by GreenLake » Wed Aug 10, 2016 12:04 pm
Your photo shows some brown color. That's not what laminate normally looks like, so I wonder whether someone simply used Bondo.
Now, the main reason to reinforce the repair from the inside is to make it easier to do the layup from the outside. This applies if the hole has a significant diameter (so that any laminate would sag badly if not supported) or, as in the case I mentioned, when there's tension in the hull and the sides of the repair do not line up properly.
A well executed repair from the outside should otherwise be strong enough to stand on its own - especially given that the laminate for the DS hull is perhaps a bit stronger than minimally necessary.
I would start by grinding away on the outside until you hit clean laminate (without any signs of damage). Damaged laminate will look white (from broken fibers), good laminate will be transparent, so look dark. You want to leave shallow edges, about 1:12, for a strong repair. You'll want to fill that repair with layers of fiberglass cloth.
There are two techniques: start with a small piece and layer ever larger pieces. Or, do the reverse, start with a piece that covers the whole repair, and then add smaller pieces to fill the center of the depression. The second technique seems counterintuitive, but has the advantage that that first layer of cloth is well suspended. If the actual "hole" in the center of your damaged area (after grinding) is small, the cloth may well "bridge" it without support from the inside.
If you do decide that the unsupported area is too large, then you will have to cut a port and prep the inside. You need to remove loose fiberglass and any paint, but you are not going for a perfect surface. Something like 60-80 grit is totally fine.
Your damage is at the corner of the CB trunk. If you add reinforcement anyway, it might as well serve to strengthen the hull/trunk connection in addition to providing support for the outer repair. 2-3 layers of cloth, tapered, so the inner overlaps the outer by and inch (ideally). I would do the layup in reverse order on a piece of plastic on your workbench, then, still wet, transfer it, with the plastic acting as backing, to the repair.
As you will need to fit it through a 6" hole, perhaps laying up two narrower strips of laminate might work best. You can apply them like an X across your repair. To transfer them, you'd roll them up like tape and then unroll them, with the plastic acting like backing tape.
~ green ~ lake ~ ~