Matt's RV-7 Project

The normal way to remove a completed sliding canopy from a side-by-side RV is to remove the bolts that attach the WD-644 canopy rollers to the slider frame, then lift the frame up off the rails. I realized that if I could make it relatively easy to remove the rear anchor pin blocks (which also function as the aft canopy stops) it would then be a cinch to instead slide the canopy straight back until the rollers slid out of the side rails. By removing the canopy that way, you avoid tearing up the paint on the roller weldments, and you don't have to mess around with trying to get a wrench on the nut that attaches the roller to the frame.

The challenge, though, is that the design of the rear anchor block mounting bracket prevents you from removing it from the fuselage unless the canopy is removed first. You have to start by removing the screws that capture the plastic block within the U-shaped bracket, so that you can remove the block and get access to the bolts that hold the bracket to to the fuselage longeron. But of course, you can't get at the screws in the first place, because the canopy side skirts are in the way.

So, my bright idea was to modify the C-677 rear pin anchor block mounting brackets by riveting some MS21051-L3 nutplates inside:

Now instead of using bolts through the top of the brackets and nuts on the underside of the longeron, the bolts come up from underneath:

To provide clearance for the nutplates and bolt threads, I drilled very slightly into the plastic anchor block: (hard to see in this photo)

Now I can remove the entire anchor block/bracket assembly from inside the fuselage, then slide the canopy backwards off the rails until it can be lifted straight up and stored safely. Hopefully this will prove to be a useful modification down the road. I will mark the bolt heads with inspection lacquer and check them periodically, although they are plenty snug in the nutplates right now.

I used the hole finder to drill the last two holes in each side of the canopy skirt – they're the two silver clecoes in the middle of this photo. Also notice how the fiberglass skirt here on the right side of the airplane is slightly too long to match up to the edge of the C-660 side skirt.

On the left side, the skirt is slightly too short. Something must have gotten misaligned pretty early on. But it's no matter – I just cut a slight (1/8") taper on the rear corner of the left side skirt, and sanded the fiberglass skirt to match. Then I cut the same taper on the right side skirt and trimmed and sanded the fiberglass to match over there too. (Heaven forbid I shoud have an asymmetrical canopy!) It looks nice now, even though I seem to have forgotten to take a picture.

On the left side skirt, I trimmed an inch off the upper rear corner, where the bottom-most rivet hole in the plexiglass had way not enough edge distance on the aluminum skirt. This will all be covered with the fiberglass skirt once it's all put together.

Once the bottom edge of the aft skirt was finalized, I sanded a nice round profile on the protruding front corners, using a quarter to gauge the radius. (I used a Kentucky state quarter, but I think you could use any of the southern states with good results.)

Overnight I figured out how to fix the misalignment of the canopy skirt mounting holes. The nice thing about fiberglass is that you can usually fix your mistakes with enough patience and sandng.

I applied a layer of packing tape over the holes on the exterior surface of the skirt:

From the inside, I used a popsicle stick to force a thin epoxy/flox mixture into the holes. After I took this photo, I came back and squeegeed off the excess flox.

Once that was cured, I removed the tape and did the same thing from the exterior side, to fill both sides of each hole. When that was cured, I sanded it all flush. Here's the result – no more holes:

Then I put the skirt back on the plane, and after a great amount of measurement and double-checking I re-drilled the holes. This time it came out straight.

In some places, yesterday's holes were okay, but in others they were substantially off:

Since the alignment of the skirt to the plexiglass and frame was now acceptable, I went ahead and drilled most of the holes that attach the rear skirt to the C-660 side skirts. There are still a couple holes on either side that need to be drilled (where the obvious gap is in this photo) but I wanted to finalize the alignment before I removed the skirt again.

Without removing the skirt from the plane or otherwise disturbing the alignment, I drilled straight through the skirt, canopy, and steel frame with a 1/8" plexiglass drill, enlarging the holes in the skirt and frame to the final size (note copper clecoes in this photo). The holes in the canopy were already at 1/8", and will be enlarged to their final size of 3/16" soon.

Back on the worktable for more surface preparation and pinhole filling:

Yet more sanding… this time down to 400 grit.

I didn't like the blunt shape of the leading edge of the skirt up in the thickest part of the middle where the glass layers were doubled up, so I sanded it to get a gentler slope. Of course this means I'll have to do more pinhole filling here.

I re-drilled the skirt to the canopy using a hole finder, since the previous pilot holes got closed up by fiberglass filler. I think it must have slipped a little bit this time, though, since the alignment is ever so slightly skewed. It still fits and nobody but me will know it's crooked, but I may yet try to fix it. Not sure what I'll do about this yet.

I clecoed the C-653 cover strip in place and marked a line where the rear skirt overlapped it. Later I trimmed the cover strip so it ends just at the leading edge of the skirt. In retrospect, it would have been cool to mold the fiberglass skirt to fit over the cover strip perfectly, but I didn't think of it until it was too late. Oh well, a simple trim works just as well.

Also, my propeller governor arrived today. It's a PCU-5000 that I picked up for a good price through the VAF group buy that was organized a few months back.