Re: Engineer don't understand fiberglass repair
It won't be cheaper to pay someone. But it may be easier.
Here's the repair process in pseudo engineer speak.
There are two phases to worry about:
- Structural repair
- Fairing and cosmetic repair
The first one involves making sure the damage didn't affect the structural support of the hull. So make sure no stringers have been damaged by impact or rot, make sure there's not a wide scale delamination of the glass on the hull, take care of any secondary issues caused by the keel holes. Repair whatever is needed. Last step is actually patching the hole from the inside to make it waterproof and strong.
The second one is actually filling the hole and making it smooth. A boat hull has some things in common with an aircraft fuselage or car body. It's a convex surface moving through a fluid. Fluid flow mechanics apply, you want to have a low friction low turbulence surface that directs flow in the correct way. You also want the repair strong enough to handle the pressures placed on it in use so it doesn't fail or deteriorate over time.
Once the hole is smooth and faired so the flow over it is good, last step is making it look good and final protection of gelcoat or paint. As mentioned have some idea how you will do this before you start, it'll affect your choice of materials.
Summary of the repair process: Fix the hole from the inside until it's not letting any water in. Then from the outside, clean the hole and remove any debris and loose fiberglass. Grind out the edges of the hole to width of approx. 10x the thickness of the hull in that area. Feather the ground out area to be thinner as you go outward from the hole, so you remove the most material at the hole and less toward the edges.
Patch the hole using several layers overlapping, with the smallest piece of glass going in first, and the final layer being nearly the full width of the ground out area. Avoid bubbles, allow it to cure, then cover the new glass patch with gelcoat or paint over fairing compound.
I don't think I have that book, but there's bound to be a section on patching a hole in your hull by grinding it out and glassing it over, that's the one you want. For your small holes, no need to clamp a backing plate on the inside first, just clean the hole and fill with layers and maybe a bit of peanut butter (resin putty).
Erik
