Matt's RV-7 Project

I marked a centerline on the outside of the lower canopy frame tubes, and drilled the C-660 side skirts to the frame:

I had to do a bunch of trial-and-error fitting of this area at the front of the skirts…

…because when the canopy is opening, the forward corners of the skirts want to dig into the fuselage decks unless you trim them back enough. I think I did an okay job here – there's a minimum but sufficient amount of clearance between the skirt and fuselage while the canopy is opening, which results in the minimum possible gap when it's closed. This will be covered by the fairing strip that goes over the rollbar, so it shouldn't leak much air. Also, note to self: Touch up the paint on the fuselage decks that you scratched up while fitting all this stuff.

The plans have you clamp the C-759 inside skirt to the C-660 skirt, and match drill the first four holes at the forward end:

Then you're supposed to sandwich the undrilled C-759 in between the canopy frame and the C-660 (both of which you already drilled) and just sort of let fly with the drill and hope for the best. I was skeptical, but it seemed to work okay on the second try. Here you can see the canopy sandwiched between the C-660 and C-759 skirts:

Unfortunately, on the first try I managed to let the C-759 slip down about halfway through, so the line of holes goes off in the weeds. This will cause edge distance problems once I drill the holes through the plexiglass, so I'll have to remake this part.

I also discovered that I need to remake both of the C-791 canopy skirt braces I made last week. You see, if you follow the dimensions in the plans, you end up with a bunch of places where there's not enough edge distance for the rivet holes. I'll have to make another set, this time substituting my own dimensions in order to make everything work. Sigh. Luckily these parts are cheap.

Hopefully the replacements will arrive by the time I get back from vacation. Sometimes I think I'm on track to set a new world's record for the number of RV-7 parts replaced. I guess that's what happens when you're a clumsy perfectionist…

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.