Does anyone know if gybing centerboards have been tried on beachcats? Been studing the Tornado rules, and can't seem to find anything that prohibits their use. The point is to add a few degrees of AoA to the board to the windward direction, thereby increasing lift.

Here is a link to how these work (scroll down the page a ways):
Gybing Boards

Mystere talked of using them at some point; around the year 2001. May have been on thier F20 consortium boat.

Gybing centerboard rely on the boat to change its apparent angle to the wind somewhat downwind. This will ultimately allow a higher angle of attack. This can be accomplished on planing hulls, as once on plane, if the hull does not travel straight in line with the boat it does not cause a significant increase in hull resistance through the water.

I would think that with a long displacement hull, i.e. cat hulls, this would not work to the same effect. The gybing board would increase resistance to water flow.

However, I do not know if anyone has actually tried it or not.

Gordon...The gybing board can be made so that it only gybes in the full down position. If you raise them a bit they center themselves. You could resolve your concern about going downwind simply by raising the board some. It's a good question I've wondered about using them in cats myself.

Quite the contrary. The purpose of the jibing (tacking?) daggerboard is to allow the hull to travel closer to straight ahead, and not have to skew to its true path thru the water to match the boards angle (which it needs to generate lift). Therefore it is particularly applicable to long slender hulls.
The tests that are inconclusive that I know of are with monohulls, what with their bowl shaped hulls, dont really care near as much which way they are crabbing along. They are compromising for lean, lateral stability and low drag at low speed so their sterns sweep up, are wide and, well, bowl shaped. If you imagine a 20' cat hull's path when it is skewed three degrees to its direction through the water, the drag and vortex loss all along the underside length must be horendous.. In effect, imagine daggerboards are only allowing you to sail higher, but not really lowering losses over a boardless boat "pointed in the same direction"
I would further gues that tacking boards would, strangely enough, encourage a deeper slender hull aft, because the vortex loss would be zero. (The boarded hull would not be crabbing, and therefore not need to be less resistant to lateral movement).
Mechanically, I think there is a problem with the tacking boards design because the sideward pressure on the top of the trunk is oposite that at the bottom. i E IT NEEDS TO BE CUT the opposite way at the top (the board would be wedge shaped pointy side forward at the bottom of the daggerboard trunk, and wedge shaped pointy side aft at the top of the trunk. IMHO

Hi Mike,
First let's get our feet on the ground.
The subject is as old as dirt.
Gybing a centerboard does not change the lift. The side force that a centerboard must generate is equal to the side force from the sails. These forces are equal and opposite reguardless of CB gybing angle. A gybing CB might change the path of a hull through the water, the sideslip angle of the hull, but it will not change the sideforce. Let's say we want to allow a CB that is supported for 24 inches in the CB trunk to gybe 3 degrees. How much trunk width are we talking about? The sin of 3 degrees times 24 inches equals 1.1 inches. If the board is 1.0 inches thick itself in the trunk and we want the board to be able to gybe plus and minus 3 degrees, that means the front of the CB trunk at the keel must be 3.2 inches wide. Wow, what a hole, what a wide slot, hard to seal, probably much water pumping going on in the trunk and that is negative horsepower.
Dream On,
Bill

Hi Bill,

I do see your point about the board's lift being a set amount, whether or not it is of gybing design. I now realize you either get the AoA from the boat's angle being ~3 degress higher & crabbing sideways or 3 degrees lower and having the board point 3 higher than the boat.

If you're main concern is with the size of the trunk opening, the Tornado already deals with its wide trunk using slot strips (usually stiff mylar these days). These are very effective at sealing the trunk from water "pumping". The trunk could easily be much wider and wider strips applied.

Mike,
The CB slot gasget on a Tornado is made to accomodate fore and aft movement of the CB not sideways movement like 1 inch to the left of center and 1 inch to the right of center. These sideways movements would tear a normal Tornado CB trunk gasget at the front end plus a special CB trunk would be required, 3 inches wide at the front. As a practical matter, " there is much to be worked out" even to do an experiment.
Bill

I dont think it should even bother us that the trunk is not sealed. We live quite happily with stern hung rudders (for convenience only) Spade rudders are better, but not "enough better".
We cannot justify plowing the 20 foot hull (sin3x20' = 12 1/2"? = increase of frontal area of 200%) thru the water (the sides of the hull are not sealed (submerged) which is why we have all that wave drag) to save a gurgling board.
A board could be made to flex for increasing attack once it sees a loading, However, I dont know how to stop it fluttering.

David,
The gaskets do more than stop a gurgling board. On the Mystere the design is such that without the gaskets the drag would be similar to dragging your hand in the water. Also at speed without the gaskets water is scooped up by the well and thrown up onto the deck. The higher the speed the higher the fountain.