Modern Ship & Shipbuilding Terminology

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Modern Terminology Listing divider
Allision: The act of a vessel striking a stationary vessel or a fixed object such as a wharf or quay; instead of collision which reguires two moving vessels. To allide.
Anchorage: Any location where a ship savely can and is allowed to drop anchor, most often a location within or just outside a harbour.
Anchor Bolster: A metal and often circular casting in the bow of a vessel through which the anchor chain passes. Also called bolster plate.
Anemometer: An instrument for measuring wind velocity. It normally consists of a rotating center shaft driven by four wind-catching cups or scoops, one on each end of two rods set at 90 degrees and connected to the top of the rotating shaft.
ASDIC: Acronym for Anti-Submarine Detection Investigation Committee. ASDIC stands for the first active-duty active-sonar system developed for the U.S. and Great Britain and widely used by the Allies for submarine detection in World War 2.
Barge: A long and often unpowered flatbottom cargo boat often towed or pushed by other craft or means. The term Barge is also used for relatively large and open pleasure boats used for public or private events.
Battleship: The largest class of warship, not counting carriers, heavily armoured and armed with the largest calibre guns.

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Battlecruiser: A warship with the firepower of a battleship and the lower armour protection of a cruiser for greater speed.
Beam Sea: Waves coming in to the side of a vessel, perpendicular to its course. Also Beam Seas.
Bermuda Rig: A fore-and-aft rig in which the mainsail is triangular in shape; also sometimes referred to as a Marconi rig. A Bermuda rig also includes one headsail.

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Bilge: Where the sides of a vessel curve in to form the bottom.
Bimini: A top or canopy for a boat, normally made of a material strung over a metal tubular frame, to provide shading from the sun.

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Binnacle: A nonmagnetic housing or stand for a ship's compass, usually located near the helm.
Bolster: A bag containing buoyant material on a small boat.
Booby Hatch: A raised hatchway covering.
Boomstop: A line to control a boom in a horizontal plane.
Boot Stripe: A painted stripe along the outside and just above the waterline of a ship's or boat's hull.
Bow Pulpit: A small plank-like platform or deck extension over the bow of a boat. Usually includes a U-shaped railing extending the boats railing over the platform forward. A bow pulpit may include navigation lights, cleats and anchor chute and rollers.

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Bow Thrusters: External or internal (tunnel or through-hull) thrusters located at the bow; propellers mounted transverse to the keel to provide lateral thrust for close-in maneuvering such as docking. See also stern thrusters.

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Breaming: To clean the bottom, or below the waterline hull of a vessel by applying heat. kills off crustaceans or any other creatures attached to the hull. To Bream.
Breast Line: A docking line to keep a vessel secured abreast (parallel) to a dock. A minimum of two are required; a forward breast line and an aft breast line.
Bridge: An upper deck or enclosed area or superstructure above the main deck of a ship from which command and control is executed.
Brig: A ship's jail or lock-up. Also a type of sailing vessel.
Bunker(s): A ship's fuel tank or tanks.
Bunkering: Fueling-up a ship or boat.
Burgee: A small flag displayed by a yacht to identify the boater's affiliation with a yacht club or any other boating organization.

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Caisson: A watertight chamber or compartment attached to the outside of a ship's hull below the water line so that repairs can be carried out. Also called cofferdam.
Careen: To turn a ship on her side for repairs or cleaning, or a ship leaning to one side while sailing in the wind.
Center of Buoyancy: The geometric center of a ship's underwater hull. When a ship rolls, the Center of Buoyancy will move as the underwater portion of the hull changes. When a ship rolls to starboard, it moves to starboard, and when the ship rolls to port, it moves to port. See also Metacenter.
Center of Effort: Theoretical center or focus of wind force on a single sail or the theoretical center of the sum of wind forces on multiple sails.
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Center of Gravity: The center of mass of the vessel. The location of the Center of Gravity is dependent upon the distribution of all weight within and on the ship including the ship itself, its cargo, supplies, armaments etc.
Chain Locker: A compartment for storing the anchor chain or cable, usually located near the bow of a vessel.
Chip Log: A piece of wood tied to a knotted cord. The speed of a vessel was measured by counting the number of knots passing over the stern while being timed. The nautical unit knot came from these equidistant knots tied in a rope. Also called hand log.
Chine: The line created by the intersection between the side and bottom of a flatbottom boat.
Chock: Deck fittings through wich mooring lines are passed. they can be of the closed, open, roller, and double roller variety.
Comber: A large rolling or breaking wave.
Conning Tower: A raised and armored observation post on a warship or submarine. On a submarine the conning tower often acted as an entrance to the submarine and as a compartment from which the periscopes were used to direct the boat and launch torpedo attacks.
Cowcatcher: A bulbous protrusion ahead of the bow and below the waterline of a ship to improve hull performance. Also Cow Catcher.
Cruiser: A fast warship with a large cruising radius, smaller than a battleship but larger than a frigate.

