Gluing Your Canopy

From Matronics

< General Interest

This information has been gleaned from various discussions on the RV-List over the past few years. I'm collecting it all into one place in hopes that future builders can benefit from it, and hopefully save them some searching.

Contents

The Products

Sikaflex

Sikaflex is the product that most people seem to have used to date. The product of interest is Sikaflex 295UV, it comes from their Marine Products division. Here are the Technical Data Sheet and the Installation Guide for Sikaflex 295UV. There are at least a dozen builders using this method, and reports of three flying, but no indication as to how many hours are on each installation.

There is also a Sikaflex 296, that has better mechanical strength properties, but there is no indication that someone has used it for an aircraft application yet. Note that the Limitations section of the 296 TDS specifies 'Do not use to bond organic glass (i.e. polycarbonate and acrylic)'.

Proseal

Every RV builder should be familiar with Proseal. The same product you used to seal your fuel tanks has also been used to bond a canopy to its frame. Here is the Technical Data Sheet for Proseal 890 Class B. There is also a Proseal 890-Class B-Type II, i'm not sure how that compares.

Note that one of the builders who used this method has reported delamination problems.

SemWeld

3M makes a product called SemWeld that has been reported by one builder to work for bonding a canopy to a frame. The builder reports 300 hours on the airplane with no problems.

Builder's Experiences

Sikaflex

Glen Matejcek

(copied verbatim from the RV-List)

I have an update on my RV-8 glued canopy. The canopy is now glued on, cut, filleted, and the edges are dressed. Along the way I came up with a few data points I'd like to share. First though I'd like to thank those who've gone before, especially Billy and Mickey. Thanks guys!

WRT the chemicals used, the cleaner does have a primer element to it. It is very easy to use and the minimum purchase quantity is several times what you will need. The primer itself is about double or more of what you need. The primer forms a very smooth surface for the adhesive to bond to. This is a fundamental requirement of the process. Somewhere out there in cyberworld is a recommendation to scuff the primer if you can't get the adhesive in place right away. This would be a large mistake, as would adding another coat of primer. Per the manufacturer, the adhesive is to be applied to the primer within 2 hours. Between 2 hours and about 3 days, you can simply wash the primer with the cleaner, and it will re-soften it adequately to apply the adhesive. Scuffing the primer will cause a significantly weaker bond, as the adhesive won't flow into the 'tooth'. If you were to scuff the primer, you should remove ALL the affected area and start the process over with the cleaner. Adding a second coat of primer would make an unacceptably thick, and therefore structurally weak, layer.

When applying the adhesive, I used perhaps 2 dozen latex gloves. This helped me to keep the project (and myself!) pretty clean. My wife and I had no trouble doing the installation by ourselves. Per Mickey's suggestion, I used segments of garden hose to space the canopy off of the frame. This provided for the proper thickness of adhesive, which is required to allow for differential thermal expansion of the canopy components. I applied adhesive to most of the area where the canopy bow and roll bar contact the canopy. I put dabs of adhesive along the lower bar of the canopy frame, as well as on the forward fuselage skin where the canopy would rest. This served to 'tack' the canopy in place until I could do a proper finish job. Spring clamps were used to hold the canopy tight to the garden hose spacers.

Once the initial gluing was cured, I used Billy's idea of scoring the primer from the inside with a screw to locate the big cut, then re-marked it with masking tape on the outside. A die grinder and cutting disc made pretty quick and easy work of the cut. I did underestimate what the final kerf was going to be, but the gasket will take care of that just fine. If you want to have the canopy and windscreen edges butt cleanly with no gasket exposed, I would recommend only gluing the winscreen to the airframe before making the 'big cut'. After making that cut, I'd reposition the canopy forward and glue it in that position to ensure a smooth canopy profile.

Once the canopy was cut from the windscreen and removed from the plane, I prepped and finish glued it. This involved back filling the areas where the spacers had been and creating aesthetically pleasing fillets. In most places this is easily done with a gloved finger. For the windscreen base, I used a four inch diameter ceramic candy dish as a squeegee. It worked extremely well, was very convenient to grip, and cleaned up easily.

