Lots of time was spent carefully measuring the seat bottoms and the hinges that will eventually be riveted to the seat bottoms. First I marked out the dimensions on the seat bottom pans.
I then drew centerlines and required dimensions on all of the hinges. Im careful to label all pieces so that once they are drilled, they end up getting riveted onto the correct place/orientation.
I took a bit of time with drilling the hinges on. The hinge rivet locations come very close to the seat ribs, so I double checked clearances were going to be ok and not interfere with the seat ribs.
Next step I fitted the hinges onto the F-638 seat back brace.
