Crack along leadinga, was full of water. Now looks dry. My idea is to fill whole wing with epoxy. Any experience or suggestions?

Looks dry and is dry are very different things. How old is the wing and what brand? It looks like the two halves are separating - a manufacturing issue. My first impression is that this is a warranty issue.

I think a proper repair would be to grind back, get it absolutely dry, rebuild the edge.

What is inside? Some kind of foam? Better not!
In the case it is hollow i would make the crack as wide as it could dry in the sun. After that you can let some epoxy in with a liquid foaming agent. I made this with my selfmade foil mast and it worked perfectly.
shop.hp-textiles.com/shop/en/Fillers-Additive/Additive/Liquid-foaming-agent/
Be sure to get it really dry!

Were you windfoiling with a Liquid Force Impulse kite foil? I spoke to someone who did that with a previous generation of LF foil and they bent their fuselage.

Sorry for offtopic its Liquid force Impulse kite foil. Missed kite forum. Dont know what inside, but no foam.

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HIMLING said..
Sorry for offtopic its Liquid force Impulse kite foil. Missed kite forum. Dont know what inside, but no foam.

Kiter? (Just kidding - my kite friends and I share the same enthusiasm of our wings)