Friday, August 10, 2012


                                                   Question. What is the theory?

The hydrodynamic resistance of a foil is greatly reduced when presented transversally to the forward motion of a boat. A high aspect ratio (span-chord) of a lifting surface such as presented on the renderings, can be useful to get on a plane by increasing the lift drag ratio at low cost in terms of resistance.

The lifting surface adds to the righting moment and the foil buoyancy resists the heeling moment.
Placed aft, on the cockpit sole and sliding to the side of the hull like a dagger board, the aileron presents no particular complication.
The shape of the stern is designed to control the angle of attack of the foil to produce the least resistance when slicing through waves, while the weight of the swing keel controls the angle of incidence being forced by the foil action.
PS: I see a serious application with powerboats to control squat down in one hand, and to promote planing on the other.