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A slightly improved figure 8 contingency rigging

Discussion in 'Tech Tips and Gear' started by Tricam, Nov 24, 2020.

  1. Tricam

    Tricam

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    Problem/Background:
    When I first started diving into canyoneering-specific rigging methods, I became intrigued with contingency anchors. They are advertised as a solution to several problems that teams can encounter in canyons, and at face value, they seemed rather ingenious. "Rigging for rescue" was heavily promoted in some of the material I was learning from. I experimented with several common methods I found online and became a bit puzzled. Some common methods didn't seem to work at all. Others worked in certain circumstances, but could easily be accidentally released. With further research, I found several instances where releasable rigging was involved in accidents and deaths. At this point, my initial reaction was to completely dismiss them as unnecessary complexity for almost all circumstances - with the exception being "real" class C canyons.

    I still found them rather amusing, and I was curious why people used them regardless of their documented issues. I learned more about rope work, experimented with many different blocks, and I eventually came to the following conclusions (for myself):

    1. Riggings that rely entirely on non-locking friction are unreliable. Ropes and components wear in and conditions change. What worked once may not work the next time. An unexpected lack of friction in this type of rigging has been implicated in at least one accident.
    2. Riggings that rely on a lock created by two non-fixed components are unreliable. Many "blocks" do not have a fixed lock as a part of their design, but rely on the lock provided by the rope being pinched between the anchor and the "block" device (demonstration of some non-locking configuration, another "block" that relies on the interaction with the anchor). External factors such as movement and rock geometry can cause this lock to release under load. If this is the only locking mechanism in the system, it becomes dependent on friction alone to hold the load, which is unreliable per #1. This scenario likely contributed to at least one fatality.
    3. Releasable rigging should be easily releasable. For a contingency rigging to provide value, it must be easy to release into a lower. Some common riggings (including the "standard" locking figure 8 block) address #1 and #2 but are not easily releasable (example). In the case of the standard figure 8 block, this happens because the strand that you need to loosen in order to release to lower is locked by a strand that is under load when the system is weighted. This has been an issue in at least one incident.
    4. Riggings should be easy to inspect. Visual complexity is difficult to verify, and the human eye is good at spotting symmetry. This is why a figure 8 knot is easy to inspect. Un-inspected riggings have been involved in accidents.
    5. Riggings should not depend on specific hardware. (a bit of personal opinion) Being dependent on a single piece of hardware is a liability, since it could be forgotten or lost. Ideal riggings should be able to be constructed with materials commonly on hand in canyons, which includes carabiners, rope, slings, and figure 8-style rappel devices.
    Possible Solution:
    The below is a block that can be constructed with figure 8 style devices that I have not yet seen elsewhere. I came across this after being disappointed that most existing designs I could find not meeting the above criteria. It is based on the Secure Compact figure 8 block, but it adds a locking half twist in the last bight. This locking twist occurs entirely on the non-load bearing side of the lock created between the block and the anchor, so it is trivial to release under load.

    I find this variation very easy to inspect because it has a symmetric appearance (although it isn't truly symmetric). It is also easy to inspect the critical piece (the lock) by asking the following: Does the rope form an obvious "X" on top pinching the exit strand?

    This also can be constructed with most any figure 8 style device you may have on hand and is not particularly dependent on features of a single device. (I find the Euro 8 rather slick, but it requires a "classic" figure 8 device, where the small hole is large enough for a bite of rope to fit through). This style works with common rope sizes, tested with 8-11mm.

