I'm building a banquette (or booth) off of my kitchen. Originally, I was going to make an oval booth with the back rest slanted. I planned on constructing a frame out of 3/4" plywood then building up layers of 1/8" bending plywood for the back rest. I've since come across the marvel of bent plywood which comes in a size I could use (in this case I need 2 - quarter circles with a radius of 4'-0") The problem I'm having, is figuring out how to cut it so the slope of the back rest is 7 degrees all the way around. There must be som e geometric formula somewhere that explains something like this, but I can't find it.

Any thoughts?

Joe