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RV-14 Canopy attach with Sikaflex

KeithB

Well Known Member
I have reached the stage in the Finishing Kit for mounting of the canopy plexiglass onto the canopy frame. After considerable research, I have decided to deviate from Van's plans and mount my 14 canopy (and rear window) using Sikaflex adhesive rather than screws and nuts.

I have:
- reviewed two excellent blogs by Bruce Swayze (RV-7A) and Bruce Hill (RV-9A) on their successful installations (big thanks to these guys for their thorough documentation and efforts at sharing)
- reviewed the manufacturer's instructions
- spoken to 3 builders who used Sikaflex and inspected their planes (RV-6, RV-7, RV-8).

I can see no barriers on the 14 plans/design to prevent using the above techniques, and I see major advantages and few drawbacks (other than you have to develop your own instructions since Van's plans don't lead you through the steps).

Yet ... I have not seen/heard any discussion on the RV-14 forum of Sikaflex canopy installations, suggesting that others have not found this route advantageous. Or is there a hidden problem out there that I'm missing? Or are there horror stories that I haven't come across that might dissuade me?

Or maybe there just aren't that many RV-14s at this stage yet.

Anybody with thoughts or comments before I charge ahead (well, actually it will be very methodical, not charging).
 
Having done a 7 and an 8 with Sikaflex, I think it is a no brainer.

Why drill holes when you don't need to.

Glass aeroplanes have their screens glued on, the 10 has part glued on, it is straight forward, neater and less stressful both on you as you do it and the canopy when attached.

We start our 14 soon and will be gluing the canopy on.
 
Prepunched holes?

Probably a minor detail but assuming the holes for the screws that hold the canopy to the frame and turtle deck area are prepunched, you'd have to fill them in. Should be able to do that with some micro and then touch it up with sandpaper so it doesn't show after painting.

I've seen a lot of cracked canopies over the years, so I may consider using Sikaflex myself.
 
For future builders who stumble on this thread, I have found one problem (not a road block yet) with a Sikaflex install - the gap seal between the canopy frame and the roll bar is held in place using the screws for attaching the canopy. With no canopy attach screws there is no (easy) way to attach the seal as supplied. I'm working on the solution ...
 
I've seen a lot of cracked canopies over the years, so I may consider using Sikaflex myself.

In the interest of full disclosure for builders seeking out information in the future....
A bonded on (Sikaflex) canopy installation does not assure a crack in a canopy will not occur. There are instances posted here in the forums.
 
Totally agree Scott, we have heard of some cracked Sika'd canopies, however I think we have heard of many more due to drilling.

I understand why the conservative way is to follow process and drill the canopy, however as build experience progresses and evolves, it was inevitable that folks would start to bond canopies on.

It involves more work, more time, more care, but the result I feel is much better. This leaves us with the dilemma, which is better - probably both a s good as each other with different threats and opportunities.

It is what homebuilding is about I guess and why we like to experiment and adapt.

Interesting post regarding the support parts, we haven't started our 14 yet, so will probably revisit this thread much later.

Now......

How about gluing an RV12 canopy on :D:D
 
Totally agree Scott, we have heard of some cracked Sika'd canopies, however I think we have heard of many more due to drilling.

I wasn't arguing for or against, and totally agree with your point about it being experimental.

But, because it is, lots of novice builders take info posted here in the forums in the sense of absolute (in my opinion a lot of it is far from it) and presume they need to make modifications or deviate from the plans just because someone else has.

If we are honest, a bonded on canopy is much more process sensitive than a screwed / riveted one. If the entire prep. and bonding process is not followed carefully, there can be much bigger problems than just a crack, but I fully understand peoples desire to find something different with the small percentage of cracks that have occurred (if you look at the size of the entire fleet as a whole... but I digress).

My post was to point out for current and future novice builders that bonding on the canopy is no absolute assurance of no cracks (or other problems). The tone of the majority of posts here in the forums regarding Sikaflex do not generally portray it that way.

BTW, attempts are being made to improve on canopy installation design.... All of the fasteners for installing the canopy and rear window on the RV-14 are screws (no rivets). Having direct control of the canopy attach fasteners clamping pressure goes a long way towards reducing the likelihood of cracks.
 
