Very true, after sanding the pistons down to fit the QT nice at room temperature, I popped the QT with piston installed outdoors (WI winter) for a couple hours (a chest freezer works almost as well for summer building too BTW). The piston might as well have been welded in at that temperature! Quite a bit of 120 grit power sanding to get the piston sliding nice and happy at both temps. Moral of the story, better to do this at home then at the launch.
Also, keep in mind that if you are flying Quantum Tube, the coeeficient of expansion is different than that for the phenolic piston. This means you may need to be prepared to sand the piston down on the field on a very cold day.
I also install my pistons "upside down" with the bulkhead towards the ejection charge. Just like the pistons in a combustion engine. I'm sure someone will chime in with..."The Link"...and agree or dis-agree opinions. There's also A LOT of other ejection methods that work just as well if not better and require little or no modifications to the kit you're building.
As far as venting the airframe goes, why not? A 3/32" hole drilled on the rail guide side won't be too obvious and can't hurt for a cert 1 flight. Nothing worse than mid flight pre-mature separation.
The BP, put it all in and shake it down so it makes contact with delay grain. They don't supply enough to break a rocket as far as I know.
Last edited by talkin Monkey; 10th July 2009 at 03:14 PM.
-TRA 11694 L2-
"...look around you, can you fabricate some sort of rudimentary lathe?..." Guy, from Galaxy Quest