I?ve just now managed to get through installing the skirts on my -7 sliding canopy. As a starter, I recommend Orndorff?s video for some good ideas. But he doesn?t show how to make the frame fit and I?m now convinced that the initial frame fit is the most important step in the process.
I had virtually no problem with the roll bar. I was able to tweak the canopy frame to get a good match between the forward canopy frame bow and the roll bar and I even managed to get the side bows to be where they needed to be relative to the fuselage. As stated earlier, it?s a very good idea to believe Van?s instructions about the position of the frame and roll bar relative to the cockpit/turtledeck.
Problem was, however, the rear bow kept messing up everything. I fooled with it endlessly to make it work with no success. I postponed installing the canopy and from time to time over months (years) would try again.
In the 90?s I built a Pitts including cutting/welding the 4130 tubing for the fuselage from scratch so I slapped my forehead and said to myself what am I waiting for? I finally got fed up and cut the rear bows off. I installed the pin mounts and caused the side bows to be where I wanted them to be. I taped 3/8? dowel rods extending forward around the turtle deck to get reference points and bent ?? x .035 4130 to fit within a 1/16? or so under the extended dowel rods. I used a borrowed tubing bender to curve the 4130 tube to avoid collapsing the tubing (you can safely make a small radius bend by hand or using a template in 3/8? 4130, but ?? 4130 tends to kink).
Worked just fine. That took me one Saturday morning but I?ve tig welded quite a bit of 4130 thin wall tubing over the years and I was able to borrow the tube bender.
Once this was done, I cut and drilled the canopy per Orndorff in a day and had the windshield trimmed and drilled in place another day. Be sure your rollers are free to rotate - this is explained in the Orndorff video. After drilling and clecoing the canopy to the frame I had to squeeze the frame in a little since the Plexiglas spreads it when attached. Fit it so that the the canopy can move fore and aft freely in the slide tracks. Later on I found out that something had moved somewhere because when I installed the right side skirt and skirt brace (C-791), it became clear that I had to take the frame off and take some of the curve out of the side bow. Fortunately, that made the right side skirt snug up against the fuselage side nicely without skewing dimensions elsewhere.
Fitting the side skirts wasn?t much trouble except for the right side bow discussed above. Be sure to trim the forward lower notch in the side skirt before you try sliding the canopy so you won?t scratch your canopy deck paint. Follow Orndorff on this part.
Like most builders, I dreaded the rear skirt installation just from hearing all the misery. But if the frame is where it should be, and the canopy is in place where it should be, then they?re not too difficult. The trick that worked for me was to cut the sheet metal oversize and then run the skirt through a slip roller at an angle (again, the slip roller was a borrowed tool). Nothing precise: maybe 45 degrees and feed the lower end of the skirt in first. Make opposing skirts, of course. The rollers don?t have to be too tight ? you don?t want a small radius - you can eyeball this to pretty closely match the turtledeck curve. Stop and back the skirt out of the slip roller about 12-15 inches from the top end since this end doesn?t need to be curved. If you keep going, you?ll make the skirt look like a curly-fry at Arby?s and the back edge won?t lay down on the top of the turtle deck.
When you lay the roller-formed skirt down across the gap, you'll be surprised that you have a pretty nice fit.
Orndorff says to use ?keeper? rivets in between the pop rivet holes in the rear bow to hold the canopy in place while fitting the skirt which is a good idea, but I think that limits your options to disassemble and paint later on. I used good quality masking tape instead around the entire perimeter to hold the canopy on the frame while I drilled the skirt in place following Orndorff?s measure-to-the-hole technique. I also propped the canopy open at the front, but I didn?t put spacers under the pin blocks like Orndorff suggests. I might do it that way if I had it to do all over again.
As suggested everywhere, pull pretty hard on the lower front edge of the rear skirt to make it lay down flush to the turtle deck while drilling ? use this ?pull? technique for each and every hole after clecoing the first 3 or 4 holes out from the center of the canopy frame at the top. Once I got down to the rivets attaching the side and rear skirts together, I adapted the rivet pattern to suit the installation which is not per the plans. I also cut a notch about ?? x 4? in the lower rear part of the side skirt and used the slip roller to curve the lower rear of the side skirt inward over the canopy deck before drilling the skirts together to help keep the side/rear skirt junction snug up to the fuse/turtledeck junction; this notch is covered by the lower part of the rear skirt. But that didn?t work perfectly either ? I still had to apply the shrinker in a few places including the usual place at the lower back side of the rear skirts so they?d lay down on the side of the turtle deck as it curves away from the fuselage.
I said the process was not too bad but I made two right rear skirts and three on the left; I also had to make 3 side skirts in total. It took me that much trial and error to catch on to the geometry of it.
Recap: Review Orndorff, make the frame fit as per Van?s even if you have to cut it and weld it, run the rear skirts through a slip roller, be prepared to buy and cut more sheet aluminum than you?d like to, and be prepared to learn to use a shrinker.
And tools, as always, can solve problems. Most builders haven?t spent $2k + on a tig welder (mine was an ancient P&H 300 amp Frankenstein machine), or have access to slip rollers, shrinkers, and tubing benders. I?d make new friends and try to reciprocate when possible. I weld stuff for friends from time to time and they let me use their shears and slip rollers and tubing benders.
As far as the windshield? Fiberglass. I thought seriously about making it in aluminum, but overall, it looks like glass is the best way to do it.
Good luck.
