geometry is not included. Note: The permeability for the negatively linked compartment should be the same as that of the parent compartment. This is to ensure that the volume that is subtracted from the parent compartment is exactly the same as the volume that the tank occupies within the parent compartment. See Permeability on page 44 and note that splitting up the engine room vertically has consequences for the negative linked compartments as well, as they too should be split up vertically in order to be able to take the different permeabilities into account. This second method is the preferred method, and is the only practical way of dealing with tanks defined by boundary surfaces that lie within compartments – see example below.

This tank is completely within the midship compartment

For tanks that lie wholly within a single compartment, follow the procedure outlined below: • Define the tanks and compartments, using boundary surfaces if required.

Page 52

Chapter 3 Using Hydromax

• Add extra compartments, which will become negative compartment volumes linked to the main compartment. One negative linked compartment is required for each of the tanks that are inside the compartment.

Make sure the linked negative compartment name is the same as the main compartment. Copy and paste the tank boundary input from the tank that is wholly within the compartment. Select the same boundary surfaces as well. • Link the negative volume compartments to the main compartment by selecting “Linked Neg. Compart.” from the combo-box in the Type column of the compartments.

The compartment and its negative volumes are now linked, so that when the parent compartment is damaged, the negative linked compartment (and the tank inside it) remains intact. For tanks that lie only partially within a single compartment, follow the same procedure as that outlined above, however, the negative linked volumes should be bounded by the limiting compartment boundaries, rather than including the whole tank.

Page 53

Chapter 3 Using Hydromax

Note: - Once linked, the negative linked compartment will be placed under the parent compartment. Ensure that the compartments to be linked have identical names. - If any changes are made to the tanks, corresponding changes must be made to the negative volumes. - Hydromax assumes all compartments to be defined before the damage cases are specified. If you add subsequent linked compartments or linked negative compartments to an already damaged compartment, you will have to toggle the damage setting for the parent compartment to ensure that all the linked compartments are damaged too. - See Permeability on page 44

Damage Case Definition In all but the floodable length and tank calibration analysis modes, Hydromax is capable of including the effects of user-defined damage. Hydromax allows the user to set up a number of damage cases. Volumes that are permanently flooded should be defined as non-buoyant volumes. Add Damage Case

To add a damage case, make the Damage window active and select Add Damage Case from the Case menu. You may specify a name for the Damage Case in the dialog. Each new damage case will have a column in the Damage Window and a tick may be placed to indicate which tanks and compartments are damaged for that particular Damage Case. The new damage case is added after the currently selected damage case column, to insert a damage case immediately after the intact case, select the intact case column. Several damage cases may be added in one go by selecting a number of columns.

Page 54

Chapter 3 Using Hydromax Delete Damage Case

To delete damage cases, simply select the columns to be deleted in the Damage Window and select Delete Damage Case from the Case menu. Note that it is not possible to delete the intact case. Rename Damage Case

The name of the current damage case may be changed by selecting Edit Damage Case when the damage case window is active, the current damage case is selected from the Analysis toolbar – see below. Selecting a Damage Case

The current damage case is selected from the Analysis toolbar.

The Loadcase and View windows will reflect the damage defined in the current damage case. To perform analyses for the intact vessel, select Intact as the current damage case. Any subsequent analyses will take into account the damaged compartments. Note that carrying out a Tank Calibration analysis will force the Intact case to be selected. This is also the case for the Floodable Length analysis which effectively sets up its own longitudinal extent of damage. When tanks have been damaged, their weights and levers are no longer displayed in the Loadcase window and the word ‘Damage’ is displayed in the quantity column. This is because Hydromax uses the “Lost buoyancy” method rather than “Added mass”. Note: - Hydromax uses the “Lost buoyancy” method rather than “Added mass”. - Flooding is considered to be instantaneous up to sea level. Any tank fluids are treated as having been completely replaced by seawater up to the equilibrium waterline. Display of Damage Cases

Damaged tanks are shown in the Loadcase Window in the following manner, with the label 'Damaged' in the Quantity column, and all values set to zero.

Page 55

Chapter 3 Using Hydromax

The Loadcase Window displays damaged tanks and excludes them from any calculations.

Damaged tanks and compartments are displayed for each damage case.

Sounding Pipes Hydromax allows sounding pipes to be defined for each tank. One sounding pipe per tank is permitted and up to nine vertices per sounding pipe, allowing inclined, bent or curved sounding pipes to be modelled. Page 56

Chapter 3 Using Hydromax

Hydromax creates a default sounding pipe when the tank is formed (either by running an analysis, or using one of the following commands: Analysis | Recalculate Tanks and Compartments; or Analysis | Update Loadcase. The default sounding pipe is placed at the longitudinal and transverse position of the lowest point of the tank. If the lowest point of the tank is shared between several locations (e.g. the bottom of the tank is flat either longitudinally or transversely) the default sounding pipe location is placed at the aft-most low point and as close to the centreline as possible. The top of the sounding pipe is taken to be level with the highest point of the tank and the default sounding pipe is assumed to be straight and vertical. Automatically created sounding pipes will be recalculated if the tank geometry changes. However, once the sounding pipe has been edited manually, any changes to the sounding pipe due to tank geometry changes will also have to be made manually. Edit Sounding Pipes

To customise a sounding pipe, you need to use the Sounding Pipes table in the Input window, shown below.

You can activate this window by selecting from the Windows | Input | Sounding Pipes menu, by clicking on the tabs at the bottom of the Input window, or by clicking on the icon in the window toolbar. To add vertices to create a bent sounding pipe, click on the first row of a particular sounding pipe and choose Edit | Add, or use the Ctrl+A key combination. A new row will be added to the sounding pipe and the longitudinal position, offset and height of the vertex can be edited. Unwanted vertices can be deleted by clicking on the relevant row in the table and selecting Edit | Delete, or by hitting the Delete key. Note that each successive vertex in a sounding pipe must be no higher than the previous vertex i.e. it is not acceptable to have S-bends in the sounding pipes. Calibration Increment

Hydromax allows definable increments for tank soundings. This is done by specifying an increment for each tank in the second column of the Sounding Pipes Input window. If no increment is entered, Hydromax uses its default value based on a reasonable division of the depth of the tank. In this case the sounding pipes window will display “Auto” in the Calibration Increment column for the tank. Note Increments are measured along the sounding pipe, not along the vertical axis of the tank. If the sounding pipe is inclined or if it has multiple angles, soundings will step evenly along the inclined length of the sounding pipe.

Page 57

Chapter 3 Using Hydromax

Key Points (e.g. Down Flooding Points) Key points such as deck edges and hatch openings can be defined in Hydromax using the Key Points window. The points may be displayed on the Design View window and will be displayed in different colours depending on whether or not they are immersed. Immersed key points will be displayed in the same colour as flooded tanks or compartments. Key points may be placed asymmetrically, a positive offset is to starboard and a negative offset is to port. Vessels which have symmetrical key points on starboard and port sides must have both key points added to the table. There are several types of Key Points: • Down Flooding points • Potential Down flooding points • Embarkation points • Immersion Points

Only downflooding points are used in determining the downflooding angle, which is used in criteria evaluation. The other types of points have their freeboard measured but are not used during criteria evaluation and are for information only. Adding Key Points

The Key Points table works in a similar manner to the Compartment Definition table. To start adding downflooding points, select New Downflooding Points from the File menu. You will be given a default point. To add additional downflooding points to the table, choose Add Point from the Edit menu. A new point will be inserted after the currently selected row in the table. Deleting Key Points

To delete a Key point, click anywhere in the row of the point to be deleted and select Delete. To delete more than one point at a time, click and drag over the rows you want deleted.

Select Delete from the Edit menu, and the selected rows will be deleted. Editing Key Points

Key points are defined by entering a name, a longitudinal position, a transverse offset from the centreline, and a height. Click in any cell and enter the name or value you require. All points are entered relative to the current zero point. The type of Key Point may be selected from the combo-box in the Type column of the Down Flooding Points table in the Input window:

Page 58

Chapter 3 Using Hydromax

Links to Tanks or Compartments

Downflooding points may be linked to tanks or compartments. Select the tank or compartment from the combo-box in the Linked to column of the Down Flooding Points table in the Input window:

Downflooding points that are linked to tanks or compartments, which are damaged in the currently selected damage case, will be ignored when computing the downflooding angle. These downflooding points will appear italicised prefixed and an asterisk* postfixed to the downflooding point’s name in the DF Angles table of the Results window:

The downflooding angles for each of the points are displayed in the results window. The downflooding angles are computed during a large angle stability analysis; the freeboards after an Equilibrium analysis. Note: Linking a downflooding point to a tank does not mean that Hydromax will consider a tank damaged when the downflooding point is submerged. This form of automatic flooding is not supported in Hydromax yet.

Page 59

Chapter 3 Using Hydromax

Margin Line Points The margin line is used in a number of the criteria. Hydromax automatically calculates the position of the margin line 76mm below the deck edge when the hull is first read in. If necessary, the points on the margin line may be edited manually in the Margin Line Points window (the deck edge is automatically updated so that it is kept 76mm above the margin line). It is only necessary to modify the height value of the margin line points. Once this has been done for all the points that need to be changed, selecting Snap Margin Line to Hull in the Analysis menu will project all of the points horizontally onto the hull surface, ensuring that the margin line follows the hull shape precisely. Points may be added or deleted as required using the procedure described in Adding Key Points and Deleting Key Points on page 58.

Modulus Points and Allowable Shears and Moments The Modulus window can be used to enter maximum allowable shears and moments. It will also be used in future for entering section modulus to display bending stress. One or more points can be entered in this window. Allowable shear and/or moment can be specified at each point.

To start a table of allowable shear forces and bending moments, bring the Modulus table to the front and choose New Modulus Points from the File menu with the Modulus window frontmost. The allowable values can be saved and recalled as text files by using Open and Save from the File menu. New allowable values can be inserted by selecting Add from the Edit menu and entering a longitudinal position as well as an allowable shear and/or moment. Allowable values are displayed as lines on the longitudinal strength graph. Points may be added or deleted as required using the procedure described for the key points.

Stability Criteria Stability criteria may be evaluated after a large angle stability analysis and after an equilibrium analysis. Stability criteria are required to perform a limiting KG analysis. Please refer to Chapter 4 Stability Criteria starting at page 111 for information on defining and selecting criteria.

Page 60

Chapter 3 Using Hydromax

Analysis Types After specifying the input values and checking the Hydromax model, the analysis can be performed. In this section the different analysis types available in Hydromax will be described. The following analysis types are available in Hydromax: • • • • • • • • •

Upright Hydrostatics Large Angle Stability Equilibrium Analysis Specified Conditions KN Values Analysis Limiting KG Floodable Length Longitudinal Strength Tank Calibrations

Also, some general information is given on: • Starting and Stopping Analyses • Batch Analysis

The required analysis settings and environment options will be discussed separately and more detailed in the next two sections of this chapter.

Page 61

Chapter 3 Using Hydromax

Upright Hydrostatics Upright hydrostatics lets you determine the hydrostatic parameters of the hull at a range of drafts. Choosing Upright Hydrostatics

Select Upright Hydrostatics from the Analysis Type option in the Analysis menu or toolbar. Upright Hydrostatic Analysis Settings

The following analysis settings apply for Upright Hydrostatic Analysis: • Trim from the Analysis menu, you may specify a fixed trim for all drafts • Draft from the Analysis menu, specify range of drafts for analysis

A range of drafts for upright hydrostatic calculations can be specified using the Drafts command from the Analysis menu.

Initial and final drafts can be entered, together with the number of drafts to be used. The Vertical Centre of Gravity is also required for the calculation of GM etc. When a design is first opened, the initial draft defaults to the draft at the DWL in Maxsurf. Similarly the VCG defaults to the height of the DWL. Upright Hydrostatics Environment Options

The following environments can be applied to the upright hydrostatics analysis: • Density from the Analysis menu • Wave Form (if any) • Hog and Sag • Damage (or Intact) from the Analysis toolbar

Page 62

Chapter 3 Using Hydromax Upright Hydrostatic Results

Page 63

Chapter 3 Using Hydromax

Large Angle Stability Large angle stability lets you determine the hydrostatic parameters of the hull at a range of heel angles either with or without trim. Choosing Large Angle Stability

Select Large Angle Stability from the Analysis menu or toolbar. Large Angle Stability Settings

The following analysis settings apply for Large Angle Stability Analysis: • Displacement and Centre of Gravity using the Loadcase window • Heel from the Analysis menu, select range for analysis • Trim (fixed or free) from the Analysis menu

If criteria are being evaluated, the heel range and heel angle steps should be chosen accordingly, to ensure accurate evaluation of the criteria. Note You can select positive heel direction (port or starboard). However, you can enter negative values and test full 360 degrees of stability if you wish -some criteria require calculations of GZ at negative heel. The criteria are only evaluated on the side of the graph that corresponds to positive heel angles. For example: when using a -180 to 180 heel range, the results may be two angles of vanishing stability, the one that would be reported in the criteria would be the one with a positive heel angle (even if the one at negative heel occurred at an angle closer to zero). Also see: Heel on page 90 in the Analysis Settings section. Large Angle Stability Environment Options

The following environments can be applied to the large angle stability analysis: • Fluid simulation of tank fluids centre of gravity • Density • Wave Form (if any) • Hog and sag (if any) • Damage (or Intact) from the Analysis toolbar • Stability Criteria

Large Angle Stability Results

Large Angle Stability Analysis results are: • Hydrostatic data table for each angle of heel • GZ curve • Stability Criteria evaluation • Downflooding angles to key points

Page 64

Chapter 3 Using Hydromax

Stability Criteria Evaluation The criteria evaluation is displayed in the criteria tab in the results window. For more information on how to customize the criteria evaluation, please refer to the Results Window on page 198 in the reference section. Important: For important information on varying displacement while evaluating criteria, see: Heeling arm criteria dependent on displacement on page 151.

Page 65

Chapter 3 Using Hydromax

Downflooding Angle After a Large Angle Stability analysis, the Key Points Data table lists the downflooding angles of the margin line, deck edge and defined downflooding points. In addition, the first downflooding point is marked on the large angle stability graph. Only the positive downflooding angles are displayed, hence if there is any asymmetry, the large angle stability analysis should be carried out heeling both to starboard and to port. The immersion angles and freeboard to the margin line and deck edge are also included, as well as the longitudinal position at which this occurred.

Downflooding points that are linked to tanks or compartments that are damaged in the currently selected damage case, will be ignored when computing the downflooding angle. These downflooding points will appear italicised, prefixed and an asterisk postfixed to the downflooding point’s name in the Key Point Data table of the Results window. A downflooding angle of zero degrees indicates that the key point is immersed at zero degrees of heel.

Page 66

Chapter 3 Using Hydromax

Equilibrium Analysis Equilibrium analysis lets you determine the draft, heel and trim of the hull as a result of the loads applied in the table in the Load window. The analysis can be carried out in flat water or in a waveform. Choosing Equilibrium Analysis

Select Equilibrium from the Analysis Type option in the Analysis menu. Equilibrium Analysis Settings • Displacement and Centre of Gravity using the Loadcase window

Also see: Frame of Reference on page 20 Equilibrium Analysis Environment Options

The following environments can be applied to the Equilibrium analysis: • Fluid simulation of tank fluid centre of gravity • Density • Wave Form (if any) • Hog and Sag (if any) • Damage (or Intact) from the Analysis toolbar • Grounding (if any) • Criteria

Equilibrium Results

Equilibrium Results are the • Hydrostatic data • Freeboard of key points • Criteria evaluation • Time stepping animation

Page 67

Chapter 3 Using Hydromax

Hydrostatic data

Height/freeboard above free surface The freeboard of each Key Point is also calculated. The freeboard is for the vessel condition currently displayed in the Design view and is recalculated after each Equilibrium and Specified Conditions analysis. The freeboard calculated is the vertical distance of the Key Point above the local free surface, hence the local free surface height if a waveform is selected will be taken into account.

Freeboard of key points.

Negative freeboards, i.e. where the Key Points are immersed are displayed in red. The longitudinal positions at which the minimum freeboard for the margin line and deck edge occurred are also specified.

Page 68

Chapter 3 Using Hydromax

Stability Criteria Evaluation The criteria evaluation is displayed in the criteria tab in the results window. For more information on how to customize the criteria evaluation, please refer to the Results Window on page 198 in the reference section. Equilibrium Animation in Waves If performed in conjunction with analysis in waves, the Equilibrium analysis will automatically phase-step the waveform through a complete wavelength. This gives ten columns of results, one for each movement of the wave crest. If necessary the results of this phase stepping can be animated giving a simple simulation of the hull motion in waves. Note: This simulation only includes static behaviour at each wave phase, and does not cover dynamic or inertial forces. This can be done using Seakeeper. Equilibrium Concept

The definition of equilibrium is “Position or state where object will remain if undisturbed”. You can distinguish equilibrium into two types: • Stable, when disturbed the object will return to its equilibrium position • Unstable, when disturbed the object will not return to its equilibrium position

Stable equilibrium

Unstable equilibrium

With ships an unstable equilibrium can exist when the KG > KM, i.e. the centre of gravity is above the metacentre. In real world a ship at unstable equilibrium will roll from the upright unstable equilibrium to a stable equilibrium and assume an “angle of loll”. Since Hydromax starts the equilibrium analysis in upright position, it has no way of determining whether the equilibrium is stable or unstable. This means that unstable equilibrium may be found instead of the stable equilibrium. Therefore it is recommend to check the GZ curve yourself after doing an equilibrium analysis.

Page 69

Chapter 3 Using Hydromax

Unstable equilibrium

Stable equilibrium ”Angle of loll”

The graph above shows the results of a Large Angle Stability analysis for a vessel with negative initial GM. In practice this vessel would have a loll angle of approximately 25 degrees. If an equilibrium analysis is performed for this vessel with the transverse arm set to zero, Hydromax will find the unstable equilibrium position with zero heel. In practice, it is desirable to find the stable equilibrium position. To do this, first ensure that the error values (Edit | Error value) are set as sensitive as possible. This will ensure that the smallest possible heeling moment is required to find stable equilibrium position.

Then create a very small heeling moment by offsetting one of the weight items in the loadcase window TCG by just a fraction. The results of the equilibrium analysis find the stable equilibrium position. Note: It is good practice to always perform a Large Angle Stability analysis as well as the equilibrium analysis to check if the vessel is in stable or unstable equilibrium. This is most likely to occur if the VCG is too high and the vessel has negative GM when upright. The problem can be overcome by offsetting the weight of the vessel transversely by a small amount.

Page 70

Chapter 3 Using Hydromax

Specified Conditions Specified Condition analysis lets you determine the hydrostatic parameters and equilibrium response of the hull as a result of changing the heel, trim and immersion. Heel can be varied be specifying either the angle of heel or the TCG and VCG. Trim can be varied by changing either the amount of trim, or the LCG and VCG. Immersion can be varied by specifying either the displacement or the draft. Choosing Specified Conditions

Select Specified Conditions from the Analysis Type option in the Analysis menu or toolbar. Specified Conditions Settings

The settings required for Specified Condition analysis are: • Specified Conditions from the Analysis menu

Three Sets of variables are provided, labelled Heel, Trim and Immersion. One choice must be made from each of these groups. Hydromax will then solve for the vessel hydrostatics at the conditions specified.

Values from the current loading condition can be inserted into the Centre of Gravity and Displacement fields by clicking on the Get Loadcase Values button. Also see: Frame of Reference on page 20 Specified Conditions on page 93 in the Analysis Settings section. Note: If the fluid simulation has been turned on in a previous analysis mode, then the VCG obtained from the loadcase will not include the free surface correction; the “Get Loadcase Values” button will return exactly the displacement and CG as displayed in the current loadcase window. Specified Conditions Environment Options

The following environments can be applied to the Specified Condition analysis: • Density • Wave Form (if any)

Page 71

Chapter 3 Using Hydromax • Hog and Sag (if any) • Damage (or Intact) from the Analysis toolbar

Specified Conditions Results

The specified conditions results are the same as equilibrium analysis results, i.e. hydrostatic data and key points freeboard.

Page 72

Chapter 3 Using Hydromax

KN Values Analysis KN Values Analysis allows you to determine the hydrostatic properties of the hull at a range of heel angles and displacements to produce the cross curves of stability diagram. Choosing KN Values Analysis

Select KN Values from the Analysis Type option in the Analysis menu or toolbar. KN Values Analysis Settings

The analysis settings required for KN Values analysis are: • Heel from the Analysis menu, select range for analysis • Trim (fixed or free) from the Analysis menu • Displacement from the Analysis menu, select range for analysis and specify estimate of VCG if known

The heel angles used may differ from those used in the Large Angle Stability analysis. To set the range of angles, select Heel from the Analysis menu. A range of displacements for KN calculations can be specified using the Displacement command from the Analysis menu. Initial and final displacements can be entered, together with the number of displacements required.

The VCG can also be entered. Traditionally, KN calculations are calculated assuming the VCG at the baseline (K). However if an estimate of the VCG is known, the accuracy of the KN calculations (for VCGs in the vicinity of the estimated VCG) may be improved by calculating the GZ curve using the estimated VCG position -- this will reduce the error in the trim balance due to the vertical separation of CG and CB because this vertical separation is specified more accurately than simply assuming the VCG at the baseline. If a VCG estimate is specified, the KN values are still presented in the normal manner with the KN values calculated as follows: KN(φ) = GZ(φ) + KG_estimated sin(φ) See KN Value Concepts on page 74 for more information. For information on Trim settings for KN Analysis, see: Trim for KN, Limiting KG and Floodable Length analyses on page 91.

Page 73

Chapter 3 Using Hydromax KN Values Analysis Environment Options • Density • Wave Form (if any) • Hog and Sag (if any) • Damage (or Intact) from the Analysis toolbar

KN Values Analysis Results

KN Value Concepts

The righting lever, GZ, may be calculated from the KN cross curves of stability (at the desired displacement) for any specified KG using the following equation:

Page 74

Chapter 3 Using Hydromax

• GZ = KN - KG * sin(φ)

M

Z G

B’ B

N

K KG*Sin(φ

GZ = KN - KG*Sin(φ) Note: KN values can also be referred to as “Cross curves of stability”.

Limiting KG Limiting KG analysis allows you to analyse the hull at a range of heel angles and displacements to determine the highest value of KG that satisfies the selected criteria. GZ curves are calculated for various KG values. After each cycle, the selected criteria are evaluated to determine whether the CG may be raised or must be lowered. When comparing the results of a limiting KG analysis to that of a Large Angle Stability analysis, it is essential that the same heel angle intervals are used and that the free-totrim options and CG are the same. Some criteria, notably angle of maximum GZ, are extremely sensitive to the heel angle intervals that have been chosen. Choosing Limiting KG

Select Limiting KG from the Analysis Type option in the Analysis menu or toolbar. Limiting KG Settings

The initial conditions required for Limiting KG analysis are: • Displacement from the Analysis menu, select range for analysis • Heel from the Analysis menu, select range for analysis • Trim (fixed or free) from the Analysis menu

The range of displacements to be used is set in the same way as they are set in the KN analysis. The heel angles used may differ from those used in the Large Angle Stability analysis. To set the range of angles, select Heel from the Analysis menu. See Large Angle Stability on page 64 for further details. For information on Trim settings for Limiting KG Analysis, see: Trim for KN, Limiting KG and Floodable Length analyses on page 91.

Page 75

Chapter 3 Using Hydromax

Note: - Since Limiting KG can be quite a time consuming analysis, you may wish to use a smaller number of heel angles than for the Large Angle Stability calculations. (However this will cause some loss of accuracy.) - Limiting KG calculations will be significantly faster if the trim is fixed. Limiting KG Environment Options • Fluid simulation of tank fluid centre of gravity • Density • Wave Form (if any) • Hog and Sag (if any) • Damage (or Intact) from the Analysis toolbar • Criteria

Limiting KG Results

Limiting KG analysis results are • Limiting KG values, including their displacement and criteria. • Limiting KG vs displacement graph

The Limiting KG analysis also checks for equilibrium based criteria. However, you must still have at least one Large Angle Stability criterion selected. Criteria are only evaluated on the positive side of the GZ curve, so if there is any form of asymmetry, it may be necessary to run the analysis heeling the vessel to both starboard and port (this can be done automatically in the Batch Analysis).

Page 76

Chapter 3 Using Hydromax

After a Limiting KG analysis has completed, the results in the Criteria results table display “Not Analysed”, this is because they do not necessarily refer to the final KG and would be misleading if all the selected criteria would have actually been evaluated during the Limiting KG analysis. If you require the limiting KG for each criterion individually or wish to perform a Large Angle Stability and Equilibrium analysis at each of the displacements and the corresponding limiting KG’s, this can be done in the Batch Analysis. Some criteria may depend on the vessel displacement and or vessel’s VCG. Where these values are explicit in the criterion’s definition in Hydromax, the correct values of displacement and VCG will be used in the evaluation of these criteria. However, problems can arise if the criterion is only available in its generic form – most commonly heeling arm criteria where the heeling arm is specified simply as a lever and not as a moment. In this case, since the heeling arm is not related to the vessel displacement in its definition within Hydromax, the heeling arm will remain constant for all displacements (where it is perhaps desired that the heeling arm should vary with displacement – for example in the case where the heeling moment, rather than the heeling arm is constant). Important: For important information on varying displacement while evaluating criteria, see: Heeling arm criteria dependent on displacement on page 151. Also see: Convergence Error on page 95 in the Analysis Settings section.

