Yesterday I started working on the seat backs. They are made up of these skins, reinforced by angles.
Here the are the 4 vertical stiffeners cut to lenght.
At the upper ends, the stiffeners gets rounded like this:
..and at the lower ends they get angled like this:
At the lower ends, a recess is also needed to make room for the hinge.
After measuring out the rivet spacing, drilling and match drilling, the seatbacks are slowly coming together. Still need the horizontal stiffeners and upper hinge parts.