From your post it sounds like you are NOT building a boost glider, where the glider portion of the rocket completely separates from the engine pod. Instead I am assuming you want rear ejection but BOTH the body and the engine pod will descend together.
1.You can attach your rocket body shock cord to the nose cone and to the FRONT of your engine pod. For strength you can loop it around the ejection pod just BEHIND the front ring and feed it through the ring between the ring and the motpop ejection pod tube so it comes out in FRONT of the forward centering ring. This shock cord is going to be blasted by the ejection charge, so needs to be tough enough to handle that but pliable enough to coil up nicely between the front of your pod and the nose cone.
You will feed the cord in before you load the pod, then stuff the pod up the tail of the rocket. You will have a separate shock cord connecting the chute to the ejection pod, this can be attached anywhere between the forward and rear centering rings. Concur with der Meister that a few sheets of wadding either in the body just after you tuck in the shock cord before you stuff the pod in, OR you can put it in the pop pod before you start. This may save your shock cord a bit.
Your chute and pod shock cord will go around the pop pod tube between the centering rings. Resist the temptation to use the pod as a spindle and just wind them around. Fold your chute so it is just a bit shorter than the space between front and back centering rings, fold your cord lengthwise just a bit shorter. Sandwich the cord between the chute and the motor mount, and wrap the chute short width around the mount. It is kind of a PITB to get in but has a much higher probability of deploying than if you just wind everything around the tube.
2. One other option is to attach your rocket body shock cord OUTSIDE the rocket body, with the other end attached to the front of the motor mount BEHIND the forward ring, the outer attachment point is at or just forward of the CG of the rocket body alone (without the pod). You can use a short piece of elastic at the motor mount attachment with Kevlar on the side running along the outside of the rocket body. Can also use a small inconspicuous Kevlar attachment point on the body and a small snap swivel on the shock cord so you can dis-attach it for display purposes.
Advantage of this is that in this case your rocket body will fall and therefore impact the ground either tail first or sideways. If you use standard rear ejection your shock cord will come out the tail of the rocket and your rocket body will pretty much always impact pointy side first.
3 final suggestions.
Make sure your nose cone is screwed in or strongly glued to the body so it doesn't blow out.
Make SURE the pod slides out very easily. This is especially true because you are going to be using a lot more chute to recover your pod and rocket together than just the pod alone, which is the case for rear eject boost gliders.
You said you are using foam centering rings. The forward ring will get some blow back of hot gas, add some paper or Mylar or something in front of it to keep it from melting
Last edited by BABAR; 23rd February 2012 at 03:37 PM.
It is amazing what you can do when you don't have a choice.
Smart people learn from their mistakes.
REALLY SMART PEOPLE learn from OTHERS' mistakes.