The glue actually had to sit for 2 days before I was comfortable handling it. After 2 weeks, it is a whole lot tougher.

To dress the 'big cut', I used 100 and then 220 grit self adhesive sandpaper on both sides of a 1/2 x 1-1/2 x 6" sanding block. I closed the canopy on the block and then sanded both sides of the cut at the same time. This ensured that the two cut edges stayed parallel as I cleaned them up. I final finished them with scotchbrite, and am quite pleased with the results.

The way I did my installation, two tubes of adhesive was just about enough to do the canopy, but not the skirt. That will require part of a third tube.

The canopy skirt is a one-piece custom made part. A local composite guru advised me that would be a much more satisfactory aproach than trying to get the factory parts to work well. So far, I'd have to agree. Attaching the skirt with SikaFlex is pretty straightforward, also. All the external canopy surface that was not to be glued was masked. A second layer of tape was applied over the first right at the edge of the glue area. The fiberglass, steel tube frame, and canopy were scuffed in the appropriate areas. The Sika cleaner was applied to the entire exposed edge of the canopy, and to the three exposed clusters on each side of the canopy frame. 1/4 wide x 3/32 thick double sided self adhesive foam tape was put all around the bottom edge of the canopy. This serves to both maintain an appropriate glue line thickness and to hold the skirt in the propper place while the adhesive cures. Next, primer is applied to the apropriate areas. Once that is dry, adhesive was appplied to the exposed canopy, and dabbed on the three clusters on each side. The skirt was set into proper alignment and pressed into the foam tape. The upper fillet was formed from 'squeeze out' and a little additional adhesive using a gloved finger. The top layer of masking tape was pulled to give a nice, sharp edge to the glue line. All the forward and lower edges of the skirt were duct taped in place.

The next day, the canopy was removed from the plane, and the skirt / frame tubing were filleted just as the canopy / canopy frame had been.

I plan on waiting at least two weeks to ensure complete curing of the adhesive prior to masking the inside of the canopy and painting the frame and inside of the skirt a uniform color. This will not only be asthetically pleasing, but will add UV protection for the adhesive.

Mickey Coggins

Mickey Coggins is building an RV-8 and has used Sikaflex to bond his canopy to the bow. His procedure was to first fit the canopy to the frame, make the big cut separating the windshield from the sliding portion, and then glue the two parts to their respective frames. Note the clever use of garden hose spacers to keep the canopy properly spaced from the frame to allow for a good bead of Sikaflex to fill the gap (more about this later).

What Mickey Learned:

  • When fitting the canopy to the frame and trimming the edges, do it with the garden-hose spacers in place. Without them the canopy will sit a little lower and won't quite be the same fit. If you don't do this, you risk trimming too much material from the plexiglass.
  • Clamp the canopy to the frame, and use a bit of Sikaflex to glue it on - don't try to do too much until the canopy is glued to the frame. Once the canopy is tacked in place, then you can remove the spacers and take your time to run full beads along the edges. The initial gluing step would require about 30 dabs of glue around the frame.
  • Make sure your primer strip around the edge of the canopy is at least 1" to 1.25" wide. Mickey did about 0.75" and says that it was not quite enough.

Billy "Barefoot" Waters

Billy Waters has a good writeup of his glued installation on Mike Stewart's RV Project website. Unfortunately the link to the photos is broken, but I think between Billy's text and Mickey's photos and text, you'll have a pretty good set of instructions to work with.

One thing to note is that Billy glued his canopy to both the windsheild and the slider frame at the same time, *before* making the "big cut" separating the two. This would no doubt result in a more guaranteed smooth transition between your windshield and slider (or between your tipup and rear window, I suppose). I have seen a few RV's with no skirt at this join, and it looks very slick when the join is fingernail-tight.

