Glossary of terms

A

ABAFT – Behind or towards the stern.

ABEAM – At right angles to the boat.

AFT – See Abaft.

ALTO – Middle-level cloud base.

ALTOCUMULUS – Middle-level cloud.

ALTOSTRATUS – Middle-level cloud.

AMIDSHIPS – Centre of the boat.

ANCHOR – Device to moor the vessel in open water on the end of a line.

ANEMOMETER – Instrument to measure wind speed.

ANTICYCLONE – Meteorological term describing area of high pressure.

ANTIFOULING – Toxic paint to hinder weed and crustations from adhering to the hull

ATHWARTSHIPS – From one side of the vessel to the other.

B

BAILER – Scoop to remove water from inside the boat.

BALLAST – Additional weight carried in the hull to increase stability.

BEAM – Mid part of the boat, or measurement of maximum width of the hull.

BEAR AWAY – To turn the bows away from the wind.

BEARING – Compass direction.

BEAUFORT SCALE – Scale of wind speeds devised by Admiral Sir Francis Beaufort.

BECKET – A second eye or attachment point in a pulley block.

BIGHT – An open loop in a rope.

BLOCK – A pulley.

BLOCK AND TACKLE – A multi-purchase pulley system.

BOTTLE SCREW – Screw system used to tension rigging.

BOW – Front end of the boat.

BOLLARD – Vertical post on the quayside to make fast mooring lines.

BOWLINE – A knot used to tie a loop into the end of a rope.

BREAKWATER – Artificial wall around a harbour to break the force of the sea.

BROACH – When a boat slews out of control broadside to the wind and sea.

BULLSEYE – Wooden block or thimble with a hole drilled through it to take a rope to act as a block or stopper.

BULKHEAD – Transverse partition within the boat.

BUNG – Plug to block a drainage hole.

BUOY – Floating anchor, racing or navigation mark.

BUOYANCY – Power to float, having a density less than water.

BURGEE – Small flag flown from the masthead.

C

CAM CLEAT – Cleat with two spring-load cams to hold a rope.

CATAMARAN – Twin-hulled vessel.

CATHEDRAL HULL – Triple V-shaped hull

CAVITATION – Loss of propeller thrust caused by air bubbles forming on the blades.

CENTRE OF BUOYANCY – Point where the buoyant force of water acts on the hull.

CHART – Map of the sea.

CHINE – Line or crease in the hull. A hull built from flat sheets of plywood is known as a hard chine boat.

CIRRUS – High-level cloud.

CIRROCUMULUS – High-level cloud.

CIRROSTRATUS – High-level cloud with little form.

CLAM CLEAT – Cleat with no moving parts that secures rope within its grooved, V-shaped body.

CLEAR ASTERN / CLEAR AHEAD – One boat is clear astern of another when her hull and equipment in normal position are behind a line abeam from the after most point of the other boat’s hull and equipment in normal position. The other boat is clear ahead.

CLEAT – Fitting designed to hold a rope under tension without the use of a knot or hitch.

CLEVIS PIN – Pin that closes the fork of a rigging screw.

CLINKER CONSTRUCTION – Traditional form of hull construction where the planks overlap each other.

CLOVE HITCH – Common knot or hitch used to tie a rope to a ring or rail.

COAMING – Small upstanding ledge or breakwater across or around the deck to deflect water.

COCKPIT – Open area of the vessel.

COMPASS – Navigation instrument that points to the magnetic north pole.

CUMULUS – Low-level cloud.

CUMULONIMBUS – Low-level rain cloud.

CURRENT – A stream of water.

D

DEAD RECKONING – Estimated position on a chart.

DEADRISE – Angle between bottom and chine or corner of hull.

DEEP-V HULL – See V Hull

DEPRESSION – Meteorological term for an area of low pressure.

DEVIATION – Compass error influenced by magnetic materials nearby.

DINGHY – Small open boat without a fixed keel.

