MEASURING AND DRILLING THE ACCESS PANELS
The access panels for the light harness came from the manufacturer simply taped shut. In order to make this a more permanent attachment, I chose to add nutplates and #6 screws around the perimeter of the wingtip access panels.
I measured out the perimeter and added a sufficient quantity of screw locations to hold it down. I started by measuring the available gap on the wingtip where the nutplates will be riveted on, and then translated those numbers to the access panel itself. After that, I measured one more time (really don’t want to mess this one up), and drilled out the access panels first. Then, I laid them down on the wingtip to match drill the screw holes. Finally, it was just a matter of widening the screw holes to #28 (or a 9/64th bit works great too – pretty standard in #6 screw bit packs and such).
NUTPLATE ATTACHMENT LOCATIONS
After match drilling the screw locations, I clecoed a nutplate in place and located the rivet holes. From there, a couple of quick shots with a #40 bit made that permanent. The only part I have left unfinished at this point is the corners. There is insufficient room for a standard K1000-06 nutplate, so I will have to go with a single lug plate. I’ll put that on my (seemingly weekly) next order to Aircraft Spruce. Once the locations for the nutplates was finalized, I final drilled the screw holes out to #28. Next step – countersinking.
I’ll admit some trepidation here. I have read numerous accounts of ideal methods for countersinking fiberglass. Key concerns include tearing all of the way through, bit life (fiberglass destroys drill bits), and getting a good surface. I was unable to get good results with a traditional countersink bit and perhaps the only thing I was worse at was the Dremel tapered abrasive bit technique. Just horrible.
Ultimately, I decided to go with traditional aluminum countersink heads spun by hand. Tedious? You bet. But seriously – I have already quite keeping track of time and got truly fantastic results. Method selected. Five quick turns for the screw heads and two or even just three for the rivet heads. Magic.
RIVETING IN THE NUTPLATES
Almost done with the wingtip access panels. I can not emphasize enough the method of attaching nutplates here, and everywhere for that matter. Attach the nutplate with the screw to hold it in place and then add the rivets. This will make sure that any deformations that occur do so with the screw in place. If you attach the nutplate first, adding the screw later may be significantly more difficult.
The final product. Tinnerman washers work great here on the fiberglass surface and look pretty classy too.