Forums > Windsurfing General

reshaping a fin

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Created by steller_3 > 9 months ago, 28 Oct 2009
steller_3
QLD, 123 posts
28 Oct 2009 8:54PM
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I am currently trying to reshape an old stock jp fin that had been damaged. It will only be used occasionally for wave or bump and jump with a 5m combat.

I have worked on it for a while, sanding it back. It does not spin out when jumping or in a straight line but spins out EVERY time when initiating a gybe. No matter how fast or slow.

Why is this happening and what part of the fin is responsible for this?

ps, i know its not my gybing technique

Bertie
NSW, 1351 posts
28 Oct 2009 11:56PM
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pics required

NotWal
QLD, 7430 posts
28 Oct 2009 11:11PM
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Not too short is it Rich?

Haircut
QLD, 6491 posts
28 Oct 2009 11:57PM
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sounds like you've just made yourself a freestyle fin

steller_3
QLD, 123 posts
29 Oct 2009 11:58PM
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Here are the pics of the jp fin,

Originally 30cm now 28cm



j.j.
WA, 86 posts
29 Oct 2009 10:11PM
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Could try thinning it out a bit more at the top - give it some flex which might help with the grip round the corner. Sail more on your front foot at the start of your gybe - sheet in harder, bury the rail....

Krisiz1
WA, 331 posts
29 Oct 2009 10:28PM
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It may be something to do with the tip. I have no idea why but I mostly use Select Weedeaters, 24cm. When brand new you can drive them as hard as you like and they never spin out, but as you grind the bottom flat (it gets shallow sometimes where we sail) they start to let go. ???

mkseven
QLD, 2315 posts
30 Oct 2009 6:54AM
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Rich bring it down to beach next time. The wide point of the foil possibly is uneven-probably a little bit too far forward at tip since it appears you have worked mainly on the front of the fin.

steller_3
QLD, 123 posts
30 Oct 2009 9:51AM
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thanks for the suggestions, I mainly use slalom fins now a days and was wondering what is the point of sweepback on the fin? Less frontal surface area to reduce drag?

NotWal
QLD, 7430 posts
30 Oct 2009 2:11PM
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steller_3 said...

thanks for the suggestions, I mainly use slalom fins now a days and was wondering what is the point of sweepback on the fin? Less frontal surface area to reduce drag?


No I think its just about getting amenable behaviour. It will tend to steer more downwind when it flexes under load. If it sweeps forward it would tend to steer upwind more when loaded. You can imagine what that would be like with the pressure going on and off in bumpy water. I doubt that you could stop it from spinning out.

Why don't you try putting one of your fins in backwards and then report back. A video would be good



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