Broken Canopy

[pvalovich]

My -8A canopy doesn't have a single rivit - all Sika. Still, last Oct on one of the first cool mornings here in the desert, I discovered a 4 inch vertical crack on the left side at the rear frame crossbar attach area. That roar you heard in the air was me going through my vocabulary - several times.

Several folks have commented that perhaps I didn't properly smooth the canopy edge - that there was an undetected nick that turned into a stress riser. Can't tell - I stop drilled the thing and have pressed on without removing any of the glue.

So far the only lesson learned is to be very attentive to proper smoothing of the canopy edges. Also, I used fairly widely spaced clamps, not close-spaced clecoes, to hold the canopy against the frame for gluing. Perhaps I induced a stress during that process. But still, I thought the Sika was supposed to flex enough to eliminate such potential stress.

Hadn't thought much about it until reading this thrad. I'm still really upset.

[Mike Zeller]

02-13-12
HI DAN
I HAVE A STOCK VANS CANOPY FOR SALE.
THANKS
MIKE ZELLER
812 305-2568

[chuckwn]

Mine Cracked at about 1100 hours and 8 years of service. It cracked at a rivet hole on the left side behind the rear seat. It was installed per Vans instructions.

My opinion here: I think what we can learn from all of this is that the canopy is not suitable for it's planned service in an RV. It should not be so fragile that it does not survive regular (real life) service. Canopy makers take note.

[N8RV]

As I understand the canopy making process, each is different and has varying thicknesses throughout the canopy. Perhaps you engineering types know whether a thicker canopy would be the solution. Assuming that holes are all adequately deburred, oversized and all edges smoothed, these really shouldn't crack from cold temps and/or turbulence.

My original canopy cracked because I had a brain fart and used the wrong kind of rivet. I stop-drilled the crack and flowed in cyanoacrylate and the crack never progressed, even though I flew it throughout the cold winter months. Apparently, the crack was a sufficient stress reliever, at least in that part of the canopy.

How about it? Should the canopies be a wee bit thicker?

[rocketbob]

Talk to Jeff @ Airplane Plastics in Dayton OH, I'm sure he can fix you up with a thicker canopy. They supply all of Van's plexiglass parts. He won't sell a Van's canopy direct, but they'll tell you how to custom order one thru Van's. I just picked a custom canopy from them not too long ago for my -6 rebuild.

[Danny King]

This thread has pointed out that most cracks happen on the left side of the canopies. I've noticed that the canopy latch, on the left side, pulls the canopy forward as it is latched, causing the entire canopy to list to the port side. I'm wondering if that puts additional stress on the left side of the canopy glass.

In the future, I will side the canopy closed, but will not latch it on cold days. I wonder if I had either left the Doll's canopy open, or simply not latched it last Saturday in front of Jay Pratt's RV Central if we would be talking about this problem now. Any thoughts?

[Louise Hose]

Originally Posted by Danny King

This thread has pointed out that most cracks happen on the left side of the canopies. I've noticed that the canopy latch, on the left side, pulls the canopy forward as it is latched, causing the entire canopy to list to the port side. I'm wondering if that puts additional stress on the left side of the canopy glass.

In the future, I will side the canopy closed, but will not latch it on cold days. I wonder if I had either left the Doll's canopy open, or simply not latched it last Saturday in front of Jay Pratt's RV Central if we would be talking about this problem now. Any thoughts?

The Valkyrie's crack is on the right side, behind the passenger's head.

[billdianne]

Originally Posted by Danny King

This thread has pointed out that most cracks happen on the left side of the canopies. I've noticed that the canopy latch, on the left side, pulls the canopy forward as it is latched, causing the entire canopy to list to the port side. I'm wondering if that puts additional stress on the left side of the canopy glass.

I was told ,or read , that the latch should be adjusted so it doesn't apply any forward pressure to the frame. Pulling the frame forward with the latch racks the frame out of alignment and puts stress on the whole canopy.