Guys,

I had a gust of wind blow my canopy down just as I was getting in my 601XL and the rear corner glanced off my shoulder.  The plexiglass cracked about 8" from the bottom edge extending vertically.  I don't have a pic, but in the attached .jpg I drew a representation (albeit on the opposite side) of what the crack looks like.  So far I have only stop drilled the end of the crack.  I would like to put a doubler inside the crack, but, as a compound curve, I am afraid of adding more stress to the plexiglass.  I see several adhesives on the market (Weldon 4, Acrifix, Plastifix), but some of these are very low viscosity and this is a vertically oriented crack

Any advice from those who have tackled a repair like this would be appreciated.

FYI, I already had the 60# McMaster-Carr canopy pistons, but noted they had been weakening.  I just ordered a replacement pair.

Dave Gallagher

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i have similar crack, stop drill at top. find scrap plexiglass and heat with heat gun till it matches inside curve; then adhere with acrylic cement " scigrip weld-on #3 adhesive" allow to dry and carry on. Another way stop drill at top, drill holes across from crack for a shoe tounge effect, lace up with safety wire. or apply duct or aluminum tape on inside and outside (ugly but works if crack stop drilled at top) I used the thicker 2 part weldon (very expensive....short shelf life) to fix for about a year with out doubler, eventually failed so now am using method listed first

The Vans Air Force forum has a ton of info on repairing canopy cracks. You can see what works and what doesn't. You can sign up by answering a simple Vans aircraft question that you can get the answer to from Google.  

I used this guys process to fix a similar crack in my canopy about a year ago and it's still holding strong. You can see the repair, but it's not that noticeable.

https://www.polyvance.com/pfxcanopy.php-1

I have completed my canopy crack repair using the Weld-on #3 as recommended by Christopher.  It is not pretty, but I think it will work. I bought some acrylic sheet from Menards, .093" thick, I believe.  I roughly shaped the acrylic to match the curvature of the crack to keep the width down and hopefully make it easier to shape and press into place.  I used a heat gun to bend the repair patch to just less than the canopy curvature.  My thought was that if I pressed on the middle of the patch, the ends would help clamp down themselves. I masked the canopy around the patch area to help keep Weld-on runs from softening areas I didn't want it to.  I brushed the canopy and patch with Weld-on #3 and held it in place for at least 4 or more minutes.  The instructions says it's fixture time was a scant 2 minutes. I have only one lightweight clamp that had jaws long enough to help hold the patch in place, so I used that to assist my hands. Unfortunately, you can see where the clamp was because some of the Weld-on crept under the feet and left a witness mark.

The Weld-on #3 seems even thinner that water, so it runs all over the place.  Need to have rags on hand to clean up runs ASAP.  The negative of being so thin is that there are no gap filling properties.  There needs to be a complete contact in order to fuse.  The positive of being so thin is that it has a lot of capillary effect.  The product came with a little bottle and syringe needle.  After the initial set-up, I notice a lot of areas where it didn't seem that good fusion took place.  I was able to use the syringe and watch the product wick into those areas.  I now believe I have about 80-90% fusion of the patch to the canopy.  The next time I am at the airport I will try to see if I can get anymore Weld-on to wick into voids.

Dave Gallagher

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