Kevin Hester

[ Update 6/8/2006: I now have 100 hours on my RV-7A. I'm still very pleased with the Sika ]

Various other posters have already covered most points, but since I've done the adhesive canopy thing I'd like to add a few notes:

  • Thanks to Chalkie for getting this great idea started with his Sport Aviation article
  • Sika is a bit of a pain to work with, but no where nearly as nasty as proseal. If I had it to do over again, there's no way I'd even consider using pop rivets.
  • I really like that with Sika your canopy mates right up with your windscreen - no need to make the fiberglass lip
  • Before applying the black primer to the plexi, be very careful about masking (duh)
  • Rough up the rollbar powdercoat pretty good before applying the sika prep clear fluid to it.
  • Also apply masking tape to the rollbar where you don't want any sika to stick.
  • The clear sika prep fluid will slightly roughen any plexi that it is allowed to sit on for an extended time. Either use masking to protect against this (particularly when doing the canopy frame with the plexy upside down over the table) or when you screw up wipe up excess with a paper towel. It is a very slight effect but noticeable if you look at the right angle.
  • Although Sika says it is dry within a day(?), it really takes a few weeks before it is as strong as it is ever going to be. When I did some test pieces I was initially a bit concerned with the strength of the bond but two weeks later it reached the point where I was breaking plexy before sika would come off. (Not a very scientific test though).
  • Use this 'slow dry' property to your advantage - if you need to mechanically remove any sika that squeezes past masking tape, it is much easier to do this the day after the lay-up than a week later.
  • I had one helper for the actual bonding day of the windscreen to the rollbar, I'd recommend two helpers. ;-)
  • If you are doing sika, you probably want to make your aft skirt out of fiberglass rather than aluminum. The fiberglass skirt only takes a day to make and you can bond it with sika as well - no pop rivets through the plexi and the frame.
  • Like anything - doing it the first time takes _much_ longer. If you can find someone local who's done it, buy em with beer to come help on windscreen bonding day (canopy bonding is way easier). I'm happy to help any SF Bay Area builder who decides to go this way...

Gert

(quoted from the RV-List) (spell-checked by [User:Snowflake Rob])

Below is an exerpt from an earlier email with glue info sent before I actually glued it.

I have since glued the canopy on with good results. The one thing I would do differently is to glue the canopy on with bare minimum of glue, let this set, and then go back and backfill and smooth out for better aesthetics. My canopy moved a tad too much and it was hard to get an even looking result.

--

Yes I definitely will try and glue. As a matter of fact, I talked with SIKA, the folks mentioned in my previous email and the Sport Aviation article. (Steve @ 1-888-832-7452).

Very, very nice person. His first words were "Sorry, we do not support your application." But right after that, "now that I have said that, how can I really help you..."

We talked for a while, Steve mentioned that his phone has been ringing off the hook ever since the Sport Aviation article came out. He kinda jokingly grumbled that he has had more response to an article SIKA did not write, for a use SIKA does not support, in a magazine SIKA did not know about, than what his total advertisement budget generated last year.

Steve said I should very carefully read the info at the Sika website for the product. He recommended to use SIKA 209 to cover the plexi to make it opaque, SIKA 226 for cleaning the frame, and SIKAFLEX 295UV BLACK for gluing the canopy on, trying to get at least 1/8" space between the canopy and the frame.

He recommends that all structural bonding be done with the BLACK urethane as it has much better UV properties. If needed, one can make fillets with WHITE urethane over the black stuff, 295UV comes in black and white colors.

