SWATH SHIPS - THEIR NUMBERS GROW

The small waterplane twin hull (SWATH), or semi-submerged ship, is a r elatively recent development in ship design. Although patents employin g this concept show up in 1905, 1932, and 1946, it was not until 1972 that the Naval Electronics Laboratory constructed an 89-foot, 217-ton prototype model. The principle of the SWATH ship is that submerged hul ls do not follow surface wave motion, and struts supporting an above w ater platform have a small cross section (waterplane) which results in longer natural periods and reduced buoyancy force changes. Hull fins further dampen motions and provide dynamic stabilization when underway . The result is that SWATH ships in theory and performance demonstrate a remarkably stable environment and platform configuration which is v ery attractive for science and engineering operations at sea. Flexibil ity of SWATH technology size and configuration allow a wide range of a pplications in open ocean and coastal regimes. About half of the thirt y-one existing or planned SWATH ships have been built or started withi n the past five years. It is time for the oceanographic community to t ake a hard look at what SWATH has to offer.