Canopy Cracks

gear1 · #1 03-20-2013, 09:54 AM

About a year ago a major crack developed in my RV8 canopy on a cold morning (about -10C) departure from Truckee CA at the "standard" locatation at the rear canopy bow. With the help of Jay Pratt (Borrowed Horse) and Danny King (Beautiful Doll) I installed a new canopy. Danny had already made two canopy replacements due to cracks, and suggested that the concept of using rubber grommets in oversize rivet holes in the plexiglas might work. The idea is that the grommets will allow some relative motion between the canopy and canopy frame during temperature changes. The grommets were made from RC model silicon fuel hose, sliced to canopy thickness. Now, a year later, Danny's idea seems to be working. Flying out of Pagosa Springs, CO, this winter we have experienced temperatures in flight as low as -12C (10F), with no canopy cracking.

Thanks, Danny!

Ironflight · #2 03-20-2013, 11:42 AM

I think you mean "Danny" King, unless he is now using an alias to avoid a posse....which, with Danny, is not out of the questions.

I did his grommet trick on my replacement as well, and think it is a grand idea. Only time will tell if it works as well as it seems like it should.

gasman · #3 03-20-2013, 12:03 PM

Progressive slots would really be the answer. But very difficult to do.

gear1 · #4 03-21-2013, 06:18 AM

Thank you, Paul. I have edited my post, with a very red face!

David-aviator · #5 03-21-2013, 06:36 AM

Seems like a common area of cracking is the "rear canopy bow".

Something must be going on in that area when in cold temperatures, perhaps the frame is changing shape with temperature change?

Has a canopy cracked in that area using Sikaflex?

Ironflight · #6 03-21-2013, 09:32 AM

Quote:

Originally Posted by David-aviator

Seems like a common area of cracking is the "rear canopy bow".

Something must be going on in that area when in cold temperatures, perhaps the frame is changing shape with temperature change?

Has a canopy cracked in that area using Sikaflex?

I actually think that location is highly stressed because of the change in diameter of the frame tubing - there is a weld bump at that point, and the canopy gets pulled tightly across it. Any imperfections in the canopy edge or holes in that area are more likely to let go when the thermal gradients build up.

At least that's my theory.