Accident Report - Rigging Failure During a Rappel

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Originally Posted by Brian in SLC

The figure eight, as far as I know it, its pretty "locked off" when you twist and put a sort of half hitch into it to secure the loop. And, I have always seen folks then clip that off as well, securing it for all but the last person.

Who has a good photo of a locked off figure eight, or, the current Stefan Hofmann riggin' of it? Post up!

Thanks.

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Perhaps the photos by unripecoconut on the "Figure 8 block with lower" (7/30/2011) thread? A rigging/knot is "locked" when a strand with more tension is pinning a strand with less tension against something else. So it looks to me like the first picture in that thread is not locked off, nor is the demonstration in cerberuscanyons. Tom seems to think it's not important whether the figure 8 block is strictly locked off -- see 4/30/2012 response to unripecoconut on the same thread.

Putting a clove hitch in when securing it to the loop would certainly do the job :) A clove hitch is a great example of locking -- the only thing it does is pin the lower-tension strand against the thing it's hitched on using the higher-tension strand.

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Originally Posted by ratagonia

You're talking apples and pomegranates.

Sandtrap:

.......
Joker/Jester:
.......

That would be a nice system, if it worked.

Tom

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Tom, it does work. It really does. My compairison was not apples to pomegranates in the sense of equipment to equipment but the comments against the sand trap and the comments against the Jester seem to be very, very similar --particularly by those who haven't tried it (or them). This accident is quite the head-scratcher for me since I have actually used the Jester multiple time to send people, youth and adults alike, down rappels, the most recent a group of twenty or so girls. Not even a tiny slip of the rope. I know, I watch these things like a hawk. Liability is/ was a major concern for someone like me. :haha: Just for fun, I think I will mark the rope at the rapide and then check the back and forth of the raps when I use this again. *edit. I think I will add a biner block just to complicate things more on each strand just in case as I test this thing out with my ropes. Off to my swing set this evening. Wish I had a video... well actually I don't. This will look pretty stupid to the neighbors. :haha:

Bjp - you have test equipment?

Tom

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Originally Posted by ratagonia

You're talking apples and pomegranates.

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Point taken -- fancy anchors are for special circumstances and users are taught to be extremely careful with them, while the Jester may have been represented as a rope-agnostic tool that can be used often. People should take note of ag23's discovery that friction slipping occurs in the Jester at unacceptably low tension with some ropes.

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Originally Posted by ratagonia

Joker/Jester:


This is a technique that people are trained to, using a specific piece of gear (Totem)

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Well, I use it all the time using two overlapping opposed standard figure 8's (not a Totem). And my use case is the same -- beginners in large groups. So, I'd definitely be interested in whether you think the Joker is also a rigging that people shouldn't be using frequently.

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Originally Posted by ratagonia

The Figure-8 blocks I have seen have an extra loop of rope that acts as a lock. It is not just friction partly because there is rope-across-rope interaction that tends to lock with more force.

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It's not just rope-on-rope that does the locking, it's high-tension on low-tension (like in the clove hitch). Most figure 8 blocks I've seen don't have this locking feature -- I'd be interested to see a picture of one that does.

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Originally Posted by ratagonia

To me, the other difference is that the Jester method is offered in a place where many other riggings could be used. Does this have advantages over other methods? Yeah, I can see that it would be great to have a system that sets up quickly, allows both strands to be used independently back and forth, AND provides contingency setup on each of those strands. That would be a nice system, if it worked.

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Well, we can essentially always come up with other ways of doing things; it's just a matter of which way has the most advantages (including such advantages as "I know how to do it this way") How do you defined "worked"? Clearly the Jester doesn't work with all ropes and rigging variations, as ag23 has shown. But it works with a lot, and so does the Joker.

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Originally Posted by ratagonia

Bjp - you have test equipment?

Tom

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Sorta -- a 2000 pound tension gauge and a come-along. I occasionally have access to a 10k pound puller.

