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SikaFlex removal

Strike69

Active Member
Sadly, after not flying in Feb/Mar due to the harsh winter, I went to go fly only to find a 12" crack in my canopy. :(

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Now I am working through fitting a new canopy (went with Todd's). Phase I was removed of the canopy from the frame.

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Phase II will be clean-up and prep of the frame and Phase III actually fitting the new canopy (hoping the second time around is easier).

The Sika experts suggested using MEK to clean up the frame but where not 100% sure it would be successful. Has anyone gone through this process and what did you use?

Thank
Strike
 
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Have not done this but ... manufacturer is always the best place to start; their recommendations always trump third-party anecdotes. That said, if you can get the old Sika cleared away enough to fit the new canopy, I'd be willing to bet that a new application of primer and Sika would cover the remaining and stick just fine. Still, I'd ask the OEM for advice.
 
If it is like any other polyurethane adhesive, the only thing that will remove it is violence. That stuff seems to be chemically bullet proof. I would start with a scotchbrite pad on a pneumatic angle grinder and if that wasn't tough enough I would go, carefully, to a sanding disk. A cracked canopy must really suck. Sorry.
 
Sadly, after not flying in Feb/Mar due to the harsh winter, I went to go fly only to find a 12" crack in my canopy. :(

Now I am working through fitting a new canopy (went with Todd's). Phase I was removed of the canopy from the frame. Phase II will be clean-up and prep of the frame and Phase III actually fitting the new canopy (hoping the second time around is easier).

The Sika experts suggested using MEK to clean up the frame but where not 100% sure it would be successful. Has anyone gone through this process and what did you use?

Thank
Strike

Sorry can't help with the sikaflex removal, but what's up with the crack?

I am getting ready to install the canopy and was thinking about using sikaflex specifically to avoid the cracks. I've heard that cracks happen with screws but the adhesive allows some flex and the stress is distributed around the frame. Maybe I'll re-think that logic...
 
Sorry can't help with the sikaflex removal, but what's up with the crack?

I am getting ready to install the canopy and was thinking about using sikaflex specifically to avoid the cracks. I've heard that cracks happen with screws but the adhesive allows some flex and the stress is distributed around the frame. Maybe I'll re-think that logic...

No trying to start a screws vs sikaflex debate, but cracks happen with sika as well, especially with the -8 canopy. I am just assuming that my canopy will crack eventually, and building it with eventual replacement in mind, therefore using the pop rivets, etc. YMMV
 
Canopy crack

I discussed this with Todd and he suggested relief curves around each vertical frame bar. That is my plan.
 
Whatch the temperatur!

I think you can controll this a bit. Most of the people are afraid about cracking there canopy, so they het up the shop when ever they handle the canopy, even during the glue on process. Due to this you will create most of the stress in winter, when the canopy is britle and prone to crack.

If you during the final installation can go as close to the mid range or below the mid temperature that your canopy will seen, then there should be less stress on it.

Just my 2 cents.
 
Cracked Canopy

The canopy needs to be able to expand and contract with temperature. I remember it was winter when I was installing my tip over canopy and it was cold in the building at first and I took a measurement and after the building warmed up some I measured it again and was surprised that I came up with a different measurement, the canopy expanded to a new size. Understanding the expansion I started from the front with small slots cut for the rivets and as I moved rearward I cut the slots longer and longer.
I covered the canopy frame with velvet like stuff called flocking so the canopy could slide easily under the rivets. No cracks so far and I have flown in below zero air temperatures to well above 80 degrees with out any problems. Here is a close up of the canopy frame with the flocking
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I would be careful using an abrasive disc on the canopy frame. The reason is that if you sand/grind through the Sika and into the frame you may not know how far through the frame metal you have gone. I would first try a new sharp razor blade to see if you can cut/scrape it off. Will a heat gun soften it up any?
Keep us posted on how you progress.
 
me too

First of all .. so sorry for your loss..

