Performance nut
Well-Known Member
- Joined
- Nov 30, 2012
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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:
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.
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.