Anonymous wrote:
Yes, some interesting thoughts there re epoxy/polyester. I have to say that I had some doubts about the polyester-based cladding of the hull, but now I understand that it's a solid outer shell on the hull, I'm pretty impressed with the system! Also, the way Frederik's done it, with the bronze nails giving a thorough mechanical bond to the ply is rock solid!
On the other hand, in a 60 year old FG power boat with 50mm plywood transom, there has been no delamination even though the plywood has been wet. So there is a way of doing things that does work. I have read that the way to do things is to do at least one coat on the plywood with no hardener. Perhaps even thinned a bit for penetration. Of course, I think in the 60s, the resin was used without hardener and the mold was heated to cure the resin. However, there are parts of the boat where it does not seem the FG (frp?) could have been done in the mold, like the rear deck, that are also fg on plywood and these have no delamination either.
I would point out that the stories of delamination I have seen floating around have for the most part, been DIY projects. I would guess that part of the problem has also been too few workers trying to clad too large a surface with rapidly hardening resin that has no way of penetrating the plywood before it is already hard. Contrast this to commercial production where the hardener is added as part of the spray system just in time for it to come out of the nozzle (see the youtube channel "on the hulls" for some explanation of spraying resin on to the mold). Epoxy with slow hardener is probably easier for the DYI project with limited equipment and people, if more expensive but frp, done right, is not out of the question.