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Originally Posted by Scott Card

Tom, it does work. It really does. My compairison was not apples to pomegranates in the sense of equipment to equipment but the comments against the sand trap and the comments against the Jester seem to be very, very similar --particularly by those who haven't tried it (or them). This accident is quite the head-scratcher for me since I have actually used the Jester multiple time to send people, youth and adults alike, down rappels, the most recent a group of twenty or so girls. Not even a tiny slip of the rope. I know, I watch these things like a hawk. Liability is/ was a major concern for someone like me. :haha: Just for fun, I think I will mark the rope at the rapide and then check the back and forth of the raps when I use this again.

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I see your point, but...

I would say that we have an instance of it failing, therefore it is incorrect to say "it works". You have used it extensively, and it has NOT YET failed on you. I think this is a good thing.

I hope to do some testing on Sunday if we can find the dynamometer.

My suspicion is that the method is not "robust". Like Humpty-Dumpty, I have my own meaning for this word. The Jester fails under some circumstances. We have not yet revealed which circumstances. My suspicion is that the small rigging variations Andre made coupled with a new, smallish rope yielded a failure. A robust system is one that can be rigged slightly wrong or used with carabiners and ropes that are a little off-the-norm, and still work.

Now that YOU have been notified that there is a possibility it does not work in all reasonable circumstances, may I presume that you CANNOT use it until this has been investigated fully, and you will be going back to the Stone?

Tom

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Originally Posted by ratagonia

I see your point, but...

I would say that we have an instance of it failing, therefore it is incorrect to say "it works". You have used it extensively, and it has NOT YET failed on you. I think this is a good thing.

I hope to do some testing on Sunday if we can find the dynamometer.

My suspicion is that the method is not "robust". Like Humpty-Dumpty, I have my own meaning for this word. The Jester fails under some circumstances. We have not yet revealed which circumstances. My suspicion is that the small rigging variations Andre made coupled with a new, smallish rope yielded a failure. A robust system is one that can be rigged slightly wrong or used with carabiners and ropes that are a little off-the-norm, and still work.

Now that YOU have been notified that there is a possibility it does not work in all reasonable circumstances, may I presume that you CANNOT use it until this has been investigated fully, and you will be going back to the Stone?

Tom

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Hence my edited comment above... isn't the answer a biner block? :lol8: I will test it on myself under a controlled environment with soft grass below my swingset hut. :crazy: This sounds down-right scientific! Prepare for a big boned canyoneers' findings to come.

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Originally Posted by Scott Card

Hence my edited comment above... isn't the answer a biner block? :lol8: I will test it on myself under a controlled environment with soft grass below my swingset hut. :crazy: This sounds down-right scientific! Prepare for a big boned canyoneers' findings to come.

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I use a Stone Knot as my #1 rigging these days. Biner block #2.

T

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Originally Posted by ratagonia

I hope to do some testing on Sunday if we can find the dynamometer.

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If you have extra time/patience, I would personally find it extremely useful if you might consider testing the opposed-figure 8's version of the Joker. If you can't, I'll try testing it next time I pull on stuff.

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Originally Posted by bjp

How do you defined "worked"? Clearly the Jester doesn't work with all ropes and rigging variations, as ag23 has shown. But it works with a lot, and so does the Joker.

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I have a higher standard than "works with a lot".

Could you post a picture of the Joker you are using? Or is it the Jester?

Tom

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Originally Posted by ratagonia

I use a Stone Knot as my #1 rigging these days. Biner block #2.

T

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I need to learn the convert to lower from a Stone Knot you speak of. That one for sure I can't picture in my mind.

Maybe Brian could post a picture (however poor) of the Figure-8 block method he is currently using.

Tom

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Originally Posted by ratagonia

Could you post a picture of the Joker you are using? Or is it the Jester?

Tom

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I use the Joker; I don't have a Totem. I'll try to take one tonight. In terms of a description: start with the rappel rope passed through the quick link. Clip one side of a quick draw onto the shelf of an anchor and the other end to the big holes of two figure 8's. Rotate each of the figure 8's 90 degrees in opposite directions so that the little holes are on opposite sides but the big holes are still overlapping ("Mickey ears"). Make a bight on one of the rope strands, pass it through the big holes, and then around the little hole of one of the figure 8's just like you would when rigging for rappel. Repeat symmetrically for the other strand. Clip a quick draw to both little holes as a safety if desired.

