Aft: At, or towards the stern of a vessel. (Opposite to forward.) Aft peak tank: A tank or compartment located abaft the aftmost watertight transverse bulkhead above propeller(s) and rudder (often used for fresh water or sea water ballast). Alleyway: A vessel's internal passageway or corridor. 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). 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, stabilising fins, shaft brackets, etc.
Astern: The backward direction in the line of a vessel's centreline. 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. 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.
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.
Boot-topping: Durable paint coating applied to a hull between the light and loaded waterlines. Bossing: Hydrodynamically faired outboard portion of hull plating surrounding and supporting propeller shafting. In a single-screw vessel the bossing is integral to a centreline 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 propulsor installed near the bow to provide a transverse thrust component enhancing manoeuvrability.
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.
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.
Cable layer: Vessel designed for the laying and repair of seabed telecommunication cables.
Cable locker: Compartment located forward to store the anchor cable. Camber : Transverse convex curvature of exposed decks to accelerate runoff. Cant frame: Hull side frame not aligned perpendicular to the vessel's centreline. 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.
Cathodic protection: Sacrificial or impressed current system of corrosion protection of hull, tanks and piping.
Container vessel: Vessel designed specifically for the transportation of standard size containers within the hull and on deck. Cellular container ship: Container vessel having specially designed vertical cell guides for the accommodation of standard size containers thereby precluding movement and lashing.
Cellular container ship
Centreline: The longitudinal vertical plane of a vessel. Chemical carrier (Tanker): Vessel designed specifically for the transportation of volatile,poisonous or corrosive liquids in specially constructed tanks.
Chemical carrier (Tanker)
Classification societies: Organisations which set standards for design and construction ofvessels 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. Counter: The overhanging stern section of a hull extending abaft the aft perpendicular or propeller aperture.
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 moulded lines of 2 adjacent decks. [Alt:deck interval.] Deep tank: Tank (usually for fuel) having significant depth (typically spanningmore than 1 deck interval). Derrick: Obsolete form of lifting appliance employing a hinged boom, king post(s) and running wires for control.
Diesel generator: Alternator (generator) directly powered by a diesel prime moverproducing AC electrical power.
Displacement: All-inclusive mass or weight of vessel measured in tonnes, 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 aftmost watertight bulkhead.
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 or lift 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 centreline, extending from the collision bulkhead to the engine room, through which ballast, bilge, fuel and hydraulic piping may be 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. Endurance: Maximum time period (indicated in hours or days) that a vessel can operate unreplenished while performing its intended role. Engine control room: Space adjacent to engine room from where engine room systemsmay be controlled and monitored.
Engine control room
Engine room: Primary machinery space containing a vessel's propulsion prime movers.
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. Flare: Outward curvature or widening of the hull above the waterline present in the bow section (of a conventional bow) to avoid shipping water. 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. 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.
Fore peak tank
Fore peak tank
Forest product carrier: Vessel designed for the transportation of processed timber with large hatchways simplifying stowage and transfer of cargo.
Forest product carrier
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 upperside of the freeboard deck.
Freeboard deck: The uppermost complete deck exposed to weather and sea, which has permanent means of weathertight closing of all openings in the exposed part, and below which all openings in the vessel's sides are fitted with permanent means of watertight closing. Funnel: External fairing through which exhaust ducting is conducted.
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 (centreline) plating. Gas carrier: Tanker designed for the transportation of liquefied gases.
General arrangement: Highly detailed plan drawings of the general layout of a vessel.
Girder: (1) Longitudinal continuous member with a vertical web providing support of deck beams. (2) Longitudinal continuous vertical plating 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 ft3 , 2.8317 m3.) (Abbr. grt.)
Handymax: Dry bulk carrier of 35 - 50,000 tonnes 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 downthrusting 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. 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 a mid-length transverse cut and the installation of a new section. 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.) Keel (plate): Lowest longitudinal strake of plating along the bottom centreline of the hull. 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, despatched via a floodable stern dock within the hull. 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. 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. 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. 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 1 minute of latitude arc at 45° latitude at sea level. 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. 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 moulded baseline, centreline 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 be strapped 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 is used 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 propulsor 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 in vintage 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 normalservice speed without refuelling. 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 perishablecargoes 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: Rigid inflatable boat.
Ride control: System(s) employing active hydrodynamic foils or deflectors installed to vary the attitude and vertical motions of the hull in high-speed vessels. Ro-Ro: Roll-on Roll-off. Method of cargo transfer between vessel and shore in which cargo is driven on/off using fork-lift, primemover/ 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 manoeuvrable 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 centreline. 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 tonnes. 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: Centreline (or twinned) fin-form continuation of the lower afterbody integrated into the hull primarily for directional stability and for support in dry-dock.
