Glossaire de termes nautiques


Altuglas search for term

Altuglas® is used to make windscreens and portholes in boats. It is a synthetic material and has an excellent mechanical resistance as well as withstanding UV rays. Altuglas® et Plexiglas® are brand names from the Arkema group.

Aluminium search for term

Aluminium is an extremely lightweight material and highly resistant to corrosion. Its softness means that it is of little use in boat construction, despite the obvious advantages of its weight. However, aluminium alloys are much stronger and are used commonly in the aircraft and nautical industries. Welding and riveting techniques have improved and hulls can be made out of large single sheets which are double-plated to increase solidity. Other equipment can also be in aluminium, such as seating, storage compartments and hatches.

Amps search for term

Amps are a unit used to measure the strength of an electric current. The intensity of the current is said to be the amount of electricity (ie. the number of electrons) which pass through a circuit in a given time.

Anemometer search for term

An anemometer is a device installed on the weather station of a boat which measures wind speed and wind pressure.

Antifouling search for term

Antifouling is a product applied to the hull of a boat and which is used to discourage the attachment of sea organisms such as plankton and seaweed spores. Heavy fouling can slow down the craft, make it less responsive, less easy to manoeuvre and less fuel-efficient.This treatment can also protect the hull from corrosion. It may contain chemicals which are harmful to sea life and so are subject to regulations concerning their usage.This treatment has to be renewed regularly.

Automatic pilot search for term

The automatic pilot is an electrical device used to keep the boat on a steady course without the need for human intervention.


Backstay search for term

The backstay is a part of the standing rigging. It is a cable running between the top of the mast and the transom and it controls the shape of the mainsail.

Ballast search for term

Sailing ships are equipped with sailing ballast, usually of metal, that is a weight which serves to counteract the lifting or tipping effect of the sails and prevent capsizing. They can also possess a sliding or pivoting fin found inside the hull which can be used during sailing or retracted totally or partially.

Bearing search for term

The attitude or bearing of a boat is its angle in relation to the wind direction.

Bimini top search for term

The Bimini top is an open-front canvas top which protects the occupants of the boat's cockpit against the sun's rays. It is easy to install and simple to fold away once the sun goes in. The Bimini top greatly increases on-board comfort.

Boom search for term

The boom is a spar attached by a pivot to the mast and which holds the bottom edge of a fore or aft sail. It is horizontal to the boat and enables the sail to be controlled and positioned effectively against the wind. Some sails are stored against the boom in more modern vessels. In some cases, mooring ropes are attached to the boom when the boat is at anchor.

Bouy rope search for term

A bouy rope links a bouy with a submerged object, usually an anchor.

Bouy-rope stripper search for term

A bouy-rope stripper is a sharp cutting tool fixed behind the propeller and whose purpose is to slice through all rope, cable, wire or netting which could become entangled in the propeller therefore causing considerable damage.

Bow thruster search for term

A bow thruster is a device set into the bow of a vessel below the waterline which enables the boat to be turned to port or starboard, thereby facilitating docking manoeuvers.

Bowsprit search for term

The bowsprit is a horizontal spar extending forward from the prow of a sailing vessel.
See: Martingale

Brake anchor search for term

A brake anchor is an anchor which has a tapered point and which is strongly weighted.

Britany anchor search for term

Made of highly resistant galvanised steel, the Britany anchor has a flat shank with no cage and is designed to bite into the seabed.


Capstan search for term

This is a circular drum allowing the links in a chain to be hooked on, in order to hoist the anchor with the windlass.

See: Windlass

Carbon fibre search for term

Carbon fibre is a strong, light, fibre-reinforced polymer containing carbon fibres. It has a high strength-to-weight ratio so is often used in naval construction but is relatively expensive.

Cathead search for term

The cathead (or davit) is a beam which extends horizontally out from the hull, where the anchor is fixed when it is raised.

Catwalk search for term

The catwalk is a narrow gangway linking the front to the rear of a boat.

Caulk search for term

The caulking of a vessel means the cleaning and repairing of the bottom of the hull below the waterline level.

Chart table search for term

The chart table is a table where maps and navigational charts are placed in order to calculate routes and itineraries.

