Fin Designs

Now that the other thread has been locked let’s start afresh.

I looked through the 16 odd pages of discussion and didn’t see anything about this theory. What would happen if you reversed the foil on the fin, ie sharp at the front and thicker at the rear. I know it sounds dangerous in crowds etc but my thoughts are if you have less resistance to water at the leading edge it would make for a very slippery fin.


Sharp front edges cause flow separation at small angles of attach, as the fin area on the low pressure side, just behind the leading edge, gets shadowed by the leading edge.

More rounded rear edges do not allow flow re-attachment. Must drag, not to mention the humming sound (I can’t hum it, but if you sing a few lines I can fake it)

It would be a nightmare.

is it possible…could it be… is it even a remote chance…

I AGREE with Blakstah!

Got some PosiTwist fins from Carribean about 15 years ago, WP BACK of center, but evenly smooth leading and trailing edge. Claim was fast and faster, with no spinout. It was 13" tall.

It was moderately fast, it did not spinout, at least not while flow was attached (therein lies the problem). If you introduced air, it didn’t recover!

And being about equal trailing edge front and back, it didn’t have “bite”, the power of holding in under sideloads.

“Twist”…sure, if a 1/2" thick fin made of carbon fiber over foam can bend at all.