Tip: RV-7A Sika Flex canopy attachment

After several months of slow, on and off progress (interruptions due to work, and other commitments) I have finished the sliding canopy on my -7A. I am very happy with how it turned out... actually professional looking. The pros and cons of using Sika Flex adhesive to attach the canopy has been pretty thoroughly debated so this post is intended simply to document my experience. I'm not trying to change anyone's mind.

For anyone who wants to use the Sika Products for this, hopefully my experience will make that part of the RV homebuilding journey a little bit less uncertain. This method was not hard (although I have no basis for comaprison vis a vis Van's suggested method). I drilled exactly 1 hole in the plexi (for the latch handle) and I didn't need any shims between the frame and the bubble (the glue compensates for any irregularities) and I have no cracks (but that's not a surprise as I didn't drill any holes). I think the main benefits of going this route are that there is less risk of cracking and it looks really nice. I plan to use Sika Flex adhesive for the windscreen as well even substituting the glue for the fiberglass molding around the base of the windscreen. That will make it relatively easy to replace the windscreen if it is ever cracked by some traumatic event (bird strike etc). The adhesive sets into a rubber-like consistency which is easily cut with a razor blade. After working with this stuff and trying to pull apart some samples I made I am confident in the strength of the glued joints (how's that for scientific?)

I had posted an intermediate progress report a while back with a link to a PICASA web album. Now that the skirts are installed and the thing is done, here's that same link again but now there is aditional photos and text.

http://picasaweb.google.com/rvtach/GluingMySliderCanopy


Jim McChesney
RV-7A starting FWF and electrical

Good Job!!

Jim,

Your installation looks very clean and professional.

I also used Sika Flex for my tip-up and was very pleased with the results. I put a bead around the front of the canopy as you indicated but also backed it up with fiberglass. 200 hours (this weekend!!!) and the canopy is still stuck on.

One item worth mentioning, the Sika Flex does allow expansion and contraction. I carried my paint onto the canopy approximately 1/4". At the aluminum/plexi joint i'm getting cracking in the paint... A wider strip of black trim tape will hide my mistake, hopefully you can avoid that.

Jim,
How do you think Sika would work in a tipup configuration? I am getting to the attaching point of the tipup. Do you know anyone who did it? Yours looks great !
Dave

Dave,

Doesn't matter if it's TU or Slider...I have a TU, and will use the Sika products to attach my canopy as well.

This is a GREAT example/tutorial on how to do it, and it's a TU...

http://www.matronics.com/wiki/index.php?title=Gluing_Your_Canopy&redirect=no

Thanks, Jim

Very instructional!
I am planing as well to bond my T/U canopy with Sikaflex. You made it look easy!
(I know it isn't). I plan on leaving the minimum fillet thickness between frame and
conopy as per sika instructions. There are a few good sites that help take the mystery out
of this challenge; your site just helps further our knowlege.

dsmithlib said:

Jim,
How do you think Sika would work in a tipup configuration? I am getting to the attaching point of the tipup. Do you know anyone who did it? Yours looks great !
Dave

Click to expand...

I don't know what all the differences are between the tip up and the slider but I think Chad is right that Sika Flex can be used ith either. It's a matter of getting everything lined up and temporarily secured, then putting the glue in. Some of the guys who have glued applied the glue then put the pieces together (usually on the -8's) and that just seemes to me like a good chance to smear the glue around and make a mess. There may be a reason I don't know about why that works better on the -8 canopy.

It actually isn't hard: the difficulty is in deciding exactly how to do it the first time. Lots of time spent looking at it from all angles and several dry runs to make sure I had the exact sequence of tasks down just right.

The main thing I learned I doing this is that next time I wouldn't use spacers; the fillet joint provides the same strength as a 1/8" joint. This eliminates the second glue step of filling in the gap after the spacers are removed and would make it easier to get a smooth joint.

Glad this is of some use to folks.

I've seen in the tutorials that Sika can be sanded. Now that I've attached my canopy, I'd like to sand out that front fillet. Any tips on how? It looks less sandable than I hoped. Also, the tech sheet says to paint with poly-based paint. Are people painting their fillets or glassing over it and then painting?

