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how to crack a canopy

C-GRVT

Well Known Member
At the risk of reviving unhappy memories, and in the spirit of wishing to benefit from the unhappy experience of others, I want to ask those who have cracked their canopy during install exactly how they did it.
My name is Bill and I cracked my canopy.
Last summer I got as far starting to trim the uncut slider canopy edges (the very first step!), had clamped the canopy to a tabletop, started to cut the thing, the canopy slipped and fell off the edge of the table enough to put a twisting weight on the remaining clamps and freshly and partially cut edge, resulting in an awful cracking sound and a ten inch crack.
Fortunately the crack was only in the windshield portion, and Van's canopy supplier - great people to deal with - very kindly supplied a "windshield only" replacement for far fewer dollars than a new canopy.
By the time I got back to thinking canopy the weather was turning cold, but here it is summer again, and time to finish it.
I am sure that I am the only one who has cracked a canopy without even drilling a hole in it - but how have others cracked the canopy?
Bill Brooks
Ottawa, Canada
RV-6A finishing
 
My name is Chad and I cracked my canopy!
I was putting spacers between the frame and the canopy and forgot that I had a cleco in about 12 inches away:eek: CRACK KILLS. Got my replacement from Todd's. I installed the next one without drilling any holes just sikaflex, which is a much better method IMHO
 
OK I'll chime in....

I haven't fessed up on the forums yet but I cracked my canopy about four weeks ago.....I'm still getting over it.

WARNING:This is one to watch out for.....

My Tip-up canopy was complete and installed. I had removed my gas struts on numerous occasions and the retaining clip on the lower LHS had become slightly widened. My attach bracket was also slightly short which was causing the bottom of the gas strut to touch the fuse rail when rotating. The combination of both resulted in a loosening of the strut on the bottom knuckle.

I was working in the cockpit and bumped the strut sideways (ever so lightly). The gas strut jumped of the knuckle and the canopy came slamming down with me under it.

Before I knew what was going on it was too late.

The remaining strut skewed the canopy sideways and the rear corner of the plexi came down and struck the roll bar as it closed.

Sheared the corner off (approx 3 inch by 1 inch long).

I was shattered (excuse the pun). Almost shed a tear. My bloody plane was finished, painted and ready to fly.

The upside was that it was cold in the hangar and I think I was lucky to get away with a smallish chip off the corner for this reason. It could have been a disaster and cracked the whole canopy clean across the top.

I will be installing small black aluminum covers on both sides to conceal the repair...can't face the thought of re-building the canopy for obvious reasons......

If you have a tip-up canopy BEWARE of this scenario - it could happen to anyone quite easily.....
 
The remaining strut skewed the canopy sideways and the rear corner of the plexi came down and struck the roll bar as it closed.

Sheared the corner off (approx 3 inch by 1 inch long).

This happened to me on my RV-9A, without any strut failure. In my case, it was a well-meaning bystander trying to close my tip-up canopy for me when I wasn't looking. It came down crooked and broke a 3"x1" piece off one corner.

I glassed some foam into the affected area and covered it with a targa strip... after it was all painted, you couldn't tell that it wasn't done that way on purpose. In fact, if I ever build another a tip-up canopy, I'll probably just do this "mod" in advance so the plexi won't have a chance to be broken!

mcb
 
I cracked mine screwing down a mounting point and the edge of the threads caught the edge of the hole. The holes were overdrilled in size but the plexi had shifted ever so slightly. Fortunately, I was able to cover it with a fairing.
 
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Cracked canopy

Hi,
My name is Michael and I cracked my canopy.

I waited for warm weather, like in the mid 80's. Someone had suggested using a vibrating saw--like a cast saw. I used a Feinmaster and was trimming away the excess when I got a two inch crack up the side of the canopy right in the middle. Rats. Got a new one from Todd. He suggested that the intense vibration of the saw might have done this. I cut the new one with a grinder and the wheel supplied by Vans. No problem.

Michael Wynn
RV 8 Finishing
San Ramon, CA
 
Canopy

Hi, my name is Pete and I cracked my canopy:(

My story isn't as bad as some, but it was still cracked. When I started drilling countersunk holes in the top spine of the slider, the countersink bit made several small cracks coming out of the drill holes.

I ended up drilling the effected holes out to a larger diameter, and moved on. I also bought a 'Chatterless' countersinking bit from Avery tools. It didn't have a pilot and worked much better on the remaining holes.
 
Hi,
My name is Michael and I cracked my canopy.

I waited for warm weather, like in the mid 80's. Someone had suggested using a vibrating saw--like a cast saw. I used a Feinmaster and was trimming away the excess when I got a two inch crack up the side of the canopy right in the middle. Rats. Got a new one from Todd. He suggested that the intense vibration of the saw might have done this. I cut the new one with a grinder and the wheel supplied by Vans. No problem.

Michael Wynn
RV 8 Finishing
San Ramon, CA

This got my attention. I've made several long practice cuts using the Harbor Freight version of this saw with good results. I feel that I'm ready for the big cut. Were you plunging the saw immediately through the Plexi or were you using several small passes?

Regarding the Van's supplied cutting discs, did you find that yours were potato chipped? Both of mine are so they wobble when they spin. I tested mine on a Black and Decker RTX which got pretty warm. I could only use a lower speed to avoid the resonance of the wobbling disc. I also performed test cuts using an electric drill which cut pretty well but occasionally got stuck within the Plexi which I didn't like at all.
 
