Naval Architecture terms

Terminologies & Definitions
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Alongside
The position of a vessel when securely moored on a berth in port.
Amidships
(1) Midway (midpoint) between port and starboard sides of a vessel. (2) The midway point between the forward and aft perpendiculars.
Anchor
A heavy steel device (of variable design) so shaped as to grip the sea bed to hold a vessel or offshore installation in a desired position.
Anchor cable
Chain or wire connecting a vessel to its anchor(s).
Anode
(1) The electrode at which oxidization occurs. (2) Zinc ingot attached to the immersed hull preventing corrosion of the steel.
Antifouling (paint)
A marine paint composition containing toxic ingredients preventing or retarding marine underwater growth on the hull of a vessel.
Appendage(s)
Objects protruding from the underwater section of a hull; e.g., bilge keels, rudders, stabilizing fins, shaft brackets, etc.
Astern
The backward direction in the line of a vessel's centerline.(Opposite to ahead .)
Auxiliary (machinery)
Vessel's machinery other than the main engine(s); e.g., generators, fuel separators, etc.
Azimuth thruster
Marine screw propellers designed to rotate 360° in the horizontal plane about a vertical axis.
Ballast
Liquid or solid mass loaded by a vessel to improve stability and trim characteristics and to increase propeller immersion. Temporary ballast is usually sea water stored in dedicated tanks. Permanent ballast (if required) is usually solid lead castings.
Barge
Flat-bottomed shallow-draft vessel, towed or self-propelled, customarily used in canals and ports.
Baseline
A horizontal and longitudinal datum (reference) line, usually taken at the inner surface of the keel plating, to which all vertical measurements are referred. [Alt. molded baseline.]
Beam
(1) The registered breadth of a vessel, measured at the outside of the hull amidships, or at its greatest breadth. (2) A transverse structural member supporting a deck and/or strengthening a hull.
Bed plate
The upper surface plating of a foundation platform of an engine or deck installation to which that equipment or machinery is permanently attached.
Berth
(1) A location in which a vessel is moored or secured alongside a wharf. (2) Allotted accommodation in a vessel.
Bilge
(1) Intersection or curved transition of bottom and sides of a hull.(2) Lowest points within hull compartments where liquids may accumulate.
Bilge bracket
Vertical transverse plate located beneath side frames in the area of the bilge and between inner and outer bottoms.
Bilge keel
Non-retractable elongated longitudinal fin protruding from the bilge used to reduce rolling.
Bilge strake
Line of shell plating at the bilge between bottom and side plating.
Bitts
Twin stout posts welded to the deck to which mooring lines are fastened.
Body plan
Drawing consisting of 2 end views of a hull showing cross-section form, deck line curvature, and projections (as straight lines) of waterlines and buttock lines.
Bollard
The equivalent of a vessel's mooring bitts used onshore (i.e., on a wharf).
Boot-topping
Durable paint coating applied to a hull between the light and loaded waterlines.
Bossing
Hydrodynamic ally faired outboard portion of hull plating surrounding and supporting propeller shafting. In a single-screw vessel the bossing is integral to a centerline skeg.
Bow
The forward end or region of a hull.
Bow door
Watertight hinged door in the fore end of a Ro-Ro vessel through which vehicles and cargo may be loaded or discharged.
Bow thruster
A propellers installed near the bow to provide a transverse thrust component enhancing maneuverability.
Bracket
Plate used to rigidly connect 2 or more intersecting structural members.
Breadth
Beam or width of a hull or superstructure.
Breasthook
Horizontal plate brackets of generally triangular form connecting port and starboard side stringers and bow plating at the stem.
Bridge
Elevated centre dedicated to the control and navigation of the vessel. [Alt. Navigating bridge Or wheelhouse.]
Bridge wing(s)
Lateral (open or enclosed) extension(s) to a vessel's bridge to permit direct vision beyond the hull side.
Bulk cargo
Cargo shipped in loose condition and of a homogeneous nature.(Includes fluid cargoes.)
Bulk carrier
Vessel designed for the transportation of dry loose homogeneous cargoes in bulk in self-trimming holds and constructed to sustain the heavy concentrated weight distribution of the cargoes.