Page 77

Chapter 3 Using Hydromax Limiting KG Concepts

Hydromax will iterate to a KG value that just passes all criteria you have specified in the criteria dialog. Hydromax will start with a set start KG value (e.g. 1 meter), run a large angle stability analysis and check the selected criteria. If any of the criteria fail, HM, will lower the KG and try again. If the criteria pass, Hydromax will raise the KG value and try to make the criteria fail. Hydromax will continue doing this until the limiting KG value has been iterated within 0.1mm. If this tolerance is not achieved in a certain number of iterations, Hydromax will move on to the next displacement. When performing a Limiting KG analysis, Hydromax will evaluate any equilibriumbased criteria that are selected for testing and act accordingly. However, at least one GZbased criterion must also be selected. This is because to perform a sensible search, Hydromax must have at least one criterion that will improve by reducing the VCG; Hydromax assumes that raising the VCG will make criteria more likely to fail and that reducing the VCG will make the criteria more likely to pass. This is not necessarily the case for equilibrium-based criteria such as freeboard requirements or for GZ-based criteria such as Angle of maximum GZ; if only these types of criteria are selected, Hydromax may have difficulty in finding a true limiting KG and specify convergence errors.

Page 78

Chapter 3 Using Hydromax

Floodable Length The Floodable Length analysis allows you to calculate the longitudinal distribution of maximum length of compartments that can be flooded with the vessel still passing specified stability criteria. The results are presented as the maximum length of compartment plotted (or tabulated) against the longitudinal position of the compartment’s centre. Traditionally the criterion of margin line immersion is used to compute the Floodable Length curve. The Floodable Length may be computed for a range of displacements and compartment permeabilities. Choosing Floodable Length

Select Floodable Length from the Analysis Type option in the Analysis menu or toolbar. Floodable Length Analysis Settings

The initial conditions required for Floodable Length analysis are: • Trim (free to trim, either initial trim or specified LCG) • Displacement, select range and specify VCG • Permeability, select range

The analysis is always carried out free-to-trim, but the centre of gravity can either be specified directly in the Trim dialog or it is computed from the specified initial trim. For information on Trim settings for Floodable Length Analysis, see: Trim for KN, Limiting KG and Floodable Length analyses on page 91. The range of displacements to be used is set in the same way as they are set in the KN and Limiting KG analyses. The VCG must also be specified since the Floodable length analysis is very sensitive to accurate trim calculations. This means that the vertical separation of CG and CB is accounted for in the trim balance. The permeability dialog is used to specify the permeabilities to be used for the Floodable Length analysis; the permeability is applied over the entire length of the vessel and is also applied to the free-surface.

This permeability is unrelated to the permeability when defining compartments and is only used for floodable length calculations. Floodable Length Environment Options • Density • Wave Form (if any) • Hog and Sag (if any)

Page 79

Chapter 3 Using Hydromax • Damage: no damage case may be selected as this is automatically defined by the analysis. The Intact condition is automatically selected and the Damage toolbar is disabled

• Criteria from the Analysis menu, select which criteria should be evaluated, these must be Equilibrium criteria checked for damaged condition

Criteria must be specified from the analysis menu. These are used to compute the Floodable Lengths.

Note that internally, Hydromax will treat the vessel sinking or the trim exceeding +/-89º as a criterion failure. Floodable Length results

The results of the analysis are given in tabulated format at the stations defined in the Maxsurf grid spacing as well as graphical format. The tabulated data is linearly interpolated from the graphical data. (The raw graph data can be accessed by double clicking the graph.)

Page 80

Chapter 3 Using Hydromax

If the analysis is unable to find a condition where the vessel passes the selected criteria, the following dialog will be displayed. The vessel sinking or the criteria failing in the intact condition could cause this.

Floodable Length Concepts

The analysis is performed by defining a flooded compartment, with the centre of the compartment at a section under investigation. The length of this flooded compartment is increased section-by-section until one of the criteria is failed. The compartment is then moved progressively forward along the vessel. This process may be visualised by turning on the display of the Hydromax sections.

Note: Speed versus Accuracy The analysis will be both considerably more accurate and slower with a larger number of sections in the Hydromax model; it is recommended that a minimum of 100 sections be used for most situations. The speed of the analysis can be increased quite considerably by increasing the allowable error values in the Edit | Error values dialog.

Page 81

Chapter 3 Using Hydromax

Longitudinal Strength Longitudinal Strength lets you determine the bending moments and shear forces created in the hull due to the loads applied in the Loadcase window. The analysis can be carried out in flat water or in a specified waveform. Choosing Longitudinal Strength

Select Longitudinal Strength from the Analysis Type option in the Analysis menu or toolbar. Longitudinal Strength Settings

The initial conditions required for Longitudinal Strength analysis are: • Displacement and Centre of Gravity using the Loadcase window • Distributed loads using the Loadcase window

When the Longitudinal Strength analysis mode is selected, two extra columns appear in the Loadcase window. These are used to specify the longitudinal extents of the load. A trapezium shaped distributed load is derived from the centre and fore and aft extents of the load. See the Loadcase: “Distributed loads” section in the Analysis Input section in this chapter for more details. Longitudinal Strength Environment Options • Fluid simulation of tank fluid centre of gravity • Density • Wave Form (if any) • Hog and Sag • Damage (or Intact) from the Analysis toolbar • Grounding (if any) • Criteria, allowable shears and moments from Input window

Longitudinal Strength Results

The output from the longitudinal strength calculations is a graph of weight, buoyancy, net load, shear force and bending moment along the length of the hull. Allowable forces and moments can be overlayed on the graph.

Page 82

Chapter 3 Using Hydromax

Name of Curve Weight Buoyancy

Net Load Shear

Description Vessel mass / unit length Buoyancy distribution / unit length = immersed cross sectional area * density. Damaged tanks and compartments reduce the buoyancy. “Weight” – “Buoyancy” x

Shear Force =

∫ NetLoad ( x)dx

AftSt

Moment

x

Bending Moment = −

∫ ShearForce( x)dx

AftSt

Allowable shear and moment

Allowable shear and bending moments as specified in the input “modulus” table.

This data is also displayed in the “Long. Strength” tab in the Results window. You can display this table by choosing Longitudinal Strength from the Results sub-menu under the Window menu.

Page 83

Chapter 3 Using Hydromax

Note: For the purposes of strength calculations, any point loads in the loadcase will be applied as a load evenly distributed 100mm either side of the position of the load.

Page 84

Chapter 3 Using Hydromax

Tank Calibrations Tank Calibration allows you to determine the properties of the tanks you have defined in the Compartment window, at a range of capacities. Choosing Tank Calibrations

Select Tank Calibrations from the Analysis Type option in the Analysis menu or toolbar. Tank Calibration Input • Tank definitions and boundaries • Permeability • Fluid type

All required Tank Calibration Analysis input can be specified in the Compartment Definition window. Note: Note that permeability and relative density values can be changed after the tanks have been calibrated, the capacities and free surface moments will be updated automatically. Also see: Relative Density of Tank Fluids on page 45 Tank Calibration Settings • Trim, fixed trim

Tank Calibration Environment Options • Hog and Sag (if any) • Density

Tank Calibration Results

Page 85

Chapter 3 Using Hydromax

In the Window | Graphs menu each tank can be selected for display in the Graph window. For more information see Chapter 5 Hydromax Reference.

Page 86

Chapter 3 Using Hydromax

Starting and Stopping Analyses To start the analysis, choose Start Analysis from the Analysis menu or toolbar. Hydromax will step through the parameter ranges specified, floating the hull to equilibrium conditions where required. At each iteration, Hydromax will redraw the contents of the windows to display the current hull position. Calculations may be interrupted at any time by hitting the Escape key. You can also choose Stop Analysis from the Analysis menu or toolbar. If you have stopped the analysis, you can resume calculation by selecting Resume Analysis from the Analysis Menu or toolbar. There may be a slight time delay on all of these operations while the current cycle is finished. You can also switch by clicking in the window of any background program. Hydromax will continue to calculate in the background although its speed will be reduced. The start, pause and resume functions are also available in the Analysis toolbar:

Page 87

Chapter 3 Using Hydromax

Batch Analysis Hydromax has basic batch processing capability. With a single command, Hydromax will run Large Angle Stability and Equilibrium analyses for all combinations of load and damage cases. Further, Limiting KG and KN calculations will be made for each damage condition. There are other options which allow the analysis to be performed heeling to both port and starboard. For the Limiting KG analysis you may also check the Limiting KG for each criterion individually. You may also choose to perform a Large Angle Stability and Equilibrium analysis at the final VCG. Batch Analysis Settings

Analysis parameters such as trim, heel angles etc. are set in the normal way for each analysis type included in the Batch analysis.

Batch Analysis Environment Options

Any criteria that have been set are evaluated at the end of each analysis and the results of these are also output to the text file. Important: For important information on varying displacement while evaluating criteria, see: Heeling arm criteria dependent on displacement on page 151. Starting Batch Analysis

Once the loadcases, damage cases, key points, criteria and analysis parameters for the Large Angle Stability and Equilibrium analyses have been set up, the Batch Analysis is started with the Start Batch Analysis command in the Analysis menu. Note: Under most operating systems, minimising Hydromax can reduce the time required to perform the calculations. This is because time consuming redrawing of the design windows, graphs and tables is avoided.

Page 88

Chapter 3 Using Hydromax Batch Analysis Results

Before analysis starts, you will be prompted to enter the name and location of the file where Hydromax will write the results of the batch analysis. Once the analysis is complete, this tab delimited text file may be imported directly into MS Excel for further processing. Because the analyses are simply carried out one after the other, it is not possible to go back to the results for a specific analysis from within Hydromax; only the results of the final analysis will be stored in Hydromax. At the bottom of the dialog is a check box which allows users to select whether they want the results of a batch analysis to go to the Report window in Hydromax as well as the batch analysis text file. Warning: Sending the results to the report can slow down analysis considerably and also consume considerable system resources. For large batch analysis, it is advisable not to include the results in the report. Batch Analysis Concepts

The aim of the batch processing function is to: • Provide the user with a simple and consistent way of carrying out Large Angle Stability and Equilibrium analyses on a large number of load and damage cases.

• Facilitate export of the data from Hydromax and import into MS Excel for post processing and report generation.

• Provide all relevant results and the data required to be able to reproduce the runs, i.e.: analysis parameters, file name etc.

Page 89

Chapter 3 Using Hydromax

Analysis Settings In the previous sections opening and preparing a model in Hydromax was discussed together with descriptions of the different Analysis types. This section will describe the following analysis settings: • Heel • Trim • Draft • Displacement • Specified Conditions • Permeability

Hydromax will allow specification of only those analysis settings that apply to the selected analysis type. In hydrostatic analysis, there are three degrees of freedom: Trim, Heel and Draft. Hydromax matches the trim, heel and draft with the vessel’s displacement and centre of gravity, or visa versa. For example: it can match a specified heel, trim and draft by varying the displacement and centre of gravity; or it can match a specified displacement and centre of gravity by varying the heel, trim and draft. Combinations of both are also possible. The following table lists the degrees of freedom and their weight counterpart:

1 2 3

Degree of Freedom Draft Trim Heel

Weight Displacement Longitudinal Centre of Gravity (LCG) Transverse Centre of Gravity (TCG)

The various analysis types and settings can be thought of as setting one variable in each pair to a fixed value and deriving the others from the analysis. For example: the Upright Hydrostatics analysis consists of fixing heel and trim and stepping through a series of fixed drafts. In this case the LCB and TCB (and therefore the required LCG and TCG) are calculated from the underwater hullshape at each draft. For an equilibrium analysis all degrees of freedom are derived from the LCG, TCG and Displacement. In the Specified Condition Analysis any combination of the variable pairs may be specified.

Heel The Heel dialog from the analysis menu is used to specify the range of heel angles to be used for Large Angle Stability, KN and Limiting KG analyses. Heel angles between -180° and +180° are. The heel steps must be positive. If only one set of steps is required, simply put 0 in the other steps. If there is any asymmetry in the vessel due to either: hull shape, key points, loading, damage, etc., and there is any doubt as to which will be the worst heel direction, then the analysis should be carried out for both heel to starboard and heel to port to find the most pessimistic condition. If all the heel angle intervals are 10 deg or less, Hydromax will fit a cubic spline to the GZ curve and use this to interpolate for values between the heel angles tested. If any step is greater than 10 deg, Hydromax will not do any curve fitting and linear interpolation will be used. Page 90

Chapter 3 Using Hydromax

Note: For the angle of equilibrium to be found (when analysing criteria), it is essential that the GZ curve crosses the GZ=0 axis with positive slope. It is possible that the GZ at zero heel may be very slightly positive (due to asymmetry or rounding error) for this reason, it is advisable to test at least one negative heel angle, at say -5 degrees, to ensure that the equilibrium angle is identified. It is good practise to start the heel range at an angle of approximately -30°. This is to allow roll back angle criteria to be evaluated correctly.

Note: The heel angles to be used are specified independently for each analysis mode. This can be a source of apparent differences in the results from the different analyses.

Trim For most analyses you may specify whether the vessel is free to trim or has fixed trim. Select “Trim” in the Analysis menu to bring up the Trim dialog.

Trim may be specified for Upright Hydrostatics, Large Angle Stability, KN Analysis Limiting KG, Floodable Length and Tank Calibrations. (For the Specified Condition analysis, the trim may be specified in the Specified Conditions dialog.) Equilibrium and Longitudinal Strength Analyses always use a free trimming analysis where the LCB and LCG are aligned. Trim for KN, Limiting KG and Floodable Length analyses

Fixed trim (KN and Limiting KG analyses only). Page 91

Chapter 3 Using Hydromax

The analysis is carried out with the specified fixed trim; the vessel is not free to trim as it heels. Free to trim using a specified initial trim value Using this method, for each displacement, the LCB of the intact vessel at the specified trim and zero heel is computed, the LCG is made equal to this value and is then used to compute the free to trim vessel orientation at each heel angle as the large angle stability analysis is performed. Thus, for each displacement, the upright vessel trim will be the same, but the LCG will be different. Free to trim to a specified LCG value With this method, a specified constant LCG is maintained for each displacement. This LCG is then used to compute the free to trim vessel orientation at each heel angle as the large angle stability analysis is performed. Thus, for each displacement, the LCG will be the same, but the upright vessel trim will be different. Calculation of LCG

For both KN and Limiting KG calculations, it is necessary to compute the vessel’s LCG if the analysis is free to trim. If the user specifies an LCG, then this value is used. If an initial trim is specified, the LCB of the intact vessel at each specified displacement at this trim is calculated the LCG is set equal to this value of LCB.

Draft The draft dialog is used to specify the range of drafts to be used for the Upright hydrostatics analysis.

The VCG specified in the draft dialog is used for two purposes: 1. For free-to-trim KN calculations, a more accurate result can be achieved if an estimate of the VCG is known. GZ curves derived from the KN results in the region of the estimated VCG will be more accurate than if a VCG at the base line had been assumed. This is because the effect of vertical separation of CG and CB on trim will have been accounted for more precisely. 2. For the Floodable length calculation, accurate trim calculations are essential. For this reason the VCG is required.

Displacement The displacement dialog is used to specify the range of displacements to be used for the KN, Limiting KG and Floodable Length calculations.

Page 92

Chapter 3 Using Hydromax

It is also possible to specify a VCG in the displacement dialog, this is used to improve the accuracy of the trim balance for KN and Floodable Length analyses; in the case of the Limiting KG analysis, the actual VCG is used and the VCG input field will state “not applicable”.

Specified Conditions The specified conditions analysis setting is only available for the specified condition analysis.

Permeability The Permeabilities are set in a table in the permeability dialog. Use the Add and Delete buttons to add or delete rows from the table. The permeabilities may be sorted by double clicking on the permeability column heading. The last set of permeabilities used will be recalled from the registry when Hydromax is started.

Page 93

Chapter 3 Using Hydromax

The permeability dialog is used to specify the permeabilities to be used for the Floodable Length analysis; the permeability is applied over the entire length of the vessel. This permeability is unrelated to the permeability when defining compartments and is only used for floodable length calculations. Individual Permeability of Tanks and Compartments

The individual permeability of each compartment (or tank) is specified in the Compartment definition table. The compartment, tank and non-buoyant volume permeabilities are used when calculating the effects of damage, and/or calculating the weights of fluids in tanks in the loadcase. Also see: Modelling Compartments on page 38

Page 94

Chapter 3 Using Hydromax

Error Values In the edit menu of Hydromax, calculation error values can be set. This defines the error values that Hydromax uses to determine when to finish iteration during • Large Angle Stability • Equilibrium analyses • Specified conditions • Floodable Length

Ideal Error values can range between 0.00001% and 0.1% (1 gram in 10 tonnes of displacement). Acceptable Error values can range from 0.001% to 1.0%. Acceptable Error values should always be greater than Ideal Error values. Convergence Error

Hydromax will attempt to solve most analysis to within the ideal error value. If this is not achieved within a certain number of iterations, but the acceptable error has been achieved, Hydromax will continue. If convergence to within the acceptable error has not been achieved, Hydromax will display a warning.

One of the most common causes of non-convergence is if the specified displacement exceeds the volume of the completely submerged vessel and it sinks. Also convergence may be poor if the trim angle approaches ±90°. If Hydromax thinks that it is likely that the model has sunk (waterplane area is zero at the current condition) the following dialog will be displayed. The specified displacement and the actual displacement at the current iteration are provided for information. Note This warning is not displayed during batch analysis, instead the warning is written in the batch file. If there is a convergence problem, which appears not to be due to sinking, then the following dialog will be displayed.

Page 95

Chapter 3 Using Hydromax

This problem can sometimes occur if the specified displacement is extremely small and the vessel has a large flat bottom, producing a highly non-linear waterplane area vs. draft plot. Other causes of non-convergence can be non-linear moment to trim vs. trim angle curve or moment to heel vs. heel angle curve. Note: There are occasions when convergence will not necessarily occur within the maximum allowable number of iterations. If Hydromax fails to converge it will give you a warning, but will allow you the option of continuing the search. If you choose to continue, Hydromax will search for the equilibrium position indefinitely. If the search is unsuccessful after a reasonable period of time, you can interrupt Hydromax by pausing the analysis. The analysis will also fail to converge if the trim becomes excessive. All analyses other than Floodable Length will fail if the trim exceeds +/-45º; in the case of the Floodable Length analysis, this limit is increased to +/-89º.

Page 96

Chapter 3 Using Hydromax

Analysis Environment Options The analysis can be performed in different environments; this section describes the analysis environment options available in Hydromax in more detail: • Fluids Simulation Method • Density • Waveform • Grounding • Hog and Sag • Stability Criteria

Fluids Simulation Method Hydromax allows you to specify two different ways of simulating any fluids contained in tanks or compartments. Selecting Fluids in the Analysis menu opens the Fluids Analysis dialog.

Note The criteria in Hydromax assume that the corrected VCG method is being used. Although the computational potential is available, authorities have not adopted this more accurate calculation of the shift in centre of gravity due to fluid movement. Fluid analysis method: Use corrected VCG

Tank capacities and free surface moments are calculated for the upright hull (zero trim and zero heel). The effective rise in VCG due to the tanks' free surface is calculated by summing the free surface moment of all the tanks filled to less than 98% capacity and dividing by the total vessel displacement (the free surface moment to be applied is specified in the loadcase). This method should be used when compiling a stability booklet for a design, as it corresponds with the traditional approach used by naval architects and classification societies worldwide. It is reasonably accurate at low angles of heel and trim. In this case, the loading window will include a column for free surface moment and cells for corrected fluid VCG. These values are automatically calculated from the maximum free surface moments of the tanks, calculated in the upright condition. There are several FSM types available. For more information, see the Loadcase window section in the Reference chapter of the Hydromax manual.

Page 97

Chapter 3 Using Hydromax Fluid analysis method: Simulate fluid movement

This method is a faithful simulation of the movement of the centre of gravity of the fluid in each tank. Every tank is rotated to the heel and trim angle being analysed. Hydromax iterates to find the fluid level for the rotated tank at the specified capacity. The new centre of gravity is calculated for each tank and used in the analysis. The new LCG, VCG and TCG are calculated for the whole design and used in the calculation of GZ, KG, and GM. This approach is used when the stability of a vessel is being investigated and the closest possible simulation of the hull's behaviour is required. It is particularly useful at high angles of heel or trim, or with tanks whose heeled water plane area may be significantly different from the upright case (i.e. tall narrow tanks, or wide shallow tanks). The penalty of using this approach is that the calculation time is longer, however the results are significantly more accurate.

When fluid simulation method is selected, free surface moments and corrected fluid VCG are not applicable and are not displayed in the loadcase.

The fluid simulation is used for analyses that use a load case, i.e. Large Angle Stability, Equilibrium Condition and Longitudinal Strength. When fluid simulation is used in one of these analyses, the actual fluid level in the tank, filled to the volume specified in the loadcase, will be displayed in the View Window. Otherwise the complete tank will be shown.

Density Where necessary, the density of sea water (the fluid in which the vessel is floating) and fluids commonly carried on board can be adjusted using the Density dialog. Density using the current units, or non-dimensional relative density (specific gravity), may be specified. Alternatively, density may be specified using Barrels as the unit of volume. Conversions are performed automatically. Relative density is calculated relative to a fluid having a density of 1000.0 kg/m3.

Page 98

Chapter 3 Using Hydromax

By assigning a code to the fluid you can easily apply the fluid type in the compartment definitions dialog. Tanks that have been specified as containing one of these fluids will be updated automatically when the density of the fluid is changed in the fluid dialog. Tank calibrations results and loading conditions will also be updated. Note The vessel's hydrostatics are always calculated assuming the vessel is floating in the fluid labelled "Sea Water". This is the first fluid in the list printed in bold font. If the vessel is to float in a different fluid, it is necessary to change the density of this fluid. Note that only the custom fluids may have their names changed. Thus, if you wanted to carry out an analysis for a vessel in fresh water, you would change the density of "Sea Water" to 1000.0 kg/m3. Also see: Windows Registry on page 18

Waveform Hydromax is capable of analysing hydrostatics and stability in arbitrary waveforms as well as for a level water plane. To specify a waveform, select the Waveform command from the Analysis menu:

Page 99

Chapter 3 Using Hydromax

The water plane can be specified as flat, or as a sinusoidal or trochoidal waveform. If a waveform is specified, the wavelength, wave height and phase offset can be specified. The wavelength defaults to the waterline length of the hull at the DWL. If the wavelength is modified the wave height defaults to a standard metric wave, equivalent to: Once a wavelength has been set, the wave height can be modified to give a non-standard height. The phase offset governs the position of the wave crest aft of the forward end of the DWL, as a proportion of the wavelength. The phase offset varies between 0 and 1, both of which correspond to a wave crest at the forward end of the DWL. For example, a phase offset of 0.5, with a wavelength equal to the waterline length, will give a single wave crest at amidships.

Grounding Grounding is an additional analysis environment option for the Equilibrium or Longitudinal Strength analyses. It is possible to specify grounding on one or two points of variable length. The Equilibrium analysis will determine whether the hull is grounded or free floating and will trim the hull accordingly. Damage can be specified concurrently with grounding.

Page 100

Chapter 3 Using Hydromax

Note: Grounding points are considered to span the transverse extents of the hull and therefore constrain the heel to zero. The length of the grounding points is only used when considering the load distribution for Longitudinal Strength analysis and not to determine the pivot point. The vessel is considered to pivot at the centre of the grounding point.

Hog and Sag Hydromax has the option to apply hog or sag during the calculations.

Hog or sag is distributed in a parabolic curve centred at either the amidships location, or a specified longitudinal position relative to the zero point. This is called the “centre of deflection”. When hog is specified the centre of deflection and frame of reference at that location remain stationary and the ends of the hull are deflected downward.

Page 101

Chapter 3 Using Hydromax

When sag is specified the centre of deflection and frame of reference at that location remain stationary and the ends of the hull are deflected upwards.

Note: Hog and sag apply to all analysis modes including tank calibrations, which will vary slightly with changes in hog and sag.

Stability Criteria Stability criteria may be seen as the “environment of authorities” that the ship will be deployed in. For more information see Chapter 4 Stability Criteria starting at page 111.

Damage You can specify whether the model is to be analysed in intact or damaged condition using the analysis toolbar. Also see: • Analysis Toolbar on page 207 • Damage Case Definition on page 54

Page 102

Chapter 3 Using Hydromax

Analysis Output Hydromax will produce the following output data: • Hydromax model • Hydromax input tables • Result data tables per analysis • Graphs per analysis • Report

This section describes the various output options available in Hydromax • Data transfer • Copying data • Copying hull views • Copying graphs • Printing • Saving

A wide range of options for transferring data from Hydromax to other programs such as spreadsheets and word processors is provided. Note: This data transfer works both ways: e.g. importing and exporting Excel spreadsheets allows you to use the full spreadsheet capabilities of Excel on your Hydromax model.

Page 103

Chapter 3 Using Hydromax

Select View from Analysis Data Each step from the analysis can be visualised. For example: the angle of downflooding can be visualised by returning to the Stability table in the results window, selecting the column at the required heel angle and select “Select View From Data” in the Display menu.

The hull will then be rotated to the selected position in the View window.

Perspective view of model at angle of downflooding during a large angle stability analysis.

