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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. ratagonia

    ratagonia

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    Yes, this is a "sales pitch" and perhaps should be only posted in my own cyberspace. But, that does not allow for discussion and counter-argument, something the Canyon Collective is meant for. Thus I post it here with this note, that some will find this inappropriate for this forum. This originally was a response to a potential-customer question. The customer is unknown to me, so I do not have any background on them... except that the question identifies them as likely new to canyoneering.

    Comments and discussion on these points, PLEASE! I mean, on the points made in the diatribe.

    ---
    Hello,

    I am interested in your canyoneering rope, but can't decide between the lighter C-IV polypropylene core, versus the 9.2 Imlay Canyonero polyester core; strength appears about the same since the C-IV is only 9mm.

    Is the strength of the sheath on the C-IV much superior to the Canyonero polyester sheath?

    (An interested Customer)

    Tom answers with a lengthy diatribe:

    Do you break ropes often?

    There are not many numbers that can be attached to specific ropes. Obviously, the weight, the cost and the diameter, although the latter is somewhat suspect as there is no standard way of determining diameter and stated diameter varies widely between brands and models. But there is strength, and EVERYBODY likes strength. Achieving that 5000 lbs strength is kind of a magic number. Which for canyoneers is fairly meaningless. I weigh 200 lbs on a bad day - my 4000 lb rope therefore has a 20:1 safety factor, which even the most conservative folks recognize as plenty safe. Ropes don't break in service, unless something else very very very wrong has already occurred.

    You should note that the Imlay brand of ropes is MY brand, so they are designed and manufactured based on my line of thinking. Since they are (likely) the most popular ropes in American canyoneering, I believe my thinking is consistent with the real world (but then again, all humans think their thinking is consistent with the real world).

    The C-IV is a good rope and I have used it on trips. I like it. One thing to note is that the C-IV rappels like an 8mm rope, because of the overall softness. So you would want to use it with a modern, small-rope rappel device like the ATS, Critr or Sqwurel; and get comfortable with its properties in an extra-safe environment before using it out in the real world. Then again, that advice should be applied to all changes to key equipment: ropes, rappel devices, that extra 15 lbs put on over the winter... first trip rappelling with an overnight pack, etc.

    The more apt comparison would be between the C-IV and the Canyon Fire rope. They rappel about the same. The weight of the Fire is 3 lb 13.6 oz per 100 feet, vs. the C-IV which is 3 lb 5 oz per 100 feet. (I get 3 lb 4 oz on my scale). The Fire is $160.00 for a 200'er, and the C-IV is $ 239.00. The Fire is available in a variety of lengths while the C-IV is hard to find in anything other than 200 feet.

    The C-IV uses Technora as 100% of its sheath. Technora is an aramid-class fiber that is considerably more expensive, denser, has a higher tensile strength and is more cut resistant than polyester. It may or may not be more abrasion resistant - test data on this is mixed. Our friends in Hawaii are clear that the C-IV holds up much better to the cutter volcanic rock than the Canyonero rope.

    The Canyon Fire uses a one-over-one 8 by 8 sheath, meaning the sheath is made of 16 bundles of fibers woven together. I designed this with as much fiber as possible in the sheath, which ends up being 56%. While the core determines the strength rating, the sheath is what we care about mostly when canyoneering. Once the sheath is compromised, we consider the object to no longer be a canyoneering rope.

    By contrast, the C-IV uses a 2 over 2, 8 by 8 sheath, thus using 32 bundles of fibers to build the sheath. I have not cut up and measured a C-IV rope, but the implication here is that the C-IV sheath is somewhat thinner than the Canyon Fire sheath, which could be as much as half as thick, but then we have to factor in the larger finished diameter of the sheath, therefore it is likely to be 3/4 of the material of the Canyon Fire sheath. Thus, my claim, lightly supported by the offered evidence, is that even assuming somewhat better performance of the Technora fibers, the overall toughness of the ropes should be pretty much the same in normal canyoneering circumstances. As noted in Hawaii, one real cutter rock, the C-IV holds up better.

