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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:
1. Tests of larger scale boat models than used in
Phase 1.
2. Dynamic tests of drogue models under simulated
storm conditions.
3. Further development of the mathematical
models.
4. Design, construction and testing of a
full-scale series type drogue.
5. Preparation of a proposed design
specification for a full-scale series drogue system and for
modifications to the boat to accommodate the use of a drogue under
survival storm
conditions.
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.
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