Casing (submarine)

The casing of a submarine is a light metal structure, usually incorporating a deck, built over the upper surface of the vessel's pressure hull. The

pressure hull A submarine hull has two major components, the ''light hull'' and the ''pressure hull''. The light hull (''casing'' in British usage) of a submarine is the outer non-watertight hull which provides a hydrodynamically efficient shape. The pressure ...

of a submarine is usually cylindrical and possesses a low freeboard when in the water, which makes walking on the hull when on the surface dangerous in high seas or rough weather. The casing provides a flat and therefore safer platform for personnel to walk on. The casing is outside the pressure hull and free-flooding so is usually

perforated A perforation is a small hole in a thin material or web. There is usually more than one perforation in an organized fashion, where all of the holes collectively are called a ''perforation''. The process of creating perforations is called perfor ...

with numerous holes, allowing water to enter and trapped air to escape easily, eliminating any

buoyancy Buoyancy (), or upthrust, is an upward force exerted by a fluid that opposes the weight of a partially or fully immersed object. In a column of fluid, pressure increases with depth as a result of the weight of the overlying fluid. Thus the ...

contributed by the casing and allowing the submarine to submerge with as little delay as possible. Casings have been eliminated since the end of

World War II World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposing ...

as the flow of water through the numerous flood-holes creates noise that may be detected by an enemy using passive

sonar Sonar (sound navigation and ranging or sonic navigation and ranging) is a technique that uses sound propagation (usually underwater, as in submarine navigation) to navigate, measure distances (ranging), communicate with or detect objects on o ...

, as well as causing

hydrodynamic In physics and engineering, fluid dynamics is a subdiscipline of fluid mechanics that describes the flow of fluids— liquids and gases. It has several subdisciplines, including '' aerodynamics'' (the study of air and other gases in motion) a ...

drag. Submarine design {{Submarine-stub