Bulkhead
(1) A vertical Structural partition dividing a vessel's interior into various compartments for strength and safety purposes; (termed strength bulkhead ). (2) Term applied to vertical partition walls(non-structural) subdividing the interior of a vessel into compartments.
Bulkhead deck
Uppermost deck at which transverse watertight bulkheads terminate.
Bulwark
Barrier of stiffened plating at the outboard edge of the main or upper deck to prevent or inhibit entry of the sea. Bulwarks may be additionally employed at the forward edges of superstructure decks in lieu of safety railings as a barrier to wind and spray.
Buttock line
Line depicted on a lines plan showing the intersection of the hull molded surface with a vertical plane parallel to the centerline.
Butt weld
Full penetration weld joint of 2 plate edges meeting end-to-end.
Cabin
Room or compartment for the accommodation of marine personnel or passengers.
Cable layer
Vessel designed for the laying and repair of seabed telecommunication cables.
Cable locker
Compartment located forward to store the anchor cable.
CAD/CAM
Computer-aided design/computer-aided manufacturing
Camber
Transverse convex curvature of exposed decks to accelerate run-off.
Cant frame
Hull side frame not aligned perpendicular to the vessel's centerline.
Capstan
Steel warping drum rotating on a vertical axis for the handling of mooring lines and optionally anchor cable.
Car carrier
Vessel designed for the delivery transportation of road vehicles.
Cargo door
Watertight door in the hull side through which cargo may be loaded or discharged.
Casing
Bulkheads enclosing upper engine room volume.
Cathodic protection
Sacrificial or impressed current system of corrosion protection of hull, tanks and piping.
Cellular container ship
Container vessel having specially designed vertical cell guides for the accommodation of standard size containers thereby precluding movement and lashing.
Centerline
The longitudinal vertical plane of a vessel.
Chain locker
[refer cable locker.]
Chemical carrier (Tanker)
Vessel designed specifically for the transportation of volatile, poisonous or corrosive liquids in specially constructed tanks.
Classification societies
Organizations which set standards for design and construction of vessels and integral machinery amongst much else.
Coaming
Raised rim of vertical plating around a hatchway to prevent entrance of water, the upper edge of which forms a sealing surface with the hatch-lid or cover.
Cofferdam
Narrow compartment (void space) between 2 transverse bulkheads or floors, to separate incompatible contents or spaces.
Collision bulkhead
The forward-most transverse watertight bulkhead ranging from the bottom of the hull to the bulkhead deck to prevent flooding of compartments aft in the event of collision.
Compartment
Enclosed space usually with watertight bulkheads, doors or hatches.
Complement
The complete crew of a vessel.
Container vessel
Vessel designed specifically for the transportation of standard size containers within the hull and on deck.
Continuous welding
Uninterrupted line of welding along the entire interface.
Counter
The overhanging stern section of a hull extending abaft the aft perpendicular or propeller aperture.
Crew boat
Fast strongly constructed craft for the transportation of offshore oilrig personnel.
Davit(s)
Radial or hinged or telescopic launch/recovery and housing installations for survival craft.
Deadlight
Steel or alloy cover plate fitted internally to portholes for protection against water ingress in case of glass failure.
Deadrise
Transverse inclination of the hull bottom from keel to bilge. [Alt: rise of floor.]
Deck height
Vertical distance between molded lines of 2 adjacent decks. [Alt: deck interval.]
Deck stringer
Strake of deck plating at outboard edge. [Alt: stringer strake.]
Deep tank
Tank (usually for fuel) having significant depth (typically spanning more than 1 deck interval).
Derrick
Obsolete form of lifting appliance employing a hinged boom, kingpost(s) and running wires for control.
Design draft
Draft at which a vessel is designed to carry its contract deadweight.
Det norske Veritas
Norwegian classification society (DnV)
Diesel generator
Alternator (generator) directly powered by a diesel prime mover producing AC electrical power.
Displacement
All-inclusive mass or weight of vessel measured in tones, and equal to the mass of water displaced.