SNAME: Society of Naval Architects and Marine Engineers (USA). 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 centreline apex area of the bow formed by curvature of plating or a solid bar section.
Stern: The aftmost (rear) part of a vessel.
Stern door: Watertight horizontally-hinged door integral to the transom on a stern-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 manoeuvrability.
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. 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 appliances and gear.
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 centreplane 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 manoeuvrable vessel designed for towing, assisting and manoeuvring 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 than 320,000 tonnes.
USL: Uniform Shipping Laws (Australian federal code for the design, construction and stability of vessels.) 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 160,000 and 320,000 tonnes. 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 an intermediate vertical shaft.
Zinc primer: Common corrosion inhibiting primer used to coat bare steel prior to subsequent paint coatings being applied.
Added mass: The effective increase in mass of a hull, due to the entrained water, when in motion.
Added weight method: One method used in the calculation of a ship's damaged stability when it is partially fl ooded. It regards the water which has entered as an added weight, the basic hull envelope remaining. The other approach uses the concept of lost buoyancy. Aframax: A term used for the largest dry bulkcarriers. Air draught: The vertical distance from the summer waterline to the highest point in the ship, usually the top of a mast. Athwartships: Across the ship, at right angles to the centreline. Auxiliary machinery: Machinery other than the ship's main engines. Bale capacity: Capacity in hold to edge of frames and stiffeners; refl ects the stowage of bales or boxes. Cavitation: The formation of bubbles on an aerofoil section in areas of reduced pressure. Can occur on heavily loaded ship propellers.
Capesize: A term applied to large cargo vessels that cannot transit either the Panama or Suez Canals. They are usually of the order of 120 000-180 000 DWT. Capsize: A ship is said to capsize when it loses transverse stabilityand rolls over and sinks.
Centre of buoyancy (CB): That point through which the buoyancy force acts. It is defi ned in space by its longitudinal, vertical and transverse (respectively, LCB, VCB and TCB) position relative to a set of orthogonal axes. It is also the centroid of volume of the displaced water.
Centre of buoyancy (CB)
Centre of flotation (CF): The centroid of area of a waterplane. A small weight added, or removed, from the ship vertically in line with the CF will cause a change of draught without heel or trim. For a symmetrical ship the CF will be on the centerline and its position is given relative to amidships.
Centre of flotation (CF)
Centre of gravity (CG): The point through which the force due to gravity, that is the weight of the body, acts. Its position is defi ned in a similar way to the centre of buoyancyand is very important in calculations of stability.
Centre of gravity (CG)
Chain locker: Space or compartment forward of collision bulkhead in which anchor chain is stored.
Coefficients of fineness: These relate to the underwater form and give a broad indication of the hull shape. They are the ratios of certain areas and volumes to their circumscribing rectangles or prisms. Cross curves of stability: A series of curves showing how a ship's transverse stabilityvaries, with displacement, for a range of heel angles. Curve of statical stability. A plot showing how the righting lever experienced by a ship varies with angle as the ship is rotated about a fore and aft axis. It defi nes a ship's stability at large angles. Also known as the GZ curve. Drift angle: The angle between a ship's head and the direction in which it is moving. Floodable length: The length of the hull, at any point, that can flood without immersing the margin line. Important in studying the safety of ships. Formal safety assessment (FSA): A process for assessing the safety of a ship by studying the risks, their likelihood and consequences. GZ: The distance from the centre of gravityto the line of action of the buoyancy force. It is a measure of a ship's ability to resist heeling moments. Handysize:A term applied to bulk carriers of 40 000-65 000 DWT. Heave: The vertical movement of a ship, as a rigid body, in a seaway.
Hogging: A ship is said to hog when the hull is bent concave downwards by the forces acting on it. Hogging is the opposite of sagging.
Hold: That part of a ship where cargo or supplies are carried. Load line markings: Markings on the ship's side defi ning the minimum freeboard allowable in different ocean areas and different seasons of the year. Also known as Plimsol mark.
Load line markings
Loll: A ship which is slightly unstable in the vertical position will heel until the GZ curvebecomes zero. It is said to loll and the angle it takes up is the angle of loll. Longitudinal: A line in the fore and aft direction parallel to the centreline. Also refers to a longitudinal stiffener running parallel (or nearly parallel) to the centreline. Longitudinal centre of buoyancy (LCB): The fore and aft location of the centre of buoyancy.
