SummaryA "Resonance-Free SWATH (RFS)" ship is introduced as an example of the oceangoing large fast ship. Because of the extraordinary small water plane area, the restoring moments of the RFS are negative, which leads to resonance-free in the motion responses. 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 towing tank and theoretical calculations based on the strip theory are carried out to examine hydrodynamic forces and motion responses in waves. The results are compared with those of various hull forms, i.e. mono-hull, ordinary SWATH and trimaran. The predominance of the RFS regarding seaworthiness will be pointed out in the conclusion.

SummaryThe paper describes the computational method for motion responses on a Resonance-Free SWATH (RFS), which has extremely small water-plane area and it leads to the feature close to the resonance-free in the motion responses. Theoretical calculations based on the strip theory are carried out and compared with experimental results in regular head waves. The influence of forward speed on lift due to hydrofoils and lower hulls are large and numerically modeled well. Hydrodynamic interaction between twin hulls is well computed through the introduction of a practical manner.

SummaryA "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.