DICTIONARY OF

Dry Card Compass 122 Dunstos Rudder Brake
Dry Card Compass. Mariner's compass having no liquid in bowl.
Dry Compass. Dry card compass.
Dry Dock. Excavated dock, fitted with watertight entrance, from which water can be
pumped to allow work to be done on underwater portion of a docked ship. Floating dry
docks are usually called 'floating docks'.
Drying Features. Underwater obstructions that appear as tide recedes, but are covered as
tide rises.
Drying Height. Height that a drying feature is above level of chart datum.
D shacke. Shackle having its sides parallel to one another.
Dub. To shape a smooth and even surface on a spar or timber.
Dubhe. Star Ursa Majoris. S.H.A. 195°; Dec. N62°; Mag. 2-0.
Du Boulay Roller Jib. Works on principle of roller blind. Luff of sail is attached to hollow
spar through which passes fore stay. Bottom of spar carries a grooved wheel to which
furling-reefing line is attached. Hauling on this line furls, or reduces area of, sail. Invented
by Captain E. du Boulay.
Duck. Flax fabric that is lighter and finer than canvas. 2. To dip into the sea.
Ducking (a Sail). Tricing, or clearing it, so that helmsman's view is not obstructed.
Duck Lamp. Small oil container with an inclined spout that holds wick. Burns colza oil.
Duct Keel. Twin centre girders with space between them. Increases longitudinal strength
and allows bilge and ballast piping to lie in the space and be easily accessible.
Dumb Barge. Barge with no sail, engine or rudder and unable to move except by towing or,
to a limited degree, by sweeps.
Dumb Compass. Compass card that has no needle, but is adjustable by hand. A pelorus.
Dummy Gantline. Rope rove through a block to act as a reeving line for a gantline.
Dumb Lighter. Lighter with neither means of propulsion nor rudder.
Dummy Piston. Disc on shaft of a reaction turbine. Steam impinges on this disc, so
reducing end thrust.
Dumb Fastening. Short screw fastening that holds a strake until a through fastening is
passed.
Dune. A low sand hill.
Dungiyan. One-masted Arabian sailing vessel.
Dunnage. Any material, permanent or temporary, that is used to ensure good stowage, and
protect cargo during carriage.
Dunstos Rudder Brake. Fitting for preventing sudden snatches on rudder chains during
heavy weather. Thwartship wire, with ends secured on either side of ship, passes around a
sheave on tiller. At normal speed of rudder, the sheave 'rolls' along wire;
with sudden stresses, wire temporarily grips sheave, so absorbing stress that would,
otherwise, come on engine and steering chains.