Hi,
Sonex Legacy 175 hrs, a few months short of 2 year since first flight
Did my pre flight. Taxied down to the Club House. Came back to my Sonex & saw a 50 mm (2 in) crack in the Canopy had just appeared.
Crack is almost exactly mid point, on the opening side, radiating perfectly straight up. Its so perfect, it looks deliberate.
What to do??
Should I drill a stop hole?
Perspex glue?
My last air craft had no cracks after 20 years, now this!!!
Any good instructions on how to deal with this problem.
Hi Skippy,
I had my canopy crack at around 300 hours, no real cause. I had not touched the screw that the crack propagated from.
I stop drilled with a no. 60 drill (smallest I had) and no issues since. Now at 370 hours.
Thanks for that.
My crack is emanating from within the left (opening) side, sandwich structure, of the canopy.
Similar to yours ie hairline, probably double the length.
I have been recommended to use ACRIFIX 105. and NOT drill.
ACRIFIX 105 is sold by Acrylic Technologies Australia https://acrylictech.com.au/about/
I think Acri-Bond 105 was meant.
It looks like a standard solvent adhesive. Give it a try, I’ve read of the use of such on the Vans Airforce forums, and I’ve been contemplating trying it myself on my canopy and windscreen. Or try their UV cured water-thin adhesives.
Weld-On 3 is a common US brand. In theory, it will wick into the crack and bond the edges together.
Yes ACRI - BOND 105 - my apologies
I have effected a temporary repair, pending replacing the Perspex canopy with one molded by Ian Link ( sailplanecanopies@gmail.com) should be far superior to the Sonex offering.
Ian has advised the following method for producing a temporary repair:
Stop drill the crack using the smallest drill you have and drill one millimeter in front of the furthest visible point of the crack .
Cut strips of lightweight woven fiberglass (I used left over wing covering fabric)that are wide enough to bridge the crack ,
Lay them over then saturate them onto the canopy using the glue nozzle to directly onto the surface of the fabric so it injects glue through the fabric and wets it out.
Repeat on inside of canopy.
Wait 24 hrs before stressing the joint.
Note: Superglue does not damage Perspex.
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I did some test pieces, trying both Superglue and Weldon 3 with light glass tape, and couldn’t detect a noticeable difference in the way they failed.
I also found PlastiFix kits from Polyvance, that looks like ground acrylic wetted out with liquid monomer. http://www.youtube.com/watch?v=UzEIXYZKiLI PlastiFix Kits – Polyvance
I found 4 of the screws that hold the plexi to the frame had fallen out. I wondered why I hadn’t used a bit of Loctite on them when I built the canopy. I installed new screws with a dab of Loctite. The next day I went out to the plane and found four 2 inch cracks in the canopy. It was then that I remembered why you can’t use Loctite anywhere near the canopy. I stop drilled the cracks and masked off the sides very tightly and put a dab of crazy glue on them as well. Still good a year later except for the frustration everytime I look at the cracks.
