To seal or not to seal, that is the question...

[LarryJ]

Ok, I'm at the point of sanding and filling (and sanding some more...), next step is applying canvas.



My question is if I should coat the whole thing with a poly mix before applying the canvas?

I'd like the extra waterproofing penetration the mix would give, but don't want to decrease the hold of the glue holding down the canvas.

Thx

LarryJ

[doug hodder]

Just how well will your canvas accept any sort of adhesive? A tight weave may require it to be laid wet, meaning,coat the trailer with adhesive, then stretch the material over it. Glass cloth is very porous and can be wet out from the top, some canvas may not be able to be laid like that and may need to be laid on a pre-wet out surface. If using a white or yellow glue...I'd mop it on raw wood for better bonding, if epoxy, then you can coat it out, let it cure, scuff it and apply a coat and lay the material while it's still wet, then do the top coating. I'd do some testing to see just how well an adhesive will penetrate your canvas. FWIW Doug

[LarryJ]

I plan on doing a couple test pieces, but I'm pretty sure the canvas will have to be laid wet - it's not very porous.

[48Rob]

I'm with Doug.

Though I'm a fan of sealing wood, there doesn't seem to be any advantage to pre sealing the wood, and then applying sealer (glue) over it.

Roughing up the raw wood will help give it a better grip, and penetration to some degree.

Good plan with the test pieces
I'd do the same, gluing canvas to scrap wood (same type as your trailer) and determining how good the bond is roughed up verses smooth, and how well it adheres to any filler.

Rob

[aggie79]

I'm with Doug.

Though I'm a fan of sealing wood, there doesn't seem to be any advantage to pre sealing the wood, and then applying sealer (glue) over it.

Roughing up the raw wood will help give it a better grip, and penetration to some degree.

Good plan with the test pieces
I'd do the same, gluing canvas to scrap wood (same type as your trailer) and determining how good the bond is roughed up verses smooth, and how well it adheres to any filler.

Rob

+3 on not sealing and using coarse grit sandpaper for mechanical grip.

I have never applied canvas to wood, so keep that in mind. You may find that for covering that large of an area, if you apply glue directly, the porosity of the plywood may cause the glue to flash set. In Texas, in the heat of the summer, I have used a two-step glue process to combat that. The first step is to apply a light coat of glue thinned with water. (I usually cut it 50-50.) Then apply 100% glue over the thinned coat. This way will give you a little more working time.

[LarryJ]

... You may find that for covering that large of an area, if you apply glue directly, the porosity of the plywood may cause the glue to flash set. In Texas, in the heat of the summer, I have used a two-step glue process to combat that. The first step is to apply a light coat of glue thinned with water. (I usually cut it 50-50.) Then apply 100% glue over the thinned coat. This way will give you a little more working time.

I was running into this issue when putting on the second layer of luan on the roof. I solved it by using your described process; put down 9 - 18 inch strip of thinned glue, cover with 100% glue, lay/bend ply, clamp, repeat. I figured I would have do the same with the canvas (minus the clamping). The only difference is that I plan on using a brush, instead of roller, with the 100% glue coat to get a thicker coat.

Thx all. For this process, I'll skip the sealing.

[48Rob]

Larry,

As you're "sealing" and covering the trailer with glue and canvas, the wood will have the potential to be 100% encapsulated...on the outside.

Areas of concern will be cutouts, penetrations, and areas out of sight, such as wheel wells and the bottom of the walls that face the road.

You are probably on top of all this already, but these areas are often overlooked, with the result being ruination of a project someone gave their all to, but simply didn't understand how one pinhole can allow moisture to get behind the best sealed wall or roof in the world.
Attention to the most minor details is the key to success.

Rob

[LarryJ]

Attention to the most minor details is the key to success.
Rob

I've been sealing just about everything, even stuff that will never (again) see the light of day - though your pinhole comment did remind that I should re-do the holes drilled for the running lights before laying the canvas.

Thx all

LarryJ