Cockpit search for term

The cockpit is a small open-air area on the deck where the helmsman or the pilot control the movement of the boat.

Composite search for term

This is a polyester resin mixed with a matrix of glass or carbon fibres and has been widely used in the construction of pleasure boats since the 1970s. It is easy to maintain, strong, light and is often heated then melded into the appropriate shape. It can degrade on the surface and is sometimes coated for added protection.

Converter search for term

A converter is an electrical device which changes direct current (DC) into alternating current (AC).

Corian search for term

Corian® is a brand name for a solid surface material made of acrylic polymer and alumina trihydrate. It is non-porous, heat-resistant, shock-resistant, comes in two thicknesses (6 mm and 12 mm), is easy to clean and ideal for use in kitchen work surfaces or bathrooms.

CQR anchor search for term

A CQR anchor, or plough anchor, is so-called because of its resemblance to the agricultural plough. It has a hinged shank, allowing it to alter direction without being pulled out of the ocean bed.

Cutter search for term

A cutter is a single masted boat with a mainsail, a jib and a forestaysail, sometimes a sail boom and/or a square sail (in which case it is known as a topsail cutter).


Deck saloon search for term

The deck saloon is a living area on the deck of a vessel, with seats and benches. Only certain boat types will be big enough to have a deck saloon.

Depth sounder search for term

A depth sounder is an instrument used to measure the underwater depth by bouncing pulses of sound off the seabed and listening for echoes.

Dinghy search for term

A dinghy is a small open motor or rowing boat usually used for going between the shore and the main boat which might be anchored offshore. It's not usually longer than 2 to 3 meters in length.

Double keel search for term

A double-keeled ship is a sailing vessel whose keel consists of two parallel wings. It has the advantage of being able to run aground keeping the vessel upright, as long as there are no underground obstacles present (in which case there would be a risk of tipping or difficult grounding).

See: Keelboat

Downwind search for term

A boat is said to be sailing downwind when it is sailing in the same direction as the wind. The sails are let out all the way and the boat is running with the wind. She is said to be sailing 'close-hauled' when she is sailing as close to the wind as possible, ie. into an oncoming wind, and the sails are pulled in tight.

Draft search for term

The draft (or draught) is the perpendicular distance between the waterline and the lowest point of the hull, (the keel). It determines the minimum depth a boat can safely sail in. It can also be used to find out the weight of any cargo on-board. Sometimes a boat carries ballast in order to increase its draft and therefore its stability.


Epoxide search for term

Epoxides, or epoxy resins, are polymers formed from a resin and a hardener.
They have a wide range of uses including coatings, adhesives and composites such as carbon fibre and fibreglass.

They have excellent heat-resistance, mechanical and water-proofing qualities.
They are sold as repair resins for boats as they are known to have excellent adhesion to many materials including timber and they have very good gap-filling properties.

They can, however, deteriorate in UV light so are usually coated with varnishes which provide UV protection.

Eutectic plate search for term

This is a cooling system using a eutectic plate which is initially frozen then used on-board to slowly defrost and refrigerate its surroundings for several hours, until its eutectic liquid returns to its liquid state.


Fixed rigging search for term

The fixed rigging consists of the fixed spars, stays, spreaders, backstays, props and masts which hold up the boat's sails.

Flush deck search for term

A flush decker is a boat where the upper deck extends unbroken from stem to stern and where there is no raised forecastle and no lowered quarterdeck.

Fly bridge search for term

This is the highest point on a boat and consists of a platform equipped with a secondary set of navigation instruments.

FOB HP anchor search for term

The FOB HP anchor is made of galvanised or stainless steel with rounded flukes and an optimal angle of attack to increase its holding power.

Foot search for term

A foot is an imperial unit of length measurement, (abbreviated to ft or '), used in navigation and aviation, corresponding to 0.3048 m.

Foresail search for term

The foresail is the mainsail situated to the fore of the vessel between the bowsprit and the main mast.

Forestaysail search for term

The forestaysail is a triangular sail situated to the fore of the mizzenmast.

Fortress anchor search for term

The Fortress anchor is made of an aluminium alloy which is as strong as steel but only half the weight. It is corrosion-proof, sharp and used by the American navy and coastguard.

