- This topic has 13 replies, 7 voices, and was last updated 17 years ago by
edward.
edward.-
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John
A clarifying question for you all…I am finishing up my scratch built L1 cert rocket for Oktoberfest and would hate to be embarrassed.
Should the piston sit all the way towards the bottom of the airframe “on” the ejection charge/top of motor or should a centering ring with a very wide mouth be used to hold it higher up? My thinking is to use the CR approach to shorten the distance the piston has to travel reducing the chance for a jam and making the piston last longer.
This is a straight forward rocket, no bays. Just a 34″ x 3″ airframe with motor mount, nosecone, and recovery system. Thanks for the help!
John
edward
I always put the piston right against the charge. They travel just fine when you keep it clean. What airframe material is used. I also have my piston sitting in my rocket so that it looks like a drinking glass – bulkhead on the bottom and open on top.
Edward
John
Thanks Edward! This is almost all LOC components (paper tube), piston using nylon webbing with a nomex sleeve attached via a metal D-ring to piton bulkhead. The webbing is epoxied to the 10″ motor mount through 2 of 3 centering rings. I haven’t actually attached the piston to the webbing yet or epoxied the bulkhead into the piston so your options are open to me. The “cup” shaped piston seems very counter-intuitive to me though I’ll admit while certainly not denying your experience of which I have none! 😉
Assuming this L1 attempt is good I plan to pick up my first G10 kit at the event.
edward
There is a site that says it is the better way because of stability but I believe Doug G. says it is bunk (I can’t confirm/deny if it is, but I’ll go with Doug). It works for me mainly because it give me extra room to pack everything in. The other way eats up some space. This way I have a ‘cup’ shape to start packing everything in. I also make sure that I ground test with my pistons. I like to get the piston out and about 5-6 from the end of the rocket put a ‘stop’ on the shock cord so that the piston stops and the momentum from the parachute keeps going throwing it out. Has worked every time for me since I’ve started doing it. I also like to size my charges so that all the shock cord gets straightened out.
Edward
John
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