Fitting the canopy bubble to the frame

[Marvin]

In a previous post I told you I cracked the canopy and was replacing it with a new one. I ordered new parts frame, canopy bubble and new skirts. When I put this bird together 10 years ago the canopy went together fairly easy fitting the the plastic bubble to the frame was no problem little bending here and there and it a little pushy on the canopy and it all fit real well. I cut the new canopy to the same dimension as the the old one. I put the old canopy inside the new one and tracing a line. Here's the problem the canopy at the rear portion is too wide for the frame. I know if I force it into fit it will only cause me problems down the line by cracking. I called Van's builders assistance and talk to one of the employees and they suggested that I cut the frame at the very end and spread it out to meet the canopy. I asked them if they were using a new supplier for canopy bubbles and they said no. They were using the same one but stated that the canopies are blown not in a mold but in a free style and each one is a little bit different. Has anybody else run into this particular problem when trying to fit the canopy to the frame?

Dick. N90774

[WA85]

I had the exact same problem. My canopy cracked during the build process and I had to repair it.

I ended up using the sika flex method to bond the canopy and fill in the gaps in the back 1/3 of the canopy. So far that has worked OK. Others report riveting it together and having a great seal of stress back there.

[Marvin]

Well misery loves company that's for sure. I haven't cracked the new canopy yet but I'm going to split the tail end of the frame and move it out about a half an inch on each side so it's under less stress on all parts. I can see the next problems fitting the skirt to fuselage. I talked to Todd of Todd's Canopy and asking about the problem and he said cutting the end of the canopy close to the frame might help. Van makes a good product but in the end the skill of the builder is the difference between completion and just gathering dust.
Dick N90774

[William Slaughter]

Cutting off the "tail" of the canopy worked wonders on mine. The conical shape formed by the very back of the canopy adds a lot of rigidity. As soon as I cut it off, the canopy readily flexed in to meet the frame. My final cut ended up with the end of the canopy about 1-1/2" forward of the very end of the frame, all covered up by the skirt.

[Marvin]

Bill this is Dick the guy with the RV 8 putting the new canopy on the frame. Can you send a photo of that area where you cut the canopy short of the frame at the rear? I talked to Todd canopies and he told me the same thing but I was not aware that the skirt covered that much area of the back. If I remember right the original skirt didn't cover that area for as much as you're saying. If you like you can send me the pictures direct to my email address if you don't know how to attach pictures to this forum. Send to. Rmjohnson32@comcast.net
Thanks
Dick N90774

[AAflyer]

Here's how mine turned out….mostly by accident. I had trimmed too much from the tail, too soon, and after getting the front, windscreen edge cut down to fit, the canopy had moved forward, thereby uncovering the aft end of the frame. But it turned out OK, since I needed to have more flex in that part of the canopy. The skirts covered the gap, but I'm sure most people could add fiberglass to cover the hole ( if you end up with one) when you glass the skirt ends together.

[Blain]

Originally Posted by Marvin

In a previous post I told you I cracked the canopy and was replacing it with a new one. I ordered new parts frame, canopy bubble and new skirts. When I put this bird together 10 years ago the canopy went together fairly easy fitting the the plastic bubble to the frame was no problem little bending here and there and it a little pushy on the canopy and it all fit real well. I cut the new canopy to the same dimension as the the old one. I put the old canopy inside the new one and tracing a line. Here's the problem the canopy at the rear portion is too wide for the frame. I know if I force it into fit it will only cause me problems down the line by cracking. I called Van's builders assistance and talk to one of the employees and they suggested that I cut the frame at the very end and spread it out to meet the canopy. I asked them if they were using a new supplier for canopy bubbles and they said no. They were using the same one but stated that the canopies are blown not in a mold but in a free style and each one is a little bit different. Has anybody else run into this particular problem when trying to fit the canopy to the frame?

Dick. N90774

Cut the frame??? Really?
Wrestle with the plexi. It will comply eventually. I have Todds. Just nibbled away a little at a time. It will settle down to the frame.

[Marvin]

First I would like to thank all that offer assistance in this job. The good news is I finally persuaded the canopy to adhere to the frame. I still have a long ways to go but I am getting there. When I get time and learn how will post a picture

Dick

[SgtZim]

I'm also concerned about this fit. IF I were to cut to the theoretical trim lines marked on the canopy, it would be considerably longer than the frame and the spot on the forward fuselage where the front of the windscreen is supposed to meet the skin, it wouldn't quite reach the top of the frame sides, and the canopy is still wider than the aft third of the frame by almost 2" on each side. Mine would almost fit right if I cut about 3" out of the middle of the bubble. I might have to almost do that. Fit the windscreen first, make the big cut, and re fit the canopy making a second big cut to match the windscreen ( yikes!)

I'm also kind of tempted now to cut off the back section off the frame.

Has anyone done this?

Going to use Sikaflex.

[izzybear]

The thing to realize about the canopy is that as you cut slices off the bottom incrementally, to ease the canopy into the proper fit, it changes all of the dimensions as it starts to settle into place. I worked on the front fit first and then the back and as I did, the canopy fit changed depending on how much I shifted the canopy forward or aft. That's what I mean about all of the dimensions changing - and why it is important to "sneak up" on the perfect fit just a little at a time. BTW, I ended up cutting past the trim lines and all fit well in the end. YMMV

The other thing I learned was that it was best if I clamped the canopy to the frame (for each test fit) at my location marks in the front bow first, and then from the aft end forward, because the forward 3/4 of the canopy already fit very close to the natural curve of the frame. So getting the front to lay down was the easy part. At one point when I was very close to the proper fit, I once clamped from the front towards the back and it changed the fit so much it that the aft end of the canopy no longer touched the frame - there was a 2" gap there...and I had a mini freak out! But when I realized what happened, I re-clamped from the aft end forward and all was well.

I was also told by Van's support that the front windscreen fit line was more of a guideline than a rule - as long as you don't conflict with the front baggage door, you are good to go.

I also know of at least one builder who, after making the big cut at the windscreen, cut the forward part of the canopy (think Targa strip), to shift the whole canopy forward...so do what works - just do a little at a time.