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caughtinside


Jun 11, 2010, 4:50 PM
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Re: [shoo] Forces when falling onto dyneema/spectra runners [In reply to]
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shoo wrote:
Neither of these is a lead fall.

but this is a PTFTW.


patto


Jun 11, 2010, 5:37 PM
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Re: [psprings] Forces when falling onto dyneema/spectra runners [In reply to]
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psprings wrote:
Naw, now you're just being a jerk. I hardly believe that you knew that dyneema runners could break from that minimal of a load.

How many people are out there that anchor into chains with a Metolius PAS? Come on dude, you need a reality check.

Why are you doubting that he knew dyneema runners could break like that? This has been fairly common knowledge for years. There have been numerous tests by numerous companies. It isn't that complicated and it isn't that surprising.


adatesman


Jun 11, 2010, 5:41 PM
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patto


Jun 11, 2010, 5:54 PM
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Re: [adatesman] Forces when falling onto dyneema/spectra runners [In reply to]
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adatesman wrote:
Judging from the number of threads here on RC about using slings as personal anchors, I'd have to side with psprings and say that it's apparently not common knowledge. Seems to me this topic comes up once or twice a year.

True, true. The evidence speaks for itself. :-)
('Common knowledge' is all dependent on the group you choose.)

Psprings was calling someone a jerk because he considered that this was new knowledge.


jt512


Jun 11, 2010, 8:27 PM
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Re: [shoo] Forces when falling onto dyneema/spectra runners [In reply to]
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shoo wrote:
Neither of these is a lead fall.

That shouldn't be too surprising, since no one leads while tied to the anchor by a sling.

Jay


gerasal


Jun 11, 2010, 9:58 PM
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Re: [psprings] Forces when falling onto dyneema/spectra runners [In reply to]
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Wow, it's amazing to me how threads on this site get completely sidetracked, and how much havoc a little test data causes.

Two pieces of information can be drawn from this data:
1) Peak forces at the fixed point (anchor, bolt, whatever) due to a fall are higher when the load is transfered through dyneema than through nylon, both being of the same load rating.
2) A dyneema sling is more likely to fail at a lower impact force than an equivalent load rated nylon sling.

These are comparative results, under the same conditions. They are valid regardless of the type of fall. If the fall can generate 11KN at the fixed end, a knotted dyneema sling is more likely to fail than an equivalent knotted nylon sling. Weather a TR, lead, or anchor fall generates that amount of load is a different question.

However, anybody who's worked on a test lab or knows some statistics will understand that one or two samples are not statistically significant. So, any test conclusion drawn based on one or two samples is questionable. A significant test result would require performing the test on a statistically significant number of samples, and reporting mean force at the anchor (or mean failure force in case of failure) and standard deviation. And to add to the equation you would need samples from multiple manufacturers, since manufacturers will have different safety margins on their ratings. A sling rated at 16KN only means the manufacturer assures that it will not fail below 16KN under some test conditions. That might mean that the lower end of the manufacturing spectrum fails at 18KN, or it might mean it fails at 20KN. So, a 16KN dyneema from one manufacturer might come out better than a 16KN nylon from a different manufacturer.

But, whatever... go on flaming... it is entertaining...


jt512


Jun 11, 2010, 10:30 PM
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Re: [gerasal] Forces when falling onto dyneema/spectra runners [In reply to]
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gerasal wrote:
Wow, it's amazing to me how threads on this site get completely sidetracked, and how much havoc a little test data causes.

However, anybody who's worked on a test lab or knows some statistics will understand that one or two samples are not statistically significant.

If your null hypothesis is that the probability of sling failure under the test conditions is close to zero, and you test one or two samples, and the proportion of failures is 0.5 or 1, then your results are statistically significant, even though your sample size is only 1 or 2.

In reply to:
But, whatever... go on flaming... it is entertaining...

Almost as entertaining as reading a statistics flame that clearly shows that the writer doesn't understand statistical inference. So, yeah, please go on. This will be fun, indeed.

Jay


(This post was edited by jt512 on Jun 12, 2010, 7:47 AM)


bill413


Jun 14, 2010, 10:07 AM
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Re: [jt512] Forces when falling onto dyneema/spectra runners [In reply to]
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jt512 wrote:
shoo wrote:
Neither of these is a lead fall.

That shouldn't be too surprising, since no one leads while tied to the anchor by a sling.

Jay

Blush


shoo


Jun 14, 2010, 10:16 AM
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Re: [bill413] Forces when falling onto dyneema/spectra runners [In reply to]
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bill413 wrote:
jt512 wrote:
shoo wrote:
Neither of these is a lead fall.

That shouldn't be too surprising, since no one leads while tied to the anchor by a sling.

Jay

Blush

That's exactly what I was saying. Cracklovers comment was not relevant to my original statement that lead falling has nothing to do with this conversation. Full circle.

There is a reason this is a thread, not a tweet.


qtm


Jun 14, 2010, 12:18 PM
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Re: [shoo] Forces when falling onto dyneema/spectra runners [In reply to]
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shoo wrote:
bill413 wrote:
jt512 wrote:
shoo wrote:
Neither of these is a lead fall.