Docking plan
Detailed structural plan and profile of the lower hull structure required for correct location of the vessel in dry docking.
Double bottom
Structural configuration employing a complete watertight inner bottom deck above the hull bottom plating, extending from the collision bulkhead to the aft most watertight bulkhead.
Double skin
Double watertight hull construction, usually referring to hull sides but may include double bottom structure.
Draft (or draught)
Depth to which a hull is immersed.
Draft marks
Numbers marked on the hull side forward, aft (and amidships on large vessels) indicating the draft.
Dredger
Vessel designed for the removal of sea bed alluvial sediment.
Drill ship
Vessel designed for sea bed drilling operations.
Dry bulk
Cargo shipped in a dry state and in bulk; e.g., grain, cement.
Dry dock
(1) Large basin with sealing caisson for the repair and maintenance of vessels. (2) General term for basin dry docks, floating docks orlift platforms for the maintenance and repair of vessels.
Duct
Vertical or horizontal large cross-section conduit through which piping, cabling, or fluids may be conducted.
Duct keel
Longitudinal passage within the double bottom, usually on the centerline, extending from the collision bulkhead to the engine room, through which ballast, bilge, fuel and hydraulic piping maybe conducted and providing access to double-bottom spaces.
Electro-hydraulic
Term given to hydraulic actuation systems where the hydraulic pressure is produced by electrically driven pumps and controlled via solenoids. [refer hydraulics.]
Endurance
Maximum time period (indicated in hours or days) that a vessel can operate un replenished while performing its intended role.
Engine control room
Space adjacent to engine room from where engine room systems may be controlled and monitored.
Engine room
Primary machinery space containing a vessel's propulsion prime movers.
Ergonomic
Permitting or accounting for efficiency of physical effort.
Even keel
Condition when forward and aft drafts are identical.
Factory ship
High endurance vessels designed for processing and packing whale or fish resources off-loaded by smaller whaling or fishing vessels.
Fender
Portable or fixed resilient protection against impact or chafing of areas of the upper hull.
Ferry
Vessel used to convey passengers and/or vehicles on a regular schedule between 2 or more points.
Flag State
The nation in which a vessel is registered and which holds legal jurisdiction as regards operation of the vessel, at home or abroad.
Flange
(1) Plate section at right angles to the web of a structural section.(2) Circular plate sections at pipe ends enabling a bolted connection.
Flare
Outward curvature or widening of the hull above the waterline present in the bow section (of a conventional bow) to avoid shipping water. (Angle of flare is measured from the vertical.)
Floor
Vertical transverse full-breadth plating between inner bottom and bottom shell plating.
Flush deck hatch
Hatch in a deck with no coaming.
Flush deck ship
Vessel having an upper deck extend continuously from bow to stern.
Foc'sle
[refer forecastle.]
Forebody
That part of a hull forward of amidships.
Forecastle
Raised and enclosed forward superstructure section of the hull.
Foredeck
Foremost section of exposed main deck.
Forefoot
The transitional region between stem and keel.
Fore peak tank
Tank (often for ballast/trimming) forward of the collision bulkhead.
Forest product carrier
Vessel designed for the transportation of processed timber with large hatchways simplifying stowage and transfer of cargo.
Forward
Towards or at the fore end of a vessel. (Abbr. Fwd or For'd.)
FPSO
Floating production, storage and offloading vessel.
Frame
Vertical structural component supporting and/or stiffening hull side plating and maintaining the transverse form.
Frame station(s)
Points at which transverse frames (or floors) are located, indicated on the baseline, numbered from zero at the aft perpendicular and terminating at or beyond the forward perpendicular. Stations abaft the aft perpendicular are numbered negatively.
Freeboard
Vertical measurement from the vessel's side amidships from the load waterline to the upper side of the freeboard deck.
Freeboard deck
The uppermost complete deck exposed to weather and sea, which has permanent means of weather tight closing of all openings in the exposed part, and below which all openings in the vessel's side sare fitted with permanent means of watertight closing.
Funnel
External fairing through which exhaust ducting is conducted.
GA
General arrangement.
Galley
Kitchen compartment aboard a vessel.
