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psprings
Jun 11, 2010, 6:23 PM
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This is a very insightful study done by dmm which looks at the forces put on runners when falling onto them with slack in the system. I think it applies to people that have slack in their system at a belay, and also if you fall onto a spectra daisy chain if aiding. Check it out, it's pretty fasinating: Main page: http://www.dmmclimbing.com/...nid=293&ngroup=1 Direct link to video: http://www.dmmclimbing.com/video.asp?id=5 ps- if any moderators have a better forum to put this in, feel free to move it.
(This post was edited by psprings on Jun 11, 2010, 6:24 PM)
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majid_sabet
Jun 11, 2010, 6:39 PM
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psprings wrote: This is a very insightful study done by dmm which looks at the forces put on runners when falling onto them with slack in the system. I think it applies to people that have slack in their system at a belay, and also if you fall onto a spectra daisy chain if aiding. Check it out, it's pretty fasinating: Main page: http://www.dmmclimbing.com/...nid=293&ngroup=1 Direct link to video: http://www.dmmclimbing.com/video.asp?id=5 ps- if any moderators have a better forum to put this in, feel free to move it. very interesting and scary. Modz, please send this to lab
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caughtinside
Jun 11, 2010, 6:48 PM
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Since I started hearing about this stuff a couple seasons ago, I went back to using more nylon runners. Probably 50/50 nylon and dyneema now. nice to have a few of the skinnies on hand, but the nylon isn't just 100% static like the skinny stuff.
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shoo
Jun 11, 2010, 7:37 PM
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caughtinside wrote: Since I started hearing about this stuff a couple seasons ago, I went back to using more nylon runners. Probably 50/50 nylon and dyneema now. nice to have a few of the skinnies on hand, but the nylon isn't just 100% static like the skinny stuff. 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. IMO, the real negatives of skinny dyneema slings are as follows: 1) Cost. They're pretty damn pricey compared to nylon 2) Durability. Gotta retire them faster, and cost more too replace, too. 3) Difficult to use as a friction hitch. They're pretty slippery. I certainly wouldn't use one as the friction hitch for holding me personally, though if I need to rig it for my feet, whatever. 4) Difficult to tie to things. Slippery, skinny enough to cut through other stuff. That said, I use skinny slings exclusively nowadays. The weight and cluster savings is pretty fantastic.
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tedman
Jun 11, 2010, 7:50 PM
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kinda sobering to see that 22kn dynema snap... 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...
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caughtinside
Jun 11, 2010, 8:13 PM
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shoo wrote: caughtinside wrote: Since I started hearing about this stuff a couple seasons ago, I went back to using more nylon runners. Probably 50/50 nylon and dyneema now. nice to have a few of the skinnies on hand, but the nylon isn't just 100% static like the skinny stuff. 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. IMO, the real negatives of skinny dyneema slings are as follows: 1) Cost. They're pretty damn pricey compared to nylon 2) Durability. Gotta retire them faster, and cost more too replace, too. 3) Difficult to use as a friction hitch. They're pretty slippery. I certainly wouldn't use one as the friction hitch for holding me personally, though if I need to rig it for my feet, whatever. 4) Difficult to tie to things. Slippery, skinny enough to cut through other stuff. That said, I use skinny slings exclusively nowadays. The weight and cluster savings is pretty fantastic. I agree with you that the test used isn't a very accurate reproduction of real life climbing scenarios, but useful for learning about the properties of the two materials. I also agree that the dyneema runners are twice as expensive and wear out twice as fast (which makes them 4x as much?) But i disagree that the weight savings is noticeable, and the bulk issue I haven't really found to be a problem using 5 nylon slings and 5 dyneema ones. If you're happy going all dyneema that's great, I did that for several years. But for me, I like having an extra dynamic element in the system rather than something 100% static. An added benefit is that if I need to leave sling material behind at anchors it's cheap, and I can cut the nylon and tie it.
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acorneau
Jun 11, 2010, 8:23 PM
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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. From the DMM web page...
In reply to: After watching the video I'm sure you'll agree that dogging a move on a sport climb while clipped to any sling is a dangerous idea and that having any slack in a belay system is best avoided - you wouldn’t want to fall off a ledge clipped into a slack sling. Clearly, taking advantage of the shock-absorbing capability of the rope by using it to tie directly into anchors as opposed to using a sling, will reduce the chances of dramatically shock-loading the anchors. If you do use slings then ensuring there is no slack in the system is paramount.
(This post was edited by acorneau on Jun 11, 2010, 8:32 PM)
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maldaly
Jun 11, 2010, 8:24 PM
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I want to know where that guy gets his hair done!
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shoo
Jun 11, 2010, 8:29 PM
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acorneau wrote: 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. From the DMM web page... In reply to: After watching the video I'm sure you'll agree that dogging a move on a sport climb while clipped to any sling is a dangerous idea and that having any slack in a belay system is best avoided - you wouldn’t want to fall off a ledge clipped into a slack sling. They're not talking about a sling on a piece of pro while using the rope, but connecting yourself directly to pro/bolts/anchors with a sling. I know. I was explaining why this test isn't relevant to me, since using a runner in this manner, nylon or dyneema, is generally a bad idea, period. Obviously this shows that it's an even worse idea with dyneema, but that's irrelevant if you don't use them like this.
