so i've seen some conflicting threads on this topic, and i'm looking for any opinions. when glassing the hull, how much does the cloth / goo hide as far as any imperfections? i'm not trying to avoid proper prep, but i also don't want to waste a lot of time and epoxy filling every bump perfectly if the cloth and goo combo is going to hide a bunch of it. , or does the cloth actually make any flaws more obvious?
Bob, Finishing cloth will telegraph medium deep blemishes. I use body glaze to smooth these out. It is poly but drys fast and is real easy to sand. Get it at any body shop supply store. Minor nick and dings the cloth will hide when you apply the weave fill coat of epoxy.
I probably was over cautious but, after noticing the pink bondo type filling that the plywood maker used to fill minor blemishes popped out when I bent to ply even slightly, I removed each of those blemish fills and replaced them with epoxy with micro balloon filler. Micro balloon filler sands easier then wood flour, which would also work. I went with the logic that if epoxy was going to seal down the cloth it would seal in the bondo or micro balloons in my case.
It didn't take long, just minutes actually and sanding it was not a big deal since you sand the surface smooth before laying on the cloth. I also used a coat of clear epoxy before layering on the cloth. It held the cloth nicely in place because I added the cloth while the clear layer was still green.
Something I didn't do but wished I had was adding filler to the epoxy I used to fill the cloth. I think I read something PAR wrote about using fillers with cloth and it made a lot of sense. I just kept layering on thing layers of clear epoxy to fill the weave. It did give me a nice smooth finish eventually with good depth for sanding to prep for painting but I think it took 3 layers of clear to fill.
You want to put the cloth on first and then put a coat of plain epoxy on the cloth, patting it in with a brush and then use a squeegee over the glass. Wash the cured coat with soap and water, fillers can then be used over that, otherwise you may not get the best penetration.
It's a lot easier if the cloth is applied over a smooth and fair surface then the other way around. Even after the 'glass job is done, you'll have some minor smoothing to do, but this is a relatively easy job, if you can just use a light coating of fairing compound, of which 90% is knocked off with the long board. It's so much harder if you have to apply an 1/8" of fairing compound and spend countless hours sanding all the highs and lows. This is because with the raw wood (fairing before 'glassing), you can knock down the high spots and fill the lows, but not so once the cloth is in place. You have to bring all the lows up to the heights of the high spots, because if you get aggressive with sanding the highs, you'll sand right through the nicely applied cloth.