Re: Stress cracks throughout the boat
If they are crazing then the fix is not difficult. Crazing is caused when the manufacturer builds up too much gelcoat on the surface. Gelcoat is basically pigmented polyester resin. When polyester resin is not supported with fiberglass cloth it fractures over time and you get crazing.
Stress cracks are caused by movement in the structure itself. Two completely different animals. If you repair the surface and the structure is still flexing then the cracks can return.
Sounds like you have crazing. It is common as fiberglass boats age. The fix for it is to simply grind out the crack to open it up a little. The increased surface area will give the filler a bigger area to bond. Small spider cracks can be taken down with a coarse grit paper and a sander. Use a grinder to make the job quicker if you have a big area to deal with. be careful with the grinder and don?t go any deeper than is necessary.
Since you are painting (rather than going back with gelcoat) you can fill the area with epoxy base filler. Simply fill the area, sand it back flush and smooth, clean it with a good solvent, prime it and paint.
While you are grinding look at the fiberglass laminate after the gelcoat is removed. If you can see cracking in the laminate, it is best to repair it using a little polyester resin and cloth before using the epoxy filler after you grind the cracks out. This will keep the area strong and replace any fiberglass you remove.
Again since you are painting 90% of the crazing you sand out can be simply filled with the filler. If you go to deep, you need to build up with glass first. The filler you use should be no thicker than about 1/16" at the surface.
I like Interlux Watertite filler, but there are many others on the market. Automotive fillers can work, but marine will out-bond and outlast them. Especially below the water line. Evercoat Formula27 is another polyester based filler I like. It is cheaper and easier to sand than watertite and it should be fine above the waterline.
You are going to get tons of opinions on this, but this is the method I use. I have never had a problem with filler popping out or cracking again. Even on the hull under water.
