Jeff R

Jeff R

Well Known Member
I have been putting off work on the canopy frame for a while, reading what I could find to get an idea of what the heck to expect, and finally decided to just go out and start doing it. I was amazed that everything seemed to line up. The side of the frame matched the fuselage sides exactly in shape, and I only had to spread the frame out a bit to make it even on both sides and about 1/4" inside the skins. Even the top part of the aft bow was right at 1/16" below the aft skins. Wow. Then I looked at the gap between the roll bar and the foward bow of the canopy. It is 1/8" at the bottom, but then widens to 5/16" at the top. I can lift up the aft frame about an inch and make the forward bow line up with an even 1/8" gap, but if I do that the top aft part is about an inch above the aft skin and, of course, is higher and forward to the slide rail.

I should add that I cut the lower front tube that the rollers mount into of the canopy so the vertical distance between the top of the roll bar and the top of the forward bow is not quite 1/2". I know this distance is supposed to be 3/8", and I will trim it down later, but that will not be enough to close the gap.

Any ideas on how to tackle this?

I checked the angles, and the roll bar is 90 degrees to the longeron, and the forward bow is 90 degrees to the side rail of the canopy.
 
Shims !

Jeff, I know this sounds too easy but just try putting about a .040 or .063 shim under the front roll bar bolt. That will lean the top back toward the canopy frame and give you a nice consistent gap.

That will leave a little gap showing from inside the cockpit going from the back to front where the shim is. Use anything you like to fill that. Urethane seam sealer, fiberglass, whatever you like. When you paint over it, you will never notice it.

If you wanted a solid shim, then put the one small one up front, build up a layer of JBWeld the lenght of the roll bar, cover with plastic, put on the roll bar, wipe off the excess and let the JB sit up, pull off the bar and plastic, and you have a custom full lenght shim.

Just one option. Worked well for me.

Bill S
7a finishing
 
Have you

fitted the canopy yet? I found that that plans 3/8" space at the top was off a lot. If you haven't put the canopy on yet I wouldn't mess with anything until you trial fit it. It's the canopy that has to be right-the frame only attaches it to the fuse. Put all your hardware on the frame also-don't cut anything yet. I cut the front bow to the plans height and had to add it back to the front bow so the canopy was resting on the frame and not down below the windshield. What is 3/16's of an inch? Not a lot to worry over. Don't forget to put the canopy latch on as well-it has to line up.
Mike H 9A/8A
 
Is the gap the same on both sides?

I just had a similar gap on the left side ony that was corrected by placing the frame bow down on 2x4s at the left side and center, then stepping and bouncing in the middle. After several iterations, the gap is more consitant.
 
I was thinking of shimming, but using something like the JB Weld or epoxy approach. The rest of the canopy fits so well that to undertake the extreme bending of the top center, then the aft bow sides, and then whatever I would have to do to the side skirts just to make the aft canopy line up, makes me think of just farming the job out. As long as no one sees any problems with angling the roll bar aftwards, then I think that is what I will do. I will use shims initially then, when it all fits, use the JB Weld.

Thanks for all the suggestions.
 
Shim it!

Jeff, if the canopy frame lines up and all you have to do is shim the roll bar, do it. The frame is a piece of spagetti when you start bending on it and you can't really tell if the roll bar is 88 degrees or 90 degrees after you glass it in.

Just a suggestion on the 3/8 clearance at the top of the canopy frame. Don't cut the bottoms of the frame to final lenght until after you make the big cut on the canopy plexi. Be careful to really find the place where the canopy wants to sit. If it's "happy" you will have little or no gaps and virtually no shimming to do on the top of the roll bar or canopy. You will also have little or no stress from the canopy to distort the frame.

You can always trim the bottoms of the front canopy bow. The "purpose: of the 3/8 is so that the sloping canopy will match up with the windshield as it lays over the canopy frame. 3/8 might work or not for a good fit. Trim it carefully and keep the trimmed off rings. That way if you do happen to cut it a little low, you can cut/file a thin slice of one of the scrap ring cuts and make a nice flush spacer. ( don't ask :rolleyes: )

Bill S
7a finishing
 
Update

After working on the canopy some more, I am starting to learn better what it is I am supposed to be doing.....

The problem that I was seeing before was the gap between the roll bar and the front bow increased from about 1/8 at the bottom to 5/16" at the top. I thought that the canopy itself otherwise fit great and it appeared that the ideal solution was to shim the roll bar to make the gap even.

Well, in going back through the instructions again, I realized that the vertical distance of the bow bottom to the canopy deck was not the same (i.e. the horozontal bar of the frame was not parallel to the deck). I had already trimmed down the front part so that the top of the roll bar was a bit more than 3/8" below the top of the forward bow, and I determined I would need to cut down another 1/4" to make the bottom part parallel to the deck, which was not an option.

Soooo, I thought about it and decided that I could bend the upper part of the aft bow to raise the bottom of the aft bow to make the bottom parallel to the deck. I reasoned that if I did that, the bottom sides of the bow would elongate, and I would then have to bend the bottom part of the bow inward to compensate.

I just did the first set of bends and now have the bottom almost parallel to the deck. I made the bend several inches from the center on each side. I now need to do the lower, inward bend. I suppose that will raise the height a little more, which will be fine.

So, to those contemplating doing their frames, you really just have to dive in and start doing it. I worried for weeks about getting started and as other say, after you do it once, then you will know how to do it. Not that I have done it all yet, but at least I am starting to see the light.
 
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