Bending Birch
Posted: Mon Jun 13, 2005 3:56 pmI don’t know if anyone else has used Bending Birch to skin the inside of their roofs. So, I thought I’d provide this mini-product review.
Bending Birch is specially laminated flexible plywood intended to mount on curved surfaces. It comes in 1/8” or ¼” thickness. When purchasing this material you need to specify the direction of bend. Since I’m building a five-foot wide tear, I needed to bend it across the short or 4-foot dimension. Someone building a 4-foot wide would want it to bend across the long or 8-foot dimension. I bought mine from Boulter Plywood in Somerville, Mass., about an hour drive from my home near Worcester. The cost was $35 per 4 x 8-foot sheet of 1/8” thickness. I bought 4 sheets, enough to skin the cabin roof and galley hatch.
I was initially very disappointed with the surface quality of this plywood when I go it home. There was a lot of glue on the surface. It also had scratches and marks on it. I briefly considered taking it back. I really didn’t want to drive back to Somerville. And, I didn’t have another local source for flexible plywood. I decided to make the best of it. I was pleasantly surprised when I sanded it. It cleaned up very nicely with 150 grit sandpaper and my orbital sander. I followed up with 220-grit. The veneer held up that sanding with no problems.
Prior to mounting on my roof spars, I applied 3 coats of Minwax Helmsman Spar Urethane, sanding with 220-grit between coats. The urethane really brought out the beauty of this wood. It looks really, really nice with the urethane on it. I never dreamed that it would come out that nice. This photo doesn’t do justice to it.
I mounted my inside roof skins yesterday. That bendable birch handles like thin piece of cardboard (just a bit stiffer than pizza box laid flat). My son and I had a tough time keeping it down on the surface of the table saw when we cut it. This material is so flexible; we rolled it into a tube and passed it through the door opening in the side wall. We had a little trouble when nailing up the piece that goes against the flat portion of the roof. We didn’t realize it at the time; it. It sagged just a bit on the flat portion of the roof. This caused a small gap to between the first and second piece. The sag will come out when I mount my overhead lights and the galley fan. I’ll hide the gap with a small trim piece. So, it’s not a disaster by any means.
It's utterly amazing how that much that flimsy 1/8" thick plywood stiffened up the trailer body. By the time I get done putting the 3/8" flexible luan on the roof, my roof will be incredibly strong. It's true. We really do overbuild these things.
Bending Birch is pricey and hard to find. However, it finishes very nicely and is much easier to apply to a curved roof than conventional plywood. For someone building a Rimple or other design with tight curves on the roofs, it's the only way to go.
Bending Birch is specially laminated flexible plywood intended to mount on curved surfaces. It comes in 1/8” or ¼” thickness. When purchasing this material you need to specify the direction of bend. Since I’m building a five-foot wide tear, I needed to bend it across the short or 4-foot dimension. Someone building a 4-foot wide would want it to bend across the long or 8-foot dimension. I bought mine from Boulter Plywood in Somerville, Mass., about an hour drive from my home near Worcester. The cost was $35 per 4 x 8-foot sheet of 1/8” thickness. I bought 4 sheets, enough to skin the cabin roof and galley hatch.
I was initially very disappointed with the surface quality of this plywood when I go it home. There was a lot of glue on the surface. It also had scratches and marks on it. I briefly considered taking it back. I really didn’t want to drive back to Somerville. And, I didn’t have another local source for flexible plywood. I decided to make the best of it. I was pleasantly surprised when I sanded it. It cleaned up very nicely with 150 grit sandpaper and my orbital sander. I followed up with 220-grit. The veneer held up that sanding with no problems.
Prior to mounting on my roof spars, I applied 3 coats of Minwax Helmsman Spar Urethane, sanding with 220-grit between coats. The urethane really brought out the beauty of this wood. It looks really, really nice with the urethane on it. I never dreamed that it would come out that nice. This photo doesn’t do justice to it.
I mounted my inside roof skins yesterday. That bendable birch handles like thin piece of cardboard (just a bit stiffer than pizza box laid flat). My son and I had a tough time keeping it down on the surface of the table saw when we cut it. This material is so flexible; we rolled it into a tube and passed it through the door opening in the side wall. We had a little trouble when nailing up the piece that goes against the flat portion of the roof. We didn’t realize it at the time; it. It sagged just a bit on the flat portion of the roof. This caused a small gap to between the first and second piece. The sag will come out when I mount my overhead lights and the galley fan. I’ll hide the gap with a small trim piece. So, it’s not a disaster by any means.
It's utterly amazing how that much that flimsy 1/8" thick plywood stiffened up the trailer body. By the time I get done putting the 3/8" flexible luan on the roof, my roof will be incredibly strong. It's true. We really do overbuild these things.
Bending Birch is pricey and hard to find. However, it finishes very nicely and is much easier to apply to a curved roof than conventional plywood. For someone building a Rimple or other design with tight curves on the roofs, it's the only way to go.
Flexible plywoods can come in real handy sometimes. 
I build custom furniture for a living and have had some experience with it when there was just no other way to duplicate the look without charging the customer an arm and a leg to cooper the front of a curved piece of furniture. Have to admit, I've thought more than once about using it for the curved portions of the enterior of my tear when I start it. 
Still think I'll use a standard material for the top.
