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Webbing Failure During Test Bouncing

Discussion in 'Accidents and Near Misses' started by willie92708, Nov 23, 2018.

  1. willie92708

    willie92708

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    Yesterday we came across an old webbing anchor with 2 separate piece rigged around a large buried rock with slip knots. The only part showing was the 2 single strand tails that came out of the dirt at the slip knots and extended to two quick links (see photo) Overall both pieces of webbing were supple (although dirty) and appeared to be tan in color. One of the webbing strands was cut near the knot with the quick links and the other was not cut. There was plenty of tail length on both strands to retie the anchor a few feet shorter, if we decided to use it.

    First, I bounce tested the strand that was connected to the quick links, because it had some fraying. On the third bounce the webbing failed (see top of photo for break point). Immediately, I'm thinking, this webbing must be very old. So we started digging it up and, yes, it was Sun bleached from red to tan so uniformly for all of it above ground or not buried tightly in a knot, that it was not obvious how bad the Sun bleaching was!

    Photos and discussion here: https://www.facebook.com/groups/canyonrigging/permalink/2102540243136502/

    [​IMG]
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  2. willie92708

    willie92708

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    Had to scale the photo size down a bit to post:

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  3. willie92708

    willie92708

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    Here's a picture with the knot at the quick links untied and laid out. The other piece of webbing is actually tan, and appears to be BlueWater:

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  4. ratagonia

    ratagonia

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    Thanks Willie. Here are the photos in-line.

    Willie01.

    Willie02.
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  5. Rapterman

    Rapterman

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    Whooa
    With the single black tracer thread webbing appears to be mil spec 5625 one inch tubular
    impossible to know manufacturer, but not Bluewater.
    Color fade = bad
    Thanks for posting, Willie!
    where did you find it?
  6. willie92708

    willie92708

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    Yes, the red webbing is clearly not BlueWater, some mil-spec webbing though. The other piece, which is tan where it was not Sun bleached, is BlueWater as best as I can tell. The weave and the faded double blue threads exactly match older BlueWater 1" climb-spec that I have. In this photo from left to right is: the red (maybe rust color?) mil-spec from the canyon, the tan BlueWater from the canyon, yellow BlueWater from the 1990's, purple BlueWater (last few years): IMG_3369x.
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  7. willie92708

    willie92708

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    Those 2 pieces of webbing came from a local SoCal canyon that's done maybe a handful of times a year:
    http://ropewiki.com/Muir_Ravine_(West)
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  8. Canyonero

    Canyonero

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    Thanks for sharing your experience. I just wanted to comment on something.

    Bounce testing is not appropriate for canyoneering anchors. The only application I know of where bounce testing is appropriate is in aid climbing. When aid climbing on moderately sketchy gear, the leader bounce tests each piece as they go. The theory is if it doesn't pull when bounce testing, then it won't pull when you fall on to it when bounce testing the piece above it.

    However, in canyoneering, you're going down, not up. So I just want to point out that "bounce testing" a deadman anchor is not good canyoneering practice. The correct canyoneering practice (which to your credit you also did) is to dig up the deadman, inspect it, rebuild it, and use some sort of back-up for everyone but the last person. Bounce testing not only doesn't ensure it won't fail as you rappel (I know of three instances now where webbing broke on something other than the first bounce or first rappeler) but actually makes it MORE likely to fail when you put your body weight on it from the wear you just put on it.

    Although to be honest, I really think deadman anchors are kind of a rookie anchor for several reasons.

    # 1 You're leaving webbing behind in the canyon, thus you can't ghost it if you're using deadmen.
    # 2 They're more difficult to back-up than ghosting anchors like meat, fiddlesticks, sandtraps, water pockets etc. (okay, it's not that hard, but it is slightly more difficult).
    # 3 They tempt following canyoneers to use the anchors without digging them up. Many beginning canyoneers assume that any anchors they come up on are bombproof. In reality, many canyoneers, especially experienced ones, rappel off anchors that are anything but bombproof. An anchor that holds the last 120 lb guy who already sent his pack down and slithered over the edge only to rappel smooth as silk is not necessarily going to hold the 225 lb guy with a 40 lb pack leaning back on the edge and bouncing his way down. The second might put 10 times the force on the anchor as the first.
    # 4 You can't observe an anchor that is underground while your buddies are rappelling. You don't know if the rocks are shifting or the webbing is slipping or tearing or whatever. Out of sight is, well, out of sight.
    # 5 The webbing for a deadman not only sits in the sun (the part out of the ground) but the part underground often sits around wet waiting for critters to chew on it. And the whole thing is often in the watercourse. These are not good characteristics for an anchor you hope will still be useable when you get to it.

