Tip-Up Canopy on RV-7A

[Hubitom1]

Hey everybody,

have one of those dumb questions again ... here it goes.

Has anyone out there in the flying world used ProSeal or SikaFlex in order to attach the bubble to the canopy frame? If so, were there any problems? Recommendations?

Thomas

[FresnoR]

Yup, just finished doing it with Sika.

It was surprisingly easy, there are quite a number of threads of people discussing it.

[Hubitom1]

Reason why I asked that question is that I talked to Scott from Sika, and he said he discourages the use of their products for different reasons (liability, off course, is one of them). But his main concern was that as soon there's some sort of stress on the plexi glass it would/could lead to cracks once primer is applied, especially when additional fastners (rivets, screws) are used.

Did you use Sika straight, or as an additional means in conjunction with the screws Vans uses?

Where did you get your stuff, and what type Sika did you use?

Tried the search function for Sika, but nothing came up. that's why I asked.

Thomas

[Sam Buchanan]

Originally Posted by Hubitom1

Tried the search function for Sika, but nothing came up. that's why I asked.

Thomas

I just poked the Search engine and had 235 threads returned when searching "sika".

[Hubitom1]

Yeah, after I posted I tried searching for Sika only. They showed up. Before I used a combination, and I didn't see anything. Guess I'm just looking like a dumb bottom right now!

Anyway, would love to hear from people that are actually flying right now. Any problems in the long run?

Thomas

[DGlaeser]

I used Sika only, there are no holes in my canopy. After 5 years of Michigan weather it is as solid as the day it was finished. As long as you glue within 2 hours of priming, it is stronger than the plexi.

[gasman]

Originally Posted by DGlaeser

I used Sika only, there are no holes in my canopy. After 5 years of Michigan weather it is as solid as the day it was finished. As long as you glue within 2 hours of priming, it is stronger than the plexi.

Any changes in the procedure over the past five years as far as spacing a gap between plexi and frame?
Has anyone glued it on without the spacing?

[lorne green]

No holes in my plexi, frame or side skirts. A gap IS nessesary for expansion and contraction, 2mm is what I used. So this means you have to fabricate your canopy frame width narrower than if you were drilling and bolting. I did lay up a sika coupon of plexi-primer-sika-primer-plexi, 2mm thick. I let it cure for four days, then tested it to failure. When it finally failed, the bond failed within the sika lay-up, just where I wanted to see it fail.

[FresnoR]

Originally Posted by lorne green

So this means you have to fabricate your canopy frame width narrower than if you were drilling and bolting.

I did not allow for the narrower canopy frame and the finished canopy did end up a few mm wider than the fuselage on each side. It was not horrible, but did look a little unsightly. Of course, ten minutes with a five-foot pipe clamp and a couple soft whacks with a mallet and I had an absolute perfect fit.

I also had no holes drilled into the plexi for main or rear. Sika is pretty easy to work with, but if it gets on your clothes, it is never coming out.

[DGlaeser]

Originally Posted by gasman

Any changes in the procedure over the past five years as far as spacing a gap between plexi and frame?
Has anyone glued it on without the spacing?

I modified my tip-up frame to allow for spacing (described in previous posts, if you do a search). A gap is needed to get a full strength joint. I have not heard of anyone going gapless, and would not recommend it.
My rear window has a minimal gap on the aft edges that lay against the inside of the fuselage skins (just sanded them down to get a gap), but the forward edge has a generous fillet, and I also glued it to the fore-aft channel (don't remember the part number), so it is not going anywhere