Permeability, permeable, and semipermeable may refer to:
Tonnage is a measure of the cargo-carrying capacity of a ship. The term derives from the taxation paid on tuns or casks of wine. In modern maritime usage, "tonnage" specifically refers to a calculation of the volume or cargo volume of a ship. Tonnage should not be confused with displacement, which refers to the actual weight of the vessel. Tonnage is commonly used to assess fees on commercial shipping.
The metacentric height (GM) is a measurement of the initial static stability of a floating body. It is calculated as the distance between the centre of gravity of a ship and its metacentre. A larger metacentric height implies greater initial stability against overturning. The metacentric height also influences the natural period of rolling of a hull, with very large metacentric heights being associated with shorter periods of roll which are uncomfortable for passengers. Hence, a sufficiently, but not excessively, high metacentric height is considered ideal for passenger ships.
The King George V-class battleships were the most modern British battleships in commission during World War II. Five ships of this class were built: HMS King George V (1940), HMS Prince of Wales (1941), HMS Duke of York (1941), HMS Anson (1942) and HMS Howe (1942).
On a ship, the engine room or ER is the propulsion machinery spaces of the vessel. To increase a vessel's safety and chances of surviving damage, the machinery necessary for operations may be segregated into various spaces. The engine room is generally the largest physical compartment of the machinery space. It houses the vessel's prime mover, usually some variations of a heat engine - diesel engine, gas or steam turbine, or some combination of these. On some ships, the machinery space may comprise more than one engine room, such as forward and aft, or port or starboard engine rooms, or may be simply numbered.
The waterline is the line where the hull of a ship meets the surface of the water. Specifically, it is also the name of a special marking, also known as an international load line, Plimsoll line and water line, that indicates the draft of the ship and the legal limit to which a ship may be loaded for specific water types and temperatures in order to safely maintain buoyancy, particularly with regard to the hazard of waves that may arise. Varying water temperatures will affect a ship's draft, because warm water is less dense than cold water, providing less buoyancy. In the same way, fresh water is less dense than salinated or seawater with the same lessening effect upon buoyancy.
A double bottom is a ship hull design and construction method where the bottom of the ship has two complete layers of watertight hull surface: one outer layer forming the normal hull of the ship, and a second inner hull which is somewhat higher in the ship, which forms a redundant barrier to seawater in case the outer hull is damaged and leaks.
A double hull is a ship hull design and construction method where the bottom and sides of the ship have two complete layers of watertight hull surface: one outer layer forming the normal hull of the ship, and a second inner hull which is some distance inboard, typically by a few feet, which forms a redundant barrier to seawater in case the outer hull is damaged and leaks.
The strength of ships is a topic of key interest to naval architects and shipbuilders. Ships which are built too strong are heavy, slow, and cost extra money to build and operate since they weigh more, whilst ships which are built too weakly suffer from minor hull damage and in some extreme cases catastrophic failure and sinking.
A ballast tank is a compartment within a boat, ship or other floating structure that holds water, which is used as ballast to provide stability for a vessel. Using water in a tank provides easier weight adjustment than the stone or iron ballast used in older vessels. It also makes it easy for the crew to reduce a vessel's draft when they enter shallower water, by temporarily pumping out ballast. Airships use ballast tanks for similar advantages.
Belt armor is a layer of heavy metal armor plated onto or within the outer hulls of warships, typically on battleships, battlecruisers and cruisers, and aircraft carriers.
A sea trial is the testing phase of a watercraft. It is also referred to as a "shakedown cruise" by many naval personnel. It is usually the last phase of construction and takes place on open water, and it can last from a few hours to many days.
The Stability conditions of watercraft are the various standard loading configurations to which a ship, boat, or offshore platform may be subjected. They are recognized by classification societies such as Det Norske Veritas, Lloyd's Register and American Bureau of Shipping (ABS). Classification societies follow rules and guidelines laid down by International Convention for the Safety of Life at Sea (SOLAS) conventions, the International Maritime Organization and laws of the country under which the vessel is flagged, such as the Code of Federal Regulations.
Ship stabilityis an area of naval architecture and ship design that deals with how a ship behaves at sea, both in still water and in waves, whether intact or damaged. Stability calculations focus on centers of gravity, centers of buoyancy, the metacenters of vessels, and on how these interact
Builder's Old Measurement is the method used in England from approximately 1650 to 1849 for calculating the cargo capacity of a ship. It is a volumetric measurement of cubic capacity. It estimated the tonnage of a ship based on length and maximum beam. It is expressed in "tons burden", and abbreviated "tons bm".
The displacement or displacement tonnage of a ship is its weight based on the amount of water its hull displaces at varying loads. It is measured indirectly using Archimedes' principle by first calculating the volume of water displaced by the ship then converting that value into weight displaced. Traditionally, various measurement rules have been in use, giving various measures in long tons. Today, metric tonnes are more used.
Indian Register of Shipping (IRS) is an internationally recognized, independent ship classification society, founded in India in 1975. It is a Non-Profit organisation, Public undertaking and a member of the 13 member International Association of Classification Societies (IACS). It was inducted into IACS along with Croatian Register of Shipping (CRS) and Polish Register of Shipping (PRS).
Ship measurements consist of a multitude of terms and definitions specifically related to ships and measuring or defining their characteristics.
An evaporator, distiller or distilling apparatus is a piece of ship's equipment used to produce fresh drinking water from sea water by distillation. As fresh water is bulky, may spoil in storage, and is an essential supply for any long voyage, the ability to produce more in mid-ocean is important for any ship.
A compartment is a portion of the space within a ship defined vertically between decks and horizontally between bulkheads. It is analogous to a room within a building, and may provide watertight subdivision of the ship's hull important in retaining buoyancy if the hull is damaged. Subdivision of a ship's hull into watertight compartments is called compartmentation.