Page 104

Chapter 3 Using Hydromax

Copying Copying Hull Views

Pictures of the hull in the View windows may be copied to the Clipboard using the Copy command from the Edit menu. A dialog appears after selecting the Copy command that will allow you to set the scale of the copied picture.

These pictures can then be pasted into other applications or the Hydromax Report window. Copying Tables

Tables may be copied to the clipboard. Simply select a cell, row, column, range of cells or the whole table and then choose the Copy command. The data copied from the table will be placed on the clipboard and can then be pasted into a spreadsheet or word processor for further work. Note: Copying data from the table with the Shift key depressed, will also copy the column headings. Copying Graphs

You can copy the contents of the Graph window using the copy command. Note that the picture that is placed in the clipboard will be the size that it was displayed on your screen. Note: When the graph is pasted in Microsoft Word®, the graph can be edited by right clicking on the graph and selecting “edit picture”. This does not work for Word version later than Office 2000. | Also see: Graph data on page 202 for information on how to get graph data exported to programs such as Excel for further processing.

Page 105

Chapter 3 Using Hydromax Printing

Each of the windows in Hydromax may be printed. Simply bring the window you wish to print to the front and choose Print from the File menu. Views of the hull in the View window may be printed to scale as in Maxsurf. Prior to printing you may wish to set up the paper size and orientation by using the Page Setup command from the File menu. Note that in the report, the inserted tables will be automatically formatted to fit the current page set up. However, once the tables have been placed into the report, their formatting will not be changed by changes to the print set up. Hence it is often most convenient to select the desired report page set up before any analyses have been made. Print Preview

The page to be printed is initially displayed in print preview mode. To print the page click the Print button, otherwise click the Cancel button. The printing may be forced to be black and white. Choose the Colours button and select the options required. Note that the print preview is not refreshed after these changes, but the selection will be reflected in the printout. The titles may be edited by clicking the Titles button.

Page 106

Chapter 3 Using Hydromax

Saving the Hydromax Design Hydromax design data may be saved • Saving in a Hydromax Design File • Saving Input Files separately

Saving in a Hydromax Design File

To save the design in one file, ensure that the View window is topmost and select Save from the File menu. The Hydromax data is saved in a .hmd file with the same name as the design. Saving Input Files separately

In addition to saving all the data together, the data in the individual tables such as loadcases, damage cases, compartment definition, key points etc., may also be saved separately. For more information on file properties and extensions in Hydromax, please see: File Extension Reference Table on page 237. Note It is recommended to save Hydromax input files separately. Saving Loadcases to a File Once you have set up a loading spreadsheet, you can save it in a file on disk. This allows the same loading spreadsheet to be recalled at any time for use with the same design or with any other hull. To save the loadcase table, ensure the Loadcase window is topmost on the screen and choose Save Load Case from the File Menu. Selecting this option saves all the loads displayed in the current tab in the Loadcase window. Saving Damage Cases to a File Bring the Damage window to the front and select Save Damage Cases or Save Damage Cases As from the file menu. Saving Compartment Definitions to a File To save a compartment definition to a file, bring the Input window to the front and choose the compartment definition table; select Save Compartment Definition from the File menu. You will be asked to name the file and select where it is to be saved. Saving Input Window Tables To save a input window table to a file, bring the Input window to the front and choose the required input table; select Save ……. from the File menu. You will be asked to name the file and select where it is to be saved. Saving Results to a File

Once you have performed an analysis, the data generated may be saved as a text file. This allows for further calculations to be done in a spreadsheet or for formatting to be done in Word, Excel or other programs. To save the data, ensure the Results window is topmost on the screen and choose the table containing the data you wish to save. Select Save or Save As from the File Menu.

Page 107

Chapter 3 Using Hydromax

Selecting this option saves all the data currently displayed in the Results window. The Results files are saved as Tab delimited text, meaning that they can be read directly into spreadsheets such as Excel with values being placed in individual spreadsheet cells.

Page 108

Chapter 3 Using Hydromax

Exporting The data export function in Hydromax is similar to Maxsurf. Some Hydromax-specific export features are described below.

Data export dialog in Hydromax.

DXF export Contains all lines displayed in the active design window as closed poly-lines. In addition, each tank, compartment and non-buoyant volume is exported on a separate layer. This export function is particularly useful to export tank arrangement drawings. Note: The layer name is the same as the compartment name, so it is important to have unique compartment names. For more information on data export of DXF and IGES, please see the “Output of Data” section in the Maxsurf manual. Exporting the Model to Hydromax Version 8.0

After Hydromax version 8, a major change I the Hydromax file structure was made. Hydromax models created in version greater then version 8.0 can be exported using the File | Export menu so that it is compatible with Hydromax version 8.0 All key points will become downflooding points in the v8 file and any tank sounding pipe information will be lost.

Page 109

Chapter 4 Stability Criteria

Chapter 4 Stability Criteria This chapter describes how stability criteria are used in Hydromax. Stability criteria are evaluated for Large Angle Stability, Equilibrium and Limiting KG calculations. The following sections will be discussed: • • • • • •

Criteria Overview Setting up Criteria - the Criteria Dialog Criteria Results Nomenclature Parent Stability Criteria Specific stability criteria

The next chapter, Chapter 5 Hydromax Reference, starting at page 193, will explain the functionality of all windows, menus and toolbars found in the Hydromax program.

Page 111

Chapter 4 Stability Criteria

Criteria Overview Hydromax uses a single dialog to control all the stability criteria. This makes it quick and easy to set which criteria should be included for analysis and to change criteria parameters. In the criteria results table, much more data relating to the intermediate calculations is available. It is also possible for users to create their own custom sets of criteria by selecting from a wide range of standard criteria types, called parent criteria. Users may save, import and edit their criteria sets. These custom criteria files may be easily transferred via email. Criteria may be identified as intact or damage criteria (or both). This ensures that the correct criteria are evaluated and displayed during normal and batch analysis. Although all criteria are displayed in the criteria table, only criteria that are applicable are added to the report; i.e.: if the intact case is being computed, only the criteria that are selected for evaluation during an intact analysis will be evaluated and added to the report, similarly for the damage cases. Criteria results are added to the Report after a Large Angle Stability or Equilibrium analysis. However, only the applicable criteria are added to the report (although all are displayed in the Results table); i.e. after an Equilibrium analysis only those criteria that are evaluated from Equilibrium data are added, and after a Large Angle Stability analysis only GZ based criteria are added to the report. Help information relating to the use and parameters of each criterion is displayed in the dialog.

Note: Floodable Length Analysis uses its own set of criteria that can be accessed through the Analysis | Criteria menu when Floodable Length is selected

Page 112

Chapter 4 Stability Criteria

Setting up Criteria - the Criteria Dialog The criteria are selected for inclusion in the analysis and have their parameters changed in the Criteria dialog. Select Criteria from the Analysis menu:

or use the Criteria button,

, in the analysis toolbar:

The criteria dialog is shown below:

Page 113

Chapter 4 Stability Criteria

Resizing and adjusting the dialog’s layout

The dialog may be resized and a vertical and horizontal slider can be used to resize the width of the Criteria List and the height of the Criterion Details areas. Note that if, in the unlikely event that the dialog items vanish due to resizing the dialog, the dialog size can be reset by holding down the “Shift” key when you open the dialog. Also in this section: • Criteria Tree List • Criteria Details • Criteria Help

Page 114

Chapter 4 Stability Criteria

Criteria Tree List The left-hand pane displays the list criteria that are available. The list allows you to manage your stability criteria.

The criteria tree list

Parent Criteria

The Parent Criteria group contains all the parent criteria types that are available in Hydromax. Each parent criterion allows you to perform a specific calculation; these are the fundamental criteria from which criteria for specific codes are derived. Parent criteria are special in that you cannot rename, delete or add criteria to the Parent Criteria group. Also the parent criteria settings cannot be saved, they will always revert to their default values when Hydromax is restarted. This is because the parent criteria are intended for use as templates from which you can derive your own custom criteria. This is done by dragging the required parent criteria in to the “My custom criteria” group or any other group you create. To distinguish the Parent criteria from your derived criteria, they are displayed in bold text in the Criteria list. You will notice that different icons are used to differentiate between different types of criteria. These icons are derived from the parent criterion type. The different types of criteria and their icons are described below: Folder icon, create separate folders to store related criteria. All folders must have unique names (even if the parent folders have different names). Equilibrium criterion. These criteria are evaluated only after an equilibrium analysis has been performed. GZ criterion. These criteria make measurements from the GZ curved obtained from a Large Angle Stability analysis. GZ area criterion GZ criterion with heeling arm

Page 115

Chapter 4 Stability Criteria

GZ area criterion with heeling arm GZ criterion with several heeling arms and their combinations GZ area criterion with several heeling arms and their combinations Combined GZ criterion. These criteria perform several individual tests on the GZ curve. e.g. STIX. Combined GZ heeling arm criterion. These criteria perform several individual tests on the GZ curve including a heeling arm. e.g. Weather criterion. Moving Criteria

Criteria may be moved from one group to another by dragging them with the left-mousebutton or by using the cut and paste functions in the right-click context menu (see above). Note that if you drag a criterion from the Parent Criteria group a copy will be made and the original will not be deleted. Defining new Custom Criteria and Groups

New custom criteria sets may be created by first creating a new criterion group and then dragging the desired criteria into the criterion group. By holding down the Ctrl button a copy of the criterion being dragged is created (unless it is a parent criterion, in which case a copy will be made regardless of whether the Ctrl key is held down or not). Alternatively use the Copy and Paste functions from the right-click context menu (see above). It is extremely important to ensure that all criteria groups have unique names. If duplicate group names exit, then loading the criteria file may cause unexpected results. As criteria (and new groups) are loaded they are inserted into the first group that is found with a name that matches the name of the group to which the criterion should belong. If there are groups with the same name, all criteria that should be in a group of that name will end up in the first one and none in the second. Using the Criteria Tree List

The tree works in much the same way as the file folders in Windows Explorer: • Click on the “+” sign to expand the folder (or double click on it). • Click on the “-” sign to collapse the group (or double click on it). • Click on an item’s name or icon to select it • Once selected, click again on the on the item’s name to edit its name

Some short-cut keys for the tree list: Tree control smart keys Alt+Keypad * Right Arrow or Alt+Keypad + Left Arrow or Alt+ Keypad Up Arrow Down Arrow Space

Page 116

Function Recursively expands the current group completely Expands the current group Collapses the current group Move one item up tree Move one item down tree Include criterion for analysis

Chapter 4 Stability Criteria Selecting the Criteria for Analysis

Criteria may be selected for analysis by ticking the tick box to the left of the criterion. Other functions are available from a menu activated when the right button is clicked on your mouse. To select an entire group, right-click on the group and choose Include for Analysis from the menu. Damage and Intact

Criteria may be defined as intact or damage stability criteria (or both). Intact criteria are only evaluated for the intact case and damage criteria are evaluated when a damage case has been selected (irrespective of whether there are actually any damaged compartments or tanks in the damage case). Criteria that are defined for both are always evaluated. These options may either be set using the right-click menu or by ticking the appropriate boxes in the bottom of the dialog:

Intact and Damage tick-boxes.

Criteria Tree Right-click Context Menu

Several options are available by right-clicking on a criterion or criterion group:

Criterion right-click menu

Include for Analysis: Toggle whether the criterion (or all criteria within the group) should be evaluated. Intact: Toggle whether the criterion (or all criteria within the group) should be evaluated for intact conditions. Damage: Toggle whether the criterion (or all criteria within the group) should be evaluated for damaged conditions. Lock: Toggle whether the criterion (or all criteria within the group) are locked. If a criterion is locked, this prevents inadvertent editing of its parameters. Locking is used for criteria belonging to specific codes where the required values are fixed. Page 117

Chapter 4 Stability Criteria

Add Group: Add a new criterion group. Cut: Cut the criterion (or whole criterion group) to the clipboard. This may then be pasted into another location in the tree. Copy: Copy the criterion (or whole criterion group) to the clipboard. This may then be pasted into another location in the tree. Paste: Paste the criterion (or whole criterion group) from the clipboard to the selected location Rename: Renames the criterion or group. This may also be done by selecting the label, then clicking again in the label. Delete: Deletes the criterion or all the criteria and sub-groups within the group.

Criteria Details The specific details for a criterion are displayed in the table in the top-right of the dialog:

Criterion details table

Page 118

Chapter 4 Stability Criteria

To edit the parameters for a specific criterion, click on the criterion’s name in the tree and the criterion’s parameters will be displayed in the table on the right. Edit the parameters as required and then select the next criterion to be edited from the tree, or click the dialog’s Close button. Please note that the criteria are updated as you change their data and that there is no “Cancel” function for this dialog. If in doubt, use the File | Save Criteria command to save a copy of your current criteria selection and data before making any changes in the Criteria dialog. The parameters that may be adjusted have a white background; those which cannot be edited, have a grey background. The values that are required for passing a criterion are in bold. Check Boxes in Criteria Properties Section of Criteria Dialog

There is some subtly different behaviour for the check boxes in the dialog depending on their context. In most cases there will be group of related options used to define a criterion parameter. For example the limits for an upper integration range or the individual criteria to be evaluated for a more complex criterion:

In both of these cases the selection is cumulative and none of the selections are mutually exclusive. However, at least one must be selected.

In other cases, where the items are mutually exclusive, the check boxes act as radio buttons and only one may be selected. This occurs, for example, with the “Value of GMt at” criterion:

Finally a check box can be used to select whether a specific effect should be included, for example, GZ curve reduction in the wind heeling criteria:

Page 119

Chapter 4 Stability Criteria Criterion Pass/Fail Test

There are some subtle differences between the wordings for different criteria. For example one criterion may state “Shall be greater than…”, whereas another may state “Shall not be less than…”. Hydromax allows you to make this distinction by selecting the required comparison from a combo-box in the criterion row of the details table:

Description Shall be greater than Shall not be less than Shall be less than Shall not be greater than

Symbol > ≥ < ≤

Logical test Greater than Greater than or equal to Less than Less than or equal to

Criteria Help A brief description of the criterion is displayed in the lower right-hand pane of the criteria dialog.

Page 120

Chapter 4 Stability Criteria

Criteria Results After a Large Angle Stability or Equilibrium analysis, criteria are evaluated and the results displayed in the Stability Criteria table in the Results window. Criteria are also reevaluated whenever the Criteria dialog is closed. After calculation the relevant criteria are also added to the Report. Criteria Results Table

The tested criteria are listed one above the other. Intermediate values are displayed. Values that could not be calculated, e.g.: angle of vanishing stability, angle of equilibrium, etc., have n/a in the Actual and/or Value column. This is normally due to an insufficient range of heel angle having been used. Results may be displayed in “Verbose” or “Compact” format (see above). The format for the results table and the report are specified separately. Chose the Display | Data Format command when the Stability Criteria results are displayed:

Page 121

Chapter 4 Stability Criteria

Stability criteria results window: verbose format

Stability criteria results window: compact format

Report and Batch Processing

As noted earlier, only the relevant criteria results are added to the Report and/or Batch file. Criteria that are not relevant, e.g. damage criteria during intact analysis or Equilibrium criteria during a Large Angle Stability analysis, are not added to the Report (although they are displayed in the Criteria Results table).

Importing and Saving Criteria Sets It is possible to load and save the criteria. The parent criteria, built into Hydromax are not saved, only the criteria that you create or import will be saved. Page 122

Chapter 4 Stability Criteria

Default Criteria Library File

When starting, Hydromax will try to open the default criteria library file called: “Hydromax Criteria Library.hcr” from the directory in which the Hydromax program resides. If this file cannot be found, you will be prompted to locate a criteria file:

You may select an alternative file or click the Cancel button to proceed and be given the default criteria, which consists of the Parent criteria and a “My Custom Criteria” group. The default criteria library or the alternative file that you selected will be automatically updated every time the criteria dialog is closed. Saving Criteria

It is also possible to save the criteria into a new file - this can be useful when you are defining new custom sets of criteria that you wish to keep separate or when defining criteria sets for different vessels. Choose Save Criteria As from the File menu. This will simply export all the custom criteria (parent criteria are not saved) to the specified file. Further updates will, however, continue to be saved to the default criteria library file that was opened when Hydromax was first started, so if you want to save any further changes you will have to resave as described above. Importing Criteria and Specific Criteria Files

New criteria may be added to your criteria list by importing them - choose Import Criteria from the File menu. You will then be asked if you wish to keep the existing criteria:

Page 123

Chapter 4 Stability Criteria

If you choose “Yes” your existing criteria will be kept, if you choose “No”, all existing criteria except the parent criteria will be removed and replaced by those in the file you are opening. The default criteria library will be over-written with the new criteria so if you wish to keep any custom criteria that you may have added to your default criteria library, it is a good idea to save them first in a new file. Note that when keeping your existing criteria, it is important to ensure that the group names in the file you are importing are not the same as those that already exist. If this does occur, the imported criteria will be found in the original groups, not in the new groups. A number of criteria containing criteria for specific codes are supplied with Hydromax. These may be found in the “HMSpecificCriteria” folder. Criteria File Format

The criteria are save in a Hydromax criteria file with the extension .hcr. The file is a normal PC text file, which may be edited manually so as to generate custom criteria. The typical format of the file is given in the Appendix. Editing this file will also allow you to add your own help text or associate rich text format help files (rtf) files with your criteria.

Page 124

Chapter 4 Stability Criteria

Nomenclature This section gives a brief description of the various values that are determined by Hydromax in the evaluation of criteria. There are two distinct types of criteria: • Criteria that depend on the final static waterline of the vessel. These are computed after an Equilibrium analysis has been performed. For example “Margin line not immersed”.

• Those that are computed after a Large Angle Stability calculation. The criteria depend on various calculations made from the GZ curve. For example “Area under the GZ curve”. These are the majority of criteria.

Note: The meta-centre is always (even for Large Angle Stability criteria) computed directly from the vessel’s hydrostatic properties (i.e. water-plane inertia and immersed volume) at the specified heel angle and not from the slope of the GZ curve. This gives an accurate result that is not dependant on the heel angles and intervals tested during the analysis.

Definitions of GZ curve features: Some typical GZ curves are shown below, the third graph shows the GZ curve with a heeling arm overlayed.

Typical GZ curve

Page 125

Chapter 4 Stability Criteria

Unusual GZ curve with double peak

GZ curve with heeling arm superimposed

Page 126

Chapter 4 Stability Criteria GZ Definitions

The table below defines how Hydromax calculates the various features of the GZ curve: Angle of vanishing stability Angle of vanishing stability with heeling arm curve Downflooding angle Equilibrium angle Equilibrium angle with heeling arm curve First peak in GZ curve

GML or GMT

GZ Curve Heeling arm curve

Maximum GZ Maximum GZ above heeling arm curve

The angle of vanishing stability is the smallest positive angle where the GZ curve crosses the GZ=0 axis with negative slope. The angle of vanishing stability with a given heeling arm is the smallest positive angle where the GZ curve crosses the heel arm curve and where the GZ-Heel Arm curve has negative slope. The downflooding angle is the smallest positive angle at which a downflooding point becomes immersed. The equilibrium angle is the angle closest to zero where the GZ curve crosses the GZ=0 axis with positive slope. The equilibrium angle with a given heeling arm is the angle closest to zero where the GZ curve crosses the heel arm curve where the GZ-Heel Arm curve has positive slope. In some cases, the GZ curve may have multiple peaks; this often occurs if the vessel has a large watertight cabin. The angle of the first peak is the lowest positive angle at which a local maximum in the GZ curve occurs. Vertical separation of the longitudinal or transverse metacentre and centre of gravity. The location of the metacentre is computed from the water-plane inertia, not the slope of the GZ curve. Note that the centre of gravity used is the upright centre of gravity corrected by the free surface moments of partially filled tanks in their upright condition, rotated to the specified heel (and trim) angle. The curve of vessel righting arm (GZ) plotted against vessel heel angle A curve of heeling lever, which is superimposed on the GZ curve. This is typically used to assess the effects of external heeling moments, which are applied to the vessel. These include the effects of wind, passenger crowding, centripetal effects of tuning, etc. Depending on the moment that they represent, the heeling arm curves will have different shapes. The heeling arms are never allowed to be negative; if the cos function goes negative, the heeling arm is made zero. If the heeling arm has a power of cos greater than zero, the heeling arm is forced to be zero at heel angles greater than 90° and less than -90°. Positive angle at which the value of GZ is a maximum Positive angle at which the value of (GZ - heel arm) is a maximum

Page 127

Chapter 4 Stability Criteria

Glossary The table below describes some commonly used terms:

φ

Angle of heel measured from upright.

Deck Slope / maximum slope

The maximum slope of an initially horizontal, flat deck at the resultant vessel heel and trim. i.e. combined effect of heel and trim. Used for some wind heeling criteria, the Gust Ratio is the ratio of the magnitude of the gust wind heeling arm to the steady wind heeling arm. 1998 CODATA recommended value for standard acceleration of gravity A negative heel angle change. Often a roll back angle is measured from some equilibrium position; the resulting heel angle after the roll back has been applied is more negative than the original. Commonly used in wind and weather criteria to account for the action of waves rolling the vessel into the wind. If a criterion uses a roll back angle, it is often necessary to calculate the GZ curve for negative angles of heel.

Gust Ratio g = 9.80665ms-2 Roll back angle

Page 128

Chapter 4 Stability Criteria

Parent Stability Criteria The parent criteria are divided up into different categories: • • • • • •

Criteria at Equilibrium GZ Curve Criteria (non-heeling arm) Heeling arm criteria Multiple heeling arm criteria Heeling arm, combined criteria Other criteria

Criteria at Equilibrium These criteria are calculated after an equilibrium analysis and relate to the equilibrium position of the vessel after the analysis. The equilibrium criteria are only displayed in the report if you run an equilibrium analysis. Maximum value of Heel, Trim or Slope at Equilibrium

This criterion may be used to check the value of maximum Heel, Pitch or Maximum Slope (compared with an originally horizontal and flat deck). Option The angle of

Shall be less than / Shall not be greater than

Description Choose from the following (case insensitive auto-completion is used): Heel Pitch MaxSlope Permissible value

Units deg

deg

Minimum Freeboard at Equilibrium

Checks whether the minimum freeboard is greater than a minimum required value. This could be used to check margin line or downflooding point immersion. Option The value of

Shall be greater than / Shall not be less than

Description Choose from the following (case insensitive auto-completion is used): Marginline DeckEdge DownfloodingPoints PotentialDfloodingPoints EmbarkationPoints ImmersionPoints Permissible value

Units length

length

Page 129

Chapter 4 Stability Criteria Maximum Freeboard at Equilibrium

Check that the maximum freeboard is less than a maximum required value. This could be used to check that an embarkation point is sufficiently close to the waterline. Option The value of

Shall be greater than / Shall not be less than

Description Choose from the following (case insensitive auto-completion is used): Marginline DeckEdge DownfloodingPoints PotentialDfloodingPoints EmbarkationPoints ImmersionPoints Permissible value

Units length

length

To check that the freeboard lies within a specified range, use a combination of both forms of the minimum/maximum freeboard criteria. Value of GMT or GML at Equilibrium

This criterion is used to check that the GM (transverse or longitudinal) exceeds a specified minimum value. Option The value of

Shall be greater than / Shall not be less than

Description Choose from the following (case insensitive auto-completion is used): GMtransverse GMlongitudinal) Permissible value

Units length

length

GZ Curve Criteria (non-heeling arm) These criteria, calculated from the GZ curve, are calculated from the Large Angle Stability analysis in Hydromax. Value of GMt at

Finds the value of GMt at either a specified heel angle or the equilibrium angle. The criterion is passed if the value of GMt is greater then the required value. GMt is computed from water-plane inertia and immersed volume. Option specified heel angle angle of equilibrium Shall be greater than / Shall not be less than Page 130

Description Value of GMt at either User specified heel angle See Nomenclature Permissible value

Units deg deg length

Chapter 4 Stability Criteria

Value of GZ at

Finds the value of GZ at either a specified heel angle, first peak in GZ curve, angle of maximum GZ or the downflooding angle. The criterion is passed if the value of GZ is greater then the required value. Option specified heel angle angle of first GZ peak angle of maximum GZ first downflooding angle Shall be greater than / Shall not be less than

Description Value of GZ at either User specified heel angle See Nomenclature See Nomenclature See Nomenclature

Units

Permissible value

length

deg deg deg deg

Value of Maximum GZ

Finds the maximum value of GZ within a specified heel angle range. The criterion is passed if the value of GZ is greater than the required value. If you want to check the value of GZ at a certain angle you can set both specified angles as the required angle. If any of the calculated angles for the upper limit are less than the lower limit, they will be ignored when selecting the lowest. If all the upper limit values are less than the lower limit, then the criterion will also fail. This functionality is to allow criteria such as “The maximum GZ at 30deg or greater”. Option in the range from the greater of specified heel angle angle of equilibrium to the lesser of specified heel angle angle of first GZ peak angle of maximum GZ first downflooding angle Shall be greater than / Shall not be less than

Description Value of maximum GZ Lower limit for heel angle range, the greater of the following: User specified heel angle See Nomenclature Upper limit for heel angle range, the lesser of the following: User specified heel angle See Nomenclature See Nomenclature See Nomenclature

Units

Permissible value

length

deg

deg deg deg deg

Page 131

Chapter 4 Stability Criteria

Value of Maximum GZ

Value of GZ at Specified Angle or Maximum GZ below Specified Angle

If the angle at which maximum GZ occurs is greater than a specified value, the value of GZ at the specified angle is calculated. Otherwise the value of maximum GZ is calculated. The required GZ value depends on the angle at which the maximum occurs, see graph below. Option

Page 132

Description

Units

Chapter 4 Stability Criteria

Option heel angle at which required GZ is constant

Description If the angle of maximum GZ is greater than or equal to this value, the required value of GZ is constant and is taken at this specified angle. Otherwise the required value of maximum GZ varies as a hyperbolic function with the angle of maximum GZ. This is φ 0

Units deg

required value of GZ at this angle is

Required value of GZ at the heel angle specified above. This is GZ (φ 0 )

length

limited by first GZ peak angle

Angle at which GZ is measured may be limited to the location of the first peak in the GZ curve Angle at which GZ is measured may be limited to first downflooding angle Permissible value

deg

limited by first downflooding angle Shall be greater than / Shall not be less than

deg length

If φ GZ ≥ φ 0 then GZ (φ 0 ) must be greater than the specified, constant value. max If φ GZ < φ 0 then GZ max must be greater than max

φ0 φ GZ

GZ (φ 0 )

max

where: φ 0 is the specified angle at which the required GZ value becomes a constant

φ GZ

max

is the heel angle at which the maximum GZ of value occurs

GZ (φ 0 ) is the GZ value at φ 0 and GZ max is the maximum value of GZ.

