Canopy fit problems explained (partly)
After fitting my canopy, and helping others fit theirs, I've seen two cases:
a) everything fits reasonably well.
b) nothing fits well.
I had a theory that even though there were manufacturing variances on the frame, that some or most of the error could be in the fuselage construction.
Evidence supporting this is that some of us had large 'fish-mouths' on the back of the side slider rails, had to cut and weld the canopy frames or trim the fuselage skins (or all three).
Today, I saw a canopy frame with an almost perfect fit, and no fishmouth at all on the slider rails (and not even any bevelling required). The builder, however, complained that he had to bend the roll bar in by 3/8" and remarked how difficult this was.
We measured the fuselage at two points... one at the seatback brace, and the other at the roll-bar attachment point. The aft measurement was spot-on at both points, but his width at the roll-bar point was... 3/8" narrower than on my fuselage!
All of his skins fit fine, his panel blank was installed, and his canopy frame fit well.
Now, my fuse was a QB, and his was a kit-build. When I received my fuse, there was a brace across the fuse near the roll-bar attachment point.
Looking at my friends fuse, I could see how it would be possible to build it with this point narrower... there is no support during construction that establishes this dimension.
If this dimension varies, then the whole canopy fit will vary. This is a large variance that's impossible to correct for with any amount of bending and twisting.
Based on this evidence, I suspect that this is the root cause of many canopy construction woes. I'll contact Van's to determine what the correct width is at the roll bar attachment point, and post it to the list.
Vern Little
9A
|
Linear Mode
