My presumption is that it came from the defrost.  When I built my plane, I put in a duct system beneath the glare shield that directed hot air up to the canopy.  In retrospect, I think I made it too effective.

I used to leave the defrost on long after the canopy had cleared.  I had a long trip “through the soup” in Western Maryland, Pennsylvania and Ohio during which I believe the defrost was on the whole time.  Immediately after that leg the canopy showed some significant cracking/crazing. 

Now I switch immediately from defrost to heat (or off) as soon as the canopy is clear.

Doug, Where did all of the heat that damage your canopy come from?

Larry Eversmeyer
still building Legacy





Yes, I need defrost – I fly out of KMTN in the Baltimore area.
 
I would suggest judicious use of defrost.  Recently had to replace my canopy due to damage from excessive heat.