Spar prep: nutplates
Hours: 3.8 | Posted in Spars & SkeletonBegan work on the wing kit today, by drilling and riveting half of the tank attach nutplates. Completed the upper side of both spars. I made a jig for countersinking the #8 screw holes out of a cut-off piece of 1×1 angle by drilling a nutplate to it, and putting a #30 hole (to match the countersink pilot). Clecoing it to the spar didn’t work, as it blocked the countersink cage, but dropping two rivets in the nutplate attach holes, then fixing the jig in place with a clamp, worked well. This reduced the chattering of the countersink cage, since the pilot doesn’t run out of material as it would if you had only the thickness of the spar flange. It produced decent holes.
The process – ream the rivet holes to #40, deburr the bottom, countersink the top. Attach the jig and countersink the center hole for the screw, and debur the bottom. Spot prime with a Q-tip dipped in primer. When dry, cleco one leg of each nutplate, rivet the opposite side, then remove clecoes and squeeze the second rivet.
There are 62 tank attach screws/nutplates on each spar, plus inspection plate holes on the bottoms. I also discovered (looking ahead) that one of the holes that should be open to bolt on the tie-down fixture is filled with a rivet on the left spar. I assume this will just get drilled out, but that’s a massive rivet.
