The roll motion of a trimaran ship composed of three Wigley hulls in beam waves has been studied on an experimental basis. Two different configurations as regards hull separation were combined with two longitudinal positions of outriggers. A mathematical model, taking into account the roll motion of main hull and the heave motion of the outriggers was compared with the results of the experimental tests. It appears that both effects have to be included to obtain a reliable simulation. The application of a parameter identification technique allowed to estimate the damping and excitation coefficients.
