THE EFFECTS OF TRIM BY BOW: A DYNAMICAL SYSTEM APPROACH

The paper briefly reviews previous attempts to account for the adverse effect of bow trim on the safety of a vessel under way before describing a rigorous treatment based on a dynamical system approach. A four-degrees-of-freedom non-linear mathematical model is used, accounting for coupled surge, sway, yaw and roll motions. Treating bow trim as a control parameter, its influence on directional stability is clearly demonstrated through application of the developed procedure to a wide beam riverboat in a variety of operating conditions. The paper then proceeds to present an investigation of the case of the HERALD OF FREE ENTERPRISE, where the capsise mechanism put forward as the most likely is a scenario based on the interplay between directional and transverse stabilities, initiated by bow and trim and aggravated by the ingress of water on the car deck.