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Glossary of Nautical, Rigging and Sailing Terms  
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A

Aback
Wind on the wrong side of the sails.

Abaft
Toward the rear of the boat, behind the boat.

Abeam
At a right angle to the length of the boat.

Abreast
Off the side, even with the boat.

Accidental jibe
An accidental jibe happens when the boat is steered or the wind shifts such that the stern of the boat accidentally passes through the eye of the wind. This causes that main boom to swing violently to the other side of the boat. Without proper preparation when jibing, the force of the boom's motion can be destructive, injuring the crew and damaging equipment. In strong winds and on large boats this force can dismast the boat and seriously injure crew members hit by the boom. Sometimes a preventer is used to reduce the possibility of an accidental jibe.

Admeasure
Formal measurement of a boat for documentation.

Admiralty law
The "law of the sea".

Adrift
Floating free with the currents and tide, not under control.

Aerodynamic
Having a shape that that is not adversely affected by wind flowing past it.

Aft, after
Toward the stern (rear) of the boat.

After bow spring line
A mooring line fixed to the bow of the boat and leading aft where it is attached to the dock. This prevents the boat from moving forward in its berth. Its opposite, the forward quarter spring line, is used to keep the boat from moving aft in its berth.

Agonic line
The line around the earth where there is no magnetic deviation between magnetic north (as measured by a compass) and true north.

Aground
When a boat is in water too shallow for it to float in, i.e: the boat's bottom is resting on the ground.

Aid to navigation
Any fixed object that a navigator may use to find his position, such as permanent land or sea markers, buoys, radio beacons, and lighthouses.

Alee
To the leeward side (downwind).

Aloft
Above the boat, in its rigging.

Amas
The outboard hulls of a trimaran.

Amidships
In the center of the boat.

Anchor bell
A bell required to be rung at certain times when at anchor during fog, according to the navigation rules.

Anchor bend
A type of knot used to fasten an anchor to its line.

Anchor chain
A chain attached to the anchor. The chain acts partially as a weight to keep the anchor lying next to the ground so that it can dig in better. Chain is also not damaged as much as line when lying on rocks. The weight of the chain also helps to absorb changes in the boat's position due to waves.

Anchor light
A white light, usually on the masthead, visible from all directions, used when anchored.

Anchor locker
A locker used to store the anchor rode and anchor.

Anchor rode
The line or chain attached to the anchor and secured to the boat.

Anchor roller
Also called bow roller. A fitting with a small wheel that allows the anchor and chain to roll over when dropping or raising the anchor. Some anchor rollers also have a provision to store the anchor as well.

Anchor watch
A watch kept when the boat is at anchor in case the anchor starts to drag.

Anchor windlass
A windlass used to assist when raising the anchor.

Anchor
(1) A heavy metal object designed such that its weight and shape will help to hold a boat in its position when lowered to the sea bottom on a rode or chain. See kedge, lightweight, mushroom, and plow anchors.
(2) The act of using an anchor.

Anchorage
A place where a boat anchors, usually an established and marked area.

Anemometer A device that measures wind velocity. Aneroid barometer
A mechanical barometer used to measure air pressure for warnings of changing weather.

Antifouling
Poisonous paint used on the bottom of the boat to prevent barnacles and other organisms from growing on the ship's bottom.

Apparent wind
The apparent direction of the wind, which is affected by a boat's motion. The apparent wind is only the same as the true wind if the boat is stopped.

Astern
Toward the stern of a vessel, or behind the boat.

At the dip
A flag hoisted half way up a flagpole. Also see close up.

Athwart, athwartships
Lying along the ship's width, at right angles to the vessels centerline.

Atmospheric pressure
Also called barometric pressure. The weight of the atmosphere, an average of 1013.2 millibars or 29.2 inches of mercury at sea level. Measuring the changes in atmospheric pressure can help predict weather.

Autopilot
A device used to steer a boat automatically, usually electrical, hydraulic or mechanical in nature. A similar mechanism called self steering gear may also be used on a sailing vessel.

Auxiliary
A second method of propelling a vessel. On a sailboat this could be a engine.

Aweigh
To raise an anchor off the bottom.

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B

Backing (wind)
The changing of the wind direction, opposite of veering. Clockwise in the southern hemisphere, counter-clockwise in the northern hemisphere.

Backsplice
A method of weaving the end of a rope to keep it from unraveling.

Backstay
A stay (line or cable) used to support the mast. The backstay runs from the masthead to the stern and helps keep the mast from falling forward.

Backwinded
When the wind pushes on the wrong side of the sail, causing it to be pushed away from the wind. If the lines holding the sail in place are not released, the boat could become hard to control and heel excessively.

Bail
To remove water from a boat, as with a bucket or a pump.

Ballast
A weight at the bottom of the boat to help keep it stable. Ballast can be place inside the hull of the boat or externally in a keel.

Bar
A region of shallow water usually made of sand or mud, usually running parallel to the shore. Bars are caused by wave and current action, and may not be shown on a chart.

Barge
A long vessel with a flat bottom used to carry freight on rivers. Barges are usually not powered, being pushed or towed by a tugboat instead.

Barograph
An instrument used to keep a record of atmospheric pressure, such as on a paper drum.

Barometer
An instrument used to measure atmospheric pressure, usually measured in inches of mercury or millibars. Inches of mercury are used because some barometers use the height of mercury in a sealed tube as a measuring device.

Barometric pressure
Atmospheric pressure as measured by a barometer.

Batten down
Also batten the hatches. To put away all loose objects on the ship and to close all openings, such as ports and hatches, in preparation for heavy weather. Hatches used to be secured with battens.

Batten pockets
Pockets in a sail where battens can be placed to stiffen the sail.

Batten the hatches
Also batten down. To put away all loose objects on the ship and to close all openings, such as ports and hatches, in preparation for heavy weather. Hatches used to be secured with battens.

Batten
(1) A thin strip of hard material, such as wood or plastic.
(2) Battens are attached to a sail to stiffen it to a more preferred shape. They are placed in pockets sewn into the sail called batten pockets.
(3) Battens also used to be used to secure hatches.

Bay
An enclosed body of water with a wide mouth leading to the sea.

Beam reach
Sailing on a point of sail such that the apparent wind is coming from the beam (side) of the boat at about a 90° angle. A beam reach is usually the fastest point of sail. A beam reach is a point of sail between a broad reach and a close reach.

Beam
(1) The widest part of a boat.
(2) Abeam, at right angles to the length of the boat.
(3) Sturdy wooden timbers running across the width of a boat . Used to support the deck of a wooden boat.

Bear away, bear off
To fall off. A boat falls off the wind when it points its bow further from the eye of the wind. The opposite of heading up.

Bearing
The direction of an object from the observer. "The lighthouse is at a bearing of 90 degrees."

Beat
To sail on a tack (direction) toward the wind.

Beating
Tacking. To sail against the wind by sailing on alternate tacks directions).

Beaufort wind scale
A method of measuring the severity of the force of wind, named after Admiral Beaufort who created the system. 0 is no wind, whereas 12 would be a hurricane.

Becket
A loop at the end of a line.

Bedding compound
A material used to join two objects completely. Usually used to create a water tight or very secure joint.

Bend on
To attach a sail and prepare it for use.

Bend
A type of knot used to connect a line to a spar or another line. Also the act of using such a knot.

Berth
(1) A place for a person to sleep.
(2) A place where the ship can be secured.
(3) A safe and cautious distance, such as "We gave the shark a wide berth."

Bight
The center of a slack line. (i.e: where it sags). Also a small indented curve in a shoreline.

Bilge pump
A mechanical, electrical, or manually operated pump used to remove water from the bilge.

Bilge
The lowest part of the interior of the boat where water collects.

Bimini
A cover used to shelter the cockpit from the sun.

Binnacle
The mount for the compass, usually located on the wheel's pedestal.

Binocular
A pair of small telescopes, one for each eye, used to magnify distant objects.

Bitt
A sturdy post mounted on the bow or stern to which anchor or mooring lines may be attached.

Bitter end
The end of a line. Also the end of the anchor rode attached to the boat.

Block and tackle
A combination of one or more blocks and the associated tackle necessary to give a mechanical advantage. Useful for lifting heavy loads.

Block
One or more wheels with grooves in them (pulleys) designed to carry a line and change the direction of its travel. A housing around the wheel allows the block to be connected to a spar, or another line. Lines used with a block are known as tackle.

Boarding ladder
A ladder used to board the vessel. Boarding ladders may be designed to be useful from either the water or a dock and are usually stowed when not in use.

Boarding wave
A wave that breaks over the deck of the boat.

Boat hook
A pole with an attached hook at the end, used for either retrieving objects or fending them off.

Boat
A small vessel used to travel on the water, powered either by wind, power or oars. Also any small vessel carried on a larger ship. Also an abbreviation for; “Break Out Another Thousand”.

Boatswain
Also bosun, bos'n, bo's'n, and bo'sun, all of which are pronounced bosun. A crew member responsible for keeping the hull, rigging and sails in repair.

Bollard
A large pillar, usually made of concrete or steel, to which a boat's mooring lines can by tied.

Bolt rope
A line (rope) sewn into the luff of a sail. The bolt rope fits in a notch in the mast or other spar when the sail is raised.

Boom vang
Any system used to hold the boom down. This is useful for maintaining proper sail shape, particularly when running or on a broad reach.

Boom
A spar that is used to secure the bottom of a sail, allowing more control of the position of a sail.

Bosun’s chair
A chair traditionally made from a plank and rope, used to hoist workers aloft to maintain the rigging.

Bosun’s locker
A locker where tools for maintaining the deck, rigging and sails are kept.

Bosun
Also boatswain, bos'n, bo's'n, and bo'sun, all of which are pronounced bosun. A crew member responsible for keeping the hull, rigging and sails in repair.

Bow & beam bearings
A set of bearings taken from an object with a known position, such as a landmark, to determine the ship's location. A type of running fix.

Bow
The front of the boat.

Bowditch
A reference book named after the original author, Nathaniel Bowditch. Updated versions contain tables and other information useful for navigation.

Bowline
A knot used to make a loop in a line. Easily untied, it is simple and strong. The bowline is used to tie sheets to sails.

Bowsprit
A pole extending from the bow of a boat. The bowsprit is used to attach the headstay forward of the front of the boat's deck. This allows added sail area for the head sail.

Brace
A guy. A line used to control the movement of the object at the other end, such as a spar.

Braided line
A method of making lines that allows for greater strength and durability when using modern materials.

Breakers
A wave that approaches shallow water, causing the wave height to exceed the depth of the water it is in, in effect tripping it. The wave changes from a smooth surge in the water to a cresting wave with water tumbling down the front of it.

Breaking seas
With sufficiently strong wind, large waves can form crests even in deep water, causing the wave tops to tumble forward over the waves.

Breakwater
A structure build to improve a harbor by sheltering it from waves.

Breast line
A line attached laterally from a boat to a dock, preventing movement away from the dock.

Bridge
(1) The room from which a ship is controlled. On a smaller boat this is usually not a room, is outside, and is known as a cockpit.
(2) A man made structure crossing a body of water, usually for the use of automobiles or train. A boat intending to pass under a bridge needs to make sure it has sufficient vertical clearance unless it is a swinging bridge or a drawbridge.

Brightwork
Pieces of varnished wood or polished metal on a vessel.

Bristol fashion
A term used to describe a clean and orderly ship.

Broach to
An undesirable position in which a vessel is turned to expose its side to the oncoming waves.

Broaching
The unplanned turning of a vessel to expose its side to the oncoming waves. In heavy seas this could cause the boat to be knocked down.

Broad on the beam
The position of an object that lies off to one side of the vessel.

Broad reach
Sailing with the apparent wind coming across the quarter of the ship. A broad reach is a point of sail between a beam reach and running.

Bulkhead
An interior wall in a vessel. Sometimes bulkheads are also watertight, adding to the vessel's safety.

Buntline hitch
A type of knot used to attach a line to a shackle.

Buoy
A floating device used as a navigational aid by marking channels, hazards and prohibited areas.

Burdened vessel
The vessel responsible for moving out of another vessels path according to the navigation rules. Also known as the give way vessel.

Burgee
A type of flag used to identify a boater's affiliation with a yacht club or boating organization.

By the lee
A point of sail similar to running where the wind is coming over the quarter of the sailboat on the same side that the main sail and boom are on. This point of sail is considered dangerous because of the possibility of an accidental jibe.

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C

Cabin
A room inside a boat.

Cam cleat
A mechanical cleat used to hold a line automatically. It uses two spring loaded cams that come together to clamp their teeth on the line, which is place between them. Also see jam cleat.

Camber
The curvature of an object such as a sail, keel or deck. Usually used when referring to an objects aerodynamic or hydrodynamic properties.

Can buoy
A cylindrical buoy painted green and having an odd number used in the United States as a navigational aid. At night they may have a green light. Green buoys should be kept on the left side when returning from a larger body of water to a smaller one. Nun buoys mark the other side of the channel. Also see green and red daymarks

Canal
A manmade waterway used to connect bodies of water that do not connect naturally. Canals use locks to raise and lower boats when connecting bodies of water that have different water levels. The Panama and Suez canals are two of the most famous.

Canoe stern
A pointed stern, such as those on a canoe.

Canvas
Tightly woven cloth used for sails, covers, dodgers and biminis. Typically made from cotton, hemp or linen. Modern sails are made out of synthetic materials generally known as sailcloth.

Capsize
When a boat falls over in the water so that is no longer right side up.

Capstan
A rotating drum used to haul heavy lines and chains. Similar to a winch, but mounted vertically.

Captain
The person who is in charge of a vessel and legally responsible for it and its occupants.

Car
A sliding fitting that attaches to a track allowing for the adjustment of blocks or other devices attached to the car.

Carbon fiber
A synthetic material consisting of fibers glued together with epoxy that is very strong for its weight.

Cardinal points
The points of North, South, East and West as marked on a compass rose.

Carlins
Structural pieces running fore and aft between the beams.