Longitudinal centre of buoyancy (LCB)
Longitudinal centre of gravity (LCG): The fore and aft location of the centre of gravity. Longitudinal stability: The stability of a ship for rotation (trim)about a transverse axis.
Metacentre: The intersection of successive vertical lines through the centre of buoyancyas a ship is heeled progressively. For small inclinations the metacentre is on the centreline of the ship.
Metacentric diagram: A plot showing how the metacentre and centre of buoyancychange as draught increases. Metacentric height (GM): The vertical separation of the metacentre and the centre of gravityas projected on to a transverse plane.
Metacentric height (GM)
Midship area coefficient (CM): One of the coefficients of fineness. It is the ratio of the underwater area of the midship section to that of the circumscribing rectangle .
Midship area coefficient (CM)
Outboard: In a direction towards the side of the ship. Permeability: A measure of the free volume in a compartment defining the maximum amount of water that can enter as a result of damage. It will be less than unity because of stiffeners and equipment in the space. Plummer blocks: Supports for a shaft (such as the propeller shaft).
Plunging: A ship is said to plunge when it sinks bow or stern first through loss of longitudinal stability.
Pull-out manoeuvre: A manoeuvre used to demonstrate the directional stabilityof a ship. Safety of Life at Sea (SOLAS): A statutory regulation of IMO dealing with the safety of life at sea. Sagging: A ship is said to sag if the forces acting on it make it bend longitudinally concave up. Sagging is the opposite of hogging.
Sagging (right picture)
Ship routing: An attempt to guide a ship into areas where it will experience less severe weather and so reduce passage times. Slamming: The impact of the hull, usually the bow area, with the sea surface when in waves. Strip theory: A simplified theory for calculating ship motions. Suezmax: A term applied to cargo ships which are just able to transit the Suez Canal. Tailshaft: Aftermost section of the propeller shafting, carrying propeller.
Thrust block: A bearing arrangement, aft of the engine(s), by which the thrust of the propeller is transmitted to the ship.
Tonnage: A measure of the volume of a ship. In simple terms the gross tonnage (GRT)represents the total enclosed volume of the ship and the net tonnage (NT) represents the volume of cargo and passenger spaces. Tonnage is defined by internationally agreed formulae, and is used for dues for drydocking and pilotage and port and harbour dues etc. It should be noted that tonnage represents a function of volume and should not be confused with deadweight mass (tonnes), Lightship mass (tonnes) or displacement mass (tonnes). Tonnes per centimetre immersion (TPC): The extra buoyancy experienced due to increasing the draught by 1 cm. Torsional strength: The strength of the hull in resisting twisting about a longitudinal axis. Transverse planes: Vertical planes normal to the centreline plane of the ship. Transverse sections: The intersections of transverse planeswith the envelope of the ship's hull. Transverse stability: A measure of a ship's stability in relation to rotation about a longitudinal axis.
Anchor billboard: A structure on the deck of a vessel upon which the anchor is mounted when not in use.
Athwartship: Transverse or across a vessel from side to side. Ballast: Any substance, other than cargo, which is usually placed in the inner compartment of a vessel to produce a desired draft or trim.
Ballast tanks usage
Bell suction: The flared open end of a cargo pipeline which is situated at close tolerances to the bottom of a liquid cargo tank. Bilge: The lower inner space of a vessel's hull.
Bin: A walled enclosure built on the deck of a barge for the purpose of retaining cargo; also called a pen or cargo box. Bollard pull: The static pulling force of a tugboat measured in pounds. Bounding angle: A steel angle used for reinforcement at the junction of two steel plates. Bow: The forward or front end of a vessel.
Boxed end: The end of a barge which is squared for the full depth and width of the hull. Bridle: A V-shaped chain, wire, or rope attached to a vessel being towed to which the towline is connected.
Buck frame: A transverse truss. Bulkhead: An upright partition separating compartments.
Buoy: A stationary floating object used as an aid for navigation. Butterworth: A washing process used to gas free or clean a cargo tank, employing hot water or chemicals, sprayed through a patented rotating nozzle. Butterworth opening: a deck access opening with bolted cover, designed for butterworth operations. Camel: A pontoon used to fender between a vessel and a wharf.
Chock: A heavy metal casting through which lines may pass for mooring or towing.
Coils: A system of small diameter pipes installed inside a liquid cargo tank for the purpose of heating the cargo by means of hot oil or steam. Comehome: A convex curvature of the rake sides of a barge that produces a narrower beam at the headlog than the beam of the hull. Compartment: An interior space of a vessel's hull which is formed by bulkheads.
Deadman: An object, such as an anchor, piling, or concrete block, buried on shore. Deadweight tonnage: The cargo capacity of a vessel.
