Duel-deployment concern

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gcanroc

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Last November I fail to achieve my Level 1 cert when my PML Spitfire went ballistic into the ground after launching on a Aerotech H283ST motor with a non deployment of the nose cone and parachute. Through the winter and through much of the COVID lock-down, I constructed a ebay which contains a Eggfinder Quantum. For me to salvage the rocket, I had to cut off 7" from the top of the body tube where it was split by the nose cone when it "arrowed" into the soft ground. This leaves me 29" of body tube to have the PML piston, shock cord, ebay coupler and parachute packed together. There will be only about 1-2 inches from the top of the shock cord above the parachute to the bp charge well when it is all put together. My goal is to have a redundant deployment system of the motor deployment firing and/or the ebay firing for my Level 1 cert.

Questions:

1) Is there a recommended clearance between the BP charge well and the packed shock cord/parachute.
2) Do you only use a "plugged" motor when using a ebay duel deployment BP system?
3) Should the motor ejection charge fire first and fail, is there a possibility of the ebay charge dissipating through the rocket because the motor is not plugged if I were to eliminate the piston. Would the packed parachute be enough of a blockage to contain the pressure build-up.

To make more room I can eliminate the piston. I'm anxious for our flying season to start. Thx for the input in advance.

Geoff
 
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Nytrunner

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1) I know of no recommended clearance, just be sure the parachute and lines are protected by nomex/wadding. Harness should be protected as well up near the charge (there are nomex harness sleeves, I just fold a strip of ductape over the line)

2) Plugged motor not required, If the delay is long enough, I leave it in as an emergency measure if the apogee charge fails (of course plugged motors require E-deploy, and if the delay is too short then I remove the charge and let the electronics do it)

3) The touch hole in the forward closure is so small it shouldn't cause a problem. Folks often drill a vent hole in the side of the airframe and that doesnt hamper deployment either.
 

gcanroc

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Thank you for the your advice. If you have ever had a rocket ballistic on you, one deployment charge is never enough. 😉Quick note: above I was using the word “shroud lines” I ment “shock cord”. Edit made

Geoff
 
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