    What does field data show? Some people like the one, some people like the other. Some people get great durability out of X. Some people screw up their rope in their very first canyon (and claim it has to do with the rope). My claim in general is that screwing up ropes comes from a mix of bad technique, lack of care in rigging (together = unforced errors) plus the occasional unfortunate circumstance where screwing up the rope is hard to avoid (ie, whenever *I* screw up a rope it must be this!) There are bad ropes out there, but there are quite a few good ropes, and the differences between the good ropes (in terms of resistance to screwing up) are small.

    Personally, I think people are better served by buying my ropes, which are good ropes and considerably less expensive than other good ropes. Most people get good durability out of my ropes, and like the way they handle... well, at least people I talk to, which is not likely to be a truly representative sample. You can buy the more expensive ropes, but I think you are unlikely to get more life out of them than out of my ropes.

    There are places where weight is a dominating factor (I'm looking at you, Grand Canyon), and in this case, I think using lighter ropes is better. My preference here is the Bluewater Canyon Pro 8mm type ropes. Personally, I use my own Canyon 8mm rope which is not quite as light as the Canyon Pro, and is half as durable as the Canyon Fire (and thus does not quite make it into the category of 'good ropes') - but obviously, my 8mm rope costs ME a LOT less than the Canyon Pro, and I tend to cut it to the exact length required, as is my privilege. You can purchase that from me for weight-dominant activities for considerably less than the Canyon Pro, but do not expect to get long life out of this model.

    Thus ends my diatribe about ropes.

    Tom :moses:
    Last edited: Apr 25, 2017
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  2. LonePeak

    LonePeak

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    My question is this: Do the high weave tension of Imlay sheaths and their low plait weave significantly reduce their resistance to abrasion? I've seen significant abrasion on the canyonfire from tough pulls. Tension obviously makes a rope easier to cut, and that should be true for tense sheath fibers, but how heavily that contributes I don't know. Also they are very nubby due to the 1/1 8 fiber weave, which means that rather than distributing their entire surface area over the rock face, just a few top fibers take the brunt of friction and get torn up. Moreover, the rope and especially sheath are stiff, that is locally inflexible, so they can't avoid some of the abrasion by flattening out to conform to the rock. To understand this, think of hard plastic knee pads getting more scratched up on rock than soft webbing. Anecdotally, it seems to me that this wears rappel devices faster than higher plait ropes. So isn't the thick sheath offset by these disadvantages? I'm very interested in feedback about this, at the technical detail level if possible as well as practical experience comparisons with other ropes. I'll be out of town for a few days.

    P.S. I find it's helpful to slip some tubular webbing over the end of the rope to protect the biner block and nearby high wear sections from abrasion, then make sure the knot is properly backed up.
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  3. ratagonia

    ratagonia

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    I understand your question, and am interested in people's answers to it, but...

    While the sheath is woven under tight tension, after it is woven, the strands are under only the tension of the rappeller, same as the sheath strands of any other rope.

    Do you tie the biner block in the section of rope sheathed with tubular webbing?

    Tom
  4. LonePeak

    LonePeak

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    Except that there appears to be much more circumferential tension in sheath strands in stiff Imlay rope, whether at rest or loaded, than in other ropes, which have much more flexible and less nubby sheaths.

    Yes, I tie the biner block in the webbing protected section. To prevent slippage, I recommend a triple clove hitch plus backup with an offset overhand followthrough bend (EDK 1.5) or double fisherman'r or similar, which happens to be the bend attaching to the pull cord.
  5. ratagonia

    ratagonia

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    Could be. But... the sheath fibers run at 45 degrees to the length of the rope. They necessarily cannot have different tension in the two directions.

    The sheath on the Fire is not particularly tight on the core. I know what you mean, but I think it is more illusion than reality. If you measured the tension in a Canyon Fire sheath fiber at rest, I think you would find the tension is zero.

    Well, that's what I thought. So I decided to cut a piece and see what happens. Here is a photo of the purple sheath strand cut across. This is a particularly stiff end piece of CF. After cutting, the edges of the wound are a little bit apart, which suggest that maybe there is resting tension in the sheath.