Deck button: A round, steel fitting affixed to a vessel's deck, designed to secure or guide cables for making up barge tows.
Deck lashing strap: A steel deck fitting normally used as an attachment for cargo tie down lines.
Dolphin: A cluster of piles driven into the bottom of a waterway and bound firmly together for the mooring of vessels.
Doubler: A steel plate installed on an existing structural plate and used as a strengthening base for deck fittings or as a repair of a damaged area.
Drip pan: An open container, located on deck under the ends of a pipeline header to retain cargo drippage. Dumb vessel: A vessel without means of self-propulsion. Dunnage: Any materials used to block or brace cargo to prevent its motion, chafing, or damage and to facilitate its handling.
Expansion trunk: A raised enclosure around an opening in the top of a liquid cargo tank which allows for heat expansion of the cargo.
Fairlead: A device consisting of pulleys or rollers arranged to permit the reeling in of a cable from any direction; often used in conjunction with winches and similar apparatus.
Fish plate: A triangular-shaped steel plate used to strengthen the connection between the towing bridle and the towing hawser.
Flame screen: A corrosion-resistant fine wire mesh screen used to cover certain openings on tank vessels to prevent the passage of flame into the tank. Freeboard: The distance from the waterline to the main deck of a boat or barge.
Freeing port: A large opening in the bulwark on an exposed deck of a seagoing vessel which provides for the rapid draining of water from that deck.
Gas free: The process of removing all hazardous gases and residues from the compartments of a vessel. Gasket: An elastic packing material used for making joints watertight. Gauge: A waterway marker which measures the level of the water in foot increments; also refers to the specific measure on the gauge. Gross tons: The volume measurement of the internal voids of a vessel wherein 100 cu. ft. equals one ton. Gunwale (gunnel): That part of a barge or boat where the main deck and the side meet. Gusset: A steel plate used for reinforcing or bracing the junction of other steel members.
Hawser: A large circumference rope used for towing or mooring a vessel or for securing it at a dock.
Headlog: The reinforced, vertical plate which connects the bow rake bottom to the rake deck of a barge or square-stemmed boat. Head of navigation: The uppermost limit of navigation from the mouth of a waterway. Hip towing (hipping): A method of towing whereby the vessel being towed is secured along-side the towboat
Horsepower: A standard unit of power which is often classified in connection with engines as brake, continuous input, intermittent, output, or shaft horsepower. Hull: The main body of a vessel which provides flotation. Integrated tow: A tow of box-ended barges which, as a complete unit, is raked at the bow, boxed at the intermediate connections, and boxed or raked at the stern. Keel: The lowest structural member of a ship or boat which runs the length of the vessel at the centerline and to which the frames are attached. Keel line: An imaginary line describing the lowest portion of a vessel's hull. Kevel (caval): A heavy, metal deck fitting having two horn-shaped arms projecting outward around which lines may be made fast for towing or mooring of a vessel hull.
Knot: One nautical mile per hour; used as a unit of measurement in expressing the rate of speed of seagoing vessels and the relative speed of water currents. Lightening hole: A hole cut in a plate or frame to reduce its weight without reducing its strength.
Limber hole: A drain hole near the bottom of a frame or bulkhead. Lines: The ropes or cables used on a vessel for towing, mooring, or lashing. Manhole: A framed opening in the deck of a vessel which primarily provides access for a man.
Manhole cover: A cover which seals a manhole and is usually designed to lock in place by twisting or using a centerbolt, studbolts, or dogs.
Mats: Slabs, usually constructed of timbers, which are placed on the deck of a vessel for the purpose of supporting and distributing the weight of heavy loads. Molded depth: The distance from the top of the keel to the top of the upper deck beams amidships at the gunwale.
Madeye: A steel fitting formed by a flat doubler plate and vertical steel member containing a circular opening. Pelican hook: A hinged hook held closed by a ring and used to provide the quick release of an object which it holds.
Pipe stanchion: A steel deck fitting consisting of a vertical post with angled bracket(s) on one side, welded to a doubler plate, which is welded on the deck of a vessel to restrain the movement of cargo, such as pipe. Plimsoll mark: The primary loadline mark which is a circle intersected by a horizontal line accompanied by letters indicating the authority under which the loadline is assigned.
PV valve: Pressure vacuum relief valve; a valve which automatically regulates the pressure or vacuum in a tank.
Reachrod: A steel rod which connects an above deck valve handle to a below deck valve. Rubrail: A protective railing on the hull of a vessel which is used for fendering. Running lights: Those lights required to be shown at night aboard a vessel or a tow while underway. Scow: Another term for a deck cargo barge having a hull design of a flat bottom, square ended rakes, and usually with a deck cargo bin. Scupper: A drainage opening cut flush with the deck of a vessel through the bulwark or bin wall.