Page 133

Chapter 4 Stability Criteria

Variation of required GZ with angle of maximum GZ

Value of RM at Specified Angle or Maximum RM Below Specified Angle

As above (Value of GZ at specified angle or maximum GZ below specified angle) except the righting moment rather than the righting lever is specified, measured and compared. The righting moment RM is given by:

RM = ∇ρgGZ

where: is the vessel volume of displacement ∇ is the density of the liquid the vessel is floating in ρ is acceleration due to gravity = 9.80665m/s2 g GZ is the righting lever Ratio of GZ Values at Phi1 and Phi2

Calculates the ratio of the GZ values at two specified heel angles. The criterion is passed if the ratio is less then the required value.

Ratio =

GZ (φ1 ) GZ (φ 2 )

Option Phi1, first heel angle, the lesser of Page 134

Description Ratio of GZ values at phi1 and phi2 First heel angle, the lesser of the following:

Units

Chapter 4 Stability Criteria

Option specified heel angle angle of first GZ peak angle of maximum GZ first downflooding angle Phi2, second heel angle, the lesser of specified heel angle angle of first GZ peak angle of maximum GZ first downflooding angle Shall be less than / Shall not be greater than

Description User specified heel angle See Nomenclature See Nomenclature See Nomenclature

Units deg deg deg deg

Second heel angle, the lesser of the following: User specified heel angle See Nomenclature See Nomenclature See Nomenclature

deg deg deg deg

Permissible value

%

Ratio of GZ values at phi1 and phi2

Page 135

Chapter 4 Stability Criteria Angle of Maximum GZ

Finds the angle at which the value of GZ is a maximum positive value, heel angle can be limited by first peak in GZ curve and/or first downflooding angle. The criterion is passed if the angle is greater then the required value. Option limited by first GZ peak angle limited by first downflooding angle Shall be greater than / Shall not be less than

Description Angle of maximum GZ The angle of maximum GZ shall not be greater than the angle at which the first GZ peak occurs The angle of maximum GZ shall not be greater than the angle at which the first downflooding occurs Permissible value

Units deg

deg

deg

Angle of Equilibrium

Finds the angle of equilibrium from the intersection of the GZ curve with the GZ=0 axis. The criterion is passed if the equilibrium angle is less then the required value. Option Shall be less than / Shall not be greater than

Description Angle of equilibrium Permissible value

Units deg

Angle of Downflooding

Finds the angle of first downflooding. The criterion is passed if the downflooding angle is greater then the required value. Option Shall be greater than / Shall not be less than

Description Angle of downflooding Permissible value

Units deg

Angle of Margin Line Immersion

Finds the first/minimum angle at which the margin line immerses. The criterion is passed if the smallest angle at which the margin line immerses is greater then the required value. Option Shall be greater than / Shall not be less than

Page 136

Description Angle of margin line immersion Permissible value

Units deg

Chapter 4 Stability Criteria Angle of Deck Edge Immersion

Finds the first/minimum angle at which the deck edge immerses. The criterion is passed if the smallest angle at which the deck edge immerses is greater then the required value. Option

Description Angle of deck edge immersion Permissible value

Shall be greater than / Shall not be less than

Units deg

Angle of Vanishing Stability

Finds the angle of vanishing stability from the intersection of the GZ curve with the GZ=0 axis. The criterion is passed if the angle of vanishing stability is greater then the required value. Option Shall be less than / Shall not be greater than

Description Angle of vanishing stability Permissible value

Units deg

Range of Positive Stability

The angular range for which the GZ curve is positive is computed. The criterion is passed if the computed range is greater then the required value. Option from the greater of specified heel angle angle of equilibrium to the lesser of first downflooding angle angle of vanishing stability Shall be greater than / Shall not be less than

Description Range of positive stability Lower limit User specified heel angle See Nomenclature Upper limit of the range See Nomenclature

Units

See Nomenclature

deg

Permissible value

deg

deg deg deg

GZ Area between Limits type 1 - standard

The area below the GZ curve and above the GZ=0 axis is integrated between the selected limits and compared with a minimum required value. The criterion is passed if the area under the graph is greater than the required value. Option from the greater of specified heel angle

Description GZ area between limits type 1 - standard Lower limit for integration, from greatest angle of User specified heel angle

Units

deg Page 137

Chapter 4 Stability Criteria

Option angle of equilibrium to the lesser of specified heel angle spec. angle above equilibrium angle of first GZ peak angle of maximum GZ first downflooding angle angle of vanishing stability Shall be greater than / Shall not be less than

Description See Nomenclature Upper limit of integration, from lesser angle of User specified heel angle User specified heel angle above the equilibrium heel angle See Nomenclature See Nomenclature See Nomenclature

Units deg

See Nomenclature

deg

Permissible value

length.angle

GZ area between limits type 1 - standard

Page 138

deg deg deg deg deg

Chapter 4 Stability Criteria GZ area between limits type 2- HSC monohull type

The area under the GZ curve is integrated between the specified limits. However the required minimum area depends on the upper integration limit. The required area is defined below and is based on the area required for IMO MSC.36(63) §2.3.3.2 and IMO A.749(18) §4.5.6.2.1. The criterion is passed if the computed area under the graph is greater then the required value. The required area is defined as follows: If φ max ≥ φ 2 : required area = A2 ; If φ max ≤ φ1 : required area = A1 ; If φ1 < φ max Where:

 A − A2  (φ 2 − φ max ) A2 +  1 φ φ − < φ 2 : required area =  2 1 ;

φ max is the upper integration limit; A1 is the area under the GZ curve required at the specified lower heel angle φ1 ; and A2 is the area under the GZ curve required at the specified higher heel angle φ 2 . For example, if the lower angle was 15° and the required area at this angle was 0.07m.rad and the upper angle was 30° and the required area at this angle was 0.055m.rad, then the required area would be given by:

 0.07 − 0.055  A = 0.55 +  (30 − φ max )  30 − 15 

or simplifying:

A = 0.55 + 0.001 (30 − φ max )

Page 139

Chapter 4 Stability Criteria Variation of required area with upper integration limit

Option

from the greater of specified heel angle angle of equilibrium to the lesser of specified heel angle spec. angle above equilibrium angle of first GZ peak angle of maximum GZ first downflooding angle angle of vanishing stability lower heel angle

required GZ area at lower heel angle higher heel angle required GZ area at higher heel angle Shall be greater than / Shall not be less than

Page 140

Description GZ area between limits type 2- HSC monohull type Lower limit for integration, from greatest angle of User specified heel angle See Nomenclature Upper limit of integration, from smallest angle of User specified heel angle User specified heel angle above the equilibrium heel angle See Nomenclature See Nomenclature See Nomenclature

Units

deg deg

deg deg deg deg deg

See Nomenclature

deg

Minimum angle that requires a GZ area greater than... Until this angle the required GZ area is constant Value of GZ area that is required until the lower heel angle Angle from which the required GZ area remains constant onwards Value of GZ area that is required from the higher heel angle onwards Permissible value

deg

length.angle deg length.angle length.angle

Chapter 4 Stability Criteria

GZ area between limits type 2 - HSC monohull type

GZ area between limits type 3 - HSC multihull type

The area under the GZ curve is integrated between the specified limits. However the required minimum area depends on the upper integration limit ( φ max ). The required area is defined below and is based on the area required for IMO MSC.36 (63) Annex 7 §1.1. The criterion is passed if the computed area under the graph is greater than the required value. required area = A1 (φ1 / φ max ) ; Where:

φ max is the upper integration limit; A1 is the area under the GZ curve required at the specified heel angle φ1 . For example, if the specified angle ( φ1 ) was 30° and the required area at this angle ( A1 ) was 0.055m.rad, then the required area would be given by:

A = 0.055(30 / φ max )

Page 141

Chapter 4 Stability Criteria

Variation of required area with upper integration limit

Option

from the greater of specified heel angle angle of equilibrium to the lesser of specified heel angle spec. angle above equilibrium angle of first GZ peak angle of maximum GZ first downflooding angle angle of vanishing stability higher heel angle required GZ area at higher heel angle Shall be greater than / Shall not be less than

Page 142

Description GZ area between limits type 3 - HSC multihull type Lower limit for integration, from greatest angle of User specified heel angle See Nomenclature Upper limit of integration, from lesser angle of User specified heel angle User specified heel angle above the equilibrium heel angle See Nomenclature See Nomenclature See Nomenclature

Units

deg deg

deg deg deg deg deg

See Nomenclature

deg

Heel angle at which required GZ area is specified Value of GZ area that is required until the higher heel angle Permissible value

deg length.angle length.angle

Chapter 4 Stability Criteria

GZ area between limits type 3 - HSC multihull type

Ratio of GZ area between limits

This criterion calculates the ratio of the two areas between the GZ curve and the GZ=0 axis. φ2

Area 1 Ratio = = abs(Area 2)

∫ GZ (φ )dφ

φ1

 φ4  abs ∫ GZ (φ )dφ  φ   3 

, where “abs” means the absolute value of.

Option

Description Ratio of GZ area between limits

Area 1 from the greater of

Area 1 lower integration limit, φ1

specified heel angle angle of equilibrium

User specified heel angle See Nomenclature

Units

deg deg Page 143

Chapter 4 Stability Criteria

Option Area 1 to the lesser of

Description Area 1 upper integration limit, φ 2

Units deg

specified heel angle angle of first GZ peak angle of maximum GZ first downflooding angle angle of vanishing stability Area 2 from the lesser of

User specified heel angle See Nomenclature See Nomenclature See Nomenclature See Nomenclature

deg deg deg deg deg

specified heel angle angle of first GZ peak angle of maximum GZ first downflooding angle angle of vanishing stability Area 2 to

User specified heel angle See Nomenclature See Nomenclature See Nomenclature See Nomenclature

specified heel angle Shall be greater than / Shall not be less than

User specified heel angle Permissible value

Area 2 lower integration limit, φ3 deg deg deg deg deg

Area 1 upper integration limit, φ4 deg %

This criterion is designed to be calculated on the positive side of the GZ curve only; GZ areas below the GZ=0 axis on the negative heel angle side of the GZ curve are not considered positive. Typically, Area 1 would be from equilibrium to vanishing stability and Area 2 would be from vanishing stability to 180 deg, see graph below. In the example below, the lower and upper integration limits for Area 1 are equilibrium and vanishing stability, respectively and the limits for Area 2 are vanishing stability and 180 deg.

Page 144

Chapter 4 Stability Criteria

Ratio of GZ area between limits – Example 1

In the following example the upper limit for Area 1 has been set to the downflooding angle. The limits for Area 2 remain unchanged.

Page 145

Chapter 4 Stability Criteria

Ratio of GZ area between limits – Example 2

In the final example, the lower integration range for Area 2 has been reduced to the downflooding angle. Note that Area 2 is now A1 – A2.

Page 146

Chapter 4 Stability Criteria

Ratio of GZ area between limits – Example 3

Ratio of positive to negative GZ area between limits

This criterion calculates the ratio of GZ area above the GZ=0 axis to that below the axis in the given heel angle range. Option

in the heel angle range from to Shall be greater than / Shall not be less than Ratio =

Description Ratio of positive to negative GZ area between limits User specified lower limit heel angle User specified upper limit heel angle Permissible value

Units

deg deg %

Area 1 , abs(Area 2)

where “abs” means the absolute value of. And the areas are defined as follows: If both heel angle limits are ≥ zero: Area 1 is the total area between the GZ curve and GZ=0 axis, where the value of GZ > 0; Area 2 is the total area between the GZ curve and GZ=0 axis, where the value of GZ < 0. Area 1 is positive, Area 2 is negative.

Page 147

Chapter 4 Stability Criteria

Ratio of positive to negative GZ area between limits. Positive heel: lower limit = 0deg, upper limit = 180deg.

If both heel angle limits are < zero: Area 1 is the total area between the GZ curve and GZ=0 axis, where the value of GZ < 0; Area 2 is the total area between the GZ curve and GZ=0 axis, where the value of GZ > 0. Area 1 is positive, Area 2 is negative.

Page 148

Chapter 4 Stability Criteria

Ratio of positive to negative GZ area between limits. Negative heel: lower limit = -180deg, upper limit = 0deg.

If the lower heel angle limit < zero, and the upper heel angle limit > zero (the upper limit is assumed to be greater than the lower limit): Area 1 is the total area between the GZ curve and GZ=0 axis, where the value of GZ > 0 for heel angles ≥ 0 plus the area between the GZ curve and GZ=0 axis, where the value of GZ < 0 for heel angles < 0; Area 2 is the total area between the GZ curve and GZ=0 axis, where the value of GZ < 0 for heel angles ≥ 0 plus the area between the GZ curve and GZ=0 axis, where the value of GZ > 0 for heel angles < 0. Area 1 is positive, Area 2 is negative.

Page 149

Chapter 4 Stability Criteria

Ratio of positive to negative GZ area between limits. Positive and negative heel: lower limit = -180deg, upper limit = 180deg.

Heeling arm definition There are several heeling arms that are used for the criteria. They are defined below. • • • • • • • • •

General heeling arm General cos+sin heeling arm Heeling due to passenger crowding Heeling due to turning Heeling due to lifting of weights Heeling due to towing or bollard-pull Heeling due to wind Gust ratio Areas and levers

General heeling arm

The general form of the heeling arm is given below:

H (φ ) = A cos n (φ ) where:

φ is the heel angle, A is the magnitude of the heeling arm, cos n describes the shape of the curve.

Page 150

Chapter 4 Stability Criteria

Typically n=1 is used for passenger crowding and vessel turning since the horizontal lever for the passenger transverse location reduces with the cosine of the heel angle. For wind n=2 is often used for heeling because both the projected area as well as the lever decrease with the cosine of the heel angle. However, some criteria, such as IMO Severe wind and rolling (weather criterion) have a heeling arm of constant magnitude, in this case n=0 should be used. Heeling arm criteria dependent on displacement

Some heeling arm criteria are dependent on the displacement of the vessel for the calculation of the Heeling Arm. For example, the value “A” in:

H (φ ) = A cos n (φ ) , is manually calculated from:

A=

M ∆

, where M = heeling moment ∆ = displacement. This means that the heeling arm will vary with the displacement. Hydromax will not take the change in displacement into account. When evaluating these criteria that are dependent on displacement, care has to be taken to make sure any change in displacement is taken into account. For large angle stability this means that every loadcase will have its own set of criteria. For Limiting KG and Batch analysis, there are two options: 1. Calculate the worst-case lever based on the displacement and VCG that result in the worst lever and see if the criterion is actually a limiting one for KG. 2. Calculate limiting KG at single displacements and change the heeling arm for each displacement. General cos+sin heeling arm

Some criteria, notably lifting of weights, require a heeling arm with both a sine and cosine component:

(

H (φ ) = k A cos n (φ ) + B sin m (φ )

)

It should be noted that provided the indices are both unity, the same heeling arm form may be used for computing towing heeling arms of the form:

H (φ ) = k ( A cos(φ + δ ) + B sin(φ + δ ) )

in this case a constant angle (in the case of towing, the angle of the tow above the horizontal) is included. It may be shown that this is equivalent to:

H (φ ) = k (C cos(φ ) + D sin(φ ) )

where:

Page 151

Chapter 4 Stability Criteria

R2 B C= 1 + tan 2 (α − δ ) , D = C tan(α − δ ) , R 2 = A 2 + B 2 and tan α = A Heeling due to passenger crowding

The magnitude of the heel arm is given by:

H pc (φ ) = where:

n pas MD ∆

cos n (φ )

n pas is the number of passengers M is the average mass of a single passenger D is the average distance of passengers from the vessel centreline ∆ is the vessel mass (same units as M ) The heeling arm parameters are specified as follows: Option number of passengers: nPass

Description Number of passengers

Units none

passenger mass: M distance from centreline: D cosine power: n

Average mass of one passenger Average distance of the passengers from the centreline Cosine power for curve - defines shape

mass length none

Heeling due to turning

The magnitude of the heel arm is derived from the moment created by the centripetal force acting on the vessel during a high-speed turn and the vertical separation of the centres of gravity and hydrodynamic lateral resistance to the turn. The heeling arm is obtained by dividing the heeling moment by the vessel weight. The heeling arm is thus given by:

H t (φ ) = a

v2 h cos n (φ ) Rg

where (in consistent units): a is a constant, theoretically unity v is the vessel velocity R is the radius of the turn h is the vertical separation of the centres of gravity and lateral resistance The heeling arm parameters are specified as follows: Option constant: a vessel speed: v

Page 152

Description Constant which may be used to modify the magnitude of the heel arm, normally unity Vessel speed in turn

Units none length/time

Chapter 4 Stability Criteria

turn radius: R turn radius, R, as percentage of LWL Vertical lever: h

h = KG h = KG - mean draft / 2 h = KG - vert. centre of projected lat. u'water area cosine power: n

Turn radius may be specified directly Or, as some criteria require, as percentage of LWL There are four options for specifying h (all options are calculated with the vessel upright at the loadcase displacement and LCG): User specified h is taken as KG - position of G above baseline in upright condition h is taken as KG less half the mean draft. h is taken as the vertical separation of the centres of gravity and underwater lateral projected area. Cosine power for curve - defines shape

length % length

length length length

none

Heeling due to lifting of weights

This is used to simulate the effect of lifting a weight from its stowage position. The magnitude of the heel arm is given by:

H lw (φ ) =

M [h cos(φ ) + v sin(φ )] ∆

where: M is the mass of the weight being lifted h is horizontal separation of the centre of gravity of the weight in its stowage position and the suspension position v is vertical separation of the centre of gravity of the weight in its stowage position and the suspension position ∆ is the vessel mass (same units as M ) The heeling arm parameters are specified as follows: Option Mass being lifted: M vertical separation of suspension from stowage position: v

horizontal separation of suspension from stowage position: h

Description Mass of weight being lifted Vertical separation of suspension point from weight’s original stowage position on the vessel. This value is positive if the suspension position is above the original stowage position. Horizontal separation of suspension point from weight’s original stowage position on the vessel This value is positive if the horizontal shift of the weight should produce a positive heeling moment.

Units mass length

length

Heeling due to towing or bollard-pull

The magnitude of the heel arm is given by:

Page 153

Chapter 4 Stability Criteria

H tow (φ ) =

[

T v cos n (φ + τ ) + h sin(φ + τ ) g∆

]

where: T is the tension in the towline or vessel thrust, expressed as a force. h is horizontal offset of the tow attachment position from the vessel centreline v is vertical separation tow attachment position from the vessel’s vertical centre of thrust ∆ is the vessel mass n is the power index for the cosine term which may be used to change the shape of the heeling arm curve τ is the (constant) angle of the towline above the horizontal. It is assumed that the towline is sufficiently long that this angle remains constant and does not vary as the vessel is heeled. The heeling arm parameters are specified as follows: Option tension or thrust: T vertical separation of propeller centre and tow attachment: v horizontal offset of tow attachment: h

angle of tow above horizontal: tau cosine power: n

Description Tension in towline or vessel thrust Vertical separation tow attachment position from the vessel’s vertical centre of thrust. This value is positive if the towline is above the thrust centre. Horizontal offset of the tow attachment position from the vessel centreline. This value is positive if the offset is in the direction of the tow. Angle of tow above the horizontal

Units force length

angle

Cosine power for curve - defines shape

none

length

Heeling due to wind

In the case of the wind pressure based formulation, the wind heeling arm is given by:

H w (φ ) = a

PA(h − H ) n cos (φ ) g∆

where: a is a constant, theoretically unity A is the windage area at height h ∆ is the vessel mass P is the wind pressure H is the vertical centre of hydrodynamic resistance to the wind force In the case of the wind velocity based formulation, the wind heeling arm is given by:

H w (φ ) = a

v 2 A(h − H ) n cos (φ ) g∆

where: a is now effectively an average drag coefficient for the windage area multiplied by the air density and has units of density Page 154

Chapter 4 Stability Criteria

v is the wind speed. And the other parameters are described as above. Option constant: a

Description Constant which may be used to modify the magnitude of the heel arm, normally unity for pressure based formulation or 0.5 ρair CD for the velocity formulation; where ρair is the density of air and CD is an average drag coefficient for the windage area

wind model

Pressure or Velocity (type “P” or “V”)

wind pressure or velocity

Actual velocity of pressure - depends on wind model

area centroid height: h

Height of user defined total or additional windage area User may specify either a total windage area Or, an area to be added to the windage area computed by Hydromax based on the hull sections There are four options for specifying H (all options are calculated with the vessel upright at the loadcase displacement and LCG): User specified H is taken as half the mean draft. H is taken as the vertical centre of underwater lateral projected area.

total area: A additional area: A

height of lateral resistance: H

H = mean draft / 2 H = vert. centre of projected lat. u'water area H = waterline cosine power: n

H is taken as the waterline Cosine power for curve - defines shape

Units none for pressure based formulation ; mass/length 3 for velocity based formulation

mass/(time2 length) or length/ time length length2 length2

length

length length

length none

Gust ratio

Some criteria require a Gust Ratio, this is the ratio of the magnitude of the wind heeling arm during a gust to the magnitude of the wind heeling arm under steady wind.

GustRatio =

H gust H steady

Page 155

Chapter 4 Stability Criteria Areas and levers

Some criteria require the evaluation of above and below water lateral projected areas and their vertical centroids. The user may also specify additional areas and vertical centroids or the total areas and vertical centroids. In all cases the vertical centroids are given in the Maxsurf/Hydromax co-ordinate system; i.e.: from the model’s vertical datum, positive upwards. Centroids of area are calculated for the upright vessel (zero trim and heel) at the mean draft. The areas are calculated from the hydrostatic sections used by Hydromax; thus, increasing the number of sections will increase the accuracy of the area calculation; further, only “Hull” surfaces are included in the calculation - “Structure” surfaces are ignored. The vertical position of the keel, K, is assumed to be at the baseline (as set up in the Frame of Reference dialog), even if the baseline does not correspond to the physical bottom of the vessel.