Gantry
High level structure supporting a traversing lifting appliance.
Garboard strake
Strake (line) of shell plating immediately adjacent to the keel(centerline) plating.
Gas carrier
Tanker designed for the transportation of liquefied gases.
General arrangement
Highly detailed plan drawings of the general layout of a vessel.
General cargo
Mixed packaged cargo other than bulk, gaseous or containerized.
Girder
(1) Longitudinal continuous member with a vertical web providingsupport of deck beams. (2) Longitudinal continuous verticalplating on the bottom of single- or double-bottomed vessels.
Gross registered tonnage
A formula-derived measure of the internal (enclosed) volume of a vessel less certain excluded spaces. (Stated in volumetric tons where 1 ton = 100 ft 3, 2.8317 m3.) (Abbr. grt.)
Guarantee period
Generally a 12-month period following formal delivery of a newly built vessel in which all defects arising in respect of the vessel's performance are the responsibility of the constructor.
Gunwhale
Timber capping the uppermost strake in a wooden vessel. Pronounce "gunnel".
Gusset plate
Bracket plate positioned in a horizontal or near-horizontal plane.
Handymax
Dry bulk carrier of 35 - 50,000 tons deadweight, popular for full efficiency, flexibility and low draft (<12 m).
Hatch
Opening in a deck providing access for cargo, personnel, stores, etc.
Hatch coaming
Raised rim of vertical plating around a hatchway to prevent entrance of water, the upper edge of which forms a sealing surface with the hatch-lid or cover.
Hawse pipe
Steel pipe duct through which the anchor cable is led overboard.
Head
(1) The bow of a vessel. (2) Term given to toilet facilities usually in the smaller craft context.
Heavy-lift vessel
Vessel designed specifically for the loading/discharge and transportation of very heavy cargoes.
Heel
Inclination of a vessel to one side. [Alt:list .]
Hopper barge
Barge designed with a single hopper type hold for the transport of bulk cargo and where the cargo is discharged (dumped) through the bottom of the vessel.
Hopper tank
Lower side ballast tank in a bulk carrier, shaped and positioned to create a hopper form to the cargo hold.
Hovercraft
Vessel designed to ride on a cushion of air formed by down-thrusting fans.
Hull
The main body or primary part providing global strength, buoyancy and hydrodynamic qualities of a vessel.
Hull girder
Combined hull structure contributing to the longitudinal global strength of a hull; treated as analogous to a girder.
Hydrofoil
High-speed craft with immersed foils for developing hydrodynamic lift at speed and a consequential reduction in resistance.
Hydrographic vessel
Vessel designed for the survey of seabed topography, currents, etc. relevant to marine navigation.
Hydroplane
Rotatable lateral fin providing vertical directional control for submersible craft.
Hydrostatic test
A pressure test employing a static head of water applied to various compartments or components of a vessel.
Ice breaker
Vessel designed for transiting sea ice or for the purpose of creating a channel in polar or winter ice for the passage of other vessels.
IMO
International Maritime Organization. UN body with the purpose of determining standards for all aspects of maritime industry imposed via Conventions, Codes, Protocols and recommendations which are adopted by resolution.
Inner bottom
[referdouble bottom] [Alt:tank top.]
Intercostal
Pertaining to structural members fabricated in separate parts which are aligned between continuous orthogonally intersecting members.
Jib
The arm or boom of a crane providing the reach (working radius).
Jumbo derrick
A derrick designed with a very high lifting capacity, often installed on heavy-lift vessels.
Jumboising
The conversion of a vessel to increase displacement by means of amid-length transverse cut and the installation of a new section.
Keel (plate)
Lowest longitudinal strake of plating along the bottom centerline of the hull.
Keel block(s)
Support block(s) located beneath the keel strake which are employed during dry-docking of a vessel.
Keelson
Longitudinal vertical member above the keel to which frames are attached. (Wooden construction.)
Knee
Outdated term for a bracket connecting a deck beam and side frame.
Knot
One nautical mile per hour (1.852 km/h, 0.5144 m/s).
Knuckle
Abrupt change in direction of hull surface or structure.
