PML STRIKER STUFFER TUBE DEPLOYMENT

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hball55

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Has anybody flown the PML Striker using the stuffer tube piston deployment method that comes stock with the kit? I can’t get past the fear that the parachute will end up inside the hollow nosecone. I have tested the rocket by blowing in the motor tube and the parachute does indeed end up inside the nosecone, and can only hope that the extra strength of a BP charge will blow the nosecone further so that the parachute will be pulled out of the nosecone when the shock cord becomes taut.

I have always had fears of the ejection charge mounted on the coupler bulkhead of dual deploy rockets will force the parachute down into the lower body tube, but that has never happened in my experience, so perhaps I shouldn’t worry.

Anyway, has anybody flown the PML Striker, and what were your experiences?
 

MikeyDSlagle

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Does the stuffer tube run into the nose cone? Not familiar with the setup.

Either way, many of us fly rockets where the only room for a chute is in the nose cone. I've never had one fail.
And all of my short rockets have electronics in the nose to blow at apogee and they all blow the chute farther down into the airframe, and they always come out. That's not quite the same but it is similar.

You could however:
Rig the chute closer to body tube rather than the nose cone and go ahead and stick the chute in the nose cone, leaving the harness below it free. That way the nose cone doesn't have to stretch the harness completely before the laundry is free; not too close though or it may not come out at all -- ya know the whole half deployed chute stuck in the airframe deal.
Or put a ring/plate in the nose cone to prevent it from going in there to begin with.
Extend buffer tube into nose cone so it will blow it off first and drag the laundry out of the body tube.
 

hball55

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You’d have to be familiar with this rocket and the PML stuffer tube. The stuffer tube fits inside the main tube and the motor tube extends into the stuffer tube rear and seals it so ejection gases don’t escape. The stuffer tube does extend far into the nosecone, so this is not a rocket that you can install electronics. The body tube is 4” and the stuffer tube is 3”, with a 3” piston inside the stuffer tube to aid ejection and protect the chute from ejection gases.

I am hoping somebody has flown this creature and can tell me it does in fact work. Though, I will fly this rocket as soon as my clubs start flying again and I will find out for myself.
 

afadeev

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Has anybody flown the PML Striker using the stuffer tube piston deployment method that comes stock with the kit? I can’t get past the fear that the parachute will end up inside the hollow nosecone. I have tested the rocket by blowing in the motor tube and the parachute does indeed end up inside the nosecone, and can only hope that the extra strength of a BP charge will blow the nosecone further so that the parachute will be pulled out of the nosecone when the shock cord becomes taut.
I haven't built Striker, but have flown 4" PML BumbleBee, and your fears are unfounded.

With the larger rockets, the chute is pulled out of the airframes by the momentum of the heavy nose cone (NC). In your Striker, NC gets expelled by the piston (which, in turn, is propelled by the ejection charge), and pulls the harness and the chute out with it, away from the airframe.

The same logic applies if you skip on the PML piston arrangement, and use Nomex blanket to isolate ejection gas particles from the chute itself.
This will work just fine on rockets with reasonably sized interior airframes, like Striker.

HTH,
a

P.S.: If you have a much larger airframe areas unconstrained by "stuffer", "cannon", or "extended motor mount" tubes, adequately pressurizing that larger space with ejection charge might become an issue.
 

crossfire

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I built mine without stuffer tube. I see no deployment issues without stuffer tube. Not a lot of tube area between MMT and nose cone.
 

MikeyDSlagle

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You’d have to be familiar with this rocket and the PML stuffer tube. The stuffer tube fits inside the main tube and the motor tube extends into the stuffer tube rear and seals it so ejection gases don’t escape. The stuffer tube does extend far into the nosecone, so this is not a rocket that you can install electronics. The body tube is 4” and the stuffer tube is 3”, with a 3” piston inside the stuffer tube to aid ejection and protect the chute from ejection gases.

I am hoping somebody has flown this creature and can tell me it does in fact work. Though, I will fly this rocket as soon as my clubs start flying again and I will find out for myself.
Ahhh
Gotcha
I understand now. I was thinking the stuffer tube was about the same size as MMT and all the laundry sat on top of the stuffer below the nose cone. Didn't realize the piston and laundry actually went into the stuffer tube, effectively making a chute cannon. I suspect if it didn't work, PML would have changed it up by now, but I now see your concern.
 

hball55

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Ahhh
Gotcha
I understand now. I was thinking the stuffer tube was about the same size as MMT and all the laundry sat on top of the stuffer below the nose cone. Didn't realize the piston and laundry actually went into the stuffer tube, effectively making a chute cannon. I suspect if it didn't work, PML would have changed it up by now, but I now see your concern.
Yes, I do believe my concerns are mostly unfounded, and yes “chute cannon” is a good description. Also, as you say, the design would have been changed if it was problematic. I wanted to build this PML rocket as designed, as past kits I have modified, but now I see the benefit of leaving out the stuffer tube, as I could then put electronics in the nosecone and not have to rely on motor ejection. Anyway, I can put up with motor ejection with this kit.
 

Tobor

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I did a 29mm motor mod of an Estes Big Daddy in which the parachute is passively deployed from the nosecone. Some build pics (Here) and flight pics (Here).
 

jd2cylman

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I built the PML Lil Lunar Express and it has a 3" stuffer tube. On the first flight, the parachute was ejected straight into the nosecone for a wonderful bellyflop onto a hard dirt road. I've given it up as a lost cause. FIns were too thin to handle a hard landing. Pods acted as fulcrums to break off edges of the fins. Guess I glued the pods on too good...
I'd guess chute placement will play a big role in perfect deployment. Good luck.
 
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