I have a very thin hull, made from poly-ester resin under GelCoat. The GelCoat has a few minor spider/spliter cracks, most are cosmetic, but 1 may have penetrated into the glass, due to flexing. I'd like to open it up and repair the area behind the GelCoat and strengthen, perhaps add or replace ribs/stringers if needed. I want to add a little weight as possible and will be working through a hole that will need to be covered and cosmeticaly fixed. Question is, what resin options should I be using ? After some research I find there is polyester, polyvinal, and epoxy. I've also found that there are chemical and physical bonds, and at least my first layer will be a physical bond. I've read differing conflicting reports about putting epoxy over poly and vs versa. On the inside it does not have to look perfect, it won't be seen, but I do want a strong bond that will not peel.
Not easy to get photos until I open it up. From the outside there is an area maybe 4" diameter with a crack in the GelCoat shaped king of like a T , that when I flex the hull in the area it opens up to maybe the thickness of a fingernail. My guess is a simple circular peice of glass cloth on the inside covering the area, plus a couple inches extra, to strengthen up the spot. Maybe drill a small hole, 1/8", in the ends of the crack to stop any further spread of the crack, filled with resin when patching. Then GelCoat patch/filler on the outside. Kind of wondering whats better to use polyester or epoxy resin.
If you are going to finish with gel-coat, fix with polyester. If you finish with paint, go with epoxy.
When you do your repair on the inside, I would go more than just a few inches all the way around the repair. Let's say that the crack is 3 inches long, I would go at least 6 inches all the way around to build it up. This way you would be eliminating the flexing going around it and building it up. Your crack should not grow once repair has been made. The flexing is one of the main reasons for the crack to grow, building it up all around won't allow for the flex, thus, the crack should not grow anymore.
The area will not be gelcoated over, it can actually remain rough, as it insode out of sight. After patching the area from the inside, I'll button it up, then grove out the crak in the gelcoat and use gelcoat patch for the finished side. I'm going in tomorrow.