Landing craft
Flat-bottomed shallow-draft vessel designed to beach, with a bow and/or stern ramp for the transfer of cargo/payload.
Landing ship dock
Large naval vessel capable of carrying small landing craft and amphibious vehicles, dispatched via a floodable stern dock within the hull. (Abbr. LSD.)
Lifeboat
(1) Rigid-hulled survival craft deployed from a parent vessel. (2)SAR craft.
Lifting gear
The lifting equipment (i.e., cranes) for loading and discharging operations.
Lightening hole
Large hole cut in a structural member to reduce its weight.
Lightship
The vessel condition without any form of deadweight aboard (incl. fuel and ballast).
Limber hole
Small hole or slot cut in a structural member to permit the drainage of liquid.
Liner
Vessel (over 1000 grt) operating on a regular route between ports according to a particular schedule.
Lines plan
Plans indicating the hull form via the inclusion of waterlines, buttock lines and section lines shown on profile, plan and end views.
List
[referheel.]
LNG carrier
Vessel designed to transport natural gas in liquefied form.
LPG carrier
Vessel designed to transport petroleum gas in a form of butane or propane.
Longitudinal
Stiffener section used for plate stiffening aligned fore and aft.
Long ton
1.016 tons or 2 240 lb.
Machinery
Term covering main engines, auxiliary engine room machinery(e.g., pumps, compressors, etc.,) in addition to other installed plant (e.g., hydraulics, air-conditioning plant, lift machinery, etc.,) and deck machinery (e.g., mooring winches, windlasses, etc.).
Magazine
Internal space dedicated to the storage of munitions (shells, surface-to-air missiles, etc.) in a naval vessel.
Main deck
The main continuous deck or principal deck of a vessel
Main mast
The principal mast of a vessel.
Midships
Identical meaning(s) as amidships. [refer a midships.]
Midship section
Fully dimensioned sectional drawing of both hull and superstructure principal structural members at the midships station.
Mooring line
Ropes used for securing a vessel to shore bollards.
Moulded breadth
Greatest breadth of a hull measured between inner surfaces of the side shell plating.
Nautical mile
Unit of distance used in marine navigation. (International nautical mile = 1.852 km. 6076.12 ft, 1.1508 land miles.) The international nautical mile is equivalent to the average linear distance over 1minute of latitude arc at 45° latitude at sea level. (Abbr. nm.)
Net registered tonnage
A formula-derived measure of the internal (enclosed) volume in a vessel except spaces for machinery, navigation and accommodation. Net tonnage is always less than the gross tonnage.(Stated in volumetric tons where 1 ton = 100 ft 3, 2.8317 m3.)(Abbr. nrt.)
OBO
[Oil-bulk ore (carrier)] Vessel designed for the transportation of oil and/or bulk ores.
Offsets
Dimensional co-ordinates of a hull form, (referenced to the molded baseline, centre line and transom or AP) usually presented in tabular format.
Oil tanker
Vessel designed for the transportation of liquid hydrocarbons in bulk.
Pallet
A flat wooden or plastic platform onto which cargo may best rapped or lashed which simplifies handling via cranes and forklift vehicles.
Pallet carrier
Cargo vessel specially designed or adapted for the transportation of pallet-borne cargoes.
Panamax
Market category of vessels notionally at the dimensional limits for transiting the Panama canal.
Panting stringer
Horizontal deep-web side structural member used for strengthening bow structure prone to panting loads.
Parallel midbody
Midship portion of a hull within which the longitudinal contour is unchanged.
Passenger vessel
A vessel which carries more than 12 passengers.
Permanent ballast
Ballast material (usually solid material) which cannot be discharged or transferred by pump or by other means and which isused for attaining design draft and trim.
Pillar
Vertical column used to provide support to overhead deck structure.
Pintles
Vertical pins or bolts that serve as a pivot axis for a rudder.
Pipe layer
Vessel designed for the laying of pipelines on the sea bed.
Pitching
The oscillatory vertical motion of a vessel forward and aft in a seaway.
Platform deck
Deck which does not contribute to the overall longitudinal strength of a vessel.