DISPLACEMENT – Volume/weight that a hull displaces in water.

DODGER – Canvas folding hood erected to protect the cockpit from spray.

DORY – Open, stable sea going dinghy or tender.

DOWNWIND – travelling in the same direction as the wind.

DRAFT – The depth of water that a vessel draws

E

EASE – To slacken a rope.

EBB – Outgoing tide or flow.

ECHO SOUNDER – Sonar instrument that measures the depth of water.

EDDIES – Area of reverse or back-running current.

ENSIGN – national flag flown from a staff on the stern of a vessel.

F

FAIRLEAD – A fixed lead to guide a rope or sheet and prevent chafe.

FAIRWAY – Main navigable channel.

FATHOM – Nautical unit of measure equal to 6ft (2m).

FENDER – Portable cushion or inflatable bladder to protect the hull from rubbing against another boat or a pontoon.

FIGURE-OF-EIGHT KNOT – Stopper knot.

FIX – A vessel’s position on a chart.

FLOOD TIDE – A rising tide.

FOLLOWING WIND – Opposite of headwind, when the wind comes from astern.

FOTHERING – The process of stuffing anything that comes to hand (e.g. sleeping bags) into a hole in the boat to stop water ingress.

FREEBOARD – Height of a boat’s side above the water.

FRONT – Meteorological term describing a distinct line of weather – cold front, warm front, etc.

G

GEL COAT – The smooth waterproof outer resin coating of a fibre-reinforced moulded hull and deck.

GNOMONIC CHART – Navigation chart on which great circle arcs are projected as straight lines.

GO ABOUT – To tack through the eye of the wind.

GPS – Satellite-based global positioning system.

GRADIENT WIND – Meteorological term caused by changes in barometric pressure. The greater the change in pressure, the steeper the gradient.

GREENWICH MEAN TIME (GMT) – Now referred to as Universal Mean Time (UTC).

GRP – Glass reinforced plastic.

GUNWALE – Outer strengthening piece around the top of the hull.

H

HALF HITCH – Temporary knot to attach a rope to a rail.

HALYARD – Rope or wire line to hoist a flag or sails up the mast.

HARD CHINE – Line where the flat sheets used to construct a hull meet.

HEADING – Direction that a boat is taking.

HEAD TO WIND – Boat facing directly into wind.

HEAVE TO – To bring the boat to a halt.

HEAVING LINE – Light throwing line with a weight on the end to drag a heavier line across to another vessel or to shore.

HELM – Rudder. Also short for helmsman or helmsperson.

HELP POSITION – The heat escape lessening postion (foetal) position to adopt should you fall overboard.

HITCH – Type of knot for attaching a rope to a rail or hoop.

HOIST – Vertical dimension of a flag or sail.

HOVE TO – See Heave to.

HUMP SPEED – The speed at which hydrodynamic forces lift a planing hull up on top of the water, reducing drag and wave-making resistance.

I

IMMINENT – Meteorological term for change in weather within six hours.

INGLEFIELD CLIPS – Interlocking C-shaped clips used to attach signal flags.

INBOARD/OUTDRIVE – Inboard engine attached to a transom mounted steerable drive.

ISOBAR – Meteorological term for line on weather map linking points of equal atmospheric pressure.

J

JACKSTAY – A strong webbing strap running the length of the boat on each side. By clipping the lifeline to this, it ensures that ‘Jack’ stays on the boat.

JETTY – A structure extending out from harbour wall or beach on which to moor a vessel.

K

KEDGE – Light, temporary anchor to hold the boat against an adverse tidal stream.

KNOT – Nautical mile per hour (1 nautical mile equals 1.15 statute miles or 1,852m). Also refers to a rope tie.

KNUCKLE – Sharp longitudinal line of distortion within the hull.

L

LAND BREEZE – Offshore wind, opposite to a sea breeze, that develops when the temperature of the sea is higher than the land.

