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Dacron

Trademarked type of polyester used in many sails.

daggerboard

See centerboard.

dampen

To moderate motion.

Danforth

A brand name for an anchor. Often used to indicate any lightweight anchor.

danger bearing

A bearing or course that marks the limit of safe navigation. To go the wrong side of it is to place the boat at risk.

danger sector

See sector.

danger signal

Five or more quick blasts on a horn or whistle to alert nearby boats to potential danger.

dangerous semicircle, dangerous quadrant

The most risky part of a gale or storm, it is the right front section as the storm advances (the left front section in the Southern Hemisphere).

davit

A small crane on deck, used to hoist a dinghy, anchor, or other object.

daybeacon, beacon, daymark

A stake driven into the bottom at the edge of a channel and displaying a placard (daymark) with identifying numbers and colors. It takes the place of a buoy as an aid to navigation in very shallow water.

daysail

To go sailing for a few hours. A daysailer is a boat without a cabin (though she may have a cuddy), used for short sails and racing.

dayshape

A signal hung during the day to indicate the vessel's type or activity, for example a black ball when the boat is anchored.

dead, square

Exact, direct, complete. An object that is dead ahead is directly ahead. To sail dead (square) before the wind is to have the wind directly on the stern. To power dead (square) into the waves is to go straight into them. A dead muzzler is a strong wind from dead ahead. In a dead calm there is no wind. Dead reckoning (D.R.), see navigate and position.

dead end

To secure an end of a line to a stationary object.

deadhead

A mostly submerged log, sometimes used as a mooring buoy.

dead in the water

Stopped.

deadlight

A port or window that cannot be opened.

deadman's switch

Kill switch.

dead reckoning, D.R.

See navigate and position.

deadrise

The angle of the boat's bottom to the horizontal. A flat bottom has 0 degrees of deadrise. A deep-V powerboat hull has about 25 degrees.

deadwood

The part of a keel that does not contain ballast.

deck

The lid on a boat on which the crew walks and sits. A decked boat (deck boat) has a deck, unlike an open boat. The foredeck is forward of the cockpit in a powerboat, of the mast in a sailboat. A deck beam is a length of wood, fiberglass, or wood supporting the deck. The side decks are on both sides. The afterdeck is near the stern. A deck box is a locker on deck. Deck gear consists of cleats, winches, blocks, and other equipment used on deck. A deck shower is a freshwater shower installed on deck or in the cockpit. A deck-house is a small cabin on deck. Deck shoes have special soles (nonskid soles) that grip a wet, pitching deck. A deck filler is an opening in the deck through which a fuel or water tank is filled. A deck plate is a small removable hatch in the deck. Decksweeper, see low.

deep six

To sink.

deep-V

See V-bottomed.

deep water

Offshore.

delaminate

See fiberglass and laminated.

delivery

A direct passage to get the boat to a location where she will be met by her owner. Compare with cruise.

departure

Leaving port at the beginning of a voyage. The vessel takes her departure when she clears land. At the point of departure her crew notes the location, the time, the course, and the mileage.

depower

To decrease the wind's effect on a sailboat by flattening or reefing a sail, or by changing down to a smaller sail.

depth, water depth

The distance from the water's surface to the water's bottom.

depthsounder, echo sounder, sounder, Fathometer, depthfinder

An electronic device that indicates the depth of water. A recording depthsounder produces a record of depth readings over time.

desalinator

See watermaker.

détente

A notch in a boat's gear shift that, when engaged, keeps the engine in gear.

deviation

Movement of a compass card (measured in degrees west or east) caused by metal or magnetism in the boat. A deviation card displays the amount of deviation at different headings.

diesel

A diesel engine, diesel fuel.

differential

See Global Positioning System.

dinette

An eating area in a boat. A convertible dinette can be made into a berth.

dinghy, dink

A small, light boat. Compare with pram and tender.

directional stability

See stability.

directions

Wind directions indicate the direction of the wind is blowing from, for example a northwester is a wind from the northwest. All other directions indicate direction toward, for example to steer a course of northwest is to head toward the northwest (or into a northwest wind). See wind.

dirty air

Wind affected by another object.

dismasted

Suddenly without a mast.

displacement, disp.

Technically the amount and weight of water that a hull pushes aside, but generally a boat's weight. It is measured in pounds or in cubic feet, determined by dividing the displacement in pounds by 64. Light displacement describes a boat that is relatively lightweight for her length, heavy displacement describes a relatively heavy boat, and moderate displacement is in the middle. The displacement/length ratio (D/L ratio) is a number that indicates a sailboat's displacement relative to her size. The larger the number, the heavier she is. See sail area/displacement ratio.

displacement hull (boat)

An especially heavy, full-ended hull or boat. A semidisplacement hull (semidisplacement boat) is somewhat lighter.

distance off

A boat's distance from a charted object. In the distance-off navigation technique, the boat's position is estimated by gauging the distance off from land or a lighthouse's light. That distance is charted as a circle of position. See position.

distance racing

See ocean race.


