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-   -   RV-3B Dave's in Colorado (https://vansairforce.net/community/showthread.php?t=85658)

Larry DeCamp 03-30-2020 06:46 PM

Thermal expansion
 
David,
Not that you can change it, but think about thermal expansion. Most canopies curve up and leak air . Probably not a problem in the summer, just something to keep in mind as you approach the finish line.

David Paule 03-30-2020 08:18 PM

Thanks! I've got something in mind that might help, maybe. we'll see. I plan to have a canopy latch at the aft end of the canopy frame. It'll be operated by the same handle mechanism as the main latches.

Dave

David Paule 04-04-2020 07:26 PM

Canopy Flange Removed
 
The canopy is taped and there?s plastic on the interior. I used the same 4 mil plastic on the interior that I?d used for the fairing. The outside plastic is the green cling wrap that AeroCanopy used to ship it. The yellow tape is one of the Frogtape line, for delicate surfaces. This taping is to let me trim the forming flange off the canopy. Wirejock, who?s ahead of me on his RV-7A project, recommended the tape.

I tried a Dremel diamond cut-off wheel. It gave a nice fine kerf but was terribly slow. Maybe I shouldn?t have used it to cut aluminum earlier. Then I tried Dremel?s cut-off disk and it was somewhat faster, but the ice cream in an ice cream cone would melt on a sub-zero day before that did the job. Next up was a cut-off disk in an air die grinder. That worked. Plus I got to listen to the air compressor the whole time. That Harbor Freight die grinder really gobbles the air.

Now I have these canopy flange cut-offs.



I lifted the canopy fairing off the fuselage and laid it on the canopy. This was an iterative process, since I had to reposition the canopy in its cradle. The canopy, unrestrained, is somewhat wider than the canopy frame that Van?s describes in the plans on Drawing 33. The cradle is cut to match that, but at the exterior surface. The plans shows how the sides of the canopy actually curve inward beyond the semi-circular, and with the canopy in the cradle, mine does too.

Once the canopy was properly positioned in the cradle, I put the fairing back on. Then came an hour of adjusting it this way and that, trying to align the two together.



Fore and aft was easier than I had expected. Lateral was a bit harder, and I'm not satisfied in roll yet. I?ll probably tweak it some before I mark the canopy for trimming.

Dave

David Paule 04-09-2020 06:08 PM

Clipped In
 
After some more trimming, 1/2” at a time, I ended up with a total of 1 1/2” trimmed off at the front and back. The overall fit is reasonable. Here’s the canopy, free of its cradle and unrestrained, resting on the fairing.



Up close, the canopy edges are generally further from the fairing than I like, but I can’t trim it any more because it’s beginning to intrude on the 1” clearance I wanted around the roll bar. It would be a mild disaster if it contacted the roll bar. Back in the cradle, the gaps are considerably reduced. No surprise there, since that’s where it was when I trimmed the canopy.

Remember that the cradle compresses the sides of the canopy to match the factory frame that I’m not using. It seems to increase the height of the canopy slightly, too, so if I could hold the canopy in this restrained shape, I’d get a better fit to the fairing and more roll bar clearance - worth trying.

I made a half dozen clips from .040 that I could cleco to the fairing. Since the fairing rests directly on the fuselage skins, the only place I could cleco them on is in the area of the cockpit. Fortunately I’d marked that some time ago. Unless I drill into the tailcone skin, though, I can't add a clip in the aft portion.

Here the canopy is, clipped to the fairing. It reduces the canopy width by about an inch and increases the depth by about 1/8”, not much but a reasonable percentage increase in clearance. If you compare these two photos, you might be able to see the better fit.



Now I’ve got to figure out the next step. While I’m letting my subconscious work that out, I’ll be smoothing the canopy edges and doing some minor tweaks.

One thing that I was pleasantly surprised with, was that the canopy trimming, at least so far, was fairly straight-forward. The cradle holds it securely, and I expect that helped a lot. My air die grinder really drinks compressed air; the compressor was running for hours.

Dave

DHerzTX87 04-10-2020 11:20 AM

Very nice work! It’s fascinating to watch the progress through your great sharing of your photos and thought process. I’m curious what you’re plan is to reinforce the canopy/fairing junction. How much lip or overlap do you have on the inside for a fillet? What material or adhesive do you plan to use?

David Paule 04-10-2020 01:33 PM

I don't have a plan yet, but I do have some of the Rutan BID and some UNI fiberglass cloth and some 3/8" PVC foam that I can use for a core if I want to and can afford the cockpit volume.

The inside of the fairing, in the cockpit area, will be trimmed flush with the canopy, and an internal flange built up from there. I'll make an outside flange first. Aft of the roll bar, it's all TBD. Right now, the fairing goes across the top past the sides of the canopy, and I'll decide later what to cut away. There will be a bit near the aft end as part of the aft-most canopy latch that I'm adding.

I'm using those materials plus Jeffco 1307 LV laminating resin and the medium hardener, from Spruce. All these materials are well-proven and reliable, which is more than I can say for my own workmanship.

Dave

David Paule 04-20-2020 09:20 AM

Well, I started making the canopy flange. The edges of the cut fabric started fraying and sticking to my hands. While fighting that, the epoxy kicked off.

I pulled the flange material off and threw it away. I'm waiting on more material now since that was the last of it. The next day, I removed most of the duct tape I'd used as a mold release since it was coated in epoxy.

Dave

David Paule 04-27-2020 07:34 PM

Canopy Flange Formed
 
The canopy got re-taped for the second flange attempt and after buying more materials, I succeeded in laying up the canopy flange. This time I used 3” fiberglass tape and 4” peel ply tape. It turned out that the epoxy remaining in the cans was just enough to do this task and I didn’t need to open the second can of the Rhino (or Jeffco) epoxy after all. Yet.

Here’s the flange with the external peel ply pulled off. There’s a bottom layer of peel ply that’ll come off when I remove the flange from the fairing and canopy.



Some work is remaining, such as trimming the edges and probably some other things that I don't know about yet.

Dave

rph142 04-28-2020 10:44 PM

Very nice work Dave. That was by far my least favorite part of the build. It?s all downhill from there.

David Paule 04-29-2020 08:08 AM

Canopy Flange Successfully Off The Fairing and Canopy
 
Thanks, Rob.

The flange came off of the fairing with some difficulty. The tool that helped was a strip of 1 x .063 aluminum left over from the exoskeleton, with tapered edges. I used this to break the seal between the fairing and the duct tape under it. Then all it took to remove the flange from the canopy itself was a tapered piece of plywood and some body English. Pulling the peel ply off was its usual fun, and included swearing and a modest blood donation.

I?d put a few cleco holes in the flange and fairing to register it afterwards. Here?s the flange on the fairing without the canopy. Later, the canopy went on ok and I marked the flange for trimming.



Dave


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