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  1. #1
    Join Date
    23rd November 2013
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    Finger Trap Technique

    I posted this on my build thread but thought I would put here as well.



  2. #2
    Join Date
    13th October 2014
    Location
    SouthEastern, WA
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    Quote Originally Posted by Lowpuller View Post
    I posted this on my build thread but thought I would put here as well.

    Very clean, I have seen this done with paracord.

    Rich

    NAR# 99154

    L3-4x upscale Estes Cherokee-D- AT M1297W 5/28/2016 http://www.rocketryforum.com/showthr...r-rharshberger

    TriCities Rocketeers NAR section# 736 http://www.tricitiesrocketeers.org/

  3. #3
    Join Date
    23rd November 2013
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    I am parachute rigger that's where I learned the technique.

  4. #4
    Join Date
    3rd August 2011
    Location
    Reed City, Michigan
    Posts
    2,674
    Would there be any bonus to a double loop in the swivel like a fly fishing knot?

  5. #5
    Join Date
    24th April 2010
    Location
    Wisconsin
    Posts
    1,575
    Very nice!!

    I want to see the next step - I would like to see how you do the two rows of stitching.
    -Scott Sager
    NAR 91621 L2
    TRA 15982 L2
    Woosh #558
    KC9WQK

  6. #6
    Join Date
    27th March 2013
    Location
    Has Changed
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    8,839
    Nice Video!

    I'll 2nd Scott's motion (or a nice photo of it).
    Dreaming of making the rockets I dreamed of as a kid (and then some).


    NAR L1 Cert flight: Sheridan, Oregon, USA. Sept. 19, 2015. Flew Deep Space OFFl on an I357T-14A Blue Thunder

  7. #7
    Join Date
    13th November 2009
    Location
    Katy, Near Houston (still Texas, though)
    Posts
    4,575
    Quote Originally Posted by K'Tesh View Post
    Nice Video!

    I'll 2nd Scott's motion (or a nice photo of it).
    Ditto!

    Greg

  8. #8
    Join Date
    23rd November 2013
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    1,900
    I use a single needle machine and this little guide.

    Click image for larger version. 

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  9. #9
    Join Date
    11th May 2009
    Location
    Phoenix, AZ
    Posts
    374
    Thanks for sharing the video!

    I do this on all my recovery harnesses. With no stitching. Stitching is not needed for strength, believe it or not. I put a lot of effort trying to get this method to fail, it just doesn't happen.
    Scott Wathey
    TRAPHX VP and Waiver Getter
    TRA 7726
    KF7EIV

  10. #10
    Join Date
    15th February 2009
    Location
    North Texas
    Posts
    382
    I've also been using the 'finger trap' technique for many years with all sizes of Kevlar. Since I don't stitch mine down (I like to be able to undo the connection) I use a much longer portion of trapped cord, about 2x-3x shown in the video. Even on large 50lb+ rockets it has never failed.

    Once you get the hang of it I find it does not take very much time and I eliminated the need for quick links. None of the three rockets I flew at BALLS used quicklinks - all were connected using loops made using the finger-trap method. The cord packs a lot neater and area for packing and weight is reduced.

    Nice video, thanks for sharing it.


    Tony
    why do people put so much stuff in their sigs?

  11. #11
    Join Date
    23rd November 2013
    Posts
    1,900
    Thank you for the comment.

    If you leave the stitching out, over time the tensioning and untensioning of the finger trap will allow it to loosen up and eventually slip out. Granted it takes many occurrences but eventually it will happen. Try it on the bench sometime, my guess is that it will fail in 10 attempts or less.

    Another factor that comes into play is the length of the tail, the longer the tail, the less likely the failure.

    Having said all that I believe the likelihood of yours failing are slim to none, but why take the chance. My only regret was not using Kevlar thread, but it was crazy expensive on eBay.

  12. #12
    Join Date
    13th October 2014
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    SouthEastern, WA
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    Quote Originally Posted by Lowpuller View Post
    Thank you for the comment.

    If you leave the stitching out, over time the tensioning and untensioning of the finger trap will allow it to loosen up and eventually slip out. Granted it takes many occurrences but eventually it will happen. Try it on the bench sometime, my guess is that it will fail in 10 attempts or less.