Heeling arms for specific criteria - Note on unit conversion There are quite a few different ways in which different authorities define their heeling arms. The approach that has been taken in Hydromax is to reflect the physics of what is generating the heeling moment. Be careful as some criteria specify heeling arms and some specify heeling moments or “moments” in mass.length. All Hydromax criteria use a heeling arm since this is what is ultimately plotted on the GZ curve. To obtain the heeling arm from the heeling moment, it is necessary to divide by vessel weight ( g∆ ); and in the case of “moments” in mass.length, it is necessary to divide by vessel mass. Hydromax uses an internal conversion of knots to m/s based on the International Nautical mile which is defined as exactly 1852m (International Hydrographic Conference, Monaco, 1929). Thus 1 knot = 1852/3600 = 0.5144444... m/s. (Note that the UK nautical mile is 6080ft = 1853.184m; giving a conversion multiplier for knots to m/s of 0.51477333...) In the following section, the conversions for some common criteria have been explained. IMO Code on Intact Stability A.749(18) amended to MSC.75(69)

3.1.2.6 - Heeling due to turning Heeling moment defined by:

M R = 0.196

V02 d  ∆ tonne  KG −  2  [kNm] L 

Where:

MR

= heeling moment in tonne.m

V0

= service speed in m/s = length of ship at waterline in m

L

Page 156

Chapter 4 Stability Criteria

∆ tonne = displacement in tonne d = mean draft m KG = height of centre of gravity above keel in m Hence the heeling arm, H R = 1000 M R / ∆g [m], is given by:

H R = 0.196

V02 ∆  d  1000 V02  d KG − 0 . 196 =    KG −  L 1000  Lg  2  [m] 2  ∆g

Where:

g

= standard acceleration due to gravity = 9.80665 m/s2 = displacement in kg

∆

The heeling arm in Hydromax is defined as:

HR = a

V2 Rg

h [m],

Where:

V R h a

= vessel speed in m/s = radius of turn in m = height of centre of gravity above centre of lateral resistance in m = non-dimensional constant (theoretically unity)

Thus equating the required IMO heeling arm to the Hydromax heeling arm, we obtain:

a

V2 Rg

h = 0.196

V02  d  KG −  2 Lg 

Equating similar terms:

d  h =  KG −  2  V = V0 and assuming that the ratio of the turn radius to the vessel length is 5.1:1, we obtain:

and

R = 510% L

a = 0.196 × 510% = 0.9996 L Note that it suffices that a = 0.196 and any ratio of turn radius to vessel length and R constant a that satisfies this relationship may be chosen, the choice of a ratio of 5.1:1 merely gives a constant approaching the theoretically correct value of unity. 3.2 - Severe wind and rolling criterion (weather criterion) Heeling arm defined by:

lw1 =

PAZ 1000 g 9.81∆ tonne [m]

Where:

l w1

= heeling arm in m Page 157

Chapter 4 Stability Criteria

P A Z ∆ tonne

= wind pressure in Pa = projected lateral windage in m2 = vertical separation of centroids of A and underwater lateral area in m

g9.81

= IMO assumed value of gravitational acceleration - 9.81m/s2

= displacement in tonne

The heeling arm in Hydromax is defined as:

Hw = a

PA(h − H ) g∆ [m]

Where:

g

= standard acceleration due to gravity = 9.80665 m/s2 = displacement in kg = height of centroid of A in m = height of centroid of underwater lateral area in m = non-dimensional constant (theoretically unity)

∆ h H a

Thus equating the required IMO heeling arm to the Hydromax heeling arm, we obtain:

a

PA(h − H ) PAZ = g∆ 1000 g 9.81∆ tonne

Equating similar terms: and

h−H = Z

a=

g g 9.81

=

9.80665 = 0.99966 9.81

IMO HSC Code MSC.36(63)

Annex 6 1.1.4 - Heeling moment due to wind pressure Heeling moment defined by:

M v = 0.001PAZ [kNm] Where:

Mv P A Z

= heeling moment in kNm = wind pressure in Pa = projected lateral windage in m2 = vertical separation of centroids of A and underwater lateral area in m

Hence the heeling arm, H v = 1000 M v / ∆g [m], is given by:

H R = 0.001PAZ

1000 PAZ = ∆g ∆g [m]

Where:

g

∆

Page 158

= standard acceleration due to gravity = 9.80665 m/s2 = displacement in kg

Chapter 4 Stability Criteria

The heeling arm in Hydromax is defined as:

Hw = a

PA(h − H ) g∆ [m]

Where:

g

= standard acceleration due to gravity = 9.80665 m/s2 = displacement in kg = height of centroid of A in m = height of centroid of underwater lateral area in m = non-dimensional constant (theoretically unity)

∆ h H a

Thus equating the required IMO heeling arm to the Hydromax heeling arm, we obtain:

a

PA(h − H ) PAZ = g∆ g∆

Equating similar terms: and

h−H = Z a = 1 .0

Annex 7 1.3 - Heeling due to wind Heeling arm defined by:

HL1 =

PAZ 9800∆ tonne [m]

Where:

HL1

P A Z

= heeling arm in m = wind pressure in Pa = projected lateral windage in m2 = vertical separation of centroid of A and half the lightest service draft in m

∆ tonne = displacement in tonne The heeling arm in Hydromax is defined as:

Hw = a

PA(h − H ) g∆ [m]

Where:

g

∆ h H a

= standard acceleration due to gravity = 9.80665 m/s2 = displacement in kg = height of centroid of A in m = height of half the lightest service draft in m = non-dimensional constant (theoretically unity)

Thus equating the required IMO heeling arm to the Hydromax heeling arm, we obtain:

a

PA(h − H ) PAZ = 9800∆ tonne g∆

Page 159

Chapter 4 Stability Criteria

Equating similar terms: and

h−H = Z

a=

g∆ 9.80665∆ = = 1.00068 9800∆ tonne 9.8∆

Where the effect of wind plus gust is required, the factor a should be multiplied by the gust factor – typically 1.5. Hence, in the case of wind plus gust, a becomes 1.50102 USL code (Australia)

USL C.1.1.3 - Wind heeling moment USL wind heeling “moment” is specified as:

M = 0.000102 PA(h − H ) [tonne.m] Where:

h H P A

= height of centroid of A in m = height of centroid of underwater lateral area in m = wind pressure in Pa = projected lateral windage in m2

Thus the heeling arm is given by:

H = 0.000102 PA(h − H )

1000 ∆ [m]

The heeling arm in Hydromax is defined as:

H =a

PA(h − H ) g∆ [m]

Where:

g

∆ a

= standard acceleration due to gravity = 9.80665 m/s2 = displacement in kg = non-dimensional constant (theoretically unity)

Thus equating:

H =a

1000 PA(h − H ) = 0.000102 PA(h − H ) ∆ g∆

simplifying and rearranging:

a = 0.000102 × 1000.0 × g = 0.102 × 9.80665 = 1.0002783 USL C.1.1.4 - Heeling moment due to turning USL wind heeling “moment” is specified as: 2 ∆ tonnes h v kts M = 0.0053 L [tonne.m]

Where:

v kts

= vessel speed in knots

∆ tonne = displacement in tonne Page 160

Chapter 4 Stability Criteria

h L

= height of centre of gravity above centre of lateral resistance in m = waterline length of vessel in m

Thus the heeling arm is given by:

H = 0.0053

2 v kts ∆ tonnes h 1 × 1000.0 L ∆ [m]

Where:

∆

= displacement in kg

The heeling arm in Hydromax is defined as:

H =a

V2 Rg

h [m],

Where:

V R h a

= vessel speed in m/s = radius of turn in m = height of centre of gravity above centre of lateral resistance in m = non-dimensional constant (theoretically unity)

Thus equating the required USL heeling arm to the Hydromax heeling arm, we obtain:

V2

2 v kts ∆ tonnes h 1 × 1000.0 h = 0.0053 a L ∆ Rg

simplifying and rearranging: 2 ∆ tonnes 1 1 R v kts R = 5.3 g a = 5.3g 2 2 LV L 0.5144 1000.0 ∆

finally, with g = 9.80665 [ms-2]:

a = 0.196424

R L

R = 509% Assuming that the ratio of the turn radius to the vessel length, L gives a value for a:

a = 0.196424 × 509% = 0.999798 R a = 0.196424 Note that it suffices that L , and any ratio of turn radius to vessel length and constant a that satisfies this relationship may be chosen, the choice of a ratio of 509% merely gives a constant approaching the theoretically correct value of unity.

Heeling arm criteria These criteria are derived from the GZ curve calculated from the Large Angle Stability analysis in Hydromax in conjunction with user defined heeling arms. In all cases there is a generic form of the criterion with the general form of the heeling arm, and in some cases, the same criteria are given with a specific, heeling arm due to wind pressure, passenger crowding or vessel turning.

Page 161

Chapter 4 Stability Criteria Value of GMT at equilibrium - general heeling arm

Calculates the transverse metacentric height (GMT) at the intersection of the GZ and heel arm curves. The criterion is passed if the GMT value is greater then the required value. GMT is computed from the waterplane inertia and the displaced volume at the equilibrium heel angle. Uses the general heel arm as described in §General heeling arm. Value of GZ at equilibrium - general heeling arm

Calculates the value of the GZ curve at the equilibrium intersection of the GZ and heel arm curves. The criterion is passed if the GZ value is greater then the required value. Uses the general heel arm as described in §General heeling arm

Value of GZ at equilibrium - general heeling arm

Page 162

Chapter 4 Stability Criteria Value of maximum GZ above heeling arm - general heeling arm

Finds the maximum value of (GZ - heel arm) at or above a specified heel angle. The first downflooding angle may be selected as an upper limit. The criterion is passed if the value of (GZ - heel arm) is greater then the required value.

Value of maximum GZ above heeling arm - general heeling arm

Ratio of GZ values at phi1 and phi2 - general heeling arm

Used to check the ratio of GZ values at two points on the GZ curve. The heel arm is used to define the equilibrium angle and the heel angle where (GZ - heel arm) is maximum. The criterion is passed if the ratio is less than the required value.

GZ (φ1 ) Ratio = GZ (φ 2 )

Page 163

Chapter 4 Stability Criteria Angle of maximum GZ above heeling arm - general heeling arm

Calculates the heel angle at which the difference between the GZ curve and the heeling arm is greatest (GZ - Heel Arm is maximum, positive). The criterion is passed if the angle is greater then the required value.

Angle of maximum GZ above heeling arm - general heeling arm

Angle of equilibrium - general heeling arm

Calculates the angle of equilibrium with a General heeling arm applied. The equilibrium angle is the smallest positive angle where the GZ and heeling arm curves intersect and the GZ curve has positive slope. The criterion is passed if the equilibrium angle is less then the required value.

Page 164

Chapter 4 Stability Criteria

Angle of equilibrium - general heeling arm

Angle of equilibrium ratio - general heeling arm

Calculates the ratio of the angle of equilibrium (with a General heeling arm applied) to another, selectable angle. The angle of equilibrium is computed as described in §Angle of equilibrium - general heeling arm. Ratio =

φ equilibrium φ specified

The other angle used to compute the ratio may be one of the following: Required angle for ratio calculation Auto complete text Marginline immersion angle MarginlineImmersionAngle Deck edge immersion angle DeckEdgeImmersionAngle Angle of first GZ peak DownfloodingAngle Angle of maximum GZ MaximumGZAngle First downflooding angle FirstGZPeakAngle Angle of vanishing stability with heel arm VanishingStabilityWithHeelArmAngle Page 165

Chapter 4 Stability Criteria

Angle of equilibrium - passenger crowding heeling arm

Calculates the angle of equilibrium with the heeling arm due to passenger crowding applied. The heeling arm is calculated from the number, weight and location of the passengers, see §Heeling due to passenger crowding. Angle of equilibrium - high-speed turn heeling arm

Calculates the angle of equilibrium with the heeling arm due to high speed turning applied. The heeling arm is calculated from the turn radius, vessel speed and height of the vessel’s centre of gravity, see §Heeling due to turning. Angle of vanishing stability - general heeling arm

Calculates the location of the first intersection of the GZ curve and heel arm curve where the slope of the GZ curve is negative. The criterion is passed if the angle is greater then the required value. This criterion should not be confused with the range of positive stability.

Angle of vanishing stability - general heeling arm

Page 166

Chapter 4 Stability Criteria

Range of positive stability - general heeling arm

Computes the range of positive stability with the heeling arm. [Range of stability] = [Angle of vanishing stability] – [Angle of equilibrium] The criterion is passed if the value of range of stability is greater then the required value.

Range of positive stability - general heeling arm

GZ derived heeling arm - general heeling arm

This criterion is used to calculate the amplitude of a heeling arm derived from the value of GZ at a certain heel angle. The GZ value used to define the heeling arm is the GZ at one of the following heel angles: • • • • •

specified angle of heel angle of first peak in GZ curve angle at which maximum GZ occurs angle of first downflooding immersion angle of margin line or deck edge

Page 167

Chapter 4 Stability Criteria

The heeling arm is then calculated as described by the equation below, and is then compared with a minimum required value.

A=

GZ φ

α cos n φ

where:

A n

φ

Amplitude of heeling arm Shape of heeling arm (n = 0 for constant heeling arm) Specified heel angle

GZ φ

Value of GZ at specified heel angle

α

Required ratio = GZ φ / HAφ

GZ area derived heeling arm - general heeling arm

This criterion is used to calculate the amplitude of a heeling arm derived from the area under the GZ curve between specified limits. The area under both the GZ and heeling arm curves is integrated between the same specified limits, see below. Lower integration limit, φ1 : • specified angle of heel • angle of equilibrium

Upper integration limit, φ 2 : • • • • • •

spec. heel angle spec. angle above equilibrium angle of first GZ peak angle of max. GZ first downflooding angle angle of vanishing stability

It is also possible to specify a minimum heel angle for the upper integration limit. Any negative areas (due to negative GZ) up to this minimum upper integration heel angle will be deducted from the total area under the GZ curve. The amplitude of the heeling, which satisfies the equation below arm is then found and compared with a minimum required value. φ2

φ2

∫φ

A cos n φ dφ =

1

A n

φ

GZ

α

Page 168

∫φ

GZ dφ

1

α

Amplitude of heeling arm Shape of heeling arm (n = 0 for constant heeling arm) heel angle GZ curve Required ratio

Chapter 4 Stability Criteria GZ area derived heeling arm (type 2) - general heeling arm

This criterion is used to simulate the effects of wind heeling whilst the vessel is rolling in waves. Because of the many different ways in which this criterion is used it has several options for defining the way in which the areas are calculated. With the wind pressure acting on it, the vessel is assumed to roll to windward under the action of waves and then roll to leeward. The rollback angle is taken from the equilibrium angle with the wind heeling arm. A heeling arm of prescribed shape is found such that the specified area ratio is met. The amplitude of the heeling arm is then compared with a required minimum value. The roll back may be specified as either: • a fixed angular roll back from the angle of equilibrium with the wind heel arm; • roll back to the vessel equilibrium angle ignoring the wind heeling arms (i.e.: where the GZ curve crosses the GZ=0 axis with positive slope); or

• roll back to a specified heel angle.

Note The Large Angle Stability analysis heel angle range should include a sufficient negative range to allow for the rollback angle. For more information see: §Heel. Area 1 =

φ2

∫φ (GZ (φ ) − heel arm(φ ))dφ 1

Area 2 =

φ2

∫φ (heel arm(φ ) − GZ (φ ))dφ 1

Area 1 Ratio = Area 2

Page 169

Chapter 4 Stability Criteria

GZ area derived heeling arm (type 2) - general heeling arm

Angle of equilibrium - derived wind heeling arm

The derived wind heeling criterion is used to check that the steady heel angle due to wind pressure exceeds a certain value. The steady heel arm is derived from a gust of specified ratio. The wind gust will cause the vessel to heel over to the lesser of a specified heel angle, angle of the first GZ peak, angle of maximum GZ or the first downflooding angle. The vessel is assumed to be safe from gusts up to the specified ratio, if the angle of steady heel is greater than the angle. This means that the lesser of: a specified heel angle, first peak in GZ curve, angle of maximum GZ or the first downflooding angle, should be large enough to withstand a gust from a steady wind heeling angle larger than ….

Page 170

Chapter 4 Stability Criteria

ngle of equilibrium - derived wind heeling arm

Ratio of equilibrium angles - derived heeling arm

This criterion is used to compare the equilibrium angles with two different heeling arms. The first equilibrium angle, φ1, is the angle of equilibrium with a derived heeling arm. The second equilibrium angle, φ2, is the angle of equilibrium with a specified heeling arm. The derived heeling arm is chosen such that the areas, A1 and A2, are in the specified ratio. There are several options which can be used to define the upper and lower ranges for the area integrations. The specified heeling arm is specified by an amplitude and cosine power; the same cosine power is used for both the specified and the derived heeling arms.

Page 171

Chapter 4 Stability Criteria

Ratio of equilibrium angles - derived heeling arm

Area 1 =

φ2

∫φ (GZ (φ ) − heel arm(φ ))dφ 1

Area 2 =

φ2

∫φ (heel arm(φ ) − GZ (φ ))dφ 1

Area 1 Ratio of areas = Area 2 φ1 = Angle of equilibrium with heeling arm derived from required area ratio (purple heeling arm) φ2 = Angle of equilibrium with specified heeling arm (orange heeling arm) The criterion is passed if the ratio φ2 : φ1 is less than the required value. Thus if it is required that φ2 be less than φ1, then the ratio φ2 : φ1 must be less than unity. Option A Page 172

Description Magnitude of specified heeling arm

Units length

Chapter 4 Stability Criteria

n required area ratio Area1 / Area2 options options options

required value

Cosine power to describe shape of both specified and derived heelning arms The required area ratio used to find the derived heeling arm magnitude Specify lower integration limit for Area1 Specify upper integration limit for Area1 Specify lower integration limit for Area2; the upper integration limit is always the angle of equilibrium with derived heel arm Specifies the maximum allowable ratio of equilibrium heel angle with the specified heel arm to the equilibrium heel angle with the derived heel arm (phi2 / phi1). This value is normally less than or equal to 100%, indicating that the equilibrium heel angle with the specified heel arm must be less than the equilibrium heel angle with the derived heel arm

deg deg deg

Note The Large Angle Stability analysis heel angle range should include a sufficient negative range to allow for the rollback angle. For more information see: §Heel. GZ area between limits - general heeling arm

Computes the area below the GZ curve and above the heel arm curve between the specified heel angles. The criterion is passed if the area is greater than the required value. φ2

Area =

∫φ (GZ (φ ) − heel arm(φ ))dφ 1

Page 173

Chapter 4 Stability Criteria

GZ area between limits - general heeling arm

Ratio of areas type 1 - general heeling arm

The ratio of the area between the GZ curve and heel arm and the area under the GZ curve is computed. This criterion is based on the area ratio required by various Navies’ turning and passenger crowding criteria. Type 1 stands for which areas are being integrated to calculate the ratio (see graph). The criterion is passed if the ratio is greater than the required value. φ2

(GZ (φ ) − heel arm(φ ) )dφ Area 1 = ∫φ ; 1

φ4

Area 2 =

∫φ GZ (φ )dφ ; 3

Area 1 Ratio = Area 2

Page 174

Chapter 4 Stability Criteria

Ratio of areas type 1 - general heeling arm

Ratio of areas type 1 - general cos+sin heeling arm

This is a very similar criterion to § Ratio of areas type 1 - general heeling arm; the only difference being the shape of the heel arm. In this criterion the heel arm has both a sine and a cosine component. This is used to simulate the effects of lifting weights and is used by several Navies. The modified form of the heeling arm is given below, for further information also see §General cos+sin heeling arm

Page 175

Chapter 4 Stability Criteria

(

H (φ ) = k A cos n (φ ) + B sin m (φ )

)

φ2

Area 1 =

∫φ (GZ (φ ) − heel arm(φ ))dφ 1

;

φ4

Area 2 =

∫φ GZ (φ )dφ 3

;

Area 1 Ratio = Area 2 Ratio of areas type 2 - general wind heeling arm

This criterion is used to simulate the effects of wind heeling whilst the vessel is rolling in waves. Because of the many different ways in which this criterion is used it has several options for defining the way in which the areas are calculated. If a gust ratio of greater than 1.0 is used, the vessel is assumed to roll to windward (under the action of waves with the steady wind pressure acting on it, then roll to leeward under a gust. Hence the rollback angle is taken from the equilibrium angle with the steady wind heeling arm, but the integration for Area 1 is taken from the equilibrium with the gust wind heeling arm. The roll back may be specified as either a fixed angular roll back from the angle of equilibrium with the steady wind heel arm or can be rolled back to the vessel equilibrium angle ignoring the wind heeling arms (i.e.: where the GZ curve crosses the GZ=0 axis with positive slope). Note The Large Angle Stability analysis heel angle range should include a sufficient negative range to allow for the rollback angle. For more information see: §Heel. φ2

(GZ (φ ) − gust heel arm(φ ) )dφ Area 1 = ∫φ 1

Area 2 =

φ2

∫φ (gust heel arm(φ ) − GZ (φ ))dφ 1

Area 1 Ratio = Area 2

Page 176

Chapter 4 Stability Criteria

Page 177

Chapter 4 Stability Criteria Ratio of areas type 2 - general wind heeling arm

Multiple heeling arm criteria These criteria are used to check the effects of combinations of three heeling arms: • Heeling due to passenger crowding • Heeling due to turning • Heeling due to wind

The combined heeling arms are computed by adding the values of the individual heeling arms at each heel angle. Ratio of GZ values at phi1 and phi2 - multiple heeling arms

Checks the ratio of GZ values as per §Ratio of GZ values at phi1 and phi2 - general heeling arm and uses the following specific heeling arms: • Heeling due to passenger crowding • Heeling due to turning • Heeling due to wind

Ratio of GZ values at phi1 and phi2 - multiple heeling arms

Page 178

Chapter 4 Stability Criteria Angle of equilibrium - multiple heeling arms

Checks the equilibrium heel angle as per §Angle of equilibrium - general heeling arm and uses the following specific heeling arms: • Heeling due to passenger crowding • Heeling due to turning • Heeling due to wind

Angle of equilibrium - multiple heeling arms

GZ area between limits - multiple heeling arms

Checks the area under the heel angle as per §GZ area between limits - general heeling arm and uses the following specific heeling arms: • Heeling due to passenger crowding • Heeling due to turning • Heeling due to wind

Page 179

Chapter 4 Stability Criteria

GZ area between limits - multiple heeling arms

Ratio of areas type 1 - multiple heeling arms

Checks the area under the heel angle as per §Ratio of areas type 1 - general heeling arm and uses the following specific heeling arms: • Heeling due to passenger crowding • Heeling due to turning • Heeling due to wind

Page 180

Chapter 4 Stability Criteria

Ratio of areas type 1 - multiple heeling arms

Heeling arm, combined criteria Several criteria require the evaluation of several individual criteria components. Although it is possible to evaluate these criteria by evaluation of their individual components, for simplicity the common combinations have been combined into single criteria. Note: At least one of the individual criteria has to be selected.

Page 181

Chapter 4 Stability Criteria

Combined criteria (ratio of areas type 1) - general heeling arm

This is a combined criterion where three individual criteria must be met. These are: 1. Angle of steady heel must be less than a specified value. The Angle of steady heel is obtained as per §Angle of equilibrium - general heeling arm. 2. The area ratio must be greater than a specified value. The area ratio is evaluated as per § Ratio of areas type 1 - general heeling arm 3. The ratio of the value of GZ at equilibrium to the value of maximum GZ must be less than a specified value.

Combined criteria (ratio of areas type 1) - general heeling arm

Combined criteria (ratio of areas type 1) - passenger crowding

This criterion is essentially the same as its generic form: Combined criteria (ratio of areas type 1) - general heeling arm, however the heel arm is the specific passenger crowding form. Combined criteria (ratio of areas type 1) - high-speed turn

This criterion is essentially the same as its generic form: Combined criteria (ratio of areas type 1) - general heeling arm, however the heel arm is the specific high-speed turning form.

Page 182

Chapter 4 Stability Criteria Combined criteria (ratio of areas type 1) - general cos+sin heeling arm

The lifting criterion is the same as the Combined criteria (ratio of areas type 1) - general heeling arm except that the heel arm has both a cos and sin component.

Combined criteria (ratio of areas type 1) – cos+sin heeling arm

Combined criteria (ratio of areas type 1) - lifting weight

This criterion is essentially the same as its generic form: Combined criteria (ratio of areas type 1) - general cos+sin heeling arm, however the heel arm is the specific lifting of a heavy weight form. Combined criteria (ratio of areas type 1) - towing

This criterion is essentially the same as its generic form: Combined criteria (ratio of areas type 1) - general cos+sin heeling arm, however the heel arm is the specific towing form. Combined criteria (ratio of areas type 2) - general wind heeling arm

This is a widely applicable wind heeling criterion in its most generic format. The heeling arm is specified simply by a magnitude and cosine power. Optionally, a gust wind can be applied. 1. Angle of steady heel must be less than a specified value. The angle of steady heel is obtained as per Angle of equilibrium - general heeling arm.

Page 183

Chapter 4 Stability Criteria

2. The area ratio must be greater than a specified value. The area ratio is evaluated as per Ratio of areas type 2 - general wind heeling arm. 3. The ratio of the value of GZ at equilibrium to the value of maximum GZ must be less than a specified value. Note The Large Angle Stability analysis heel angle range should include a sufficient negative range to allow for the rollback angle. For more information see: §Heel.

Page 184

Chapter 4 Stability Criteria

Area definition

Page 185

Chapter 4 Stability Criteria

If required, a reduction of the GZ curve may be applied. If this is done, all calculations are done using a reduced GZ’ curve which is computed at each heel angle as follows:

GZ ' (φ ) = GZ (φ ) − B cos m (φ ) This criterion may be used to evaluate the following specific criteria (as well as many others of similar format): • US Navy DDS079-1: §079-1-c(9) 1, §079-1-c(9) 4, • Royal Navy NES 109: §1.2.2, §1.3.5, §1.4.2 Initial impulse and Wind heeling criteria • RAN A015866: §4.4.4.2, §4.8, §4.9.5 • IMO A.749(18) Code on intact stability: §3.2 • IMO MSC.36(63) High-speed craft code §2.3.3.1 • ISO/FDIS 12217-1:2002(E) Small Non-Sailing Boats §6.3.2

Combined criteria (ratio of areas type 2) - wind heeling arm

This criterion is exactly the same as §Combined criteria (ratio of areas type 2) - general wind heeling arm except that the magnitude of the heeling arm is automatically calculated from the wind pressure (or velocity), projected area and area lever information.

Page 186

Chapter 4 Stability Criteria

Area definition

Page 187

Chapter 4 Stability Criteria

Note The Large Angle Stability analysis heel angle range should include a sufficient negative range to allow for the rollback angle. For more information see: §Heel.

Other criteria Other criteria, which do not easily fall into the categories above, are found here. Other criteria - STIX

The stability index criterion or STIX criterion as described in ISO/FDIS 122172:2002(E) is used to assess the stability of sailing craft. The required input parameters are described below. Please refer to ISO/FDIS 12217-2:2002(E) for exact definitions of parameters and how they should be calculated. Option delta

AS, sail area ISO 8666

height of centroid of AS

LH, length

BH, beam of hull

Page 188

Description Adjustment to STIX rating, either 0 or 5. δ = 5 if the vessel, when fully flooded with water, has reserve buoyancy and positive righting lever at a heel angle of 90º . δ = 0 in all other cases. Sail area as defined in ISO 8666. Note that no additional windage areas are calculated by Hydromax for this criterion. Height of sail area centre of effort from model’s vertical datum (not necessarily the waterline, this is not the same as the STIX variable hCE which is measured from the waterline, positive up). Hull length as defined by ISO 8666. This may be either specified or calculated by Hydromax. Hydromax calculates this parameter as the overall length of the vessel (all hull surfaces) in the upright, zero trim condition. Hull beam as defined by ISO 8666. This may be either specified or calculated by Hydromax. Hydromax calculates this parameter as the overall beam of the vessel (all hull surfaces) in the upright, zero trim condition.

