It's in the starboard sidetank in the back quarter. It had previously been repaired after a trapeze hook stuck it's self through it. It was either the trapeze hook again or the crews foot but I'm not sure. It is now a lot larger and I'm going to have to cut quite a lot out of it.
Its not a big deal there though. Especially as the decks are painted so you don't need to be pretty. (not that Stanley's decks were *ever* pretty!
Get some 3mm exterior grade ply.
Cut the hole back to good wood
Make a patch to go underneath, Should be about an inch bigger than the hole all round (except gunwhale side of course!)
Cut a hole in the middle of this about an inch smaller than the hole
Glue in place, using G cramps to clamp it down - hence the hole in the middle. Don't forget to remove all excess epoxy whilst it's still soft.
Make piece of ply the same size as the hole. Glue/staple in place. The ply will probably end up higher than the deck - sand down flush. If the patch is lower than the deck (unlikley, I'm sure the decks will be 3mm ply) and you want to be really cute then take back the top veneer flush about half an inch bigger all round, add a larger patch to fill that which will be way proud and belt sand that down...
Paint.