Basically, it's identical to the Jester except that the two sticht plate friction points are replaced with figure 8's. But come to think of it, I'm not sure why the big and little holes couldn't be reversed for a bit more friction; I'll have to try that.

Also, looks like I'll be able to use the 10k puller next week. I have the samples of all your ropes; want anything broken? :)

Fiddlin' about...here's the Rock Exotica smallish eight, rigged with a tie off on the T post. Kinda neat:

Attachment 57035

ATS rigged ala Jester, methinks:

Attachment 57036

Some rap device (Trango?) rigged ala Jester as well, methinks:

Attachment 57037

Note the two above don't hold me, but, slip when rappelling single strand. Tom, recognize the cord? Its your old friend the teal trail line! 8mm. My guess is the friction holding of the Jester is very (VERY) rope diameter, and, maybe rappeller weight, dependant.

How I've rigged an eight, but, not sure if other folk do it this way, or, that its Stefan's way:

Attachment 57038

Cheers!

Thanks.

Yes, nice Teal "Trail Line". What a piece of junk. Sorry I ever had anything to do with that. I would call it 7.5mm by today's standards!

T

Yeah, that rope is the one we harvested from being cut off and left in a canyon. Great for living room/stairwell use!

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Originally Posted by BW123

Hey Beck! Did I say that I use the thing? And why am I suddenly having to defend learning basic techniques (this is not a basic technique but rather a use for the totem) ? In the context of these Canyoneering courses, a lot is thrown at relative beginners over a short amount of time including the use of many devices. BTW...I like the M/M but if you are stupid, you could really screw that up too!

BW

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I apologize BW. I read what you said about Rich showing you 5 incorrect ways that the Jester could be set up, and just wanted clarification as to the correct way so that if at any time I was with someone insisting that we use this system, I might be able to understand if it were rigged properly or not? Once again...no mal-intent directed toward you.

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Originally Posted by rcwild

Forgive me if I spoil anyone's fun by providing accurate information ...

https://www.facebook.com/AmericanCan...ingAssociation

Feel free to copy any of the Jester rigging photos from the Facebook page and paste them here to continue your discussion.

Carry on.

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Thank you very much Rich!!!!!! You've answered my question which seems to be eluded to in this conversation! Makes total sense what this rigging is used for now!

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Originally Posted by Scott Card

I need to learn the convert to lower from a Stone Knot you speak of. That one for sure I can't picture in my mind.

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X2 :hmm2:

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Originally Posted by bjp

The Jester and Joker are releasable versions of the Stone knot -- all three isolate both strands allowing people to rappel on either strand while the Munter/Mule does not. The reason one might want the option to rappel on both strands is to have someone rappelling at all times in a big group; the next person rigs while the previous person is on rappel. This is extremely useful in certain circumstances, like taking a group of 12 through Little Santa Anita with 10-12 small rappels.

I can only speak from personal experience, but I find it much easier to rig, teach others to rig, and check the Joker than a Munter/Mule. Like the Joker, the Jester essentially has just 3 simple steps -- clip Totem to anchor, push rope into sticht slots, clip carabiner through bights. The Munter/Mule has 4 steps and more details to get right -- clip quickdraw to anchor, tie Munter with rappel strand to lower carabiner, tie a slip knot with a bight from between the lower carabiner and quickdraw, tie an overhand with bight.

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Ah, you forgot the new important fourth step, hope it holds and pray you don't die. :lol8: I joke, I joke...

Really, this is the best "for" argument on the thread so far. I'm not sold yet, but thanks bjp for answering my question.

I'm looking forward to these fancy test results. :popcorn:

:popcorn:

__

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Originally Posted by Brian in SLC

ATS rigged ala Jester, methinks

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Looks equivalent to the Totem version to me.