Port
(1) Pertaining to the left-hand side of a vessel. (2) Term used for small windows in the marine context.
Poop deck
Raised short deck at the stern.
Port of Registry
Port in the country under whose flag a vessel is legally registered.
Port State Control
The examination of vessels for compliance with IMO Conventions and resolutions by state authorities.
Product tanker
Tanker designed for the transportation of a variety of hydrocarbon and chemical liquids with elaborate pumping and safety systems.
Propeller
Bladed propellers generating thrust via the creation of hydrodynamic lift forces in the direction of vessel motion.
Pusher tug
Tug designed for or engaged in pushing barges from behind.
Quadrant
Quadrant-shaped flat plate assembly mounted horizontally on top of a rudder stock for to which steering cables/chains are attached invintage vessels or small craft.
Quarter deck
Full-width raised hull section and deck extending from the aft shoulder to the stern.
Rake
Inclination from the vertical.
Railing(s)
Horizontal parallel tubing forming a safety barrier at edges of decks.
Ramp
Hinged platform permitting the loading/discharge of vehicles or movement between decks of vehicles aboard Ro-Ro vessels.
Range
The maximum distance a vessel is capable of attaining at its normal service speed without refueling.
Reach
The horizontal distance that a crane or lifting appliance can cover, measured from its axis of rotation.
Refrigerated vessel
Vessel designed for the transportation of refrigerated perishable cargoes in which the hold spaces are refrigerated and insulated.
Research vessel
Vessel designed for oceanographic or fisheries research.
Reserve buoyancy
Watertight volume of a vessel above the waterline.
RIB / RHIB
Rigid inflatable boat. / Rigid-hulled inflatable boat
Ride control
System(s) employing active hydrodynamic foils or deflectors installed to vary the attitude and vertical motions of the hull inhigh-speed vessels.
Rise of floor
[refer dead rise.]
Ro-Ro
Roll-on Roll-off. Method of cargo transfer between vessel and shore in which cargo is driven on/off using fork-lift, prime-mover/trailer combinations, etc
Roll
The transverse angular motion of a vessel.
Ro-Pax
Vessel designed with combined Ro-Ro and passenger capacity.
Rudder
Vertical control surface generating lift or reactionary forces for the directional control of a vessel.
Rudder stock
Vertical shaft connecting the rudder to the steering actuating system.
Sacrificial anode
Anode of zinc attached to the immersed parts of a hull to prevent deterioration of the hull steel through electrochemical reaction.
Salvage tug
Large powerful and maneuverable vessel designed to tow and assist vessels needing assistance due to grounding, sinking or fire.
Scantlings
Set of dimensions of a vessel's structure. (Structural dimensions.)
Section
(1) General term for an extruded or fabricated structural member.[Alt: profile.] (2) Transverse vertical plane through the hull perpendicular to the centerline.
Sheer
Upward longitudinal curvature of the upper deck.
Sheer strake
The uppermost strake (line) of side shell plating immediately adjacent to the strength deck.
Shell plating
Plating forming the hull side and bottom outer surfaces.
Short ton
American ton (2000 lbs). 0.9072 tons.
Shuttle tanker
Moderate sized tanker designed for the regular short-haul transport of oil between FPSO vessels or single point mooring buoys and coastal refinery terminals.
Skeg
Centerline (or twinned) fin-form continuation of the lower after body integrated into the hull primarily for directional stability and for support in dry-dock.
Sounding
Measured depth of liquid contents in a tank.
SPC
Self-polishing copolymer antifouling paint.
Specifications
Specified details relating to the performance, operating conditions, construction and quality of an engineered item.
Spreader
Beam or beam structure temporarily attached to and spanning the extremes of an item being lifted.
Stabiliser(s)
Protruding hydraulically-activated fin(s) which reduces roll amplitude through oscillatory action creating alternating lift vectors phased to counter roll.
Stability
The state or ability of a vessel afloat to recover equilibrium of trim and heel at sea.
Stanchion
Vertical structural supports of bulwarks and safety railings.
Starboard
Pertaining to the right-hand side of a vessel.
Static load
Structural loading of constant magnitude and application.
