I have been struggling with thisTH55A horizontal stabilizer for ever. The skin is 2024-T3 .016" and has strengthening ribs as there are no internal ribs to the structure. Forming these ribs has driven me crazy. So, based on a lot of input from my metalsmith friends, I came up with this die design for my Pullmax. This way I can form the bead and close the ends in one operation. Still won't be easy but Ithink it will work.
I am pre-stretcing on the English wheel with a 1/2" radius lower wheel. The attached photos have more detailed explanations. Not out of the woods yet but close.
Here is the die. I can run the bead without the end closing sections in place, then close each end separately.

Obviously, this would close off the left end bead. By rotating the left side down and running to the end of the right side, I swing that side up and close the bead.

This would form the bead itself.

Pre stretching on the wheel. I have a laser set up to aid with start stop points.

These are sample pieces to establish process. I lay out a line to run the edge of the upper wheel.

The small laser beam is the actual, the bright one is reflected off the piece.

Forming the bead I found it necessary to control the material against the fence so the angle keeps the thin material from folding up and messing up the bead.

Close. I have tried a number of pre-stretch processes to see how much is needed to keep any distortion to a minimum. Still would like to massage the close offs and the more samples I did, the better they got.