Carrick bend
A knot used to tie two lines together.

Cast off
To detach mooring lines as when leaving a dock.

Catamaran
A twin hulled boat. Catamaran sailboats are known for their ability to plane and are faster than single hulled boats (monohull) in some conditions.

Catboat
A sailboat rigged with one mast and one sail.

Catenary
The sag in a line strung between two points.

Caulking
Material used to seal the seams in a wooden vessel, making it watertight.

Cavitate, cavitation
A type of drag on a propeller caused by air bubbles forming near the tips of a propeller that is spinning too fast. This causes inefficiencies and unnecessary wear and tear on the propeller.

Celestial navigation
A method of using the stars, sun and moon to determine one's position. Position is determined by measuring the apparent altitude of one of these objects above the horizon using a sextant and recording the times of these sightings with an accurate clock. That information is then used with tables in the Nautical Almanac to determine one's position.

Celestial sphere
An imaginary sphere surrounding the globe that contains the sun, moon, stars and planets.

Center line
The imaginary line running from bow to stern along the middle of the boat.

Centerboard
A device similar to a keel, except that it is usually either removable or can pivot. Also see daggerboard. The centerboard is used like a keel to reduce the unwanted sideways motion of a boat.

Certificate
A legal paper or license of a boat or its captain.

Chafe
Wear caused by the friction of parts moving past each other.

Chafing gear
Tape, cloth or other materials placed on one or more parts that rub together. By using chafing gear, hopefully the chafing gear will wear rather than the parts that it is protecting.

Chain locker
Storage for the anchor chain.

Chain
Metal links that are locked together to make a strong and flexible line. Chains are typically used for anchors and other places where high loads may be exerted on the line, particularly in large vessels.

Chainplates
Plates on the deck to which lines and stays are attached.

Chandlery
A store that sells nautical gear.

Channel marker
A buoy or other mark used to mark a navigable path through a waterway.

Channel
A navigable route on a waterway, usually marked by buoys. Channels are similar to roads where the water is known to be deep enough for ships or boats to sail without running aground.

Chart datum
The water level used to record data on a chart. Usually the average low tide water level.

Chart table
A table designated as the area in the boat where the navigator will study charts and plot courses.

Chart
Maps for boaters are known as charts. Charts are usually issued by government agencies and include information on channels, navigational aids, water depth and hazards.

Cheek block
A block with one end permanently attached to a surface.

Chine
The location where the deck joins the hull of the boat.

Chock
A fitting that a line can pass through and be controlled.

Chockablock
When a line is pulled as tight as is can go, as when two blocks are pulled together.

Chop
Small, steep disorderly waves.

Chronometer
An accurate clock that is used for navigation.

Classes
Groups of boats organized for racing. Boats compete against others in the same class, assuming that their performance will be similar.

Cleat hitch
A figure eight pattern used to tie a line to a cleat.

Cleat
A fitting to which lines can be easily attached.

Clevis pin
A metal pin used to attach fittings to each other or their mounts.

Clew
The lower aft corner of a sail.

Close hauled
Sailing with the sails hauled tight, sailing the boat towards the wind as much as possible.

Close Reach
Sailing with the wind coming from the direction forward of the beam of the boat. A close reach is the point of sail between a beam reach and close hauled.

Close up
A flag hoisted to the top of a flagpole. Also see at the dip.

Close winded
A boat that is able to sail well into the wind.

Clove hitch
A type of knot typically used when mooring. It is easily adjustable, but it may work loose.

Club footed
A jib or staysail that utilizes a small boom.

Club
A boom on a jib or staysail.

CNG
Compressed natural gas. A type of compressed gas used as fuel for stoves and heaters. CNG is stored in metal cylinders prior to use. CNG is considered safer than other types of fuel such as propane (LPG) because it is lighter than air and may rise into the sky in the event of a leak. Caution should still be used as CNG can collect near the cabin ceiling, potentially causing an explosion. Propane is available in more areas around the world than CNG so CNG is not often used outside of North America.

Coaming
A small wall to prevent water from entering the cockpit.

Coast Pilots
Books covering information about coastal navigation, including navigational aids, courses, distances, anchorages and harbors.

Coast
The region of land near the water.

Coastal navigation
Navigating near the coast, allowing one to find one's position by use of landmarks and other references.

Cock
A valve used to regulate the flow of water or gas.

Cockpit sole
Sole (floor) of the cockpit.

Cockpit
The location from which the boat is steered, usually in the middle or the rear of the boat.

Code
Any method of passing messages, such as visual or electronic Morse code, code flag pennants and semaphore.

Cold front
Used in meteorology to describe a mass of cold air moving toward a mass of warm air. Strong winds and rain typically accompany a cold front.

Cold molding
A method of bending a material into an appropriate shape without heating or steaming to soften the material first.

Collision bulkhead
A watertight forward bulkhead designed to keep the boat from sinking in the event of a collision.

Colors
The national flag and or other flags.

COLREGS
A term for the international rules designed to prevent collisions between boats.

Come about
To tack. To change a boat's direction, bringing the bow through the eye of the wind.

Companionway
The entryway into the cabin from the deck.

Compass card
A card labeling the 360° of the circle and the named directions such as north, south, east and west.

Compass course
The course as read on a compass. The compass course has added the magnetic deviation and the magnetic variation to the true course.

Compass error
Magnetic deviation. The difference between the reading of a compass and the actual magnetic course or bearing due to errors in the compass reading. These errors can be caused by metals, magnetic fields and electrical fields near the compass. Prior to using a compass, magnetic deviation should be recorded for many different points on the compass as the error can be different at different points. The act of checking for magnetic deviation is called swinging.

Compass rose
A circle on a chart indicating the direction of geographic north and sometimes also magnetic north. Charts usually have more that one compass rose. In that case the compass rose nearest to the object being plotted should be used as the geographic directions and magnetic variations may change slightly in different places on the chart.

Compass
(1) An instrument that uses the earth's magnetic field to point to the direction of the magnetic north pole.
(2) A device used to draw circles.

Composite construction
An object made with more than one type of material.

Compressed natural gas
CNG for short. A type of compressed gas used as fuel for stoves and heaters. CNG is stored in metal cylinders prior to use. CNG is considered safer than other types of fuel such as propane (LPG) because it is lighter than air and may rise into the sky in the event of a leak. Caution should still be used as CNG can collect near the cabin ceiling, potentially causing an explosion. Propane is available in more areas around the world than CNG so CNG is not often used outside of North America.

Continent
A large land mass, such as Africa, Antarctica, Asia, Australia, Europe, North America, and South America.

Continental shelf
A region of relatively shallow water surrounding each of the continents.

Coordinated universal time
A time standard that is not affected by time zones or seasons. Time measured in coordinated universal time labeled with the term Zulu. It is used so that people around the world can communicate about time without regard to individual time zones.

Cordage
Any rope or line.

Cotter pin
A small metal pin used to keep other parts from changing their position, such as to keep a nut from turning or a clevis pin from falling out.

Counter
The part of the stern aft of where it leaves the waterline.

Course
(1) The direction the boat is traveling or intends to travel.
(2) A path which racing boats are to follow.

Courtesy flag
A smaller version of the flag of the country being visited. It is flown from the starboard spreader.

Cove
A small sheltered recessed area in the shoreline.

Cowls
Scoop like devices used to direct air into a boat.

CQR anchor
Also called a plow anchor. Short for coastal quick release anchor. An anchor that is designed to bury itself into the ground by use of its plow shape.

Cradle
A frame to support a vessel when out of water.

Crest
(1) The top of a wave.
(2) The act of reaching the top of a wave.

Crew
One or more people that aid in the operation of a boat.

Cringle
A fitting in a sail that allows a line to fasten to it.

Crossing situation
When two vessels approach each other and their paths are crossing. The boat with the other boat on its starboard side is the give way vessel and must yield.

Crosstrees
Spreaders. Small spars extending toward the sides from one or more places along the mast. The shrouds cross the end of the spreaders, enabling the shrouds to better support the mast.

Cruising guides
Books that describe features of particular sailing areas, such as hazards, anchorages, etc.

Cunningham
A line used to control the tension along a sail's luff in order to maintain proper sail shape.

Current
The movement of water, due to tides, river movement and circular currents caused by the motion of the earth.

Cutter
A sailboat with one mast and rigged a mainsail and two headsails. Also see sloop.

Cutwater
The front edge of the boat.

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D

Dacron
A synthetic polyester material.

Daggerboard
Similar to a centerboard, except that it is raised vertically. Like a keel, daggerboards are used to prevent a sailboat being pushed sideways by the wind.

Danforth anchor
A brand of lightweight anchor. It has pivoting flukes that dig into the ground as tension is placed on the anchor. It does not have a stock.

Davit
A device that projects beyond the side of the boat to raise objects from the water. Typically a single davit is used on the bow of a vessel to raise an anchor, and a pair are used on the side or stern of the vessel to raise a dinghy.

Daybeacon, daymark
A navigational aid visible during the day. In the United States and Canada, square red daybeacons should be kept on the right and triangular green daybeacons should be kept on the left when returning from a larger to smaller body of water. Also see can and nun buoys.

Daysailer
A small boat intended to be used only for short sails or racing.

Dayshape
Black diamond, ball, and cone shapes hoisted on vessels during the day to indicate restricted movement ability or type. For example three balls means aground.

Dead ahead
A position directly in front of the vessel.

Dead astern
A position directly behind the vessel.

Dead before
Running with the wind directly behind the boat.

Dead reckoning
A method of determining position by making an educated guess based on last known position, speed and currents.

Deadlight
Fixed ports that do not open, placed in the deck or cabin to admit light.

Deadrise
The measurement of the angle between the bottom of a boat and its widest beam. A vessel with a 0º deadrise has a flat bottom, high numbers indicate deep V shaped hulls.

Deck stepped
A mast that is stepped (placed) on the deck of a boat rather than through the boat and keel stepped. The mast of a deck stepped boat is usually easier to raise and lower and are usually intended for lighter conditions than keel stepped boats.

Deck
The surface on the top of the boat that people can stand on.

Deckhead
The underside of the deck, viewed from below (the ceiling.)

Depth sounder
An instrument that uses sound waves to measure the distance to the bottom.

Deviation
See magnetic deviation or compass error.

Dinghy, dink
A small boat used to travel from a boat to shore, carrying people or supplies. Also known as a dink or tender.

Dismast
The loss of a mast on a boat. Generally this also means the loss of some or all of the ability of the boat to sail.

Displacement hull
A type of hull that only floats, even when in motion, as opposed to a type of hull that allows a boat to skim across the surface of the water. See planing hull.

Displacement speed
Also hull speed. The theoretical speed that a boat can travel without planing, based on the shape of its hull. This speed is 1.34 times the length of a boat at its waterline. Since most monohull sailboats cannot exceed their hull speed, longer boats are faster.

Displacement
The weight of a boat measured as a the weight of the amount of water it displaces. A boat displaces an amount of water equal to the weight of the boat, so the boat's displacement and weight are identical.

Distance made good
The distance traveled after correction for current, leeway and other errors that may not have been included in the original distance measurement.

Distress signals
Any signal that is used to indicate that a vessel is in distress. Flares, smoke, audible alarms, electronic beacons and others are all types of distress signals.

Ditty bag
A small bag.

Dive flag
(1) A red flag with a white stripe.
(2) The alpha flag is the legal requirement for boats with divers in the water. Boats should probably display both flags when they have divers in the water.

Dividers
A navigational tool used to measure distances on a chart.

Dock
(1) A platform where vessels can make fast. The act of securing a boat in such a place. Docks are often subdivided into smaller areas for docking known as slips.
(2) The act of entering a dock.

Documentation
Licenses or registration papers for a vessel. Types of documentation vary depending on the country, vessel size and purposes.

Dodger
A cover attached to the top of the cabin at the front of the cockpit. Dodgers help shelter the cockpit from wind and water.

Dolphin
A playful sea mammal. Also a type of fish. Also a group of piles used for mooring or as a channel marker.

Dorade vent
A type of vent designed to let air into a cabin and keep water out by the use of baffles.

Double-braid
A line consisting of a braided inner core and a braided outer sheath.

Double-ender
A boat with a pointed stern. Known as a double-ender because the stern may look very similar to the bow.

Douse
(1) To drop a sail quickly.
(2) To extinguish a candle, lamp, or fire.

Down helm
To steer a sailboat toward the wind.

Downhaul
A line used to pull down on a spar or sail.

Downwind
In the direction the wind is blowing.

Draft
(1) The depth of a boat, measured from the deepest point to the waterline. The water must be at least this depth or the boat will run aground.
(2) A term describing the amount of curvature designed into a sail.

Drag
The resistance to movement.

Dragging
Description of an anchor that is not securely fastened to the bottom and moves.

Draw
Draft. The depth of water that a boat requires to stay off the bottom. A vessel "draws" a certain amount of water.

Drawbridge
A bridge that can be raised vertically to allow boats to pass underneath.

Drift
The velocity of a current.

Drogue
Any object used to increase the drag of a boat. Typically shaped like a parachute or cone opened underwater, drogues slow a boat's motion in heavy weather. Also see sea anchor.

Dry dock
A dock where a boat can be worked on out of the water. The boat is usually sailed into a dry dock and then the water is pumped out.

Dry rot
Used to describe the decay of wood. A misnomer, dry rot is actually caused by moist conditions in fresh water.

Dry storage
Storing on land. Many small boats are placed in dry storage over the winter.

Ducts
Tubes used to move air, such as to ventilate an enclosed area.

DWL
Design waterline. Also length waterline or load waterline (LWL). This is the length of the boat where it meets the water when loaded to its designed capacity.

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E

Ease the sheets
To loosen the lines that control the sails.

Ease
To slowly loosen a line while maintaining control, such as when loosening the sails.

East wind, easterly wind
A wind coming from the east.

East
One of the 4 cardinal compass points. East is at 90° on a compass card.

Ebb, ebb tide
The falling tide when the water moves out to the sea and the water level lowers.