    If it is all you've got, great, build a deadman as best you can. But I'd rather build and use my own sandtrap than dig up your old deadman, even if the deadman could potentially hold more weight. I'm not sure I can recall the last deadman anchor I used.
    Last edited: Nov 26, 2018
  9. ratagonia

    ratagonia

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    Please forgive my friend Canyonero, who has obviously never been to Death Valley. He is talking from a great deal of experience in one particular kind of canyon, and does not realize that his experience does not really apply to the canyons of Death Valley, which are completely different.

    Tom
  10. ratagonia

    ratagonia

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    I do want to put in my plug for the anchor type that works well in Death Valley: the "Modern Death Valley Cairn Anchor".

    The main benefit of the MDVCA is that the webbing is easily accessed and can be inspected and/or replaced with minimal effort. No more webbing coming out of the sand... well, in DV, there is only sand about 1/3 of the time.

    Perhaps someone could provide a picture.

    Tom
  11. Canyonero

    Canyonero

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    Are you suggesting bounce testing is appropriate in Death Valley rather than digging up the deadman? Methinks no.

    You must be just referring to my preference for sandtraps over deadmen. Obviously that doesn't work if there isn't sand and a cairn/deadman anchor it is.
    Last edited: Nov 26, 2018
  12. ratagonia

    ratagonia

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    A lot of what you said was smart and true everywhere, but the general thrust of your essay showed a lack of understanding of DV canyons.

    I think bounce testing is a weak and ineffective way of testing anchors. People that want to live would do well to thoroughly inspect the webbing on all DV anchors, which often means partially disassembling and re-assembling deadman anchors in Death Valley.

    These anchor failures fall into the category of "progressive failure". Meaning, it is not so much that the force was too high, it was a matter of the force was applied for too long a time. This can take a partial tear in weak webbing and finish the tearing. Or, when webbing is tied around a rock, perhaps the force eventually turn the rock in a direction that the webbing comes off. Another example is a wedged knot - as each person rappels on it, the knot gets a little tighter, and a little smaller. In some placements, this results in the knot-chock eventually pulling through.

    Tom
  13. willie92708

    willie92708

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    For the given anchor in the OP, I had no concern that the rock would move, as that rock easily weighs a few tons and is mostly buried flat in dirt.

    What concerned me is the webbing itself, and bounce testing the webbing caused it to fail. Sure it's not as precise as if I take the webbing to my pull test setup and measure the force before failure, but it does allow me in the field to put 2x to 3x body weight against the webbing and see what happens. If the webbing was in good shape, it would not fail under any amount of such bounce testing. However, since the webbing in question did fail at a force around 350 to 500 lbf, that's a BIG problem!

    Yes, I agree, even if the webbing holds up to a bounce test, that does not mean everything is good to go. Every inch of the webbing should be inspected for mechanical or other damage (UV). I've found anchors with new webbing as (of less than a few months) that rodents had chewed most of the way through on the back side of bushes or trees. Still, there are plenty of buried anchors where it would take 30 minutes to dig up all the fill dirt around the webbing to inspect it all (as such in the OP). There comes a point where inspecting what's exposed, bounce testing, and sequencing rappellers with a backup a meat anchor is what happens by choice.

    Overall this gets down to: Do you trust the webbing placed there some time ago or not? The easy approach is to replace it all, but this is the most time consuming, and totally overkill for bolted trade routes. For Death Valley canyons, it may be the only safe choice, unless you know that another party has replaced it all in the same season. For SoCal canyons, it varies all over since some canyons are heavily traveled (thus the webbing is replaced often anyway), deep under trees (thus get little Sun to UV bleach the webbing), and have lots of bolts, trees, or bushes to make inspection easy. Others (like the OP) see a handful of descents a year, the webbing sits in full Sun most of the day, and much of the webbing is buried under inches of dirt.

    Willie
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  14. willie92708

    willie92708

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    I just did this first descent on Sunday: http://ropewiki.com/Bear_Cloud_Canyon and we built many rock cairn anchors, because the bushes and cactus are badly rooted in very shallow soil (would not hold body weight), and all the big rocks were so rounded they did not have anything to loop webbing around. However, there were plenty of loose rocks in the 20 to 200 lbs range that worked great for quickly building rock cairns. Sure, the next party will have to disassemble them to inspect, but for the ones we built that will be a few minute job per anchor. Even if I had sandtrap bags, I would not have used them because it would take far longer to find enough dirt to fill them up. The soil is so thin and covered with so many nasty desert plants, it's not worth it!
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