This session started by installing the rivets on all of the nutplates for the right wing spar using my hand squeezer. A few of the nutplates near the tip and root of the spar had to bucked using the air gun because they were too far from the edge to use the hand squeezer. Five more universal-head rivets also had to be installed near the root of the spar with the air gun.
Next, I set the spar on its edge and started countersinking the screw-holes of the nutplates so that the countersunk fuel tank skins could be screwed down into them. I re-used the sample piece of a dimpled #8 screw that I had previously made for the left wing spar to ensure that these holes were not countersunk more deeply than necessary. After that, the inspection cover nutplates also required their screwholes to be countersunk in a similar manner with a different sample skin for a dimpled #6 screw. Then, I countersunk all of the remaining skin and rib holes to also accept a dimpled skin for a -3 flush rivet. Once all of these holes on the bottom of the spar were countersunk, I treated them all with my Alodine pen to prevent future corrosion.
What's next? Flip the spar over and countersink all of the holes on the top side.