I was going to do the Paul Dye surgical tubing rivet method, but the previous builder didn't leave enough canopy hole-edge distance for the holes.. and just the starter holes were there..

I recently ordered all the SIKA to do this, and have been waiting for this warmer weather.. hmm re-thinking AGAIN..

great ideas here.. thanks..
 
80 grit sanding flap wheel and Dremel

I had to remove Sika from my RV-8 canopy frame and I used a dremel with a 80 grit sanding flap wheel. The sanding flap wheel will easily remove the Sika, bit it will also likely remove the powder coating from the frame. I repainted my frame afterwards. Do it outside because you will have lots of Sika dust. I had no issues with it removing too much metal from the frame, just stop sanding when you remove all the Sika. A 120 grit wheel also works, but its less aggressive in it removal abilities. When repainting the frame, make sure you use a paint that is compatible with Sika.
 
If it is like any other polyurethane adhesive, the only thing that will remove it is violence. That stuff seems to be chemically bullet proof. I would start with a scotchbrite pad on a pneumatic angle grinder and if that wasn't tough enough I would go, carefully, to a sanding disk. A cracked canopy must really suck. Sorry.


Now that's funny right there!
 
sikaflex removal

I fouled up the glue up and to remove part of my canopy skirt. Cut it loose with a gigli saw--the metal flexable thing that looks like a wire. I then cut off most of the sika with a sharp blade. Primered the remainder, Sika over that. Bonded very well. I think there is no need to get it all off. Just enough so the next canopy sits properly.

Good luck. This is a major PITA
 
SikaFlex removal/Canopy Repair Update

Taking the advice of some - brut force (note the hammer) and a sheetrock knife where the best tools for removing the old skirt, canopy, and windscreen. While the bond is super strong in keeping the canopy on the frame, the knife made easy work of it. Followed up with some sandpaper to clean up the frame and it was ready for re-priming of Sika.

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One change from previous in prepping the canopy is cutting notches where the frame skirt vertical supports intersect. I am told these should provide sufficient stress relief to hopefully prevent having to do this R+R again.

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Why is it that any time you do a job a second time things always seem to go easier? I have been dreading this repair work all spring/summer (okay also took some time off when my kids were here). I would love to go back to the start (with ALL of the knowledge I have gained since starting in Dec 2011) and build again.

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Still some clean-up work to do inside the windscreen but almost complete.

Much happier about the skirt fitting and look forward to much less wind in the cockpit this winter.

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The skirt is off to paint then bonded to the frame next week. If all goes well, I should be back in the air next weekend!
 
Cracked Canopy

Scott

'' A cracked canopy must really suck. Sorry.''

Well ask me if I know the feeling....I'm on my 4th canopy on my RV-4.:rolleyes:

Planning to start the new replacement tomorow...

Sikaflex again with a Todd's canopy this time and a new frame ( I have 2 spare..:)

Bruno
[email protected]
 
Leave 1/8" gap between canopy and frame

I think a key thing in using the Sikaflex is to allow enough thickness of Sikaflex to act as an expansion buffer. I used short segments of garden hose as spacers, and filled the 1/8" gap between the canopy and frame with the Sika. Once cured, I pulled out the spacers and filled the remaining gaps.

I think this is S.O.P.

If you make that gap too small, the canopy and frame are too intimately connected and the canopy will break when it shrinks more than the steel frame.
 
I think a key thing in using the Sikaflex is to allow enough thickness of Sikaflex to act as an expansion buffer. I used short segments of garden hose as spacers, and filled the 1/8" gap between the canopy and frame with the Sika. Once cured, I pulled out the spacers and filled the remaining gaps.

I think this is S.O.P.

If you make that gap too small, the canopy and frame are too intimately connected and the canopy will break when it shrinks more than the steel frame.

Exactly! A thicker bead to carry the wider expasion envelope of the 4 and 8 canopies.
 
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