Hi Guys,<br><br>I am building a Sonex aircraft http://dkoelzer.murkworks.com/. This design has a Plexiglas bubble canopy which hinges to the side. In the event of a roll over accident I would not be able to open the canopy normally. Short of a fireman's axe is there any good tool which would help me break out of the cockpit. <br><br>Some veterans have mentioned that they were taught to score the window with their sheath knife and then hit it with the butt of the knife to break the window. Is this really effective or is it an old-sergeant's tale?<br><br>David Koelzer