Thursday February 15, 2007
Wing Spar Countersinking, Nutplates (Wings)
4.5 Hours

Tonight, I began by finishing countersinking the rivet holes for the tank attachment nutplates on the left spar.

Then, I drilled all of the #8 screw holes out to #19 and deburred the insides of all of the holes.

Finally, I riveted all of the tank attach nutplates to both spars.

Next up: countersink the #8 screw holes. Vans instructions say to use a #30 countersink and that the nutplate will guide the pilot well enough to keep the c'sink centered and circular. The countersinking process will eat all of the way through the flange on the spar, so using a #19 countersink would have its own problems. Once the hole became enlarged, the #19 countersink pilot would be able to wander. With this method, the center of the nutplate will hold the #30 pilot more or less centered without damaging its threads.

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