Triangular monos sailing heeled

[Skippy]

Originally Posted by Rodger Martin Yacht Designs (on their website)

LIFTING / GYBING KEEL
An innovative feature of the Diode 36 is the “gybing” carbon keel– it can be rotated enabling numerous tactical options, such as rotating to windward offering increased upwind pointing ability.
A rotating inner drum contains the keel fin itself ... within the fixed outer drum.

This is exactly what I was talking about.

Originally Posted by Skippy

Would it be feasible to have an adjustable daggerboard with a little tiller on it (lockable) so you have the optimum angle of attack in all conditions?

On a heavy-keel boat of course, the ballast is working when the boat is heeled, but racing skiffs sail heeled in light air without the heavy keel. Hydrodynamically speaking, the question is the same: What do the forces and water flow look like around a regular non-gybing centerboard (and the hull)? It seems like when the triangular hull is floating on its leeward bilge, the centerboard should be pointing leeward and therefore generating lift to leeward???

Unless the hull is contributing significantly to stopping leeway the keel/centreboard will always be at pretty much the same angle of attack... its just a question of how sideways the hull is going through the water [grin]

[Skippy]

Exactly. Maybe I underestimated the hardness of the bilge. In that case, the question is, do these hulls really get that much leeway?

(retyped from memory, accidentally edited the original)

[Skippy]

Well, my guess is these hulls do badly when heeled, making lots of leeway and reducing the lift of the keel. That rotating keel sounds like a good idea.

[pchenrrt]

I'd like to start with a disclaimer - I'm no expert but . . as far as I can reason: If the keels are inefficient due to the hull sliding to leeward it is because the angle of attack is has increased and the keel stalling. Angling the keel to windward would be increasing the angle of attack, which would make the stalling worse, create drag, and slow the hull further. On top of this, angling the keel to windward would increase heeling and spill air from the sails.

Even in a boat that doesn't make a lot of leeway, on a fin keel the lift is created by the flow coming at a slight angle to leeward just as lift is created on an airplane wing. You could angle the keel a bit to windward but then you would need to make the fore edge thicker to be more stall resistant. Overall, I don't know if you would have a net gain on your hands or just have more complexity.