by GreenLake » Thu Aug 12, 2021 6:26 pm
OK. So you have a cockpit floor that's separate from the hull. I hadn't realized this (or forgotten - it's been a while since you first discussed your boat). We'll have to figure out what this means for your repair. Mainly, the issue is how to fix the floor when the repair isn't supported. We'll find an approach.
Next, your boat seems to have been put together with Bondo (or similar filler). Those fillers don't have any strength, certainly not in form of a sheet. The high-strength filler might have held up a bit better, but I wouldn't use it for anything unsupported extending beyond 1/2" of a supported area (like, it's good to add / restore the edge of a rudder/centerboard because you can build it up with some strength unlike other filler, but it's not something you can use to replace places where you'd want to use laminate.
Then, we've learned that your PO either didn't scuff sand where he applied repairs or didn't solvent wash (read the literature on your epoxy for recommended solvents) to get any traces of wax off the existing substrate. That's the reason for the separation (and yes, it's happened to me recently - luckily nothing structural - and it came off when that area was damaged and needed fixing). Being meticulous in this would be good.
Now, first, you need to get a grinder in there and grind away at the edges of these "channels" to get nice bevels at a slope of 1:12 and also to grind any wood that isn't really solid.
The openings will be too wide to just lay laminate unsupported. You can either (1) use a sheet of something that you can pull tight against the cockpit floor from below and which gets abandoned after the repair (2) laminate a very thin layer of laminate that you attempt slide in and then glue from below - in both cases held up by some wires that you can cut when the repair is done. Or, (3) you can carefully wedge a piece of good styrofoam (the builders kind, that's at least a bit waterproof) so that the new laminate has something to rest on. Again, you'd have to abandon it in place.
With the support in place, you can just lay new laminate to fill the gap. If you have a 1:12 bevel, that should be wide enough to anchor it. As some of the bevel is wood, I suggest you first seal the wood with a coat of epoxy - I happen to have a penetrating epoxy (SystemThree S-1) in my shop, and would use that. But failing that, ordinary unthickened epoxy would do. Make sure it doesn't all get wicked in, before you apply the laminate by adding a bit extra as needed.
Theoretically you could instead lay up a flat piece of laminate on some plastic/wax paper on your work bench, then saw and grind that to be a "plug" with the opposite bevel, and finally glue that in place - but the precision of the fit would make that unlikely to succeed.
If your repair isn't totally smooth (but without really big voids) you can use filler to create a smooth surface, but follow instructions on preparation!
When mixing your epoxy be really precise in the ratio - use a 2:1 if you can, they are easier to mix - and make sure to scrape bottom and sides of the container so there are no pockets of unmixed epoxy. (For the same reason, best to have a bit of epoxy left when you are done, so you don't need to scrape the final bits which are often not as good a mix. And doing so leaves a plug in the container that you can later inspect as to how well it hardened, and if you pull it out, whether there are any places where it didn't get mixed near the container walls - think of it as quality insurance).
The good news is that the actual repair, filling the gap with laminate is really no big deal; as long as the laminate doesn't bridge an open gap because you've supported it from below. If executed well, it will not come apart and be as strong as what it repairs.
PS: I would ordinarily not necessarily bother to restore the wood layer separately from the laminate, but teat it all as a single gap to fill. However, if the depth gets to be over 1/2", that might make it attractive to save on laminate. If the beveling leaves you with nicely beveled wood, you could try to fit a piece of wood with matching bevel and glue that in place with thickened epoxy - it would then serve as support for the laminate. The fit wouldn't have to be perfect, the glue should help fill small gaps up to 1/8", and you'll seal the surface when you laminate over it. Only if you can fashion something to fit with reasonable effort.
PPS: don't hesitate: if you feel like adding another layer of glass over the repair because you're not quite sure it's strong enough, go for it, It's sufficiently far in a corner that one extra layer, nicely sanded and made smooth with a bit of filler, will not look too bad. Extend 2-3" over the edge, but make sure to sand/clean that area down to the old laminate.
~ green ~ lake ~ ~