Ship Structure Terminology

Angle Bar

A bar of angle-shaped cross section used as a stiffener.

Bulwark Stay

A brace extending from the deck to a point near the top of the bulwark, to keep it rigid.

Gusset Plate

A bracket plate lying in a horizontal, or nearly horizontal plane. A tie plate, used for fastening posts, frames, beams, etc., to other objects.

Web Frame

A built-up frame to provide extra strength, usually consisting of a web plate flanged or otherwise stiffened on its edge, spaced several frame spaces apart, with smaller regular frames in between.

Corrugated Bulkhead

A bulkhead constructed of plate bent in alternating directions, such that welded stiffeners are not required.

Chain Locker

A compartment for the stowage of anchor chain.

Rider Plate

A continuous flat plate attached to the top or bottom of a girder.

Girder

A continuous member running fore and aft under a deck for the purpose of supporting the deck beams and deck. Also, the vertical fore and aft members in the bottom structure.

Strake

A course, or row, of shell, deck, bulkhead, or other plating.

Ceiling

A covering usually of wood, placed over the tank top for its protection.

Cant Beam

A deck beam not square to the centerline, connected to the cant frames.

Skeg

A deep vertical finlike projection of the keel near the stern. Sometimes extends to support the bottom of the rudder.

Bracket Floor

A floor built up of flanged plates (brackets) and other plate or rolled forms. Compare to solid floor.

Solid Floor

A floor constructed from continuous plate. May have lightening and access holes. Contrast with bracket floor.

Cant Frame

A frame not square to the centerline, usually in the stern of the ship.

Rabbet

A groove or offset into which the edge of another structural member is fitted, such that the two are flush.

Deck Transverse

A heavy athwartships horizontal structure, built up from plate, supporting a deck.

Stern Frame

A heavy casting forming the stern profile in way of the propeller and rudder.

Stem Casting

A heavy casting used to form the stem, where a stem bar or rolled plate do not provide sufficient strength.

Bed Plate

A heavy structure that distributes engine weight and stresses to the ship's structure.

Lightening Hole

A hole cut in a structural member where it can be made lighter without reducing its strength.

Manhole

A hole cut in structural member to provide access for a person to pass through for inspection, cleaning, and repairs.

Air Hole

A hole in the upper part of a solid floor to equalize the pressure between floors of a double bottom tank.

Stringer

A horizontal, fore and aft girder running along the side of the ship at the shell, and the outboard strake of plating on any deck.

Flate Plate Keel

A keel built up from flat plate, usually consisting of the keel plate, center vertical keel, and inner bottom plating.

Duct Keel

A keel built up to form a box beam, such that piping and other systems may run fore and aft.

Bar Keel

A keel made up of a single heavy bar, common on smaller vessels that operate in restricted water.

Keelson

A large I-beam placed above the vertical keel on the rider plate for reinforcing the keel.

Spectacle Frame

A large casting extending from the hull, providing support for and forming the trailing edge of the propeller shaft bossing on multi-screw ships.

Torsion Box

A large heavy box girder at the deck edge of a containership.

Bilge Keel

A long longitudinal fin fitted at the turn of the bilge to reduce rolling.

Deck Longitudinal

A longitudinal horizontal structural member supporting a deck.

Transverse Framing

A method of framing a ship characterized by many closely spaced transverse frames.

Longitudinal Framing

A method of framing a ship characterized by many smaller, closely spaced longitudinal stiffeners.

Bulb Plate

A narrow plate generally of mild steel, rolled with a bulb along one edge. Used as a hatch coaming or stiffener.

Intercostal Side Girder

A non-continuous vertical plate stiffener running fore and aft some distance off centerline, fitted between floors in the bottom structure, running from bottom plating to tank top.

Wash Bulkhead

A non-tight bulkhead used to reduce the sloshing motion of liquids in tanks.

Perforated Flat

A non-watertight horizontal structure in the fore peak, stiffened athwartships and serving the same purpose as panting beams.

Facing Flat

A piece of flat bar or plate welded perpendicular to the edge of another plate to form a flange

Drain Hole/Limber Hole

A small hole or slot in a frame or plate for the purpose of preventing water or oil from collecting.

Stem Bar

A solid round bar used to form the stem, to which the shell plating is welded.

Flat Bar Stiffener

A stiffener, usually on a bulkhead or solid floor, constructed from a piece of plate or bar without a flange.

Forecastle or Fo'c'sle

A superstructure fitted at the extreme forward end of the upper deck.

Breasthook

A triangular plate bracket joining the port and starboard structure at the bow.

Bulkhead

A vertical partition in a ship which divides the interior space into various compartments.

Center Girder

A vertical plate on the ship's centerline between flat keel and inner bottom or rider plate, extending the length of the ship. Also called center vertical keel (CVK) or center keelson.

Rudder Stock

A vertical shaft that connects the rudder to the steering gear, transmitting the steering force.

Athwartships

Across the ship, at right angles to the fore-and-aft centerline.

Stiffener

An angle, T-bar, channel, built-up section, etc. used to stiffen plating.

Deck Beam

An athwartships horizontal structural member, usually a rolled shape, supporting a deck.