Most places I called would only sell a case of 12 10-ounce tubes of the 295UV. Again, Steve came to the rescue... Jamestown Distributors @ 1-800-423-0030 will sell you individual quantities. Pricing: about $12US for a tube of 295UV black or white, $31US for a pint of 209 and $11US for a pint of 226. So that's what I ordered, one tube each of black and white, one pint of 226 and one pint of 209. One could say I am now committed ;-)

Took me a weekend to cut the canopy. Agony, agony, agony, lots of sweat... If there is one thing I would do different it is not cut the rear of the canopy till I have the front close. Originally, my canopy did not even cover half the tubes on the side frames of the slider. By dropping the front 1/8" at the time I brought the sides of the canopy till just even with the bottom of the frame. This however did 2 things, one it brought the highest point of the canopy forward as it is sliding over the roll-over bar, and two, it pulled the rear of the canopy forward. I had cut some off the rear in an attempt to make the canopy come down as a whole. (I am 6'6", I need all the headroom I can have ;-)

Well, there you have it, my experience so far for posterity, to pass along if you so wish. I will let you know what transpires when I get to the gluing bit. Let me know if you can milk any info out of Charlie, Sure would like to know what sticks better to plexi and canopy frames than Kryptonite to Superman.

James Bowen

(quoted from the RV-list)

Sikaflex advises to use the black as it has a much better UV tolerance, also, u have to maintain a minimum gap between frame and canopee for the sikaflex to work. According to the lad i talked to, if u do not allow for a gap, the sikaflex will eventually rip from expansion differences between plexi and frame.


Jim Ellis

 Sikaflex 295UV, cleaner and primer
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Sikaflex 295UV, cleaner and primer



 Two of the eight clamps that hold plexi against side frame
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Two of the eight clamps that hold plexi against side frame



 Use four clamps per side while adhesive sets
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Use four clamps per side while adhesive sets



 Bonding primer band is three inches wide
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Bonding primer band is three inches wide



 Sikaflex fairing is sanded to shape with 120 grit sandpaper
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Sikaflex fairing is sanded to shape with 120 grit sandpaper



 Forward fairing is painted for UV protection
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Forward fairing is painted for UV protection



 Finished glued Sikaflex canopy
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Finished glued Sikaflex canopy



 Machine screws hold the aft edge of the rear window
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Machine screws hold the aft edge of the rear window



 The completed canopy has no visible screws
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The completed canopy has no visible screws
The following describes the process I used for gluing (and bolting) the canopy to the tip up frame on my RV9-A.

You will need two 10.3 fl oz. tubes of Sikaflex 295UV Adhesive, one 250 ml bottle of Sika-Cleaner 226, and one 250 ml bottle of Sika Primer-209N. These can be obtained from Jamestown Distributors.

You will also need some mineral spirits (paint thinner) for cleanup of the uncured adhesive. Once it cures nothing seems to dissolve it. Also buy lots and lots of masking tape. Cheap vinyl electrical tape from Ace Hardware is good to use because it removes without tearing.


Drill #40 pilot holes for the 14 bolts through each of the side frames, but do not drill through the Plexiglas or the side skirts. All twenty-eight side frame bolts may, in fact, not be necessary. The bond that the Sikaflex creates between the plastic and the aluminum is incredibly strong. The plastic will break or the aluminum will bend before the bond will let go. However, the bolts assure that the plastic and frame will stay together even if the adhesive were to fail.

Make eight "U" shaped clamps, four for each side, from 2" x 4" x 1/8" wall thickness aluminum tubing by cutting one of the 2" sides off the tubing and threading a 5/16 bolt into one of the 4" sides of the tubing. Each clamp is about three inches long and sits under the frame with the open end of the "U" facing up. Note the small 3/4 inch thick wood block attached to each clamp which allows the clamp to wrap around the bottom flange and press against the inside of the frame. 2x4 rectangular aluminum tubing is a fairly common item found at metal supply houses. They may even have a two foot long cut-off piece they will give you.

Fit the canopy to the frame. Place three or four rubber hose washers under and along the forward edge of the canopy and three or four washers between the plastic and the canopy bow frame while trimming and aligning the canopy in order to assure a 1/8" to 3/16" gap between the Plexiglas and the metal. Using the washers will assure that not too much is trimmed from the sides.

If you have not done so already, this would be a good time to paint the glare shield area of the tip-up canopy forward skin before proceeding.

