Started with something like this:
I used a ball mill with a battery drill to grind out the damage, untill I had good clean wood and fiberglass. My neighbor is a body guy and reccommended this filler:
It's a fiberglass filler with strands of glass to reinforce it. You mix hardner with it like bondo, but it is a glass/resin mix, very nasty, wear gloves. I mixed about 2 OZ of the stuff and used a plastic spreader to fill the chunk, then put masking tape on to make sure the bottom didn't sag:
It set up in 15 minutes and I used a sureform to clean the pocket and a sander to clean up the hull part:
Then used regular resin and some UNI glass to put three layers or glass over it. First up and down, then accross, then up and down:
Next is to sand, prime and will paint when I do the bottom. I'm pretty sure no one will ever know it was damaged. Total time was an hour. The glass string filler stuff would be great to fill a mast step or anywhere that you need a strong filler. I plan to use it to fill the several extra hols in my transom, put a piece of clear box tape on the outside, and fill the hole from inside.