Full batten search for term

This large sail consists of 4 to 6 laths or battens, depending on the size of the sail, which extend its surface area away from the mast. It enables more comfortable, more efficient and faster sailing.

Furler mechanism search for term

A furler is a winding drum mechanism which enables the rapid unrolling or rolling up of sails. The sails cannot be used partially, they must either be fully deployed or fully stored away.


Gelcoat search for term

Gelcoat is a material used to provide a high-quality finish on the visible surface of a fibre-reinforced composite material. It is a kind of modified resin and is applied to the composite during its liquid state. It is often pigmented to provide a glossy and aesthetic finish, is durable, UV-resistant and a good electrical insulator.

Generator search for term

A generator is a device which produces electrical energy.

Gennaker search for term

The gennaker is a triangular sail which is a cross between a Genoa and a spinnaker and which is used for sailing downwind. It is attached to the bowsprit at the front.

Genoa search for term

The Genoa sail is situated to the front of the mast and extends past the mast and overlaps with the mainsail. It is used in weak to moderate wind conditions.

GPS search for term

A GPS or SatNav is a device which enables you to establish your boat's position and its route on a map, thanks to its satellite navigation system.

Grey water tank search for term

The grey water tank is a tank which collects waste water from showers, baths and washbasins. This water makes up nearly 40% of our daily consumption.


Halyard search for term

A halyard is a rope used to raise or lower a sail, flag or spar. The tightness of a halyard can determine the shape of the sail.

Hull below waterline search for term

This is the part of the hull below the waterline, including the keel and the sides of the vessel up to the floating line.


Jib search for term

The jib is a triangular staysail set at the front of the boat.


Keelboat search for term

A keelboat is a sailing ship with a keel that provides stability and ballast.

Ketch search for term

A ketch is a sailing vessel with two masts, a main mast and a mizzenmast situated aft of the mainmast. Both masts are rigged fore-and-aft, thus allowing long-distance sailing with better balance.

Kevlar search for term

Kevlar is a synthetic fibre which is either used on its own, spun into cables or made into sheets, or is used as part of a composite material. Kevlar is relatively light and is five times stronger than steel and is used in the construction of boat hulls and to reinforce sails.


Lazy bag & lazy jack search for term

The lazy bag is a cover used to store and protect the mainsail while it is packed away on the boom. The lazy jack is a system of cables that run between the main mast and each side of the boom and which guide the mainsail onto the boom when it is lowered and which facilitate its storage into the lazy bag.

Life raft search for term

A life raft is a small inflatable vessel used to evacuate the ship in case of an emergency. It is stored in a container and inflated automatically. It is obligatory to have one on-board ship when travelling internationally and during races and it must be checked regularly to ensure it is in a good state of repair.

Log search for term

This is a device used to measure and record the speed that the boat has travelled through the water. It takes into consideration the course and the time taken and calculates the speed in knots. 1 knot = 1 Nautical Mile per hour (1 Nm = 1852 m).

Lower lanyard search for term

The lower lanyards are cables which help to stabilise the mast and prevent it bending. They are fixed to the mast at the mast stars.


Martingale search for term

The Martingale is a strong cable or chain which links the tip of the bowsprit to its base and strengthens the bowsprit against the upwards pull of the mast stays.

Mast search for term

The mast is a vertical pole or spar which supports the sails. It can also hold electrical devices, aerials etc

Mast stars search for term

These are spars which make up part of the rigging and which are fixed to the mast horizontally and at differing intervals. They are used to spread out the lanyards.

Mer-veille search for term

The Mer-veille radar detector sounds an alarm when other ships' radar beams cross it. It detects where other vessels are and is ideal for avoiding collisions and increasing your comfort and security on-board.

Mizzen search for term

The mizzen is a lightweight sail attached to the mizzenmast and part of the rigging.


NAVTEX search for term

NavTex (which comes from NAVigational TELEX), is used for the automatic broadcast of local maritime information using radio telex (also known as Narrow Band Direct Printing, or NBDP). It transmits on a fixed international waveband: 518 kHz. A NAVTEX receiver consists of an integrated printer, display and keyboard. Once programmed with appropriate station codes and subject indicator characters, the unit is left unattended - messages are received automatically and printed on the integrated printer. An alarm is preset to go off whenever urgent messages are received.


