Shock cord lengths and narrow rockets

Discussion in 'Recovery' started by Jackball74, Jun 15, 2017.

Help Support The Rocketry Forum by donating:

  1. Jun 15, 2017 #1

    Jackball74

    Jackball74

    Jackball74

    Well-Known Member

    Joined:
    Nov 24, 2009
    Messages:
    385
    Likes Received:
    0
    A friend of mine is working on his first rocket, an Alpha III, and was wondering what he should do about the shock cord. I use elastic nylon and go by the "twice as long as the rocket" rule, but all of my craft are at least 1.34" in diameter and generally longer than a foot. Would this be effective for a short rocket with a narrow diameter, or would you risk running out of room for a parachute and wadding? I imagine it would also be a nightmare to pack.
     
  2. Jun 16, 2017 #2

    dhbarr

    dhbarr

    dhbarr

    Amateur Professional TRF Supporter

    Joined:
    Jan 30, 2016
    Messages:
    5,523
    Likes Received:
    526
    An easy upgrade for most any Estes kit is to just prepend a length of Kevlar about the same length as the stock elastic.
     
  3. Jun 16, 2017 #3

    Banzai88

    Banzai88

    Banzai88

    Lvl 1,Wallet....Destroyed

    Joined:
    Jul 15, 2015
    Messages:
    1,946
    Likes Received:
    228
    Since there is no give or stretch with kevlar, you're going to want to go the recommended "3-5x the length of the rocket". Anything shorter usually ends up with zippers. Since it's much smaller, lighter, and can be packed tighter for the extra length than the rubber, it usually works rather well.
     
  4. Jun 16, 2017 #4

    T-Rex

    T-Rex

    T-Rex

    Ordinary Average Guy

    Joined:
    Jul 22, 2011
    Messages:
    2,930
    Likes Received:
    20
    I am not sure I understand where the question comes from. The kit should come with a length of shock cord. If he wishes to replace the rubber band with elastic or kevlar there should be no problem getting it into the tube, even adding a few extra inches to avoid the "Estes Smile" should easily fit. If he is worried, test fit the cord and chute before it gets glued in....

    Normally the only time I have an issue with the laundry in the tube is BT20 & BT5 sized models
    I will add that getting a 12ft of nylon and a 70" chute into 18" of 3" tube is a bit frustrating. I plan to change to kevlar soon.
     
  5. Jun 18, 2017 #5

    caveduck

    caveduck

    caveduck

    semi old rocketeer

    Joined:
    Jun 6, 2011
    Messages:
    1,191
    Likes Received:
    55
    I can vouch from supporting a number of youth launches that the stock Alpha III is very tight on laundry space. Switching the stock rubber to elastic will help a bit since the elastic packs up better. Changing to 1.5m of kevlar will free up even more space, as will changing the parachute from the thick 1mil Estes version to something thinner.
     

Share This Page