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Tech Tip: Question Tom's diatribe about ropes, March 2017 edition

Discussion in 'Tech Tips and Gear' started by ratagonia, Mar 7, 2017.

  1. LonePeak

    LonePeak

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    That rope test is remarkable and fairly reassuring, even considering statistical and experimental variation and that a listed min break strength gives ~15% margin from average.

    I also find the silt accumulation argument convincing about tight weaves, though I'm really not sold on nubs.
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  2. Kuenn

    Kuenn

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    As diatribes go, this one is far more informative than it is bitter. Thank you for the valuable information and advice, Mr. Jones.

    Questions:
    1. Is there any logic whatsoever why 5000 became the magical number? (Wouldn't 4K or even 3K have been sufficient?)
    2. In your opinion, what breaking strength is the absolute bare minimum? (Pragmatically speaking)
    (In Bold) May be the best line of rope construction logic (regardless of genre) I've ever read in print!
    From my experience, core shot = time to cut rope!! And 95% of the time, the core was pristine.
    Excellent advice to all... especially to the neophyte!
    X2
    Having purchase somewhere north of 1K feet of Imlay ropes over the past 5 years or so, I for one have been extremely pleased with the ROI, as well as the performance. You done good, pilgrim!
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  3. Rapterman

    Rapterman

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    X2
    When it comes to canyoneering rope, all ropes are NOT created equal!
    Manufacturing experience matters.
    That is why I am a big fan of Imlay Canyon Gear (Tom's) ropes, and of Bluewater.
    (and a good reason NOT to rappel on 'boat rope')
    :)
    Last edited: Mar 14, 2017
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  4. ratagonia

    ratagonia

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    Thanks Kuenn.

    I believe the 5000 lbs comes from the NFPA standards, the long-dominant standard in the USA. National Fire Protection Association - essentially a National body of Fire Fighters, which includes many SAR teams. They set a standard for ropes they use. SAR teams buy a LOT of ropes. The standard makes sense for them. And as the only standard around (pre CE standards), the ones to follow so when you sit on the witness stand, you can say "we used the certified rope".

    I'm happy with the 4000 lb strength. There seems to be no compelling reason to go lower.

    Tom
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  5. hank moon

    hank moon lovely ligatures

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    Pretty sure the 5000 lbf breaking strength came from OSHA 1926.502(d)(9) :
    Or OSHA may have adopted it from the original ANSI Z359.1 standard - not sure which came first. Note that the NFPA MBS requirements for life safety rope were 4500 lbf (single person) and 9000 lbf (two person) for several years, then changed to 20 and 40 kN (still the current values).
    Last edited: Mar 16, 2017
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