I had always intended to build access panels into the forward fuselage skin to give occasional access to the avionics mounted underneath, but hadn't gotten around to it yet. Then Van's came out with their own access panel kit, which saved me the hassle of completely building them from scratch.
The installation of this kit is pretty straightforward. First I set the top skin in place with enough clecoes to make it conform to its final shape in the area where the panels will go:
Using the provided tabs, I clecoed the hole doublers to the firewall:
Then I match drilled all the rivet holes through the doublers into the skin. You're also supposed to drill the screw holes up to the final #19 size at this point, but I decided to drill them only to #30 to match the pre-punched #30 holes in the access panel covers. You'll see why in a moment.
With the doublers removed, I clecoed the panel covers to the skin and carefully traced around the outside with a fine-tip marker:
I used the air nibbler to rough-cut the holes in the skin. No going back now!
To finish the holes I used a series of grinding wheels, sanding drums, and files, iteratively sneaking up to the cut line:
If you take care and work slowly, you can get a good fit here. (maybe in a future RV kit these holes will be CNC-cut, wouldn't that be nice?)
I'm happy with the way these holes finally ended up… I have an even and consistent panel gap all around the perimeter of both panel covers:
With the holes complete, the temporary locating tabs removed, and everything deburred, I clecoed the doublers to the inside of the skin, then clecoed the skin to the fuselage:
At this point I clecoed the cover plates to the doublers, positioned to give an even panel gap all the way around, and drilled the #30 holes up to #19. Doing it this way adds a couple minutes of extra work, but it ensures that everything lines up perfectly. You probably don't have to do this step with the skin mounted to the airplane, but I wanted everything to assume its final shape before drilling.
After that I deburred and dimpled all the holes, and riveted the nutplates to the doublers. Then before riveting the doublers in place I applied a thin bead of RTV to seal out water:
After riveting I cleaned up the squeeze-out, giving a pair of nice-looking holes:
Skin installed back on the airplane for one last test fit:
The panel covers fit so well I didn't even bother running any screws in:
These access panels will be invaluable for maintaining the various things hidden under the top skin, not to mention riveting the top skin in place when I get to that step.