The stability of submarines

The purpose of this paper is to place on record the results of calculations made to determine the conditions of stability of submarine vessels in varying circumstances which may occur on service. Accidents have happened to many submarines, and in some instances have been accompanied by loss of life. After investigating possible causes of accident, the author was convinced that one of the chief was the singular variation in stability and buoyancy produced by changes in the draught of water and the “trim” of submarines. He was led, therefore, to undertake the detailed calculations of which the principal results are now stated and illustrated. Either by accident or intention, submarines may reach considerable depths below the surface and be exposed to severe external fluid pressures. Ample structural strength must be provided to meet these pressures and to prevent deformation of the vessels. In order to fulfil this object with moderate weights of structures, submarines are made “cigar-shaped,” with circular or nearly circular cross-sections. The cigar-shape is usually somewhat disguised by light superstructures built above the upper surface of the hull proper, and carrying decks or platforms, which add to the comfort and convenience of the crews when the vessels are floating at the surface—in the “awash” condition—at their lightest draught. In that condition water is excluded from the spaces between the superstructures and the cigar-shaped hulls, and the buoyancy and stability are sensibly increased.