Wave Reduction by S-Catamaran at Supercritical Speeds

Abstract

The S-catamaran is a catamaran with twin hulls that are slightly curved in an S-form and arranged at a mean yaw angle but mirror symmetric to their common longitudinal centerplane. Theoretical studies (Chen & Sharma 1997, Chen 1997) show that by proper choice of the sectional area curve, separation, curvature, and yaw the waves generated by the component hulls cancel each other at a supercritical design speed, and consequently the wave wake and wave resistance can be substantially reduced. Theoretically, an almost complete elimination of the waves would be conceivable for an S-catamaran. To verify this theory, a model experiment with an S-catamaran was recently carried out in the VBD. The S-catamaran (Chen & Sharma 1997) was designed to have the same length and displacement as the VBD model series M601, which was developed and tested much earlier in the VBD by Heuser (1973). Despite certain deviations from the ideal form for practical reasons, the wave resistance of the new curved-yawed-hull catamaran with and without skeg was numerically found to be less than that of an equivalent straight-unyawed-hull catamaran by 50% and 30%, respectively. Now, the new design, albeit without skeg, has been validated by a model experiment. In comparison with a reference catamaran of the series M601, up to 28% wave-resistance reduction was achieved in the experiment, although not in the originally designed configuration but at a reduced yaw angle found by trial and error.