Echo sounder
An electrical fish finder or depth sounder that uses sound echoes to locate the depth of objects in water. It does so by timing the sound pulses.

Eddy
Water or air currents flowing in circular patterns.

Electronic navigation
The use of echo sounders, radio, and various electronic satellite and land based position finders to determine a boat's location.

Emergency tiller
A tiller that is designed to be used in the event that wheel steering fails.

Ensign
The national flag of a boat's home nation.

EPIRB
Emergency Position Indicating Radio Beacon. An emergency device that uses a radio signal to alert satellites or passing airplanes to a vessel's position.

Equator
An imaginary line around the center of the world at 0° of latitude.

Estimated position
A position based on dead reckoning estimations of a boat's position using estimated speed, currents, and the last known position (fix) of the boat.

Eye of the wind
The direction that the wind is blowing from.

Eye splice
A splice causing a loop in the end of a line, by braiding the end into itself or similar methods. It may or may not be reinforced by a metal fitting known as a thimble.

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F

Fair
In good condition.

Fairlead
A fitting designed to control the direction of a line with minimal friction.

Fall off
Also bear away or bear off. A boat falls off the wind when it points its bow further from the eye of the wind. The opposite of heading up.

Fastening
An item such as a nail, screw, rivet or other device used to fasten objects together.

Fathom
A nautical measurement equaling 6 feet (182 cm). Usually used to measure depth.

Fathometer
A brand name for a depth measuring device.

FCC Rules
Federal Communications Commission Rules governing radio equipment and operation in the United States.

Feathering
A propeller that can have the pitch of its blade changed to reduce drag when not in use. Also see folding and variable pitch propellers.

Feet
More than one foot. A foot is a unit of measurement used primarily in the United States. 1 foot equals 30.48 centimeters.

Fend off
To push a boat away from another boat or dock by hand.

Fender
A cushion hung from the sides of a boat to protect it from rubbing against a dock or another boat.

Fetch
The distance that wind and seas (waves) can travel toward land without being blocked. In areas without obstructions the wind and seas can build to great strength, but in areas such as sheltered coves and harbors the wind and seas can be quite calm. Fetch is also used to describe the act of sailing to a location accurately and without having to tack.

Fiberglass
A construction method using layers of woven glass mats that are bonded together with an epoxy (glue).

Fid
A tool used in splicing and working with rope.

Fiddle
A small rail on tables and counters used to keep objects from sliding off when heeled or in heavy seas.

Fiddle Block
A block with two sets of sheaves (sometimes three), one above the other.

Figure-eight
A type of knot that can be used to stop a line from passing through a block or other fitting.

Fin keel
A keel that is narrow and deeper than a full keel.

Finger pier
A small pier that projects from a larger pier.

Fisherman anchor
Kedge anchor. A traditionally shaped anchor having flukes perpendicular to the stock of the anchor and connected by a shank. These are less common than modern anchors such as the plow and lightweight anchors.

Fix
An accurate position of the vessel, as determined by any reasonably accurate method, such as by taking visual bearings.

Flake
To fold a sail in preparation for storage.

Flame arrester
A device used to prevent or stop unwanted flames.

Flare
A device which burns to produce a bright light, sometimes colored, and usually used to indicate an emergency.

Flashing
Used to describe a light that blinks on and off in regular patterns.

Flemish
To coil a line flat on the deck in spirals.

Flinders bar
An iron bar mounted on or near the compass to correct for magnetic deviation in steal hulled ships.

Flood tide
The incoming tide where the water comes in from the sea, lowering the water level.

Flotsam
Debris floating on the water surface.

Fluke
(1) The broad flat parts of an anchor that are designed to grab and hold in the bottom.
(2) Also a fin on a whale.

Flush deck
A deck that is not obstructed by a cabin.

Flying bridge
A high position from which to steer a boat.

Folding
A propeller having blades that fold up when not in use to reduce drag. Also see feathering and variable pitch propellers.

Following sea
A sea with waves approaching from the stern of the boat.

Foot
(1) The bottom edge of a sail.
(2) sailing slightly more away from the wind than close hauled to increase the boat speed.
(3) A unit of measurement used primarily in the United States. 1 foot equals 30.48 centimeters. Units of more than 1 foot are known as feet.

Fore and aft sail
The more common position of the sail with its length running along the ship's length as opposed to a sail such as a square sail which is mounted across the width of the vessel.

Fore and aft
Running along the length of the boat.

Fore
Toward the bow (front) of the vessel.

Forecabin
The cabin towards the front of the vessel.

Forecast
A weather prediction.

Forecastle
Also fo'c'sle or fo'csle. Pronounced fo'csle. The most forward below decks area of a vessel.

Foredeck
The forward part of the deck.

Foremast
The forward mast of a two or more masted vessel.

Forepeak
The furthermost forward storage area of a vessel.

Foresail
A sail placed forward of the mast, such as a jib.

Forestay
A line running from the bow of the boat to the upper part of the mast designed to pull the mast forward. A forestay that attaches slightly below the top of the mast can be used to help control the bend of the mast. The most forward stay on the boat is also called the headstay.

Forestaysail
A sail attached to the forestay as opposed to a jib which is attached to the headstay.

Foretriangle
The space between the mast, the deck, and the headstay.

Forward quarter spring line
A mooring line running forward from the stern of the boat. The forward quarter spring line prevents the boat from moving backward while moored. The after bow spring line does the opposite.

Forward
Toward the bow (front) of the boat.

Foul
When a line ends up somewhere it does not belong and becomes jammed. Lines can foul on blocks, winches and other objects on a boat.

Founder
Used to describe a boat that is having difficulty remaining afloat. "The boat foundered and then sank."

Fractional rig
A type of rig where the jib attaches below the top of the mast.

Freeboard
The distance between the top of the hull and the waterline.

Freeing port
An opening in the rail (bulwarks) along the deck to allow water to drain.

Freestanding mast
A mast made out of exotic materials so that it can support itself without the use of stays. See fully stayed mast.

Fronts
Used in meteorology to describe bounderies between hot and cold air masses. This is typically where bad weather is found.

Full and by
Sailing as close to the wind as possible with full sails.

Full keel
A keel that runs the length of the boat. Full keels have a shallower draft than fin keels.

Fully battened
A sail having battens that run the full horizontal length of the sail.

Fully stayed
A mast supported by the use of lines known as stays and shrouds.

Furl
To lower a sail. Sails are sometimes partially furled to reduce the amount of sail area in use without completely lowering the sail. This is usually known as reefing.

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G

Gaff rigged
A type of traditional working boat using four sided gaff sails that are hoisted on gaffs.

Gaff sail
A four sided sail used instead of a triangular main sail. Used on gaff rigged boats.

Gaff
(1) A spar that holds the top of a four sided gaff sail.
(2) A pole with a hook at the end used to get a fish on board.

Gale force winds
Wind speeds strong enough to qualify the storm as a gale.

Gale
A storm with a wind speed between 34 to 40 knots.

Galley
The kitchen area on a boat.

Gallows frame
A frame used to support the boom.

Gasket
Ties used to tie up the sails when they are furled.

Gennaker
A large sail that is a cross between a spinnaker and a genoa. Hoisted without a pole, the tack is attached at the bottom of the headstay.

Genoa
A large jib that overlaps the mast. Also known as a jenny.

Geographic north
The direction toward the top point of the line about which the earth rotates (between Canada and Russia in the Arctic Ocean.) See also magnetic north.

Geographic position
The position of a boat on a chart.

Gimbals
Hinges for objects such as lamps, compasses and stoves so that they can remain upright as the boat rolls.

Give way vessel
The vessel that must yield to another vessel according to the navigation rules. Also known as the burdened vessel.

Global Positioning System
GPS for short. A system of satellites that allows one's position to be calculated with great accuracy by the use of an electronic receiver.

Globe
A map of the earth drawn on a sphere so that both its distances and angles are accurate.

GMT
Time measured in Greenwich Mean Time. Coordinated universal time is a newer standard. A time standard that is not affected by time zones or seasons.

Go about
To tack.

GPS
Global Positioning System. A system of satellites that allows one's position to be calculated with great accuracy by the use of an electronic receiver.

Grab rail
See hand rail.

Granny knot
A bad knot that was probably tied in error, will not necessarily hold fast, and may be difficult to untie.

Great circle route
A course that is the shortest distance between two points, following a great circle. Great circle routes usually do not look like the shortest route when drawn on a flat map due to deviations caused by trying to draw a flat map of a round object such as the earth.

Great circle
Any circle drawn around the earth such that the center of the circle is at the center of the earth. The shortest distance between any two points on the earth lies along a great circle.

Green buoy
A can buoy. A cylindrical buoy painted green and having an odd number used in the United States as a navigational aid. At night they may have a green light. Green buoys should be kept on the left side when returning from a larger body of water to a smaller one. Nun buoys mark the other side of the channel. Also see green and red daymarks.

Green daymark
A navigational aid used in the United States and Canada to mark a channel. Green triangular daymarks should be kept on the left when returning from a larger to smaller body of water. Red daymarks mark the other side of the channel. Also see can and nun buoys.

Green water
A solid mass of water coming aboard instead of just spray.

Greenwich Mean Time
GMT for short. Coordinated universal time is a newer standard. A time standard that is not affected by time zones or seasons.

Grommet
A ring or eyelet normally used to attach a line, such as on a sail.

Ground swells
Swells that become shorter and steeper as they approach the shore due to shallow water.

Ground tackle
The anchor and its rode or chain and any other gear used to make the boat fast.

Gudgeon
The hole in which the pin from a stern mounted rudder fits. The pin is known as a pintle.

Gunkholing
Cruising in shallow water and spending the nights in coves.

Gunnel, gunwale
Pronounced gunnel. The rail around the edge of a boat. Smaller versions are called toe rails.

Guy
Also called a brace. A line used to control the movement of the object at the other end, such as a spar.

Gybe
Usually spelled jibe. To change direction when sailing in a manner such that the stern of the boat passes through the eye of the wind and the boom changes sides. Prior to jibing, the boom will be very far to the side of the boat. Careful control of the boom and mainsail is required when jibing in order to prevent a violent motion of the boom when it switches sides. Jibing without controlling the boom properly is known as an accidental jibe. Tacking is preferred to jibing because the boom is not subject to such violent changes. Jibing is usually needed when running with the wind and tacking is used when close hauled.

Gypsy
A windlass or capstan drum.

Gyres
A large circular ocean current.

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H

Hail
To attempt to contact another boat or shore, either by voice or radio.

Half hitch
A simple knot usually used with another knot or half hitch.

Halyard
A line used to hoist a sail or spar. The tightness of the halyard can affect sail shape.

Hand bearing compass
A small portable compass.

Hand lead
A weight attached to a line used to determine depth by lowering it into the water.

Hand rail
A hand hold. Usually along the cabin top or ladder.

Hand
Someone who helps with the work on a boat.

Handsomely
To do something carefully and in the proper manner, such as when stowing a line.

Handy-billy
A movable block and tackle.

Hanging locker
A locker big enough to hang clothes.

Hank
(1) Clips used to fasten a sail to a stay.
(2) Using such slips to attach a sail to a stay.

Harbor
An anchorage protected from storms either naturally or by man-made barriers.

Harbormaster
The individual who is in charge of a harbor.

Hard over
To move all the way in one direction, such as when turning the wheel.

Hard-a-lee
A command to steer the boat downwind.

Hard-chined
A hull shape with flat panels that join at sharp angles.

Hatch
A sliding or hinged opening in the deck, providing people with access to the cabin or space below.

Haul out
Remove a boat from the water.

Haul
Pulling on a line.

Hauling part
The part on the object which is hauled upon.

Hawse hole
A hole in the hull for mooring lines to run through.

Hawsepipes
Pipes to guide lines through the hawse hole. On large vessels anchors are stored with their shanks in the hawsepipes.

Hawser
A rope that is very large in diameter, usually used when docking large vessels.

Hazard
An object that might not allow safe operation. A group of rocks just under the water or a submerged wreck could be a navigational hazard.

Head seas
Waves coming from the front of the vessel.

Head to wind
A position with the boat's bow in the direction that the wind is coming from. This will probably stop the boat and place it in irons.

Head up
To turn the bow more directly into the eye of the wind. The opposite of falling off.

Head
(1) The front of a vessel.
(2) The upper corner or edge of a sail.
(3) The top or front of a part.
(4) The toilet and toilet room in a vessel.

Heading
The actual course of the vessel at any given time.

Headsail
Any sail forward of the mast, such as a jib.

Headstay
The furthest forward of all the stays on the boat.

Headway
The forward motion of a vessel through the water.

Heave
To throw or pull strongly on a line.

Heaving line
A light line used to be thrown ashore from which a larger rope can then be pulled.

Heaving to
Arranging the sails in such a manner as to slow or stop the forward motion of the boat, such as when in heavy seas.

Heavy seas
When the water has large or breaking waves in stormy conditions.

Heavy weather
Stormy conditions, including rough, high seas and strong winds. Probably uncomfortable or dangerous.

Heel, heeling
When a boat tilts away from the wind, caused by wind blowing on the sails and pulling the top of the mast over. Some heel is normal when under sail.

Heeling error
The error in a compass reading caused by the heel of a boat.

Helm’s alee
A warning from the helmsman that the boat is about to tack.

Helm
The wheel or tiller of a boat.

Helmsman
The person who is steering the boat.

Hemisphere
Half of a sphere. On the globe hemispheres are used to describe the halves of the earth north or south of the equator.

High tide
The point of a tide when the water is the highest. The opposite of low tide.

High
A location of higher barometric pressure than the surrounding area of a weather system.

Hiking stick
An extension to the tiller allowing the helmsman to steer while hiking. This may be desired for improved visibility or stability.

Hiking
Moving the crew's weight to or past the windward rail to counteract the heeling of a boat. Typically seen when boats are racing.

Hitch
A knot used to attach a line to a cleat or other object.

Hoist
(1) To raise a sail.
(2) To raise anything up.

