Research On The Motions In Waves And Stability Of The Motions For Swath Ship

Small Water-plane Area Twin Hull ships(SWATH) have two submarine-like lower hulls completely submerged below the water surface. Above water, a SWATH resembles a catamaran. Its haunch areas areconnected to each submerged hull by one or two relatively thin vertical members , or struts. The SWATH ship is a new type ship, which has the excellent combination property, such as low wave making resistance, outstanding sea keeping capacity, ample deck area, etc, and be paid more and more attention by many countries. But the trimming counter moment of SWATH is always reduced, especially in high speed, because of small waterplane area, that makes the ship easily to lose its stability. So, it has most important significance to research the motions and the stabilizing fin of the SWATH ship.At first this paper established the equations of motion for coupled heave and pitch, where hydrodynamic coefficients associated with the motion equations are obtained according as strip theory method that developed by Lee.C.M. And the Routh stability criterion is used to study SWATH stability, from which we derived three performance parameters: the nature period, half-decay time and damping ratio. After that factors such as the size and the location of the fin stabilizers and so on are studied, established the basic theory of design and fixing stabilizing fin of SWATH ship.It hopes that the research will be helpful for the sufficiently understanding in the hydrodynamic performance of SWATH, and useful for the further research in the fin stabilizers.