Extremely small space for parachute

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Performance nut

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Hey all. Finally ready to build my HPR min diameter bird and had a concern.

Rocket: 54mm min diameter. The nosecone coupler is the e-bay, the biggest engine will almost literally rest on the bottom bulkhead. The volume between the nose cone tip and the top e-bay bulkhead will house the shock cord, the parachute, and the ejection charge. Shock cord is some really nice Kevlar with a swivel on it. Parachute hasn't been decided yet.

Problem: The fiberglass is thin enough to see through it and I have to say, it is tight as all heck. Unfortunately the NC fits extremely snug on the coupler (I have to use some force on it). I believe that to be by design to minimize drag separation as the NC is quite heavy compared to the rest of the rocket. I'm still thinking sheer pins are necessary but I'm concerned the amount of force that is required to break a sheer pin strong enough to prevent drag separation is going to burn all of my recovery.

Thoughts:
  • The shock cord is Kevlar, so I'm thinking I'm good there.
  • The parachute... I'm thinking Nomex big enough to wrap all the shroud lines and parachute will be enough but it adds bulk. Too much in fact. So I have to loose some shock cord or go with a smaller parachute.
  • Its carbon fiber BT with a fiberglass NC so I'm not worried about breaking it. It does have a rather hefty aluminum tip on it though and I'm also considering going with a Max-Q fin can as I plan on pushing high mach with it. Coming down hard will definitely leave an impression on anything it hits.
  • The other thought is pack the parachute and Nomex with a chute release (that has a protector on it too). The chute release generally tightens the parachute up. If the ejection charge burns the rubber band, I'm still going to get a deployment albeit much sooner than I wanted.

I feel this is going to be tough on my parachutes or I'm going to need to science the ... stuff out of this. Anyone have some tips? Found tons of threads on deployment charges but nothing with extremely small volumes.
 
What kind of weight are you looking at? You could ditch the Nomex and just use dog barf?
 
Rocketman kevlar parachute....no nomex or dog barf needed

Shorter than usual kevlar shock cord...you don't need to worry about zippering

Shear pins without a doubt ...i wouldn't trust a nosecone to stay on without shear pins
 
A lot of folks oversize their kevlar and hardware. How are you planning to attach it, have you got a ballpark total weight, and is there motor eject involved?

In a typical burrito arrangement there's a lot of wasted overlap. Consider something flower shaped that folds up like a shotgun cup with minimal overlap.

Bear AltiDuo SMT with a Prairie Twister Cable Cutter is the most compact dual deploy arrangement I know if.

And finally, drag-per-gram-per-cc it's Fruity Chutes all the way, but you'll pay dearly for the privilege. Good luck!
 
I get a 36in.Topflight in my 54mm airframe head end deploy........

DSCN5794.jpg

see here as to all needed info on how too.

Don't forget to vent the nose cone.....it's actually the payload now & you don't want it popping off prematurely.

https://www.rocketryforum.com/showt...t-Drag-Race-35-00-build&p=1594288#post1594288

Use either 1/4in or 1/8in tubular Kevlar for shock cords.
Don't put cord in burrito, place ribbon folded on front half of burrito with bulk, in space in front of burrito.
 
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Standard Topflight.
No issues...just proper folding & placement of shock cord to maximize space in NC.

You probably won't get it in, the first nor 3rd or 5th try. BUT eventually you can figure it out & all will fit quite nicely & not be crammed in tight.
 
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I manage a 54" Spherachute in nomex blanket with Kevlar line in a 54mm airframe, tube length about 11 inches going from memory. The deployment charges and eye bolts suck up some of the available length. It is a compression fit held together with shear pins and uses a moderately hefty charge to guarantee deployment.

A lot of it is how you pack.

Gerald
 
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