Beam Knee

Angular bracket connecting a deck beam to a frame.

Stanchion

Another name for a pillar.

Tank Top

Another word for inner bottom.

Panting Beam

Beams in the fore and aft part of the ship, tying the panting frames together and providing further resistance to panting.

Watertight Bulkhead

Bulkhead dividing ship into main compartments and preventing progressive flooding in case of damage.

Bilge Strake

Course of shell plating at the bilge.

Doubler Plate

Extra plates added to strengthen sections where holes have been cut in a structure, or where strain or wear is expected.

Tripping Bracket

Flat bars or plates fitted at various points on deck girders, stiffeners, or beams as reinforcements to prevent their free flanges from tripping (buckling).

Side Keelson

Fore and aft vertical plate member located above the bottom shell on each side of the center vertical keel and some distance off centerline.

Shedder Plate

Inclined plate welded in the channel of a corrugated bulkhead to keep material out of the bottom corner of the bulkhead.

Hopper Side Longitudinals

Longitudinal stiffeners in the hopper side.

Gudgeon

Lugs on the sternpost drilled for the pintles on which the rudder hinges.

Intercostal

Made in separate parts: between floors, frames or beams; the opposite of continuous. Literally means "between ribs".

Fairwater

Plating fitted around the ends of shaft tubes and shaped to streamline the part.

Inner Bottom

Plating forming the top of the double bottom, also called the tank top.

Deep Tank

Tanks extending from the bottom or inner bottom up to or higher than the lowest deck.

Wing Tank

Tanks located outboard and usually just under the weather deck, sometimes formed by fitting a longitudinal bulkhead between the two uppermost decks.

Head Ledge

Technically, the athwartship equivalent of the hatch coaming.

Bossing

The aperture in the stern frame where the propeller shaft enters.

Panting

The bellows-like pulsation of the bow and stern plating at ends of the ship alternately rise and fall in the water.

Stem

The bow frame forming the apex of the intersection of the forward sides of the ship. The shape of the bow profile.

Hopper Side

The chamfer corner structure in a bulk or ore carrier hold. The hopper side eliminates the corners in the hold and provides additional tank space for ballast.

Aft Peak

The compartment in the stern, aft of the aftermost watertight bulkhead.

Scantlings

The cross-section dimensions of a ship's frames, girders, plating, etc.

Steering Flat

The deck in the aft peak on which the steering gear is mounted.

Strength Deck

The deck that is designed as the uppermost part of the main hull girder.

Collision Bulkhead

The foremost main transverse watertight bulkhead. It extends from the keel to the freeboard deck and is designed to keep the entire ship from being flooded in case of collision.

Hatch Side Girder

The girder supporting the deck at the hatch opening.

Bearding Line

The line of intersection of the plating and the stem or sternpost.

Gunwale

The line where a shelter deck stringer meets the shell.

Inner Bottom Longitudinals

The longitudinal stiffeners attached to the inner bottom plating.

Bottom Longitudinals

The lower longitudinal stiffeners in the double bottom, welded to the shell plate.

Fore Peak

The narrow extremity of a vessel's bow, forward of the collision bulkhead.

Margin Plate

The outboard strake of the inner bottom, which closes off the floors and connects the inner bottom to the shell plating.

Fantail

The overhanging stern section of a vessel, from the sternpost aft.

Pintles

The pins that hinge the rudder to the gudgeons on the sternpost.

Shell Plating

The plates forming the outer side and bottom skin of the hull.

Side Shell

The plating forming the side of the hull, in contrast to the bottom plating.

Hopper Plating

The plating over the hopper side, angled such that the cargo material will slide down into the center of the hold as it is unloaded.

Frame

The rib-like stiffeners, holding the shell plating in shape and maintaining the transverse form of the ship.

Tween Decks

The space between any continuous decks.

Garboard Strake

The strake of bottom shell plating adjacent to the keel plate.

Deck Stringer

The strake of deck plating that runs along the outboard edge of a deck.

Fore Peak Tank

The tank within the fore peak, often used to control trim.

Transom Plate

The transverse shell plating forming a transom (square-ended) stern.

Flange

The turned edge of a shape or girder, which acts to resist bending strain.

Hold Frame

The typical frame in the ship's holds. Contrast to the web frames, which have heavier scantlings.

Sheer Strake

The uppermost course of shell plating, at strength deck level.

Sternpost

The vertical part of the stern frame to which the rudder is attached.

Hatch Coaming

The vertical plating bounding a hatch for the purpose of stiffening the edges of the opening and resisting entry of water below.

Stern Tube

The watertight tube enclosing and supporting the propeller shaft.

Hawse Pipe

Tube, usually of heavy cast construction, through which the anchor chain passes overboard at the bow.

Pillar

Vertical columns supporting the decks. Also called stanchions.

Bulwark

Vertical plating immediately above the upper edge of the sheer strake, forming an extension of the side shell above the weather deck.

Rudder Trunk

Vertical space in the aft peak through which the rudder stock passes.

Floor

Vertical transverse plate immediately above the bottom shell plating, often located at every frame.