[RocketsNW] Parachute protection options

[Azinger, Fred]

Don't forget to "invert" the piston -- skirt forward.
Think of an automobile piston on the power stroke....skirt away from the
charge...
Yes -- when coefficients of expansions are matched, pistons work well.
 

-----Original Message-----
From: rockets-bounces at rocketsnw.com
[mailto:rockets-bounces at rocketsnw.com] On Behalf Of Mfreptiles at aol.com
Sent: Monday, November 03, 2008 8:35 PM
To: rockets at rocketsnw.com
Subject: Re: [RocketsNW] Parachute protection options

I think Steve is on to something in certain situations.  
 
Taking Steve's advice, I've built a piston for my 38mm all aluminum
rocket.  
The piston is machined aluminum and slides really smoothly within  the 
aluminum airframe and won't bind because the piston skirt is several
calibers long 
and the piston and airframe is the same material.  My  previous problem
was 
the bulk of the recovery gear wrapped with nomex.   Even then, my kevlar
harness 
was exposed to the ejection gasses and would  degrade after a few
flights.  
With the piston, there is less bulk to pack,  and the harness above the
piston 
stays like new.  The kevlar harness  section below the piston will
degrade, 
but since it is shorter, less $ to  replace.
 
Now if you asked me if I believe in phenolic pistons in cardboard, or  
plastic airframes........forget it! :)
 
Mike F.
 
 
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