Each of the four skins has three ribs inside, two of those ribs get assembled by cutting up a piece of L-angle metal and bending it to the shape of the rib. Then a slat support piece is placed between the rib and the bracket piece and they are riveted together.
I figured I would do all 8 ribs at once rather than just the two I needed for this skin. So I took all 8 ribs:
and cut up the L-angle into the right size and then made some cuts into it so that it could be bent to the shape of the rib. The rib has pre-drilled holes and the bracket was drilled to match them. Then I placed the support in between the two pieces of metal and drilled all the holes to the right size for an A4 rivet.
After an hour I had 8 of them (note there are 4 left hand ones and 4 right hand ones) ready and waiting to be deburred, primed and then riveted.
