Once the mid front rib was riveted to the skin's top side, we fed the front spar into the skin and cleco'd the end and mid ribs and the skins to the spar. Once everything was aligned, we pop-riveted the bottom skin to the mid front rib, then pop-riveted the mid fore/aft ribs to the front spar.
Bottom skins, mid rib pop rivets
Pop Riveting the mid fore and aft ribs to the front spar