Holding ground
The type of bottom that the anchor is set in. "Good holding ground."

Holding tank
A storage tank where sewage is stored until it can be removed to a treatment facility.

Homing
Using a radio direction finder to steer toward a source of radio signals.

Horizon
Where the water and sky or ground and sky appear to intersect.

Horizontal angle
The angle measured between two fixed objects (usually on shore) to aid in finding a boats position by determining the arc of a circle on which the boat must lie.

Horseshoe buoy
A floatation device shaped like a U and thrown to people in the water in emergencies.

Hull speed
Also displacement speed. The theoretical speed that a boat can travel without planing, based on the shape of its hull. This speed is about 1.34 times the square root of the length of a boat at its waterline. Since most monohull sailboats cannot exceed their hull speed, longer boats are faster.

Hull
The main structural body of the boat, not including the deck, keel, mast, or cabin. The part that keeps the water out of the boat.

Hurricane
A strong tropical revolving storm of force 12 or higher in the northern hemisphere. Hurricanes revolve in a clockwise direction. In the southern hemisphere these storms revolve counterclockwise and are known as typhoons.

Hydrodynamic
A shape designed to move efficiently through the water.

Hydrofoil
A boat that has foils under its hull onto which it rises to plane across the water surface at high speed. See displacement and planing hulls.

Hydrography
The study of the earth's waters.

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I

ICW
Short for Intercoastal Waterway. A system of rivers and canals along the Atlantic and Gulf Coasts of the United States allowing boats to travel along them without having to go offshore.

In irons
A sailboat with its bow pointed directly into the wind, preventing the sails from filling properly so that the boat can move. It can be very difficult to get a boat that is in irons back under sail. An old square rigger could take hours to get underway again.

Inboard cruiser
A motorboat with an inboard engine.

Inboard
(1) Toward the center of the boat.
(2) An engine that is mounted inside the boat.

Inch
A unit of measurement used primarily in the United States equal to 2.54 centimeters.

Inches of mercury
A unit used when measuring the pressure of the atmosphere. 33.86 millibars. Inches of mercury are used because some barometers use the height of mercury in a sealed tube as a measuring device.

Inflatable
A dinghy or raft that can be inflated for use or deflated for easy stowage.

Inland Rules
Rules for the operation of vessels in harbors, rivers and lakes.

Inland
Away from large bodies of water, surrounded by land. See offshore.

Inlet
A bay or cove along a river, sea or lake coast line. A stream or bay leading inland. A narrow passage between to bodies of land.

Intercoastal Waterway
A system of rivers and canals along the Atlantic and Gulf Coasts of the United States allowing boats to travel along them without having to go offshore.

International Code of Signals
A set of radio, sound, and visual signals designed to aid in communications between vessels without language problems. It can be used with Morse Code, with signal pennants, and by spoken code letters.

Irons
In irons. A sailboat with its bow pointed directly into the wind, preventing the sails from filling properly so that the boat can move. It can be very difficult to get a boat that is in irons back under sail. An old square rigger could take hours to get underway again.

Isobars
Lines drawn on a weather map indicating regions of equal pressure. When the lines are close together, this indicates a rapid change in air pressure, accompanied by strong winds.

Isogonic lines
A line connecting points of equal magnetic variation on a map.

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J

Jack line, jack stay
A strong line, usually of flat webbing, or a wire stay running fore and aft along the sides of a boat to which a safety harness can be attached.

Jacobs’s ladder
A rope ladder.

Jam cleat
A cleat designed to hold a line in place without slipping. It consists of two narrowing jaws with teeth in which the line is placed. Also see cam cleat.

Jaws
A fitting holding a boom or gaff to the mast.

Jenny
A genoa jib. A large jib that overlaps the mast.

Jetty
A man made structure projecting from the shore. May protect a harbor entrance or aid in preventing beach erosion.

Jib netting
A rope net to catch the jib when it is lowered.

Jib sheets
A sheet (line) used to control the position of the jib. The jib has two sheets, and at any time one is the working sheet and the other is the lazy sheet.

Jib stay
The stay that the jib is hoisted on. Usually the headstay.

Jib topsail
A small jib set high on the headstay of a double headsail rig.

Jib
A triangular sail attached to the headstay. A jib that extends aft of the mast is known as a genoa.

Jibe
Also spelled gybe. To change direction when sailing in a manner such that the stern of the boat passes through the eye of the wind and the boom changes sides. Prior to jibing the boom will be very far to the side of the boat. Careful control of the boom and mainsail is required when jibing in order to prevent a violent motion of the boom when it switches sides. Jibing without controlling the boom properly is known as an accidental jibe. tacking is preferred to jibing because the boom is not subject to such violent changes. Jibing is usually needed when running with the wind and tacking is used when close hauled.

Jiffy reefing
A method of lowering the sail in sections so that it can be reefed quickly.

Jigger
A small sail on the mizzen mast of a yawl or a ketch.

Junction buoy
Also known as a preferred channel buoy. A red and green horizontally striped buoy used in the United States to mark the separation of a channel into two channels. The preferred channel is indicated by the color of the uppermost stripe. Red on top indicates that the preferred channel is to the right as you return, green indicates the left. Also see can and nun buoys.

Jury rig
A temporary repair using improvised materials and parts.

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K

Kedging
(1) To kedge off. A method of pulling a boat out of shallow water when it has run aground. A dinghy is used to set an anchor, then the boat is pulled toward the anchor. Those steps are repeated until the boat is in deep enough water to float.
(2) A traditionally shaped anchor having flukes perpendicular to the stock of the anchor and connected by a shank. These are less common than modern anchors such as the plow and lightweight anchors.

Keel stepped
A mast that is stepped (placed) on the keel at the bottom of the boat rather than on the deck. Keel stepped masts are considered sturdier than deck stepped masts.

Keel
A flat surface built into the bottom of the boat to prevent the reduce the leeway caused by the wind pushing against the side of the boat. A keel also usually has some ballast to help keep the boat upright and prevent it from heeling too much. There are several types of keels, such as fin keels and full keels.

Keelson
A beam attached to the top of the floors to add strength to the keel on a wooden boat.

Ketch
A sailboat with two masts. The shorter mizzen mast is aft of the main mast, but forward of the rudder post. A similar vessel, the yawl, has the mizzen mast aft of the rudder post.

King plank
The center plank on a wooden deck.

King spoke
The top spoke on a wheel when the rudder is centered.

Knees
Supporting braces used for strength when two parts are joined.

Knocked down
A boat that has rolled so that she is lying on her side or even rolled completely over. A boat with appropriate ballast should right herself after being knocked down.

Knot
(1)
A speed of one nautical mile per hour.
(2) A method of attaching a rope or line to itself, another line or a fitting.

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L

Labor
Heavy rolling or pitching while underway.

Lacing
A line used to attach a sail to a spar.

Laid up
A boat in a dry dock.

Land breeze
A wind moving from the land to the water due to temperature changes in the evening.

Landlocked
Surrounded by land.

Landmark
A distinctive reference point that can be used for navigation.

Lanyard
A line attached to a tool.

Lash
To tie something with a line.

Lateral resistance
The ability of a boat to keep from being moved sideways by the wind. Keels, daggerboards, centerboards, and leeboards are all used to improve a boat's lateral resistance.

Latitude
Imaginary lines drawn around the world and used to measure distance north and south of the equator. 90° north is the North Pole and 90° south is the South Pole, and the equator is at 0°. Also see longitude.

Launch
(1) To put a boat in the water.
(2) A small boat used to ferry people to and from a larger vessel.

Lay line
An imaginary line on which a sailboat can sail directly to its target without tacking.

Lay up
To prepare a boat for winter storage.

Lay
(1) The position of an item.
(2) The direction in which a stranded rope is twisted.

Lazarette
A small aft storage space for spare parts and other items.

Lazy guy
A line attached to the boom to prevent it from accidentally jibbing.

Lazy jacks
Lines running from above the main sail to the boom to aid in the lowering of the sail, keeping the sail flaked and off of the deck.

Lazy sheet
A line led to a sail, but is not currently in use. The line currently in use is known as the working sheet. Usually the working and lazy sheets change when the boat is tacked.

Lead line
A line with a weight on the end used to measure depth. The lead is dropped into the water and marks on the line are read to determine the current water depth. The lead usually has a cavity to return a sample of the bottom type (mud, sand, etc.)

Leading lights
Lights that are separated in distance so that when they are lined up with one behind the other they provide a bearing. Usually used to enter a harbor or navigate a channel.

Leading marks
Unlit navigational aids for use during the day. Like leading lights, they mark a bearing to a channel when they are lined up one above the other.

League
3 nautical miles.

Lee helm
The tendency, if any, for a sailboat to want to steer away from the direction of the wind. The opposite condition is known as weather helm.

Lee shore
The shore that the wind is blowing toward. It is important to keep distance from the lee shore because the boat will be blown toward it if control of the vessel is lost.

Lee
The direction that the wind is blowing toward. The direction sheltered from the wind.

Leeboards
(1) Boards projecting into the water from the lee side of a vessel to help keep it from slipping sideways in the water when traveling across the wind, similar in intent to a keel.
(2) A board placed on the side of a berth to keep the occupant from falling out.

Leech line
A line used to tighten the leech of a sail, helping to create proper sail shape.

Leech
The aft edge of a fore and aft sail.

Leecloths
Cloths raised along the side of a berth to keep the occupant from falling out.

Leeward
The direction away from the wind. Opposite of windward.

Leeway
The sideways movement of a boat away from the wind, usually unwanted. Keels and other devices help prevent a boat from having excessive leeway.

Licensed pilot
A pilot with a license stating that they are qualified to guide vessels in a particular area.

Lie
(1) Where an object is.
(2) To put an object in place.

Life boat
A small boat used for emergencies such as when the parent boat is sinking.

Life jacket
A device used to keep a person afloat. Also called a life preserver, life vest, PFD or personal floatation device.

Life preserver
A device used to keep a person afloat. Also called a life jacket, life vest, PFD or personal floatation device.

Life raft
An emergency raft used in case of serious problems to the parent vessel, such as sinking.

Life vest
A device used to keep a person afloat. Also called a life jacket, life preserver, PFD or personal floatation device.

Lifeline
A line running between the bow and the stern of a boat to which the crew can attach themselves to prevent them from being separated from the boat.

Light list
A list of lights arranged in geographical order.

Light
A lit navigational aid such as a lighthouse that can be used at night or in poor visibility.

Lighthouse
A navigational light placed on a structure on land. The supporting structure was a house in which the person that maintained the light lived. Most modern lighthouses no longer have living areas.

Lightship
A light placed on a ship. The ship remained in a fixed position. Most lightships have been replaced by lit buoys or other structures.

Lightweight anchor
Danforth anchor. It has pivoting flukes that dig into the ground as tension is placed on the anchor. It does not have a stock.

Limber hole
A hole in between compartments in the bottom of the boat to allow water to flow into the bilge where it is sent overboard.

Line
On a boat most ropes are called lines.

Linestoppers
A device used to keep a line from slipping, such as a jam cleat.

Liquid petroleum gas
LPG or propane for short. Propane is a common fuel used for cooking and heating. CNG (natural gas) is considered safer because propane is heavy than air and will sink into the bilge if it leaks, creating the potential for an explosion. Propane is more easily available throughout the world than CNG however, so it is used for most boats outside of North America.

List
A leaning to one side when not underway. Usually the result of an improperly loaded boat. Heeling is different from a list because it is caused by the forces of wind acting upon a sailboat that is underway. When a boat changes tacks, the direction of the heel will change sides, whereas a list is a continual leaning to the same side under any condition.

LOA
Length overall. The total length of a boat including bowsprits or other items projecting from the bow or the stern of the boat.

Lock
A device that allows boats to pass between bodies of water having different water levels, such as in a canal. A boat enters a lock, then large doors close behind it. The water level is then either raised or lowered until a second set of doors can be opened and the boat can pass through.

Locker
Any storage place on a boat. See also chain locker, hanging locker, and wet locker.

Log
(1) A device used to measure the distance traveled through the water. The distance read from a log can be affected by currents, leeway and other factors, so those distances are sometimes corrected to a distance made good. Logs can be electronic devices or paddle wheels mounted through the hull of the boat or trailed behind it on a line.
(2) A written record of a boat's condition, usually including items such as boat position, boat speed, wind speed and direction, course, and other information.

Logbook
A book in which the boat's log is kept. Each entry usually contains the time and date of the entry, weather conditions, boat speed and course, position and other information and observations.

Long splice
A method of splicing two lines of identical thickness by unwrapping strands and braiding the lines back together. Long splices have the advantage of being able to fit through blocks and other devices, but are not as strong as other methods of joining lines.

Longitude
Imaginary lines drawn through the north and south poles on the globe used to measure distance east and west. Greenwich England is designated as 0° with other distances being measured in degrees east and west of Greenwich. For example the center of California, USA is approximately 120° west and the center of Australia is around 135° east. Also see latitude.

Lookout
A person designated to watch for other vessels and hazards.

Loose footed
A sail whose foot (bottom) is not attached to a boom or other rigid object. The opposite of club footed.

LORAN
An electronic instrument using radio waves from various stations to find one's position. The LORAN system is being replaced by the GPS system and will be obsolete in a few years. Many LORAN stations have already stopped providing service.

Low tide
The point of a tide when the water is the lowest. The opposite of high tide.

Low
Used in meteorology to describe an area of low atmospheric pressure.

LPG
Liquid petroleum gas or propane. Propane is a common fuel used for cooking and heating. CNG (natural gas) is considered safer because propane is heavy than air and will sink into the bilge if it leaks, creating the potential for an explosion. Propane is more easily available throughout the world than CNG however, so it is used for most boats outside of North America.

Lubber line
A mark on a compass used to read the heading of a boat.

Luff rope
Bolt rope. A rope in the luff of a sail. The luff rope is usually used to attach the sail to a mast.

