Didnt work out well , the resin melted away the foam to about the size of half a can of beer.
sorry this is a sup board with a windsurf mast insert that was ripped out when i cocked up on a wave.
Trying to do a home job and the above happened . now ive got a big bloody hole in the board.
Any advice on repair of that depth and size
im not concerned about appearances , just want to get it water tight and hopefully put the mast insert back in
would i just get the epoxy resin and top it up till its level with the existing board
cheers for any help .
Probaly should have just given it to the man but eh this is how you learn

With a cavity that big if you just fill it with epoxy resin or even resin and q-cell mix, the heat generated will further melt the foam. You're better off filling it with some foam, either polyurethane or polystyrene, sanding it flat and then glass over it.

Fill with 2 part expanding...note..expanding foam and glass using epoxy resin.

cheers Lee , i went with your advice . Hopefully all works out.