by LMarsh » Sun Feb 28, 2016 11:11 pm
I'm not sure if this applies to birch plywood or just plain old 1/8" but...
As already mentioned the 1/8" plywood is more flexible in one orientation than the other, but it can depend on which way the center ply is running. I've seen it flexible in both directions and some is just plain more flexible than others. I started with some sheets from one lumber yard that was very flexible in the width and it worked great for our 5' wide. I got real lucky with those sheets because then I got some more from a big box store and it busted every time I tried to bend it around the tight rear radius on build 2, I even poured boiling water on it to soften it up. It made no difference though. I finally realized the large center ply was flexible lengthwise in these sheets. They were less flexible overall too, either from the material or maybe a thinner center ply and thicker outside plys. I ended up getting the bendy plywood because I couldn't get anything to bend around the radius. It was pricey and hard to find though. I called every lumber store in the area and only one supplier had it, but all the stores either wouldn't/couldn't get it or were getting it from this single supplier. Since the supplier would only sell wholesale to other businesses I had to buy it from a retail lumber yard but then drive to the supplier and pick it or wait for delivery to the store.
If you have a tight bend as it appears in your photo, definitely look into and consider the bendable plywood. It's so easy to bend you'll be amazed. I believe all the plys run in the same direction so it bends effortlessly. I still have some rolled up into a coil in my garage. You have to specify which way you want it to bend too. The 1/8" bendy plywood is a little floppy so you could even consider something thicker, but once its bent it does stiffen up a bit, just not as much as non bendable 1/8" plywood.