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Davit: A purchase onboard a ship or boat, such as a deck-crane, for suspending or lowering heavy equipment and objects on and off the vessel. The equipment to lower a life-boat or tender into the water, for example.
DDH: Destroyer-Carrying Helicopter(s).
Deadweight: Deadweight tonnage or DwT is the absolute maximum weight that a ship can safely carry when fully loaded. It includes crew, passengers, cargo, fuel, water, and stores. Often expressed in long tons or metric tons. Acronym: dwt. It is measured by measuring the displacement difference when the vessel is empty (or light) and fully loaded.
Demurrage: Charges required as compensation for the delay, or the detention of a ship beyond its scheduled time of departure.
Destroyer: A small, fast and highly maneuverable warship. A destroyer is normally lightly armoured but is often heavily armed with guns, torpedoes, depth charges, and a variety of guided missiles. Usually smaller than a frigate.
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Displacement Tonnage: The actual weight of a ship and its contents. One displacement ton, measuring the displacement of seawater while a ship is afloat, is equivalent to one long ton or about one cubic meter (35 cubic feet) of salt water.
Dodger: A cover attached to and over the top of the cabin and cabin entrance to shield the cabin from wind, rain and spray.

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Dorade: A yacht ventilation system named after the winner of the 1931 Transatlantic and Fastnet races: the Dorade. It consists of a single-chamber box with a baffle between the air intake and the interior air feed. Normally air is fed into the dorade through a cowl vent. The purpose is to allow air to enter while water is kept out and drained.
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Double Block: A tackle block with two sheaves located side by side.
Draft: 1. The depth of a ship in the water. The vertical distance between the waterline and the bottom of the keel or deepest part of a ship anywhere along its length, expressed in feet or meters. 2. The plans for construction of a ship, showing at least hull cross-sections and water-lines (horizontal sections).
Drillship: A vessel designed or modified to include a drilling rig and special station-keeping equipment.
ECDIS: Electronic Chart Display and Information System.
EPIRB: Emergency Position Indicating Radio Beacon. As the name implies, EPIRB is an emergency radio signal alerting others such as rescue to the vessel's position. Also referred to as EPERB, or Electronic Positioning Emergency Radio Beacon.
Fair Curves: Curves along the hull of a vessel that shown no discontinuities. Smooth curves, each segment of the curve is tangent to the next segment.
Fiddle Block: A tackle block with two sheaves of different diameter located one above the other.
Fin Keel: A protruding narrow but deep fin-like keel to give a shallow draft vessel better stability. Performance substitute for a longer or full length keel, often present on ocean-racing yachts.
Fish Plate: One of a pair of steel reinforcing plates bolted or welded to the sides of a beam or bulkhead joint.
Flotilla: A small fleet of ships or a fleet of small ships or boats.
Flotsam: Floating ship and cargo wreckage. Also previously called waveson. See also jetsam
Flybridge: The highest navigational bridge on a ship; a small and often open deck above the pilot house and main deck.
Freeboard: The distance from the waterline to the upper deck level, measured at the centre of a ship.
Frigate: A warship used primarily for escort duty. Most frigates are between 4,000 to 9,000 displacement tons and they are often larger than destroyers but smaller than cruisers. Earlier definition of frigate
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Gaff Preventer: A line to control a gaff in a horizontal plane.
Galley: The kitchen area aboard a ship. See also galley.
Gantline: Term for a rope passing through a block hung from a mast or other superstructure for the purpose of hoisting loads. Originally called girtline in the 18th century.
Gennaker: A headsail that is a hybrid between a genoa and a spinnaker, hence its name. A gennaker is used for sailing downwind.
Genoa: A headsail, similar to a jib, but larger. Part of a modern bermuda rig and a genoa partially overlaps the mainsail, sometimes even completely eliminating the mainsail.
GRT: Gross Register Tonnage is the cubic capacity of all enclosed spaces of a ship, more often used then NRT for calculating cargo capacity of a vessel. A Gross Register Ton is equal to 2.83 cubic meters or 100 cubic feet.
Gusset: A metal or wood brace reinforcing a joint where two or more structural parts meet, such as hull frame members.
Havener: A harbour master.
Headsail: Any sail set forward of the foremost mast of a sailing vessel.
Hooker: Slang for an outdated, obsolete, unwieldy, or just ugly vessel. Also a small fishing vessel using hooked (baited) lines. Also Hoeker (Dutch).
Hydrofoil: A wing like structure to create lift and raise the hull of a vessel above the water-surface for the purpose of increasing speed, smoothness and maneuverability by reducing drag and "skimming" the surface.
Inclinometer: An instrument to measure the degree of heeling of a vessel.
In Ordinary: When a commissioned naval vessel is placed in ordinary, it is 'mothballed' or stored for later use, later re-assignment or possibly final decommissioning.
Jetsam: All parts of a vessel and cargo deliberately thrown overboard, most likely in an emergency situation. See also flotsam.
Jiggermast: The fourth mast on a four-, five- or six-masted sailing vessel.
Kite: A free flying sail, similar to a spinnaker but different in that it is not attached to a mast and can be flown far out from a sailing ship or boat (like a kite).