Units

length2

length

length

length

Chapter 4 Stability Criteria

Option LWL, length waterline

BWL, beam waterline

height of immersed profile area centroid

Shall be greater than / Shall not be less than

Description Hull waterline length in the current load condition as defined by ISO 8666. This may be either specified or calculated by Hydromax. Hydromax calculates this parameter as the waterline length of the vessel (all hull surfaces) at zero heel and at the loadcase displacement and centre of gravity; if the analysis is carried out free to trim, the waterline of the trimmed vessel is used. Hull waterline beam in the current load condition as defined by ISO 8666. This may be either specified or calculated by Hydromax. Hydromax calculates this parameter as the waterline beam of the vessel (all hull surfaces) at zero heel and at the loadcase displacement and centre of gravity; if the analysis is carried out free to trim, the waterline of the trimmed vessel is used. Height of centre of the lateral projected immersed area of the hull from model’s vertical datum (not necessarily the waterline, this is not the same as the STIX variable hLP ); may be specified or calculated by Hydromax. Hydromax calculates this parameter at zero heel and at the loadcase displacement and centre of gravity; if the analysis is carried out free to trim, the waterline of the trimmed vessel is used. Hydromax uses the numerical STIX rating value rather than the STIX design category.

Units length

length

length

Hydromax calculates the various factors and STIX rating according to ISO/FDIS 122172:2002(E). Note that a downflooding angle is required to calculate the STIX index. Hence, if no downflooding points are defined, or defined downflooding points do not immerse within the selected heel angle range, the angle of downflooding is taken to be the largest heel angle tested. This affects the calculation of the Wind Moment and Downflooding factors.

Page 189

Chapter 4 Stability Criteria

Specific stability criteria A number of criteria files containing criteria for specific codes are supplied with Hydromax. These may be found in the “HMSpecificCriteria” folder. Most specific criteria are locked; those that are not locked require your ship design data to be input.

ISO 12217: Small craft – stability and buoyancy assessment and categorisation. This section gives some details on implementing the ISO 12217 stability criteria in Hydromax. Part 1: Non-sailing boats of hull length greater than or equal to 6m

In many cases the user must determine the required pass value for the criteria, which depends on the category and length of vessel being tested. In most cases the default required value would exceed the worst case. 6.1.2: Downflooding height Minimum freeboard to downflooding points must be determined from Figures 2 and 3 (Section 6.1.2) and entered into the required value field; the default value is set at 1.42m which is slightly greater than the height required for a category A vessel of 24m in length. 6.1.3: Downflooding angle Must be greater than a certain value as determined according to the design category; see Tables 3 and 4 (Sections 6.1.3, 6.2). The default value is set to 49.7 6.2: Offset-load test There are several ways of evaluating this criterion: 1. Define a heeling arm and calculate the intersection of the heeling arm with the GZ curve to determine the angle of equilibrium. 2. Specify a loadcase with the offset load specified and carry out an equilibrium analysis. Verify that the angle of equilibrium does not exceed the maximum permissible value. An additional requirement in this section is that a specified freeboard must be exceeded. 6.3: Resistance to wind and waves Determine the windage area and lever and enter them in the appropriate fields in the criterion. Also determine the required wind speed and roll-back angle (depending on the design category) and enter these values. In Hydromax, there is no option for placing the height, H, of the centre of lateral resistance at the bottom of the vessel, so this must be specified manually (it is measured from the model zero point, positive upwards). 6.3.3: Resistance to waves This criterion comprises two parts, one to check that the righting moment is sufficient and a second to determine whether the righting lever is sufficient. Page 190

Chapter 4 Stability Criteria

6.4: Heel due to wind action Determine the parameters required for calculation of the wind heeling moment as per 6.3, but note the different wind speeds to be used. Determine the limiting heel angle from Table 4 (Sections 6.2) Part 2: Sailing boats of hull length greater than or equal to 6m

6.2.2: Downflooding height Minimum freeboard to downflooding points must be determined from Figure 2 (Section 6.2.2) and entered into the required value field, the default value is set at 1.42m which is slightly greater than the height required for a category A vessel of 24m in length. 6.2.3: Downflooding angle Must be greater than a certain value as determined according to the design category, see Tables 3 (Sections 6.2.3). The default value is set to 40 6.3: Angle of vanishing stability Determine the required angle of vanishing stability which depends on design category and vessel displacement. The default value is 130. 6.4: Stability index (STIX) Determine the required STIX value depending on the design category, see Table 5 (Section 6.4.9). Also specify the sail area and vertical position of the sail area centroid and enter these values in the appropriate fields in the criterion. If desired you can specify the other values or let Hydromax calculate them for you. 6.5: Knockdown-recovery test The test can be approximated by examining the angle of vanishing stability in the flooded condition. If the flooded vessel has positive GZ at the knockdown angle, it should self right. 6.6.6: Wind stiffness test Determine the wind heeling moment as defined in 6.6.6 for the wind speed of interest (Table 6, Section 6.6.7). Convert this to a heeling lever. Calculate the GZ curve with the crew seated to windward, this criterion will then look at the angle of equilibrium of the vessel under the applied wind heeling arm. Part 3: Boats of hull length less than 6m

These criteria are evaluated after an equilibrium analysis under the specified loading condition. Non-Sailing Boats: 6.2.2: Downflooding-height tests Determine the required downflooding height and specify the appropriate loading condition. The criterion is evaluated after an equilibrium analysis. 6.3: Offset-load test This criterion is most effectively evaluated by performing an equilibrium analysis with the required offset loading condition Sailing Boats: Page 191

Chapter 4 Stability Criteria

7.2: Downflooding height Minimum freeboard to downflooding points must be determined from Figure 2 (Section 6.2.2) and entered into the required value field, the default value is set at 1.42m which is slightly greater than the height required for a category A vessel of 24m in length. 7.5: Knockdown-recovery test The test can be approximated by examining the angle of vanishing stability in the flooded condition. If the flooded vessel has positive GZ at the knockdown angle, it should self right. 7.6.6: Wind stiffness test Determine the wind heeling moment as defined in 6.6.6 for the wind speed of interest (Table 6, Section 6.6.7). Convert this to a heeling lever. Calculate the GZ curve with the crew seated to windward, this criterion will then look at the angle of equilibrium of the vessel under the applied wind heeling arm.

Page 192

Chapter 5 Hydromax Reference

Chapter 5 Hydromax Reference This chapter contains brief descriptions of the tools available in Hydromax: • Windows • Toolbars • Menus

Page 193

Chapter 5 Hydromax Reference

Windows Hydromax uses a range of graphical, tabular, graph and report windows. • • • • • • •

View Window Loadcase Window Damage Window Input Window Results Window Graph Window Report Window

View Window The View window displays the hull, frame of reference, immersed sections of the hull and any compartments, and the centroids of gravity, buoyancy, and flotation. These positions are represented by: cb cg cf

centre of buoyancy centre of gravity centre of flotation

You can choose which type of view is displayed by selecting from the Window menu or the View toolbar. The Zoom, Shrink, Pan and Home View commands from the View menu may be used and work in exactly the same way as in Maxsurf. If a Perspective view is shown, you may also use the Pitch, Roll and Yaw indicators to change the angle of view. Please refer to the Maxsurf manual if you are unfamiliar with these functions. You may set the visibility of the various display elements by using the Visibility command from the Display menu. Two sets of visibility flags are maintained, one is used for all analyses other than tank calibration and the other is used for when the tank calibration analysis is selected. If a view window is visible when an analysis is being carried out, it will display the hull shape using the correct heel trim and immersion for the current iteration of the analysis. After an analysis, the Select View from Data command in the Display menu may be used to move the hull to a selected position from the Results window. The view of the tanks, compartments and non-buoyant volumes can be toggled between an outline view and a view of the sections. Perspective view

In the perspective view, the model may be rendered.

Page 194

Chapter 5 Hydromax Reference

The rendered view also enables tanks and compartments to be more easily visualised, especially when the hull shell is made transparent.

The rendering options are to be found in the Display menu, with further lighting options in the Render toolbar. Please refer to the Maxsurf manual for more information on the different rendering options available in perspective view. Note: Fastest performance will be achieved by reducing the amount of redrawing that is required from Hydromax. For this reason, it is best to turn off sections, and especially waterlines, when performing an analysis. You may then turn them on again after the analysis has completed. For fastest performance, e.g. when running in Batch mode, minimise the Hydromax window so that no redrawing occurs. .

Page 195

Chapter 5 Hydromax Reference

Loadcase Window In the Loadcase window a spreadsheet table of all loads and tanks is displayed.

Using the tabs on the bottom of the window allow you to quickly browse through the different loadcases. Hydromax allows you to improve the presentation of the Load Case window by adding blank, heading or sub-total lines in the table. For more information see Loadcase

Damage Window The Damage window is used to specify which tanks and compartments are flooded in each damage case. There is always an Intact case, which may not be edited, this is the default condition. If flooded volumes are required in the intact case they should be defined as non-buoyant volumes.

Input Window The Input window contains tables where the additional Hydromax design data is entered. The tables in the Input window contain the: • Compartment Definition • Sounding Pipes Page 196

Chapter 5 Hydromax Reference • Key Points • Margin Line Points • Modulus Points

The input window contains tabs on the bottom that allow you to quickly browse through the different input tables. Compartment Definition

This table can be used to define the tanks and compartments in the Hydromax models. For more information see Modelling Compartments on page 38 in the Analysis Input section. Sounding Pipes

This table is used to define the tank sounding pipes and calibration intervals. Default values are provided but these may be edited if necessary. Key Points

There are several types of Key Points: • Down Flooding points • Potential Down flooding points • Embarkation points • Immersion Points

Only downflooding points are used in determining the downflooding angle, which is used in criteria evaluation. The other types of points have their freeboard measured but are not used during criteria evaluation and are for information only. Margin Line Points

The margin line is used in a number of the criteria. Hydromax automatically calculates the position of the margin line 76mm below the deck edge when the hull is first read in. If necessary, the points on the margin line may be edited manually in the Margin Line Points window (the deck edge is automatically updated so that it is kept 76mm above the margin line). Points may be added or deleted as required using the procedure described for the downflooding points. Modulus Points

This table is used to define the allowable limits for shear force and bending moment during the longitudinal strength calculations.

Page 197

Chapter 5 Hydromax Reference

Results Window The Results window contains ten tables, one for each of the different analysis types plus a criteria results and key points results tables. The currently selected results table will change to reflect the current analysis mode, when switching mode. Note that results are never invalidated if analysis options are modified – it is up to the user to ensure that the results are recalculated as necessary. Data Format

It is possible to configure Hydromax so that only the results that you wish to see are displayed. To do this, choose Data Format from the Display menu. You may change the table to view the results from the last analysis of each type.

A dialog similar to the one above will appear. Items that are selected with a tick will be displayed in the Results window and on any printed output. Items that are not selected are still calculated during the analysis cycle, but are not displayed. You may change the display format at any time after the analysis without having to redo the calculations. The LCB and LCF can be displayed in the Results windows relative to the Zero Point specified or from the Amidships location. To choose either format, select Data Format from the Display menu and click on either the From Amidships or the From Zero Pt items. Data Layout

Analysis data can be formatted vertically or horizontally to fit better on the screen or the printed page. For example, with Upright Hydrostatics, the data can be formatted so that each draft has a column of results, or so that each draft is on a separate row.

Page 198

Chapter 5 Hydromax Reference

To change the format, select Data Format from the Display menu, and select either the horizontal or vertical layout button. The data for each of the analysis types is stored in a separate table in the Results window. Changing the current analysis mode will change the current table in the Results window. Two additional tables are available in the Results window. These are: Stability Criteria and Key Point Data (downflooding angles and freeboards). Key Points Data Result Window

Key points data is calculated for Large Angle Stability, Equilibrium and Specified condition Analysis. The DF angle column is only visible when the analysis mode is set to Large Angle Stability and the Freeboard column is only displayed when the analysis mode is set to Equilibrium or Specified condition.

Page 199

Chapter 5 Hydromax Reference Stability Criteria Result Window

If stability criteria are turned on in the analysis menu, they will be evaluated during Large Angle Stability, Limiting KG and Equilibrium analyses. The results of the criteria evaluation are presented in this table after Large Angle Stability and Equilibrium analyses. The results may be displayed in compact format:

Alternatively, the results can be displayed in verbose format, where all the intermediate calculations are shown, by selecting the desired format in the Display | Data format dialog.

Graph Window The Graph window displays graphs, which show the results of the current analysis.

Page 200

Chapter 5 Hydromax Reference Graph type

Hydromax can graph many types of data depending on the type of analysis being performed. These graphs include Upright Hydrostatics, Curves of Form, GZ curves, Longitudinal Strength and Tank Capacities. These can all be displayed via the Graph item in the Windows menu. In some cases, such as hydrostatics, multiple sets of data are plotted on the same graph. Interpolating Graph Data

To display an interpolated value from one of the curves, use the mouse to click anywhere on the curve. The data in the lower left corner of the window will change to display the curve name and co-ordinates of the mouse on the curve. Click anywhere on the dashed line and drag it with the mouse; as you move the cursor the interpolated values will be displayed.

Note: In case multiple curves are plotted in the same graph you can switch between the curves by clicking on them. Hydromax will ignore the exact position you click on the curve to allow reading all related interpolated values along the black dashed line. GZ Graph

The GZ value, Area and corresponding heel angle can be measured by using the slider; the slider position is displayed at the bottom of the Graph window. The area is integrated from zero heel angle to the location of the graph slider.

Page 201

Chapter 5 Hydromax Reference

Note: Because the horizontal axis scale is always in degrees, the area is always given in units of length.degrees and cannot be displayed in units of length.radians.

Note The lower integration limit is always zero (irrespective of the equilibrium angle). Thus if you require the area between two limits, you must subtract the area at the lower limit from the area at the higher limit. Curve fitting for GZ graph

A parametric cubic spline is used to fit a smooth curve through the calculated GZ data at the specified heel angles. This ensures that the fitted line goes exactly through the calculated GZ points. The curve fit will only be performed if all the heel angle intervals are less than or equal to 10˚. Graph data

The graphed data can be obtained by double clicking on the graph. Since the graph data contains more data points than most tables in the results window, this double click can be extremely helpful to export the analysis data to for example Excel fro further processing. Especially in the case of the sectional area curve, where there is no tabular data available. Also see: Copying Tables on page 105.

Page 202

Chapter 5 Hydromax Reference

Report Window Hydromax contains a Report window. This window is used to create a progressive summary of the analyses that have been carried out. This report can be edited via Cut, Copy and Paste; printed, saved to and recalled from a disk file. Since Microsoft Office programs such as Word and Excel are more powerful formatting programs, it is generally recommended that you only use the Report window to accumulate results and that you do not attempt any formatting of the report within Hydromax. Once you have completed the analysis simply copy and paste the contents of the Report window into Microsoft Word and proceed with the formatting there. It is usually more convenient to copy and paste tables and graphs into Word and Excel directly from the Result and Graph windows, instead of from the Report window. Formatting can be done in the Report window. However it is recommended that the report window be used only to accumulate the results. Once all the results have been gathered in the report window, these should be saved and opened in a word processor such as Microsoft Word for formatting: • set the results tables up as you want them to appear in the report (the report uses the same column widths, fonts etc.); do the same for the graph widow;

• choose an appropriate paper size for the report (the tables will be split to fit this paper size, so choosing a wide paper size will prevent all but the widest tables from being split);

• copy and paste the Hydromax report into Microsoft word. Use the Format | Autoformat function in Word (with the default settings) to set the correct styles for the different levels of heading in the document, this will facilitate generating a table of contents and also allows you to re-format the various styles (or import a custom set of styles using the style organiser in Word).

Report files are loaded and saved in Rich Text Format (RTF), allowing you to load them directly into your favourite word processor for further editing. The Report window has it's own toolbar permanently attached to the view, as well as a ruler showing you tab stops, indentation and margin widths. Underneath all of this you have your actual editing area. Note that it is best to set up the desired page size, orientation and margins before starting any analyses. This way Hydromax will make best use of the page when inserting tables, graphs and text. Changing the page layout after data has been inserted will not reformat the tables etc. Hydromax will split most results tables so they fit the specified page set up. However, both Loadcase and Criteria results tables will not be split.

Page 203

Chapter 5 Hydromax Reference

The toolbar has a number of buttons that allow you to change either the current settings, or the section of text that is currently highlighted. The toolbar contains the following items: Font combo box Font Size combo box Bold Italic Underline Right/Left Justify Centre Justify Double Line Spacing Indent Margin Left Indent Margin Right Hanging Indent

Use this to change the current font Use this to change the current font size Use this to toggle the Bold style Use this to toggle the Italic style Use this to toggle the Underline style Use this to toggle Left/Right Justification Use this to toggle Centre Justification Use this to toggle Single/Double Line Spacing Indent the Left Margin Indent the Right Margin Indent the Hanging Indent

The Ruler comes in two formats, in metric and in inches - the format you have displayed on your screen depends on the current Dimension Units you have (use Units in the Display menu to change this). The format shown below is metric.

The Ruler allows you to set left, right, centre, and decimal tab stops. The tab stops are very useful for creating columns and tables. A paragraph can have as many as 20 tab positions. The 'left' tab stop indicates where the text following the tab character will start. To create a left tab stop, click the left mouse button at the specified location on the ruler. The left tab stop is indicated on the ruler by an arrow with a tail toward the right.

Page 204

Chapter 5 Hydromax Reference

The 'right' tab stop aligns the text at the current tab stop such that the text ends at the tab marker. To create a right tab stop, click the right mouse button at the specified location on the ruler. The right tab stop is indicated on the ruler by an arrow with a tail toward the left. The 'centre' tab stop centres the text at the current tab position. To create a centre tab stop, hold the shift key and click the left mouse button at the specified location on the ruler. The centre tab stop is indicated on the ruler by a straight arrow. The 'decimal' tab stop aligns the text at the decimal point. To create a decimal tab stop, hold the shift key and click the right mouse button at the specified location on the ruler. The decimal tab stop is indicated on the ruler by a dot under a straight arrow. To move a tab position using the mouse, simply click the left mouse button on the tab symbol on the ruler. While the mouse button is depressed, drag the tab to the desired location and release the mouse button. To clear a tab position, simply click on the desired tab marker and drag it off the ruler. Normally, a tab command is applicable to every line of the current paragraph. However, if you highlight a block of text before initiating a tab command, the tab command is then applicable to all the lines in the highlighted block of text. Keyboard Support For Reports

In addition to menu support, there are also several useful keystrokes that are available while editing the report. These are listed below for convenience: Ctrl+B Toggle Bold on/off Ctrl+U Toggle Underline on/off Ctrl+PageUp Ctrl+PageDown

Position at the top of the report Position at the bottom of the report

Ctrl+Enter

Insert a page break

Opening and Saving the Report

The report can be saved to a file or read in from a file using the Save and Open Menu commands with the report window highlighted. This is useful if you wish to append an analysis to a report that had been calculated at some time in the past. (Load in the old report, perform the analyses; the new results will be appended to the end of the report which may then be resaved). Pasting images into the report

Sometimes, it is desirable to insert schematic images of the vessel into the report. This is very easily done, by copying an image from one of the design views and then pasting it into the report at the desired location. Ensure that the colors selected will be easily visible in the white background of the report view. Depending on which Microsoft operating system you are using (notably Win98), the image may not maintain its aspect ratio and may be pasted into the report as a square. To overcome this problem, paste the image into Microsoft Word first, then copy it from Word back into the Hydromax report window.

Page 205

Chapter 5 Hydromax Reference

Changing the scale will affect the size of the image, and hence the thickness of the lines. For example, copying the image at 1:100 instead of 1:50 will effectively double the thickness of the lines if you make the images the same size in the report. Remember that you can change the font size in the design window.

hatch 1 Tank 3 cg AP

hatch 2

cg Tank 12 cf TankTank 4 cg cg cb zerocg pt. MS

hatch 3 Baseline FP

Image copied at 1:500 (Word image displayed at 200%) hatch 1

Tank 3 cg

AP

hatch 2 cfcg Tank1 2 Tank Tank 4 cgcg cb cg zero pt. MS

Image copied at 1:250 (Word image displayed at 100%)

Page 206

hatch 3

Baseline

FP

Chapter 5 Hydromax Reference

Toolbars Hydromax has a number of icons arranged in toolbars to speed up access to some commonly used functions. You can hold your mouse over an icon to reveal a pop-up tip of what the icon does.

File Toolbar

The File toolbar contains icons that execute the following commands: New - Open - Save - Cut - Copy - Paste - Print Edit Toolbar

The Edit toolbar contains icons that execute the following commands: Add Row - Delete Row View Toolbar

The View toolbar contains icons that execute the following commands: Zoom - Shrink - Pan - Home View Analysis Toolbar

The Analysis toolbar contains icons for selecting the current analysis, loadcase and damage case: Analysis Type - Current Loadcase - Current Damage Case

The Analysis toolbar also contains icons that execute the following commands: Criteria (dialog) | Start Analysis - Pause Analysis - Resume Analysis | Update Tank Values in Loadcase The “Update Tank Values in Loadcase” is exactly the same as the menu command for “Recalculate Tanks and Compartments on page 214.

Page 207

Chapter 5 Hydromax Reference Window Toolbar

Perspective – Plan – Profile – Body Plan | Loadcase – Damage Case | Compartment – Downflooding – Margin Line – Modulus | Results for Current Analysis – Criteria Results – Key Point Results | Graph – Report Visibility Toolbar

The Visibility toolbar contains icons that show or hide various items in the graphical views: Sections – Datum Waterline – Waterlines | Key Points – Margin Line | Tanks – Damaged Tanks – Compartments & NBVs – Damaged Compart. & NBV*s – Tank/Compart./NBV Names – Tank/Compart./NBV Sections * NBV = Non Buoyant Volume Render Toolbar

Render – Render transparent – Toggle custom light 1 – Toggle custom light 2 – Toggle custom light 3 – Toggle custom light 4 – Customise light settings

Page 208

Chapter 5 Hydromax Reference

Menus The following section describes all of the menu commands available in the Hydromax program. • • • • • • • •

File Menu Edit Menu View Menu Analysis Menu Case Menu Display Menu Window Menu Help Menu

File Menu The File menu contains commands for opening and saving files and printing. New

Creates a new table for whichever input table is frontmost, e.g: when the Loadcase Condition is the frontmost window, the New command will create a new loading condition. When the Compartment Definition window is frontmost, New creates a new compartment definition. Open

When no design is open, selecting the Open command will show a dialog box with a list of available Maxsurf designs. Select the design you wish to open, click the Open button. The requested design will be read in and its hull shape calculated for use in Hydromax. If a design is already open, the Open command will open whichever file corresponds to the frontmost input window. Close

The Close command will delete the data in the frontmost window. Hydromax will ask whether you wish to save any changes. Selecting Close when one of the design view windows is frontmost will close the current Maxsurf design. Save

Selecting Save will save the contents of the frontmost window to a file on the disk. Save As

Selecting Save As performs the same function as save but allows you to specify a new filename preventing the original file from being overwritten.

Page 209

Chapter 5 Hydromax Reference Export

Selecting Export enables you to export a Hydromax file as a variety of different file formats such as DXF or IGES. DXF exports sections as closed poly-lines. In addition, each tank, compartment and non-buoyant volume is exported on a separate layer (the layer name being the same as the compartment name, so it is important to have unique compartment names) Also allows users to export Hydromax files that are compatible with earlier versions of Hydromax. Page Setup

The Page Setup dialog allows you to change page size and orientation for printing. Print

The Print command allows you to print the contents of the frontmost window on the screen. Exit

Exit will close Hydromax and all the data windows. If you have any data or results, which have not been saved to disk, Hydromax will ask you if you wish to save them before quitting.

Edit Menu The Edit menu contains commands for working with tables. Undo

Undo may be used with desk accessories, but cannot be used on Hydromax drawing windows or data windows. Cut

Cut may be used in the Report window but cannot be used on Hydromax drawing or data windows. Copy

The Copy command allows you to copy data from any of the windows, including the design view, input tables, results tables and graph window. Paste

Choose the Paste command to Paste data into the Loadcase window or other input tables, or the Report window. Paste cannot be used in the View, Graph or Results windows. Select All

Selects the entire Report. Fill Down

Copies text in a table down a column like a spreadsheet. Table

Performs operations on Hydromax's Report window.

