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

pics required

Not too short is it Rich?

sounds like you've just made yourself a freestyle fin

Here are the pics of the jp fin,

Originally 30cm now 28cm

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....

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. ???

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.

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?

Select to expand quote

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