Luff
(1) The edge of a sail toward the bow of a boat.
(2) A term used to describe that edge when the airflow around it stalls. (see luffing)

Luffing
A description of a flapping motion along the luff (leading edge) of a sail. A sail begins to luff when the air flow stalls when traveling across the sail. Luffing is a sign that the sail is not properly trimmed or that the boat is trying to sail too close to the eye of the wind (pinching.)

Lugs
Metal or plastic pieces attached to a sail's luff that slide in a mast track to allow easy hoisting of the sail.

Lull
A period of no wind. Lulls may be followed by a significant change of wind speed and direction.

LWL
Load waterline or length waterline. Also design waterline (DWL.) This is the length of the boat at the waterline when loaded to its designed capacity.

Lying ahull
A boat that is letting herself be subjected to prevailing conditions without the use of sails or other devices. Lying ahull is usually not preferred to other actions because a boat may tend to lie with her beam to the waves and the wind (parallel to the waves.) This can cause a boat to roll excessively and even become knocked down.

Lying to
A boat that is almost stopped with her bow into the wind, probably with the aid of a sea anchor.

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M

Magnetic bearing
The bearing of an object after magnetic variation has been considered, but without compensation for magnetic deviation.

Magnetic course
The course of a vessel after magnetic variation has been considered, but without compensation for magnetic deviation.

Magnetic deviation
Compass error. The difference between the reading of a compass and the actual magnetic course or bearing due to errors in the compass reading. These errors can be caused by metals, magnetic fields and electrical fields near the compass. Prior to using a compass, magnetic deviation should be recorded for many different points on the compass as the error can be different at different points. The act of checking for magnetic deviation is called swinging.

Magnetic north
The direction to which a compass points. Magnetic north differs from true north because the magnetic fields of the planet are not exactly in line with the north and south poles. Observed differences between magnetic and true north is known as magnetic variation.

Magnetic variation
The difference between magnetic north and true north, measured as an angle. Magnetic variation is different in different locations, so the nearest compass rose to each location on a chart must be used.

Main mast
The tallest (or only) mast on a boat.

Main topsail
A topsail on the main mast.

Mainsail
The main sail that is suspended from the main mast.

Mainsheet
The line used to control the mainsail.

Make fast
To attach a line to something so that it will not move.

Make way
Moving through the water.

Marina
A place where boats can find fuel, water and other services. Marinas also contain slips where boats can stay for a period of time.

Mark
(1) Marks used on a lead line or anchor rode indicating the length of the line at that point.
(2) A buoy or other object used to mark a location.

Marl
To wrap a small line around another.

Marline
A small line used for whipping, seizing, and lashing.

Marlinespike
A pointed tool used to separate the strands of a rope or wire.

Mast boot
A protective cover wrapped around the mast at the deck on a keel stepped boat to prevent water from entering the boat.

Mast box
A box where a deck stepped mast is stepped.

Mast partners
Supporting structures to take the load of the mast at the deck.

Mast step
The place that supports the bottom of the mast. The mast step usually has a built in pattern fitting a matching pattern on the bottom of the mast, enabling the mast to be accurately positioned.

Mast track
A track or groove in the back of the mast to which the sail is attached by means of lugs or the bolt rope.

Mast
Any vertical spar on the boat that sails are attached to. If a boat has more than one mast, they can be identified by name.

Master
The person in charge of a vessel. The captain.

Masthead light
Also known as a steaming light. The masthead light is a white light that is visible for an arc extending across the forward 225° of the boat. When lit the masthead light indicates that a vessel under power, including sailboats with engines running. Masthead lights are usually located halfway up the mast rather than at the top.

Masthead
The top of a mast. Wind direction indicators and radio antennas usually collect on the masthead.

Mate
An assistant to the captain.

MAYDAY
An internationally recognized distress signal used on a radio to indicate a life threatening situation. Mayday calls have priority over any other radio transmission and should only be used if there is an immediate threat to life or vessel. Mayday comes from the French "M'aidez" which means "help me." For urgent situations that are not immediately life threatening there is the PAN PAN identifier. Less urgent messages such as navigational hazards should send a SECURITE message.

Mean low water
A figure representing the average low tide of a region.

Mean lower low water
In an area with two tides, this figure represents the average of the lowest of the low tides.

Mean
Average.

Measured mile
A course marked by buoys or ranges measuring one nautical mile. Measured miles are used to calibrate logs.

Mediterranean berth
A method of docking with a boat's stern to the dock.

Mercator
A type of projection of the globe used when making charts. Since the world is a sphere, it is impossible to draw accurate charts on flat paper. A Mercator projection shows all of the meridians as straight vertical lines rather than lines that would intersect. This is the type of projection used on a typical world map, but the distances become very distorted near the poles.

Meridian
A longitude line. Meridians are imaginary circles that run through both poles.

Messenger
A small line used to pull a heavier line or cable. The messenger line is usually easier to throw, lead through holes or otherwise manipulate than the line that it will be used to pull.

Meteorology
The study of weather.

Midchannel buoy
A red and white vertically striped buoy used in the United States to mark the middle of a channel. Midchannel buoys may be passed by on either side. Also see nun and can buoys.

Midships
A place on a boat where its beam is the widest.

Mile
(1) Distance at sea is measured in nautical miles, which are about 6067.12 feet, 1.15 statute miles or exactly 1852 meters. Nautical miles have the unique property that a minute of latitude is equal to one nautical mile (there is a slight error because the earth is not perfectly round.) Measurement of speed is done in knots where one knot equals one nautical mile per hour.
(2) A statute mile is used to measure distances on land in the United states and is 5280 feet.

Millibar
A unit of pressure used to measure the pressure of the atmosphere. 1 millibar equals 0.03 inches of mercury.

Minute
(1) When used to measure location a minute is one sixtieth of one degree. One minute of latitude is equal to one nautical mile. Each minute is divided into sixty seconds.
(2) When measuring time a minute is one sixtieth of one hour.

Mizzen mast
A smaller aft mast on a ketch or yawl rigged boat.

Mizzen sail
The sail on the aft mast of a ketch or yawl rigged sailboat.

Mizzen staysail
A small sail that is sometimes placed forward of the mizzen mast.

Monkey fist
A large heavy knot usually made in the end of a heaving line to aid in accurate throwing.

Monohull
A boat that has only one hull, as opposed to multihull boats such as catamarans or trimarans.

Moor
To attach a boat to a mooring, dock, post, anchor, etc.

Mooring buoy
A buoy marking the location of a mooring. Usually attached to an anchor by a small pendant.

Mooring line
A line used to secure a boat to an anchor, dock, or mooring.

Mooring
A place where a boat can be moored. Usually a buoy marks the location of a firmly set anchor.

Morse code
A code that uses dots and dashes to communicate by radio or signal lights.

Motor sailor
A boat designed to use its motor for significant amounts of time and use the sails less often than a normal sailboat.

Motor
(1) An engine.
(2) The act of using an engine to move a boat.

Mount
(1) An attachment point for another object.
(2) The act of putting an object on its mount.

Mouse
A line used to reeve lines.

Multihull
Any boat with more than one hull, such as a catamaran or trimaran.

Mushroom anchor
A type of anchor with a heavy inverted mushroom shaped head. Mushroom anchors are used to anchor in mud and other soft ground.

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N

Natural gas
Short for compressed natural gas or CNG. A type of compressed gas used as fuel for stoves and heaters. CNG is stored in metal cylinders prior to use. CNG is considered safer than other types of fuel such as propane (LPG) because it is lighter than air and may rise into the sky in the event of a leak. Caution should still be used as CNG can collect near the cabin ceiling, potentially causing an explosion. Propane is available in more areas around the world than CNG so CNG is not often used outside of North America.

Nautical Almanac
An annually published book that contains information about the position of the sun, moon, planets and stars. This information is used for celestial navigation.

Nautical mile
Distance at sea is measured in nautical miles, which are about 6067.12 feet, 1.15 statute miles or exactly 1852 meters. Nautical miles have the unique property that a minute of latitude is equal to one nautical mile (there is a slight error because the earth is not perfectly round.) Measurement of speed is done in knots where one knot equals one nautical mile per hour. A statute mile is used to measure distances on land in the United states and is 5280 feet.

Nautical
Having to do with boats, ships, or sailing.

Navigable water
Water of sufficient depth to allow a boat to travel through it.

Navigation lights
Lights on a boat help others determine its course, position and what it is doing. Boats underway should have a red light visible from its port bow, a green light on the starboard bow and a white light at its stern. Other lights are required for vessels under power, fishing, towing, etc.

Navigation Rules
The rules concerning which vessel has the right of way if there is a possibility of collision between two or more boats. The United States Inland Rules of the Road and International Rules of the Road are slightly different.

Navigation
The act of determining the position of a boat and the course needed to safely move the boat from place to place.

Navigational aid
Any fixed object that a navigator may use to find his position, such as permanent land or sea markers, buoys, radio beacons, and lighthouses.

Navigator
The person responsible for navigating a boat.

Neap tide
The tide with the least variation in water level, occurring when the moon is one quarter and three quarters full. The lowest high tide and the highest low tide occur at neap tide. The opposite is the spring tide.

Noon sight
A sighting taken for celestial navigation at noon, when the sun is at its highest point in the sky.

North Pole
The "top" point of the line about which the earth rotates.

North Star
Polaris, the North Star, is visible in the northern hemisphere and indicates the direction of north. In the southern hemisphere the Southern Cross is used to find the direction of south.

North wind, northerly wind
Wind coming from the north.

North
One of the 4 cardinal compass points. North is the direction toward the North Pole and is at 0° on a compass card.

Notices to Mariners
Official notices reporting changes to charts and other navigational and safety items.

Nun buoy
A conical buoy with a pointed top, painted red, and having an even number, used in the United States for navigational aids. At night they may have a red light. These buoys should be kept on the right side of the boat when returning from a larger body of water to a smaller one such as a marina. Can buoys are used on the opposite side of the channel. Also see green and red daymarks.

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O

Oar
A stick with a blade at the end used to row a rowboat. Oars are different than paddles because they have a provision to be secured to the rowboat for rowing, such as an oarlock.

Oarlock
A device to attach oars to a rowboat, allowing the operator to row rather than paddle the boat.

Observed position
A position or fix determined by observing landmarks or other objects to find the position.

Occulting lights
A navigational light which turns on and off in a regular pattern, but is on more than it is off. The opposite of a blinking light.

Ocean
(1) The large body of salt water covering seven tenths of the earth.
(2) The Atlantic, Pacific, Indian, and Arctic Oceans.

Off the wind
Sailing with the wind coming from the stern or quarter of the boat.

Offshore wind
Wind that is blowing away from the land, towards the water.

Offshore
Away from land, toward the water. See inland.

On the beam
To the side of the boat at right angles, abeam.

On the bow
To the bow of the boat, forward of the beam.

On the quarter
To the stern of the boat, aft of the beam.

On the wind
Sailing close hauled. Sailing toward the wind as much as possible with the wind coming from the bow.

Open
A location that is not sheltered from the wind and seas. An open location would not make a good anchorage.

Out of trim
Sails that are not properly arranged for the point of sail that the boat is on. The sails may be luffing or have improper sail shape, or the boat may be heeling too much. These conditions will slow the boat down.

Outboard engine
An engine used to power a small boat. Outboard engines are mounted on a bracket aft of the stern of the boat.

Outboard
On the side of the hull that the water is on. Outboard engines are sometimes just called outboards.

Outhaul
A line used to tension the foot of a sail, used to maintain proper sail shape.

Outrigger
A floatation device attached to one or both sides of the hull to help prevent a capsize.

Overall length
The total length of the boat, including any object protruding from the bow or the stern. Also known as LOA.

Overboard
In the water outside of the vessel.

Overfall
Dangerously steep and breaking seas due to opposing currents and wind in a shallow area.

Overhang
The area of the bow or stern which hangs over the water.

Override
A line that becomes improperly wrapped over itself and fouls a winch.

Owner’s flag
A boat owner's private pennant.

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P

Pad eye
A small fitting with a hole used to guide a line.

Paddle
(1) A stick with a blade in the end of it used to propel a small boat through the water.
(2) The act of using a paddle to propel a boat.

Painted waterline
A painted line on the side of a boat at the waterline. The color usually changes above and below the waterline as the boat is painted with special antifouling paint below the waterline.

Painter
A line attached to the bow of a dinghy and used to tie it up or tow it.

Palm
A tool worn on the hand with a thimble shaped structure on it and used when sewing sails.

PAN PAN
An urgent message used on a radio regarding the safety of people or property. A PAN PAN message is not used when there is an immediate threat to life or property, instead the MAYDAY call is used. PAN PAN situations may develop into MAYDAY situations. As with a MAYDAY, PAN PAN messages have priority on the radio channels and should not be interrupted. In the case of a less urgent safety message, such as a hazard to navigation, the appropriate signal to use is SECURITE.

Parachute flare
An emergency signal flare that will float down on a parachute after launch, hopefully improving its visibility.

Parachute
Sometimes used to describe a spinnaker.

Parallax error
Error that can be introduced when not reading an instrument directly from its front, due to the separation of the indicator and the scale being read.

Parallel rules
A navigational tool used to move a line on a chart from one location to another without changing its angle, such as when moving a plotted course to a compass rose. Parallel rules are two straight edges that are mechanically connected such that both edges always remain parallel. Lines can then be "walked" across a flat chart.

Parallels
Latitude lines.

Parcel
Material wrapped around a line to prevent chaffing.

Parrot beak
A clip at the end of a spinnaker pole to hold the guy.

Partners
Supporting structures used to support areas where high loads come through openings in the deck, such as at the mast boot.

Passage
A journey from one place to another.

Patant log
A type of log that uses a counter attached to a rotor on a line which is towed behind the boat to help measure distance and speed.

Pay out
To let out.

Pedestal
The column that the wheel is mounted on.

Pylorus
A card marked in degrees and having sightings on it that is used to take bearings relative to the ship, rather than magnetic bearings as taken with a compass.

Pendant
A small line attached to a mooring chain. Also sometimes called a pennant.