LANYARD – Short length of cord used as a safety line.

LATERAL RESISTANCE – Ability of a boat to resist leeway or sideways force of the wind.

LATITUDE– lines around the globe parallel to the Equator.

LEAD – The direction that a rope is led.

LEE – Opposite to windward. The side away from the wind.

LEE SHORE – Shoreline which the wind is blowing towards.

LEEWARD – Opposite of windward; away from the wind.

LIFEJACKET – Buoyancy vest designed to keep a nonswimmer or unconscious person floating head up.

LOA – Length overall.

LONGITUDE – Vertical line around the globe that passes through both north and south poles.

LWL – Load waterline or length of waterline.

M

MAGNETIC POLE – Point on the Earth’s surface to which the needle of the compass points towards.

MAGNETIC VARIATION – Difference in angle between True North and Magnetic North.

MAMMA – Dark low-level rain cloud with udder-like shape.

MAST – A spar going straight up from the deck, used to attach sail and boom.

MARLING HITCH – Line of linked knots tying sail to a spar.

MERCATOR PROJECTION – Chart projection on which the lines of latitude and longitude are shown in parallel.

MERIDIAN – A line of longitude passing at right angles to lines of latitude.

MILLIBAR – Meteorological term for unit of pressure equal to 1/10000th of a bar.

MOULD – Male or female pattern for producing a plastic hull and other mouldings.

MULTIHULL – Generic term for a catamaran or trimaran.

MY – Prefix for name of vessel – Motor Yacht.

N

NAUTICAL ALMANAC – Annual publication listing tide tables, lights and radio beacons.

NAUTICAL MILE – 1 nautical mile equals 1.15 statute miles or 1,852m.

NEAP TIDES – Tides with the smallest rise and fall. Opposite of spring tides.

NIMBO – Rain cloud.

NIMBOSTRATUS – Middle-level rain cloud.

O

OAR – Wooden blade to row a boat with.

OBSTRUCTION – An object that a boat cannot pass without changing course substantially to avoid it, e.g. the shore, perceived underwater dangers or shallows.

OCCLUDED FRONT – Meteorological term to describe when a cold front overtakes a warm front.

OCCULTING LIGHT – Flashing navigation light where the period of light is longer than the period of darkness.

OFFSHORE WIND – Wind blowing seaward off the land.

OUTBOARD MOTOR – Self-contained propulsion system that bolts to the transom of a boat.

P

PAINTER – Mooring line.

PELICAN HOOK – Metal hook with a cam-action lock.

PFD – Personal flotation device such as a buoyancy aid or life jacket.

PINTLE – Male part of a pair of rudder hangings that fits into the female gudgeon.

PITCH – Theoretical distance that a propeller will move a vessel forward with one revolution.

PLANING – When a boat lifts its bows out of the water, and because of the reduced drag, then accelerates onto a planing attitude.

PORT – Left-hand side of a boat.

PULPIT – Safety guard rail around the bow.

PURCHASE – Mechanical advantage of the block and tackle or lever.

PUSHPIT – Safety guardrail around the stern.

Q

QUARTER – Sides of the boat aft, i.e. starboard quarter, port quarter.

R

RACE – Fast running tide or stream.

RADAR – RAdio Direction And Range – Electronic navigation system that sends out radio pulses and transcribes their range and position on a cathode screen.

RADAR REFLECTOR – Metal or electrical system that magnifies the radio pulse from a radar scanner and reflects it back to the cathode screen.

REEF KNOT – Knot joining two ropes together.

RHUMB LINE – Line on the Earth’s surface that intersects meridians at the same angle.

RIB – Rigid bottomed Inflatable Boat.

RIDING LIGHT – Navigation light displayed at night by a vessel when lying at anchor.

RIDING TURN – When a rope or sheet crosses under itself and jams, most often around a winch.

RIGGING – Standing wires that hold up the mast.

