Brief Description: Begin countersinking main spar starboard wing
I began countersinking all the tank attach holes in preparation for attaching the platenuts. The drilling jig fabricated when building the port wing was used to center the countersink cutter. The drilling jig was made from 1/8" aluminum bar stock. I used a #21 drill to ream the screw holes and followed with a #20 countersink cutter. Results were excellent with no elongated holes and no chattering. Per some earlier research, I set the depth by measuring the circumference of the countersunk hole (not to exceed .375") and double checked with an appropriately dimpled test patch (material same thickness as tank skin and dimpled for #8 screw).
By the way, I used my Craftsman cordless drill to do the countersinking on this wing. I think the lower RPM and higher torque works better in this application than the Sioux air drill which was used on the earlier wing. Anyway, the countersinking looks good.
