Best Kevlar for LPR shock cord attachment?

Discussion in 'Techniques' started by neil_w, Nov 18, 2016.

Help Support The Rocketry Forum by donating:

  1. Nov 18, 2016 #1

    neil_w

    neil_w

    neil_w

    Hunkered down TRF Supporter

    Joined:
    Jul 14, 2015
    Messages:
    7,636
    Likes Received:
    1,502
    Location:
    Northern NJ
    I'm almost out of my kevlar, need to buy some more. The first time around I bought 130 lb thread, seems to be working fine. I just looked at Emmakites (didn't know about them the first time around) and all their stuff is braided... I don't know if that's better or not. I've also been wondering if I should get something slightly heaver (like maybe, 200 lb)for the 24mm stuff I've been doing... but then I don't know if that'll be overly bulky for the smaller rockets.

    I'm typically attaching the kevlar to the motor mount, and then connecting a sewing elastic shock cord to the kevlar just below the end of the BT.

    What weight and style do other folks use?
     
  2. Nov 18, 2016 #2

    Cabernut

    Cabernut

    Cabernut

    Well-Known Member

    Joined:
    Oct 15, 2015
    Messages:
    1,384
    Likes Received:
    1
    I've used 220# kevlar on my BT-5 Optima, and a couple BT-20 rockets. Works great so far after several launches. Packs in the BT-5 nicely.
     
  3. Nov 18, 2016 #3

    MCriscione

    MCriscione

    MCriscione

    Well-Known Member

    Joined:
    Jul 9, 2015
    Messages:
    295
    Likes Received:
    0
    Unless your 24mm stuff is up around the 2lb mark, you can probably keep using 120-130ish. Braided is better. I've been eyeing the emmakites stuff myself, for the next time I run short. I have a hundred feet or so left to use up first though.
     
  4. Nov 18, 2016 #4

    kyle

    kyle

    kyle

    Well-Known Member

    Joined:
    Nov 9, 2013
    Messages:
    280
    Likes Received:
    33
    I use the 100# and 300# Kevlar from Apogee for most stuff, both weights are nice and soft/flexible.
     
  5. Nov 18, 2016 #5

    mpitfield

    mpitfield

    mpitfield

    Moderator Staff Member TRF Lifetime Supporter Global Mod

    Joined:
    Jul 7, 2013
    Messages:
    4,762
    Likes Received:
    381
    Gender:
    Male
    Location:
    Toronto, Ontario
  6. Nov 18, 2016 #6

    Forever_Metal

    Forever_Metal

    Forever_Metal

    JustAnotherBAR

    Joined:
    May 21, 2016
    Messages:
    464
    Likes Received:
    24
    Gender:
    Male
    Location:
    Madison, AL
    been using it for most of our lpr stuff, works great!

    fm
     
  7. Nov 18, 2016 #7

    Micromeister

    Micromeister

    Micromeister

    Micro Craftman/ClusterNut TRF Lifetime Supporter TRF Supporter

    Joined:
    Jan 19, 2009
    Messages:
    15,074
    Likes Received:
    29
    Gender:
    Male
    Location:
    Washington DC
    For most of my LPR models up to about 2.5lbs I'm using 90 or 100lb braided kevlar from thekevlarstore.com They sell spools of natural yellow and UV resistant Green in several line strengths up to 1000lb. Great stuff at reasonable prices.

    Kevlar Line-d2_Yellow 70lb Braided (Tubular) Kevlar_11-16-15.JPG

    Kevlar Line-e_Green 100lb UV Resistant line_11-16-15.JPG

    Kevlar Line-f_Blue 200lb twisted Kevlar Line_11-16-15.jpg
     
  8. Nov 19, 2016 #8

    Onebadhawk

    Onebadhawk

    Onebadhawk

    Sponsor TRF Sponsor

    Joined:
    Jan 11, 2013
    Messages:
    5,741
    Likes Received:
    255
    Thank you very much Michael..
    I think this person wants much smaller then the 3/16" Tubular Kevlar..
    I have "Very light" kevlar and I have 1/8" Tubular Kevlar..
    Both are in 50 ft hanks at a great price...
    Take a look on my site..

    Teddy
     
  9. Nov 19, 2016 #9

    TopRamen

    TopRamen

    TopRamen

    SA-5

    Joined:
    Aug 9, 2013
    Messages:
    9,919
    Likes Received:
    15
    Emmakites stuff is great! Onebadhawk is the "Go To", but the thread from Emmakites is really nice and worth sampling.
    If you think you are going to have any problems at al, go with Onebadhawk, as they post here and are renown for quality of service to the customer.
    If you just want some convenient and nice supple braided Kevlar of the lightweights, the Emmakites I got in two different weights off of Amazon is great stuff, and I even used it in knife handles, as it is affordable and supple. It's great for rockets too, but I don't think there is any customer support, so to me, Kevlar is Kevlar, and the only Kevlar I will never buy again is that rigid stuff that for some reason is springy and stiff, and not supple at all. I'm not going to drop any names, as the seller of that Kevlar is a good person otherwise, but really? For rockets? Cheapo crappy Kevlar that is not supple?
    You will be pleasantly surprised with the quality of Emmakites if you try it.
     
