Sunday, November 8, 2009

Veal Heel for Multihull Foilers

One of the most recent major contributions to the physics of sailing has come from the little Moth monofoiler: it is called "veal heel" after Rohan Veal who developed it.

Nothing new about heeling a boat to windward except when that boat is flying on hydrofoils. In that case with the boat heeled to weather the Righting Moment(RM) is increased by the amount the boat and crew CG move to weather of the center of lift of the foils.

Not only that but the struts(daggerboard and rudder) supporting the hydrofoils are unloaded and a component of the hydrofoil lift acts to weather improving upwind vmg.

Multifoilers,to date, have either sailed level or heeled like a "normal" sailboat.( except for an unsuccessful experiment in the C class)
I think there may be a better way on a high performance trimaran that would use very small "amas" like the Rave but with a major difference: the new boat would use two foils-like a Moth- for boat speeds up to say, 20 knots. After that the boat would deploy(retractable) very small foils from the vicinity of the windward ama that would generate downforce to increase RM.

I did a rough comparison of two boats each weighing exactly what a Rave does and the wetted surface is less at least up to 30 knots boat speed but whats more drag is less again, at least up to 30 knots. This thing could be designed to be MUCH lighter than a Rave(368lb) and could be substantially faster in 5-20 knots of wind.

But what is really cool is that the new concept foiler would sail with "veal heel" with the attendant advantages upwind.


Comments welcome.....

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