    I'm not sure it is enough to impact the abrasion resistance. I think the tension of the canyoneer on rappel would dominate, but hard to say without making actual measurements. Also, the rappellers tension is mostly held by the (much, much) stiffer core, rather than by the sheath.

    My personal experience is that stiffer (tighter-woven) ropes tend to be MORE resistant to cutting/abrasion.

    Tom

    CanyonFire Cut Sheath Fiber. Sterling C4.
    Last edited: Mar 9, 2017
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  6. ratagonia

    ratagonia

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    UPDATE:

    1. Taking some pictures, I am reminded that the C-IV has an almost-100% Technora sheath, not the 50-50 I was thinking. Sorry about that.

    2. Our friends in Hawaii, who canyoneer on very sharp volcanic rock, have tried the Canyonero, finding that it cut up pretty quickly. Their choice is the C-IV (plus edge guards when feasible) which lasts a lot longer. So on sharp rock, the Technora definitely lasts longer.

    3. I misstated the number of sheath strands on the C-IV - it is actually 8*4 = 32.

    All these points have been corrected and/or added to the diatribe above.

    Tom
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  7. AW~

    AW~

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  8. ratagonia

    ratagonia

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    Here is a closeup of some well-used Canyon Fire showing how it wears. Cut fibers all over, but no cut sheath bundles - so, seems like abrasion breaks fibers on the outside (as expected) and it seems that as the rope gets worn it will be less tough, and eventually one or more sheath bundles will be cut all the way through.

    This particular rope we would use without concern, at least for short rappels.

    Tom

    CanyonFire Well Used.
    Last edited: Mar 12, 2017
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  9. ScottM

    ScottM Looking for a canyon, you got one?

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    Tom,

    Can you elaborate on the terms you used above. (I.E. "one-over-one" and "8 by 8")

    Thanks,
    Scott
  10. Brian in SLC

    Brian in SLC Brian in SLC

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    Rope braiders are amazing pieces of machinery...

  11. ratagonia

    ratagonia

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    I was hoping the pictures showed that sufficiently.

    Let's call the bundles of fibers that the sheath is braided from "threads".

    A one over one is a simple braid. One big thread goes over, under, over under.

    A two over two does the same thing, but each thread is two threads next to each other. Two threads go over two threads, then under two threads, then over two threads.

    8 by 8 is the number of threads that make up the sheath. 8 threads going left to right, 8 threads going right to left. Also called 16 bobbins. Easier to see on a rope with only one tracer (like the Sterling C-IV below). On this rope, there is only one pair of black threads, so you can see there are in that direction 8 threads, one black, one green and six technora; and in the other direction eight technora.

    I consider this 8 by 8, two over two. But I assume it takes 16 bobbins each way so it could be called 16 x 16. I'm not sure how the actual rope making nerds designate it.

    Hope this helps.

    Annotated Rope.
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  12. ScottM

    ScottM Looking for a canyon, you got one?

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    Yes, that certainly did help. Thank you.

    Hindsight is now 20/20 [for me].

    I could certainly see this...

    This wasn't as easily discernible. I was not accounting for the "threads" to be side by side.

    Thanks again!
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  13. LonePeak

    LonePeak

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    Thanks for the further testing and info, @ratagonia. I'd like to see somewhere a comparison with more supple, higher plait weave ropes than either C-IV or Imlay. It makes no sense to me that a stiffer rope could possibly be more abrasion resistant than a supple one, all else being equal, because the supple one conforms to the rock better and distributes the same force over a larger surface area. Similarly, a higher plait weave sheath will be less nubby and also distribute the force over more fibers. If one gets a different impression, I have to think that there must be other confounding factors at work. Also a slightly looser weave would most likely allow fibers to shift more to relieve local tension created by bending over a rock edge, reducing wear. It's conceivable that some of this might be offset by some other factor, like how thick you're able to make the sheath with a given number of fibers or something.

    I observe that in my odd assortment of cords, I see the the following comparison from most abrasion resistance to least: high plait aramid > high plait polyester or nylon > low plait aramid > low plait polyester or nylon. FYI by high plait weave, I'm talking about a larger number of smaller fiber groups woven in the sheath for a smoother, more supple finish. I further observe that a fuzzy, sandy rope wears out rappel devices much more quickly than a slick, clean one.