That shouldn't be too surprising, since no one leads while tied to the anchor by a sling.

Jay

Blush

That's exactly what I was saying. Cracklovers comment was not relevant to my original statement that lead falling has nothing to do with this conversation. Full circle.


Three Doves GT anchor. Leader clips with a 2' runner, then ties in with the rope as a backup. Belays partner up. Flip the rope, leader unties rope but forgets to unclip. Steps up and walks up behind tree. Runner follows around tree, then stops the leader. Who stumbles and falls 6' on a 2' runner.

Yes, the rope will catch him when the runner breaks. But by that time the leader and the anchor have already absorbed the force.

Sure, it comes under the "horribly wrong" category, but I'm sure people forget to unclip all the time. They're just lucky not to fall at that point.


acorneau


Jun 14, 2010, 1:17 PM
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Re: [qtm] Forces when falling onto dyneema/spectra runners [In reply to]
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qtm wrote:
Who stumbles and falls 6' on a 2' runner.


How's that again?!?


qtm


Jun 14, 2010, 1:39 PM
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Re: [acorneau] Forces when falling onto dyneema/spectra runners [In reply to]
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acorneau wrote:
qtm wrote:
Who stumbles and falls 6' on a 2' runner.


How's that again?!?

Walk up behind the tree and the runner will ride up the webbing around the tree, adding a couple of feet to the fall distance but not the amount of "rope" out. Because you're scrambling up, it might not quite be an FF2 if you stumble back down before going over. But if you pitch cleanly back, could be more than FF2.

There are a number of these anchors. Sleepwalk is another where you could take a > FF2 fall if you forget to unclip and climb past the anchor. But not many bother to go past the tree.

Edited: grammar


(This post was edited by qtm on Jun 14, 2010, 1:43 PM)


tradmanclimbs


Jun 14, 2010, 1:46 PM
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Re: [acorneau] Forces when falling onto dyneema/spectra runners [In reply to]
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You would be supprised how often the comfortable stance on a multi pitch climb is not directly under the anchors for whatever reason. you then end up standing in a spot usualy off to the side and sometimes above where you should be. I quite often have to tell partners where to stand at a stance. Hey. I know its more comfortable up there but if you slip you will shock load the anchor so please come down here.. daisys, PAS and slings that you use to clip into the anchor with should not be Dynema or specrta. Nylon is the best way to go. Slings that you intend to knott or girth hitch should also be nylon. pretty simple stuff actually.


shoo


Jun 14, 2010, 2:27 PM
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Re: [tradmanclimbs] Forces when falling onto dyneema/spectra runners [In reply to]
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tradmanclimbs wrote:
Nylon is the best way to go.

If by nylon, you mean your rope and a clove-hitch, then yes.





And for all of you who think it's scary that the slings broke, don't worry; you're going to break way before they do.


tradmanclimbs


Jun 14, 2010, 2:33 PM
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Re: [shoo] Forces when falling onto dyneema/spectra runners [In reply to]
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Shoo, cloveing in with the rope is great when climbing but a bit of a hassel when rapellingWink


caughtinside


Jun 14, 2010, 3:39 PM
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Re: [shoo] Forces when falling onto dyneema/spectra runners [In reply to]
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shoo wrote:
tradmanclimbs wrote:
Nylon is the best way to go.

If by nylon, you mean your rope and a clove-hitch, then yes.





And for all of you who think it's scary that the slings broke, don't worry; you're going to break way before they do.

I wouldn't say it's scary, but I would say it's eye opening, the difference in the force generated by the fall onto the spectra runner, and the fall onto the nylon runner. The forces generated by the spectra are nearly double in several cases on that chart.


jefffski


Jun 17, 2010, 10:38 AM
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Re: [cracklover] Forces when falling onto dyneema/spectra runners [In reply to]
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cracklover wrote:


Scenario 1: multi-pitch rappel. You rap down to the next bolted anchor and clip into it with a two foot sling while standing on a small ledge. You get off rappel and then stupidly slip off the small ledge. Knot in your spectra sling, or no knot, but you're above the anchor? Buh-bye.

Scenario 2: You're leading, and finish your pitch at a bolted anchor. Standing on a small ledge, you clip into the first bolt. You call down "off belay". You slip. See above.

GO

Not a scenario--this happened to me:
Standing on a ledge after rapping. Anchored to two pins with slings. My partner was rapping down and knocked down some very large rocks, coming right at me. I had nowhere to hide, so I faced the onslaught face on and took a direct hit to my arm. Consequently, i was knocked off the ledge and found myself hanging in mid air, held by the slings.

I do not know how much slack I had in the system, but there was likely some.

In short, the scenario tested by DMM could, and in my case, did happen.


psprings


Jun 17, 2010, 11:16 AM
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Re: [shoo] Forces when falling onto dyneema/spectra runners [In reply to]
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shoo wrote:
That's exactly what I was saying. Cracklovers comment was not relevant to my original statement that lead falling has nothing to do with this conversation. Full circle.

