Canopy damper warning

[messydeer]

Hey, guys!

I'd like to report on what's happened to my canopy since I installed a damper upon completion of the airplane about three years ago. The damper worked fine (for details see Sonextalk), dampening the closing and the opening. But the first problem showed up about a year into flight, maybe 60 hours on it. The aft bow cracked completely in two, a couple inches below the crossbar on the right side. I figured this was from me tugging and pushing on the canopy against the damper to get it to close and open. Didn't seem like it was much, but there was a pretty good lever there. The canopy didn't crack and I inserted a solid 3/8" rod, plus dialed down the tension on the damper. Fast forward 100 hours and the bow cracked in the same place, right through the solid bar. This time I didn't get lucky and am repairing a 4" crack with Weld-On #3. I'm certain it cracked from the damper causing pressure and plan to switch to something else to keep the canopy open, which could be the simple and light wire Sonex recommends.

Cheers,
Dan

[gammaxy]

Wow. That's pretty surprising. Thanks for sharing

I'm not sure how many people have had problems with the recommended wire, but Kip switched to a pilot chute lanyard.

http://sonexbuilders.net/viewtopic.php?f=33&t=498

I did something similar with shock-absorbing nylon webbing. I just prefer the aesthetics of the webbing over wire and though that the canopy blowing open against webbing might be gentler than against wire.

[sonex892]

Hi Dan. That's no good. More than likely the strut was too powerful. Any photos of your install?
Mine is in its 5th year now with no sign of damaging the standard canopy frame.
Steve 892

[sonex892]

Dan. When I first read the post Warning about the use of gas struts, I was curious to see what your arrangement was. Thanks for letting us know your version didn't work out. Thankfully my setup is a totally different design. Such as I used a smaller gas strut, different attachment locations and brackets etc.

When experimenting, prototyping and designing our own modifications. FaiIure is the chance we take. Its part of the joy and frustration of experimental aviation. I still believe the gas strut is a better option than the sonex string. It does one thing very well that the string cant do. It will hold the canopy open on a windy day.

I think I found a photo of your gas strut on sonextalk taken during setup. I couldn't see any on your completed aircraft. So I am guessing this was the final location


My arrangement shown below. The angle bracket under the crossbar is needed to hold the canopy in alignment when closed


Steve 892
VH-ZSX

[billmaxmcw]

I have used a gas strut for 3 years, and have had no problems. It is a 15-lb. strut, 7 inches closed, 10 inches open, ball joints both ends, from McMaster-Carr.
Bill

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