Steering flat
Compartment above the rudder(s) containing the vessel's steering actuation system(s).
Stem
The centerline apex area of the bow formed by curvature of plating or a solid bar section.
Stern
The aft most (rear) part of a vessel.
Stern door
Watertight horizontally-hinged door integral to the transom on astern-loading Ro-Ro vessel.
Stern ramp
Stern- (transom) mounted hinged platform located to permit the loading/discharge of vehicles aboard a Ro-Ro vessel.
Stern thruster
A propulsor installed near the stern to provide transverse a thrust component enhancing maneuverability.
Stern tube
Sealed and sleeved gland and bearing(s) for through-hull propeller shafting where the shaft penetrates the hull structure.
Stiffener
Linear structural section attached or integral to flat (planar)structure to prevent buckling and reduce bending deflections.
Strake
Continuous longitudinal line of plating.
Stringer
Longitudinal deep-web member used to provide support of web frames in the transverse framing system of hull side structure.
Stringer plate
[refer deck stringer .] [Alt:stringer strake.]
Strut
Support structure (with streamlined cross-section) for propeller shafting in a multi-screw vessel. [Alt: shaft bracket .]
Superstructure
(1) General term for sections of a vessel constructed on and above the upper or main decks of a vessel. (2) A more restrictive term under the International Convention on Load Lines, (1966):detached enclosed structure on the freeboard deck and extending transversely to within 4% of the breadth from the vessel's sides.
Swash bulkhead (plate)
Longitudinal or transverse perforated bulkhead (baffle) fitted in a tank to reduce the surging of the contents.
SWL
Safe working load; certified load limit applied to lifting appliance sand gear.
Tank top
[refer double bottom and inner bottom.]
TEU
Twenty-foot equivalent unit. A standard of measurement used in container transport based on the dimensions of a container 20 ft long × 8 ft wide × 8.5 ft high; (6050×2440×2590 mm).
Transom
Square-ended stern.
Transverse
(1) Alignment perpendicular to the centre plane of a vessel. (2)Deck beam.
Trawler
Fishing vessel designed for operation involving the towing of submerged nets.
Trim
The longitudinal attitude of a vessel, i.e., the difference between forward and aft drafts.
Trunk
Vertical space or passage formed by bulkheads or casings extending 1 or more decks providing access or through which piping or cabling may be conducted.
Tug
Small powerful and highly maneuverable vessel designed for towing, assisting and maneuvering larger vessels in port or restricted waterways.
Tumblehome
Inward curvature or slope of hull sides above the waterline.(Obsolete feature.)
Tween-deck
Intermediate deck within a cargo space above the lower hold and below the upper deck.
ULCC
Ultra large crude carrier. Tanker of deadweight greater than320,000 tons.
Ventilator
Installation or nacelle for the intake or exhaust of ventilation air for enclosed spaces.
Visor
Single-section outer bow door on a Ro-Ro vessel.
VLCC
Very large crude carrier. Tanker of deadweight between 160,000and 320,000 tons.
Void space
Enclosed space (often watertight) intentionally left empty; (e.g., cofferdam).
Watertight
Capable of preventing the ingress of water under a head of water likely to occur in the intact or damaged condition.
Weather deck
Uppermost hull deck exposed to the weather at all times.
Weathertight
Capable of preventing the ingress of water in any wind and wave conditions up to those specified as critical design conditions.
Web frame
Transverse side frame with deeper web, spaced at multiples of main frame stations for the provision of extra strength.
Winch
Geared rotary machine used for handling of lines, wires, etc.
Windlass
Winch designed for the raising and lowering of an anchor.
Wing tank
Ballast or cargo tank adjacent to the hull side.
Yacht
Private or charter vessel designed for pleasure cruising, racing, etc. propelled by wind or power.
Yield stress
Stress limit within a material at which plastic (permanent) strain commences under load.
Z-drive
Propulsion train configuration where the engine output and propeller shafts are horizontal and parallel and linked via anointer mediate vertical shaft.
Zinc primer
Common corrosion inhibiting primer used to coat bare steel prior to subsequent paint coatings being applied.
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