Can wood top-coated w/ polyurethane be bent?

[TheHubbardBus]

Preparing to mount our interior ceiling panels, which are 1/8" birch ply. They'll be bent to conform (approximately) to the original curve of the roof. We'll be applying an oil-based polyurethane top-coat / sealant. My question / problem: Applying the poly with the panels in place (over our heads) seems like a real PITA, and is definitely sub-optimal if I want this to flow out well. Alternatively, I could (preferably) apply it before installing the panels, but will the cured finish be able to flex enough to allow the kind of bending we need?

[Drew Bru]

It should bend just fine. You could always test it on a piece of scrap or the back of one of your panels. We painted ours in place and it wasn't too bad, we used rollers and drop cloths. It might require some futzing around to get the panels in place (we found that nothing ever goes as planned) and that may damage the finish a little...so touch ups are almost inevitable.

[TheHubbardBus]

Thanks so much, Drew. Think I'll take your advice on testing first. It sets me back a day but I'd much rather have the option to paint it flat if I can. Kudos to y'all doing it in place. I'll probably test the same on scrap also & see if it's within my capabilities w/o making a mess of things.

Q: What sheen did you go with (satin, gloss, etc) and are you happy w/ the long-term results?

[DeMac]

Are you steaming or just heating the wood first? Probably
not using ammonia. Neither penetrate varnish. No matter, the bending process will likely mar the surface. Overhead sanding? No. Coating in linseed oil would serve your needs better. Varnish after.

Linseed oil acts as a sealer and also helps hold the heat while you're working the bends. The heat also allows the pores in the wood to open so the oil penatrates deeper. This will speed up your varnish prep work, too.

Polyurethane is 1/3 Boiled Linseed Oil or Tung Oil

[TheHubbardBus]

Thanks for all the info, Mac. Very much appreciated.

As for the wood, it bends to conform to the curve as-is. 3-ply baltic birch, 1/8". Extremely flexible.

I'm no wood expert. Maybe you can tell me the difference? But we searched every big-box store for something in that size that could bend to conform to the required radius, and nothing could - even what appeared to be pretty much exactly what we ended up with... 1/8" 3-ply birch.

We had resigned ourselves to either doing something like you suggest (heat/moisture bending) or going another route when we hit up our local Woodworker's Source store. We thought their 'wiggle wood' selection might be what we needed, but were advised it would be too flimsy for our needs. We were pointed towards their 1/8" baltic birch. I brought along a piece of foam board insulation I had cut to match the most extreme curve on the sides, and it bent around it with zero issues!

[Drew Bru]

Originally Posted by TheHubbardBus

Q: What sheen did you go with (satin, gloss, etc) and are you happy w/ the long-term results?

I think we used a semi-gloss finish, in a white paint. We're happy with how it turned out overall.

[TheHubbardBus]

Thanks again, everyone. Probably a little to early to answer my question without doubt, but at 12+ hours after applying 1 coat of Minwax oil-based polyurethane on a test piece (well past dry-to-touch), I see absolutely no issues whatseover. I can bend this peice of wood in a 9" radius circle and the coating looks fine. Almost feel silly even asking the question now, but I can't say I've ever applied a coating on anything that was subject to this level of bending post-application. I'll update our build thread in the coming week once we get the ceiling up with a definitive report.

[Rucker]

Originally Posted by TheHubbardBus

Thanks again, everyone. Probably a little to early to answer my question without doubt, but at 12+ hours after applying 1 coat of Minwax oil-based polyurethane on a test piece (well past dry-to-touch), I see absolutely no issues whatseover. I can bend this peice of wood in a 9" radius circle and the coating looks fine. Almost feel silly even asking the question now, but I can't say I've ever applied a coating on anything that was subject to this level of bending post-application. I'll update our build thread in the coming week once we get the ceiling up with a definitive report.

I think if you coat it and install within a week or so from 'dry to touch' you can get away with a lot more than if you coat it and let the finish cure.

[TheHubbardBus]

Think you're right, Rucker. That sounds like a good plan.

