Daggarboard Lift - ?

[quote="jim-doty"][quote]When both boards are down, they canx eachother like the H14 or H16 hulls... but w/one board, maybe could get 'lifted' more....
[/quote]

This is not a true statement. I think you missed the part about "angle of attack."

Both boards see the same angle of attack and therefore create "lift" in the same direction.

Jim[/quote]


I was saying if the boards had one flat side....other curved.
Don't the H16 hulls want to draw nearer to eachother w/speed, so long as the boat is flat? I was thinking it'd be similiar w/two boards, both down, both w/the inboard side curved, outboard sides flat.

It would depend how the boards were shaped, but my bet would be that angle of attack would win out. Most airplanes will fly upside-down given enough angle of attack.

Jim

The purpose of the curved, teardrop shape, is to allow the fluid flow to remain attached to the surface, but the angle of attack is what determines the direction of lift. Fluids don't like to travel around sharp corners due to their viscosity. So when the radius of the curve becomes too small, the fluid will separate from the surface (stall), the lift will drop significantly and the drag will rise significantly. Having a flat surface on the low pressure side of the board is going to create a really sharp corner that the flow has to go around at the leading edge.

So if you were to make daggerboards with one flat (or concave) side to the outside and you sailed with both of them down, I'd guess that there'd be a high likelyhood that the windward board would just stall when heavily loaded thus creating a lot of drag.

The problem with sailing with one daggerboard raised on the 18 is that you can only raise the board just so high before a lot of the daggerboard trunk is exposed which also creates drag.

Again, if I were you, I'd look into converting to high-aspect ratio boards rather than assymetrical boards.

sm