SWATH ship

SWATH ship (Small Waterplane Area Twin Hull), a catamaran ship—though the technology is equally applicable to a trimaran hull—which is shorter than a monohull or conventional catamaran of equal displacement tonnage. The basis of the design is twin underwater torpedo-shaped hulls to which are attached two or more streamlined struts. These pierce the water surface and are connected to a platform deck designed for cargo or passengers by means of what is known as the haunch. It is usual for each submersed hull to have independent machinery. The advantage of this design is that a large proportion of the hull stays below the surface which reduces wave drag and increases stability, giving smaller vessels the steadiness associated with much larger ones. It is also more economical as less power is needed to climb the waves, and it can sustain higher speed in rough weather than a conventional vessel. The theory of SWATH was developed by Dr Thomas G. L. Lang in the late 1960s, and the US Navy commissioned a SWATH ship in the 1970s which has proved successful. The technology is now being employed to build ferries and small cruise ships. SLICE (not an acronym) technology is now being developed, using underwater propulsion pods (see propeller), which allows SWATH ships higher speed through the water without sacrificing stability.