The Seakeeper analysis was carried out using 41 equally spaced sections to define the hull and 3 parameter Lewis mappings were used to compute the section hydrodynamic properties. In all cases the basic inviscid Salvesen et al. (1970) Strip Theory formulation was used with no additional damping terms; for the high Froude numbers, the analysis was also performed including the Salvesen et al. (1970) transom stern correction.

The computed RAOs (magnitude and phase) are compared with those from the tank tests in regular waves. In all cases, heave has been non-dimensionalised against wave height and pitch against wave slope. The phase lag between the motion and the wave at the centre of gravity is given in degrees.

A comparison of the hullform and the mapped Lewis sections is given in Figure 1. It may be seen that the mappings give a reasonable definition of the actual surface, though there is scope for improvement of the mapping by using more mapping terms.

The motions of the catamaran have been predicted by computing the motions of a single demihull in isolation. For all but the lowest speeds the interaction between the demihulls is small, particularly for the wider spacing of , Separation:Length ratio, S/L = 0.4.