Going through my notes a while back I came across a tip for mounting inspection covers from Rex Ervin. You install the inspection covers using the backing plate mounted to the inspection cover as a jig to center the cover in the hole in the wing. I tried this and it works pretty well.
I painted the backing plates a few days ago. Today I match drilled the cover to the backing plate at the screw locations with a #40 bit. Then I drilled for the nut plate legs on the backing plate with a #40 bit. Then I machined out a countersink for the rivet at the nut plate legs. Then I matched up the cover and backing plate again and drilled the screw hole opening with a #27 bit. Next I deburred all the holes (there's a lot of holes!). Then I dimpled the screw holes with the pneumatic squeezers. (I'm truly convinced that pneumatic squeezers are 100% a nessisary tool.) Next I attached the nut plates. (These K1100-06 work great)
To position the backing plate to the wing I screwed the cover to the backing plate. Then I looped a couple wires to the corner holes. I put the assembly into position and held it in place by pulling out on the wire loops. I found it helped to put a little peace of tape in the corners of the backing plate to keep the assembly from slipping around while holding it in place. Then I drilled the corner locations and clecoed as I went. Finally all holes in the skin to backing plate were drilled.
One thing worth noting; it was mentioned in the builders manual to use a 1/8" drill bit to open up the screw holes for dimpling and in the QB manual it was said to use a #30 drill bit. In testing I found that both holes were too small and produced cracks when dimpled with a 6-32 screw dimple die. The dimple had to force the hole open. On the drill and tap chart the close fit clearance hole drill size is listed as #27 so that's what I used.