The forward and aft edges of the plastic need to be prepared for the adhesive before clamping the plastic to the frame. Mask the front edge of the Plexiglas with a 1" wide edge band on both the inside and the outside. Rough the plastic with red scotchbrite pad, clean and prime. Do the same thing with aft edge of plastic canopy, but make the adhesion band 2" wide on the inside only. The total width of the black primered area over the roll bar and canopy bow is three inches, two inches on the tilt up portion and one inch on the aft window.

After preparing the contact area of both the side frames and the Plexiglas with Sika cleaner and Sika primer apply a layer of Sikaflex 295UV to the side frame. With the canopy in its final position, with all of the washer/spacers in place, tighten the "U" clamps to hold the Plexiglas sides to the frame. Run short 3" or 4" beads of Sikflex along the front edge of the plastic skipping the places where the washers are located. Do not apply too much. You can fill in the gaps and build up additional thickness later. Do the same thing along the forward side of the canopy frame bow. You will have to climb in through the rear window opening to do this...or find a small volunteer!

Wait at least 24 hours before removing the clamps and opening the canopy. Remove the hose washers and run a solid bead of Sikaflex on the inside and outside of the forward edge and along the fore and aft sides of the canopy frame bow. BoatersWorld sells eight inch flexible caulking tips, Item #366981405, that screw onto the Sikaflex cartridge that make applying the adhesive to the gap between the lower inside forward edge of the canopy and the glare shield much easier.

After allowing all the new adhesive to set, back drill the previously drilled pilot holes in the side frame through the Plexiglas with a #40 plastic drill, countersink the outside of the Plexiglas for a #6 AN507-6R8 machine screw, and then ream or drill #27 through both the side frame and the Plexiglas for bolt clearance. Special drill bits for Plexiglas in both fractional and number sizes are available from Abbeon Cal, Inc.

Lightly bolt the canopy sides to the frame as shown in the plans (but not through the side skirts). Tighten the nuts just enough so that the bolts can still be turned easily with a screw driver. Pilot drill the side skirts for only the rivet holes, not the bolt holes, as shown in the plans. Clamp the skirts to the side frames, match drill into the frame and dimple the skirts/countersink the frame. Mask and prep the outboard edge of the plastic and the side frames. Place a thin layer of Sikafex (Non-structural, so thin is okay in this instance.) on the outboard surface of the frame and Plexiglas and clamp the side skirt in place with clecos until the adhesive cures.

Finally rivet the side skirts to the frame.

You should be able to squeeze all but the aft three or four rivets with a longeron yoke. These may to be set with gun and bucking bar. Clamp the canopy frame to the main longeron while riveting in order to reduce the vibration stress on the Plexiglas.

The forward fairing is molded with additional Sikaflex adhesive and sanded to shape with 120 grit sandpaper. If you want to paint the fairing, (a good idea to improve the UV protection for the Sikaflex) wait at least one week for the Sikaflex to fully cure. Do not use a mineral based paint. It will not dry properly. Instead use a polyurethane or water based enamel.

Note that the forward edge of the rear window is bonded to the roll bar, but the aft edge of the window is attached with machine screws per the plans. This was done because it is very hard to hold the minimum adhesive thickness of 1/8 inch required for the Sikaflex. Silicone sealant can be used here to waterproof the joint between the plexiglass and the metal.

The finished bonded canopy looks terrific with no visible screws.


Wayne Pedersen

(copied from the RV-List) (Wayne is building an RV-7 with a tip-up canopy)

I used Sikaflex for attaching the plexi on my tip up as well as using it as a fairing at the front of the windshield. Pretty straight forward just go to their web site and follow the instructions. Basically its prep, prime, apply and clamp.

Drop me a line if you have specific questions.

[Someone in Germany]

Here's a photo of an RV-6 in Germany that has used the Sikaflex process. Hosted on Mickey's website.

Don Hall

Back in Dec 2007, my canopy cracked during the drilling process. I was devastated. I originally thought I might try to repair the crack and move on, but this was one booboo that would have been visible and in my face with every flight. What's another thousand bucks anyway? I ordered a new canopy and waited for Georgia's hot summer weather. This time around, I went with Sikaflex. This website was an amazing resource. I'm not sure there's much to add beyond what's been said by those who have been before.