RIGGING SCREW – Screw to tension shrouds. Also known as a bottle screw.

RIGHT OF WAY – Term within Collision Regulations denoting a boat with right of way.

ROCKER – Fore and aft curve within the central underside sections of the boat.

ROUND TURN AND TWO HALF HITCHES – Knot used to attach rope to a rail or hoop.

ROWLOCK – Swivel fitting on the gunwale to support an oar when rowing.

RUBBING STRAKE – A strengthening strip secured to the gunwale as a protective buffer.

RUDDER – Moving foil to steer the boat with.

S

SEA BREEZE – Onshore wind opposite to a land breeze, that develops when the temperature of the land is higher than the sea.

SELF BAILER – Thru-hull automatic bailer that, once activated, allows the bilge water to flow out when the boat is planing at speed.

SEACOCK – A valve going through the hull, which can be shut from inside the boat.

SEXTANT – A navigational instrument used to determine the vertical position of an object such as the Sun, Moon or stars. Used with celestial navigation.

SHACKLE – Metal link with screw pin to connect wires and lines.

SHEAVE – The wheel within a block.

SHEEPSHANK – Knot used to shorten a rope.

SHEET BEND – Knot used to join two dissimilar sized ropes together.

SHOCK CORD – Elastic or bungee cord made of rubber strands.

SKEG – Short keel to protect rudder from grounding.

SLIP LINE – Temporary double line with both ends made fast to the boat that can be released from onboard and pulled in.

SNAP SHACKLE – Shackle with a secure locking mechanism instead of a pin.

SPONSON – Inflatable tube around a RIB or inflatable dinghy.

SPRING TIDE – Extreme high tide caused by the gravitational pull of the moon.

STAND-ON-BOAT – Right of way boat.

STEPPED HULL – Right angle step in the bottom of a planing hull designed to suck air into the boundary layer and reduce skin friction.

SQUALL – Sudden, short-lived increase in wind.

STARBOARD – Right-hand side of the boat.

STEERAGE WAY – Enough speed for the rudder to steer the boat.

STEM – Forward extremity of the boat.

STERN – Aft extremity of the boat.

STRATUS – Featureless low-level cloud.

STRATOCUMULUS – Low-level cloud.

STROP – A ring of rope or wire used to make up an attachment to a spar.

SWIVEL – Connector whose two parts rotate.

SYNOPTIC CHART – Weather map.

T

TACKLE – Multi-purchase system.

TAIL – The free end of a rope.

TALURIT – Swaged wire splice.

THWART – Transverse seat or plank amidships.

TIDAL STREAM – Flow of water caused by the rise and fall of tide.

TIDE – Six-hourly rise and fall of water caused by the gravitational pull of the moon.

TILLER – Arm of a rudder to control boat direction.

TRANSIT – Sighting two objects in line.

TRANSOM – Transverse aft end of a boat.

TRIM TAB – Adjustable elevator to adjust the boat’s fore and aft trim in the water.

TRUCKER’S HITCH – Knot used to tension a tie rope.

TRUE WIND – Direction and velocity of wind measured at a stationary position.

TUGMAN’S HITCH – Knot to secure towing strop to winch.

U

UNIVERSAL JOINT – Hinge that allows universal movement.

V

V HULL – Deep V hull has a deadrise of 18–25º.

VARIATION – Difference in angle between True North and Magnetic North.

VENTED HULL – See Stepped hull.

VMG – Velocity made good.

W

WAKE – Turbulence left astern of a moving boat.

WARP – Rope used to moor a boat.

WEATHER SHORE – Shoreline where the wind is blowing offshore.

WETTED SURFACE – Total underwater area of the hull.

WINCH – Capstan used to haul in an anchor cable.

WINDAGE – Drag caused by the boat and crew.

WINDWARD – Towards the wind; opposite of leeward.

WINDLASS – See Winch.

WORKING END – End of a rope used to tie a knot.