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Damping: A ship (boat) has six degrees of freedom, Heaving, Swaying, Surging, Rolling, Pitching and Yawing. The first three are linear motions. Rolling is rotation about a longitudinal axis, pitching is rotation about a transverse axis and yawing is rotation about a vertical axis. It is often necessary to dampen these actions and many devices from stabilizer fins to passive water tanks have been used to this effect.
Davits: Supports under which lifeboats and liferafts are stored and launched.
Deadlight: Steel cover used to protect a porthole in heavy weather. Usually secured with screws and wingnuts.
Deck: Horizontal steel or wooden flooring usually extending from one side of the vessel to the other.
Deck Head: Underside of the deck.
Deck House: Superstructure found on upper decks of a vessel which do not extend the full width of the vessel.
Deck, Main: Principal or strength deck that for structural reasons is an essential part of the ships structure. Usually the deck to which vertical watertight bulkheads terminate.
Deck, Shelter: Deck above the main deck. If this deck is not permanently closed against the weather it is exempt from tonnage dues.
Deck Tween: In a cargo ship any deck between the bottom of the ship and the main deck.
Deep Tanks: Tanks extending from the shell or double bottom up to or beyond the lowest deck. May serve the dual purpose of carrying liquid in bulk or ballast.
Depth Moulded: Vertical distance at Midships from the Keel to the uppermost deck, taken inside the ships plating.
Devils Claw: Claw attached to the fore part of a Windlass which can be fitted over a link in the anchor cable thus enabling the weight of the anchor to be taken off the windlass when the vessel is under way.
Displacement: Weight of water in tones, displaced by a ship. Loaded displacement includes cargo, stores passengers, and crew. Light displacement is the tonnage displaced without these items. The weight of a Warship is always quoted as displacement tonnage.
Docking Bracket: Vertical stiffener fitted between each transverse bulkhead to support the centerline girder of an oil tanker.
Docking Plug: Threaded bolt usually with a socket hex head, fitted to all double bottom yanks and spaces to allow drainage prior to examination in a dry dock.
Dodger: Screen used as a protection from sea spray.
Double Bottom: Space between the outer hull plating and the inner bottom plating of the ship.
Double Skin: A method of construction that utilises an outer and an inner hull. This method of construction is now compulsory for oil and product carriers.
Doubling Plates: Extra plates, bars or stiffeners added to strengthen sections where holes have been cut.
Down to her Marks: When a vessel is fully loaded to her maximum draught for her relevant load line.
Drain Hat: Bilge water collecting pointing a continuous tank top designed to exclude large waste material.
Draught: Distance from the bottom of the ship to the loaded water line. If the waterline is parallel to the keel the vessel is said to be on an even keel or on the keel. If not the vessel is said to be trimmed by either the head or the stern.
Duct Keel: Space formed by twin longitudinal girders in a ships double bottom. Provides longitudinal strength and is usually used to carry longitudinal pipe mains such as ballast and fuel. Big ships can have a small cart on rails that you sit on and pull yourself along to gain access to valves and fittings for inspection and repair. It is one of the scariest places I have ever been. |