Dave’s RV-7A Building Log

I countersunk the rest of the holes in the canopy bubble. I found two things made it much easier. First, I put some tape down around the hole. That kept the countersink cage from marring the surface of the plexiglass, so I didn’t have to worry about it.

The second improvement was using Boelube on the countersink cutter tip. That helped keep it from binding and thus the possibility of cracking. I also drilled all the holes out to 5/32″ with a plexiglass drill bit from Cleaveland, and deburred the back sides of the holes. The main bubble is now done, except for maybe some more tweaking of the aft edge. The next work item will be countersinking the rear window.

I needed a break from plastic work. I pulled out the raw stock for the canopy strut and started fabricating the parts. Strangely, there was not enough material to make the spacers for the aft attach points. I ended up using some .250 bar stock that I had left over from the canopy hinge points. That will look better than two layers of .125 anyway.

I started the very long process of countersinking the holes in the canopy. I’ve been putting this off as countersinking is my least favorite task. I did a couple of test countersinks in some scrap and confirmed that Dan’s measurement of 9/32″ diameter is perfect. I got about 1/8 of the holes done.

Tapped some of the holes in the roll bar for the rear window, but spent most of the day on fitting the rear window. I wanted to get the canopy/window fitted this weekend, and I think I’m about there. The gap between the canopy and rear window looks very good. It’s about 1/32″ and even all the way around. It took several iterations of removing the canopy or rear window and sanding to get it looking good. Once the frame is riveted and the plastic screwed down, I’m anticipating doing some tweaking, but it’s 99% there.

I spent quite a bit of time fitting the rear window. I had to trim a little bit more from the middle aft edge of the window so that it would fit. There’s a chunk of aluminum there that’s part of the Van’s service bulletin for improving the connection between the roll bar and the F-706 bulkhead.

From there I started drilling the rear window. I followed the instructions exactly. I started at the top and worked my way down both the front and back of the window at the same time down the left and then right sides. Along the front, I drilled the window with the 1/8″ plexi drill bit until it made a small divot in the roll bar. I then used my other drill with a #40 drill bit to finish the hole in the roll bar. Along the aft edge of the window, I just drilled with the 1/8″ plexi drill bit through the skin and window while holding the window tight up against the skin. It turned out great.

From there, I decided I might as well trim the aft edge of the rear window. That way I wouldn’t have to do any more nasty trimming with the cut off wheel. I drew a line on the window where the top skin hit the window, but it made more sense to base the cut off line on the holes. I put marks a certain distance (which I can’t remember right now) from the edge of the holes. I connected the dots with masking tape and did the final cut followed by smoothing with sandpaper.
Drilled rear window
More rear window trimming and deburring

I deburred various holes in the canopy bubble and frame. I also spent some time laying out the holes along the rollbar and top skin for the rear window. I pre-drilled the holes in the top skin to #40. I decided not to pre-drill the holes in the roll bar. Since the roll bar is a closed structure, there’s no way to get a nut on the screws. The instructions and plans call for tapping the holes. Thus, those holes don’t get drilled out to 1/8″. You’ll see what I ended up doing tomorrow.

I trimmed the rear window to 1.5″ aft of the line I drew when I put the top skin on. This is what the instructions recommend as a starting point. (Actually they recommend 1.25″, but 1.5″ seemed safer.) Cutting around the curve is fairly difficult with the die grinder wheel. Hopefully, I will only have to use the cut off wheel one more time for the final trim on the rear window.