There comes a day in every RV builder?s life when he or she has to trim the canopy to fit. This has long been one of the big hairy Bogeymen of the kitbuilding world, and quite frankly, doesn?t really live up to it?s advance billing. With care and preparation, getting the canopy to fit on the airplane is just another task that you have to do along the way ? no more, no less.
Now I must admit, the RV-3 is much easier than the RV-8 ? for one thing, you don?t have to make the ?big cut? (separating the windshield form the canopy) because it is a flip-over rather than a slider. And second, the whole is much smaller, which makes it easy to handle, even for one person. That made it far simpler to flip it on and off the fuselage and frame to make multiple trims. The other thing nice about not making the ?Big Cut? is that you essentially fit it ?once? to the hoop part of the frame, rather than having to make it fit the frame and the roil bar (as in the -8), a multi-dimensional problem that can drive you nuts (until you realize the fit changes after the cut, and fixes all previous sins?).
Our RV-3 kit came from another builder who ordered all the sub-kits, but bought a ?tall-man?s canopy from Todd?s, rather than the stock Plexiglas that comes from Van?s. This is a bit thicker than stock, and also comes with the flange removed ? a head start in the trimming process. Still, with the bottom essentially ?flat?, you have to make an informed guess as to how to make the first trims front and back to get it to settle down around the curve of the fuselage. Or, you have to have an ?Aha!? moment?.like the fact that the canopy gets trimmed to the bottom of the ?hoop? on the frame, and if the hoop is formed to fit the fuselage before you get started on the plex, you can set the canopy over the frame ? with the frame on the work table ? and get a good approximation of the cut the first time! That is what we did, and it worked really well for the front ? the rear took a few iterations because the two aft parts of the frame ?hoop aren?t joined, but just sort of flop around, and so they don?t really represent the shape of the fuselage properly. SO here we go:
We started with the frame ?hoop? shaped to fit the fuselage. We then put the raw bubble upside-down on the table (on padding), set the frame inside, and traced the outline of the hoop on the bubble with a grease pencil.
Allowing a generous tolerance for errors, we then used the cut-off wheel to make the first major cut.
First fit worked out very well for the front (we didn?t really trim it again until we were polishing the edges), but we had to sneak up on the rear a bit to get the canopy to settle down with the edges just below the hoop. For this kind of trimming, a 2? sanding disk on the right angle die grinder was outstanding ? you can carve the plexi aggressively but under complete control. It probably took only a minute or two of grinding to take a quarter inch off each time. Total trimming to fit too about a half hour.
Once we were happy with the fit, we drilled the canopy to the frame for clecoes. While we haven t? decided for sure if we?re using rivets or Sika for the final attachment, it is very handy to have it firmly held with Clecos during construction. Initial holes drilled with a #40, Plexi holes then opened up with a #27 Plexi drill, and holes in the frame opened up to #30 for -4 Clecos.
Of note is the fact that Louise did a large part of the cutting, trimming and polishing of the canopy edges, as well as the majority (I think I drilled two holes) of the drilling to the frame. Yup ? she has made the ?Rite of Passage? required of all homebuilders in making a canopy work?.
The canopy fit very well in a very short time, and I am happy enough with that to be at peace with our decision to go with a tip-over on this bird?.
Paul
Now I must admit, the RV-3 is much easier than the RV-8 ? for one thing, you don?t have to make the ?big cut? (separating the windshield form the canopy) because it is a flip-over rather than a slider. And second, the whole is much smaller, which makes it easy to handle, even for one person. That made it far simpler to flip it on and off the fuselage and frame to make multiple trims. The other thing nice about not making the ?Big Cut? is that you essentially fit it ?once? to the hoop part of the frame, rather than having to make it fit the frame and the roil bar (as in the -8), a multi-dimensional problem that can drive you nuts (until you realize the fit changes after the cut, and fixes all previous sins?).
Our RV-3 kit came from another builder who ordered all the sub-kits, but bought a ?tall-man?s canopy from Todd?s, rather than the stock Plexiglas that comes from Van?s. This is a bit thicker than stock, and also comes with the flange removed ? a head start in the trimming process. Still, with the bottom essentially ?flat?, you have to make an informed guess as to how to make the first trims front and back to get it to settle down around the curve of the fuselage. Or, you have to have an ?Aha!? moment?.like the fact that the canopy gets trimmed to the bottom of the ?hoop? on the frame, and if the hoop is formed to fit the fuselage before you get started on the plex, you can set the canopy over the frame ? with the frame on the work table ? and get a good approximation of the cut the first time! That is what we did, and it worked really well for the front ? the rear took a few iterations because the two aft parts of the frame ?hoop aren?t joined, but just sort of flop around, and so they don?t really represent the shape of the fuselage properly. SO here we go:
We started with the frame ?hoop? shaped to fit the fuselage. We then put the raw bubble upside-down on the table (on padding), set the frame inside, and traced the outline of the hoop on the bubble with a grease pencil.
Allowing a generous tolerance for errors, we then used the cut-off wheel to make the first major cut.
First fit worked out very well for the front (we didn?t really trim it again until we were polishing the edges), but we had to sneak up on the rear a bit to get the canopy to settle down with the edges just below the hoop. For this kind of trimming, a 2? sanding disk on the right angle die grinder was outstanding ? you can carve the plexi aggressively but under complete control. It probably took only a minute or two of grinding to take a quarter inch off each time. Total trimming to fit too about a half hour.
Once we were happy with the fit, we drilled the canopy to the frame for clecoes. While we haven t? decided for sure if we?re using rivets or Sika for the final attachment, it is very handy to have it firmly held with Clecos during construction. Initial holes drilled with a #40, Plexi holes then opened up with a #27 Plexi drill, and holes in the frame opened up to #30 for -4 Clecos.
Of note is the fact that Louise did a large part of the cutting, trimming and polishing of the canopy edges, as well as the majority (I think I drilled two holes) of the drilling to the frame. Yup ? she has made the ?Rite of Passage? required of all homebuilders in making a canopy work?.
The canopy fit very well in a very short time, and I am happy enough with that to be at peace with our decision to go with a tip-over on this bird?.
Paul