I was kind of surprised at how it was still off-gassing 12 hours after putting it down. Now I'm happy about it. Love the look though... the warm satin clear just makes the wood 'pop' without adding glare / artificiality.

[Rucker]

Originally Posted by TheHubbardBus

Think you're right, Rucker. That sounds like a good plan.

I was kind of surprised at how it was still off-gassing 12 hours after putting it down. Now I'm happy about it. Love the look though... the warm satin clear just makes the wood 'pop' without adding glare / artificiality.

Most finishes regardless of medium require 6-8 weeks to cure completely, less if dry and warm 24/7, more if cold and wet.

I'm thinkin there's a sweet spot somewhere between a week and a month where the finish will be most resilient to bending without distortion or delamination.

[TheHubbardBus]

Originally Posted by Rucker

I'm thinkin there's a sweet spot somewhere between a week and a month where the finish will be most resilient to bending without distortion or delamination.

Just to be clear, you mean from the time it's well dry to the touch and obviously safe to hande, up to between a week & a month, right? Or do you mean wait a week and then get it up before the months over (understanding that these are loose time estimates). I figure you mean the former, but want to make sure.

[Rucker]

Originally Posted by TheHubbardBus

Just to be clear, you mean from the time it's well dry to the touch and obviously safe to hande, up to between a week & a month, right? Or do you mean wait a week and then get it up before the months over (understanding that these are loose time estimates). I figure you mean the former, but want to make sure.

The former. Handle it as soon as you can but it might be a week or two before you can install without damage, longer when colder.

Be sure to use good ventilation and/or run the heat in the bus for a day or so after installation so you can outgas any remaining volatiles. I just sprayed an acrylic finish over some surfaces and even after a day in the sun, after I moved them to the bus it reeked the next day or so.

[TheHubbardBus]

Thanks again, Rucker! Understood.

And yeah, you don't have to tell me twice regarding the fumes. I've spent half my time on this build in a half-face respirator. Last thing I want to do is rob myself of the experience of my body breaking down by short-cutting the process.

[BigPaul367]

Originally Posted by TheHubbardBus

Preparing to mount our interior ceiling panels, which are 1/8" birch ply. They'll be bent to conform (approximately) to the original curve of the roof. We'll be applying an oil-based polyurethane top-coat / sealant. My question / problem: Applying the poly with the panels in place (over our heads) seems like a real PITA, and is definitely sub-optimal if I want this to flow out well. Alternatively, I could (preferably) apply it before installing the panels, but will the cured finish be able to flex enough to allow the kind of bending we need?

You can steam and bend any piece of wood, all it takes is enough steam and the wood cut thin enough. But, steaming the wood will usually loosen and ruin any finish that pre-exists on the wood. if you are talking about a dry bend, no matter what, bending the wood will change the finish unless it is just stain.

[incubus]

I have taken roof material and pre bent it to arc by placing cinder blocks about eight feet apart and stacking weights(blocks,bricks,tool boxes) on 1/4 inch ply and leaving it. Pad blocks with card board, increase weight over several days. I've done I think 5 or 6 sheets at a time. Dont see why poly cant be applied first,I paint all paneling before installing. Much quicker and easier even with touch up.

[TheHubbardBus]

Thanks everyone.

Well, we'll find out. Sharon worked her butt off this weekend doing pretty much all the staining + 2 coats of clear poly (I had the laborious job of moving panels and removing flying bugs with forceps). I think they turned out amazing (picture is terrible, take my word for it)! Have all the panels sitting in the bus right now w/ a fan blowing over a pan of water... we have moisture-cured polyurethane sealant (backing plates for puck lights) I want to speed the cure of, and this polyurethane coating I want to slow the cure of, so hopefully this helps in both cases. Plan it to put them up tomorrow. I'll try to report back on this thread once fully cured & in place. If not here then our build thread.

I honestly don't see how doing them in place would have been doable unless they were sprayed. It was hard enough to get thin even coats w/o bubbles laying flat in good light.

[Rucker]

Hey, if Van Gough can leave bugs in his paintings we skoolie conversion experts can leave a few bugs in our finishes as well...