Sanding Sikaflex

Sikaflex sands nicely with 120 grit open coat sandpaper. To shape the forward fairing wrap the sandpaper around a short piece of PVC pipe and sand away.

You can paint cured Sikaflex with either polyurethane paint or a water based enamel...try Borden's brand at Ace Hardware. Do not use a mineral spirit based paint because it reacts with the Sikaflex and will not dry. With very little work you can get a very nice looking fairing without using any fiberglass.

Rivets?

Hi Jim,

I can't tell from the photos, did you use pop rivets or solid rivets on the side skirts?

Best,

Rivets and sanding

tomcostanza said:

Hi Jim,

I can't tell from the photos, did you use pop rivets or solid rivets on the side skirts?

Best,

Click to expand...

I riveted the skirts to each other and to the frame as per plans using pop rivets to the frame (inside and out) and solid rivets to join the side skirts and the inner brace. Again, no rivets throught the plexi. Where the side skirts overlap the plexi I scuffed, cleaned, primed both surfaces and glued w/ the Sika Flex putting in a thin layer of adhesive to anchor the skirt to the plexi. What oozes out is easily removed after it cures. I made some samples of scraps from the canopy glued to aluminum w/ very thick and very thin layers of glue. Some of these samples have spent time in a 225 degrees oven then transferred to the freezer and the glue joints still seem strong (i.e. can't pull them apart with my fingers). That said, Sika Flex says you need some thickness in the glue to get a really strong joint.

flion said:

I've seen in the tutorials that Sika can be sanded. Now that I've attached my canopy, I'd like to sand out that front fillet. Any tips on how? It looks less sandable than I hoped. Also, the tech sheet says to paint with poly-based paint. Are people painting their fillets or glassing over it and then painting?

Click to expand...

I did some sanding of the fillets with the sand paper wrapped around an appropriately sized dowel to geta consistent radius. A finger tip would have worked too I suppose.

Sika and Tipup questions

I've read some of the writeups on the matronics site and other places. I'm still left with a few questions.

The Tipup is glued/attached to the canopy bow, but also rests unglued on the canopy frame.
How did you go about applying Sika across the full width of the canopy frame (seems you need this so there's a seal)?

Did you apply a mold release agent to the tipup plexi, then glue the forward half of the canopy frame with the tipup firmly in locked position? Then you remove the tipup and go through the process of gluing the rear half of the shell? (Or maybe do the rear canopy first, and come back and add the front seal as final step?)

Here is how we did it

You'll find a description of how we did it on: http://websites.expercraft.com/PHVII/index.php?q=log_entry&log_id=6287 and on the pages beyond.

All the best,

And here's what we did,
RV-7A tip-up, result looking great!

we did a few mods to the frame to prepare for the sikaflex:
and basically cou can finish the frame including the rear latches and weatherstripping before ever putting on / trimming the plexi as opposed to van's instructions where you'd wait e.g. with drilling the rear top center splice plate.

first, the "canopy stop" idea that has been floating around here is highly recommended, otherwise installing the gas struts will skew everything:


then we did some custom weatherstripping, which is awesome:



now to the actual mods on the frame:
- the siderails are mounted to the inside instead of the outside (plans) of the weldment, essentially resulting in an offset to the inside of .125". between the weldment and the bracket attaching the siderails are small spacers.




then there are 2 .063 strips with lightening holes clecoed to the siderails. on that the canopy will rest/can be clamped while the default top bend of the siderail will allow for a very nice bead on the inside of the canopy, giving enough sikaflex to hold on to. The sideskirts are later installed only with the rivets through the siderails and sikaflex between the canopy and the skirt, we have 0 holes in our plexi also the rear canopy frame rib was built slightly undersize to give the canopy a nice sikaflex bead while resting flush on the rollover bar. also, no need to wait with installing the canopy frame top skin as per van's. when you're at the point, just rivet it on before plexi work.



