So, has anyone used Sikaflex on a 12?

My new canopy parts will be here Friday. When repairing the plexi I found a broken weld on the frame, and decided I was fighting a losing battle trying to fix it. I'm building a complete new canopy. I like the Sika idea better than screws & rivets, but haven't yet figured out how it would be done on a 12. I'm still researching.

I've seen some discussion about Sika on a 12, but never any final word on whether it's actually been done or not. Has anyone done it?

Dale,

Maybe it's not practical in your situation, but why not get the frame crack tig welded?

Rich

I could... but I'd have to replace the canopy anyway, re-do all of the fiberglass, and spend a lot of time cleaning up the old frame to re-do it all. Then I'd have to drill all the canopy holes and try to make them match the holes in the frame. And hope whoever did the welding had the frame jigged straight. In the end, the added cost of the frame ($325, compared to the $1100 plus crating and exorbitant shipping I was already in for) to not have to screw around trying to salvage the frame. It wasn't just a crack; the right lower end of the bow was completely broken off of the lower rail. I've got a couple of temporary reinforcing plate riveted in there until I get the new one built.

And, this way I can maybe put the old canopy back on and fly while I'm doing the finishing work.

DaleB said:

... It wasn't just a crack; the right lower end of the bow was completely broken off of the lower rail. I've got a couple of temporary reinforcing plate riveted in there until I get the new one built.

And, this way I can maybe put the old canopy back on and fly while I'm doing the finishing work.

Click to expand...

Dale, could you provide a picture of the damaged frame? It would help making a thorough inspection of ours. This kind of damage is somewhat surprising as I understand you bought the plane recently and probably have had the plane inspected before purchasing it.

You wouldn't see this kind of damage unless it had happened due to a pretty severe impact. You are, I believe, familiar with the plane in question. Based on the damage to that corner of the canopy and the F-1254 support frame underneath it, my guess is that the wind caught it and slammed it shut at some point, and it came down crooked. There's a dent where the tab on the bottom of the canopy missed the slot and impacted the support rail, the acrylic in the corner was broken and the skirt was not too pretty there.

We saw the external canopy damage during the pre-buy inspection, of course. It was a little ugly but limited in scope. Aside from the broken corner of the acrylic, which could be fixed with the right adhesive and a little careful work, it didn't look like a big deal. The broken weld was not obvious. It was only when I started taking apart the patches and previous attempts to fix the acrylic that I found the broken weld. The end of the canopy bow is completely separated from the side of the canopy frame. In hindsight I could have found it with a more thorough inspection of the weld from inside the plane, but honestly it never even occurred to any of us.

I think the takeaway here is, if the wind slams the canopy violently shut and breaks the acrylic, you might want to also check the welds.

Thanks for the pictures, Dale, very helpful to pinpoint the area of damage. As far as I remember, the previous owner mentioned that the canopy had dropped and damaged the Plexiglas but I was not aware of a broken weld. Your explanation of how it happened makes perfect sense but I doubt that the weld would have broken if it had no defect. It was probably neither the first canopy drop nor the last. If they all resulted in what you experienced we would have heard of it on this forum.
By the way, I had the same adventure at the same airport, KGEV, due to the blast of a Cessna Citation which turned in front of my plane for refueling while I was tying down the plane with the canopy up. Luckily I had limited damage because the handle of the canopy was in the closed position (In hot weather I always taxi with the canopy cracked open and the handle stays in the closed position when the canopy goes up). The handle took the brunt of the shock and got bent but it also absorbed the energy of the fall and prevented the tab to hit the rail at the bottom. For this reason I now always make sure the handle is in the closed position whenever the canopy is open.
Good luck for your repair!

Well, I'm a fair amount into the new canopy build. I've decided I'm definitely using Sikaflex, and have the materials on the way.

I'm having trouble believing how easy this is. The canopy frame was a near perfect fit right out of the box. I spent maybe a couple of hours getting it tweaked to line up perfectly, and doing some careful filing of excess material off of a few welds. The canopy itself dropped into place with zero trimming, and even the hole for the handle was already drilled. It appears to have a light tint to it, though I haven't compared it to the old one side by side yet.

Last night I fluted the C-1203 attach angles, it was easier than I thought to get them matched perfectly to the frame side rails. If I get good enough weather to shoot primer and paint it should be ready for Sika this weekend - though we'll be gone for a funeral, so it will have to wait a bit longer.

The skirts have prepunched holes for the screws I won't be using. I don't really feel like cutting new skirts, but maybe I should. I'm thinking I'll let the Sika fill the holes, and use a razor to shave it flush before painting. I don't know that I'll be able to get it completely invisible after painting, but it won't be as noticeable as screw heads. I don't want the paint cracking though.

The new rear canopy seal uses an aluminum strip (C-1221) that's supposed to slide under the nuts on the screws that won't be there. The old canopy didn't have anything there. I haven't decided for sure what to do about that. I could possibly use flush rivets to attach a strip for the seal... will evaluate that tonight when I put the frame back on the airplane for some final drilling.