THE DEVELOPMENT OF STABILITY STANDARDS FOR UK SAILING VESSELS

This paper describes the work undertaken by the Wolfson Unit and sponsored by the UK Department of Transport to develop stability criteria appropriate for the safe operation of sailing vessels. An extensive series of model tests and full scale trials have shown many of the conventional assumptions used in sailing vessel stability calculations to be invalid. New methods of assessment have been established which incorporate the results of the research. Whilst the stability criteria themselves appear very simple, the regulations also require presentation of information to aid the master in assessing his safety when under sail. The presentation to be used has been developed as an integral part of the work and is a significant advance in enabling the master to measure his vulnerability to gusts. The experimental work which led to such an improvement in the understanding of sailing vessel dynamics is summarised, and the implications of the findings on traditional calculation methods, particularly in the determination of wind heeling moments, is discussed. The results include new information on wind heeling moment and its variation, the response of a vessel to gusts of various kinds, the effect of inertia, damping and rolling, and the characteristics of gusts themselves. The paper concentrates on the philosophy behind the new requirements and the information for the master, rather than the experimental techniques, and concludes with the implications for the U.K. sail training fleet.