    All in all, I'd like to see scientifically controlled abrasion testing of all canyon rope brands pulled over the same sharp rock edge, or the closest thing we could get to it. I wish rope makers would provide more comprehensive engineering data. Anyone know how to get it? I've been communicating unsuccessfully with Teufelberger (New England Ropes) for months.

    Had another tough pull this week that really scratched up the [biner] and the webbing that protected my Imlay rope. If I hadn't protected it, that could easily have been a core shot. Protecting with webbing does make the pull a little harder at the rapide, so straighten it out carefully. Where practical, extending anchor webbing all the way to the final edge helps too.

    If the information is available anywhere, I'd like to see how much dyneema/spectra fibers, like part of the cores of CanyonLux, may have improved since Tom Moyer's 2003 testing to tolerate knots better. Rope strength at the knot was reduced by a whopping 60-70% in those days, and that may still be true! My conservative safety factor calculations make me uncomfortable on spectra core ropes without specialized gear like rope thimbles at the anchor.

    I noticed significant bounce on Sterling C-IV this past weekend, which is to be expected with a polypropylene core. But the aramid sheath seems more durable than polyester from what I've seen too.

    One other factor to be considered is that when stuffing it in a bag (which helps so much to prevent tangles) supple ropes are far less bulky than stiff ones, by an estimated 25-50% for similar diameters.
  14. ratagonia

    ratagonia

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    I think you missed one of the key points.

    The rope is kaput when ONE of the sheath threads is all the way cut through. A higher-plait weave is necessarily thinner. My worn Canyon Fire shows a lot of cut fibers, but zero cut threads. Looks to me like the threads are halfway cut through. The rope is now smoother.

    I understand your reasoning, I just don't believe that what you think are the key parameters are the key parameters.

    ---

    On your other items, let me know when you get the test lab set up and a good tech hired, and I can provide some rope samples. In six months, you should be able to get some fairly good data. ;-)

    ---

    Tom Moyer's tests were done with Spectra Slings. Having the core inside the sheath is like having a thimble on it. The radius the core is subject to in even a tight knot, using a rope, is much, much larger than the tiny radius a spectra sling sees when girth hitched. Therefore the loss of strength should be much, much less.

    ---

    My main thought on this is that the cavers have shown that stiff, tightly woven rope is effective at avoiding cutting. I have heard it called Indestructible Rope Technique, and some of the PMI products are way stiffer than my stiff ropes. Perhaps Onkaluna or Kuenn could comment on their experience.

    The other nice thing about the stiff rope is that it has a lesser tendency to get stuck on pulls.

    Tom
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  15. LonePeak

    LonePeak

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    @ratagonia
    "Blue Water Titan has a braided Spectra/Nylon core and a Nylon sheath." - Moyer, 2003.
    https://user.xmission.com/~tmoyer/testing/High_Strength_Cord.pdf

    In this study, this sheathed spectra/nylon lost 47% of its strength at the knot. The nylon component surely improved knot efficiency. The 70% spectra loss I mentioned incorrectly as Moyer's data probably came from another spectra study. I'll update if I find the correct reference again, until then please disregard. However you can reach similar loss by combining knot efficiencey with flex fatigue in Moyer's study.

    So the danger with spectra core knot efficiency remains significant.
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  16. Bootboy

    Bootboy Atwood Gear

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    It has been my observation with softer (looser sheath) ropes that they gain bulk over time. They fill with sediment from dirty water and being in the sand and their properties change over time. I had a short section of rope that had done this over the course of a couple seasons. I was curious as to why it had gotten bulkier and firmer so I cut a piece of it and pulled it apart. The polyester core that was originally pure white was rust colored and there was a small pile of dust/sand on the table that had fallen out of the fibers as I pulled it apart.

    The amount of silt that a loose/soft rope can pickup is really impressive.

    So one added benefit to stiff, tightly woven ropes is that they are more impervious to sediment and their properties and handling characteristics seem to change less over time.


