Fin design

Looking for feedback on whether or not this has been tried

Take it over to General Discussion. You’ll get a response. Yes had been tried before. Topic doesn’t belong on this forum tho.

I moved the thread to general discussion. The original poster could have done it, but probably wouldn’t know how. And mcding’s right, it wouldn’t get far in the industry talk folder.

Nice fin, what is the rider feedback?

Yes, its been done before a long time ago and I believe it is mostly favored by windsurfers .

I think it is called a slot fin or something along those lines.

One guy here did ask me to make him two fins. One normal foil and one with the slot similar to what you are showing but the slot is closer to the leading edge of the fin. It has been a while but I believe he did not notice any difference between the two fins. Hopefully that rider can post up and provide more information.


I believe Ike and Yater both experimented with slotted fins way back when in SB. John Eichert was one of the very first back in the early 60’s to start whittling away at fin area by various means. Lowel

Here is a pic of some that I have. There is another in a board I’ve been riding and one with little holes drilled straight in to the leading edge that exit out the side. Another surfboard specific version by Alfred Maldonado features a pivoting trailing portion(pic not mine.) Some of the old longboards in Santa Barbara were really cut out leaving just a fiberglass outline (pic not mine.)

PS - The one I’ve been using is like the one at the far left in the top photo. I can’t tell much (if any) difference between it and a ‘normal’ fin of same size and shape.


As with a slotted airplane wing. the slot is placed near the leading edge of the foil.
To have effect, slot design and placement must be fairly precise.

As Hans says, a fin with proper flex would have similar effect – the equivalent of wing washout. Making a fin with the right flex would likely be much simpler.

Someone did a fin much like the one shown in the first pic, back in the 70s. The slot was thinner and closer to the back edge. It may have been Alfred Maldonado. Jeff Ho also played around with slots and cuts during that time.

Living on the perfect test track i have to say sometimes the weirdest stuff goes the best. I personally havent ridden the fin. My buddy who does says it works awesome in real waves

I saw some in the Los Angeles area that had a slot but more importantly, the trailing flap pivoted and was connected by internal struts to hinged swallow tail panels. The idea was the tail would ‘bend’’ at the hinge and as it did, would activate the pivoting flap so it acted like a flex tail with a steering rudder.
It was featured in a magazine article but never caught on. Too many moving parts. That, and the idea that in a sucky wave, the inside swallow tail would ‘flex’ resulting in a spin out right when you wouldn’t want that to happen.
In softer waves, it kind of makes sense though…
PS - did you see the slotted fin on billywillgo’s Brewer gun in another thread?