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Originally Posted by Brian in SLC

How I've rigged an eight, but, not sure if other folk do it this way, or, that its Stefan's way

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Thanks for the great pictures. However, I still don't think this eight block is "locked". I've colored the rope according to how much tension is on it, for both the clove hitch and your eight block (I'm not sure which way the strands go in your eight block, so I have two versions; they differ only by a half-twist of the final bight):
Attachment 57041
Attachment 57042Attachment 57043

In the clove hitch, note that a high-tension part of the rope (the diagonal segment) is on top of a lower-tension part of the rope (the vertical segment on the left) -- this is what locks/pins it to the bar. In the eight block, there is no high-tension part on top of a lower-tension part (or rather, there is no low-tension part in between the figure 8 and a high-tension part) -- it is not locked to the figure 8. For this reason, I would put the figure 8 block in the "non-locking" category along with the Joker, Jester, etc, and since I trust the figure 8 block (and it seems like pretty much everyone else does too), I don't think it's reasonable to categorically call the Jester unsafe simply because it doesn't lock. It may or may not be safe for other reasons (such as not providing enough friction), but unless I'm missing something, I take issue with this statement:

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Originally Posted by ratagonia

I don't see how you can look at this and NOT be scared. There is no mechanism that 'locks' it.

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I guess we disagree on what it means for something to lock.

As someone said - if you pull on it and it will go to full strength without slipping, it is (de facto) locked.

If you pull on it and at some force it starts to slip, it is (de facto) NOT locked.

Figure8 block - Locked (pretty sure). Because rope crosses rope, and the way the rope crosses rope.

Tom :moses:

p.s. Nice coloring job...

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Originally Posted by ratagonia

I guess we disagree on what it means for something to lock.

As someone said - if you pull on it and it will go to full strength without slipping, it is (de facto) locked.

If you pull on it and at some force it starts to slip, it is (de facto) NOT locked.

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Hmm, yes, we have different definitions. The key difference is that a rigging could be Tom-locked with one size of rope and not-Tom-locked with another size of rope. If a rigging is Ben-locked with one size of rope, it should be Ben-locked for all sizes of rope. So when we observe that the Jester is not Tom-locked with new, thin rope, that doesn't really tell us much about whether the Jester is Tom-locked with thicker, standard rope. In fact, "full strength" is relative; perhaps the Jester IS Tom-locked for new, thin rope if the system includes a sand trap ;)

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Originally Posted by ratagonia

Figure8 block - Locked (pretty sure).

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Interesting; I'm inclined to think it's not Tom-locked under some circumstances. I'll test and report.

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Originally Posted by ratagonia

Because rope crosses rope, and the way the rope crosses rope.

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Surely this isn't the reason it's locked. I can easily create a Tom-locked anchor where rope never crosses rope -- just put 6 normally-rigged figure 8's on a rope, one after another.

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Originally Posted by bjp

Hmm, yes, we have different definitions. The key difference is that a rigging could be Tom-locked with one size of rope and not-Tom-locked with another size of rope. If a rigging is Ben-locked with one size of rope, it should be Ben-locked for all sizes of rope. So when we observe that the Jester is not Tom-locked with new, thin rope, that doesn't really tell us much about whether the Jester is Tom-locked with thicker, standard rope. In fact, "full strength" is relative; perhaps the Jester IS Tom-locked for new, thin rope if the system includes a sand trap ;)

Interesting; I'm inclined to think it's not Tom-locked under some circumstances. I'll test and report.

Surely this isn't the reason it's locked. I can easily create a Tom-locked anchor where rope never crosses rope -- just put 6 normally-rigged figure 8's on a rope, one after another.

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"Full Strength"

"Going to full strength" in testing means that the rope breaks. If your anchor or test fixture breaks, that means you did a poor job of setting up the test. If I break my telephone pole anchor, I am in big trouble.

A system is much more useful if it "locks" independent of rope size. Knowing that the Jester works for some ropes but not for others is not real useful to ME - I want my rigging things to work with all (reasonable) sizes of rope. Wet or dry, new or well-used, full moon or new moon.

I think we are talking past each other, BJP. Perhaps some actual testing, rather than more talking would be a good idea, and would clarify meaning. No, tom-locked should be independent of rope size. Yes, it is possible to make something that locks without rope crossing rope, but that would be the difficult way. Most systems that "lock" have rope crossing rope.

