A glossary of marine technology and terminology

Aft At or near the stem of a vessel. (See also Forward.)

Ahull A sailboat is laying ahull when it is lying with all sails furled; associated with riding out gales.

Anchor rode The anchor line, rope or cable connecting the anchor to the vessel.

Apparent wind The direction of wind over the deck, calculated as the speed and direction of true wind plus the speed and direction of the boat. (See True wind.)

Astern Behind. To go astern means to reverse.

Beam The maximum width of a boat.

Bear away To alter course away from the wind.

Bearing An object's direction, expressed in compass degrees. Bearings can be true or magnetic.

Beating Sailing to windward (upwind), by tacking. Bight A curved or looped section of a rope. Also an indentation in a coastline.

Bitter end The end of a warp (rope) or chain.

Boom A spar, or pole. The foot of the mainsail is normally attached to a boom.

Bosun's chair A seat made of strong fabric or wood, used to hoist a person up the mast in safety.

Bow The forward section of a vessel.

Broach To slew in a following sea or wind. The boat rounds up violently and can heel to an alarming angle.

Broad reach A point of sail between a reach and a run. Bulkhead A structural, normally watertight partition running across the width of a vessel.

Burgee A triangular flag, often representing the yacht club to which the vessel belongs.

Close-hauled A sailing vessel is close-hauled when sailing as close to the wind as possible.

Cockpit Area towards the stern of a yacht from which the helmsman steers and the crew trims the sails.Cockpit instrumentation can be costly and sometimes it is a good idea to arrange a short term loan which can help cover the initial outlay.

Companionway The main entrance into a sea-going sailboat, usually via a hatch leading to a ladder.

Dead reckoning (DR) A method of navigating by recording the course sailed, leeway, speed, current drift, etc at regular intervals, starting from a known position (see also Observed position).

Displacement The weight of water a vessel displaces when floating normally. The weight of the displaced water equals the weight of the boat.

Downwind A point of sailing with the wind aft of the beam; the term is used for broad reaching or running.

Draught/draft The depth of a vessel under the water, from the waterline to the lowest point of the keel.

Ebb tide The tide is ebbing when it flows back from high to low water. (See also Flood tide.)

Ensign A flag flown to indicate a vessel's nationality.

Fathom A unit of measure, normally used with regard to water depth. One fathom = 1.8m (6ft).

Fix A fix is the vessel's position taken by obtaining accurate bearings by compass, sextant or other means.

Flood tide The tide is flooding when it rises from low to high water. (See also Ebb tide.)

Forward (`forrard') Towards the bow of a vessel.

Free wind Wind is aft of the beam, or running free.

Gimbals A swivelling device which enables a galley stove or compass card to remain level.

Go about To turn a sailing vessel through the headto-wind position in order to change tacks.

GPS Global positioning Systems, instruments which fix a craft's position by means of satellites.

Gunwale ('gunnel') The top edge of the hull where, in the case of a decked vessel, the hull meets the deck.

Gybe To change course by turning the stern through the wind. A fore-and-aft sail will be moved from the left side of the boat to the right, or vice versa.

Halyard A rope or wire used to hoist sails. Heading The compass direction in which the vessel is pointed.

Headsail A triangular sail set forward of the mast.

Heads The vessel's toilet(s).

Head-to-wind Pointed directly into the wind.

Heave to To stop the boat, normally by sheeting a headsail to windward.

Heel To lean over or list.

Helm A wheel or tiller by which a vessel is steered.

Holding ground Ground into which an anchor can dig.

In irons A sailing vessel is `in irons' when it is pointing directly into the wind and has lost its momentum.

Inshore Close to, or towards, the shore.

Isobars Lines on a weather map which join areas of equal barometric pressure.

Jury rig A temporary arrangement to replace damaged rigging and/or spars.

Knot Unit of speed. One knot equals a speed of one nautical mile per hour.

Lanyard A short length of line or rope for attaching items so they will not be lost overboard.

Lee The sheltered area downwind of a vessel (away from the direction from which the wind is blowing).

Leeward (`loo'ard') Towards the lee side; the direction to which the wind is blowing. (See also Windward.)

Life line A safety line fitted around the deck, or fore and aft, to prevent the crew from slipping overboard.

Log An instrument used to measure a boat's speed through water and distance travelled. Also a logbook.

Mainsail The principal sail of a sailboat, always aft of the main mast in a fore-and-aft rigged boat.

Mainsheet The rope, normally run through a series of blocks, that controls the trim of the mainsail.

Mark A fixed feature, either afloat or ashore, used as a guide for navigation.

Mayday A distress signal sent in a case of extreme emergency or when life is in danger.

Millibar Unit of barometric pressure used to measure atmospheric pressure (1000 millibars = 1 bar).

Nautical mile Unit of length equal to 1852m (6076ft). Also equal to one minute of latitude.

Observed position Position obtained by direct observation of features on a chart, or by observing celestial bodies by sextant. (See also Dead reckoning.)

Offshore At some distance from the shore.

Onshore On or towards land (e.g. an onshore breeze).

Painter A line used to tow or tie up a small boat.

Pilot A person qualified to navigate a vessel into or out of harbours or rivers; also a navigation reference.

Plot To mark a boat's position on a chart.

Port The left side of a vessel when facing the bow.

Port tack A yacht is on port tack when the wind comes over the port (left) side. (See also Starboard tack.)

Prow The front section of a vessel including the bow.

Pulpit A guard rail at the bow of a boat, usually built of stainless steel or aluminium tubing.

Pushpit A guard rail at the stern of a boat.

Race A rapid current, often caused by restricting the flow of water through a narrow channel.

Reach A point of sailing when the wind is approximately at right angles to the boat.

Reef To reduce the size (area) of a sail for operation in heavy weather.

Run To sail with the wind directly behind the centreline of the boat.

Running rigging The sheets and halyards which control the raising, lowering and set of the sails. (See also Standing rigging.)

Sea anchor A drogue-shaped anchor streamed in bad weather to slow the boat down.

Sheet The rope attached to the clew of a sail or, via a tackle. to the boom; it is used to control sail trim.

Spinnaker A large, normally lightly constructed, full headsail for downwind use; usually multicoloured.

Standing rigging The shrouds and stays that support the mast/s. (See also Running rigging.)

Stand on To maintain a course. A vessel with rightof-way is known as the stand-on vessel.

Starboard The right of a vessel when facing the bow.

Starboard tack A sailing vessel is said to be on starboard tack when the wind comes over the starboard, or right, side. (See also Port tack.)

Stern The aft section of a vessel.

Tack To turn a sailboat through the eye of the wind (to go from port tack to starboard tack and vice versa).

Trade wind A wind blowing obliquely towards the equator (from the northeast in the northern hemisphere, southeast in the south), between latitudes 30° N and S.

True wind Speed and direction of the actual wind as if the vessel is not moving. (See also Apparent wind.)

Upwind Sailing upwind of a vessel means sailing to windward of it. (See also Windward.)

UT Universal Time. Formerly GMT.

Veer A clockwise shift in wind direction (`back' is an anticlockwise shift in wind direction).

Warp A rope used to moor or secure a vessel. Weather side The upwind, or windward, side of a boat.

Windward Direction from which the wind is blowing; the weather side of a boat. (See also Upwind.)