Tickel,

Whatever you do, don't let the question of having "been tried before" be the test.  You may have to develop several generations before you get it right (a process that most simply don't have the stomach for).  Your board will be very weak and will likely have to be three times as heavy to get similar flex characteristics (all other variables being the same).  I'm not pointing this out to discourage you but only to make sure you take it into consideration.  Extra weight in the centerboard is not a deal killer.

Bram 

i know you said clever people only but im going to say something anyway. how would you store the spare board? it would have to be a centreboard boat i thjink. it might be worth it a class with a heavier weight so you get more righting moment from the board. i dont see why it wldnt work if you got a fairly decent shape but that might need alot of trail and error to sort out.

go for it mate!

The gospel according to Bethwaite reckons the extra lift will never make up for the extra drag.

Water being so stiff, you hardly need any angle of attack to get lift, and sufficent angle of attack comes from the boat sailing along very slightly diagonally when sailing up wind.

Having said which, I sailed with an aged GP14 sailor once who insisted on heeling the boat to leward when sailing up wind, even in a blow, as the curve in the hull gave him extra pointing - and out point everyone else we did!

So maybe if you make the asymetry subtle enough....

as hyrodynamic as possible I think, ie good airfoil section. 

Flat is not necessarily good because you have to transition from leading edge to flat surface to trailing edge again and sudden changes in curve cause the water to accelerate quickly, creating displacement force.

I guess, but don't know for sure, that a really thin board will be good - if you can make it stiff enough not to twist off.

Upon which .... has anyone tried making their own foils?  Out of what?

as the extra mass would be stored in the hull it would'nt make any difference to righting moment.the board in the water would still have the same mass and the same lever so the same righting moment. it would make a difference to the pitching moment of the yacht as their would be more mass lower down in the boat thus lowering the centre of gravity of the boat.but only slightly.

on the subject of building foils you have a multitude of choice depending on the class rules of the boat. personally i would use very high density foam 200kg/m3 plus and uni directional carbon

What about having a 'Bilge boards' arrangement like some scows? Only one foil need be in the water at a time, the other providing some ballast. I'd guess that over the years that Scows have been around, someone must have tried this and probably proved Bethwaites contention  that drag will exceed lift.

Couldn't resist the photo!

My memory of what FB said about his trials with flapped boards is that they found no noticeable difference with a +ve flap but did lose out with a -ve flap.  BUT he then went on to say that they did the wrong experiment.  With the flap the reality is that you could have had a smaller board and hence less wet drag and thus an advantage - albeit a very small advantage.  He didn't go on and do the new experiment though!

So if you did go this route you could and should go for a smaller board as well as a proper assymetric shape.

Don't most boards "flex" beneath the hull anyway?

The prob we always have with Gybing boards (aka accentuating the lift/wing shape) is that they can fall out of gybe, and end up giving you lift the wrong way...!

You could try a movable max chord, which swings side to side where the  system comes out of the top of the blade - like an Int 14 rudderblade.

I like the idea of a flexier blade that you could lock off in either "gybe" as that would surely present a lifted shape to the water, and thus more lift, without the downside of needing to keep pressure on the blade to keep it in gybe.

Mind you - that is awfully tweaky....and that from a 505 sailor...!

Cheers

CW

B*££#R class rules.  Once it's painted white who's to know!!!! 

Though in truth my play boat already conforms to no known class and I'm sick of taking chunks out of the foils with trap hook.  Gel coated foam is just too fragile.  Carbon wrapped foam sounds a good bet.  How about aluminium sheet wrapped round wooden forms?

or better still .... get the class rules changed to something sensible.  When changes that save cost or increase strength but don't change performance are banned, but changes which evidently do change performance, but cost a mint (like buying a new boat every year) are allowed, you have to ask who the rules are written for, the sailors or the manufacturers?

However, rest assured, any boat I race meets the rules pertaining to that race.  But happily there's more to sailing than racing.