Pennant
(1) A small flag, such as can be used for signaling. Flags can be used together to spell words or individually as codes, such as the quarantine flag.
(2) A small line attached to a mooring chain, sometimes called a pendant.

Personal floatation device
PFD for short. A device used to keep a person afloat. Also called a life jacket, life preserver or life vest.

PFD
Personal Floatation Device. A device used to keep a person afloat. Also called a life jacket, life preserver or life vest.

Pier
A place extending out into the water where vessels may dock. Usually made out of wood or cement.

Pile, piling
A pole embedded in the sea bottom and used to support docks, piers and other structures.

Pilot
An individual with specific knowledge of a harbor, canal, river or other waterway, qualified to guide vessels through the region. Some areas require that boats and ships be piloted by a licensed pilot.

Piloting
The act of guiding a vessel through a waterway.

Pinch
Steering a sailboat too close to the eye of the wind, causing the sails to luff.

Pintle
A pin used to attach a stern mounted rudder. The hole that the pin fits is known as a gudgeon.

Pitch poled
When a boat's stern is thrown over its bow.

Pitch
(1) A fore and aft rocking motion of a boat. Also see roll and yaw.
(2) How much a propeller is curved.
(3) A material used to seal cracks in wooden planks.

Planing hull
A hull design that is capable of planing.

Planing speed
The speed needed for a boat to begin planing.

Planing A boat rising slightly out of the water so that it is gliding over the water rather than plowing through it.

Planking
Wood strips used to cover the deck or hull of a wooden vessel.

Plot
To find a ship's actual or intended course or mark a fix on a chart.

Plow anchor
Also called a CQR or coastal quick release anchor. An anchor that is designed to bury itself into the ground by use of its plow shape.

Plug
(1) A tapered device, usually made from wood or rubber, which can be forced into a hole to prevent water from flowing through it. Plugs should be available to fit every through hull.
(2) The act of using anything to stop the water from flowing through a hole.

Point of sail
The position of a sailboat in relation to the wind. A boat with its head into the wind is known as "head to wind" or "in irons". The point of sail with the bow of the boat as close as possible to the wind is called close hauled. As the bow moves further from the wind, the points of sail are called: close reach, beam reach, broad reach, and running. The general direction that a boat is sailing is known as its tack.

Point
(1) To sail as close as possible to the wind. Some boats may be able to point better than others, sailing closer to the wind.
(2) The named directions on a compass such as north, northeast, etc.

Polaris
Polaris, the North Star, is visible in the northern hemisphere and indicates the direction of north. In the southern hemisphere the Southern Cross is used to find the direction of south.

Pole
(1) A spar. Such as a pole used to position a sail.
(2) One of the two points around which the earth spins, known as the north and south poles.
(3) One of the two points that the earth's magnetic field emits from, the magnetic north and south poles.

Poop deck
A boat's aft deck.

Pooped
A wave that breaks over the stern of the boat.

Port tack
A sailboat sailing on a tack with the wind coming over the port side and the boom on the starboard side of the boat. If two boats under sail are approaching, the one on port tack must give way to the boat on starboard tack.

Port
(1) The left side of the boat from the perspective of a person at the stern of the boat and looking toward the bow. The opposite of starboard.
(2) A place where ships go to dock.
(3) A porthole. A window in the side of a boat, usually round or with rounded corners. Sometimes portholes can be opened, sometimes they are fixed shut. Also see hatches

Porthole
A port. A window in the side of a boat, usually round or with rounded corners. Sometimes portholes can be opened, sometimes they are fixed shut. Also see hatches.

Position doubtful
A mark of PD made on a chart when plotting a boat's position to indicate that there is reason to doubt that the fix is accurate.

Pound
The action of a boat's bow repeatedly slamming into oncoming waves.

Pram
A type of dinghy with a flat bow.

Preferred channel buoy
Also known as a junction buoy. A red and green horizontally striped buoy used in the United States to mark the separation of a channel into two channels. The preferred channel is indicated by the color of the uppermost stripe. Red on top indicates that the preferred channel is to the right as you return. Also see can and nun buoys.

Prevailing winds
The typical winds for a particular region and time of year.

Preventer
A line run forward from the boom to a secure fitting to prevent the boom from jibing accidentally when running. If the boat jibes anyway, this can cause the sail to become backwinded.

Prime meridian
The 0° longitude line that runs through Greenwich, England.

Privileged vessel
The vessel that is required to maintain its course and speed when boats are approaching each other according to the navigation rules. Also known as the stand on vessel.

Prop
Slang for propeller.

Propane
Also known as LPG (liquid petroleum gas). Propane is a common fuel used for cooking and heating. CNG (natural gas) is considered safer because propane is heavy than air and will sink into the bilge if it leaks, creating the potential for an explosion. Propane is more easily available throughout the world than CNG however, so it is used for most boats outside of North America.

Propeller shaft
The spinning shaft from the engine to which the propeller is attached.

Propeller
An object with two or more twisted blades that is designed to propel a vessel through the water when spun rapidly by the boat's engine.

Protractor
A navigation tool used to measure angles on a chart.

Prow
The part of the bow forward of where it leaves the waterline.

Pulpit
A sturdy railing around the deck on the bow.

Pump out
Removing waste from a holding tank.

Purchase
Two or more blocks connected to provide a mechanical advantage when lifting heavy objects.

Pushpit
Also called stern pulpit. A sturdy railing around the deck at the stern.

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Q

Quadrant
A device connected to the rudder that the steering cables attach to.

Quarantine flag
The Quebec pennant is flown when first entering a country, indicating that the people on the ship are healthy and that the vessel wants permission to visit the country.

Quarter
The side of a boat aft of the beam. There are both a port quarter and a starboard quarter.

Quartering sea
A sea which comes over the quarter of the boat.

Quarters
Sleeping areas on the boat.

Quay
Also a wharf. A section parallel to the shore for docking and unloading vessels.

Quick flashing light
A navigational aid with a light that flashes about once per second.

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R

Radar arch
An arch to mount the radar, usually at the stern of the boat.

Radar reflector
An object designed to increase the radio reflectivity of a boat so that it is more visible on radar. Many small boats are made with fiberglass and other materials that do not reflect radar very well on their own.

Radar
Radio detection and ranging. An electronic instrument that uses radio waves to find the distance and location of other objects. Used to avoid collisions, particularly in times of poor visibility.

Radio beacon
A navigational aid that emits radio waves for navigational purposes. The radio beacon's position is known and the direction of the radio beacon can be determined by using a radio direction finder.

Radio bearing
A bearing taken with a radio direction finder toward a radio beacon.

Radio direction finder
RDF for short. An instrument that can determine the direction that a radio transmission is coming from. The RDF is used with a radio beacon to find a radio bearing to help determine the vessel's position.

Radio
An instrument that uses radio waves to communicate with other vessels. VHF (very high frequency) radios are common for marine use, but are limited in range. Single side band (SSB) radios have longer ranges.

Radiowaves
Invisible waves in the electromagnetic spectrum that are used to communicate (radio) and navigate (radar, RDF.)

Raft
(1) A small flat boat, usually inflatable.
(2) To moor with more than one boat tied together, usually using only one boat's ground tackle.

Rail
The edge of a boat's deck.

Rake
A measurement of the top of the mast's tilt toward the bow or the stern.

Range
(1) distance a boat can travel with its available fuel and supplies.
(2) The difference between high and low tides.
(3) Two lights or daymarks that can be aligned with one behind another to indicate that one is positioned on a line on a chart, typically used to guide a boat into a channel.

Ratlines
Small lines tied between the shrouds to use as a ladder when going aloft.

RDF
Radio direction finder. An instrument that can determine the direction that a radio transmission is coming from. The RDF is used with a radio beacon to find a radio bearing to help determine the vessel's position.

Reaching
Any point of sail with the wind coming from the side of the boat. If the wind is coming from directly over the side, it is a beam reach. If the boat is pointed with its bow more directly into the wind it is a close reach. If the wind is coming from over the quarter, it is called a broad reach.

Reciprocal
A bearing 180° from the other. A direction directly opposite the original direction.

Red buoy
A nun buoy. A conical buoy with a pointed top, painted red, and having an even number, used in the United States for navigational aids. At night they may have a red light. These buoys should be kept on the right side of the boat when returning from a larger body of water to a smaller one such as a marina. Can buoys are used on the opposite side of the channel. Also see green and red daymarks.

Red daymark
A navigational aid used in the United States and Canada to mark a channel. Red square daymarks should be kept on the right when returning from a larger to smaller body of water. Green daymarks mark the other side of the channel. Also see can and nun buoys.

Reef cringles
Reinforced cringles in the sail designed to hold the reefing lines when reefing the sail.

Reef knot
Also known as the square knot. This knot is an unreliable knot used to loosely tie lines around the bundles of sail that are not in use after reefing.

Reef points
Points where lines have been attached to tie the extra sail out of the way after reefing.

Reef
(1) To partially lower a sail so that it is not as large. This helps prevent too much sail from being in use when the wind gets stronger.
(2) A line of rock and coral near the surface of the water.

Reefing lines
Lines used to pull the reef in the sail. The reef line will pass through reef cringles, which will become the new tack and clew of the reefed sail.

Reeve
Leading a line through a block or other object.

Regatta
A series of boat races.

Relative bearing
A bearing relative to the boat or another object, rather than a compass direction.

Rhumb line
A line that passes through all meridians at the same angle. When drawn on a Mercator chart, the rhumb line is a straight line. However the Mercator chart is a distortion of a round globe on a flat surface, so the rhumb line will be a longer course than a great circle route.

Ride out
To weather a storm, either at sea or at anchor.

Riding light
Anchor light. A white light displayed from the top of the mast to indicate that the boat is at anchor.

Riding sail
Also called a stability sail or steadying sail. Any small sail set to help the boat maintain its direction without necessarily moving, as when at anchor or in heavy weather.

Rig
(1) A combination of sails and spars.
(2) To prepare the rig before sailing.

Rigging
The wires, lines, halyards and other items used to attach the sails and the spars to the boat. The lines that do not have to be adjusted often are known as standing rigging. The lines that are adjusted to raise, lower and trim the sails are known as running rigging.

Right
To return a boat that is not upright to its upright position.

Rigid inflatable
A small inflatable boat that has a solid hull but has buoyancy tubes that are inflated to keep it afloat.

Roach
A curve out from the aft edge (leech) of a sail. Battens are sometimes used to help support and stiffen the roach.

Roaring Fourties
A region between 40° south and 50° south where westerly winds circle the earth unobstructed by land.

Rode
Anchor rode. A line or chain attached to the anchor.

Roll
A side to side motion of the boat, usually caused by waves. Also see pitching and yawing.

Roller furling
A method of storing a sail usually by rolling the jib around the headstay or the mainsail around the boom or on the mast.

Roller reefing
A system of reefing a sail by partially furling it. Roller furling systems are not necessarily designed to support the loads of reefing.

Rolling hitch
A knot used to attach a line to a spar or similar object.

Rope
Traditionally a line must be over 1 inch in size to be called a rope.

Row
A method of moving a boat with oars. The person rowing the boat faces backwards, bringing the blade of the oars out of the water and toward the bow of the boat. They then pull the oars through the water toward the stern of the boat, moving the boat forward.

Rowboat
A small boat designed to be rowed by use of its oars. Some dinghies are rowboats.

Rub rail, rub strake, rub guard
A rail on the outside of the hull of a boat to protect the hull from rubbing against piles, docks and other objects.

Rudder post
The post that the rudder is attached to. The wheel or tiller is connected to the rudder post.

Rudder
A flat surface attached behind or underneath the stern used to control the direction that the boat is traveling.

Rules of the Road
The rules concerning which vessel has the right of way if there is a possibility of collision between two or more boats. The United States Inland Rules of the Road and International Rules of the Road are slightly different.

Run aground
To take a boat into water that is too shallow for it to float in, i.e: the bottom of the boat is resting on the ground.

Runners
Also known as running backstays. Adjustable stays used to control tension on the mast.

Running backstay
Also known as runners. Adjustable stays used to control tension on the mast.

Running bowline
A type of knot that tightens under load. It is formed by running the standing line through the loop formed in a regular bowline.

Running fix
A fix taken by taking bearings of a single object over a period of time. By using the vessel's known course and speed, the location of the vessel can be found.

Running lights
Navigational lights that are required to be used when a vessel is in motion.

Running rigging
The lines and wires (rigging) that are used to raise, lower and adjust the sails.

Running
(1) A point of sail where the boat has the wind coming from aft of the boat. Running can cause the danger of an accidental jibe.
(2) Used to describe a line that has been released and is in motion.

Back to the Top

S

Safe overhead clearance
A distance that needs to be kept between the mast and overhead electrical lines to prevent electrical arcing.

Safety harness
A device worn around a person's body that can be attached to jack lines to help prevent a person from becoming separated from the boat.

Safety pin
(1) Any pin that is used to prevent a fitting from falling open.
(2) A pin used to keep the anchor attached to its anchor roller when not in use.

Sail shape
The shape of a sail, with regard to its efficiency. In high winds a sail would probably be flatter, in low winds rounder. Other circumstances can cause a sail to twist. Controls such as the Cunningham, boom vang, outhaul, traveler, halyards, leech line, sheets, and the bend of the mainmast all can affect sail shape. Also see sail trim.

Sail track
A slot into which the bolt rope or lugs in the luff of the sail are inserted to attach the sail. Most masts and roller reefing jibs use sail tracks. Systems with 2 tracks can allow for rapid sail changes.

Sail trim
The position of the sails relative to the wind and desired point of sail. Sails that are not trimmed properly may not operate efficiently. Visible signs of trim are luffing, excessive heeling, and the flow of air past telltales. Also see sail shape.

Sail
(1) A large piece of fabric designed to be hoisted on the spars of a sailboat in such a manner as to catch the wind and propel the boat.
(2) The act of using the wind to propel a sailboat.

Sailboat
A boat which uses the wind as its primary means of propulsion.

Sailcloth
A fabric, usually synthetic, used to make sails.

