Cozy
Chapter 18 - Canopy
Cutting the Canopy
I talked with Jeff at Airplane Plastics about the canopy bubble. Jeff says that the 2515 light tint allows 70% light transmission and is the maximum tint allowed by the FAA for certified airplanes. It seems, however, that most Cozy builders order the 2514 medium tint. Others have said that the medium tint is just fine for night flying, so that's what I ordered. The canopies are NOT cheap. A few months later, a local Cozy IV builder, Todd Silver, visited my project. Frustrated by the high prices he has invested in the equipment and learning curve needed to blow canopies. He "just happened" to have one in the back of his van. It looked good to me, but my Airplane Plastics unit was already fitted by then. Todd told me that he can produce optically perfect canopies and rear window sets for MUCH less than the price we've all been paying.
Todd's number is 954-579-0874, email BSILVER05@aol.com
Once the firewall was cured I test fitted the turtleback and canopy. Using a cut off blade in the dremel I trimmed away about 1.5 inches of acrylic around the shoulder support and the instrument panel until I had the canopy sitting down on the TB all the way around. What puzzelled me was that the BL0 template was about an inch out. The plans say to be sure you use the 4.0 inch size for F28 while drawing M4, way back in Chap 4, gave me a choice to keep the F28 bulkhead at 3.3 inches. I'd opted for a lower nose and used 3.3. I called Nat. It seems that, as I'd guessed, BL0 was designed with a 4.0 inch F28. This is why my BL0 doesnt fit. Nat suggested that I increase the height of F28 for a rounded nose. Another question I had was the angle of the canopy. My TB is at 90 degrees to the longerons. The matching cut on the canopy is more like 100 degrees, so the canopy overlaps the groove at the top by 1/2 inch. It's tempting to cut away more at the IP to get the edges lined up at the back, but I'm getting awfully close to the switch panel. Nat's thoughts on this were that the canopy is blown rather than draped [for improved optics] and is therefore oval. He suggested I trim the aft top to get a good fit. Next came a discussion on lifting the TB to get rid of the "dip" at the top. I've read archives and web sites which talk about "getting rid of the dip" at the top by raising the foreward end of the canopy 1 inch or more. This approach is also used by tall pilots to get a little more headroom. Wayne Hicks lifted his TB about an inch, but then again - Wayne's not exactly the best guy to follow when it comes to chaper 18, if you know what I mean.
I lifted the canopy with foam blocks and yes, the dip goes away when you get about 1 inch high. The problem for me is twofold. This lifts the WL of the forward end of the back windows, thus making the sweep along the bottom of the windows climb as it reaches the canopy. To keep a good line between the canopy and the rear windows I'd have to raise the tape on the canopy a couple of inches. Being fairly small (5' 7") I don't want to loose that much visibility. Even then, I'm not sure I could get a smooth curve from back to front. I sat inside with the canopy on. There's plenty of room inside and the canopy is nowhere near my head when in plans position. Having to fill a one inch tapering gap between the TB and the longerons with pour foam doesn't seem right to me. Finally, I've decided [persuaded myself] that I rather like the "eyebrow" at the top of the canopy. I think it's distinctive and breaks up of the straight line join. So, after much measuring and test fitting I decided that the best course here was to ignore all the well meant advice from numerous other builders and follow plans. I'll come back to this spot later and let you know if I regretted this decision.
Juliet gets an inside!
Did I mention that "the plane" now has a name? My reserved registration is N386JS, so "Six Juliet Sierra" will become common usage for me. Julia is the name of my eldest daughter, and, being British, I'm fond of a little shakespeare - so Juliet it is.
I've already done the fuel vent lines and they've been flopping around at the back of the plane because I didn't have anything to attach them to. I gently bent the vent lines so they went inside the TB, circled the top of the firewall and came back out at the bottom where the other one went in. I cut two small grooves in the lower aft side of the TB to let the tubes pass, being careful to keep them out of the way of the future engine mount reinforcements. They go through the triangle area which is later filled with urathane foam. (later Note: the vent pipes were in the way of the engie moount reinforcements. I had to bend them out of the way. In doing so I fractured one of them. Repair was easy with a brake line fitting.) I had to sand away some of my finishing micro on the edges of the TB, strakes and fuselage for a good glass / glass bond with later BID tapes. This only took a half hour, so I'm not sorry that I did a lot of the finishing early. At last, on May 12, I floxed the TB in position. I used a few small nails to hold the TB to the right curvature, but found that it tended to "pop out" a bit on one side. Here, I used drywall screws to secure a clamp which squeezed the TB into place. I ended up with a small ridge, about 1/16 inch, all around where the TB is slightly larger than the firewall. Flox fills the angle nicely. No big deal. I climbed inside the TB and cleaned up the flox joins. Then it occured to me... I was INSIDE the plane for the first time!
Reading ahead in the plans I saw notes that said "you'll have to leave this step until later, when you have access to the inside". Had I missed the step where you attach the canopy? No, this is done later. Hmmm. Why don't you have access to the inside at this stage? Then it dawned on me - You can't climb through a plans TB1 bulkhead! I'd climbed in and out of the back of a couple of times by then. You have to be fairly supple, but it can be done. I can imagine Charrie diving head first into the back to get the sandwiches during a long flight.
Fitting the canopy
I trimmed an inch or so off the bottom of the canopy glass to get it 1/4 inch above the longerons, then sanded the edges smooth to reduce possible stress points. I had been worried about cracking my canopy, but trimming it was really not a problem. In all I went through about 25 cut off wheels trimming the acrylic. I liked the very thin ones, even though they tend to break up if you get the cutting angle wrong for half a second, they seem to have less impact on the material. I managed to keep out of the line of fire most of the time. I only got hit in the face by two of them.
Once the canopy was trimmed and I'd roughed up the edges I prepared to flox it in place. I used the plans method of bondoing boards to the TB, but I used a total of eight of these to hold the glass in place evenly. Now for the single strip of UNI around the canopy - hmmm. Where are my trusty $5 scissors? Answer - in the back seat! I found my old scissors (the $35 ones from Wicks), cleaned the epoxy off them, and cut one long strip of UNI. Plans say to butt the selvege edge up against the tape. Does that mean the edge of the selvege edge? I decided it meant the edge of the UNI and epoxied the stip in place working my way from back to front. When it came to turning the corner at the front the UNI wouldn't [read couldn't] lay flat, so I cut it and overlapped. As the epoxy was curing I used a razor blade to try and keep the selvege threads off the tape. Didn't work very well, but I'm hoping I'll be able to trim this up easily when I remove the tape. I 3 BID taped the aft edge of the canopy using flox to fill any gaps first.
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