    [​IMG]


    With 8mm and 11mm rope, resepctively:
    [​IMG]

    With various figure 8 style devices (probably works with other common devices, but unverified):
    [​IMG]

    Notes:
    • I generally would prefer a MMO which also meets all of my criteria, but there are some benefits of using a device (smoother, less rope twist, less rope-on-rope friction, does not require re-rigging for LAPAR)
    • I would still always secure the bag side of this (or any) releasable block, unless the tail is being actively managed by someone at the anchor
    • I wanted to share this because I was rather disturbed with the number of accidents involving contingency anchors. It is possible that this or other solutions are well known in the "real world", but the readily searchable information I could find online left a lot to be desired.
    Last edited: Nov 24, 2020
  2. vanyoneer

    vanyoneer

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    Bumping this thread to the top. Tricam, how has this rigging worked for you? Over the past months I have experimented with the various ropewiki 8 blocks and found yours to be the best to date. I have one improvement to offer, which is to add an initial "double" as shown below.

    [​IMG]


    [​IMG]
    Last edited: Aug 9, 2021
  3. SRappel

    SRappel

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    Hi vanyoneer, what is the advantage of adding an double?
  4. vanyoneer

    vanyoneer

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    The most recent development in figure-8 block methodology was to add a "twist" to the last wrap to add a ton of additional friction and prevent the rope from slipping. (this had the added benefit of constricting the wraps and preventing cyclic loading from inadvertently dislodging a wrap off the figure 8).

    The twist caused so much friction that the block couldn't be released under load, defeating the purpose of rigging an 8 block. Back to the drawing board!

    The flaw with the twist is that it is too far upstream in the rigging. Rope goes through the link, through the big hole, around and through the big hole again, and then twist. All of those steps prior to the twist don't induce enough friction. When a rappeller jolts weight on the block, the rope microscopically starts creeping through each of these relatively low friction wraps until the rope begins to creep at the twist, which will creep until cinched tight and prevent further creep, but be too tight to release.

    However, the twist is a flaw worth keeping because the cinch toward the tail end is great in keeping things from shaking loose, it's necessary if you ask me.

    To fix this flaw, ideally the first wrap is the highest friction wrap, and ideally more friction than each consecutive wrap, and certainly more than last twist, such that the twist is holding no more than a feather's load, nor should any rappelling jolt induce creep and cause the twist to cinch. But if you are a superhuman, big boned canyoneering monster the twist should constrict and save you from the rope slipping, at the cost of a harder-to-release contingency (but hey, probably even with a big guy it might be easy to release. Never tested it on more than 180lbs).

    Long story short, the double is a first step wrap that gives a ton of up-front friction that works symbiotically with the twist.
  5. TCarlisle

    TCarlisle

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    Location:
    SLC
    I had a thought, which is just an idea that hasn't been tested yet so don't eat me alive for this; but I'm wondering if the idea has potential. What about combining the benefits of a MMO (Munter, Mule, Overhand) and a Figure 8/Euro 8 block by rigging the figure 8 device as normal and then adding a mule hitch through the small hole of the figure 8 device to lock it off followed by overhand knot for a backup?

    Theoretical Advantages:
    • Smooth lowering operations via the figure 8 device
    • Mule hitch for holding/lock-off
    • Easy release under load
    • Less likely to have rope jammed between the figure 8 device and the rapide, rock, etc.
    Theoretical Disadvantages:
    • Bulky knot and or loop from the overhand backup could get stuck on the pull (however a standard Figure 8 block has a carabiner in this position that also presents a similar issue)
    • Might not work will all figure 8 devices and rope combinations
    I quickly rigged it in the driveway so that you can have an image of what I'm talking about.

    Attached Files:

    • EMO Block.
      Filename:
      EMO Block.jpg
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      208.6 KB
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    Kuenn likes this.
  6. Brian in SLC

    Brian in SLC Brian in SLC

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    I guess one of my concerns...besides it being "theoretical" (ha ha), is...how easy is it really to release? Also, once released, if you need to secure the rope again, with a load, how easy is it to go back? Might be hard to poke the rope back through that small hole if you're holding a full canyoneer's body weight.

