Gluing your
Canopy by Billy Waters
Gluing your
Canopy by Billy WatersWhen I acquired my latest project back the first of the year, one of the tasks I’ve dreaded the most is installing the canopy. After all, I did make the $1000.00 mistake on my –6A. It was a few months after that I read the article in one of the magazines describing how Chalkie Stodard had installed his canopy with a urethane adhesive, without drilling any holes. Needles to say, this intrigued me very much, since I was trying to finish this plane on a budget, a budget that did not allow me the luxury of buying another canopy!
When the time finally arrived to begin the dreaded canopy install, I sent an email to Chalkie to see how his canopy installation was holding up. His reply was 300 hours, no worries, would never rivet a canopy on again! Well, that did it for me. A little Internet research and I had my canopy glue!
To cut the canopy, I pretty much followed Van’s instructions. I cut the sides on the factory marks, leaving a little extra front and rear. (Sorry, no pictures of the cutting process) When I positioned the plexi on the frame, I was about 1 ½” to 2” above the roll bar and front canopy frame bow. I resisted the temptation to slice off about the same amount, and started out making about ½” cuts on the front only. After each cut, I would stand back and study the situation very closely.
After about four cuts it started coming into position. It finally reached the point I had to make half moon cutouts for the canopy latch tube. When doing this, be sure to heed Van’s advice and take the time to smooth up these cuts. It’s getting close, wouldn’t want it screw up now! After several hours of cutting and studying, the canopy finally seemed to just settle into position. At this point, I made a mark using the canopy framework as a guide, and made a final cut all the way around. This is the first time I cut the rear of the canopy since I made the initial cut. Time to stand back, admire your work, and, if so inclined, have a beer!!
This whole cutting process took somewhere between four to six hours. Remember, I did a lot of studying! The next day, I took the canopy off the frame and polished the cut edges. Notice I have not made the big cut. When gluing the canopy, it is put on as one piece. This is a big plus as once installed, you will not put any stress on the plexi. Once polished, we’re ready for the glue!
The material I used is Sika 295UV. You can find tech info and instructions for plexi installation on Sika’s website, I downloaded the installation instructions and followed them to the letter. It’s really a pretty simple process, one that leaves you thinking, "Is that all there is too it?” Since I did follow their instructions, I won’t go into too much detail here. Install manual and specs here.
I will pass on a few tips though. The plexi must be primed before you glue it to the frame. Put the canopy on the frame then, using masking tape on the outside, mark the areas that will come in contact with the adhesive. Once all areas are marked, take off the canopy and, using the tape as a guide, tape off the interior. Doing it this way, you can minimize the area you have to sand and prime. Make sure to leave the inside tape in place, as it will keep the adhesive where it belongs.
Once prepped, I applied the glue to the canopy frame, and recruited some help to set it in place. If you have areas with a large gap between the plexi and the frame, be sure to apply enough material to fill the gap. Because of the shape of the –8 canopy, once it was in place, it held itself without the need for any clamps. I’m not sure this would be the case for the side by side canopies. If you do apply clamps, I’d use only enough pressure to hold it in place. You don’t want to squeeze out all the material. The instructions actually call for spacers to allow a gap between the pieces. I checked it after about 2 hours and I believe you’d have been hard pressed to get it off, even at this point! At this point, I was thinking something’s wrong, this has been too easy!
After letting it cure overnight, it was time to separate the windscreen and slider. I had put one wide band of primer between the frame and roll bar, so I couldn’t see the gap to make my cut. I took a screw and using it to make a mark in the primer, reached underneath the canopy and lightly scribed the primer between the frame and roll bar. I then applied masking tape to the outside, then, very carefully, made the cut. I now had a separate slider and windscreen attached to the plane and I didn’t drill a single hole in the plexi! Really cool, and believe me, this process was much easier and a whole lot less stressful than the drilling method. In all you’re excitement, don’t forget to dress the edges of the big cut. At this point, you can remove the canopy, the, using the glue, apply some nice fillets wherever necessary. Once all this is done and set, remove all the tape from inside the canopy. I had to use a razor knife in a few spots to get a nice edge.
Next came the skirts. A lot of folks have trouble getting these things to fit well, but I guess I was lucky. Use duct tape to hold the skirts in position, then make your cut marks. Same as the canopy, I made several cuts to get the fit and coverage I wanted. Once I had the fit I was looking for, I secured them to the frame using clecoes in about 4 places.
Here’s where I ventured a little into new territory. Once secured into position, I reached in from the opposite side and marked the frame tube locations. After marking both sides, I removed them, prepped the areas between the marks, and then applied the same adhesive I used on the canopy. Using a combination of the clecoes and duct tape, I secured both sides in placed, and left them for the night. You can see the results in the pictures.
I am very pleased with the results I obtained using this method. It is, however, very different than attaching the canopy with rivets. It is a lot easier, but it is also a lot messier. Before I paint the canopy skirts and frame, I will have to spend a little extra time using some seam sealer to make all the glue joints at the tubes look nice. Too some, fooling with the glue may not be worth the mess. Would I do it again? You Bet! After drilling the holes thru the skirt into the canopy frame for the clecoes, I was thankful I didn’t have to do the same thru the plexi.
Hopefully, I have posted enough pictures to help you make a decision. They can be found here: Look under Super 8, interesting. And while your there, you can check out Mike’s progress on his Super 8. Thanks to Mike Stewart for posting them.
Good luck whichever way you decide to go!
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