Glossary of Ship Construction Terms

Technical Bulletin 1 M a r ch 2 0 0 9

Glossary of Ship Construction Terms This is a collection of terms which may be useful to have to hand when reading a surveyor’s report relating to hull damage, it is by no means an exhaustive list but has been kept to the basics so as not to become too in depth. Hopefully it will be of some use to the reader. After perpendicular

An imaginary line drawn perpendicularly through the waterline at the edge of the rudder post where it meets the summer load line.

Aft Peak bulkhead

The first main transverse watertight bulkhead forward of the stern. The aft peak tank is the watertight compartment between this bulkhead and the stern.

Ballast Tanks

Tanks which are filled with sea water to alter the trim or draught of a vessel

Bilge keel

A length of offset bulb plate attached at the bilge position along about a third of the length of a vessel to help reduce rolling. The bilge being the area where the side plating meets the shell plating “the rounding of the bilge”.

Bow

The forward most part of the ship, sometimes termed the “pointy end”.

Bulwark

The plating that stands vertically above the vessel’s exposed decks, these are fitted for safety of personnel and prevent loss of items which may come loose during transit, they are not structural members, and if of solid construction must have freeing ports capable of removing wash from the deck area.

Bulwark

Hatch “Coaming”

Freeing Port

Freeboard deck

Bulbous Bow

Fitted to disrupt bow wave generation and reduce the ship’s resistance.

Collision bulkhead

The foremost transverse main transverse watertight bulkhead.

Coaming

The surrounding vertical structure around cargo hatches or skylights.

Cofferdam

Empty space between two bulkheads, often in place to prevent contamination from one tank to another, in the instance of having a fuel tank next to a ballast tank, the cofferdam would prevent contamination in the event of the bulkhead failing in on tank.

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Deep tank

Tank extending from the shell plating, or inner bottom to the lowest deck or higher.

Double Bottom

The inner bottom is the top of the double bottom structure, below the inner bottom are stiffeners which attach between the shell plating and the inner bottom plating, the plating plus stiffeners is the double bottom structure. The purpose of the double bottom is to maintain watertight integrity should the shell plating become pierced, it is normal on many vessels for the double bottoms to be used as ballast tanks.

Duct Keel

Sometimes know as the pipe duct, it contains piping and valves which would otherwise have to run through cargo holds, it runs along the length of the vessel from the forward transverse bulkhead of the machinery space. As the name “keel” suggests it runs along the bottom of the vessel’s structure. Forecastle

Stem

Bulbous Bow

Fairlead

A reinforced fitting for changing or preserving the direction of a rope, used mainly in mooring the ship.

Floor

Transverse member fitted to the bottom structure.

Forecastle

The raised short superstructure situated above the bow.

Forward perpendicular

An imaginary line drawn perpendicularly through the waterline where the forward edge of the stem meets the summer load line.

Freeboard Deck

The uppermost continuous deck exposed to the weather and sea.

Girder

A primary structural member.

Gusset

Triangular plate fitted to distribute forces between two structural members.

Intercostal

Non continuous section.

Keel

The backbone of the ship, usually a flat plate running longitudinally, which is stiffened by a vertical plate being welded to its centreline inside the hull.

Midship section

This is a cross section taken at the mid position between the two perpendiculars.

Panting

The in and out movement of a ship’s plating caused by changes in pressure due to wave and vessel movement.

Rudder

The aerofoil fin used for steering the vessel, they come in various forms, balanced, semi-balanced and unbalanced.

Rudder Pintle

The pin on which certain types of rudder swing.

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Scantlings

Details and dimension of structural members of the vessel.

Scupper

An outlet for removing unwanted water from the ship’s decks.

Sheer strake

The uppermost strake of plating of the ship’s side plating

Spectacle frame

Strength member which shell plating is attached to, the structure projects out from the vessel to support propeller shaf ts in twin screw ships.

Stem

This is the plating or bar where the termination of shell and side plating at the forward end occurs.

Stern

The after most part of the ship, sometimes termed the “blunt end”.

Stern frame

Strength member including the rudder post used in the construction of single and triple screw vessels.

Rudder Pintles

Stern Frame

Semi-balanced rudder

Stiffener

Added for strengthening plating, in the form of a secondary structural member, flat bar or section.

Stiffeners

Superstructure

Any structure above the freeboard deck spanning more than 92% the breadth of the ship

Transverse

A member running 90 degrees to the centreline of the ship.

Tripping Bracket

A plate added to the free edge of structural members for reinforcement

Tween Decks

An abbreviation of between decks. The deck space between two adjacent decks in a cargo hold.

Void

An enclosed empty space.

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Wash Bulkhead

A partial bulkhead fitted along the centreline in a tank, usually found in deep tanks and peak tanks to withstand the flow of liquid caused by the ship’s motion.

Watertight bulkhead

A transverse bulkhead compartments

for

separating

the

ship’s hull

into

watertight

Mooring winches and windlasses on the forecastle deck Fairlead

Winch

A piece of equipment used for winding in ropes, use in mooring operation, found at the fore and aft ends of the ship.

Windlass

A similar piece of equipment to the winch used for raising the ship’s anchor, often combined to operate as a windlass and winch with a clutch to disconnect the windlass

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