Scott - in this vein, I should have complimented Vans on the tremendous improvement in the canopy for the 14 over older models. While I have not had the "pleasure" of making "the big cut" and trimming a canopy, other builders have looked over my 14 canopy and spouted praise to Vans for the tremendous improvement the 14 canopy represents. One RV6 builder looked at my canopy sitting on the frame/fuselage for several minutes, asked "So this is the way it came out of the box?" and to my affirmative response said sarcastically "You suck!"

Kudos for the improvements.
 
After much planning, yesterday (Saturday) was the big day - we mounted the canopy to the canopy frame using Sikaflex. It was a stressful day, not because of problems, but just because the stakes (and expectations) were high. My partner, Christine, and I did all the extensive prep of masking and scuffing, as well as the application of Sika Aktivator, Sika Primer and finally Sika Adhesive. For the canopy placement, however, I asked several neighbors/former builders for assistance ? here?s a great shot of how the neighbors in our community of Pecan Plantation pitched in. Special thanks to Tom and Bonnie Lewis, Martin and Claudia Sutter, and John Kleber.

ng29m0.jpg


I will not attempt a photo blog (others like Bruce Hill and Bruce Swayze have set that bar way too high already) but here is an overview description and some salient observations. The prep work (as with painting) is the most important part, and can take as long as you like, and pays off. However, with Sikaflex, once you start the process, the clock is running. We began applying Sika Aktivator to all bonding surfaces about 1:00 pm (it dries for at least 10 minutes, no more than 2 hours) ? this took 10 minutes and was quite easy. We started the Sika Primer application about 1:20 pm ? it is more technique sensitive, with runs being the biggest problem (it?s very thin) ? a helper nearby with paper towels and alcohol is important. Primer goes again on all bonding surfaces. This was done by 2:10 pm ? the Primer needs to dry for at least 30 minutes and is ?active? for 24 hours. I began applying Sika Adhesive about 2:30 pm and it took about 30 minutes. It is applied to one surface only at each bond. While very similar to caulk, an intensive half hour was very hard on the squeezing hand. Also, since the Adhesive begins to set up at 1 hour, there is some time pressure. The group of assistants pictured above helped position the canopy on the canopy frame (where the Adhesive had been applied) and which was already locked on the fuselage. 3 people held and aligned, 2 ?coaxed the plexiglass inside the ?ears? and lots of alignment checks were made (about 3:20 pm). Still under time constraints, Adhesive gets applied to the bottom of the sides and the inside of the side skins, which are then Cleco?d in place. Fillets got made along the inside and outside of the canopy sides and masking removed ? nothing was required along the aft canopy frame or inside/outside of the front edge. Weights were placed, straps wrapped and cinched and a couple more clamps placed strategically. Done about 4:15 and the Sikaflex was already setting up.

Today (Sunday), the Sikaflex Adhesive had set up enough to remove the canopy assembly from the fuselage to the work table. Additional Sika Adhesive was caulked into the fore and aft sides of the aft canopy frame and the front side of the canopy on the glareshield. This was smoothed to a nice fillet and masking removed ? 3 hours today.

I am quite happy with the results ? I?d give it a B+ or even A- and declare it very much worth the effort. Things I might do differently:
- I would buy an extra tube of adhesive and have 2 people applying it. This would give more time to work the sides, fillet edges etc. before it set up.
- I would cut a larger ?V? in the tube to apply a large V of caulk and ease dispensing.
- I would investigate powered (or pneumatic) guns to ease the application of adhesive.

RV-14 has some specific considerations as well ? the blogs I mentioned above by Hill and Swayze are for an RV-9 and RV-7. The biggest RV-14 specific is that the screws that hold the aft edge of the canopy to the aft canopy frame (Vans install) also hold on a gap seal between the aft canopy frame and roll bar. Sikaflex installation eliminates these screws so a work around is needed to attach the seal. I chose to countersink the aft canopy frame for the screws so their heads end up under canopy and covered by the Sikaflex bond line, and installed the seal on the aft canopy frame before installing the canopy.

I would also note Scott?s comments in this thread and reinforce that this is NOT a trivial undertaking. Because it is a deviation from the plans, it takes considerable investigation and planning, lots of attention to detail and good technique. Proceed at your own risk.

I?m happy to share my experience with anyone who cares ? just post a message or send a PM and I will respond.
 
Another WARNING on the primer, if you do anything, take all the precautions of taping up every square MM of plexi that does not get primer, I used a small paint brush and was carful not to let the bristles fling at the end of a stroke.
 
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