"just put 6 normally-rigged figure 8's on a rope, one after another"

Our discussion has progressed to the "extension to absurdity" - suggesting that more back and forth is unlikely to be fruitful.

Tom

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Originally Posted by Deathcricket

..... I am hard pressed to see the ANY difference between the 2 setups....

(pics)

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One thing I noticed is the rapide in Andre's version is through the top biner and perpendicular to it, while the rapide & top biner are parallel in Rich's pic. Not sure what effect this would have on the system.

Disclaimer: I have used the Totem in several ways, but never as a jester.

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Originally Posted by ratagonia

...A system is much more useful if it "locks" independent of rope size. ...

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I have used the Totem in ascending mode with two different diameters of rope and overall I love the Totem. However, to my dismay, the Totem does slip when using the 8.3 MM rope. I thought I could use it for this use on all my ropes, but after noticing this, I am thinking I may need a device for that purpose.

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Originally Posted by bjp

Looks equivalent to the Totem version to me.

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Isn't the "Jester" a method for the "Totem"? I ask out of ignorance...

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Originally Posted by bjp

Thanks for the great pictures. However, I still don't think this eight block is "locked". I've colored the rope according to how much tension is on it

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As the kids say (or, Kenny on South Park), thats "hella cool!"

I think mine's on the bottom, as, there's a half twist finish on my loop.

I get my full weight on the rappel strand, and, static on that, I just set there. Then, I can undo and lower easily whilst my full weight is on the rope. I like it. Also, for back up, out of the photo to the left, there's a clove hitch on a 'biner for back up.

Thanks for the "color" commentary!

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Originally Posted by Brian in SLC

Isn't the "Jester" a method for the "Totem"? I ask out of ignorance...

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The "Jester" is a rigging technology, that could be implemented with any piece of metal with appropriate geometry.

Tom

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Originally Posted by ratagonia

Could you post a picture of the Joker you are using?

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Joker:
Attachment 57069

Seems Andre should have taken more than one photo and/or taken better notes and/or paid more attention during the course. I told his class, just like I tell every other class, that the Jester provides the core rigging system for a variety of applications. It can be used for lowering, single-rope contingency, double-rope contingency, creeping the rope with depth gauge, rigging plate for top rope belay, rigging plate for converting contingency to haul, etc. etc. etc.

I told Andre's class, just like I have told every other class, that the Jester, (correctly) rigged only in "core" mode slipped when I tested it in single-rope contingency mode with narrower diameter ropes (8mm Canyon Pro DS). Until someone is sure how it will behave with their particular rope, it should be either minded or tied off -- when used for single-rope contingency. Even if you are confident your rope won't slip in single-rope contingency mode, it only takes an extra 10 seconds to tie it off, so why not?

Needless to say (at least for those who understand the techniques) it is not necessary to tie off if it is rigged for creeping the rope or double-rope contingency.

After making all of those points, the students practiced with it using 8.9-9.2mm ropes. Their concerns went from "will it be enough friction" to "there is too much friction to lower". I demonstrated the normal-friction lowering mode and another low-friction lowering mode.

The Totem WORKS for rappelling and rigging with ropes from 8mm to 10mm. The Jester rigging system WORKS with ropes from 8mm to 10mm. Like virtually all devices, it is rigged differently to accommodate its diameter range. Kinda like how you need to rig a figure eight differently with various diameters, how you need to rig an ATC differently with various diameters, etc.

The Jester WORKS when it is used correctly (which includes minding it or tying it off when rigged in single-rope contingency mode, especially with narrow diameter ropes). It might not work when it is used incorrectly.

Stone Knot works when it is used correctly. It might not when it is used incorrectly. MaxxiPad works when it is used correctly. Might not when it is used incorrectly. Water version of MaxxiPad works when it is used correctly. Might not (did not?) when it is used incorrectly. Figure eight knot works when it is tied correctly. Might not when it is tied incorrectly. Etc. Etc. Etc.

I have been teaching the munter-mule since 1994 and can demonstrate at least 5 common mistakes people make when rigging it. Quite a few people avoid using it because they are not confident with their ability to do it correctly. The Jester is much much simpler to rig than a munter-mule. I can teach anyone the core Jester rigging system in a couple minutes and have never seen anyone get it wrong. Until now.

