Abstract
The SSC, called by the U.S. Navy SWATH, is the one advanced ship which provides excellent seaworthiness and a large deck space, in spite of its relatively small size, and the ability to maintain speed in rough waves. The SSC consists of two submerged lowerhulls, which account for a major part of the displacement, connected to a deck above the water surface by streamlined struts on each side. In this paper, the seakeeping performance of the SSC is presented by describing a theoretical prediction method developed by the authors, model tests results and full scale trial results of the SSC passenger ferry 'SEAGULL' capable of carrying 446 passengers. The motion prediction method is based on the 'New Strip Theory', and takes into proper consideration inherent hydrodynamic forces to the SSC generated by the lowerhulls and fins. The effects of automatically controlled fins are also taken into account in the theory. It is shown in the paper that the theory has been validated by model test results from three different SSC models in various regular waves, showing the favourable effects of fixed fins on motion reduction. Picth, roll motions and vertical accelerations of the SSC as well as measured waves during the extensive full scale tests of the 'SEAGULL' in waves are presented in the form of a spectrum. The results demonstrate the superior seakeeping performance of the SSC and the remarkable reduction of motion due to automatic operation of the fins in seas ranging from beam through following. Correlation of theory with the full scale test results of the 'SEAGULL', shows that the theory developed by the authors is sufficiently useful for motion prediction of the SSC at a preliminary ship design stage.
