Experimental study on hydrodynamic performance of SWATH vessels in calm water and in head waves

Abstract An extensive experimental investigation on four SWATH hull forms has been conducted in calm water and in regular waves at University of Naples Federico II. Calm water tests have been analyzed in the range of Froude number F r T from 0.1 to 0.6. For all four SWATH configurations at the speed, corresponding to F r T 0.32, the behaviour in regular waves has been tested. The results of heave, pitch and vertical accelerations are presented in nondimensional form as RAO. For the “most promising” SWATH #4 configuration, a set of stabilizing fins have been designed and an active stabilization system has been developed. The developed SWATH#5 has been tested in calm water on three displacements in the range of F r T from 0.1 to 0.65. The dynamic wetted surface has been identified and the residual resistance coefficient C R as well as R T /Δ are reported. Seakeeping tests have been performed in regular head sea and in head and following irregular sea at F r T = 0.50. The conditions for the occurrence of dynamic longitudinal instabilities have been identified. The results allows to comment the effect of slenderness of struts and SWATH’s immersed bodies on resistance and seakeeping and concerns the applicability of SWATH concept to small craft.