Several comments. He achieves these very sharp angles by laminating and steam bending in combination. First he steam bends 1/8" pieces, then he laminates them together. Notice how basic his steam bending apparatus is, just plastic pipe and a wallpaper steamer. I am fairly sure this is Sitka spruce by the way, favored by airplane makers for its strength, durability and light weight. Think about the stresses on a WWI fighter. I was also interested in his jig, a lot simpler than most I read about. Finally, I had never heard of casein glue. It is made from milk protein and is apparently very strong, durable, resistant to water and has a long open time. Invented in ancient Egypt, it has been used by musical instrument makers and wooden airframe manufacturers.
Here's the video:
Correction: Alan correctly points out in the comments below that the woodworker in the video is using Cascophen glue, not casein as I indicated. As he says, it is a resorcinol formaldehyde adhesive that has apparently come to replace casein for manufacturing wooden airframes. I apologize for the error. The information about casein glue above is still correct.