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Old 08-30-2005, 04:34 AM
sailingsloofer sailingsloofer is offline
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Join Date: Aug 2005
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Location: Seattle
Winged Canting Keel for Increased Efficiency???

So yes the canting keel, a great design which only needs about half the balast of conventional sailboats and increses uprighting force on the boat which both increase the overall speed.
But what about a canting keel, with a wing on the bulbus balast at the bottom of the keel that would provide a down force (upside down airfoil) and would be able to rotate about the horizontal axis of the balast with some mechanical device in the bulbus balast so the wing would always be horizontal to the surface of the water, and the downforce would always be straight down. So when the keel is canted to windward, the wing would provide additional downforce on the keel, uprighting force on the boat, increased sail area, and would also cut down more balast weight, which would lead to more overall efficiency.
I'm wondering if anybody out there has ever heard of something similar to this? And was maybe wondering if there are any obvious flaws I have overlooked, other than the slight increase in underwater drag, feedback would be appreciated, thanks.
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Old 08-30-2005, 12:16 PM
Doug Lord
 
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Winged Canting keel

The question of wings on canting keels has at least two distinct incarnations:
1)One of the biggest problems when considering the use of a canting keel is finding a way to create the extra lateral resistance needed as the keel cants. Solutions have ranged from daggerboards ahead of or behind the canting keel,twin asymetrical daggerboards and wings on the keel.Wings don't take up any inside room and have the advantage of the canting keel unit being self contained.Some low cant angle canting keels have used a trim tab to enhnce the effectiveness of the keel at cant angles around 25-30° such as Eric Sponberg's Project Amazon and the Cookson 50.
I believe it was Brit Chance who used a wing shaped bulb on the canting keel of Procyon and Julian Bethwaite has recently showed an illustration of a 26 footer using the same basic thing-both relatively high cant angle systems with Bethwaites at 60°. A few years ago Andy Dovel in Australia designed a race boat using fixed high aspect ACC like wings on the bulb for lateral resistance. I've come up with a retractable wing system(kFOIL™) where the wings retract into the bulb when not needed.
2) The other side of wings on a canting keel is to use them for downforce as you suggest. Stephen Ditmore, a contributor here came up with a rotating foil system for a fixed keel that might be adapted to a canting keel for that specific purpose. And Alberto Calderon and the CBTF guys have come up with an idea utilizing a flap similar to a trim tab on a HIGH CANT ANGLE canting keel strut specifically to do what you suggest.
Using foils and flaps on monohulls with canting keels to develop righting moment has the potential of allowing great righting moment with less ballast and possibly allowing canting keel monofoilers as time goes by.
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