Wave tank testing and the capsizability of hulls

We study the capsize of model ships excited by the naturally propagating wavefront created by a laboratory wave maker that is suddenly switched on. Such a test is shown to give a good measure of the capsizability of a hull form, and the resulting transient capsize diagram is compared with earlier studies of premature transient capsize under stepped sinusoidal forcing. Some useful design observations are also made, based on the sustainable wave slope of a vessel under tuned, worst-case, beam-sea excitation. Realistic wind loading can give a 30% reduction in the sustainable wave slope, emphasizing that the capsizability of a symmetric, unbiased, vessel is an unreliable guide to its safety at sea.