and the actual gluing:
http://www.flyvans.com/log/2008_04_03_sikaflex_canopy.html
http://www.flyvans.com/log/2008_04_10_sikaflex_canopy2.html

we made one mistake:
with the big cut, thought it was a good idea to move that away from the centerline of the rollover bar forward onto the flange of the forward rib. the idea being, that the rear canopy will have a stronger bond plus that ridge between the ribs where you can see the straps would be covered.
problem it turns out was, the forward canopy was now sitting flush while the rear canopy was "trumpeting" over the rollbar and the big cut didn't look good any more. we fixed it by trimming the rear canopy as well and filling the void with a solid sikaflex bead. that used about another cartridge but the end result looks good and we have a 0/0 sealed canopy

observations:
-get enough helpers
-anywhere where there's no sika primer, sikaflex won't stick and can be easily removed by rubbing it off. best done about a day after while it's still relatively soft. use that to your advantage.
- get good quality electrical tape that doesn't leave too much residue.
- the quality of the joint is awesome, sample pieces (with adverse conditions, no cleaning, no scuffing) had the plexi break before anything would let loose.
- also the tip with sanding the sika with 120grit works perfectly. just make sure you "plaster" enough sikaflex on so you can sand it down and aren't left with any voids.
- get enough sikaflex. most descriptions mentioned about 2 cartridges, we had to order more, certainly used 3 for the "regular" front and rear canopy and used a fourth (but that was used to cover our big cut building mistake)
one gets probably sanded away again when you shape the fairings ;-)

kind regards,
bernie

I'm partway through the process with my tip-up. I fitted the canopy without making 'the big cut'. I then glued the canopy to the front frame; it looks pretty much like the pictures in the previous post except I still have the rear section attached. Then the weather turned cold, so I've waited to finish. In the meantime, I've noticed that the Sika has hardened a great deal. My fillet around the front of the canopy worried me a bit but now I see that it's solid (like hard rubber).

My next step will be to glue the canopy to the roll bar. I've masked the outside of the canopy to mark the big cut and I've masked the inside so that Sika on the rollbar only sticks aft of the cut (and I've left a little room aft of the rollbar for a fillet). Because I didn't think the process through and drilled the aft-canopy-to-skin holes oversized already, I will have to be inside to cleco the skin on. So I will clean, paint, and apply Sika generously to the rollbar and then lower the canopy onto it. Then a helper will cleco the top skin on while I cleco the canopy to the skin and complete the aft fillet. I'll then spend the next couple of hours working on cockpit wiring runs and catching up on my reading until my helper comes back and we remove the skin. I'll have to crawl out aft of the baggage compartment. We'll then put the skin back on (reaching in and putting a few clecoes at the top of the canopy should be enough to hold it at that point). When the canopy has had a few days to cure, I will make the big cut. That should leave a shelf of Sika for the front canopy to rest on; I'll dress any damage I do to that making the cut buy applying some Sika by finger. I'll finish up the canopy by using a thin layer of Sika and riveting the side skirts and top skin on. Finally, I'll wax the aft canopy around the big cut and lay up a fiberglass strip to cover the joint.

Like I said, the bubble is already glued to the frame and it is *soliid*. I've had the frame up and down working on the latch, struts, and some clearance issues, and it doesn't give way at all. For those familiar with how twisty at tip-up canopy can be, especially before the struts are on, you'll understand when I say that I think that gives it more stress than I think flight loads will. My only concern will be sanding out that big fillet at the front; try as I might I could not get it perfectly smooth when forming it and there's a healthy edge at the masked lines.

Hard to see in the photo. How did you transition from the extra .063 on the side rails to the welded front canopy frame? Did these just taper or did you offset the side rails toward the inside (obviously requiring longer rivets)?

Thanks. Great that you posted this stuff for those of us considering sikaflex to see!

cheers,
greg

it's actually 2 strips of .63 (by the way, lent from another 7a kit, rollover bar strips) on each side for a total of about .125".

the intersection is achieved by simply making 2 spacers, .063 each and only half the width of the splice plate. going between the weldment and the siderail splice plate. longer rivets of course. the top "lid" is as per plans except for the lid now being on the outside.

here's another pic where you can kind of see the spacers.


also note the slightly different mounting of the lift struts. might be a result of the inboard offset of the siderails. actually more rigid as with the spacers per plans.



and another closeup of the weatherstripping



bernie

VERY helpful

This is a great thread ... thanks again to you brave souls who led the way. This is wonderfully instructive to those of us ready to start the canopy.