Polyester search for term

Polyester is a kind of polymer made from either synthetic or naturally produced chemicals. Its uses range from clothing and upholstery to plastic bottles and yacht interiors. It is relatively inexpensive, resistant and light.

Prop search for term

A prop is a cable which is part of the rigging and which links the top of the mast to the front of the sailing ship.

Propeller shaft search for term

The propeller shaft connects the transmission inside the boat to the propeller blades outside the hull.


Reinforced concrete search for term

Reinforced concrete is concrete which has had reinforcement bars, plates or fibres placed in it to increase its strength. Hulls made of reinforced concrete are stronger than those made of steel, are durable and easy to maintain; they are relatively inexpensive and are usually coated with epoxy resin to increase their resilience.

Retractable centerboard search for term

A keelboat possesses a retractable centreboard, which can be pivoted out of a slot in the hull and into the water. It can be retracted if sailing in shallow water or when the boat is being towed. It can also move the centre of lateral resistance during sailing.

Rigging search for term

The rigging consists of both fixed and moveable (running rigging) spars and allows the sails to be raised, manoeuvered or lowered.

Roller reefing mechanism search for term

A roller reefing mechanism enables the halyards to be unrolled or rolled up, thus allowing the sails to be hoist or lowered.

Roof search for term

The roof is a structure erected over a small part of the boat's deck, usually covering the cockpit and the companionway.

Rope search for term

A rope is a vessel's cable.

Running rigging search for term

The running rigging consists of all control lines such as sheets and halyards used to control the sails.


S-drive search for term

The S-drive, or Saildrive is a kind of propeller which protrudes from the bottom of the hull (and not from the stern), there is no prop shaft therefore allowing more space inside the hull.

Saloon search for term

The saloon is the main interior living area on a boat.

Sandwich search for term

A sandwich compound is a substance consisting of two stronger and relatively thin outer layers or skins, enclosing a single softer interior layer. The compound formed is thus very strong and very lightweight.

Schooner search for term

A schooner is a type of ship with two masts, a mizzenmast and a main mast, both carrying fore-and-aft sails. The mizzzenmast is shorter or the same height as the main mast. These sailing vessels are known for their speed and windward ability.

Sea-Fire search for term

The Sea-Fire® brand is a world leader in marine fire suppression technology on-board ships.

Sloop search for term

A sloop is a single-masted ship, with a headsail attached to the fore to a fixed bowsprit and the mainsail held by the boom.

Solar panel search for term

A solar panel, or photovoltaic panel, consists of photovoltaic cells which generate electrical energy by using light energy from the sun. This is an environmentally-friendly way of providing your vessel with energy.

Solent search for term

The solent is a small inner forestaysail which can increase the sail surface area between the mast and the prop.

Spade anchor search for term

This anchor has an optimum angle when it lands on the seabed and is characterised by its concave flukes.

Spar search for term

A spar is a round pole of wood or metal, or of a lightweight material such as carbon fibre, which provides support for the sails.

Speedometer search for term

A speedometer is an instrument used to measure the speed of the vessel and this information is fed into the navigational equipment. Instruments vary from a propeller log, (which calculates the speed relative to the number of rotations of a small propeller set under the hull and which functions like an anemometer for wind speed), a Propeller RPM (which measures the rotation rate of the propeller on a motor boat), Doppler Shift (which measures the vessel's speed by bouncing pulses off the ocean bottom) and GPS (which uses satellites to measure a ship's speed and its position. Speed is measured in knots.

SSB search for term

SSB (or Single Sideband modulation) is a way of transmitting via radio using only one of the AM sidebands, (the main carrier band and the other sideband having been removed). Its advantage is that all the energy used to transmit is concentrated in this single waveband; long distances can therefore be covered and signals can be clearly received. SSB is therefore ideal for maritime, military, aeronautical and amateur radio uses.

