I believe I first mentioned this on another forum over a year ago but it’s worth mentioning now, again, because I have more confidence in it working well.
The idea is to use a flap on the lower portion(maybe more) of a canting keel fin ONLY when the fin is at an actual angle of 45 degrees or less to the water. At that point the flap would be deployed up creating negative lift and adding to the righting moment of the boat. Such a flap would be particularly usefull on a monohull canting keel boat that also utilised hydrofoils since the speed of the fin through the water would be greater allowing more force to be developed.But I believe it will work to some degree on any canting keel boat near top speed–but the foils allow a ready way to exceed any hull speed limits. Using a flap like this could result in a significant ballast reduction leading to a lighter boat than currently possible with “normal” canting keel boats.Coupling this lighter displacement to a high beam to length ratio hull could result in speeds between a top end “normal” canting keel boat and a multihull.
Another possibility for creating a similar effect, though with less sure and less controllable results is to install the pivot axis of a canting keel with a 2 to 3 degree nose down angle. It would have little to no effect on the foil until the canting angle TO THE WATER decreased substantially. But unlike the Flap this would not be adjustable and might have slightly negative attributes at cant angles between 50 and 60 degrees to the waters surface.
But what is certain, in my opinion, is that the fin carrying the bulb can be put to good use increasing righting moment at low cant angles relative to the water(high boat angle of heel+cant angle)–and probably not just on hydrofoil equipped canting keel boats leading to a lighter boat and faster speeds.
Doug Lord
microsail.com
monofoiler.com
High Technology Sailing/Racing