A floating winged keel is a great idea. Its about time someone thought of a genuine innovation like this.The advantage of the winged fin generally, is that it improves the effective aspect ratio of the fin upright. The increased aspect ratio causes the lift-curve slope of the fin to increase, and reduces the drag induced for a given amount of lift (sideforce) produced.
A winged fin should have a better lift (sideforce) to drag performance for a given planform area than the same fin without the wingtip.
I am not impressed with wingtips on fins in general. This is because the lift on the wing tip is not significant compared to the lift produced by the planing board. Also the close proximity of the wing to the underside of the board would tend to produce an interference or biplane effect. The wing tip produces drag for not much lifting benefit.
However, the floating wingtip allows for a much bigger wing to be put on the tip, without the drag penalties of a typical fixed lifting wingtip.
This means the performance of the fin can be effectively increased to a useful range not encountered by normal fins.
For a given fin planform area the floating wingtip fin can be given a higher lift curve slope, a higher lift co-efficient and lower drag than non-floating wingtip fins.
A way to make a better fin with the same area is to make the fin span less and fin chord greater with the floating wingtip added. The greater chord increases the chord Reynolds number and this improves the responsiveness of flow over the fin (better stability of flow attachment). The otherwise greater induced drag caused by the stubbier fin should be offset by the floating wingtip.
The floating wingtip needs be self-balancing and steady so it minimises the drag it contributes.
Such a self-balancing wingtip can be practically improved by making the wingtip fixed at a zero-local angle of attack and by making the wing trailing edge flexible or flapped. The wing trailing edge needs to be transversly straight and rigid or the benefits of minimising the induced drag due to fin tip vortices will be progressively lost.
Its a wonder to me why this concept has not caught on with yatch designers.
I’ll leave the implementation aspects of the floating wing tip design to the practical people out there.
Thanks.
Hmmmmm…