Matt's RV-7 Project

The sliding canopy is held shut by a simple latch that engages a pin welded to the rollbar. The latch mechanism also doubles as a handle you can grab to open and shut the canopy from inside the cockpit. I assembled all the parts per the plans, then spent some time filing material from the latch arm until it fit properly.

Here it is being fitted to the canopy and rollbar. I had previously filed enough excess material from the steel latch pivot tube to place the latch arm at the proper vertical position relative to the pin. The latch shuts with a gentle over-center action, just enough to keep it from vibrating loose; I didn't want to force it to put a lot of strain on the canopy and maybe break something later.

The exterior latch handle is made from a piece of tapered aluminum stock that Van's gives you, which you're supposed to whittle into a pleasing streamlined shape. Me being me, I spent the extra bucks to order a nice machined handle, which should arrive one of these days.

Lately I've been taking a lot of closeup photos but no shots of the big picture, so here's a snapshot of the current state of the canopy. You can see the afforementioned latch, as well as one of the pins and anchor blocks I was working on yesterday.

Finally some progress… I know you've all been waiting to see some more blurry pictures of shiny objects, and tonight's update shall not disappoint.

One job I have been putting off until I was sure I needed to do it was trimming the rear ends of the canopy slider tracks. There is a little detail in the plans that shows a relief notch cut into the tracks to let the side skirts clear, with a note saying you should do this "if/as required". I did some playing with aluminum scraps and determined that I did need to trim the tracks to keep the skirts from rubbing, so I guess it is indeed required. First I roughed out the shape with a unibit and hacksaw:

After a bunch of filing and scotchbriting, I had a nice notch cut in each track and all the material for the side skirts to catch on was gone.

By the way, I'm really glad I attached the slider tracks with a nutplate strip instead of nuts and washers – it would have been a huge pain to take the tracks on and off multiple times to get this area to fit correctly.

Then I started on the blocks that anchor the pins that are welded to the aft corners of the canopy frame. Each one is held in place by a U-shaped bracket, which is bolted to the fuselage longeron. I intially drilled the holes only to #30, and temporarily attached the brackets with 4-40 screws in order to be able to fine-tune the fit later if needed.

Next I put the plastic blocks into the brackets, scribbled some sharpie ink in the approximate area where the pins would contact the blocks, and slowly slid the canopy forward. At the spot where the pin touched the block the ink was wiped away, leaving a clear indication of where the drill the hole for the pin. I center-punched the spot and the hole location was marked. Simple.

I transferred the angle of the pin to the top and side of the block so I could have some lines to sight along while getting ready to drill:

The hole you have to drill is parallel to nothing, which makes it tricky to get it lined up. I borrowed a Panavise from work, which made it a lot easier to get the block aligned in the drill press. The pins are 1/4" O.D., but since holes in this UHMW plastic stuff shrink after you drill them, a 1/4" hole in the block caused the pin to be an interference fit. So, I used a 17/64" drill bit I borrowed from Scott to slightly enlarge the holes, and that made everything happy.

Then I drilled the bolt holes in the brackets and longerons to final size, and bolted everything together. But oh by the way, these are also the stops that keep the canopy from rolling off the back of the slider tracks, so in order to remove the canopy and work on anything I had to unbolt the brackets, slide the canopy off, and re-bolt the brackets on. This slowed me down a lot because I kept needing to remove or replace the canopy in order to get anything done.

After that I put the blocks into the brackets, slid the canopy shut (the pins fit in the holes, hooray!) and used C-clamps to immobilize the blocks in the correct position. Then I drilled holes for the screws that attach the blocks to the brackets, drilled the holes in the blocks up to #10 to let the screws fit through the plastic, reassembled everything, countersunk for the flush screw heads, and bolted it all together. Throughout this process I had canopy on and off many many times. Whew.

I may come back and countersink the screw holes a little deeper if I need to later on, but for now I didn't want to wallow out the hole too badly. This will all be covered by the canopy skirts later, so it's not critical.

This afternoon I fabricated the six pieces that form the lower canopy skirts. Here are the C-759 and C-791 pieces after being cut and deburred. I used a hole saw to cut the lighteninng holes in C-791, then went through three or four scotchbrite wheels deburring the insides of all the holes. That was kind of tedious.