    Sent from my iPhone using Tapatalk
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  17. hank moon

    hank moon lovely ligatures

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    Strength in numbers, short version:

    Looser sheath braid = looser sheath yarns/bundles, so individual fibers are more susceptible to being separated from the protecting bundle and damaged.

    Tighter weave = more cohesive sheath bundles, so individual fibers are less exposed to damage.

    Experience shows that this generally holds true for rope rubbing up-and-down over "friendly" sandstone or limestone surfaces. With harder rock surfaces and/or rock types, combined with lateral rope movement, etc. the balance can quickly change.
    Last edited: Mar 12, 2017
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  18. Rapterman

    Rapterman

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    Good thread!
    Lone Peak- regarding the strength of dyneema core ropes when knotted.
    During development of the CRITR rappel device we performed the UIAA test with multiple brands and diameters of canyoneering and climbing ropes.
    All test ropes were knotted (figure eight) at the anchor. After UIAA was complete (loading to about 1600 lbs and holding for 1 minute) we pulled
    many of the samples to failure.
    All samples broke at the knot in the rope.
    I will try to dig up some photos and specific test results later, but recall that there was (as expected) about a 40% strength loss for ALL samples.
    In our tests dyneema core rope (8mm Bluewater canyon pro) had the same expected percentage loss but with one advantage:
    you get an initial rated strength of 5000 lbs in a 8mm package.
    In our day job we manufacture safety products that utilize both dyneema (spectra) and nylon webbing and have done lots of testing with both.
    And yes, tying knots in dyneema SLING is generally a bad idea.
    But dyneema core ropes are as strong/stronger as any out there and broke at the highest values in our tests.
    :)
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  19. LonePeak

    LonePeak

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    Thanks for the useful information! I'd love to see more test results, @Rapterman. There's so little published.

    Here's an article showing sheathed dyneema core rope losing 65% of its strength at a figure 8 (Flemmish) and other knots.
    http://www.yachtingmonthly.com/sailing-skills/strongest-sailing-knot-30247

    I've been talking of rope, not webbing. Results for the latter tend to be all over the board. I've seen rope tests somewhere that show turns around pipes even >1 inch in diameter that still significantly reduced breaking strength, though the effect is greatly exacerbated by smaller radii, like a small rapide or bend with a small diameter rope. With dyneema the effect is worse. Beware! Thus a rope thimble is far stronger than a knot in a thick sheathed rope and may be useful for those who chose to double over small diameter line in an emergency--a controversial topic I'm not trying to pursue further here. Even a fat rap ring is better than a rapide.

    The triple fisherman is generally the strongest knot short of a proper splice. If you want to attach a lead line of more durable rope to your dyneema/amsteel/spectra pull cord, use it. If you splice the end of the dyneema then attach a stronger cord with a girth hitch, reef (square knot), or sheet bend, you don't get any knot strength benefit out of the splice, just a little security. Might as well just tie the knot.

    Wouldn't it be great if a thickly sheathed rope could be smooth at production so that a nubby one doesn't have to be worn down before it starts to distribute friction forces over a larger surface area? You'd get more abrasion resistance per weight without carrying all those quickly cut, top-of-the-nub fibers.

    @ratagonia Do you have any reference for stiffer ropes being more resistant to abrasion than supple ones, or could you propose a plausible mechanism?

    I'd love to see a well-balanced analysis of other specific canyon ropes here, with input from their makers as well if at all possible.
  20. Rapterman

    Rapterman

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    ACTUALLY...
    Our (rather limited) CRITR test results show the the Bluewater Canyon Pro had superior results.
    In this particular test we had used the same piece of rope for multiple pull tests to 1600 lbs, then pulled to failure (of the CRITR).
    The CRITR folded over and snapped in two at 3,980 LBS then we stopped the test.
    The Bluewater 8mm dyneema core rope strand had sheath break at the knot and where the rope wrapped
    around the CRITR but 5 of the 6 dyneema core strands were still un-damaged.
    For any rope knotted with a figure eight to still be intact after being pulled to 80% of its rated strength is pretty impressive...
    BEFORE:

    CRITR test destruction 3-14-14.

    AFTER:

    bluewater canyon pro test.
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