Page 210

Chapter 5 Hydromax Reference

Insert New Table Create a new table in the Report. Insert Row Insert a new row into the current table in the Report. Split Cell Split the currently selected cell into two separate cells in a table in the Report. Merge Cells Merge the selected cells in a table into a single cell in the Report. Delete Cells Delete current cell, column or row or a range of cells, columns or rows in the Report. Row Positioning Set Justification for the current table row or an entire table in the Report. Cell Border Set Cell Border Width for a single cell or range of cells in the Report. Cell Shading Set Cell Shading Percentage for a single cell or a range of cells in the Report. Show Grid Toggle table grid lines in the Report. Add

The Add command is used to add an entry to the input tables. Delete

The Delete command will delete rows from the input tables. If no rows are selected, the last row in the window will be deleted, otherwise all selected rows will be deleted. Add Surface Areas

This command automatically adds the surface areas and centres of gravity of all hull surfaces into the current loading condition. This is useful for estimating the initial weight of hull plating. Error Values

See Error Values on page 95.

View Menu The View menu contains commands for controlling the views in the graphics windows. Zoom

The Zoom function allows you to examine the contents of the design view windows in detail by enlarging the selected area to fill the screen. Shrink

Choosing Shrink will reduce the size of the displayed image in the design view windows by a factor of two. Pan

Choosing Pan allows you to move the image around within the View window.

Page 211

Chapter 5 Hydromax Reference Home View

Choosing Home View will set the image back to its Home View size. Set Home View

Choosing Set Home View allows you to set the Home View in the View window. To set the Home View, use Zoom, Shrink, and Pan to arrange the view, then select Set Home View from the View menu. Colour

The Colour function allows you to set the colour of lines, labels, and graphs. Remember to always be careful when using colour. It is very easy to get carried away with bright colours and end up with a garish display that is uncomfortable to work with. In general it is best to use a neutral background such as mid grey or dull blue and use lighter or darker shades of a colour rather than fully saturated hues. From the scrollable list, select the item whose colour you wish to change. The item’s current colour will be displayed on the left of the dialog. To change the colour click in the box and select a new colour from the palette. Font

Font command allows you to set the size and style of text.

The text style chosen will affect the display and printing of all text in the Report, Loadcase, Graph, Curve of Areas, and Results windows. Toolbar

Allows you to turn the Toolbars on and off. Status Bar

Allows you to turn the Status Bar on and off at the bottom of the screen.

Analysis Menu The Analysis menu can be used to change the current analysis mode. It also contains commands to set the input data and analysis settings and environment options required for the current analysis. Page 212

Chapter 5 Hydromax Reference

Note: It is good practice when preparing to run analysis to work down the Analysis menu. Heel

Selecting Heel allows you to specify the three ranges of heel angles that you wish Hydromax to step through. Separate ranges may be set for Large Angle Stability, KN and Limiting KG analyses. Trim

Free trimming is activated by setting the Free Trim box, otherwise all calculations are performed with fixed specified trim. Draft

The range of drafts used for the analysis of upright hydrostatics can be set using this command. Displacement

The range of displacements used for the analysis of KN values, Limiting KG and Floodable Length can be set using this command. Specified Condition

Allows you to specify Heel, Trim, CG, Displacement and Draft for the Specified Condition analysis. Permeability

The range of permeabilities used for the Floodable Length analysis are set using this command.

Page 213

Chapter 5 Hydromax Reference Fluids

Allows you to specify whether to use Corrected VCG method or Simulate Fluid Movement method when analysing the fluid contained in tanks. Also see: Free surface correction on page 37. Density

This command allows you to set the density of fluids used in the analysis. Waveform

The Waveform command allows you to perform analysis for a flat waterplane or sinusoidal or trochoidal waveforms. Hog and Sag

Allows you to define the amount of hog or sag to be applied to the hull when calculating the vessel’s hydrostatics. Criteria

The criteria menu item will bring up the criteria dialog. This allows you to specify which criteria will be checked during the analysis. See Criteria Overview on page 112. When the floodable length analysis is selected, the criteria command will bring up a Floodable Length Criteria dialog with criteria that only apply to floodable length analysis.

Grounding

Specifies grounding on one or two points of variable length. Update Loadcase

Checks for changed tanks and makes sure that any tanks and compartments that have not been formed are correctly calculated. It then updates the loadcase with the correct capacities and free surface moments for the tanks. Also see: Tank Loads on page 37 Analysis Toolbar on page 207 Recalculate Tanks and Compartments

Forces all tanks and compartments to be re-formed from their initial definition. This command also updates the loadcase.

Page 214

Chapter 5 Hydromax Reference

If any of the tank boundaries are made up from boundary surfaces, it is better to use “Recalculate Hull Sections” after re-opening the Maxsurf model to make sure the latest internal structure surfaces are being used as well. Recalculate Hull Sections

Deletes all existing hull, tank and compartment sections and recalculates them from the hull surface data and compartment definition. This is particularly useful if the underlying Maxsurf model has been modified, if you wish to recalculate at a different precision, or if you wish to modify whether skin thickness or trimming options are applied. Note: To be able to update the Hydromax model to changes made in Maxsurf, the Maxsurf model first has to be re-loaded into Hydromax. Follow this procedure to retain all Hydromax data and update the section lines: - Save the model in Hydromax - Close the model in Hydromax - Save the model in Maxsurf - Open the model in Hydromax, using “Read sections from file”. This ensures that the Loadcases, compartment definition etc. remain part of the Hydromax design file. - Use the “Recalculate Hull Sections” command from the analysis menu - Specify the calculation options in the Section Calculations Options dialog - Press Ok See Updating the Hydromax Model on page 25. Snap Margin Line to Hull

Project all of the margin line points horizontally onto the hull surface, ensuring that the margin line follows the hull shape precisely. Also see: Margin Line Points on page 60. Set Analysis Type

Choose the analysis type you wish to use from the sub-menu. Start Analysis

Selecting Start Analysis causes Hydromax to start performing the specified analysis. The analysis may be halted at any time by choosing Stop Analysis from this menu, also. Resume Analysis

If you have halted analysis by choosing Stop Analysis, Resume Analysis may be used to restart the calculation from the point where it was interrupted. Stop Analysis

This command halts the analysis at the current iteration. Note that the analysis may not have been completed and in the case of large angle stability, equilibrium condition and KN values, any data displayed for the final iteration may be incorrect.

Page 215

Chapter 5 Hydromax Reference Batch processing

Hydromax will run Large Angle Stability and Equilibrium analyses for all combinations of load and damage cases using the batch processing command. Results are written to a tab delimited text file which may be specified by the user at the start of the analysis. The aim of the batch processing function is to: a) Provide the user with a simple and consistent way of carrying out Large Angle Stability and Equilibrium analyses on a large number of load and damage cases; b) Facilitate export of the data from Hydromax and import into MS Excel for post processing and report generation; and to c) provide all relevant results and the data required to be able to reproduce the runs, i.e.: analysis parameters, file name etc. Analysis parameters such as trim, heel angles etc. are set in the normal way. Any criteria which have been set are evaluated at the end of each analysis and the results of these are also output to the text file. Because the analyses are simply carried out one after the other, it is not possible to go back to the results for a specific analysis from within Hydromax; only the results of the final analysis will be stored in Hydromax. Once the loadcases, damage cases, key points, criteria and analysis parameters for the Large Angle Stability and Equilibrium analyses have been set up, the Batch Analysis is started with the Start Batch Analysis command in the Analysis menu. Before analysis starts, you will be prompted to enter the name and location of the file where Hydromax will write the results of the batch analysis. Once the analysis is complete, this tab delimited text file may be imported directly into MS Excel for further processing. Note: Under most operating systems, minimising Hydromax can reduce the time required to perform the calculations. This is because time consuming redrawing of the design windows, graphs and tables is avoided.

Case Menu The case menu is used to add, delete and rename damage cases. Add Damage Case

Adds a damage case before the currently selected damage case, in the Damage Case window. If either the intact case or none is selected, the new damage case will be added to the end of the list. Delete Damage Case

Deletes the current damage case(s) in the Damage Case window. Edit Damage Case

Allows the name of the selected damage case, other than the intact case, to be edited.

Page 216

Chapter 5 Hydromax Reference Max. Number of Loadcases

Allows the user to set the number of loadcases that can be defined. A maximum of 25 loadcases may be specified.

Display Menu The Display menu contains commands for controlling the data, which are displayed in the graphics and other windows. Data Format

Data Format allows you to choose which stability data are tabulated. A dialog box allows you to choose from a range of stability variables. Coefficients

In Hydromax you may choose between the length between perpendiculars and the waterline length for the calculation of Block, Prismatic and Waterplane Area Coefficients. Select Coefficients from the Display menu:

Units

The units used may be specified using the Units command. In addition to the length and mass units classes, units for speed (used in wind heeling and heeling due to high-speed turn etc. criteria) and the angular units to be used for areas under GZ curves, may also be set. The angular units for measuring heel and trim angles are always degrees.

Page 217

Chapter 5 Hydromax Reference Visibility

The visibility of tanks, compartments, labels, hull contours, and other items in the design view may be set by using this dialog.

Frame of Reference

If the position(s) of the Baseline and/or Perpendiculars need to be changed from those defined in the Maxsurf model, they may be changed using the Frame of Reference command. It is highly recommended that the correct frame of reference be set in Maxsurf prior to loading the design into Hydromax. This will ensure that a consistent frame of reference is used in all the programs. See: Frame of Reference on page 20. Zero Point

This function sets the longitudinal and vertical reference point for all measurements, including the centre of gravity. It is highly recommended that the correct zero point be set in Maxsurf prior to loading the design into Hydromax. This will ensure that a consistent zero point is used in all the programs. Show Single Hull Section in Body Plan

Selecting the Show Single Hull Section item from the Display menu will change the display in the Body Plan window to show only one section through the hull, as well as a control box, similar to the one in Maxsurf, in the top right corner of the window. The section being displayed can be chosen by clicking on the section indicators at the top of the control box. Alternatively, the section chosen can be changed by depressing the left or right cursor keys on your keyboard. This allows you to rapidly step through the hull sections from bow to stern. Also see: Show Single Hull Section on page 29

Page 218

Chapter 5 Hydromax Reference Select View from Data

This function may be used to synchronise the display in the Design View window with one of the sets of data in Results window. The view may be set from any of the results from Upright Hydrostatics, Large Angle Stability or Equilibrium analyses. Simply highlight the column or row that corresponds to the condition you wish to view and select “Select View From Data”; the Design View will change to match the condition in the selected row or column in the Results window. Render

When the Perspective window is the current view for the model the Render option may be toggled on and off to render the surfaces. Render Transparent

When the Perspective window is the current view for the model the Render Transparent option may be toggled on and off. Render Transparent makes the hull surfaces of the model semi transparent so that the rendered compartments within the model may be viewed. Animate

Selecting Animate will animate the stability sequence in the design View window, through the range of heel angles specified. You may set the initial viewing position in the Perspective View window using the Pitch, Roll and Yaw indicators. When Hydromax has finished calculating the frames the sequence may be replayed by moving the mouse from side to side. Clicking the mouse button will terminate the animation. If animation is chosen after an Equilibrium Analysis has been performed in waves, the animation will automatically cycle through the full range of wave phases, giving a simple visual simulation of the motion of the hull through a wave pattern.

Window Menu For the items in this menu, each represents a Hydromax window. Selecting the item brings the appropriate window to the front. Cascade

Displays all the Windows behind the active Windows. Tile Horizontal

Layout all visible windows across the screen. Tile Vertical

Layout all visible windows down the screen. Arrange Icons

Rearranges the icons of any iconised window so that they are collected together at the bottom of the Maxsurf program window. View Direction

Select the desired view direction from the sub-menu. The selected design window will then be brought to the front.

Page 219

Chapter 5 Hydromax Reference Loadcase

Brings the Loadcase window to the front. The Loadcase window allows you to enter a series of component weights, together with their longitudinal and vertical distances from the zero point. These inputs are used to calculate the total Displacement and Centre of Gravity for Stability, KN and Equilibrium analysis. Input

Choose from the Input item to bring the desired Input window to the front and display the Compartment Definition, Key Points, Margin Line Points or Modulus table. Results

Choose from the Results item to bring the desired Results window to the front and display the desired table. Graph

Brings the selected Graph window to the front. The Graph window displays a number of different graphs, depending on which analysis mode is currently active.

Help Menu Provides access to Hydromax Help. Hydromax Help

Invokes Hydromax Help. About Hydromax

Displays information about the current version of Hydromax you are using.

Page 220

Appendix A

Appendix A Calculation of Form Parameters This Appendix explains how the calculation of form parameters (CB, CP, AM, etc.) is achieved in Hydromax, and investigates why differences with other hydrostatics packages may occur.

Definition and calculation of form parameters Below is a summary of the definitions of basic vessel particulars and form parameters used in Hydromax. Nomenclature

Amax AWP BOA BWL B b LOA LCB LCG LWL LBP L T0 T t ∇

Maximum immersed cross-sectional area to waterline under investigation Area of waterplane at the waterline under investigation Overall beam of whole vessel (above and below waterline) Maximum waterline beam at design waterline Maximum beam of waterline under investigation Waterline beam of station under investigation Length overall Longitudinal Centre of Buoyancy Longitudinal Centre of Gravity Length of design waterline Length between perpendiculars length of waterline under investigation Draft from some arbitrary baseline (normally the lowest point on the design) Maximum immersed depth (draft) of hull Draft (immersed depth) of station under investigation Immersed volume of displacement at waterline under investigation

Length

The design waterline or DWL is a waterline near which the fully loaded design is intended to float under normal circumstances. The forward perpendicular is normally defined as the intersection of the DWL with the bow. The after perpendicular is normally defined as the position of the rudder post, or possibly the transom. Several lengths may be defined: the LBP is the length between perpendiculars, this may be different from the length of the DWL (LWL) and in general, will also be different from the LOA (overall length). In some cases, particularly for resistance prediction purposes, it may be more appropriate to define an effective length of the underwater body, features such as bulbous bows and overhangs can make the LBP, LWL and LOA quite different. In addition, for calculations at drafts other than the DWL, it may be appropriate to use the actual waterline length at that draft (L).

Page 221

Appendix A

Some of the more common lengths that may be used to characterise a vessel.

In Hydromax you may choose between the length between perpendiculars and the waterline length for the calculation of Block, Prismatic and Waterplane Area Coefficients. Select Coefficients from the Display menu:

Beam

It is normal to use the maximum waterline beam for calculation of coefficients, and this may be of the DWL or the waterline under consideration. However, there may be times when it is appropriate to use the maximum immersed beam (e.g. submarine, vessel with tumble-home or blisters). For the calculation of section area coefficients it is normal practice to use the beam and draft of the section in question.

Vessel with tumble-home

Catamarans and other multihull vessels pose another difficulty. In some cases the overall beam is of importance, in others, the beam of the individual hulls may be required. Hydromax uses the total waterline beam of immersed portions of the section for calculation of block coefficient and other form parameters. For the case of a monohull this will be the normal waterline beam. For catamarans this will be twice the demihull beam (remember that the total displaced volume is used and hence the block coefficient is the same as that of a single demihull). For the section shown below, the beam used would be the sum of B1, B2 and B3.

Page 222

Appendix A

Multihull beams

Draft

The draft is normally specified from a nominal datum. Normally this datum is the lowest part of the upright hull. However, for vessels with raked keel lines or yachts, the datum may be elsewhere. In Hydromax drafts are defined from the datum line. However, there are also occasions when the immersed depth of the section is a more relevant measure of draft, this is often the case when form parameters are calculated. Hydromax uses the depths that stations extend below the waterline for calculation of form coefficients. For calculations of block coefficient, the greatest immersed section depth is used; for calculations of section area coefficients, the immersed depth of the section in question is used. Both depths are measured in upright position.

Draft measurements

Draft measurement at heel angle When the vessel is heeled, the draft is measured through the intersection of the upright waterline and the centreline, perpendicular to the heeled waterline (see figure below).

Midship Section

It is current usual practice to define the midship section as midway between the perpendiculars, however for some vessels it is defined as the midpoint of the DWL. For vessels with no parallel mid-body, the section with greatest cross-sectional area may also be of particular interest. Page 223

Appendix A

When comparing form coefficients such as CP and CM, remember that Hydromax uses the station with the maximum immersed cross-sectional area at the waterline under consideration. Block Coefficient

Principles of Naval Architecture defines the block coefficient as: "the ratio of the volume of displacement of the moulded form up to any waterline to the volume of a rectangular prism with length, breadth and depth equal to the length, breadth and mean draft of the ship at that waterline." However, the actual definitions of the length, beam and draft used vary between authorities. Length may be LBP, LWL or some effective length. The beam may be at amidships or the maximum moulded beam of the waterline; or may be defined according to another standard – this may be important for hulls with significant tumble-home or blisters below the waterline. Hydromax uses the length of the waterline under consideration, L, the maximum waterline beam of that waterline, B. The draft is the depth below the waterline of the deepest section, T. Note that B and T need not occur at the same longitudinal station.

CB =

∇ L ⋅ B ⋅T

Midship Section Coefficient

Principles of Naval Architecture defines the midship coefficient as: "The ratio of the immersed area of the midship station to that of a rectangle of breadth equal to moulded breadth and depth equal to moulded draft at amidships." It should be noted that, for sections that have significant tumble-home or blisters below the waterline, the midship section coefficient can be greater than unity. The midship section coefficient used by Hydromax, is calculated at the station with maximum cross-sectional area. The beam used is the waterline beam at this station, b, and the draft is the immersed depth of the station, t.

CM =

Amax b⋅t

Prismatic Coefficient

Principles of Naval Architecture defines the prismatic coefficient as: "The ratio between the volume of displacement and a prism whose length equals the length of the ship and whose cross-section equals the midship section area." Again the definition of midship section and vessel length depend on the standard being used. Hydromax uses the length of the waterline under investigation, L, and the maximum immersed cross-section area Amax.

CP =

Page 224

∇ L ⋅ Amax

Appendix A Waterplane Area Coefficient

Principles of Naval Architecture defines the waterplane area coefficient as: "The ratio between the area of the waterplane and the area of a circumscribing rectangle." Hydromax uses the length of the waterline, L, and the maximum beam of the waterline, B.

CWP =

AWP L⋅B

LCG and LCB

The LCG and LCG are calculated from either the Zero point or Amidships. This can be set in the column selection dialog in the display | data format menu.

The LCG and LCB are calculated in the frame of reference of the vessel. When the vessel is free to trim, the LCG and LCB will be at the same longitudinal position in the global coordinate system, but not in the frame of reference. Therefore a difference between the LCG and the LCB value will occur when the vessel is trimmed. This is explained in the figure below:

Page 225

Appendix A

Note: LCG and LCB are calculated in the vessels’ frame of reference and therefore will have different longitudinal positions when the vessel is trimmed then for when it is upright. This is the same for differences in TCG and TCB values due to heeling. Trim angle

The trim angle as defined by:

 Ta − T f    L pp  

θ = tan −1 

where: θ is the trim angle; Ta , Tf are the aft and forward drafts at the corresponding perpendiculars and LPP is the length between perpendiculars. Maximum deck inclination

The inclination angle is a combination of heel and trim angle. Hydromax calculates the steepest slope of the deck when the ship is trimmed and/or heeled. Deck camber and initial deck slope are not taken into account. For example:

Page 226

Appendix A

The Max deck inclination is the maximum slope of the deck when combining the trim and heel angle of the vessel, assuming the deck inclination is zero when the vessel is in upright position.

Immersion

The weight required to sink the model one unit-length below its current waterline. The unitlength can be either in cm or inch depending on your unit settings. MTc or MTi

The required moment to make the vessel trim one unit-length. That can be either cm or inch depending on your unit settings. RM at 1 deg

The righting Moment at 1 degree heel angle, calculated by

RM = Displ * GMt * sin(1)

Page 227

Appendix A

Potential for errors in hydrostatic calculations There are a number of potential sources of error when calculating the hydrostatic properties of immersed shapes. These mainly occur from the integration method used, and occur in both hand calculations, and most automatic calculations carried out by computers. Both methods use numerical integration techniques, which are normally either based on Simpson's rule or the Trapezium rule. As with all numerical integration schemes, the accuracy increases as the step size is reduced, hence computer calculations offer an enormous advantage compared with hand calculations, due to the increased speed and accuracy with which these calculations may be carried out. With hand calculations, it is normal to use perhaps 21 sections and perhaps 3-5 significant figures; with computer calculations, it is quite feasible to use 200 sections or more with 10s of significant figures. These effects are noted from comparing the results of different hydrostatics packages on the same hullform. In general, differences for basic parameters such as displacement etc. are under 0.5% (note that, in general, agreement of hand calculations to within 2% is considered good). Differences in derived form parameters may show considerable variation. However, this is primarily due to differences in the definitions used – see discussion above. The 0.5% error discrepancy noted above, may be attributed to a number of causes: • Convergence limits when balancing a hull to a specified displacement or centre of gravity. • Different number of integration stations used, and their distribution. Where there are large changes in shape, such as near the bow and stern, the stations should be more closely spaced. This can be of particular importance if the waterline intersects the stem profile between two sections.

• Differences in the hull definition, and number of interpolation points used to define each section. If the surface is exported as DXF poly-lines then the precision used and the number of straight-line sections used to make up the poly-line are important.

• The integration method used: trapezium, Simpson, or higher order methods.

Integration of wetted surface area

At first glance, it may seem that wetted surface area may be calculated by simply integrating the station girth along the length of the hull, in a similar way that one might integrate the station cross-sectional area along the length of the hull to obtain the volume. However, this is not the case, and the wetted surface area can only be accurately found by summing elemental areas over the complete surface. Further, the error due to integrating girths along the vessel length cannot be removed simply by increasing the number of integration stations. The only accurate numerical method is to sum the areas of individual triangles interpolated on the parametric surface. The differences are easily shown by considering the surface area of half a sphere. This is given analytically by: A = 2πR 2 , where R is the radius of the circle. It may be shown that the area obtained by integrating the girth of the sphere along its length is given by: A = 2πR 2 , note that this is with an infinite number of integration steps, and there is a error factor of

π

2

, or approximately 57%.

However, for normal ship hulls the differences will be much less, due to the greatly reduced longitudinal curvature. Surface areas calculated by the 'Calculate Areas' dialogue in Maxsurf are the most accurate, since they are derived from the actual parametric definition of the surface. Those calculated by Hydromax and most other hydrodynamics packages, which use a number of vertical stations to define the hull, will be subject to the error described above.

Page 228

Appendix A

Reference Designs A folder of reference hull shapes is included with Maxsurf and Hydromax. These designs are of simple geometric shapes and can be used to validate calculations performed by Hydromax. Below is a table of results derived analytically from these shapes compared with results obtained from Maxsurf and Hydromax at different precisions.

