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Soft formula fin for less than a bazillion dollars?
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mac



Joined: 07 Mar 1999
Posts: 5083

PostPosted: Fri Nov 01, 2013 3:40 pm    Post subject: Reply with quote

There are some interesting videos of a formula board going by. The tip of the fin is bent almost to horizontal. Under load it looks like the center daggerboard of the AC 72's. I don't know that the theoretical analysis has kept up with the practical, but here's my take. I own 4 Kashy's and 2 early F4's, and have sailed a lot of other fins as well.

The most important factor in sailing a formula board competitively, whether racing or training with your buddies, is the ability to sail near top speed as much of the time as possible. Your very top speed is less important than the amount of time you can be very fast. I had a Deboichette (don't remember the spelling) R14, which was very stiff and very fast. When I would get into some wind I could catch top guys, even Mike Zaicek--the fin was dramatically fast with great angle when lit. But if the win dropped by about 3 miles and hour, I'd be out the back of the pack--the fin lost both speed and angle.

More flexible fins (softer) were developed to give a wider range of response and control. They will work really well across a broader range of wind speed. Too flexible a fin will overpower and lift you in both upwind and downwind directions. Neither is fast. Too stiff a fin will be faster--but will not have as much lift when the wind lightens up.

So a softer fin will have a little more power, and should help you plane earlier--but that edge is small compared to how good your pumping technique is, or whether you are lit.

The 70 cm Kashy goes well with my 11.8, and my 11.0 if not very windy. The 66 Kashy goes with my 11 lit, or my 10 across most winds. The 64 Kashy works with the 10 really lit. And the 62 Kashy ( a repotted 67) works with my 9.0 until I don't want to be on a formula board any more.
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zirtaeb



Joined: 03 Jul 2009
Posts: 2363

PostPosted: Fri Nov 01, 2013 3:44 pm    Post subject: Reply with quote

Also, bear in mind, Kashy's and F-4's have a wider chord, so are actually bigger in squ in per length of fin.
Deb's are very narrow, so have less pure squ in of area.
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