Join Date: Sep 2003
Location: Auckland New Zealand
Thanked 36 Times in 33 Posts
Rep Power: 13
I reckon the important thing is to understand that on the outside you don't want a bump but you have to ensure that the plug you are forming with the patch cannot be forced into the boat.
So what you need to do is in an area say twice the size of the hole, grind down till you get a sharp edge at the hole. This results in a "well" that you can fill with glass fibre. That will certainly prevent the "plug" from being forced into the boat and will enable you to fair any bump back to the original level of the hull without compromising the strength of the patch. Then grind the inside to create a decent key for the resin and on this side it doesn't really matter if it stands a little proud.
I'll bow to others on what products you should be using. I would add a pigment to colour the repair the same as the original hull colour.