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Courtesy of Garrett Freberg & KiteShip
Knot: A unit of measure used to express the speed of a ship in nautical miles per hour. One knot = 1.151 statute miles per hour.
Knuckle: Any abrupt change in direction or non-tangency in any external structure of a vessel, forming a 'knuckle-line' i.e. the line formed at the apex of the angle dividing the upper and lower part of the stern or counter.
Lane Meter: A unit of measurement for the deck capacity of a ship to roll on (and off) cargo such as containers, vehicles etc. A lane meter is generally accepted to be 2 meters wide and 1 meter long. Several practical variations exist to allow for clearance, anything from 2.5-3 meters wide and a minimum height of 4 meters.
Latitude: The distance north or south of the earth's equator. Both longitude and latitude are angles measured in degrees.

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Lazarette: A small storage space onboard a ship or boat, often located near or at the stern.
LBP: Acronym for Length Between Perpendiculars or horizontal distance between the main forward and aft perpendicular frame members. Sometimes the horizontal distance between stem and sternpost. For some vessels it may indicate the length of the hull along or at the waterline, also called Waterline Measurement.

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Levanter: A strong easterly Mediterranean breeze.
Lightship: An anchored ship acting as a floating lighthouse where building a lighthouse was not possible or impractical. Lightships would display a light at the top of a mast and in case of fog would sound a fog signal.

Example of a lightship
LOA: Acronym for overall length (Length Over All) or the extreme length of the ship along its centerline.

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LOD: Acronym for Length On Deck when specifying the length of a vessel.
Log Line: A line attached to a device such as a patent log or a knotted cord attached to a chip log trailing from the stern of a vessel for the purpose of determining the vessel's speed.
Longitude: The distance east or west from Greenwich, England. Both longitude and latitude are angles measured in degrees.

