Canvas set in Weldwood? from 6/03 isue

[TomMcKinney]

I was rviewing old issues last night as I do almost every day and in the June 2003 issue I saw a reference that intriuged me. The article was on a former gillneter that had been converted from sail to power over years and one of the side boxes mention that deck was 2 layers of plywood covered in canvas set in weldwood glue then painted. And it doesn't leak.

My question is how is this done? do you wet out the canvas like fiberglass or do you press it onto a glued surface? Do you water down the glue or make it thick. I have not worked with weldood before--but I have some and this sounds like much less $$$ than 6 oz glass and epoxy for a basic fishing boat that sits on a trailer in fairly dry southern california.

I'm building an OldWharf Dory Co. Lumber yard skiff, so my main goal is to keep the plywood from checking. I don't "need" the strentgh of the glass/epoxy--- boat has a 3/4 ply bottom, 3/8 sides and side decks, frames for extra support.

Any thought if this would work?

[John B]

I know a guy who skinned his boat with an extra thickness of timber and then covered that with calico set in resin. I just covered the bottom of a kids dinghy in cotton and resin. The thing with the fabric is that it sucks up the resin... much more than glass so you do use a lot of product. I'd think it would be the same with the weldwood( The quantity issue I mean... I don't use weldwood and know nothing about it )

[Todd Bradshaw]

If we're talking about cotton canvas and Weldwood Urea-Formaldehyde glue (tan powder, mixed with water to about a pancake-batter consistency) it seems like a strange mix. Weldwood dries to a water-resistant, fairly hard and very brittle state. The only way I can see it stopping fir ply from checking would be to completely encapsulate the ply with enough of it to either prevent moisture absorption or overpower it's effect on the wood (which doesn't seem very likely).

Throwing cotton canvas into the mix may not add any strength at all since cotton canvas stretches like crazy. Other than adding thickness and possibly some abrasion resistance, it's not likely to contribute much to stopping the ply from expanding and contracting. As John said, cotton absorbs lots and lots of resin and it also loves water. It may actually suck some of the water right out of the glue during the application process as well as just require massive amounts of glue to saturate. Tacked down and then dampened with a light spray of water with a few drops of soap in it, you could probably get phenomonal glue absorption into the canvas and stick it down to the plywood, but whether it would wind-up being a durable boating surface is hard to tell.

Given the option of using stuff that we know works very well (epoxy/Dynel or Epoxy/glass, maybe even with some CPES tossed-in for good measure) it seems a bit experimental to me. If it worked, you could save some money, but if it fails three years down the road it may not turn out to be such a bargain. In any case, I'd do some test panels first to devise an application strategy and leave them out in the weather for a while to see what kind of problems might pop up.