Sailing directions
Books that describe features of particular sailing areas, such as hazards, anchorages, etc.

Sampson post
A strong post used for to attach lines for towing or mooring.

Sand bar
An area in shallow water where wave or current action has created a small, long hill of sand. Since they are created by water movement, they can move and may not be shown on a chart.

Satellite navigation
Navigation using information transmitted from satellites. See Global Positioning System.

Scale
To climb.

Scend
The distance that the trough of a wave is below the average water level. With large waves in shallow water the scend is important to help determine whether a boat will run aground.

Schooner
A sailboat with two or more masts. The aft mast is the same size or larger than the forward one(s). Also see ketch and yawl.

Scope
The length of the anchor rode relative to the depth of the anchor. For example 100 feet of anchor rode in 20 feet of water would be a scope of 5:1. A scope of 7:1 or more is usually used depending on the holding ground. Too little scope can cause the anchor to drag. Increased scope increases the swinging room.

Scow
A boat with a flat bottom and square ends.

Screw
A propeller or type of fastener.

Scud
To run before the wind in a storm.

Scull A method of moving a boat by using a single oar at the stern.

Scupper
An opening through the toe rail or gunwale to allow water to drain back into the sea.

Scuttle
To sink a boat.

Scuttlebutt
Gossip. People talking about things that may or may not be true, usually about other people or events. The term scuttlebutt evolved from the name of a keg containing water and alcohol that sailors used to gather about before meals.

Sea anchor
A drogue designed to bring a boat to a near stop in heavy weather. Typically a sea anchor is set off of the bow of a boat so that the bow points into the wind and rough waves.

Sea buoy
The last buoy as a boat heads to sea.

Sea cock
A valve used to prevent water from entering at a through hull.

Sea kindly
A boat that comfortable in rough weather.

Sea level
The average level of the oceans, used when finding water depths or land elevations.

Sea room
Room for a boat to travel without danger of running aground.

Sea
(1) A body of salt water. A very large body of fresh water.
(2) Any body of salt water when talking about its condition or describing the water around a boat. Heavy seas for example.

Seagoing
A vessel designed to be able to cross oceans.

Seamanship
The ability of a person to motor or sail a vessel, including all aspects of its operation.

Secondary port
A port that is not directly listed in the tide tables but for which information is available as a difference from a nearby standard port.

Sector light
A navigational light that is visible only for a specific sector or arc of a circle, enabling a boat to determine that it lies within that sector. Sector lights might mark the entrance to a channel.

Sector
An arc of a circle in which certain types of navigational lights known as sector lights are visible.

Secure
To make fast. To stow an object or tie it in place.

Securite
A type of warning message transmitted by radio. Securite messages are used to warn of impending storms, navigational hazards and other potential problems that are not immediately life threatening by themselves. MAYDAY and PAN PAN are used for more immediate problems.

Seizing
Tying two lines, or a spar and a line together, by using a small line.

Self bailing
Said of an area, such as the cockpit, that is capable of rapidly draining away any water that may fill the area.

Self draining
A locker or other area equipped with a drain capable of allowing any water that may collect in it to leave, such as from wet clothes or equipment.

Self steering gear
A device used to keep a sailboat on the same heading relative to the wind without aid of a person. Self steering gear is a mechanical system using a wind vane instead of electrical power as does an autopilot.

Semaphore
A method of signaling using two flags held in position by the signaler.

Sentinel
A weight hung from the anchor chain in order to keep the anchor lying as flat as possible to prevent dragging.

Separation zone
A region drawn on a chart to separate two lanes that have shipping vessels moving in opposite directions.

Serve
To wind small line around a rope to protect it from chaffing and weather.

Set
(1) To put an object in place, as in "set the anchor."
(2) The manner in which an object is in place. "Are the sails set correctly?"
(3) The direction that a current is moving.

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
A metal U-shaped connector that attaches to other fittings with the use of a pin that is inserted through the arms of the U.

Shake out
To remove a reef from a sail.

Shakedown
An initial trip with a boat to make sure that everything is operating properly.

Shank
The long bar part of an anchor. The flukes are at one end of the shank and the stock is at the other.

She
All boats are referred to as female. "She is at anchor." "Her sails are set."

Shear pin
A pin attaching one part to another that is designed to break if excessive loads are applied. For example to connect the propeller to the propeller shaft so that the pin can break if the propeller strikes something, preventing damage to the propeller and engine.

Sheathing
A covering to protect the bottom of a boat.

Sheave
A wheel used to change the direction of a line, such as in a block or at the top of the masthead.

Sheepshank
A knot used to temporarily shorten a line.

Sheer strake
The top plank on the side of a wooden boat that follows the sheer of the deck.

Sheer
(1) The fore and aft curvature of the deck.
(2) A sudden change of course.

Sheet bend
A type of knot used to tie two lines together.

Sheet
A line attached to the clew of a sail and is used to control the sail's trim. The sheets are named after the sail, as in jib sheets and main sheet.

Ship
(1) A large vessel.
(2) To take an object aboard, such as cargo, or water.
(3) To put items such as oars on the boat when not in use.

Shipshape
Neat, orderly and ready to use.

Shoal
(1) Shallow water.
(2) An underwater sand bar or hill that has its top near the surface.

Shore
The edge of the land near the water.

Shoreline
Where the land meets the water.

Short splice
A quickly made splice joining two lines together. A short splice is wider than the original line and will not fit through blocks or fairleads.

Shove off
To push a boat, as from a dock or another boat.

Shroud
Part of the standing rigging that helps to support the mast by running from the top of the mast to the side of the boat. Sailboats usually have one or more shrouds on each side of the mast.

Side lights
Green and red lights on the starboard and port sides of the boat required for navigation at night. Each light is supposed to be visible through an arc of 112.5°, beginning from directly ahead of the boat to a point 22.5° aft of the beam.

Sideslip
The tendency of a boat to move sideways in the water instead of along its heading due to the motion of currents or leeway.

Sight reduction tables
Tables containing information about the position of the sun, moon, planets and stars. When using celestial navigation these tables help find the position of a boat.

Signal halyard
A halyard used to hoist signal flags.

Single sideband
A type of radio carried on a boat to transmit long distances.

Sink
(1) To go to the bottom of the water.
(2) To cause an object to go to the bottom of the water.

Sister ship
A vessel of a similar design to another.

Skeg
Any flat protrusion on the outside of the hull that is used to support another object such as the propeller shaft or rudder.

Skiff
A small boat.

Skin
The outside surface of a boat. Usually used when describing a fiberglass or other molded hull.

Slack water
A period of almost no water movement between flood and ebb tides

Slack
(1) A line that is loose.
(2) To ease a line.

Slide
Also called a lug. Metal or plastic pieces attached to a sail's luff that slide in a mast track to allow easy hoisting of a sail.

Sling
(1) Lines used to hoist heavy or awkward objects.
(2) The act of using such lines to hoist heavy or awkward objects.
(3) Ropes used to secure the center of a yard to the mast.

Slip
A space between two docks or piers where a boat can be moored.

Sloop
A style of sailboat characterized by a single mast with one mainsail and one foresail. Also see cutter.

Slot
The opening between the jib and the mainsail. Wind passing through this opening increases the pressure difference across the sides of the mainsail, helping to move the boat forward.

Small stuff
Small lines used when whipping and serving.

Snap hook
A metal fitting with a arm that uses a spring to close automatically when connected to another object.

Snatch block
A block that can be opened on one side, allowing it to be place on a line that is already in use.

Snub
To suddenly stop or secure a line.

Soft eye
An eye splice that does not use a protective insert.

Sole
A floor on a boat.

Sound
Signals required by navigation rules describing the type of vessels and their activities during times of fog.

Sounding
The depth of the water as marked on a chart.

South Pole
The "bottom" point of the line about which the earth rotates.

South wind, southerly wind
Wind coming from the south.

South
One of the 4 cardinal compass points. South is the direction toward the South Pole and is at 180° on a compass card.

Southern Cross
A constellation in the shape of a cross used to determine the direction of the South Pole when traveling in the southern hemisphere.

Spar buoy
A tall buoy used as a navigational aid.

Spar
A pole used as part of the sailboat rigging, such as masts, booms, spinnaker poles and gaffs.

Spell
To relieve someone when taking turns at a task, such as manning the helm.

Spherical buoy
A ball shaped buoy marking a navigational hazard.

Spider band
A metal band around a spar with an eye to take the shackles used on the running rigging.

Spill the wind
To head up into the wind or loosen a sail, allowing the sail(s) to luff.

Spindle buoy
A tall cone shaped navigational buoy.

Spinnaker halyard
A halyard used to raise the spinnaker.

Spinnaker pole lift
Also spinnaker lift. A line running from the top of the mast, used to hold the spinnaker pole in place.

Spinnaker pole
Sometimes spinnaker boom. A spar used to extend the foot of the spinnaker beyond the edge of the boat, and to secure the corner of the sail.

Spinnaker
A very large lightweight sail used when running or on a broad reach.

Spitfire
A storm jib. A small jib made out of heavy cloth for use in heavy weather. Sometimes brightly colored.

Splice
The place where two lines are joined together end to end.

Spreader
Small spars extending toward the sides from one or more places along the mast. The shrouds cross the end of the spreaders, enabling the shrouds to better support the mast.

Spring line
Docking lines that help keep the boat from moving fore and aft while docked. The after bow spring line is attached near the bow and runs aft, where it is attached to the dock. The forward quarter spring line is attached to the quarter of the boat, and runs forward, being attached to the dock near the bow of the boat.

Spring tide
The tide with the most variation in water level, occurring during new moons and full moons. This is the time of the highest high tide and the lowest low tide. The opposite of a neap tide.

Spring
To begin, as in "to spring a leak."

Squall
A sudden intense wind storm of short duration, often accompanied by rain. Squalls often accompany an advancing cold front.

Square knot
Reef knot. A simple knot that can slip. Often used on sailboats when reefing.

Square rigged
A sailboat having square sails hung across the mast.

Square sail
A square sail hung from a yard on the mast. Best used when sailing down wind.

SSB
Single sideband radio. A type of radio used on a boat to transmit for long distances.

Stability sail
A vertical pole on which flags can be raised.

Stability
Ability of a boat to keep from heeling or rolling excessively, and the ability to quickly return upright after heeling.

Stall
(1) To stop moving.
(2) Air is sail to stall when it becomes detached from the surface it is flowing along. Usually air travels smoothly along both sides of a sail, but if the sail is not properly trimmed, the air can leave one of the sides of the sail and begin to stall. Stalled sails are not operating efficiently.

Stanchion
A post near the edge of the deck used to support life lines.

Stand on vessel
The vessel that is required to maintain its course and speed when boats are approaching each other according to the navigation rules. Also known as the privileged vessel.

Standard port
A port for which information is listed in the tide tables. Other ports known as secondary ports have information listed as a difference from the standard port rather that having complete tables.

Standing rigging
The rigging of a boat that does not normally need to be adjusted.

Standing
The part of the line that will carry the load after a knot has been tied in it.

Starboard tack
A sailboat sailing on a tack with the wind coming over the starboard side and the boom on the port side of the boat. If two boats under sail are approaching, the one on port tack must give way to the boat on starboard tack.

Starboard
The right side of a boat, from the perspective of a person at the stern of the boat and looking toward the bow. The opposite of port.

Stateroom
Sleeping quarters for the boat's captain or guests.

Statute mile
A mile as measured on land, 5280 feet or 1.6 kilometers. Distances at sea are measured as nautical miles.

Stay
Lines running fore and aft from the top of the mast to keep the mast upright. Also used to carry some sails. The backstay is aft of the mast and the forestay is forward of the mast.

Staysail
A triangular sail similar to the jib set on a stay forward of the mast and aft of the headstay.

Steadying sail
Also stability sail or riding sail. Any small sail set to help the boat maintain its direction without necessarily moving, as when at anchor or in heavy weather.

Steaming light
Also known as a masthead light. The steaming light is a white light that is visible for an arc extending across the forward 225° of the boat. When lit the steaming light indicates that a vessel under power, including sailboats with engines running. Steaming lights are usually located halfway up the mast rather than at the top.

Steep seas
Tall and short waves caused by water current and wave directions being opposite to the direction of the wind.

Steerage way
In order for the rudder to be able to properly steer the boat, it must be moving through the water. The speed necessary for control is known as steerage way.

Stem
The forward edge of the bow. On a wooden boat the stem is a single timber.

Step
(1) A fitting for the bottom of the mast (mast step.)
(2) The act of placing the foot of the mast in its step and raising the mast.

Stepped
(1) A mast that is in place is stepped.
(2) Where the mast is stepped, as in keel stepped or deck stepped.

Stern light
A white running light placed at the stern of the boat. The stern light should be visible through an arc of 135°, to the rear of the boat.

Stern line
A line running from the stern of the boat to a dock when moored.

Stern pulpit
Pushpit. A sturdy railing around the deck at the stern.

Stern
The aft part of a boat. The back of the boat.

Sternway
Making way in reverse.

Stiff
A boat that resists heeling.

Stock
A crossbeam at the upper part of an anchor.

Stopper knot
A knot used in the end of a line to prevent the end from running through a block or other narrow space. Stopper knots prevent a line that slips from unthreading itself and getting lost.

Stopper
A mechanical device or knot used to keep a rope from running.

Stores
Supplies on a boat.

Storm jib
Sometimes called a spitfire. A small jib made out of heavy cloth for use in heavy weather. Sometimes brightly colored.

Storm sail
The storm jib and storm trysail. Small sails built from heavy cloth for use during heavy weather.

Storm trysail
A very strong sail used in stormy weather. It is loose footed, being attached to the mast, but not the boom. This helps prevent boarding waves from damaging the sail or the rigging.

Stow
To put something away.

Strakes
A row of wooden planks on the hull of a wooden boat or fiberglass on a more modern fiberglass boat.

Strike
To lower.

Strop
A length of line used in connecting two parts of a boat or its rigging.

