Originally Posted by Brasshopper
In any case, the boat ended up with a 20" long hole in the port side, under the waterline. I want to do the repair myself. I plan on making an inner support out of something, maybe wax paper covered Formica or wax paper covered styrofoam or even foam in a can. Then I plan on building up alternating pattern and random cloth, pushing it into thick epoxy. Finally, I will cover it in epoxy filler and then gelcoat.
I have not done epoxy since I was 13 or 14...
The best advice here so far is get a pro to do, do it from the outside, forget epoxy and forget waxes , tapes etc.
So don't do it as there are so many little things you cant read from the books
, little things that make the difference and then the big thing in knowledge that someone who has laminated over 10 or say 1000 tons of polyester resin has acquired not in any book
But since i have a feeling you going to do it yourself anyways and I am stuck, yeah its snowing outside, and have a few beers to kill before i turn in... and am not going to proof read this for spelling
From the images
its seems there is a inner liner behind the hole.
Your own initial thought is pretty good but i would modify the approach a bit.
As it is right at the chine one could assume the bottom is also somewhat damaged.
My suggestion is to cut out a rectangle along the bottom about a 1 inch above the bottom of the hull to leave a small ledge upwards, the hole say 30" long 6" high but that depends how large the damage is so approx values.
This gives you axes to the bottom of the hull from the outside.
Strengthen that with appropriate non woven polyester laminate, (clean sand an all that) bring it up the side where you left the ledge and dont worry how damaged the material of the ledge is at this time.
You have also cleaned the insides of the sides before you comers on above lamination, from outside the best you can, this is not super critical but if you get it done perfect all the better, some 36 grit sand paper is good as you cant really get any tool in there.
Next on a flat surface like the Formica you were going to use for backing, laminate a baking, 5 x 450g/m2 should be plenty, make it 10" longer and 5" higher than the hole, drill 2 holes into it, slightly larger than a one component spray insulation polyurethane
nozzle is so you can also fit some thin wire through it while the nozzle is in, trim it so you can later slide it inside the hull with ease or re design it to a two part backing, one peace is is better but not always possible, the main thing is you can get it place with ease.
Next fair "feather" the sides around the hole the best you can 6" minimum id go a whole 1 foot but the sides are pretty thin so something in between.
The next part is a bit tricky, i would laminate strips of wet fiberglass on to the on to the backing and on to the insides of the sides of the hull and the strengthened ledge you left and built up but there is a big possibility to mess up here, the other way is to try to stick wet laminates inside of a hull and on the backing while the baking plate is inside the hull but that might end up even a bigger mess, so first option is maybe better, just plan it so it slides in nice and you can hold it by the wires and remember this part is not really critical but will help to spread the load so if done well all the better. Personally i would not be satisfied if it was not done perfect. Do a few dry runs screw on a handle to hold on to it once you know where the handle wont interfere with the fitting of it in place.
One it is place with the wet fiberglass screw the sides with a few self taping screws (another possibility to screw it up ) or tension it out with wires from the whole or using the handle, you'l figure it out, might even spray some window foam insulation
in at this time if you not sure what you doing, one can should do it with the inner liner so close but even 4 cans, just the cheap
stuff that deteriorates in sun light and will absorb some moisture after time, might make the difference between sinking if you botch the repair. I would not spray in any but just saying.
After all is dry and nothing has bulged, it should not but make sure it can not bulge out one bit or its fed up, do the actual repair (again only non woven and only polyester) from the outside against this structural backing plate and the strengthened chine line flange against future pounding and stuff so do it good.
Anyways I am out of beer
and saying I would not repair it quite like that, almost but not quite if was to keep it for myself (as would most likely just scrap it depending on circumstances) but that is the most simple method for a inexperienced do it your self that should hold even if you mess up a bit, finish of with some polyester putty, and polyester paint
, slap on some anti fouling
and its there.
Edit: LOL just red it, doubt anyone will understand that text.