Naval Arch

AP-Aft Perpendicular FP-Forward Perpendicular LOA- Length overall LBP-Length Between perpendiculars

STABILITY AND HYDROSTATICS

DOUBLE BOTTOM CONSTRUCTION

SINGLE BOTTOM CONSTRUCTION



















After perpendicular: AP, the point where the aftermost section crosses the design water line (DWL). On commercial vessels, generally located on the vertical rudder post. Abaft - Behind Abeam - Area on either side of a ship near the mid section. About - Direction of travel opposite to that being traveled. "Come About" is to change course 180°. Aero-Beacon - A modern type of light presently used in many lighthouses to produce a characteristic. Also used in many airport beacons. Aft - Toward the stern or back area of a vessel. Ahead - In front of or forward of Aid to Navigation - Markers, buoys, lights, fog signals, and electronic systems such as G.P.S. & loran. Used to assist mariners in fixing their positions, aid in marking landfalls, mark dangerous shoals and rocks and to enable ships to keep within a channel. Amidships - Center or middle of a vessel in either length or width. Avast - Stop



















Beam: The maximum breadth of the hull. Bow: The forward end of the ship. Bulbous bow: A prominent appendage attached to the bow in order to reduce resistance and thus reduce required horsepower. Buoyancy force: A ship displaces a certain amount of water and the pressure of the water on the external surface of the underwater body causes this upward force. Buttock lines: Regularly spaced reference planes cutting the ship's hull parallel to the centerline, generally spaced one, two or four feet apart. Beam - Width of a vessel at it's widest point. Binnacle - Pedestal that houses a compass and sometimes a light near the helm (steering wheel) of a ship. Bow - Front of a vessel. Bridge - Area of a ship from which the vessel is steered and navigated. Sometimes referred to as the Pilothouse Bulkhead - Wall or partition dividing a ship into compartments. Also part of the skeleton (ribs) of a ships structure. Bulwark - Part of the hull of a ship that extends above the main deck from bow to stern forming a rail. Bunker - Compartment used for storing fuel.











Coefficients of form: Geometric qualities used to describe the ship more precisely. Presented as ratios or dimensionless coefficients. The most common being the block coefficient, Cb, which is equal to the displacement divided by the length times beam times draft. Davit - A boom or crane type device used to raise and lower objects. Commonly used for lifeboats. Day-Mark - Unique color and/or pattern that identifies an aid Depth: The vertical distance from the baseline, or keel, to the top of the freeboard deck, measured at mid-length of the vessel. Displacement: The weight of the water displaced by the vessel. Salt water equals 64 pounds per cubic foot. Draft: The depth of the vessel below the waterline measured vertically to the lowest part of the hull or other reference point. Forward, aft, and mean draft are commonly found.















Forward perpendicular: FP, the point where the design waterline crosses the forward most section of the hull. Gravity force: Downward force equal to the sum of all the weights on the ship. Acts at the center of gravity, point G on the diagram. Gross tonnage: A measure of the capacity of the ship in which 1 ton is equivalent to 100 cubic feet. Heel: The inclination of the vessel to one side vice roll, which is the angular motion in waves. Keel: The principal fore and aft component of a ship's framing, located along the centerline of the bottom. Length Between Perpendiculars: The length between the forward and aft perpendiculars. Length Overall: The extreme length of a ship measured from the foremost point to the aftermost point. Long ton: Equal to 2,240 pounds. Metacenter: The point where the intersection of a vertical line drawn through the center of buoyancy of a slightly listed vessel intersects with the centerline plane. Metacentric height: The distance between the center of gravity and the metacenter. Planimeter: A tool used to measure the distance around a section in order to develop accurate lines drawings. Port: The left hand side of the ship.



















