How much will 1/4 inch birch plywood bend?

[caseydog]

I want to do my roof skin with 1/4 Birch plywood. But I don't know how well it will bend.

This is my profile. The plywood needs to curve around the fron bend, which is an 18-inch radius curve.

The rear curve is a 36-inch wide by 24-inch tall ellipse. My hatch will start about 6-inches back from the beginning of the curve.

Any advice?




CD

[doug hodder]

I think you may have a difficult time with doing it in a baltic birch, if that's what your using, without cutting some kerfs in it. I did my curves in 2 layers of the 1/8", and it worked fine. They mate up perfectly in thickness to the 1/4" that I used on the flat portions. Baltic has more veneers in it and is engineered to stay flat. A regular exterior grade sanded 1 side would probably make the bend though with some encouragement depending on which direction you installed it. Others experience may differ. Doug

[caseydog]

Doug, just to be clear, did you use 1/8 birch, or some other wood?

[TPMcGinty]

The 1/4 inch birch i used could make the bend without a problem, but I picked up some bending birch.

[doug hodder]

I used 1/8" Baltic birch, reason was, It was going to be painted and the Baltic takes on the epoxy much better than the typical ply. It gives a really nice uniform curve and finishes up nicely. It's dimensionally exact so that 2 layers will equal the 1/4" Baltic....not offbeat on the dimensions. If you are going to skin it in aluminum, you could probably get by with the Home Depot stuff...Doug

[caseydog]

I used 1/8" Baltic birch, reason was, It was going to be painted and the Baltic takes on the epoxy much better than the typical ply. It gives a really nice uniform curve and finishes up nicely. It's dimensionally exact so that 2 layers will equal the 1/4" Baltic....not offbeat on the dimensions. If you are going to skin it in aluminum, you could probably get by with the Home Depot stuff...Doug

My main reason for birch is that I am exposing my roof and roof ribs on the inside, and I want to clear coat it and let the wood be what it is.

My exterior is going to be paint. I'm more interested in the inside than the outside.

[doug hodder]

I think if it were me, I'd find the look for the interior ceiling in like an 1/8" material or thereabouts, then overlay it with something that will give you the strength and finish capabilities. Thing is, with the Baltic birch....it doesn't really have a lot of nice grain to it, just my opinion. It will finish up nicely, but just doesn't have the flash that you may be looking for. Usually the nice interior type veneers are laminated to so so substrate. My construction is different that what you are trying to do, so those techniques may not apply. Doug

[bg]

Last I checked (It's been awhile) Ft. Worth Plywood has 1/4" bendable birch.

Probably not what you're after though

[Miriam C.]

I agree with Doug, a nice 1.8" paneling for the inside and a Baltic Birch for the outside. You will need to be sure the Baltic Birch doesn't have footballs. My inside walls are Baltic Birch and they make great pictures but not as good up close.

[caseydog]

I agree that birch does not present the dramatic grain of some other woods, but I like it, and I want to keep my ceiling consistent with my walls, which are birch, and my dimensional support wood, which is poplar.

It certainly won't be furniture grade, but I'm okay with that, since my overall design is for something that is rustic in it's personality.

If I can get birch showing on the inside, I don't care what is on the outside, as long as it takes paint well. Birch takes paint without having to fight with raising grain, too, which gives me more reason to use it inside and out.

I'll check out that flexible birch in Fort Worth, or go with two layers of 1/8 inch birch -- unless someone comes up with a better idea.

CD

[Miriam C.]

The only reason to watch for footballs in the Baltic Birch is if it is on a curve it may pop out and might show under paint. You can get it without footballs you just have to look.

[starleen2]

I would definitely go with the two layers of 1/8 inch ply after trying to bend some 5mm ply. Save yourself some time, grief and struggle and avoid that sickening "pop" when plywood wants to have its own way. Use some titebond II or III to adhere the outer layer after installing the the interior piece.

[b.bodemer]

My front is a 24' radius and the 1/4" was not trouble. But looking at your profile I think that 18" would be difficult.

Barb

[Jst83]

Till it breaks sorry I couldn't help it

[Bucko6]

I just bent 1/4" birch to a 22" radius this last weekend. I was unable to secure 1/8" locally so had to go with the 1/4". I did not find "Baltic birch" but was a nice cabinet grade birch, solid with no voids but only 3 ply would not even come close to the 22" radius. I cut relief’s every 1" about 2/3 of the way through and was just able to bend the radius. The cuts, if done carefully may give your ceiling a neat look?