Tip: RV-7A Sika Flex canopy attachment

rvtach · #1 01-15-2008, 01:47 PM

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

sglaeser · #2 01-15-2008, 02:30 PM

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.

dsmithlib · #3 01-16-2008, 08:58 PM

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

cjensen · #4 01-16-2008, 09:12 PM

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....py&redirect=no

lorne green · #5 01-17-2008, 12:59 AM

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.

rvtach · #6 01-17-2008, 05:05 AM

Quote:

Originally Posted by dsmithlib

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

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.

flion · #7 01-17-2008, 08:47 AM

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?

Jim Ellis · #8 01-17-2008, 05:50 PM

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.

tomcostanza · #9 01-17-2008, 06:13 PM

Hi Jim,

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

Best,

rvtach · #10 01-18-2008, 05:15 AM

Quote:

Originally Posted by tomcostanza

Hi Jim,

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

Best,

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.

Quote:

Originally Posted by flion

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?

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.