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  #1  
Old 05-02-2021, 07:03 AM
DavidHarris DavidHarris is offline
 
Join Date: May 2018
Location: Upland, CA
Posts: 152
Default Reinforcing Canopy Crack

Despite using Sikaflex, my RV7A slider canopy developed a crack after sitting out on the tarmac for a cold night this fall.

I stop drilled, which has stopped the hole growing. Then I repaired with Weldon #3 in the crack as other builders have reported on this forum. The repair held for about a month. I repeated with the same results.

Any suggestions how to reinforce such a repair?

I'm pondering bonding a thin half-inch-wide strip of something transparent and moderately flexible to the underside of the crack, but am unsure what materials to use.

Or maybe it just needs multiple applications of Weldon or some prep of the top surface of the crack?

Thank you,

David Harris
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Last edited by DavidHarris : 05-02-2021 at 07:11 AM.
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  #2  
Old 05-02-2021, 07:40 AM
Allan Stern Allan Stern is offline
 
Join Date: Jan 2006
Location: Cape Coral, Florida
Posts: 297
Default Crack

Think about using a piece of clear gorilla tape on the underside of the crack.
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  #3  
Old 05-02-2021, 08:19 AM
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Skid Skid is offline
 
Join Date: Jun 2006
Location: KBUU
Posts: 251
Default Canopy crack repair

David,
I used Plastifix to repair the ~20" crack in my slider canopy about 10 years ago and it is still holding. It is not clear, but as it is above my head it has not been an issue. I am going to replace the canopy one of these days...
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  #4  
Old 05-02-2021, 08:43 AM
PhatRV PhatRV is online now
 
Join Date: Mar 2018
Location: Buena Park, California
Posts: 564
Default

I had a smaller crack in my plexiglass and I used plastifix as mentioned before. Fortunately, the crack was covered with the fiberglass skirt.

After many years of woodworking, one concept we used is "accentuate the flaws". At first, the concept is preposterous but the logic is when you decorate the flaws with other more elaborate details, people will notice the new detail as another design instead of noticing the original flaws. After you get your canopy fixed, you can decorate the canopy with painting over the flaws in the shape of a sunshade or cover it up with a sunshade pattern of dark tint. And if you embellish the new patch overlay with other interesting details, the crack magically disappears. It's funny how the mind works.

Good luck on the repair.
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RV8 standard build: Empennage 99% completed
Wing -- Closed
Fuselage -- Canopy Done. Fiberglass 80%
Avionics Installation -- 90%
Firewall Forward -- Cowl completed. Baffle 90%
Electrical -- 90%

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  #5  
Old 05-02-2021, 09:10 AM
David Paule David Paule is offline
 
Join Date: Dec 2009
Location: Boulder, CO
Posts: 5,002
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You won't like this idea and I'm only mentioning it for historical accuracy. Back around 1970 a helicopter (with a low Vne compared to RVs). had a badly cracked bubble. The mechanics drilled small holes along both sides and used .020 safety wire to lace it up like a shoe, putting lacing on both the inside and the outside.

Looked terrible - held well.

Dave
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  #6  
Old 05-02-2021, 10:20 AM
Ralph Inkster Ralph Inkster is offline
 
Join Date: Feb 2008
Location: Calgary, Alberta
Posts: 1,536
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Pure speculation here.
It looks (to me anyway) the crack is caused by stress around the latch hole. Any glue repair will fail again unless you relieve the cause. I suggest you remove the latch handle & shaft to see if the plexi is to tight around the small latch tube causing expansion/ contraction stress from temp changes. If so, take a dremel with a very fine bit & gently grind it out a bit. Than try the glue again.
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  #7  
Old 05-02-2021, 11:09 PM
DavidHarris DavidHarris is offline
 
Join Date: May 2018
Location: Upland, CA
Posts: 152
Default

Thanks! This sounds wise to check out the canopy latch clearance and to explore plastifix. I'll pass on lacing with wire!

David
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