Inboard - Toward the center of a ship. Also in smaller vessels, an engine mounted inside the vessel driving a propeller shaft through the hull. Keel - The spine of a ship that runs from bow to stern at the lowest point. Lee (Leeward) - Direction the wind is blowing relative to the ship. The side of the ship opposite that of which the wind is coming from is known as the Lee side. Lighthouse - A tower used as an aid to navigation marking a hazard or point of entrance. Usually consisting of a very bright light atop a tower and often a foghorn or siren and radio beacon. Lightship - A vessel used to mark a hazardous area and/or guide shipping traffic, anchored in position with a mast mounted beacon and equipped with a steam whistle for fog warning. List - To lean exceedingly to one side or the other. Log - A book for maintaining complete daily records, Loran - Long range aid to navigation. Operates off of (3) land based radio towers to triangulate location. Mooring - The means of tying a vessel to a pier, dock buoy or other vessel. Navigation - Directing the course of a vessel. Port - A Harbor or Port of Call providing protection for vessels. Also the Left side of a vessel, marked by a red light or day-mark. Porthole - A round window in the side of a vessel that may be opened or tightly closed to seal out water. Quarter - Either side of a ship near the stern. "Quartering Seas" are waves approaching from the front of the ship at an angle. Radio Beacon - A land based, fixed radio beacon that aids navigation by sending a radio signal. Vessels can determine
















Resistance: A force that opposes the forward motion of a ship through the water. Broken down into frictional and residual, where residual includes air and eddy-making resistance, but is primarily wave-making resistance. Section: The intersections with the hull of transverse planes perpendicular to the centerline plane of the ship. Stability: The tendency of a ship to remain upright or the ability to return to normal upright position when heeled by the action of waves, wind, etc. Starboard: The right hand side of the ship. Stern: After end of the ship. Superstructure and deckhouse: The structures built above the hull form, ie. pilothouse and accomodation areas. Table of Offsets: Table of coordinates of a ship's form, ie. height above the baseline and half-breadths at each section. Waterlines: The line of the water's edge when the ship is afloat. Weights and splines: Small weights and plastic pieces used to draw "fair" lines for ship's lines drawings.

















Deck - Floor or horizontal surface extending from one side of a ship to another. Draft - The depth a vessel extends below the waterline. Ebbing - A tide falling or moving from high to low water. Forecastle - The crew's quarters at the bow of a merchant ship or on a sailing vessel, the upper deck located forward of the foremast. Foremast - The forward most mast of a sailing vessel. Forepeak - The area below the forecastle, near the bow. Forward - Toward the front or bow of a ship. Freeboard - Distance from the waterline to the top of the main deck. G.P.S. - Global Positioning System that operates off of at least (3) satellites to triangulate location and elevation. Gunwale - The top of the Bulwark or side rail. Hatch - A cover used to close and seal a hatchway or opening. Hatchway - An opening in the deck through which cargo is transferred or persons enter and exit. Hold - An area below decks used for storage of cargo. Hull - The frame or body of a ship below the main deck.




















Range Lights - Two lights or Day-Marks, located a distance apart, visible from one direction only. When one light is visible directly above the other, you are in the marked channel for safe passage. Reef - A ridge of rocks, sand, or coral at or near the surface of a body of water. Seaworthy - A vessels ability to operated in conditions usually found when out to sea. Ship's Bell - A bell used to signal the time on a ship. Generally constructed of brass. Shipshape - A vessel operating in a clean, organized & proper order. Shoal - An area of rocks or sand at or near the surface of a body of water. SOS - A distress signal. Starboard - The right side of a vessel, marked by a green light or day-mark. Stem - The forward most part of a ship. Stern - The aft part of a ship. Tide - The regular rise and fall of the water level along a seacoast or in an ocean port. Gravitational attraction of the moon is the primary cause of tides. With the moon orbiting the earth every 24 hours and 50 minutes, low and high tides are about 12 hours and 25 minutes apart. Waterline - The point at which the water reaches on a vessel when floating. Windward - The side of a vessel that is nearest the direction the wind is coming from.