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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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  6. LonePeak

    LonePeak

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    @Rapterman
    Have you been able to dig up any more CRITR rope test data? It would sure be useful, thanks.
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  7. Rapterman

    Rapterman

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    The trouble with the data that we have is that it is for the UIAA test of the CRITR and not for rope by itself.
    In order to be more objective it would be better to design a test (or tests) that are specific to the (canyoneering) rope.
    Please feel free to design one!
    :)
  8. ratagonia

    ratagonia

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    What particular data do you think would be useful?

    Tom
  9. LonePeak

    LonePeak

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    I suppose that a figure 8 loop tension to failure test would be the place to start for the broadest comparison to other data. More canyon relevant would be the EDK, or better yet the offset overhand follow-through. See pg 32 of this link. http://www.paci.com.au/downloads_public/knots/01_Knots.pdf It would be helpful to add a triple clove hitch block on a round biner through a 5/16" rapide, with a double-fisherman backup in the tail. It may surprise some people to see the effects of varied rapide diameter on the same rope in throw & go setup, and possibly blocked configuration. If we can be ambitious, I'd suggest setting up a 90' rock edge and pulling the rope over it and down to a locked off CRITR, with load cycles increasing until failure. The longer the rope is above the edge, the more enlightening sawing action would take place. If I really had my druthers, I'd add doubled pull cords and certain high strength 6mm emergency cords, besides the list of canyon ropes on the market. Relevant to pull cords would be the double fisherman's bend. And the statistical significance lacking in so many informal studies- probably a sample size of 6 if possible. What do you think?
  10. ratagonia

    ratagonia

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    I think for $ 20,000 I could get good data for you as suggested.

    But I'm not sure any of this data would have ANY impact on what you are doing. Given that most gear is built to a 4000 to 5000 lbf standard, and loads in canyoneering top out at about 600 lbs... There is almost a 7:1 safety factor over KNOWN highest force.

    It is kind of like the UIAA descender test making sure rappel devices can go to 15 kN - 3300 lbf. If you are applying 15kN to your rappel device, something has already gone very, very wrong.

    Relevance. I question the relevance.

    Tom
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  11. LonePeak

    LonePeak

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    Oh, and lets not forget flex fatigue. Also durability: load cycles at 250 lbs over the same rock.

    @ Ratagonia If every rope is so over-engineered that safety is not a concern, then either we should be reducing weight and diameter, or possibly buying the cheapest, which you might appreciate. But I'd lean more conservative on those safety factors than you're suggesting here, especially by considering test/use configuration, and reduce weight at the same time. Despite their high strength to weight ratio, you've spoken out against other fibers besides polyester, like dyneema, vectran, aramids, citing Moyer's old paper, "Comparative testing of high strength cords," and if that opinion is true, then materials and construction do matter. Polyester blends with higher strength materials are interesting for weight and price, if the bounce is reduced.

    If perhaps you're only concerned about sheath durability (and I remain concerned about more than that) then durability studies comparing canyon rope examples of different weaves and thicknesses and aramid vs polyester would be the thing. We'd find out which products perform better than others, and I'd like data on that if we can get it, not just opinion on one site where one seller is by far the most prominent voice (though that voices certainly continues to offer so much to the community thath he helped to build). At least invited opinions from other rope makers would be helpful, but data is better. The question is, what tests would be most relevant?
  12. Rapterman

    Rapterman

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    Wow, LonePeak
    That is a VERY ambitious series of tests, which could take a lot of hours, and would destroy a LOT of rope.
    If Tom would do it for $20,000 that's a bargain.
    Maybe something less ambitious that can happen in the lab (on a test machine)?
    .....
    Last edited: Apr 7, 2017
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  13. Rapterman

    Rapterman

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    Some more thoughts, LonePeak-
    PERFORMANCE is just one part of the rope formula:
    the other is price.
    I believe one of the nicest ropes is the 8mm Bluewater canyon Extreme (technora sheath, dyneema core)
    But it is expensive. (I have not yet tried the new Canyon Lux by Sterling)
    On the other hand, Tom's 8.3mm Canyon Fire is a GREAT rope at a MUCH more affordable price.
    Perhaps neither is the best beginner rope where a larger diameter might be better and more durable.
    We all would like the TESLA
    but may only have coin for the BOLT
    :D
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  14. LonePeak

    LonePeak

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    True enough, money talks, esp value over time. That's why I'm interested in finding out whether the light-weight aramid-sheathed dyneema/vectran/pProp cores are worth it in the long run, or if they wear just as fast. Personally I'd also like to avoid those Imlay nubs with at least a 2/2 weave in the future, but I'm now sold on the tight weave for keeping out sand.

    Yep, all those tests were idealistic suggestions. If someone had a mechanical tester and a few samples but not a lot of time, I'd guess that a fig 8 loop test would give us a useful idea of how much the knot efficiency of high strength fibers have improved since Moyer's paper. If more time were available, the quicker version of the more canyon-relevant sheath test would be pulling over some fairly rough edge with increased load cycles to failure, with enough lead rope for scrapage. Depending on the mech tester configuration, a rough edge might be pushed into the lower end of the test section of the rope, and hopefully there's room for enough elongation for scraping to occur. Just my thoughts.
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  15. Rapterman

    Rapterman

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    I would be careful not to equate Moyer's paper to the specific canyoneering ropes we have been discussing.
    There are many nuances that go into rope construction besides the raw materials used (as Tom has helped demonstrate)
    Because some rope designed for a different application in a different diameter does poorly on a test does not mean that all ropes
    with similar fiber will share the same characteristics.
    Climbing rope performance has evolved significantly over the past 30 years but the raw material (nylon 6-6) is essentially the same.
    :)
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