Fixed lifting foil sailing vehicles are at about the same stage of development as were catamarans about 15 years ago. So far it has been established (experimentally) that fixed foil vehicles do “fly”; that there exists an optimum take off speed corresponding to each given hull configuration; that for a given catamaran configuration with and without foils in true wind speeds in excess of 15 knots; and that the observed improvement is not equal to that predicted.

The present paper concludes on the basis of timed runs that the discrepancy between predicted ideal and observed performance is due to lack of control of vehicle stability and balance in the hard and gusty winds required for top speed. Herein, are developed some simple ideas for improving sailing hydrofoil performance with minimal helmsman control of foil incidence and dihedral. The design and development of two hydrofoil sailboats incorporating these ideas is described and the results of comparative predicted and measured performance of one of them is presented.

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