haven't logged on in a few years. As i'm getting more and more acquainted with manufacturing operations through my job, I was curious how Curtis Husting might have bent the first RC10 tub frame into shape. I'm still a novice when it comes to sheetmetal work, but i'm eager to learn.

I can't quite understand how he managed to bend the middle frame walls without getting a crease in the metal. Shouldn't a bend in the diagonal planes cause a crease? I have sort of an idea how he might have done it, but i think it's too complicated for a hand-made frame.
Would anyone with some more metallurgy/sheetmetal experience be able to give me some insight? I always had this half-idea to try and make my own hand-made RC10.