    If you've got a quickdraw clipped to the small hole for whatever reason...would also defeat being able to use the keeper hole. Also, if the keeper hole of the eight was in use, you wouldn't be able to clip into it if you needed to (for whatever reason).

    upload_2021-9-16_14-25-33.

    Interesting thought, though. Back in the day, was a period in time between hip belays for climbing, and, using a figure eight. A bunch of folks (me included), used the small end of a figure eight for belaying like a sticht plate. Was pretty effective. Then, ATC's and their ilk came out and figure eights went the way of the dodo for most climbers.

    I like and have used (and have been used...ha ha) a figure eight for a contingency on a canyon anchor. Pretty smooth and controllable, especially with a larger diameter rope. Really common for places where slipping the rope whilst on rappel keeps the rope from getting damaged when someone is rappelling and the rock is kinda sharp.

    Honestly have never figured out why folks would block a rope to rappel single when they could use a contingency anchor but that's another issue...

    Anyhow, for me, I want whatever contingency I use to be bomber when its secured, and, smooth and easy to undo and convert to lower with a load. Also want to be able to re-secure it easily even under a load.

    Just thinking out loud...for me, I kinda like to have that small hole in the eight open for clipping into. Which, would negate your option.

    Good thoughts!
  7. vanyoneer

    vanyoneer

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    I made a video describing the method in this thread, it went live today, and a canyoneer responded that this method would cause deaths in class C canyons and I should remove the video (I did). He thinks the "capturing twist" will cinch down and be un-releasable in an emergency waterfall lower. I invited him to post here.

    From ropewiki:

    This seems like valid advice for a class C situation (and I admit, I didn't address C canyons in my video), however the accusation at hand is specifically the ability (or inability) to release a "capturing twist" under load. If the "capturing twist" can be released under load, then the above ropewiki quote is moot. Besides, I can imagine about a dozen things I'd rather be doing than sitting next to the anchor with a leg wrapped up.

    I can find evidence that the older 8 blocks (i.e. the method Petzl used to suggest in their "canyoning" tech tips but since removed) become unreleasable with the "capturing twist" cinching too tight but I have not been able to induce Tricam's rigging shown here (which is the same as the "compact secure" method on ropewiki but with the added twist) to fail. Especially if you add the double wrap as shown in the images I posted above.

    Am I missing something obvious/do you have experience enough to shed light on class C flowing water rigging experiences that would show that I am wrong for suggesting this method of 8 block? As far as I can tell, a "capturing twist" would have saved at least one person's life (salamander accident). Maybe the twist would have killed more people as my naysayer suggests. Thoughts?

    (Edit to add, looks like 9 years ago on Bogley was the last time this stuff was developed: http://www.bogley.com/forum/showthr...-Report-Rigging-Failure-During-a-Rappel/page8
    "bjp" mentions the "compact secure" setup in the very last post)
    Last edited: Sep 30, 2021
  8. Tricam

    Tricam

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    I haven't been able to get out west this year (due to a baby resulting from last year's trip :) ) but I've been checking in periodically, hoping to take a trip to Utah in the spring once the grandmas can handle the baby :D

    The way this block is designed, the rope-on-rope capturing twist is a secondary blocking mechanism that occurs entirely on the low-tension side of the primary block caused by the rapide pinching the rope against the figure 8. The rope on rope block will only ever engage if the figure 8 device has gotten "stuck" away from the rapide. At an actively managed anchor in a class C situation, I would assume that:

    1. The person managing the anchor would ensure that the figure 8 is properly positioned during an active rappel.
    2. The person managing the anchor would be able to manipulate the bag-side of the rope with body weight to un-stuck it, if it happened.

    Once the primary rapide-based block is engaged, tension is removed from the secondary block, which would allow it to be easily released. I would be glad to hear if there is reason to suspect this may not be the case.

    ---

    All that said, I think that serious class C canyons require a significantly different skillset and risk assessment, almost to a point where it is a different sport. I would suspect "best practice" between the two environments to be significantly different.
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