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shoo
Jun 11, 2010, 8:30 PM
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caughtinside wrote: I agree with you that the test used isn't a very accurate reproduction of real life climbing scenarios, but useful for learning about the properties of the two materials. I also agree that the dyneema runners are twice as expensive and wear out twice as fast (which makes them 4x as much?) But i disagree that the weight savings is noticeable, and the bulk issue I haven't really found to be a problem using 5 nylon slings and 5 dyneema ones. If you're happy going all dyneema that's great, I did that for several years. But for me, I like having an extra dynamic element in the system rather than something 100% static. An added benefit is that if I need to leave sling material behind at anchors it's cheap, and I can cut the nylon and tie it. It's more of a bulk thing than anything. I guess I associate bulky and heavy. 60cm BD nylon sling is 36grams 60cm Mammut contact sling is 15 grams Over 10 trad draws, that's a savings of about 7 oz, so yeah, you're right no big deal. In any case, the couple of nylon slings I used to have have been lost or bailed off of long ago.
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redlude97
Jun 11, 2010, 8:37 PM
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yep, bulk is the main issue. A tripled nylon runner is huge compared to a tripled dyneema runner, especially the mammuts.
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caughtinside
Jun 11, 2010, 8:37 PM
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Well in that case, it's always worth having one tied nylon runner. They cost $1.50 and are great for bailing instead of leaving those $10 mammuts.
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psprings
Jun 11, 2010, 8:47 PM
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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. 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. You're right, this isn't about how they work in a lead fall with a dynamic rope involved.
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shoo
Jun 11, 2010, 8:53 PM
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psprings wrote: 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. 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. You're right, this isn't about how they work in a lead fall with a dynamic rope involved. I really have no clue what you just tried to say above. In any case, the point I'm making is that you don't take falls while attached to an anchor directly with a sling. You just don't. And since you don't, this test isn't relevant.
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psprings
Jun 11, 2010, 8:58 PM
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You don't know anyone that has ever attached to the main anchor via a sling? And you've never seen slack in such a system? It's pretty simple.
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shoo
Jun 11, 2010, 9:01 PM
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psprings wrote: You don't know anyone that has ever attached to the main anchor via a sling? And you've never seen slack in such a system? It's pretty simple. 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. Edit: just thought of a scenario, which is so profoundly stupid as to be, again, totally irrelevant. Factor 2 onto the anchor, with the belayer attached to the anchor via a sling, while the belayer is allowing significant slack in the sling between him/herself and the anchor. This may be what you were trying to say earlier. In this case, the rope will not mitigate the force caused by the belayer falling. Again, this is stupid because the belayer should not have had slack between him/herself and the anchor. That is the problem, not the dyneema.
(This post was edited by shoo on Jun 11, 2010, 9:11 PM)
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psprings
Jun 11, 2010, 9:08 PM
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Of course it will be mitigated by the rope, the point is that when you have slack in your system, shockloading is bad. Suppose the rope reduces the forces to 10Kn instead of the 20Kn seen in the video. That still leaves you with 10Kns of force slamming that slack that you have in your system. It's not a big leap to see how this applies to real world belay set ups. Yes, your right that it's a test and doesn't perfectly describe things, but it does a great job at helping us think about our belay system and how high the forces can be on things... at least some of us.
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shoo
Jun 11, 2010, 9:15 PM
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psprings wrote: Yes, your right that it's a test and doesn't perfectly describe things, but it does a great job at helping us think about our belay system and how high the forces can be on things... at least some of us. If it helped you to understand not to use a runner as a personal anchor system (and if you do use it, don't have any slack in it), then i suppose the test did some good. It's a dangerous practice with ANY sling material. However, this was already pretty well known, at least where I come from.
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jt512
Jun 11, 2010, 9:28 PM
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tedman wrote: The fleshy human body is not made of steel. Speak for yourself. Jay
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psprings
Jun 11, 2010, 9:33 PM
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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.
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shoo
Jun 11, 2010, 10:02 PM
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Nope, didn't need to. As far as I know, it has never been accepted practice to allow slack between yourself and your anchor if you are using a sling as a connection to an anchor. A fall on a runner directly attached to an anchor massively increases the force on the gear and the person. This has been known for a long, long time. With regards to the PAS, they are hanging in them. As in no slack in the system. No fall possible if there isn't any slack, now is there?
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cracklover
Jun 11, 2010, 10:32 PM
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shoo wrote: psprings wrote: You don't know anyone that has ever attached to the main anchor via a sling? And you've never seen slack in such a system? It's pretty simple. 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. 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
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shoo
Jun 11, 2010, 10:49 PM
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Neither of these is a lead fall.
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psprings
Jun 11, 2010, 10:57 PM
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shoo wrote: Neither of these is a lead fall. But both of them fit the test model; hence how it applies.
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