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During the conventional spiral process the manoeuvring characteristics of displacement motor yachts are assessed only on a late stage, if ever assessed. MARIN has developed a tool for a quick numerical assessment of the manoeuvring characteristics that are selected in the early design phase. The effects of variations in rudder area, rudder position, rudder rate of turn and transverse metacentric height are investigated in a structured method. The software behind the scene is the well known software SURSIM, which is used to determine the manoeuvring performance (e.g. the yaw checking and course changing abilities, the turning ability, the directional stability) and to generate valuable trends. The application of a larger rudder or its re-positioning can be therefore included during a hull form optimisation process, assisting the designer and looking already at the resulting manoeuvring performance. The verification with reference criteria and the comparison of the behaviour of the ship under investigation with other ships are additional achievable applications of the manoeuvring tool presented in this paper.