Hi, my name is Lars and I cracked my canopy.

In my case, a slider. I had it lying upside down on a padded workbench, so I could do some finish work on the frame. At that point I had bonded the acrylic to the frame with Sikaflex and was about to start work on the skirt. We had too many workbenches in close proximity to each other, and I was squeezing between them to get to my toolbox while carrying a pair of vise-grips. I tripped slightly, then had a ringside seat as the vise-grip slipped out of my hand, sailed through the air and did a one-point landing on the acrylic just above where the pilot's head would be. Made a nice 6 inch diameter star crack. I was beyond being in shock. There was nothing to do as far as a repair, so I grabbed a razor blade and went to work cutting the plexi off the frame. I found a local builder who could spare his canopy (I bought him a replacement), ordered some more Sika, and went to work. What took me almost 2 months the first time I managed to do the second time in 6 days. And I'm more careful around my canopy now, to say the least.

Kelly, if you can spare the time you are welcome to c'mon up to KDWA and try my pneumatic die grinder with a cutoff wheel to cut plexi. No doubt there are lots of ways to cut the stuff, but I found that to be easy and extremely controllable. My hands are back in business, more or less.
 
Just a quick tip

For those unfortunate enough to have this happen, Sikaflex can be softened with careful use of a hair drier or heat gun on low heat setting. The Sika can then be cut using something like a length of safety wire or thin paint scraper. It's easier if you have a helper to work the heat gun along just ahead of the cutting tool.

Keep in mind I am talking about a moderate heat only, not paint blistering or acrylic melting hot! Warm to fairly hot to the touch is more than adequate and don't be in to much of a hurry. With a bit of careful experimentation you will have that broken canopy in the rubbish bin in no time:eek:

Clive Whittfield
Auckland
New Zealand
RV6 - Engine started for the first time
 
ouch!

thanks guys for sharing. My canopy crack is just a tiny little thing, placed there to make me worry if nothing else, ( one of theose 'screw hole migration cracks' )
Now that I see there are a dozen cracked canopies out there, would someone PLEASE clamp it to the bench, get under it, and try to 'break out' like you just flipped in a corn field and gas was dripping on your leg!

just looking to put to rest some of the 'canopy cracker' tool controversies:)

thanks for letting me share your pain!
 
Now that I see there are a dozen cracked canopies out there, would someone PLEASE clamp it to the bench, get under it, and try to 'break out' like you just flipped in a corn field and gas was dripping on your leg!

just looking to put to rest some of the 'canopy cracker' tool controversies:)

If I do crack mine, I was planning to do exactly that.

We shall see... ;)
 
Anyone interested in buying a cracked RV-4 canopy - Cheap?

But seriously, I cracked mine by working on the opposite side from where the crack occurred. I had the right side cleco'ed on and was adjusting the left side. 2 problems - winter - temperature in the teens, (Hangar temp in the
50's), and "racking" the canopy although very slightly. I always pre-heated the canopy by placing a small space heater under it for a half hour or so before I worked on it. This particular night I had the "gottagetitdone" fever. working for 3 hours without re-heating the plexi. As I said, I had the right side cleco'ed and shifted the left side very slightly to the rear to adjust the fit - and -CRACK- my heart sank - I said every curse word I knew, then went in to mentally beat the dickens out of myself. Bought a new one from Todd's, and am still looking fearfully at it.
 
hum---

I've been reading about the cracked canopies, due to fabrication accidents, and I was just wondering if there was a better way to go instead of plexi. This isn't my area of expertise, so I was looking at the "what if" scenario. In-flight vibration cracks, etc. Anyone have any solutions?
Tom
 
canopy materials

Well Tom,
since no-one else has commented, I can say this about plastic windshields.
We went thru at least 4 windshields, and several side canopy panels on our 1972 Jodel f-11 'slider'.
My Dad first cold wrapped the acrylic 'plexiglas' windshield, which gave good optics and scratch resistance as they have since the 1930's (perspex I believe.)
eventually, the stress from the bend was seen at the attach points, screws, and it started cracking at these points. Heck, just cleaning it probably caused half the stress!
The new windshield was lexan - polycarbonate, so that this stress cracking would be avoided. It attracted dust like a magnet, was easy to scuff, and after a few years yellowed a bit, ( all 3 of which have been addressed to varying degrees with modern lexan).
... the worst part was, at the bends, the optics were quite wavy, and as it aged, some kind of stress riser appeared as a sliver-like lines in the bend area. Not bad on the side you were looking thru, but if you looked across at the co-pilot's side, or the sun was just right, it was very hard to see thru.
so the moral is????....each material is designed to do one or two things well, at the expense of the other.
New acrylics come in 'high impact' versions to minimize cracking, just as polycarbonate comes with UV inhibitors and surface hardening treatments.

Most polycarbonate has a high moisture content, and does age, compared to acrylics, becoming more breakable.
Personally, I don't think I'd use a lexan windshield, just due to the maintenance, and inadvertent scuffing by well-meaning people with rags etc.
If your ship is hangared all the time, and only you touch it, you could get away with it, and have a pretty decent, bird-proof windscreen!
 
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