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Screws vs Sika on Canopy

pilot28906

Well Known Member
I am working on the canopy on a 7 and have read a lot of good info about using Sika. I am sure there are proponents of using screws and would like to here from them.

How easy to get a crack? How does the screw method hold up long term? Difficulty with installation? Etc.

Thanks
 
After scrubbing this forum and numerous builder's logs, I've decided to go the Sika route, too.
 
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Screws

I went for screws and put heavy rubber tape between the canopy and the hoop. Some folks were doing adhesive + screws for insurance against the canopy somehow departing. thinking about that, if I put in screws anyhow, then why adhesive? One big caution, DO NOT use locktite on the screws, it will attack the canopy plastic. I found a different threadlocker that was safe to use.
 
I've done both

Sika looks better and probably lasts a lot longer, but very messy.

Fasteners are simple fast and easy, but have a history of cracking out


Tada!
 
Search thermal coefficient of expansion, Dan and others do a great write up of how the canopy wants to grow 10X more than the steel frame while in the sun, basically the canopy trying to tear its self off the screws, don't get me wrong, there are a lot of canopies out there with screws but mine is Sika!
 
Sika looks better and probably lasts a lot longer, but very messy.

Fasteners are simple fast and easy, but have a history of cracking out


Tada!

I went the sika route also. I'm not flying yet so I can't say the long term benefits but I can say there is a learning curve to working with sika. It's much easier than I thought to get a good fillet. A nitrile gloved finger with a little water or slightly soapy finger and a slow steady movement gave me good results.
 
Another vote for Sika. Our RV-6 canopy (riveted) cracked through a rivet hole after a high-altitude flight and corresponding large temperature swing. We have Sika on the RV-8 and it seems like a much more appropriate solution.

Good luck!

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i did both

I used Sika and screws because I didn't know which to use. It was way over kill, Sika alone is plenty strong and it looks better with no cracks. I used aluminum screws by the way to reduce weight
 
Sika

One of each. Screwed the first one on my RV-8 and lasted two years, then it cracked on me. Replaced with Sika. RV-6A was cut, fit and glued with Sika in a day. It is not messy if you tape off the unaffected areas. It absolutely baffles my why Vans recommends any other way.
 
I did screws and if I were to do it again, I'd do Sika.

I can't get the screws out now. Many of them are loose in the lame tapped rollbar... they're loose enough but the tap isn't stripped enough to be able to get them out .
 
I did both. Tipup canopy, front is Sika, rear is screws over baggage compartment. Have one crack emanating from one screw in rear, stop drilled. Have seen other aircraft screwed with crack emanating from same exact screw hole, identically stop drilled as mine is.
 
Silka turned out to be a lot easier than I ever expected. The thought of drilling all those holes in the canopy gave me chills. There's tons of step by step photo's and great tips right here on this site. Just do a little research and go for it.
Also the silka method just seem to be a more solid assembly. I think there are two kinds of pop riveted canopies, those that have cracked and those that will.
There is also a big variation in the price of Silkaflex with the best I have found at EMI Supply,inc on the Internet.
 
I did both. Tipup canopy, front is Sika, rear is screws over baggage compartment. Have one crack emanating from one screw in rear, stop drilled. Have seen other aircraft screwed with crack emanating from same exact screw hole, identically stop drilled as mine is.

Ruh roh. Which screw hole?
 
Sika - But Watch Out for Stress Points

-8A; 5+ years with 760+ hours. Used Sika - not a single rivet in the canopy structure - but still ended up with approximately 4 inch cracks in the area of the rear canopy frame cross brace - one on each side.

After going through my bad word inventory numerous times, I calmed down, applied logical analysis and realized I may have introduced stress points during the assembly process by using "excessive" (I have no idea what the actual difference between excessive and non-excessive might be) force in clamping the canopy to the frame in that area in order to conform with frame curvature. Perhaps judicial use of a heat gun would have made things right, but of course, I had no idea at the time that there would be a problem. Thought Sika elasticity would compensate.
 
I used Sika for the entire canopy on my RV-8, worked great, easy to use and install....however do not think that a Sika'ed canopy cannot crack. Mine cracked vertically at the aft cross over tube after I experienced some violent turbulence while cruising at 165 KIAS and the acft yawed about 20 degrees to the left. The whole right side of the canopy flexed inward, resulting in a stress crack right on top of the aft cross over tube. Not sure either method (rivets or Sika) would have prevented the crack.
 
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