Nautical Glossary - D

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

daggerboard

1. A board, which does not pivot, dropped vertically through the hull to prevent leeway. May be completely removed for beaching or for sailing downwind.

danger bearing

A line drawn on a chart from a visible, charted object to a navigational hazard

danger buoy

A buoy marking a hazardous, dangerous spot or area

davits

Wooden or metal devices with sheaves or blocks attached on the ends, projected over a vessels sides or stern, and used to hoist up a dinghy or small boat

Davy Jone's Locker

The bottom of the sea

daymark

The colored and numbered or lettered sign placed on many beacons to identify them

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day sailor

A boat used for day sailing, typically an open boat without accommodations, rigging, or equipment needed for sailing or bunking in overnight

day's work

A record of noon-to-noon navigation work used to determine a ship's position

dead ahead

Directly ahead of the boat's course

dead astern

Directly behind, or astern, of the boat's course

dead before the wind

When the wind is directly behind, or astern, of the boat and the mainsail and boom are all the way out at right angles to the mast

deadeye

A round, flat wooden block with three holes but no sheaves, through which shroud lanyards are received

deadlight

1. A cover clamped over a porthole to protect it in heavy weather; 2. A fixed light set into the deck or cabin roof to provide light below; 3. Glass permanently set in a cabin or deck to admit light below

dead reckoning (DR)

Determining a boat's position by noting the course sailed, boat speed, and the distance covered

dead men

Neglected, old loose ends of a rope

dead rope

Line that is not led through a block or sheave

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dead run

A run when the wind is directly behind the boat

deck plate

small fitting set flush with the deck, forming the upper extremity of a piping system.

dead water

The eddy under a vessel's counter when the vessel is not in motion

dead weight tonnage

The carrying capacity of a vessel figured by weight in terms of tons or 2240 pounds

dead wood

A heavy fore-and-aft timber that lies above the keel and may extend beyond it

deck

1. A platform covering or extending horizontally across a boat 2. The floor on a boat

deck beams

Athwartships members that support the deck; their outer ends usually rest on the clamps

deck horse, boom horse, or traveler

A metal rod (or track) bolted to the deck upon which a ring (or car) of a sheet block can slide from side to side as the boom swings over on a change of tack.

deckhouse

A superstructure above the main deck level

declination

The angular distance of a heavenly body from the celestial equator measured either northward or southward on an hour circle

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deep six

1. To throw something overboard; 2. The sea, where you send unwanted items overboard

demast

1. When the mast falls over unexpectedly due to structural damage or faulty rigging; 2. To remove the mast for service, repair, storage, or transporting a boat across land 

departure

1. Exact point at which to commence dead reckoning; 2. The distance due east or due west made by a boat on its course

depth (of hull)

Measurement inside the hull from the underside of the deck to the top of the keel

derelict

An abandoned ship

deviation

Compass error produced by magnetic disturbances aboard or near a ship.

dew point

The point at which a give amount of air becomes saturated with moisture, condensation forms, and fog begins

dinghy, dink, or tender

1. A small open boat equipped with either oars or an outboard motor, occasionally rigged with sails; 2. A small boat used for transportation to shore from a larger vessel.

dip

To salute or signal by means of hoisting and then lowering a flag or pennant

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displacement tonnage

The actual weight, in tons of 2240 pounds, which the vessel displaces when floating at any given draft (such as "light" or "loaded")

distress signal

The method by which a crew can draw attention to a boat in distress; common signals include radio transmissions, flares, flags, air horns, and signal lights 

ditty bag

a bag used by sailors to hold gear needed for repairs on sails or rigging.

dividers

Navigational instruments used chiefly to measure distances or coordinates on a chart

dock

A structure bordering the water area in which boats lie; See pier and wharf

dodger

A screen of cloth or other material erected to protect the cockpit from spray and wind

dog

A metal fitting used to close hatches, covers, and other compartments

dog bones

Metal rings suspended from trapeze lines to which crew can attach their harnesses; typically used on catamarans

dog watch

Two-hour periods of duty between 4:00 and 8:00 p.m. (1600 and 2000)

dolphin

A mooring buoy or spar

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dolphin striker

A rigid support bar between the hulls, at the front of the boat, on a catamaran

dorade ventilator

A deck box with a cowl and an internal arrangement that allows air but not water to enter the cabin.

dory

A rowboat with a flat, narrow bottom and high freeboard noted for its seaworthiness

double ender

Any boat that is pointed at both the bow and stern

doubler

A wood or metal plate bolted beneath a mounting surface for reinforcement

doubling

1. Sailing around a point of land; 2. Overlapping parts on two masts 

douse

1. To turn off or put out a light; 2. To take in or lower a sail

downhaul

1. A line or tackle used to pull down on a sail or spar; 2. A control line that adjusts and tensions the luff of a sail

down helm

To bring a boat up into the wind

downwind

1. Sailing in the same direction as the wind; 2. To leeward

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down with the sun

A recommended way of coiling rope or line, by following the sun's path through the sky

dowsed or doused sail

A sail that is lowered quickly

draft

1. The depth of the water required to float a vessel; 2. Measurement of a boat that extends from the surface of the water, or waterline, to the bottom of the keel; 3. The fullness or belly of a sail

drag

A retarding force caused by friction between the hull and the water that slows boat speed

draw

1. Sails draw when they fill with wind and provide power to drive a vessel through the water; 2. General term that means the same as draft as in "What does she draw?" (how deep is her draft)

drift

1. The leeway of a boat; 2. The natural direction of movement of a boat caused by wind or current, when the boat is not under power; 3. The speed a boat is pushed sideways while under power; 4. The speed of current in knots; 5. To move along with the tide or current

drift lead

A lead weight on a line dropped from an anchored vessel to indicate if she is starting to drag anchor

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drive

To carry all canvas possible in heavy weather

drogue

See sea anchor

drop

The depth of a sail measured from head to amidships

dry dock

A structure that can be shut off from surrounding water and pumped out in order to make repairs on a vessel's bottom

dry sailing

To keep a boat out of the water when not in use