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Manifest: The official inventory of all cargo carried by a merchant ship.
MCR: 1. Machinery Control Room of a ship. 2. The Maximum Continuous Revolution of a ships engine.
Metacenter: The point of intersection (M) of the vertical line through the Center of Buoyancy (B - centroid of the displaced volume of water) and the centreline of the hull. To ensure that a ship will come upright when she is heeled (listing) the Metacentre must be above the Centre of Gravity (G) of the hull.
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The more distance between the Metacenter and Center of Gravity, also called the Metaheight, the more 'stable' the hull.
MLD: Marine (or Mariner) Licensing and Documentation.
Monkey Block A single block pulley equiped with a swivel.
Monkey Gaff A small gaff on merchant vessels for the display of signals at sea.
Monkey Rail: A small additional railing above the quarter rails of a vessel.
Moon Pool: The opening in the hull of an offshore drilling vessel through which drilling equipment passes.
Motion: A ship's motion is defined by heave (the rise and fall of the entire ship), pitch (rise and fall of the bow and stern), roll (tilting or heeling of a ship), surge (sudden forward movement or slowing), sway (sideways drift) and yaw (sudden change of direction). See image below for descriptive terms for ship motion and direction.
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Mudbox: Slang term for the water intake filter on a vessel's engine cooling system.
NRT: Net Register Tons, the true cargo capacity of a ship. NRT signifies the cubic below-deck cargo or passenger capacity used for the vessel's revenue generation only. For taxation purposes normally GRT is used. A Net Register Ton is equal to 2.83 cubic meters or 100 cubic feet.
Otter Board: A device creating a lateral spreading force on the mouth of a trawl net. Also called Otter door.
Out Haul: A line used to haul out a sail to a boom, yard, sprit or stay. Also outhaul.
Panama Lead: Tow fairleads at the bow and stern of a ship being towed through the Panama Canal.
Parbuckling: The righting of a sunken or stranded vessel, wich is inverted or on it's side, by rotating the vessel through applying leverage.
Passerelle: Gangplank. Entrance and exit to/from a vessel. Often a telescoping or folding walkway with railings.
Patent Log: A torpedo- or cigar-shaped device with rotating fins dragged on a (log) line from the stern of a vessel for the purpose of measuring the ship's speed. Also called screw log or taffrail log.
Plim: When wood swells (expands) in water. To plim. Plimed.
Plimsoll Line: A mark painted on the sides of (initially British) merchant ships indicating the draught levels to which the ship may be loaded under varying conditions. It was made compulsory in 1876 after too many ships were lost due to being overloaded. Named after Samuel Plimsoll, who was instrumental in the creation of the British Merchant Shipping Act one year earlier.
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Popple: Choppy seas or water.
RAS: Replenishment at sea. Term for a Navy ship being re-supplied with fuel and other stores by a supply-ship while at sea.
RIB: Rigid Inflatable Boat. A RIB provides buoyancy and stability through its inflatable collar, and performance and handling by having a rigid fiberglass or aluminium hull. RIB's are used for multiple applications such as military, rescue, sports and as yacht tenders.

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Ribband: A band or painted stripe along the outside of a ship's or boat's hull.
Rigging Monkey: A crew member performing rigging tasks aloft on a sailing ship or boat.
Running Lights: A term for the navigational lights required for when a vessel is in motion.
Sail: The superstructure of a submarine.
Scuttle: A circular port in the side of a vessel to admit light and/or air. A typical scuttle that comes to mind has a hinged circular brass or bronze frame with a thick glass window. It is secured by butterfly nuts. On the inside there can be a a deadlight, a hinged metal plate that can be lowered to cover the port in bad weather or when the ship must go dark. The term scuttle is also used to describe the deliberate sinking of a ship by opening ports and/or cutting holes into the hull.
Shaft Log: A metal casing on the inside of the hull of a boat, located directly over the propeller shaft hole.

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Sheet Anchor: A large anchor to be used in case of an emergency. Also called waist anchor.
SHEX: Shipping acronym for Sundays and Holidays EXcepted.
SHINC: Shipping acronym for Sundays and Holidays INCluded.
Snatch Block: A pulley block that can be opened on the side or top, or is open at the top (open face), to receive a line quickly rather then having to thread the line through.

