Brief Description: Match drill cover plates & install nutplates
I began today's shop session by clamping the two cover plates together with cleco clamps and then drilling the screw holes to #30. Extreme care must be taken to locate the holes so they do not interfere with the angle that ties the sides and inner surface of the gear box together. Once the plates were drilled, I carefully placed them over the access ports and began match drilling them to the gear boxes. Again, placement of the holes is critical on the gear box inner surface (if you get the holes outboard too much you will have trouble attaching the nutplates).
After match drilling to #30, I attached the nutplates and drilled the #40 attach holes all around (a copper cleco was used to hold the nutplate in place while drilling the attach holes). My next step was to enlarge the screw holes to #19, again by match drilling. The final step was to countersink all the nutplate attachment holes and rivet the nutplates into position.
In conclusion, I am happy with the mod and believe the enlarged access port will make future maintenance much easier. Using the same grade and thickness of aluminum for the covers and keeping the screw spacing similar to the riveted structure should avoid any structural issues (this is the consensus on the various builder forums).
I would like to suggest a couple improvements if there are any builders out there that haven't gotten too far into the fuselage assembly. First, make this mod before assembling the landing gear boxes (it's just easier). Second, consider using flush screws and nutplates (I used std AN515-8R8 screws and K1000-8 nutplates). Just remember, placement of the screw locations can be tricky due to the aluminum angle).