Strum box A strainer in the bilge so that the bilge pump doesn't get clogged.

Stuffing box
A fitting around the propeller shaft to keep the bearing lubricated and to keep water out of the boat.

Superstructure
Cabins and rooms above the deck of a ship.

Surf
(1) The breaking waves and resulting foam near a shore.
(2) The sport of riding breaking waves on a board.

Survey
An inspection of a boat to determine its condition.

Surveyor
A person who is qualified to inspect a boat in order to determine its condition.

Swab
(1) A mop made from rope.
(2) To use such a mop.

Swallow
The place between the sheave (roller) and housing of a block, through which the line is run.

Swamp
To fill with water.

Swell
Large smooth waves that do not crest. Swells are formed by wind action over a long distance.

Swim platform
A platform, usually on the transom, allowing swimmers to easily climb back onto a boat.

Swing a compass
The act of checking compass readings against known headings in order to determine the compass error.

Swinging bridge
A bridge that swings away from the waterway so that boats may pass beside it.

Swinging circle, swinging room
The distance a boat can move around its anchor. Swinging room is important because if other boats or objects are within a boat's swinging circle they may collide.

Swivel
A rotating fitting used to keep a line from tangling.

Back to the Top

T

Tabernacle
A hinged support for the bottom of a mast so that the mast can be lowered easily when passing under bridges.

Tachometer
A gauge that measures engine revolutions per minute.

Tack
(1) The lower forward corner of a triangular sail
(2) The direction that a boat is sailing with respect to the wind. See also port tack and starboard tack.
(3) To change a boat's direction, bringing the bow through the eye of the wind.

Tacking
(1) To change a boat's direction, bringing the bow through the eye of the wind.
(2) To tack repeatedly, as when trying to sail to a point up wind of the boat.

Tackle
Lines used with blocks in order move heavy objects.

Taffrail
A rail around the stern of a boat.

Tail
(1) The end of a line.
(2) A line attached to the end of a wire to make it easier to use.
(3) To gather the unused end of a line neatly so that it does not become tangled.

Take in
(1) To remove a sail.
(2) To add a reef to a sail.

Tall buoy
Also called a Dan buoy. A float with a flag at the top of a pole. Used to mark a position such as for a race or a man overboard.

Tang
A metal fitting on the mast that the spreaders are attached to.

Telltale
A small line free to flow in the direction of the breeze. It is attached to sails, stays in the slot, and in other areas, enabling the helmsman and crew to see how the wind is flowing. Proper use of the telltales can help sailors improve their sail trim.

Tender
(1) A small boat used to ferry people and supplies between a larger boat and the shore. See dinghy.
(2) Used to describe a boat that heels easily.

Tenon
The bottom of the mast, with a shape designed to fit into the mast step.

Thimble
A metal fitting used to strengthen an eye splice (loop) made in a rope or wire.

Throat
The forward upper corner of a four cornered sail known as a gaff rigged sail.

Through hull
Fittings attached through the hull to which a sea cock and hose, a transducer, or other device is attached. Through hulls are used to expel waste water, such as from a sink, to let sea water in, such as for engine cooling, and to allow placement of sensors such as depth gauges. A sea cock is attached directly to the through hull before any hoses are attached so that the flow of water can be easily shut off if the hose fails. Plugs should be available to force into a through hole in case the through hole fails. Transducers should be equipped with caps to place over the hole should the transducer itself need to be removed.

Thwart
A seat running across the width a small boat.

Thwartships
Also athwartships. Across the width of a boat.

Tidal atlas
Small charts showing tidal stream directions and rate of flow.

Tidal current
Also called tidal stream. The flowing of water caused by the rising and lowering tidal waters.

Tidal range
The difference of a tide's high and low water levels.

Tidal stream
The flow of water caused by rising and lowering tides.

Tide tables
Tables containing information about the time of the high and low tides and the water level to be expected at that time.

Tide
The predictable, regular rising and lowering of water in some areas due to the pull of the sun and the moon. Tidal changes can happen approximately every 6 or 12 hours depending on the region. To find out the time and water levels of different tides, you can use tide tables for your area. The period of high water level is known as high tide and the period of low water level is known as low tide. In the Bay of Fundy, the tidal range exceeds 40 feet (13 meters.)

Tiller extension
Also hiking stick. An extension to the tiller allowing the helmsman to steer while hiking. Commonly found on racing boats, they can help improve visibility or stability.

Tiller
An arm attached to the top of the rudder to steer a small boat. If the helmsman wants to steer to starboard he pushes the tiller to port. Larger boats usually use a wheel instead of a tiller.

Time zone
Regions of about 15° of longitude around the world where time is measured on a local scale. Each time zone keeps time slightly differently so that at 12:00 noon the sun will be high in the sky. For example at noon in England it is midnight in New Zealand. If New Zealanders kept their clocks set to the English time zone, it would be very dark at noon!

Toe rail
A small rail around the deck of a boat. The toe rail may have holes in it to attach lines or blocks. A larger wall is known as a gunwale.

Tonnage
The weight or displacement of a ship.

Top heavy
A boat that has too much weight up high. This can adversely affect the boat's stability.

Top mast
A mast on top of another mast.

Topmark
A mark on the top of a navigational buoy or daybeacon.

Topping lift
A line running from the end of the boom to the top of the mast used to keep the boom from falling when the sail is not set.

Topsail
A triangular sail set above the gaff on a gaff rigged boat.

Topsides
The sides of the hull above the waterline and below the deck.

Tow
To pull a boat with another boat, such as a tugboat towing a barge.

Towing light
Running lights that should be used by boats when towing to indicate that a tow is in progress.

Track
(1) The path that a vessel is taking.
(2) A guide in the mast or other spar that accepts lugs to attach a sail.
(3) A rail to which a sliding car is attached for easy adjustment of the position of blocks and lines.

Trade wind
Winds in certain areas known for their consistent strength and direction. Trade winds are named because of their reliability, allowing for planned voyages along the routes favored by those winds.

Trailing edge
The aft edge of a sail, more commonly called the leech.

Transducer
An electronic device that uses sound waves to collect information such as water depth and vessel speed, usually attached to a through hull. The transducer then converts that information to electrical signals that can be used by electronic displays in the cockpit.

Transit
Also called a range. Two navigational aids separated in distance so that they can be aligned to determine that a boat lies on a certain line. Transits can be used to determine a boat's position or guide it through a channel.

Transom
The aft side of the hull.

Trapeze
A belt and line used to help a crew hike out beyond the edge of a boat to counteract the boat's heel. Usually used on small vessels for racing.

Traveler
A track or rod with an attached block, allowing more controlled adjustment of a sail's sheet. The traveler allows better control of the sail's shape.

Triadic stay
A stay leading from one mast, such as the main mast to another, such as the mizzen mast.

Tricolor light
A running light allowed on some sailboats instead of the normal bow and stern lights. The tricolor light contains the red and green side lights and the white stern light in a single fitting that is attached to the top of the mast.

Trim tab
An adjustable section of the rudder that allows the rudder to be corrected for lee helm or weather helm.

Trim
(1) To haul in on a sheet to adjust the sail trim.
(2) Sail trim.
(3) A properly balanced boat that floats evenly on its waterline. Improperly trimmed boats may list or lie with their bow or stern too low in the water.

Trimaran
A boat with a center hull and two smaller outer hulls called amas. Also see catamaran and monohull.

Trip line
A line attached to the end of an anchor to help free it from the ground.

Tropic of Cancer
A line 23 degrees, 27 minutes north of the equator. On June 21 the sun is directly above the Tropic of Cancer, at all other times the sun is further south.

Tropic of Capricorn
A line 23 degrees, 27 minutes south of the equator. On December 22 the sun is directly above the Tropic of Capricorn. At all other times the sun is further north.

Tropics
The region around the equator between the Tropic of Cancer and the Tropic of Capricorn. The tropics are known for their warm weather.

Trough
The bottom of a wave, the valley between the crests.

Truck
A cap for the top of the mast.

True course
The course of a boat after being corrected for magnetic deviation and magnetic variation.

True north
Geographic north. Toward the North Pole.

True wind
The speed and direction of the wind. The motion of a boat will cause the wind to appear to be coming at a different direction and speed, which is known as apparent wind

Trunk
The place that the centerboard or daggerboard retracts into.

Trunnion hoop
A hinged fitting at the top of a mast to hold another mast above it.

Trysail
Also called storm trysail. A very strong sail used in stormy weather. It is loose footed, being attached to the mast, but not the boom. This helps prevent boarding waves from damaging the sail or the rigging.

Tugboat
A small powerful boat used to help move barges and ships in confined areas.

Tune
To adjust the standing rigging or other equipment to make a boat perform better.

Turn turtle
For a boat to turn completely over such that its mast is pointing down instead of up.

Turnbuckle
A metal fitting that is turned to tighten or loosen the tension on standing rigging.

Turning circle
The distance required for a boat to turn in a complete circle.

Turtle
A bag in which a spinnaker or other large sail can be stowed with the lines attached so that it can be rapidly raised.

Twine
Small line used for whipping other light duties also known as small stuff.

Two half hitches
A knot with two half hitches (loops) on the standing part of the line.

Typhoon
A strong tropical revolving storm of force 12 or higher in the southern hemisphere. Typhoons revolve in a counterclockwise direction. In the northern hemisphere these storms revolve clockwise and are known as hurricanes.

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U

Under bare poles
Having no sails up. In heavy weather the windage of the mast and other spars can still be enough to move the boat.

Under the lee
On the lee side of an object, protected from the wind.

Under way
A vessel in motion is under way.

Undertow
Strong offshore current extending to the shore.

Unfurl
To unfold or unroll a sail. The opposite of furl.

Upwind
To windward, in the direction of the eye of the wind.

USCG
United States Coast Guard.

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V

Vane
A flat device that is affected by the wind. Vanes are used in wind direction indicators and some self steering gear systems.

Vang
A hydraulic ram or block and tackle used to hold the end of the boom down.

Variable pitch
A type of propeller that has adjustable blades for varying speeds or directions, and may be able to reduce drag when under sail.

Variation
Magnetic variation. The difference between magnetic north and true north, measured as an angle. Magnetic variation is different in different locations, so the nearest compass rose to each location on a chart must be used.

Vector
A line drawn to indicate both the direction and magnitude of a force, such as leeway or a current.

Veer
A shifting of the wind direction, opposite of backing. Clockwise in the northern hemisphere, counter-clockwise in the southern hemisphere.

Velocity made good
Also VMG. Actual boat speed after adjusting for such factors as current and leeway.

Vertical clearance
The distance between the water level at chart datum and an overhead obstacle such as a bridge or power line.

Very quick flashing
A navigational aid with a light that flashes between 80 and 159 times per minute. Usually around twice per second.

VHF
(1) Very High Frequency radio waves.
(2) A radio that transmits in the VHF range. VHF radios are the most common communications radio carried on boats, but their range is limited to "line of sight" between the transmitting and receiving stations. Also see single sideband.

Visual bearing
A bearing taken by visually observing the location of known landmarks.

Visual fix
A fix taken by visually observing the location of known landmarks.

VMG
Velocity made good. Actual boat speed after adjusting for such factors as current and leeway.

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W

Wake
Waves generated in the water by a moving vessel.

Watch
(1) A division of crew into shifts.
(2) The time each watch has duty.

Waterline length
The length of the boat at the waterline.

Waterline
The line where the water comes to on the hull of a boat. Design waterline is where the waterline was designed to be, load waterline is the waterline when the boat is loaded, and the painted waterline is where the waterline was painted. Actual waterline is where the waterline really is at any given time.

Waterlogged
Completely filled with water.

Waterway
A river, canal or other body of water that boats can travel on.

Way
The progress of a boat. If a boat is moving it is considered to be "making way."

Weather helm
The tendency of a boat to head up toward the eye of the wind. The opposite of lee helm.

Weigh
To raise, as in to weigh anchor.

West wind, westerly wind.
Wind coming from west.

West
One of the 4 cardinal compass points. West is at 270° on a compass card.

Wet locker
A locker equipped with a drain so that wet clothes can be stored in it without damaging other objects in the boat.

Wetted surface
The amount of area of the hull, keel, rudder, and other objects that is under water.

Wharf
Also a quay. A section parallel to the shore for docking and unloading vessels.

Wheel
One of two methods used to steer a boat. A wheel is turned in the direction that the helmsman wants the boat to go. On smaller boats a tiller is usually used, which steers in the opposite manner.

Whip
To bind the strands of a line with a small cord.

Whisker pole
A spar used to help hold the jib out when sailing off the wind.

Whistle buoy
A navigational buoy with a whistle.

Wide berth
To avoid something by a large distance.

Winch
A device used to give a mechanical advantage when hauling on the lines.

Wind scoop
A funnel used to force wind in a hatch and ventilate the below decks area.

Windage
The amount of a boat, sail or other object that the wind can push on.

Windlass
A mechanical device used to pull in cable or chain, such as an anchor rode.

Windward
In the direction of the wind. Opposite of leeward.

Wing and wing
A method of running before the wind with two sails set. Usually the mainsail on one side and a headsail on the other, or one headsail on each side.

Working sails
The sails used on a particular sailboat in normal weather conditions.

Working sheet
The sheet that is currently taught and in use to control a sail. The opposite of the lazy sheet.

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X

Y

Yacht
A sailboat or powerboat used for pleasure, not a working boat.

Yard arm
The end of a yard.

Yard
A spar attached to the mast and used to hoist square sails.

Yaw
Swinging off course, usually in heavy seas. The bow moves toward one side of the intended course. Also see rolling and pitching.

Yawl
A two masted sailboat with the shorter mizzen mast placed aft of the rudder post. A ketch is similar, but the mizzen mast is forward of the rudder post.

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Z

Zenith
The point of the celestial sphere which is directly overhead.

Zephyr
A gentle breeze. The west wind.

Zulu
Used to indicated times measured in Coordinated Universal Time, a successor to Greenwich Mean Time. A time standard that is not affected by time zones or seasons.

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