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Sonar: Acronym for 'Sound Navigation And Ranging'. Sonar works by sending out sound waves in water and measuring distance by the time it takes for the sound wave to reach and bounce off (echo) an object (or the bottom) and return back to the sender. Originally developed for detecting submarines (the famous ping).
SOS: Ship's distress call, easier to transmit and a modified version of the original CQD (1904) Marconi code distress call. The Titanic alternated between transmitting CQD and SOS during her fateful sinking in 1912.
Spanker: A headsail set beside and to windward of a spinnaker when running downwind.
Spankermast: The fifth mast on a five- or six-masted sailing vessel.
Spindrift: Wind swept spray from the water surface. Also called spoondrift.
Spinnaker: A large, light and often brightly coloured headsail that is used when sailing downwind.
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Sponson: Any of a variety of flat structures that project outward from the side of a boat or ship, often a platform for armaments on larger vessels and used for stability on smaller boats and watercraft.
Spring Line: A docking line used to secure a vessel to a dock and prevent forward and aft motion.
Spurling Pipe: A steel pipe leading to the chain locker through which the anchor chain or cable passes. Also called Navel Pipe.
Squadron: A division of warships.
Squat: The amount the stern (rear end) of a boat goes lower down (draft) in the water when powered by its propellers in comparison to the amount of (draft) when the boat is not in motion.
SSB: Single Sideband Radio. Efficient AM radio system for long-range Naval and marine communication.
Stealer Plate: The first plate where two strakes of plates join into a single strake, near the bow or stern of a ship where the strakes converge. It's 'stealing' a strake, so to speak.
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Steerage: The most uncomfortable and cheapest accommodations on a ship, generally located well below deck. Historically meaning the aft or stern part of a ship below the great-cabin, since the steering cables, tiller and rudder were located there.
Stern Thrusters: External thrusters at the stern of a vessel; propellers mounted transverse to the keel to provide lateral thrust for close-in maneuvering such as docking. See also bow thrusters.

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Stuffing Box: A water seal fitting around a boat's propeller shaft and clamped to the inboard end of the shaft log, preventing water from entering a boat along the propeller shaft.

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Tanker: A vessel specifically constructed to carry liquid cargo, for instance an oil tanker.
Tender: A vessel attending to another vessel, in particular one that ferries supplies and personnel between ship and shore.

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TPI: Tons Per Inch immersion.
TPC: Tons Per Centimeter immersion.
Trawl Net: A fishing net that is towed either along the sea bottom (benthic trawling) or higher in the water (pelagic trawling). Also called dragnet.
Trawler: A fishing vessel of varying size using trawl- or dragnets.
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Trim Tabs: Two adjustable planes located at the transom of a boat. Hydraulically controlled, these planes (or tabs) can move up and down like the elevators on an airplane to lift or lower (trim) the stern.

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Trimaran: A fast sailboat with three hulls, normally having a larger main center hull and two smaller outrigger hulls called amas, one on either side, connected to the center hull by a framework of struts called akas. The words aka and ama originate from the original 'outrigged' East Indies Caracore or Proa.
Tug Boat: A relatively small but very powerful boat built for towing or pushing larger vessels and floating platforms.
Turnbuckle: A threaded fitting, used for adjusting rigging such as stays.
ULCC: Acronym for Ultra Large Crude (oil) Carrier. Tanker of between 320,000 and 549,999 DWT.
Umbrella: A protective cone-shaped shield overtop of a smokestack.
Vessel: A craft designed for water transportation.
VLCC: Acronym for Very Large Crude (oil) Carrier. Tanker of between 160,000 and 319,999 DWT.
Waft: A ships flag or pennant used to signal or indicate wind direction. Sometimes called waif.
Waterline: One of a number of (virtual) horizontal lines on the hull of a ship indicating the surface of the water when the ship is under various loads.
Weep: Water entering a wooden boat through the seams between the planks (leaking), often at launch. Then the planks plim and the weeping should be largely reduced, otherwise the sinking may start.
Welldeck: The space on a ship's weather deck lying at a lower level between a raised forecastle or poop and the bridge superstructure.
Windjammer: A variety of large and usually fore-and-aft rigged sailing vessels, used for pleasure cruises. Earlier definition of windjammer.
Wing: The name of that part of a ship's hold nearest to the side, away from the centre of the hold.
Wingsail: A composite rigid sail, or a 'soft' sail which can have its profile altered. Both versions are derived from aerospace technology and resemble and act very much like airplane wings. Benefits can include increased performance and ease of handling a large sail.
Zephyr: The west wind or a gentle breeze.
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Concept, content & Design: The Art of Age of Sail