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distance run

The distance a boat has covered in a known period of time.

distress signal

A flare or other visual signal indicating an emergency.

ditch bag

See abandon ship.

ditty bag

A small bag used to stow and carry a knife, light line, tools, and other boatswain's gear.

divided rig, split rig

See rig.

dividers

Calipers (two short metal legs joined at a hinge) used to measure distances on a chart.

dock

Technically, the water in which a boat sits when she is tied to a float, pier, or wharf. However, the term usually is used to mean the float, pier, or wharf itself. To dock is to pull in to or alongside a dock. Dockage is the fee charged for docking, which may be supervised by a dockmaster. A docking line (dockline) is a line used to tie a boat to another object. See breast line, springline. A dock cart is a wheelbarrow or wagon used to carry gear down a pier or wharf to the water.

documented

A boat registered with the federal government rather than with a state.

dodger

A spray shield over and around a hatch.

doghouse

A shelter forward of a cockpit or over a hatch.

doldrums

A calm area in the middle of an ocean between the trade winds.

dollop

A small wave.

dolly

A trailer for dinghies, used on launching ramps and in boatyards and not intended to be pulled behind cars.

dolphin

Pilings tied together.

dolphin striker

See bobstay.

Dorade ventilator

See ventilator.

dory

A flat-bottomed, double-ended rowing boat originally used as a fishing boat on the Grand Banks.

double

To do twice. To double a peninsula is to sail around it. To double up a line is to rig a backup line. In a double-bottomed boat, there is a watertight compartment between the bottom and the cockpit sole.

double-ender, double-ended

A boat with a pointed stern. See transom.

doublehanded

With a crew of two.

double-headsail rig, double-head rig, cutter rig

Having two jibs set simultaneously on two stays. The outer sail (the jib) is set on the headstay; the inner one (the staysail, forestaysail) is set on the forestay.

douse

To lower or roll up a sail or awning.

down

See head off.

Down East

The coast of Maine, especially north and east of Mt. Desert Island.

downflood

Water pouring below through a hatch or other opening on deck.

downhaul

A line or tackle that pulls down a sail at its tack or holds down a spinnaker pole (also foreguy).

downwind

Away from the direction from which the wind is blowing. Opposite of upwind.

D.R.

Dead reckoning, dead-reckoning plot. See navigate and position.

draft, dr., draw

1) The boat's extreme depth, from her waterline to her lowest point. A boat has 3 feet of draft or draws 3 feet; alternatively, her draft is 3 feet. 2) The fullness or camber of a sail. See chord.

drag

1) Dragging anchor, see anchor. 2) To drag for something on the water's bottom is to scrape the bottom with a grapnel hook or net. 3) Concerning sails and appendages, drag is resistance to wind or water caused by the object's shape, surface friction, and the process of generating forward force (lift) from air and water flow. Eddies around the leech of a sail or the stern of a boat indicate the presence of drag. Compare with lift and stall.

draw

1) See draft. 2) To design a boat.

dress ship

To display flags from bow to stern and aloft in honor of a holiday or an event. A form of flag etiquette.

drift

1) The current's velocity. Compare with set. 2) To not make any speed by power, sail, or oar but rather be pushed by the waves and current. Drifting conditions are almost nonexistent winds. A drifting match is a race held in drifting conditions. A drifting jib or drifter (also windseeker) is a light, small sail set in very light wind.

drive

1) To increase speed. When a sailboat drives off she heads off and speeds up. To drive over another boat means to go by her on her windward side. To drive (push) a boat hard is to push her to near her and her crew's limits. Driving power is a boat's ability to be pushed hard. 2) Driveshaft, the transmission for a boat engine. She V-drive. 3) Steer. The automotive terms drive and driver have recently come to be used by racing sailors and powerboaters to mean "steer" and "steerer" (helmsman).

drogue

A device used to ride out heavy weather and storms. It is a small parachute or other object towed astern. See storm. Compare with sea anchor.

drop

To lower.

dry

A relative word when used in a boat, it generally means that all the water comes from the sea. A dry nor'easter kicks up plenty of spray but provides no rain.

dry rot

Rot in wood.

dry store, dry sail

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

dry suit

Waterproof one-piece clothing that keeps water out and maintains body heat. Compare with survival suit and wet suit.

dual-purpose boat

A racer-cruiser.

dual wheels

Two steering wheels, one on either side. They allow the steerer to sit far to one side or the other for better visibility forward.

duck

1) To duck another boat or duck astern of her is to steer behind her, passing astern. 2) To duck behind a point of land or breakwater is to go from open water to shelter, where there is protection form wind and waves.

duct

A channel for air leading to a ventilator.

DWL, designed waterline

See length.

dying

Describes a wind that is fading or a sea that is growing flatter.