Plywood shell/skin. Seal- spar urethane both sides or just one?

drewspuppet

New member
So I’ve got a pretty large trailer build 19’x7.5’ and right now have a bunch of luan sandwiches to assemble and finish.

Due to cost I’m wanting to skin in 1/4” mdo plywood and seal/paint. It’s something that if doesn’t work out I can fix or change down the road.

2x2s, 1.5” foamular and super thin luan.

Would using the urethane on both sides of the 1/4” help prevent warp, etc? Needed?

Thank u for your info
 

rruff

Explorer
I built a camper like this over 20 years back. I'd highly recommend epoxy-fiberglass as your exterior coat over the luan, then paint. You can do most of that before you assemble the panels if you wish.
 

Teardropper

Well-known member
Would using the urethane on both sides of the 1/4” help prevent warp

If I understand, you are asking if the inside of the sheathing should be varnished on the interior side before attaching to the framework.

I'll vote no.

I think sheathing should be attached using TB3 (and screws or crown staples), and any surface treatment will negate the glue's ability to grab the wood. I suggest TB3 instead of TB2 because it has double the open time to work with.

I sure didn't get any warping on my interior 1/8" BB sheathing:

zfranGS.jpg


Tony

P.S. I swear by Minwax oil-based polyurethane.
 

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