Stainless steel search for term

On certain pleasure boats the hull may be made of stainless steel. However, its use is uncommon due to its high cost. See: Steel, Aluminium, Wood, Composite, Epoxide, Reinforced concrete, Carbon fibre, Kevlar, Polyester, Sandwich

Stay search for term

A stay is a cable running from the mast or the spars to the U-bolts situated at the bow or stern of a ship and serves to support the mast and rigging.

Steel search for term

Nowadays most hulls are made of steel. It is the strongest and most hard-wearing material available and has a particularly high shock-resistance quality. See: Stainless steel, Aluminium, Wood, Composite, Epoxide, Reinforced concrete, Carbon fibre, Kevlar, Polyester, Sandwich

Stern search for term

The stern consists of a strong piece of wood or metal which encloses the end of the hull and which holds the rudder fittings. Often called the poop, it is situated at the rear of the boat.

Storm jib search for term

The storm jib is a foresail placed to the fore of the mast. It is smaller and more tightly set than a genoa and is made of stronger, thicker material in order to resist rough weather conditions.


Through-hull tube search for term

This is a tube which passes through the hull and which contains the navigational sensors.

Tri-radial spinnaker search for term

The tri-radial spinnaker is a light foresail which is fixed at its topmust point to the mast as well as at its two bottom corners, causing wind force to hollow out the sail along its seams. This sail is light and used for sailing downwind.

Two-blade folding propeller search for term

This is a two-bladed propeller developed for sailing ships and which can be folded during sailing, therefore reducing drag. The blades are symmetrical and do not cause vibration in either forward or reverse gears. It greatly increases the efficiency of the boat and avoids snagging nets or seaweed.


U-bolt search for term

A U-bolt is made of stainless steel and is fixed to the deck or the hull of the sailing vessel and is used to attach the spar cables (for the mast, rigging, stays etc...)


Valve search for term

A valve is a type of tap used for regulating the flow of liquid in a pipeline. They usually screw or unscrew open and closed and may be made of plastic or metal. It is advisable to open and close them regularly to stop them seizing up.

VHF search for term

VHF (or Very High Frequency) is the radio frequency from 30 MHz to 300 Mhz. VHF radios are the most common communications radios found on boats but their range is limited to line-of-sight between the transmitting station and the receiving station. It is used for navigation, by aircraft and the military.


Waste-water container search for term

The law states that vessels equipped with a toilet must recuperate all waste water and store it inside a specially adapted recipient: a waste-water container.

Water maker search for term

A water maker produces water fit for drinking, for showering, in the galley and for cleaning. It is an essential piece of on-board equipment.

Waterjet search for term

A waterjet is a pumping system which propels the boat by pumping in water from under the boat then expelling it at high speed behind the boat. It is particularly efficient at high speed (more than 25 knots) and is most often used in high-speed ferries or sea scooters.

Watt search for term

The Watt (symbol W) is an international unit of measurement which measures the power of an electric current.

WC with holding tank search for term

A holding tank is a kind of reservoir which contains sewage from the toilet until it can be emptied at an appropriate treatment facility.

Winch search for term

A winch is a manual or electric device used to wind up or wind down the sails. It consists of a spool on a vertical axis and a crank.

Wind vane search for term

A wind vane is a device which determines the direction that the wind is blowing and is used by the autopilot or pilot to set a heading.

Windlass search for term

The windlass is a winch used to hoist and lower the anchors. It has a racheted wheel that hooks into the chain links and which rotates about a horizontal axis.

Wood search for term

Historically, wood was the primary material used in boat construction, but it is still used even now. However, the laminated products available now are highly resistant and as good as, if not better than, any other composite material. Plywood is also used, particularly in boats of medium length (12 – 13 m), as it is solid but only of average strength and not particularly shock-resistant.


Yard search for term

A yard is a cylindrical spar, metal or wooden, which is fixed or hinged to the mast and which extends outwards horizontally at different heights and which supports and extends the sails.


Z-drive search for term

The Z-drive is a kind of marine propulsion system, also know as an azimutal thruster. The propeller, situated below the hull, is shaped so that it can turn through 360° and thus allow rapid changes of direction. It is usually fitted to vessels requiring precise manoeuverability.