I cut the C-660 side skirts out of the supplied raw sheet stock, and then painstakingly measured and marked the locations of each of the four rows of holes that go in this part. That kind of sucked because each row has a different rivet spacing, and the vertical and horizontal spacing measurements are actually given on two separate drawings. To avoid doing it all twice, I lined up both parts and match-drilled them both together at the same time.

Here's the finished result. Hey Van's, how about making these prepunched parts? This sure seems like a good application for one of those fancy CNC machines – flat sheets with lots of precisely-located holes in them.

Not much work on the airplane this weekend, and even less that was worth photographing. I spent several hours sanding the edges of the canopy with increasingly finer grades of sandpaper, starting with 120 grit and working my way down to 600. Then I broke out this buffing wheel and plexiglass polishing compound that I'd previously ordered from Ridout Plastics. (Nice people to deal with on the phone, but they really screw you on shipping – $25 in shipping and handling fees for ten dollars worth of parts?!?)

The special "plexiglass polishing wheel" turned out to just be a normal garden-variety soft cotton buffing wheel. The polishing compound, however, was interesting – instead of the liquid goo I'm used to seeing for a buffing/polishing application, it was almost like chalk in composition. To get it where it needs to be you peel back the cardboard tube and run the wheel across the chalky stuff until it picks enough up.

It certainly did the trick – the edges of the canopy and windshield are now as smooth as the edges of a pint glass. Excellent.

I think I may have finally seen the last of the most obnoxious plexiglass work – or at least I don't think I will need to do much more cutting or sanding. (and I also have enough magic polishing stuff to do another dozen airplanes)

The next tasks will be the canopy latch handle and the rear latch blocks, but I have other stuff I have to do first.

In order to fit the windshield to the fuselage, I clecoed on the forward top skin and bolted the rollbar brace in place:

Here's the windshield on the fuselage before any trimming was done. The contour along the front doesn't match the fuselage all that well.

Here it is about halfway through the trimming process – getting better.

There isn't a lot of excess material to work with at the rear corners – actually the glass just barely overlaps the side skin. In retrospect, I wish I had waited to trim the lower edges of the canopy until after making the big cut, but I was blindly following the plans and didn't know any better.

Much trimming and belt-sanding later, I got the front contour to match the fuselage shape pretty well. Once the windshield is fastened down, there will be essentially zero gap here.

There is gap of about a quarter inch on both sides of the windshield where it turns aft towards the lower corners. The fasteners will pull this in somewhat, but I'll still have to cover it up with the windshield fairing. If I'd had more material to play with I think I could have made this come out better, but overall it's not too bad.

I duct taped the windshield to the rollbar in order to measure the height difference between the windshield and canopy:

The apex of the canopy was about 3/16" higher than the windshield. To fix this you can either raise the windshield with shims, or lower the canopy. I chose the latter because of the afforementioned issue at the aft corners.

The canopy is lowered by whacking a piece off both ends of the forward bow tube:

With the canopy back on the rollers, there's now a smooth transition between the top of the windshield and the top of the canopy:

With the height properly set, and everything clamped straight and true and triple-checked, I drilled the holes for the screws that attach the rollers to the canopy frame:

The canopy rolls very easily, thus making the hours of fitting and measuring that led up to this point all worth it.

The next job was to drill the windshield to the rollbar, so I started with the same masking tape setup I used to drill the canopy to the slider frame:

Here is it after drilling. Because of the angle the windshield makes with the rollbar, the actual centerline where the holes need to go is not where you'd imagine it would be just by looking at it – it's important to use the tape method to get everything square.

The glass overlaps the side skin by about 3/16" on either side. This will all be hidden by a fairing later.

In the photo below you're standing on the right side of the fuselage looking forward towards the firewall. The rollbar and slider frame contours don't quite match, so the windshield bulges out from the canopy by about 1/8" at the 10 and 2 o'clock positions. This will also be covered up by a fairing. I'd be worried if the canopy was sitting proud of the windshield because that would have made the fairing difficult, but this way should be no big feal.

I still need to do at least one more round of trimming to finish off the aft edge of the windshield and finalize the gap between the canopy and the side frame tubes, but I'm hot and tired of being covered with grit.

Update: I couldn't resist spending another hour grinding away and making a mess. I got the canopy trimmed to its final size (I think) and I cleaned up the aft edge of the windshield. Of course I then had to take another shower to wash off all the grit. My next airplane will have a solid aluminum canopy and a TV screen to let me see out.