In future courses I will be showing Andre's photo to point out how improper rigging can cause problems. I will also make it a point to have people use the Jester with 8mm rope to add emphasis to my points about minding or tying off.

I learned the Stein Knoten (Stone Knot) in Austria in 1999 and taught it to Tom several years ago. Surprised to hear that it is anyone's "go-to" rigging. Converting it to lower in 2.X minutes? That's an okay time, unless there is water present and the rappeller in distress can't hold his breath that long. Jester will do everything the Stone Knot will do and much much much more. Lowering takes a couple seconds. In well under one minute I can solve the distressed rappeller's problem without lowering him more than a couple feet. Even converting to haul can be done well under 2.X minutes.

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Originally Posted by bjp

Joker:

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Ben,

Try threading the rope on the right from front to back so the loop is on the front side of the neck on the figure eight. Opposing loops will hold the figure eights in position more securely. Not a big deal most of the time, but on occasion (like when the rigging is pressed up against the rock) it can make a difference.

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Originally Posted by deagol

One thing I noticed is the rapide in Andre's version is through the top biner and perpendicular to it, while the rapide & top biner are parallel in Rich's pic. Not sure what effect this would have on the system.

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Doesn't make any discernible difference in friction.

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Originally Posted by deagol

I have used the Totem in ascending mode with two different diameters of rope and overall I love the Totem. However, to my dismay, the Totem does slip when using the 8.3 MM rope. I thought I could use it for this use on all my ropes, but after noticing this, I am thinking I may need a device for that purpose.

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Which ascending system are you using? Stop-n-Go or Plaquette (autoblock).

When the Totem first came out, students were coming up with dozens and dozens of ways to use it. That was cool, but I now teach just a handful of what I consider to be the most beneficial uses. If you know you need to ascend, use ascenders. I only use the Totem in ascending mode if I need to go up and come right back down or visa versa.

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Originally Posted by ratagonia

A system is much more useful if it "locks" independent of rope size. Knowing that the Jester works for some ropes but not for others is not real useful to ME - I want my rigging things to work with all (reasonable) sizes of rope. Wet or dry, new or well-used, full moon or new moon.

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That is a sufficient but not necessary condition for a good system. The figure 8 block does not work (lock) with all sizes of rope, particularly under certain moons (when something gets between the quick link and the figure 8). Yet I still think it's a perfectly good system when used appropriately -- likewise with the Joker, which (almost) never locks. If you don't want to watch the whole video explanation, just check out 2:38 to 3:46:
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EDIT: I've removed the video because it showed a version of the figure 8 block which does not lock when not pulled against the quick link; Tom's version a few posts below is a better rigging.

For historical purposes, the key portion of the video showed a non-locking figure 8 block jammed against a quicklink using 8.3mm Canyon Fire rope; that configuration locks by squeezing the rope between the figure 8 and quick link. When the figure 8 block is suspended above the quick link so that the figure 8 can't squeeze the rope against the quick link, the rope easily (perhaps 50-70 pounds) pulls through the figure 8 block.
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To recap:
1) A locking system always must have a strand or component with higher tension/force squeezing a strand with lower tension
2) The figure 8 block's locking mechanism is squeezing a lower-tension strand between the quick link and figure 8
3) This mechanism does not necessarily occur in all riggings of the figure 8 block
4) A system does not need to be locked to supply friction force greater than the breaking strength of the rope
5) Not all systems/situations require that the supplied friction force exceed the breaking strength of the rope
6) The Joker and Jester are both non-locking systems that supply less friction force than the breaking strength of the rope under most circumstances
7) Particularly on the Jester (and probably on the Joker; not yet tested), there are some reasonable rope and rigging combinations where the supplied friction force is not sufficient

Thanks to ag23 for letting everyone know about #7.

Like Rich said, moral is block it off. But I would say always, even when using both sides. If the system works as advertised, you should be able to get a biner block or a mule hitch off of it, right? Doesn't matter if your rope is thick. I'm not experienced with these types of riggings, but common sense tells me that if a system is at all dependent on rope size, you should be extraordinarily careful with it.

