Should the parachute be attached to the nose cone or along the shock cord?

Discussion in 'Beginners & Educational Programs' started by Underdog, Sep 15, 2019.

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  1. Sep 15, 2019 #1

    Underdog

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    Sometime I see parachutes attached directly to the nose cone (often with a barrel swivel). However, on many rockets parachute gets attached somewhere along the shock cord. On single stage rockets is one way better than another? I'd like to avoid tangle parachute lines.
    Is this a "to each his own" decision? other locaiton.JPG nos attach.JPG
     
  2. Sep 15, 2019 #2

    neil_w

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    Kits typically specify attaching the chute to the nose cone, probably because it's simplest. I've been attaching my chutes about 6" down from the cone, on the shock cord, because... uh.... well I think @hcmbanjo lately has been recommending 1/3 of the way down from the nose, but I don't go that far with it. I do believe it is an anti-tangle strategy, but I really don't know the theory.

    It is *always* a good idea to use a swivel to attach the parachute.
     
  3. Sep 15, 2019 #3

    kuririn

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    If the chute is attached to the nose cone eye, it is easier for the nose cone to weave in and out of the shroud lines during ejection.That happened on my Custom Equinox, and the shroud lines were badly tangled.
    Putting the chute further down the shock cord lessens the chance of that happening.
    Good explanation and hcmbanjo's response here:
    https://www.forums.rocketshoppe.com/showthread.php?t=18069&highlight=interceptor
     
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  4. Sep 15, 2019 #4

    Matt_The_RocketMan

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    That depends on the rocket you are flying for Small powered rocketry to Mid Power Rocketry I would recommend fixing the shroud lines to the nose cone, this is very easy anchorage, and most of the time the shroud lines do not tangle unless you do not check them before packing. High Powered rocketry is a different story , giving they dont necessarily need to be tied down with the nose cone, usually if would have its own anchored hook to the lower recovery part of the rocket.

    On some rockets for LPR or MPR you have nose cones in which the parachute could only attached to the shock cord, also to add I would suggest that if you are wondering if the shroud line and the shock cord get stuck. Well it happens, but this only happens if there is a bad wind gust, your shock cord is to long, or the rocket deploys the parachute as it is falling towards the ground. Giving whiplash moment when the ejection charge goes of after 6 or 7 seconds... So yeah, trust me Ive seen it all with parachute failures.
     
  5. Sep 15, 2019 #5

    kuririn

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  6. Sep 15, 2019 #6

    BABAR

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    Beware of attaching anything to a plastic flange on a nose cone, they break easily.

    I usually drill a hole through the flat side and loop the shock cord through that hole and out the central hole.
     
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  7. Sep 15, 2019 #7

    jadebox

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    After a tip posted in TRF, I have stated attaching the parachute (via a swivel) to the end of the shock cord and the nosecone to the shock cord a few inches lower. It makes everything hang down in a line below the 'chute which may cause less twisting and less chance of the nosecone hitting the body.
     
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  8. Sep 15, 2019 #8

    Underdog

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    Is there a image that might explain this graphically? I'm have a hard time following this. Yes, the plastic flange on the nose cone does seem flimsy.
     
  9. Sep 15, 2019 #9

    Underdog

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    I'll give this a try. Seems simple enough. Unrelated: Do I need wadding if using a baffle on a lower power rocket (D,E,F)?
     
  10. Sep 15, 2019 #10

    Scott_650

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    This technique has worked very well for me. I’ve had the molded plastic loop fail but not the additional hole. What I do now is mount the shock cord as BABAR stated above then attach the chute to the plastic loop. My logic is, even though there’s a risk of tangled shroud lines, if the cone pops then the chute will be out. A deployed but tangled chute is better than no chute at all.
     
  11. Sep 15, 2019 #11

    Underdog

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    Which is the "flat side" of the nose cone? (1,2,3,4,?) flat side.JPG
     
  12. Sep 15, 2019 #12

    rocketguy101

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    I think he means drill a hole in the flat that is on some NCs (1) and snake the shock cord out the hole (2) like this...or as your pic shows, drill at "4" and come out the center hole...
     

