Canopy Break out tool

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

With plexiglass the scoreing followed by impact will be mostly useless unless the plexiglass is quite thin or you "score" through most of it (which will be much more like cutting). This method would work admirably with glass. <br><br>An option might be a battery powered dremel tool pre-loaded with the correct cutting wheel. It is small and could be taped / velcro'd to the canopy / dash and be perfectly capable of cutting through most plexiglass. <br><br>I am unfamiliar with the aircraft specifics but if you craft is upside down on a plexiglas bubble and you break the bubble is there sufficient room within the cabin for you after the aircraft settles down on the broken shards of the canopy? Seems like a bad situation whatever.

Hi,<br><br>Here is a view of my plane under construction http://dkoelzer.murkworks.com/canopy/canclosed.jpg<br><br>The forward windscreen is make from Lexan while the bubble canopy is Plexiglas. In the above picture the forward part of the windscreen still has the white plastic covering on the Lexan. Here is another view with the hinged part of the Plexiglas canopy opened. http://dkoelzer.murkworks.com/canopy/canopen2.jpg<br><br>You can see that the metal hoop of the windscreen and turtle deck of the aft fuselage will act as roll bars so I won't be pinned under the overturned fuselage. I should have 2' of space to crawl out from under if I can make a hole in the canopy. <br><br>I inadvertently cracked my first Plexiglas canopy during installation and it surprised me how brittle Plexiglas really is. So score and crack method seems theoretically possible to me but I would feel better if I knew someone had first hand experience.

Well.... Looks as if you will be safe from crushing. The flexion stress from the weight of the plane should assist on the score and Whack method. If you cracked your first one then you should have material around for experimenting. Take a curved piece, place it curve down just as it would be in the hypothetical emergency, place a 2/4 with a bunch or weight on it accross the upturned edges, then reach in, score it and give it a whack. Protect yourself from the colapse as this experiment doesnt have the roll-bars. Let us know about your success.

Try some of the dedicated windshield punches. They are small and very effective. In the Coast Guard we had boat and aircraft axes and our personal knives. We had to smash through plexiglass, wood and fiberglass, cut the occasional line or fishing net. I went through the AF survival knife, an early British MOD4 and eventually settled on a German Linder sheepsfoot with detached marlinspike ( The sheepsfoot blade was legislated into existence to stop seamen from knifing each other well before vulnurable liferafts.) The marlinspike proved very effective at punching starcracks into plexiglass with a following blow from the butt or bladeback ( depending on how scared or pressed for time we were.)

It is my understanding that the USAF "survival" knive has what pass for saw teeth on the back so that it can be used to saw thru plexiglas or the aluminum skin of an aircraft. I never got a chance to use mine on those materials, but just for the heck of it I sawed a 2x4 in half with it, and it worked pretty good for that. I did snap the tip off while trying to husk a coconut tho...<br><br>There are many knives available with really effective saw teeth, you might consider something along those lines...