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Originally Posted by dustinsc

Like Rich said, moral is block it off. But I would say always. Doesn't matter if your rope is thick. I'm not experienced with these types of riggings, but common sense tells me that if a system is at all dependent on rope size, you should be extraordinarily careful with it.

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Lotsa variables in any system. Rope: diameter, stiffness, state of wear, wet or dry, new or used, dirty, icy, etc. How worn is the friction device(s), and so on.

Question for the Joker/Jester users out there: is there a significant advantage gained by NOT tying off?

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Originally Posted by hank moon

Lotsa variables in any system. Rope: diameter, stiffness, state of wear, wet or dry, new or used, dirty, icy, etc. How worn is the friction device(s), and so on.

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Let me roll it back then. If a system is that dependent on the metal on rope friction, then you should be especially careful. Not that you should ever be lackadaisical with any system....

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Originally Posted by hank moon

Lotsa variables in any system. Rope: diameter, stiffness, state of wear, wet or dry, new or used, dirty, icy, etc. How worn is the friction device(s), and so on.

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I read that as.... a lot of different ways this system can fail. :eek2:

Most folks only have one large chip to wager with in the big game of life.... bet yours wisely.

:popcorn:

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Originally Posted by bjp

That is a sufficient but not necessary condition for a good system. The figure 8 block does not work (lock) with all sizes of rope, particularly under certain moons (when something gets between the quick link and the figure 8). Yet I still think it's a perfectly good system when used appropriately -- likewise with the Joker, which (almost) never locks. If you don't want to watch the whole video explanation, just check out 2:38 to 3:46:

To recap:
1) A locking system always must have a strand or component with higher tension/force squeezing a strand with lower tension
2) The figure 8 block's locking mechanism is squeezing a lower-tension strand between the quick link and figure 8
3) This mechanism does not necessarily occur in all riggings of the figure 8 block
4) A system does not need to be locked to supply friction force greater than the breaking strength of the rope
5) Not all systems/situations require that the supplied friction force exceed the breaking strength of the rope
6) The Joker and Jester are both non-locking systems that supply less friction force than the breaking strength of the rope under most circumstances
7) Particularly on the Jester (and probably on the Joker; not yet tested), there are some reasonable rope and rigging combinations where the supplied friction force is not sufficient

Thanks to ag23 for letting everyone know about #7.

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Thank you for your efforts BJP.

However, you make some assertions that I think I can be demonstrate to be false:

"1) A locking system always must have a strand or component with higher tension/force squeezing a strand with lower tension"

Rats! A careful reading notices the phrase "or component" in there, which makes my dis-proof a non-dis-proof. But here it is anyway, the Garda Knot, which has no ropes crossing but still locks even on 3mm cord:

(Pictures 1 and 2 below, if I got them to load in the right order).

"2) The figure 8 block's locking mechanism is squeezing a lower-tension strand between the quick link and figure 8"

Well, I suppose, if you use the NON-LOCKING FIGURE-8-BLOCK, then the only locking mechanism is that. However, why would you use that? With a simple half-twist, you can make a LOCKING FIGURE-8-BLOCK, which seems to have all the bene's of the non-locking version, plus the benefit that it locks, no matter what the cord size.

(LATE ADDITION:
EXCEPT, as Benjamin has pointed out in a separate conversation, it is no longer a contingency anchor because it does not release! :facepalm1:

Tom
)

(see the rest of the pictures, below).

I personally do not use Figure-8-blocks, though I suppose I should practice it some so if I canyoneer in Ouray with Brian, I won't be surprised...

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AND - perhaps you noticed that I did not prove my thesis. Correct. That was not the point. The point was to provide an example of a locking, non-rope-crossing system to refute the claim I THOUGHT you made; and to present a locking version of the Figure-8-block that people might find more secure than the non-locking version that you show.

Tom :moses:

Yeah, Tom, that half twist make a big difference to me.

I'd be good with whatever contingency rig folks want to use, munter/mule, stone, figure eight... I wouldn't be overly psyched to dive onto a jester rig with a 8mm canyon pro rope, though, unless one side is tied off.

Cheers!