  10. Nov 19, 2016 #10

    Woody's Workshop

    Woody's Workshop

    Woody's Workshop

    Well-Known Member

    Joined:
    Aug 3, 2011
    Messages:
    4,062
    Likes Received:
    101
    Gender:
    Male
    Location:
    Reed City, Michigan (Lower)
    I bought some Kevlar a few years back and started retro fitting old rockets, and using on new builds.
    I bought some from Sunward I think, and Rocketarium. Not sure what the #'s were, but probably 100 or less.
    I follow quite a few kevlar thead sellers on ebay. Kevlar makes great stitching threat on knife sheaths. Especially the waxed threads.
    For leather crafting I prefer the black, but for rockets the yellow, or UV resistant green.
    Go with MCriscione's advice and you can't go wrong.
     
  11. Nov 19, 2016 #11

    mikemech

    mikemech

    mikemech

    Well-Known Member

    Joined:
    Jul 29, 2012
    Messages:
    593
    Likes Received:
    0
    +1 on thekevlarstore.com. I bought a 1000 foot spool of 100# yellow 3-4 years ago. I use it on all my rockets. On my single (so far) HPR I just doubled it. Still have at least half the spool left.
     
  12. Nov 19, 2016 #12

    BEC

    BEC

    BEC

    Well-Known Member

    Joined:
    Feb 19, 2009
    Messages:
    2,881
    Likes Received:
    135
    Gender:
    Male
    Location:
    Auburn, WA
    +2 on thekevlarstore.com. When he first set up shop he gave folks here killer deals (buy one get one free or something along those lines). I probably have a lifetime supply of kevlar suitable for LPR models from my one buy from there
     
  13. Nov 19, 2016 #13

    OverTheTop

    OverTheTop

    OverTheTop

    Well-Known Member

    Joined:
    Jul 10, 2007
    Messages:
    3,233
    Likes Received:
    732
    Gender:
    Male
    Location:
    Melbourne Australia
    I have always used the braided stuff (300lb from Apogee) for anything D motor and above, even though it is overkill from a breaking force point of view. I think the skinny stuff is likely to floss the body tube easier during a sub-optimal deployment, so I go with the 1/8" or thereabouts braided. YMMV.
     
  14. Nov 19, 2016 #14

    ksaves2

    ksaves2

    ksaves2

    Lifetime Supporter TRF Lifetime Supporter

    Joined:
    Nov 25, 2009
    Messages:
    5,670
    Likes Received:
    127
    Ever so true about zippering. I flew a Fliskits Starlord last weekend for the first time since it was built over 7 years ago. http://www.fliskits.com/products/01prod_fs.htm Back then I did a flawless paint job to look like the rocket on the insert.
    I used some small diameter kevlar for a shockcord that could zipper the tube like heck if less than nominal deployment. I was going to get some RDF experience with a Beeline RDF tracker even though the flight was simmed to 1900 to 2000 feet and
    I expected it to come down in sight using three E9-8's. Simmed the daylights out of it and 8 seconds is what it said was reasonable. I then had a flash idea to use a Jolly Logic Chute release with the logic that if the apogee deployment was a bit more early or late than I expected, the restrained parachute pack with the JLCR would be less likely to zipper the tube.

    Well, my battery went bad in the tracker. I should have cycled/tested it as it was very old. Left it in the rocket as it was simmed with its mass. Launched it and it looked like it really got up there on the three lit motors. Apogee deployment
    looked good and with the 8 second delay it seemed to have a very nice, slow ascent. Could barely see the rocket in the early stage of the descent but I did a very shiny clear coat over the color coat and could follow the flashes till it got lower.
    I had the chute release set for 800' so I could get some hang time for using the (defunct) RDF tracker and the release did its thing right on schedule. Took a fairly long walk out to get it and when I picked up the rocket, there wasn't a single ding
    in the cardboard from the kevlar cord. I did use a relatively long cord but it had tangled and didn't extend its full length. Nonetheless, the rocket had a nice first flight.

    Bottom line is, if one has the room in a cardboard rocket with motor ejection for a Jolly Logic Chute Release, it will likely allow more protection against zippering with a too early or late ejection. RS after several runs had suggested a 14ft/sec rate after
    apogee when the chute deployed. It was so far up, I couldn't tell if that was the case. It just seemed to hang in the sky for a moment.

    Kurt
     
  15. Nov 19, 2016 #15

    pythonrock

    pythonrock

    pythonrock

    Well-Known Member

    Joined:
    Apr 3, 2013
    Messages:
    229
    Likes Received:
    6
    I've used many sizes from Emmakites, it's all good stuff. It's a tighter braid than most of the tubular kevlar from our vendors, so it's a little narrower for a given strength but harder to make "DeHate loops" and a little less stretch.
     

Share This Page

Group Builder