An Experimental Study on Transverse Stability Loss of Planing Craft at High Speed in Calm Water

Abstract

In this study, experimental investigations on the high speed transverse stability loss and the dynamic instability of pitch-excited rolling are carried out for a planing craft, in calm water. Some types of unstable rolling phenomena are observed from free rolling test of a model which is also heave free. The restoring moment, the lift force and the transverse force acting on the model with zero degree of freedom are measured by towing tests, systematically changing towing speed, heel angle, trim angle and draft. As a result, it is found that the unstable phenomena observed by the free rolling tests are due to the influence of the advance speed on the roll restoring moment, and that the roll restoring moment of the craft depends significantly on its trim angle. Using a database, of the measured three-component hydrodynamic forces acting on the model, the nonlinear pitch-excited rolling of the craft is simulated, using the fourth order Runge-Kutta method. The results show that large rolling motion occurs when the period of pitching is half of the natural period of rolling.