Ah, that weatherseal was the missing detail I'm still pondering on. I'm curious to see if others did something similar.

Since the rear canopy section floats on a 1/8" layer of glue at the roll bar, there should be a 1/8" gap where the front canopy comes down to the roll bar, not really touching the roll bar, right? I was wondering if folks left the gap, or installed some weather seal (d-channel or whatever), or maybe allowed a little sika build up on the front half of the rollbar for a seal.

dhall_polo said:

Ah, that weatherseal was the missing detail I'm still pondering on. I'm curious to see if others did something similar.

Since the rear canopy section floats on a 1/8" layer of glue at the roll bar, there should be a 1/8" gap where the front canopy comes down to the roll bar, not really touching the roll bar, right? I was wondering if folks left the gap, or installed some weather seal (d-channel or whatever), or maybe allowed a little sika build up on the front half of the rollbar for a seal.

Click to expand...

Don, did you ever get an answer to this question? This is what I'm hung up on too.

Did you reduce the width of your rollbar? My latest thinking is to move my side frames in by .25, and the aft canopy channels in by .125" to account for the Sika bond thickness (skirts are 2x), and just fasten the rear window instead of using Sika. This allows no mods to my stock rollbar and also does not make the canopy stick out past the fuse side skins as it would if I sika'd the rear window and matched the canopy to it. This way the canopy and the rear window both sit flush all around the rollbar. I already have a good spare window from the 1st canopy which was cracked by the previous builder I bought the project from. So if I cracked the rear window, it wouldn't be the end of the world...

Can anybody comment on this approach? Anybody else done it this way??

I tried letting the Sika flow forward to act as a seal under the canopy; I was not very happy with the results. You have no control over the forward edge and it looks pretty bad. I tried cleaning it up and filling but I'm still not happy. I'd say trim it flush with the aft canopy and install weather seal under the forward canopy. A targa strip over the canopy gap finishes the deal.

Ooops...

Yesterday, as I was clearing out my various email in boxes and my desktop I deleted my Google account. Never used it, never got anything in my Gmail account (not even any good spam!).

I was driving to the airport last night when I realized that the Picasa web album where I documented my slider canopy gluing had become part of Google and, well, now it's gone. If anyone who might have made a copy of the contents of that album could send me what they have I'll try to put something back together again and repost it. It doesn't matter if the photos aren't great quality as I have the originals. It's the text that will be most helpful. Maybe I'll re-post it on VAF then it's archived and I can't screw it up again.

My direct email is: [email protected].

Appreciate the help.

I really hope that someone saved it I just had it bookmarked but now it's gone. Perhaps there is someone out there that will turn up. It was very good and detailed.

yes it was

I used it a LOT when I started my gluing. I thought about saving the pics one day, but didn't. I just had it bookmarked. Sorry. You were a big help. Just finished my aft skirts. Glued them as well.

Not to worry...

Just got word this morning that one of our RV brethern has saved a copy of the whole Picasa slide show on his Picasa page (thanks Mike) and so now I just have to figure out how to do the same thing. I'll make a copy on my hard drive and a back up copy on a disc and save it to an on-line storage account so I don't lose it again. I'll post a new link here when I get it all done... probably later today.

Glad some folks found the pics helpful.

New link

Here's a new link to the Picasa Photo album that shows how I glued my canopy. Thanks for all the off-line help. I promise I won't do that again!

http://picasaweb.google.com/n622wr/GluingMySliderCanopy#

new link for my Sika Flex procedure

I've been away from the forum for quite a while but wanted to review my Sika Flex procedure and found that the Picasa link is now a dead end. Here is a new link in case anyone might find it helpful. Just about ready to glue the windscreen so I'll try to get that step-by-step posted here soon.

https://drive.google.com/file/d/0B37PxBNZlHKsVHg1b2IxM0Ywelk/view?usp=sharing

This link is to a PDF that should be downloadable in case that is helpful. Please PM me if there are any problems with this link.