Q: How much can we bend 3/8-inch plywood forms?

A.: Probably to a circle with a 3-foot radius if you bend across the grain, or a circle with an 8-foot radius if you bend parallel to the grain. Even shorter radii can be used if the panels have no knots and have a short grain, or if they are wetted or steamed. Some panels might undergo a localized failure at excessively short radii, however. The American Plywood Association gives the following minimum bending radii:

¡ Bending Radii
Plywood thickness 1/4" 5/16" 3/8" 1/2" 5/8" 3/4"
Across grain 2' 2' 3' 6' 8' 12'
Parallel to grain 5' 6' 8' 12' 16' 20'