Dave’s RV-7A Building Log

I psyched myself up for the big drilling event. The temps here in Seattle have been cooling off. It was around 70 degrees in the garage. I pulled out the heater and put it in the baggage area pointed toward the cockpit. With it set on low, it heated up the area under the canopy to a nice 80-85 degrees. I let that run for about an hour to make sure everything was heated up. During that time I made double and triple sure the canopy was exactly where I wanted it, taping down the front and sides and clamping the aft edge. With Julie pushing in on the side, I drilled every other hole from the top down the aft edge and then forward along the side. We repeated that on the other side. I then went back and drilled the other holes. I used a fairly slowly turning drill, and let the drill bit cool off frequently. Of course I used a 1/8″ drill bit that is made just for plastics. It’s a little difficult to line up the drill bit with the #40 hole underneath. You just have to look at it from a couple of different angles. I let the 1/8″ drill bit enlarge the hole in the underlying aluminum frame after going through the plastic.

The whole thing turned out great, and was not nearly as stressful as I thought it would be. I have just a tiny bit of trimming/sanding to do along the sides and aft edge. The middle of the front edge lifted up slightly–maybe 1/16″. I’ll do a tiny bit of sanding along the front as well.

That was all the time I had for the project, so I removed all of the clecos to relieve any pressure on the canopy.

I had previously marked on the canopy frame aft ribs the locations for the screws in order to crimp between them. I used those marks to drill #40 holes. I also marked out a 2″ spacing for holes along the sides of the frame. While the canopy bubble was off, I sanded the sides and aft edge with a long board and sandpaper. That cleaned up the edges nicely. I also took some finer sandpaper and cleaned up all of the edges really well. I removed all of the tape from around the edges of the bubble, so I could see to drill through to the frame. With Julie’s help this time, I placed the bubble back on the frame and got it all positioned for drilling.

I’ve been planning tonight’s work session in my head for a few days and was finally able to execute. It always helps to have a clear plan in mind before heading to the workshop.

I first marked along the front of the canopy where a tiny bit more trimming was needed. I removed the canopy and drilled the splice plate for the rear ribs using the template that I previously attached.

I then used a multitude of clamps to hole the side rails in the perfect position while I drilled them to the ribs. (Unfortunately, the camera battery died at this point, so no pictures.) I clamped the skirts to the side rail to make sure they lined up nicely with the sides. I also clamped the top part of the rail to the rib, so that the plexiglass can make a smooth transition from the ribs to the side rail. While the bubble was off, I also opened up the slots a bit more with the Dremel. I think I’m at the point of diminishing returns there. The fit doesn’t seem to be improving any more.

After using the belt sander to trim a little along the front, I put the bubble back on. I carefully marked the final trim locations for the sides and back of the canopy, while clamping the aft edge down and trying my best to hold in the sides. I used the cut off wheel a little bit, but mostly the belt sander to take off the tiny bit needed. After cleaning up the edges, I put the bubble back on. The fit is really looking good now. I’m trying to decide now whether to go ahead with the drilling to the frame before or after cleaning up the aft edge.

We went camping this weekend so not much happened on the plane. Getting back fairly early on Sunday I tinkered around a little bit. I crawled inside the fuselage and fitted the rear ribs of the canopy frame to the bubble. The instructions are a bit contradictory. They say to drill these ribs to the frame sides before fitting the canopy and then they say to drill them after pushing them up to the bubble. Several builders suggested waiting to drill, so that’s what I did. I’m glad I bothered to actually crawl inside. I had the two halves off-center. I shifted them over and then pushed them out to meet the bubble.

I wasn’t motivated to do much else. I flipped through the Van’s parts catalog a little bit trying to figure out what parts of the firewall forward package I need to omit.

I didn’t get too much done due to packing for the upcoming weekend of camping.

I removed the canopy again. This time I used the Dremel and a cutting bit to enlarge the slots quite a bit. I also clamped the rear ribs of the frame in place in preparation for fitting them to the canopy. After putting the canopy back on, the fit through the slots is getting slightly better. The canopy still wants to bow out quite a bit right at that spot.

I decided to try and fix the canopy frame alignment problem, the gap at the left front. I drilled out the rivets in the frame around the hinge arm. I temporarily put .625 shims in between the front of the frame and the flange for the hinge arm. I clecoed that together and re-installed the frame. That brought the frame too far forward, so I tried .40 shims. Clecos don’t pull the parts together quite as close as rivets, and that has a huge effect on the fit. I ended up going with the .40 shims and riveted the joint back together. Now the gap on the left side is around 1/16″ and the right side is 3/64″. I can live with that. The gap also seems to change when I put pressure on different parts of the canopy skin, so the whole thing might change once I rivet on the skin. I was afraid the shims might adversely affect the fit of the skin to the frame, but the holes still line up pretty well. The aft row of holes need to be enlarge to #30 anyway for pop rivets.

The canopy frame has been the most difficult part in the kit to deal with so far. Considering the complexity of the part, the several different Al parts welded together, the fit was remarkably good out of the box. However, getting the perfect fit dialed in has been very frustrating.

While I had the canopy bubble off, I did one more round of trimming on the front of the canopy and enlarging the slots in the canopy skin. That fit is looking really good. I think it’s finally time for the final trim on the sides and back of the bubble.

