Many thanks for taking the time to reply guys but unfortunately its still not going well. 24 hours after applying the gel coat I can pick it off quite easily with the end of a paint scraper. The gelcoat is setting up nice but not bonding too well. This is my process;
1) Mask off area
2) Sand with 120 grit
3) Clean with acetone
4) Mix up gelcoat (proportions are 20ml hardener per 1kg - I'm actually mixing 1.25ml with 62.5g). Gelcoat already has wax in it.
5) Apply gelcoat - I'm doing this quite thickly about 2mm or 3/32 of an inch.
6) Leave for 24 hours
7) Cry because gelcoat can be picked off!
Possible reasons why this isn't working;
1) I'm using waxed paper cups for mixing. Is this contaminating the gelcoat? Will use plastic next time.
2) I opened the inspection holes and found about a pint of seawater in each one. I imagine its been in there for about a year. Could moisture have got through to the outer layers of the hulls and prevented adhesion. Have now got out all the water, the inspection caps are off and the boat is in the garage.
Anyone like to chime in with some thoughts?
Best regards, Andrew