1. Remove any loose material with a Dremel type tool.

2. Fill the gap with Evercoat Forumla 27 (polyester resin paste) and let harden. This stuff goes off pretty fast. Your working time is about 5-7 minutes depending on the amount of catalyst, temperature and humidity. It's hard and ready to sand after about 15 minutes.

3. Sand to the desired contour.

4. Get a Preval disposable aerosol paint applicator, fill with thinned gelcoat/catalyst and spray over the repaired area. You can add wax to the gelcoat mix but I use mold release (PVA) sprayed over the still wet gelcoat. You need to seal the gelcoated surface from air. You need to do this in order for it to cure. Otherwise the surface will not cure and be tacky.

5. Let the whole thing cure until hard (overnight to be safe).

6. Flare the repaired area to match the exisiting material using various grits of wet/dry sandpaper. Repeat steps 4, 5 and 6 if necessary to get the desired thickness/coverage.

7. Rub out with rubbing compound and buff to desired gloss level.

NOTE: Do not use an epoxy based product (i.e. Marine Tex) to fill-in the damaged area. Polyester based gelcoat will not cure if sprayed over epoxy.

This process works very well for polyester resin repairs. Repairing damaged carbon (rudders/daggerboards) is another process (epoxy) and another thread. Good luck.