Model tests and full-scale tests were conducted to investigate the use of drogues to prevent breaking wave capsizing of sailing yachts. A mathematical model was prepared which simulates the motion of a boat and drogue in regular waves and in a breaking wave strike.
For this report the term drogue is used to describe a drag device of any type or size deployed from either the bow or stern, and may be used interchangeably with the term sea anchor.
The tests described herein represent the second phase of the investigation. The first phase results are reported in Reference 1.
The second phase includes:
Prior to this investigation of the use of drogues, comprehensive model tests were conducted in this country and in England to study the effect of sailing yacht design characteristics on breaking wave capsizing vulnerability. This work is reported in References 1-4. Although it was found that' certain design characteristics such as beam/length ratio would adversely affect capsize performance, the effect was relatively small and a slightly larger wave would capsize all the designs. From this work it may reasonably be concluded that design changes which could be incorporated in the sailing yacht fleet in the foreseeable future will not significantly reduce the frequency of capsize. Accordingly this program and a similar program in England was directed toward the use of drogues as a solution which offered the promise of a large improvement in safety and which could readily be applied to the current fleet of sailing yachts.