An Investigation into the Self-righting of a Modern Racing Yacht in Waves

Abstract

Ocean sailing yachts can, and do, capsize from time to time, and so the safety of those who sail on them is linked directly to their ability to self-right once capsized. Current regulations used for racing yachts are based on statical concepts, which have been shown to be inappropriate (Renilson et al 2000). In order to gain an understanding of the dynamic factors involved, experiments were conducted on a 1/12.5 scale model of an ocean sailing yacht in waves in the towing tank at the Australian Maritime College. Two different experimental procedures were developed: Testing in a single breaking wave, and testing in steep irregular waves. Four variations of the limit of positive stability were tested, together with one condition which had a different roll radius of gyration, without water on board the model. In addition, two variations of the limit of positive stability were tested to represent the condition with 4000 kg of water on board. From the tests it was possible to conclude that, for the given yacht, if the limit of positive stability is decreased from 119 deg to 104.7 deg the yacht is much less likely to self-right under the action of waves, with or without 4000 kg of water on board.