I did two more iterations of marking the front of the canopy, removing it, trimming slightly with the belt sander, polishing the edge with the orbital sander, and putting the canopy back on. I also did one more round of enlarging the slots on the sides. Somewhere in there I also removed the canopy skin, drilled the tabs, and riveted them. Right at the seam between the front canopy frame and the sides, the canopy was sitting kind of tight to the frame. I used a Crescent wrench to bend the frame inward slightly on both sides. That improved the fit quite a bit. In the end, the front of the canopy was sitting down very nicely on the skin with just a few gaps of 1/16″ or so. Maybe one more round of trimming. It’s important to hold in the sides of the canopy when you’re looking at the gap, because that tends to lift the front of the canopy in the middle.

This part of the canopy fabrication definitely takes a lot of patience. I can see why it’s called more of an art than a science. I can’t remember where I read the tip of using a belt sander to do minor trims on the canopy, but that has really worked great.

One other issue that’s been nagging me is that the gap at the front of the canopy skin somehow opened up to 1/8″ on the left side. The right side is a perfect 1/32″. I was ignoring the problem until Julie brought it up again. She noticed that way before my beautiful work on the fit of the canopy bubble. The gap was perfect when I drilled the hinge points, but I guess I had the frame at a bad angle. I don’t know how else it could have happened.

My first thought was to order new plastic blocks for the hinge point. I could redrill the hinge point and pull it forward a little bit on the left side. But then I had possibly a better idea. I could drill out the rivets where the hinge arm is attached to the front of the frame, stick some shims under there, and re-rivet. That would essentially do the same thing, pulling the canopy frame forward. There might be a slight side-effect of screwing up the fit of the skin to the frame. I’ll have to think about it a little more and maybe call Van’s help line.

On a side note, if you haven’t checked out RunwayFinder already, you should. That’s a little side project I’ve been working on for a few months. It turned out pretty nice so far. I posted a note about the project on a Google Maps forum last Thursday to get some advice from the experts. That generated some positive comments. And then suddenly on Monday word hit the pilot communities. The number of users on the site went from the dozens to 2,000. And then 3,000 today. I’ve gotten a lot of postive feedback in the forums and email. I’m glad the site is proving to be popular. Makes the time I spent on it away from RV building worth it.

It took about half an hour to fix my boo-boo with the canopy frame tabs that I noticed yesterday. Luckily, I’ve gotten pretty good at drilling out rivets. With the tab on the inside like it’s supposed to be, the canopy was fitting much better.

I did one more round of filing the slots and two rounds of trimming the front corners, first with the cut-off wheel and then with the belt sander. The gap up front is looking much better–around 1/16″ to 1/8″. Holding in the sides definitely makes the front pop up. I’ll probably do one to two more rounds of conservative trimming.

It’s not really explicitely stated anywhere in the instructions, but this seemed like the right time to get the canopy fitted into the slots in the canopy skin. I enlarged the slots roughly following what Dan did. I propped up the front of the canopy with a couple of chunks of 2×4, filed the slot a bit, and then tested the fit.

I got it fitting pretty good, but it was still bulging out quite a bit at the front of the sides. And then I discovered the problem. Even after double checking the drawings, I managed to rivet the sides to the canopy frame with the tabs on the outside instead of the inside. Doh! Should be a simple matter of drilling out a few rivets and re-positioning the tabs. The canopy will never fit correctly the way it is now.

Today was a big day. With the front gap down to 1/8″ and the gap over the roll bar at 3/8″ and the temps in the mid-70s, it was time to make the big cut on the canopy. I made sure the canopy was centered well and taped it down securely with duct tape. I used some wide 2″ tape to follow the line I made previously on the roll bar. It took quite a while to get it perfectly on the line. Following Dan’s method, I put some tape 1/32″ away on the other side of the mark and built up both sides with another couple of layers of tape. While I had the canopy perfectly positioned, I put the top aft skin on and marked a line on the canopy where it hit.

Rather than just use a couple of saw horses, I made a platform 4′ wide for the canopy to sit on. This worked out really well. I put blocks on either side to keep the canopy from springing out.

The cut went extremely smoothly. I taped the pieces together every 6″ or so. As it turned out, I forgot to cut the plastic on the inside. That actually helped keep the pieces stabilized as well. I cleaned up the edge with a belt sander and orbital sander.

With the canopy split in half it is much easier to maneuver. I was able to put it on and off the fuselage solo, speeding things up quite a bit. The fit turned out really good. As expected, the canopy tilted a tiny bit, which caused the line at the back to be off by about 1/8″ at the bottom on each side–not bad.

I made a few more iterations of trimming the front of the canopy to reduce the gap at the front. In that process, I realized that I hadn’t cut off the front corners symmetrically. I fixed that issue, which then caused the canopy to sit a little further down on one side than the other. I adjusted the position of the canopy slightly, which caused problems with the cut at the back, but that needs to be straightened up anyway.

With the canopy in its (hopefully) final position I taped it down again and marked the approximate location of where the side cuts needed to be. I cut them off, cleaned up the edges, and put the canopy back in place.

Long day, but big progress! Call me warped, but I really enjoy working on the plastic. It cuts and shapes really easily. It’s also a big bonus that the weather is hot enough right now that I don’t have to mess with heaters.