Seaworthiness of Resonance-Free SWATH as an oceangoing fast ship

Abstract

A "Resonance-Free SWATH (RFS)" as the oceangoing large fast ship has the negative restoring moments, which leads to resonance-free in the motion responses, because of the extraordinary small water plane area. The RFS is designed to cross 4,800 nautical miles of Pacific Ocean in 5 days punctually at a high speed of 40 knots, with the good seaworthiness such as no speed reduction or absolutely no slamming even in the rough sea. To verify the seaworthiness of the RFS, experiments in model basin and theoretical predictions are carried out to examine the lowest limit of motion responses in waves. The results in regular and irregular head waves are compared with those of various hull forms, such as mono-hull, ordinary SWATH or trimaran. The predominance of the RFS regarding seaworthiness will be pointed out in the conclusion. For example, by using PD control action, heave motion responses of the RFS is reduced to about 1/40 compared with those of mono-hull or trimaran, and pitch motion responses of the RFS become about 1/8.