I'll add a few bullets: - tape like crazy around every edge you intend to glue. Then after you smooth the fillets, you can just remove the tape with minimal cleanup. - If you get sika somewhere where it's not supposed to be, no big deal. Let the mess dry. It will come right off any smooth surface after it's dried. sika will absolutely not stick to any paint or plexi surface that has not been properly primed. Use that to your advantage, and make sure you prime according to directions. - Use lots of gloves. - Sika Slick Lubricant is very useful stuff for creating nice fillets. After you apply the glue with the gun, put on a clean glove and spray some lubricant on the fingertip. Use the lubed finger to smooth your fillets. - Sika Hand Cleaner. Awesome stuff. Great for cleaning hands, paint surfaces, tools, or anthing that the sika got all over. I'm not sure if this stuff is good for plexi, so keep it away from that. It's easy to get sika off plexi later anyway.

My website, donka.net, documents my build and has the pictures. Click here for quick jump to end of canopy gallery.

Sikaflex is the way to go. Good luck and thanks to all those who have contributed before me.

Proseal

Mark P

(quoted from the RV-List)

I used proseal to attach both canopy parts (tip-up) to the canopy frame and cabin frame (rollbar) to avoid exposed screws or holes in the plexi. (Screws and proseal were used for the rear skin and sides of the canopy frame)

Due (I believe) to the different expansion rates of the aluminum rollbar and the plexi, as soon as the plane was exposed to some real heat in direct sunlight, the proseal separated from the plexi in some areas of the rollbar, but has held nicely to the canopy frame, which is less rigid than the rollbar. I didn't scuff the plexi prior to application which may have contributed to the separation, just thoroughly cleaned it. Other materials may hold better, but I would be concerned about the stresses from temperature variation. I you're doing a slider, this may not be as much of an issue, however.

Kelly McMullen

(quoted from the RV-List)

As I had posted before, ProSeal is the specified sealant for Mooneys windows, and has been for probably 25 years, after the early 201s had some corrosion problems from side window leakage.

I'm not sure what retention method is used on the newer models. The older models have retention clips that hold the plexi in place against the exterior skin, and the clips are held by counter sunk screws on the outside and self locking nuts on the inside. Of course the exterior skin is subject to both expansion/contraction as well as wind forces, as it is only skin and is non-structural, as the Mooney uses a chrome moly steel tube frame for the cockpit.

SemWeld

Chuck Robowtham

(quoted from the RV-List)

We used SemWeld from 3M - came in a caulking type tube (you'll need one their caulking type guns - see if you can borrow one from an Auto body shop). We have 300 hours on our canopy -No issues. It can also be painted. You might want to check the archives under my name back in 2001 - I'm pretty sure I posted a report on it. Please email me off line if you have any questions.

Conclusion

A number of builders have successfully used adhesive products to bond their canopies to the frame. The only post-installation problem reported was when using Proseal, and the builder admits that he may not have properly prepped the plexiglass before bonding it to the frame. It would be interesting to hear from a builder who has used Proseal successfully, as this is a material that we're already familiar with and have ready access to.

The builder wasn't descriptive enough in his message, but it is possible that he bonded his canopy without properly spacing it from the frame as well. It's intuitive to think that just putting a bead of adhesive on the frame and dropping the canopy in place will be adequate, but unfortunately this is likely to squeeze out too much of the adhesive and not leave enough to allow for thermal expansion and contraction differences. Mickey's instruction to use the spacers, tack the canopy in place, and then go back and fully seal it in after the spacers are removed is no doubt the best method, regardless of the choice of adhesive.

Other Sources of Information

  • Sport Aviation, January 2004 - Apparently has an article on using Sikaflex to install canopies
  • Matronics Search Engine - Searching for "sikaflex", "glueing canopy", or similar phrases will return lots of entries.