Re****ulation.

Apologies if you've read some of this on another forum but I thought some of you might be doing similar stuff at home. I'd love to see it if you are.

Im a proner and I basically only hit the surf at this stage...no downwinding or jumping off rocks. etc.

I want to surf my foils like a shortboard but it's not that easy. I can blame myself for the most part but I do like to tinker and I've done stuff to my wings and stabs that has made them feel so much better.

I was after more speed, harder more aggressive turns and less of that standing on a ball feeling when banking it over.

Ive cut my Kai stab down to 5 1/2" and have found that the whole setup just goes faster the less span it's dragging around.

Next i added winglets to my Iwa and it is epic. It's noticeably faster and a lot easier to crank into turns. I also glossed the top to help with adhesion of the flow over the top of the wing.

my turns are better already...









Next up I have cut my Kai and will add span to be equal with the Iwa, with a different anhedral setup and probably winglets. It's thinner, higher aspect and it'll have some straight areas along the leading edge. I expect it to be very fast.

Nice work! I especially like the winglets.

Can you explain your thoughts on the glosy top side wing? My understanding is lift is created by the speed of the fluid traveling faster across the top, and slower across the bottom pressure differential = lift... Not sure how friction across the would help.

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Fishdude said..
Nice work! I especially like the winglets.

Can you explain your thoughts on the glosy top side wing? My understanding is lift is created by the speed of the fluid traveling faster across the top, and slower across the bottom pressure differential = lift... Not sure how friction across the would help.

The gloss is a cheap and cheerful attempt at boundary layer control. My thinking is that the finer surface will delay the transition from laminar to turbulent flow. When flow becomes turbulent (usually just behind the point of maximum thickness) it incurs much greater skin friction drag.

The drag of a "clingy" surface is likely to be much less than the drag caused by turbulent flow. I know that guys have said on the forum that this wetsand vs gloss question has been solved on sailboats and sailboards etc, and I tend to agree but they are talking about dragging a planing body through or across water and a foil entails a different set of problem and solutions.

The winglets reduce induced drag, giving a higher l/d ratio....more efficiency.

The frontal cross section has been slightly reduced by clipping the bulbous tips, reducing form drag a little. Form drag seems to be a killer with these foils, and probably the most impressive change in the speed I've felt so far is from clipping inches from the stab as well as thinning. The dream would be to have a thinner mast but I'm on the 29.5" and that has its own benefits.

This project was my attempt to make the foil more efficient overall. It really does feel better, I have gotten it to go a lot faster on the same waves....much less of the handbrake feeling.

Stringerless EPS, one is 5oz innegra/ 4oz e glass deck with 6oz carbon bottom.
The other board is EPS with depron skin, full 6oz carbon deck and 50/50 carbon and glass bottom. This on is very light as I only hotcoated the bottom and rails. The depron is waterproof so I left it naked on the deck.

They are pretty small at 4'4" and 3'11" and the deck concave stiffens them so I don't see a need for stringers.