    Another factor that comes into play is the length of the tail, the longer the tail, the less likely the failure.

    Having said all that I believe the likelihood of yours failing are slim to none, but why take the chance. My only regret was not using Kevlar thread, but it was crazy expensive on eBay.
    Check out The Thread Exchange, they have kevlar threads at decent prices.
    Rich

    NAR# 99154

    L3-4x upscale Estes Cherokee-D- AT M1297W 5/28/2016 http://www.rocketryforum.com/showthr...r-rharshberger

    TriCities Rocketeers NAR section# 736 http://www.tricitiesrocketeers.org/

  13. #13
    Join Date
    23rd November 2013
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    1,900
    WOW! Thank you, the thread exchange is actually less than 5 minutes from where I work but I had ever heard about it.

  14. #14
    Join Date
    13th October 2014
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    SouthEastern, WA
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    Quote Originally Posted by Lowpuller View Post
    WOW! Thank you, the thread exchange is actually less than 5 minutes from where I work but I had ever heard about it.
    They have excellent service via their online sales, but I cannot speak for onsite sales.
    Rich

    NAR# 99154

    L3-4x upscale Estes Cherokee-D- AT M1297W 5/28/2016 http://www.rocketryforum.com/showthr...r-rharshberger

    TriCities Rocketeers NAR section# 736 http://www.tricitiesrocketeers.org/

  15. #15
    Join Date
    23rd November 2013
    Posts
    1,900
    I'll let you know!

  16. #16
    Join Date
    15th February 2009
    Location
    North Texas
    Posts
    382
    Quote Originally Posted by Lowpuller View Post
    Thank you for the comment.

    If you leave the stitching out, over time the tensioning and untensioning of the finger trap will allow it to loosen up and eventually slip out. Granted it takes many occurrences but eventually it will happen. Try it on the bench sometime, my guess is that it will fail in 10 attempts or less.

    Another factor that comes into play is the length of the tail, the longer the tail, the less likely the failure.

    Having said all that I believe the likelihood of yours failing are slim to none, but why take the chance. My only regret was not using Kevlar thread, but it was crazy expensive on eBay.
    I often undo and then redo my loops as I don't use quick-links. So I need the ability to be able to undo the loops. But I dress them before every flight.

    I do agree that if you don't secure the loop it can come undone over time. Either stitch it as you do or make sure to dress the loop every time you fly. BTW, after seeing your trick I've tried it with very small cord using solid core copper wire and it works great. Beats my old way of doing it hands down.


    Tony
    why do people put so much stuff in their sigs?

  17. #17
    Join Date
    1st September 2010
    Location
    Tucson, AZ
    Posts
    852
    This is definitely getting filed away for future use...thanks for sharing!
    NAR 96681
    L1 - May 29, 2014 LOC Norad ProMax, H120
    L2 - Feb 21, 2015 Fiberglassed Madcow Frenzy, J280

  18. #18
    Join Date
    26th November 2009
    Posts
    3,645
    I gotta make me one of those wire loop pullers!!!! Dang that's slick. Thanks. Kurt Savegnago

  19. #19
    Join Date
    12th April 2011
    Location
    Huntsville, AL
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    39
    Quote Originally Posted by Lowpuller View Post
    I am parachute rigger that's where I learned the technique.
    It's cool to see fellow riggers involved in rocketry.
    :cool::cool::cool::cool:
    Skydiving Enthusiast
    FAA Senior Parachute Rigger

  20. #20
    Join Date
    23rd November 2013
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    Cool, we probably met along the way, 2000+jumps, AFFI, SLI, PRO, Senior Rigger, working on Master. I learned the technique from Dave DeWolf.

  21. #21
    Join Date
    27th January 2009
    Location
    Oregon
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    One of my contractors did something similar for making loops in a wire rigging that helped support/stiffen my deck roof members....

    Frank

    Manufacturer of 24mm RC Rocket Glider Kits: dynasoarrocketry.com

    Franks Rocketry and R/C Airplane Blog

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