Unlocking hydrofoil hydrodynamics with experimental results

Hydrofoil sailing has been able to unlock performance characteristics previously confined to speed records, making them available to multiple racing fora. The America’s Cup is now regularly sailed at 40 knots, Moth sailing dinghies and A-Class catamarans achieve up to 30 knots on standard race courses. The systems employed to achieve these speeds have been refined to such an extent that high speeds are regularly attained. However, there are still large gaps in our understanding of the fundamental hydrodynamic phenomena to enable safe control of these machines and continued increases in performance. For example, arbitrary ventilation pathways have been noticed and yet are not fully explained. This paper provides the means to unlock the methods of quantitatively establishing a pathway for arbitrary ventilation and for measuring the flow regime complexity around such foils. These two methods have been developed over many years by the collaborators mentioned in this paper. The result is a valuable contribution to capability available to the sailing research community. An additional two methods of experimental analysis have been detailed within the paper.