Shackle: A U-shaped metal fitting used as a connection for line, cable, or chain and which has a pin secured through its end by a nut cotterpin, or screw threads.
Sponson: An addition to the side of a vessel that is outside its normal hull and which provides added deck space and/or greater flotation stability.
Spud: A steel or wooden post or pile that is placed vertically through a well in the hull of a vessel and which, when lowered to the bottom of the waterway, anchors the vessel. Spudwell: A casing which is attached to or passes through the hull of a vessel through which a spud is raised or lowered. Stern: The after or rear end of a vessel.
Sternlog: The reinforced, vertical shell plating which connects the stern rake bottom to the rake deck of a barge. Strake: A longitudinal or transverse row of steel hull plates. Turnbuckle: A connecting device usually used with cable or chain and which takes up slack by rotating on its screw threads.
Ullage opening: A small, covered opening in the top of a cargo tank through which measurements are made to determine the level of the liquid in the tank. VCG: Vertical center of gravity; an important computation used in the determination of the stability of a vessel with its cargo.
Horn cleat: A fitting, usually with two horn-shaped ends, to which lines are made fast. The classic cleat is almost anvil-shaped.
Kenter shackle: A detachable shackle which is used to join two forged anchor chain links together.
Eye plate: Fitting used for mooring arrangements.
Anchor stopper: A device to hold an anchor cable so as to prevent the anchor from running out or to relieve the strain at the inboard end.
EPIRB: Emergency Position Indicating Radio Beacon. EPIRB is a small hand-held battery-operated transmitter, actuated by water, for use in locating vessels in distress. EPIRBs are devices that trasmit a digital signal on the international distress signal frequency 406 MHz. Designed to work with satellites, EPIRBs are detectable by COSPAS-SARSAT satellites, which orbit the poles, and by the GEOSAR system which consists of GOES weather satellites and other geostationary satellites. There are two types of EPIRBs, Category I or Category II. Category I EPIRBs float-free and are automatically activated by immersion in water, and they are detectable by satellite anywhere in the world. Category II EPIRBs are similar to Category I, except in most cases they are manually activated, however some models can be automatically activated.
Various types of EPIRBs
SART: Search And Rescue Transponder. A SART is a self contained, waterproof radar transponder intended for emergency use at sea. The radar-SART is used to locate a survival craft or distressed vessel by creating a series of dots on a rescuing ship's radar display. A SART will only respond to a 9 GHz X-band (3 cm wavelength) radar. It will not be seen on S-band (10 cm) or other radar.
GMDSS: Global Maritime Distress Safety System. The GMDSS is an internationally agreed-upon set of safety procedures, types of equipment, and communication protocols used to increase safety and make it easier to rescue distressed ships, boats and aircraft. GMDSS consists of several systems, some of which are new, but many of which have been in operation for many years. The system is intended to perform the following functions: alerting (including position determination of the unit in distress), search and rescue coordination, locating (homing), maritime safety information broadcasts, general communications, and bridge-to-bridge communications. Specific radio carriage requirements depend upon the ship's area of operation, rather than its tonnage. The system also provides redundant means of distress alerting, and emergency sources of power.
Roller fairleader: A block, ring, or other fitting through which passes a line or the running rigging on a ship to prevent chafing.
Turnbuckle: a device that usually consists of a link with screw threads at both ends, that is turned to bring the ends closer together, and that is used for tightening a rod or stay.
SCBA: Self-Contained Breathing Apparatus. Such an apparatus consists of a suitable face mask, combined with a hose and source of fresh air, generally in the form of a tank of compressed air. The SCBA may be incorporated into a full-body protection suit. It is important to recognise that use of a SCBA is not trivial, and they are not designed to be worn by those without training.
Freefall lifeboat: Some ships have freefall lifeboats, stored on a downward sloping slipway, dropping into the water as holdback is released. Such lifeboats are considerably heavier to survive the impact with water. Freefall lifeboats are used for their capability to launch nearly instantly and high reliability, and since 2006 are required on bulk carriers that are in danger of sinking too rapidly for conventional lifeboats to be released. Tankers are required to carry fireproof lifeboats, tested to survive a flaming oil or petroleum product spill from the tanker. Fire protection of such boats is provided by insulation and sprinkler system, which has pipe system on top, through which water is pumped and sprayed to cool the surface. This system, while prone to engine failure, allows fireproof lifeboats to be built of fiberglass and not only metal.