Page 229

Appendix A

Reference Calculations Hydrostatics calculations for various reference designs, comparison of Maxsurf and Hydromax with analytical values sphere 10m diam at 5m draft

Analytically derived

Volume m^3 261.79939

WP Area m^2 78.53982

VCB LCB m m -1.875 0

Hydromax High Precision

260.4998

78.381

-1.874 0

Hydromax Low Precision

260.34279

78.357

-1.874 0

Maxsurf Hi Precision

261.532

78.341

-1.875 0

Maxsurf Low Precision

257.105

77.849

-1.871 0

10m Cylinder 10m diam. at 5m draft Volume m^3 Analytically derived 392.699

WP Area m^2 100

VCB LCB m m -2.122 0

Hydromax High Precision Hydromax Low Precision Maxsurf Hi Precision Maxsurf Low Precision

100 100 100 100

-2.121 -2.121 -2.122 -2.118

Page 230

391.991 391.991 392.522 389.874

0 0 0 0

Trans. I m^4 Long. I m^4 Volume WP Area Trans. I 490.873852 490.87385 % error % error % error 488.6807269 489.14247 -0.50% -0.20% 0.45% 488.564741 488.93873 -0.56% -0.23% 0.47% 490.57 485.761 -0.10% -0.25% 0.06% 483.191 480.89 -1.79% -0.88% 1.57%

Long. I % error 0.35% 0.39% 1.04% 2.03%

Trans. I m^4 Long. I m^4 Volume WP Area Trans. I 833.333333 833.33333 % error % error % error 833.333333 833.33333 -0.18% 0.00% 0.00% 833.333333 833.33333 -0.18% 0.00% 0.00% 833.333 833.333 -0.05% 0.00% 0.00% 833.333 833.333 -0.72% 0.00% 0.00%

Long. I % error 0.00% 0.00% 0.00% 0.00%

Appendix A

Box 20m long 10m beam at 5m draft Volume m^3 Analytically derived 1000

WP Area m^2 200

VCB m -2.5

LCB m 0

Hydromax High Precision Hydromax Low Precision Maxsurf Hi Precision Maxsurf Low Precision

200 200 200 200

-2.5 -2.5 -2.5 -2.5

0 0 0 0

1000 1000 1000 1000

Parabolic Wigley type Hull, LWL=15m,B=1.5m,D=0.9375 Volume WP Area VCB LCB m^3 m^2 m m Analytically derived 9.375 15 -0.352 0 Hydromax High Precision

9.364

14.985

-0.352 0

Hydromax Low Precision

9.351

14.98

-0.352 0

Maxsurf Hi Precision

9.372

14.999

-0.351 0

Maxsurf Low Precision

9.302

14.942

-0.351 0

Trans. I m^4 Long. I m^4 Volume WP Area Trans. I 1666.666666 6666.6667 % error % error % error 1666.666666 6666.6667 0.00% 0.00% 0.00% 1666.666666 6666.6667 0.00% 0.00% 0.00% 1666.667 6666.667 0.00% 0.00% 0.00% 1666.667 6666.667 0.00% 0.00% 0.00%

Long. I % error 0.00% 0.00% 0.00% 0.00%

Trans. I m^4 Long. I m^4 Volume WP Area Trans. I 1.92875 168.75 % error % error % error 1.92527 168.4685 -0.12% -0.10% 0.18% 1.92418 168.3773 -0.26% -0.13% 0.24% 1.927 168.63 -0.03% -0.01% 0.09% 1.91 167.621 -0.78% -0.39% 0.97%

Long. I % error 0.17% 0.22% 0.07% 0.67%

Page 231

Appendix B

Appendix B Criteria file format The criteria are saved in a Hydromax criteria file with the extension .hcr. The file is a normal PC text file, which may be edited manually so as to generate custom criteria. The typical format of the file is given below: Hydromax Criteria File [units] LengthUnits = m MassUnits = tonne SpeedUnits = kts AngleUnits = deg GZAreaGMAngleUnits = deg [end] [criterionGroup] GroupName = Specific Criteria ParentGroupName = root [end] [criterionGroup] GroupName = My Custom Criteria ParentGroupName = root [end] [criterionGroup] GroupName = STIX input data ParentGroupName = Specific Criteria [end] [criterion] Type RuleName CritName CritInfo CritInfoFile Locked GroupName TestIntact TestDamage Test Compare UseLoHeel UseEquilibrium UseHiHeel UseFirstPeak UseMaxGZ UseFirstDF UseVanishingStab LoHeel HiHeel RequiredValue [end] Page 232

= = = = = = = = = = = = = = = = = = = = =

CTStdAreaUnderGZBetweenLimits STIX input data GZ area to the lesser of downflooding or… Area under GZ curve between specified heel… HMCriteriaHelp\StixHelp.rtf true STIX input data true false false GreaterThan false true false false false true true 0.0 30.0 0.000

Appendix B

[criterion] Type RuleName CritName CritInfo CritInfoFile Locked GroupName TestIntact TestDamage Test Compare RequiredValue [end]

= = = = = = = = = = = =

CTStdAngleOfVanishingStab STIX input data Angle of vanishing stability Calculates the angle of vanishing stability… HMCriteriaHelp\StixHelp.rtf true STIX input data true false false GreaterThan 0.0

The file must have “Hydromax Criteria File” in the first row. The first section of the file is the units section and this specifies the units that are to be used in the file. There are two angular units: AngleUnits Specifies the units for angular measurements, e.g. range of stability GZAreaGMAngleUnits Specifies the angle units used for area under GZ graph and for GM. The criteria then appear after the units section and as many criteria as required may be included. The common parameters for all criteria are as follows: Type Describes the type of criterion RuleName Text which specifies the rule to which the criterion belongs CritName Text which specifies the criterion’s name CritInfo Verbose description of the criterion Locked Whether the criterion may be edited in Hydromax or not. If Locked is set to true, it is not possible to edit the criterion’s parameters in Hydromax The other parameters that may be set depend on the criterion type. The available criterion types are as follows: Criteria at equilibrium CTStdEquiAngle Angle of equilibrium CTStdEquiFreeboard Freeboard at equilibrium CTStdEquiGM GM at equilibrium GZ curve criteria CTStdValueOfGMAt Value of GM at specified heel angle CTStdValueOfGZAt Value of GZ at specified heel angle. CTStdValueOfMaxGZ Maximum value of GZ in specified range CTStdRatioOfGZValues Ratio of two GZ values at specified heel angles. CTStdAngleOfMaxGZ Angle at which maximum GZ occurs. CTStdAngleOfEquilibrium Angle of equilibrium. CTStdAngleOfDownflooding Angle at which first down flooding point is Page 233

Appendix B

CTStdAngleOfVanishingStab CTStdRangeOfStability CTStdAreaUnderGZBetweenLimits CTStdHSCMonoAreaUnderGZBetweenLimits CTStdHSCMultiAreaUnderGZBetweenLimits Heeling arm criteria CTStdHeelValueOfGMAtEquilibrium CTStdHeelValueOfGZAtEquilibrium CTStdHeelValueOfMaxGZAboveHA CTStdHeelRatioOfGZValues CTStdHeelAngleOfMaxGZAboveHA CTStdHeelAngleOfEquilibrium CTStdPassengerCrowdingAngleOfEquilibrium

CTStdHighSpeedTurnAngleOfEquilibrium CTStdDerivedHeelArmAngleOfEquilibrium CTStdHeelAngleOfVanishingStab CTStdHeelRangeOfStability CTStdHeelAreaBetweenGZAndHABetweenLimits CTStdHeelRatioOfAreas1Turning CTStdHeelRatioOfAreas1Lifting CTStdHeelRatioOfAreas2 Multiple heeling arm criteria CTStdMultiHeelRatioOfGZValues

immersed. Angle of vanishing stability. Range of positive stability. Area under GZ curve Area under GZ curve – required area depends on upper limit, linear Area under GZ curve – required area depends on upper limit, exponential Value of GM at angle of equilibrium with specified heel arm. Value of GZ at angle of equilibrium with specified heel arm.

Angle of equilibrium with specified heel arm. Generic heeling arm Angle of equilibrium with specified heel arm. Passenger crowding heeling arm Angle of equilibrium with specified heel arm. Turning heeling arm Derived wind heeling Angle of vanishing stability with specified heel arm. Range of stability with generic wind heeling arm Area between GZ curve and heeling arm Area ratio, method 1 using generic heeling arm Area ratio, method 1 using sin+cos heeling arm Ratio of areas based on US Navy wind heeling criterion.

GZ ratio for combined heeling arms CTStdMultiHeelAngleOfEquilibrium Angle of equilibrium for combined heeling arms CTStdMultiHeelAreaBetweenGZAndHABetweenLimits Area between GZ curve and heeling arm, for combined heeling arms CTStdMultiHeelRatioOfAreas1Turning Ratio of areas method 1 Page 234

Appendix B

for combined heeling arms Heeling arm, combined criteria CTStdHeelGenericTurning CTStdHeelGenericLifting CTStdHeelGenericWindHeeling

CTStdHeelWindHeeling

Combined criteria for turning Combined criteria for lifting of heavy weights Combined angle of equilibrium, ratio of GZ values and ratio of areas criteria for specified heeling arm; based on US Navy wind heeling criterion. Uses generic heeling arm Combined angle of equilibrium, ratio of GZ values and ratio of areas criteria for specified heeling arm; based on US Navy wind heeling criterion. Uses wind heeling arm

Page 235

Appendix C

Appendix C Reference Tables This appendix contains the following reference tables: • File Extension Reference Table • Analysis settings reference table

Page 236

Appendix C

File Extension Reference Table The following table lists files that are used in Hydromax. The .hmd file contains all the additional information that defines the Hydromax model and you need only save this file when working in Hydromax. However, if you wish to transfer loadcases or compartment definitions from one model to another, this can be done by going to the appropriate window and saving it to a separate file. File Maxsurf Design

Hydromax Design

Extension .msd

.hmd

Description Contains control point and surface information. E.g. precision, flexibility, thickness, outside arrows, trimming, colour When opening a .msd file Hydromax looks for a .hmd file with the same name. Contains hydrostatic sections information and all Input information that may also be stored separately in the files below The .hmd file does not contain: - Maxsurf surface information - Links to or information on the Stability Criteria Library - Links to or information on the Results tables - Links to or information on the Report

Separate Input files Loadcase Compartments

Extension .hml .htk

Damage cases

.dcs

All Input window tables

.txt

Output files All Result Window tables

Extension .txt

Report Library Hydromax Criteria Library

.rtf Extension .hcr

Description Each loadcase can be saved separately The compartment definition can be saved separately The damage case definition can be saved separately All tables in the input window can be saved as text files. Downflooding/embarkation points, margin lines, sounding pipes and modulus Description Result tables can be saved separately Results tables can not be opened in Hydromax The report can be saved separately Description The library is not related to the Hydromax Design File, i.e. is not model related. The library is loaded when the program starts, not when the model is opened. For more information see the section on criteria.

Page 237

Appendix C

Analysis settings reference table The following table can be used as a reference to the various analysis settings for each analyses type. Analysis Settings Analyses Trim Heel Draft Displace LCG TCG VCG type -ment Upright stability

X

Upright

R

-

-

-

For GM only

Large Angle Stability

X/ FTTLC

R

-

LC

LC

LC

LC

Equilibriu m

-

-

-

LC

LC

LC

LC

Specified Condition

X

X

X

X / LC

X / LC

X / LC

X / LC

KN values

X/ FTT

R

-

R

X/ FTT

TCG=0*

X1

Limiting KG

X/ FTT

R

-

R

X/ FTT

TCG=0*

-2

Floodable Length

FTT

Upright

-

R

X/ FTT

Upright

X3

Tank Calibration

X

Upright

n/a

n/a

n/a

n/a

n/a

Where,

X R LC FTTLC FTT

Cannot be specified – they are calculated Specific (fixed) value to be set by user Varied within range specified by user Calculates values from loadcase – specifies displacement and COG only Free to trim to loadcase CG Free to trim to LCG calculated from a specific initial trim angle or specified LCG (and VCG) 1 The VCG is used in two ways in the KN analysis. a) The VCG only has an effect on the results if the analysis is free to trim. b) The GZ curve is calculated for the specified VCG and then the normalised KN curve is calculated as KN = GZ + VCG*SIN(heel).

Page 238

Appendix C

2

The VCG is not required for the Limiting KG analysis. When calculating the LCG from a specified trim and displacement, the effect of VCG is ignored. If the trim is small and the VCG relatively close to the VCB, the effect of VCG will be negligible. If the analysis is free to trim, then the GZ curve is recalculated as required using the actual Limiting VCG. 3

The VCG is required for the floodable length analysis because of its effect on trim. During the floodable length analysis, the trim can be substantial and hence grater accuracy is achieved by including the effect of the VCG. TCG = 0* Hydromax assumes TCG = 0 for upright vessels. For asymmetric vessels, this means that the KN value at zero heel will not be equal to zero.

Page 239

Index

Index A About Hydromax ....................................... 220 Add............................................................. 211 Add Load ..................................................... 35 Add Point ..................................................... 58 Add Surface Areas ..................................... 211 Allowable shears and moments.................... 60 Analysis Input ......................................................... 32 Menu ...................................................... 212 Output .................................................... 103 Settings................................................... 238 Toolbar................................................... 207 Analysis in waves ........................................ 69 Analysis type Equilibrium .............................................. 67 Floodable Length ..................................... 79 KN Values Analysis................................. 73 Large Angle Stability ............................... 64 Limiting KG............................................. 75 Longitudinal Strength .............................. 82 Specified Conditions................................ 71 Tank Calibrations..................................... 85 Upright Hydrostatics ................................ 62 Animate...................................................... 219 Arrange Icons............................................. 219 B Batch Analysis ............................................. 88 Batch Processing........................................ 216 Beam .......................................................... 222 Block Coefficient ....................................... 224 Boundary Box .............................................. 39 C Calibration Increment .................................. 57 Cascade ...................................................... 219 Case Menu ................................................. 216 Cell Border................................................. 211 Cell Shading............................................... 211 Centre of buoyancy .................................... 194 Centre of flotation ...................................... 194 Centre of gravity ........................................ 194 Close .......................................................... 209 Coefficients, calculation of ........................ 217 Coefficients, Hydrostatic ............................. 33 Colour ........................................................ 212 Compartment definition saving ..................................................... 107 Page 240

Compartment Definition ...................... 38, 197 Compartment types ...................................... 50 Compartments .......................................... 51 Linked ...................................................... 51 Linked Negative....................................... 51 Linked Tanks ........................................... 51 Non-Buoyant Volumes ............................ 51 Tanks........................................................ 51 Compartments, Forming .............................. 47 Convergence Error ....................................... 95 Coordinate system........................................ 32 Copy................................................... 105, 210 Copying Graphs ......................................... 105 Copying Tables .......................................... 105 Corrected VCG ............................................ 97 Criteria ....................................................... 214 Cut.............................................................. 210 D Damage ................................................ 54, 102 Damage Case Add................................................... 54, 216 Delete ............................................... 55, 216 Display ..................................................... 55 Edit......................................................... 216 Rename .................................................... 55 saving ..................................................... 107 Select........................................................ 55 Damage Window ....................................... 196 Data Format ....................................... 198, 217 Data layout................................................. 198 Delete ......................................................... 211 Delete Cells................................................ 211 Density ................................................. 98, 214 Design Preparation....................................... 20 Design, coherence ........................................ 22 Design, saving............................................ 107 Displacement ....................................... 92, 213 Display Menu............................................. 217 Distributed Loads......................................... 36 Downflooding Angles.................................. 66 Downflooding points ........................... 58, 197 Linking to tanks or compartments ........... 59 Draft ........................................62, 92, 213, 223 DWL ............................................................ 62 DXF export ................................................ 109 E Edit Menu .................................................. 210 Edit Toolbar ............................................... 207

Index

Equilibrium ............................................ 10, 67 Equilibrium Condition ................................. 10 Error Values ......................................... 95, 211 Exit............................................................. 210 Export......................................................... 210 Exporting ................................................... 109 F File Extension Table .................................. 237 File Menu ................................................... 209 File Toolbar................................................ 207 File, Hydromax Version 8.0....................... 109 Fill Down ................................................... 210 Floodable Length ......................................... 14 Floodable Length Criteria dialog ............... 214 Flooding ....................................................... 55 Fluid analysis method .................................. 97 Fluid VCG.............................................. 37, 98 Fluids ......................................................... 214 Font ............................................................ 212 Form parameters ........................................ 221 Frame of Reference........................ 20, 33, 218 Free Surface Moment............................. 37, 97 Free Surface Moment, options ..................... 38 Freeboard ..................................................... 68 G Graph ......................................................... 220 Data interpolation................................... 201 double click............................................ 202 get data ................................................... 202 Type ....................................................... 201 Graph Window........................................... 200 Grounding .......................................... 100, 214 GZ .................................................................. 9 H Heel ...................................................... 90, 213 Help Menu ................................................. 220 Hog and Sag....................................... 101, 214 Home View ........................................ 194, 212 Horizontal lever ........................................... 35 Hull Sections, Recalculate ......................... 215 I Immersion .................................................. 227 Immersion Angles........................................ 66 Initial Conditions ......................................... 32 Input ........................................................... 220 Input Tables, saving ................................... 107 Input Window ............................................ 196 Insert New Table........................................ 211 Insert Row.................................................. 211 Installing Hydromax .................................... 18

K Key points ............................................ 58, 197 adding....................................................... 58 Data.......................................................... 66 deleting..................................................... 58 editing ...................................................... 58 Results.................................................... 199 KN Values.............................................. 12, 73 L Large Angle Stability............................... 9, 64 LCB, LCG.................................................. 225 Length ........................................................ 221 Limiting KG......................................13, 75, 79 Loadcase .............................................. 34, 220 Adding and Deleting loads....................... 35 Distributed loads ...................................... 36 Editing loads ............................................ 35 Free surface correction............................. 37 maximum number ............................ 34, 217 Naming..................................................... 34 saving ..................................................... 107 Tank loads................................................ 37 Update...................................................... 37 Loadcase Formatting............................ 35, 196 Blank lines ............................................... 35 Grouping tanks......................................... 36 Headings lines.......................................... 35 Total lines ................................................ 35 Longitudinal Strength ............................ 15, 82 M Margin Line points............................... 60, 197 Margin Line, Snap to hull .......................... 215 Maximum deck inclination ........................ 226 Maximum shears and moments ................... 60 Menus......................................................... 209 Merge Cells................................................ 211 Midship Section ......................................... 223 Midship Section Coefficient ...................... 224 Modulus points .......................................... 197 Modulus Window ........................................ 60 Moment to trim .......................................... 227 N New............................................................ 209 Non-Buoyant Volume Definition ................ 38 O Open..................................................... 22, 209 Outside arrows ............................................. 21

Page 241

Index

P Page Setup.................................................. 210 Pan ..................................................... 194, 211 Paste ........................................................... 210 Permeability ..............................14, 44, 93, 213 Perspective view ........................................ 194 Plating thickness .......................................... 21 Precision, surface ......................................... 23 Preferences................................................... 18 Print............................................................ 210 Print Preview.............................................. 106 Printing....................................................... 106 Prismatic Coefficient ................................. 224 R Ratio of equilibrium angles - derived heeling arm ......................................................... 171 Reference Calculations .............................. 230 Reference Designs ..................................... 229 Relative Density..................................... 45, 98 Render ........................................................ 219 Render Transparent.................................... 219 Report Window.......................................... 203 Keystrokes.............................................. 205 Results........................................................ 220 Results Window ......................................... 198 Results, saving ........................................... 107 Resume Analysis.................................. 87, 215 Righting Moment ....................................... 227 Row Positioning......................................... 211 S Save.................................................... 107, 209 Save As ...................................................... 209 Section, show single................................... 218 Sectional Area Curve ................................... 30 Sections, Forming ........................................ 25 Select All.................................................... 210 Select View from Data....................... 104, 219 Set Analysis Type ...................................... 215 Set Home View .......................................... 212 Shift Key ...................................................... 18 Show Grid .................................................. 211 Show single hull section .............................. 29 Shrink................................................. 194, 211 Simulate fluid movement ............................. 98 Sounding Pipes..................................... 56, 197 Calibration Increment .............................. 57 Edit........................................................... 57 Specific Gravity ..................................... 45, 98 Specified Condition ....................... 11, 71, 213 Specified Conditions, dialog ........................ 93 Split Cell .................................................... 211 Page 242

Stability booklet ........................................... 97 Stability criteria............................................ 60 Stability Criteria Results ............................ 200 Stability criteria, Angle of deck edge immersion .............................................. 137 Stability criteria, Angle of downflooding .. 136 Stability criteria, Angle of equilibrium ...... 136 Stability criteria, Angle of equilibrium derived wind heeling arm....................... 170 Stability criteria, Angle of equilibrium general heeling arm........................ 164, 165 Stability criteria, Angle of equilibrium - highspeed turn heeling arm ........................... 166 Stability criteria, Angle of equilibrium multiple heeling arms............................. 179 Stability criteria, Angle of equilibrium passenger crowding heeling arm............ 166 Stability criteria, Angle of margin line immersion .............................................. 136 Stability criteria, Angle of maximum GZ .. 136 Stability criteria, Angle of maximum GZ above heeling arm - general heeling arm 164 Stability criteria, Angle of vanishing stability ............................................................... 137 Stability criteria, Angle of vanishing stability general heeling arm................................ 166 Stability criteria, Areas and levers ............. 156 Stability criteria, check boxes .................... 119 Stability criteria, Combined criteria (ratio of areas type 1) - general cos+sin heeling arm ............................................................... 183 Stability criteria, Combined criteria (ratio of areas type 1) - general heeling arm ........ 182 Stability criteria, Combined criteria (ratio of areas type 1) - high-speed turn............... 182 Stability criteria, Combined criteria (ratio of areas type 1) - lifting weight .................. 183 Stability criteria, Combined criteria (ratio of areas type 1) - passenger crowding ........ 182 Stability criteria, Combined criteria (ratio of areas type 1) - towing............................. 183 Stability criteria, Combined criteria (ratio of areas type 2) - general wind heeling arm 183 Stability criteria, Combined criteria (ratio of areas type 2) - wind heeling arm............ 186 Stability criteria, criteria library file .......... 123 Stability criteria, damage and intact settings ............................................................... 117 Stability criteria, defining custom criteria.. 116 Stability criteria, details ............................. 118 Stability criteria, equilibrium ..................... 129 Stability criteria, General cos+sin heeling arm ............................................................... 151

Index

Stability criteria, General heeling arm ....... 150 Stability criteria, glossary .......................... 128 Stability criteria, Gust ratio........................ 155 Stability criteria, GZ area between limits general heeling arm................................ 173 Stability criteria, GZ area between limits multiple heeling arms............................. 179 Stability criteria, GZ area between limits type 1 - standard............................................. 137 Stability criteria, GZ area between limits type 2- HSC monohull type ........................... 139 Stability criteria, GZ area between limits type 3 - HSC multihull type........................... 141 Stability criteria, GZ area derived heeling arm - general heeling arm ............................. 168 Stability criteria, GZ area derived heeling arm (type 2) - general heeling arm ................ 169 Stability criteria, GZ curve features........... 125 Stability criteria, GZ definitions ................ 127 Stability criteria, GZ derived heeling arm general heeling arm................................ 167 Stability criteria, GZ, non-healing arm ...... 130 Stability criteria, heeling arm definition .... 150 Stability criteria, heeling arm dependency on displacement .......................................... 151 Stability criteria, heeling arm units ............ 156 Stability criteria, Heeling due to bollard-pull ............................................................... 153 Stability criteria, Heeling due to lifting of weights crowding ................................... 153 Stability criteria, Heeling due to passenger crowding ................................................ 152 Stability criteria, Heeling due to towing .... 153 Stability criteria, Heeling due to turning.... 152 Stability criteria, Heeling due to wind ....... 154 Stability criteria, IMO Code on Intact Stability A.749(18) ............................................... 156 Stability criteria, IMO HSC Code MSC.36(63 ............................................................... 158 Stability criteria, importing ................ 122, 123 Stability criteria, ISO 12217 ...................... 190 Stability criteria, list................................... 115 Stability criteria, Maximum Freeboard at equilibrium............................................. 130 Stability criteria, Maximum value of heel, pitch or slope at equilibrium .................. 129 Stability criteria, Minimum Freeboard at equilibrium............................................. 129 Stability criteria, moving criteria ............... 116 Stability criteria, Other criteria - STIX ...... 188 Stability criteria, overview......................... 112 Stability criteria, parent criteria ......... 115, 129 Stability criteria, pass/fail test.................... 120

Stability criteria, Range of positive stability ............................................................... 137 Stability criteria, Range of positive stability general heeling arm................................ 167 Stability criteria, Ratio of areas type 1 general cos+sin heeling arm................... 175 Stability criteria, Ratio of areas type 1 general heeling arm................................ 174 Stability criteria, Ratio of areas type 1 multiple heeling arms............................. 180 Stability criteria, Ratio of areas type 2 general wind heeling arm....................... 176 Stability criteria, Ratio of GZ area between limits ...................................................... 143 Stability criteria, Ratio of GZ values at phi1 and phi2.................................................. 134 Stability criteria, Ratio of GZ values at phi1 and phi2 - general heeling arm............... 163 Stability criteria, Ratio of GZ values at phi1 and phi2 - multiple heeling arms............ 178 Stability criteria, Ratio of positive to negative GZ area between limits .......................... 147 Stability criteria, report and batch processing ............................................................... 122 Stability criteria, resizing dialog ................ 114 Stability criteria, results ............................. 121 Stability criteria, saving ............................. 123 Stability criteria, selecting for analysis ...... 117 Stability criteria, setting up for analysis..... 113 Stability criteria, tree list............................ 116 Stability criteria, USL code........................ 160 Stability criteria, Value of GMt at ............. 130 Stability criteria, Value of GMt at equilibrium - general heeling arm ............................. 162 Stability criteria, Value of GMt or GMl at equilibrium............................................. 130 Stability criteria, Value of GZ at................ 131 Stability criteria, Value of GZ at equilibrium general heeling arm................................ 162 Stability criteria, Value of GZ at specified angle or maximum GZ below specified angle....................................................... 132 Stability criteria, Value of maximum GZ .. 131 Stability criteria, Value of maximum GZ above heeling arm - general heeling arm 163 Stability criteria, Value of RM at specified angle or maximum RM below specified angle....................................................... 134 Start Analysis ....................................... 87, 215 Starting Hydromax....................................... 18 Status Bar................................................... 212 Stop Analysis ....................................... 87, 215 Surface Use .................................................. 20

Page 243

Index

T Table .......................................................... 210 Tank adding, deleting........................................ 38 Fluids ....................................................... 45 Ordering ................................................... 46 Permeability ............................................. 44 saving ..................................................... 107 Surface Thickness .................................... 46 Visibility .................................................. 46 Tank Calibrations................................... 16, 85 Tank Type complex.................................................... 40 external..................................................... 42 linked ....................................................... 40 simple....................................................... 39 tapered...................................................... 39 Tanks, Non-Buoyant Areas.......................... 42 Tanks, Recalculate ............................. 207, 214 Tile Horizontal ........................................... 219 Tile Vertical ............................................... 219 Toolbars ............................................. 207, 212 Trapezoidal integration ................................ 25 Trim ..................................................... 91, 213 Fixed ........................................................ 91 Free to trim to a specified LCG value...... 92 Free to trim using a specified initial trim value..................................................... 92 Trim angle.................................................. 226 Trimmed surfaces, checking ........................ 21 U Undo........................................................... 210 Units..................................................... 33, 217 Update Loadcase........................................ 214 Upright Hydrostatics................................ 8, 62 V Validate Hydromax model ........................... 29 View Direction........................................... 219 View Menu ................................................ 211 View Toolbar ............................................. 207 View Window ............................................ 194 Visibility .................................................... 218 Visibility Toolbar....................................... 208 W Waterplane Area Coefficient ..................... 225 Wave definition............................................ 99 Wave height ............................................... 100 Waveform .................................................. 214 sinusoidal ............................................... 100 trochoidal ............................................... 100 Page 244

Wavelength ................................................ 100 Wetted surface area, integration of ............ 228 Window Menu ........................................... 219 Window Toolbar ........................................ 208 Windows Registry........................................ 18 Z Zero Point .................................20, 33, 35, 218 Zoom.................................................. 194, 211