Gybing Plates

Yes yes, that is exactly it, why didn't I think of that? Of course fixed fin and it was a round board with quite a rocker and they like nothing more than to head up at the best of times, so and I'd thought of this for formula, time for a gybing fin head..

So lets go back to sitty down things, so what's happening in our five ohs, are you saying the helm is on or about the same angle as the plate and if so that would be constant weather helm?

Now I need to make my switch on switch off system then I could tell immediately, it must of course be so and it should therefore only be used in overpowered planing conditions so you kind of buzz along and instead of making leeway, actually crab to weather.

Anyway, small boat under foiled, should I or shouldn't I? I could do without wasting my time this go round, got lots of other things that need doing.

Edited by iGRF - 27 Jan 16 at 2:54pm

Originally posted by iGRF I don't suppose anyone might have a picture of one, I'm trying to fashion the head of the plate in this Minisprint I bought recently and doing it from memory, ahem thirty five year old memory at that, last time I had one was in 1981 and it wasn't particularly successful in a div 2 board, I'm hoping the additional weight and leverage of this Minisprint with it's canoe seat might be able to overcome the excess lift they generate.

Graeme,
You can't get more power from a gyber, the "power" or side force is, in equilibrium, only ever equivalent to the righting moment that you are applying.
On a dinghy it means taut you can run the hull at 0 deg leeway, which can save up to 10% of additional induced drag. Penalties of loss of buoyancy in case, junctions etc but some compelling wins Esp on under finned boats where you are loading the foils hard and doing in excess of 4 deg leeway. Fwiw we have estimated that cats lime dart 18 etc do about 7 deg leeway sailing upwind normally! A short board I'e skeg only probs similar.
Anyway the reason it didn't work on your board is because, if correctly set up, a boat should have the side force shared to a large extent between board and rudder. In the case of the gyber, the board is yawed say 4 deg from the hull, and the rudder the same to keep balance, so it isn't necssarily seeing any weather helm but it's 4 deg over to maintain equilibrium in yaw.
On the board, you yaw the CB, but can't yaw the skeg, so assuming you are running the skeg with a bit of load innit upwind, the board will want to be heading up the whole time because you have angled the dagger (fwd of Clr) a. Lot and not the skeg (aft of Clr) so unless you chop the rig fwd loads and run all the side force off the CB, so the skeg is not earning it's keep and will be wasted wetted surface, then you will have a board that won't stay in equilibrium

Jim Stop it please, has the world come to an end, you saying grf is talking sense on a techinal matter   
And you agreed with him!!

Love to see the thinking and the effort, but suspect that simply making a decent board will see the greatest gains. Mind, be thankful that you have the option of real shape. The case on my wooden one is so narrow, a Mirror Dinghy board cut down only just fits! No real opportunity for shape there.

Will be trying the one I've made when I collect the boat from its cosy barn.

I did look at this for my Sprint, the main issue I looked at which suggested not doing this, was the slot is only about 5" deep, the pressure on such a short section of centreboard could be catastrophic, you are in effect loading up a reduced surface area, when you shave off material.