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  13. Sep 15, 2019 #13

    Underdog

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    great
     
  14. Sep 15, 2019 #14

    rocketguy101

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    I've been considering starting to connect the chute to the shock cord and let the nose dangle so that the nose loop or screw eye will experience lower forces during ejection and subsequent descent...mounted as shown, when the chute opens, it supports the total weight of the rocket whereas the nose loop only has to support the shock and load of the nose.

    Edit: I prefer to use a butterfly knot to make the chute connection loop: it is non-slipping and produces less stress in the cord https://www.netknots.com/rope_knots/butterfly-knot
     

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  15. Sep 15, 2019 #15

    Scott_650

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    That shows the ideal way to do it. On my heavier rockets that’s the way I rig my shock cord and chute though I have a bag of barrel swivels I picked up at the hardware store that need installed. That’s a great graphic along with the nose cone picture to illustrate what we’ve been discussing.
     
  16. Sep 15, 2019 #16

    Nytrunner

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    You could likely get away with ito. As long as the baffle blocks the hot particles, you should be fine.
     
  17. Sep 15, 2019 #17

    BABAR

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  18. Sep 15, 2019 #18

    Scott_650

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    Drill at point #4 then route through the center and #4 - much stronger than the loop.
     
  19. Sep 15, 2019 #19

    neil_w

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    I'm trying to think of any disadvantage to this scheme and I can't think of any. It would seem to maintain a more orderly arrangement during descent.

    What are the pluses and minuses of connecting the nose part way down the shock cord, vs. connecting the parachute part way down?
     
  20. Sep 15, 2019 #20

    kuririn

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    After giving it some thought, I actually like Roger's suggestion. The nose cone is distanced from the chute, minimizing shroud tangling, and the full length of the shock cord is used to mitigate the rebound from the chute opening. I might try it on my future builds.
     
  21. Sep 16, 2019 #21

    Underdog

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    I have not figured out who "Roger" is. But I tied the parachute onto the shock cord about a third the way down from the nosecone (to the rocket).
    I flew on a d12-5 and with the exception the ejection time being too long, everything was perfect. The Super Big Bertha landed intact 10 feet from the launch pad. Open rocket had told me to use a 3 second delay (instead of 5) and I just grabbed the wrong motor.
    I'm surprised that the shock cord did not zipper the thin walled body tube with a speed at deployment of 34 mph. Beginner's luck?

    velocity at deployment.JPG
    speed off the rod.JPG
     
    Last edited: Sep 16, 2019
  22. Sep 16, 2019 #22

    neil_w

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    Roger Smith AKA @jadebox AKA "the jonrocket guy". :)
     
  23. Sep 16, 2019 #23

    Underdog

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    oh, I get all my rocket stuff at JonRocket. I'll have to try Roger's suggested alternative parachute/nose cone setup.
    note: I'll post a video of of my very first rocket launch ever and the descent (with the parachute attached 1/3 the way down). I can see how the nose cone could hit the rocket.
    I'm surprised that the shock cord did not zipper the thin body tube with a speed at deployment of 34 mph.
    velocity at deployment.JPG
    speed off the rod.JPG
     
    Last edited: Sep 16, 2019
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  24. Sep 16, 2019 #24

    BABAR

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    For elastic depends on which needs more stress relief.

    If you have a lot of extra weight on your nose cone (I have seen some filled up with BBs) you may want that to have the greatest length of elastic. On the other hand, for those of us flying without electronics, where deployment may be early or late, hence at high velocity, the chute may be the biggest stressor.

    I sort of learned this when I put a chute on my booster stage that deployed immediately upon black powder gap staging (came out of a pod off sustainer.) Rocket was going full velocity at separation. Ripped 6 of 8 shroud lines off the booster chute.
     
  25. Sep 16, 2019 #25

    Underdog

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    Here's a slow motion video of a parachute deployment. It appears that the parachute acts to slow the nose cone down and lessen the force of the shock cord on the rocket body. Hard to tell from this angle.
     
    Last edited: Sep 16, 2019
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