There is a reason this is a thread, not a tweet.
shoo wrote:
Meh. Kinda irrelevant to me. These kinds of tests are done by dropping something on a sling attached to a static anchor. However, this isn't really how they are used. If you're taking a fall on an anchor attached directly by a dyneema sling, you did something horribly wrong.

These are runners. There is a key factor that's missing from these kinds of tests: the rope. That's what reduces the peak forces during the fall. If used appropriately, the additional stretch from the runner is negligible compared to that of the rope and belay system.
This is your first post, Shoo. Up to this point no one was talking about these being used as "runners" and failing like in the DMM video. You're the one who brought up the rope being part of the system via a belay.

Like you say in your first (not second) paragraph, something would be horribly wrong... and it does/can happen. That's all this is pointing out, and letting you know how bad it can be when it does.


(This post was edited by psprings on Jun 17, 2010, 11:18 AM)


shoo


Jun 17, 2010, 11:45 AM
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Re: [psprings] Forces when falling onto dyneema/spectra runners [In reply to]
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Except that's not the actual run of things that happened. Here, let me summarize the full order of events, in actual order, and not just what you feel like posting, such that you may understand them.

psprings wrote:
The point of the study was looking at using them by having them to attach the climber to an anchor (think: multipitch, you are using these to keep you tied in), but that there could be let's say 12" of slack floating around. Then suppose your climber takes a fall and pulls that slack out of the system; this is supposed to give you an idea of how this could affect your tie-in.

psprings brings some odd lead fall situation into the conversation

shoo wrote:
Yes, I have. If the leader falls, said person is pulled up. Force is mitigated via the rope, the belayer being pulled upward against gravity, and any additional friction in the system.

If, in the worst case scenario, the climber falls factor 2 style onto the anchor, peak force is reduced through the rope, the belay device, and the belayer's belay loop.

In other words, there is NO SCENARIO in which a leader fall will result in static load onto the anchor.

Shoo says that a lead fall does not result in static load onto the anchor.

cracklover wrote:
Huh?

Not difficult to imagine at all!

Scenario 1: multi-pitch rappel. You rap down to the next bolted anchor and clip into it with a two foot sling while standing on a small ledge. You get off rappel and then stupidly slip off the small ledge. Knot in your spectra sling, or no knot, but you're above the anchor? Buh-bye.

Scenario 2: You're leading, and finish your pitch at a bolted anchor. Standing on a small ledge, you clip into the first bolt. You call down "off belay". You slip. See above.

GO

Cracklover disputes above statement, except doesn't realize that I never said anything about a static load not being possible; rather, I said that lead falls will not produce static load.

shoo wrote:
Neither of these is a lead fall.

I dispute the above.




This is effing simple people. All I said was that lead falls don't produce static load onto the anchor, except in the one scenario I outlined.


chadnsc


Jun 21, 2010, 12:24 PM
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Re: [jt512] Forces when falling onto dyneema/spectra runners [In reply to]
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jt512 wrote:
shoo wrote:
Neither of these is a lead fall.

That shouldn't be too surprising, since no one leads while tied to the anchor by a sling.

Jay

They don't? Damn I've been doing it wrong all this time. Tongue


psprings


Jun 21, 2010, 12:45 PM
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Re: [shoo] Forces when falling onto dyneema/spectra runners [In reply to]
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shoo wrote:
Except that's not the actual run of things that happened. Here, let me summarize the full order of events, in actual order, and not just what you feel like posting, such that you may understand them.

Naw, again, you are quoting the post I made after your jump to it not applying to the rope in the situation. I simply responded with the following post that you could even see some effect on shockloading the system if there is slack in it.

Out of order to justify your argument that it doesn't apply.


snoboy


Jun 23, 2010, 9:43 PM
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Re: [tedman] Forces when falling onto dyneema/spectra runners [In reply to]
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tedman wrote:
on the flip side, I dont think its entirely fair to say that the 70kg weight is the same as a tied in climber. The fleshy human body is not made of steel. Not that I have any data, but seems like it would change the impulse of the system greatly. You've also got the harness to consider and any elasticity it brings to the table. not saying the results are BAD, just not quite apples to apples...

Might want to read myth #6 on this page: http://www.geir.com/mythbuster.html


tomcat


Jun 24, 2010, 2:38 PM
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Partner robdotcalm


Jun 24, 2010, 3:12 PM
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tomcat wrote:
This first came up when John Sherman snapped a Dyneema runner that was part of a rappel anchor a couple years ago,while rapping a static line with a gri-gri I believe.Luckily it was backed up.
slipping starting at 900 pounds when they test that scenario.

Mammut's testing gave a cut over a sharp edge as the most probable reason for the sling failing. Black Diamond also said that the break was so clean (not frayed or melted strands) that a cut of some sort was the proximal cause. Pay attention to sharp edges. Pressing against a rope or sling they present far more danger than the loss of strength from knots (and I'm not advocating thoughtless knotting).

http://news.climbing.de/...n-equipment-failure/

http://www.alpinist.com/...-broken-sling-report

Cheers,
Rob.calm


tomcat


Jun 24, 2010, 4:02 PM
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