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rgold
Dec 20, 2012, 4:46 PM
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jliungman wrote: Hi! The results, in short, show that under heavy but entirely realistic loads (ff 2 with new rope and and test dummy), a new dyneema sling fails completely. This happens when the dyneema is shortened using two techniques which, at least in Scandinavia, are common and taught by instructors. Any thoughts?
The loads are heavy, that's for sure. "Entirely realistic" is questionable, and "complete failure" appears to be just plain wrong. What failed was a single strand of clove-hitched dyneema. We can probably all agree that it is a bad idea to take a statically belayed factor-2 fall on a single strand of clove-hitched dyneema.
On the other side of the coin, most people and all engineers believe that one's gear should have safety margins, which is to say that is should be capable of withstanding loads in excess, typically significantly in excess, of what might be expected in the field.
Industrial-level safety margins are not possible for climbing gear in general; they would make the gear too heavy to be practical. So climbers (or those climbers who actually think about such things) are used to operating far closer to the safety edge when climbing then they would be in their ordinary lives.
The dyneema tests continue to suggest that there is almost no safety margin, in the engineering sense, with knotted dyneema slings, meaning that knotted sling failure loads, for brand-new material, are at the edge of what could conceivably occur in certain unusual climbing situations, and this is without any allowance for the relatively rapid decline in strength, compared to nylon, of dyneema.
I doubt there will be many people who will chuck their trad draws because of this, nor should there be. As I said, for practical reasons, climbers have to accept low safety margins in their gear. Most trad gear will cannot hold the largest loads that one can expect in the field, for example.
This does not mean, internet static notwithstanding, that climbers should strive to remain as ignorant as possible about the performance of their gear under challenging conditions, or that knowledge of limitations has to be equated with fear of usage, but the internet is what it is.
Practically speaking, I'd be cautious about knotting dyneema in very high-load applications like belay anchors, especially if, say, you are rope-soloing and so employing totally static belays. Most of the time, it still seems highly unlikely to matter. However, it is also true that there are effective practices, such as tying in with the rope, with orders of magnitude higher margins of safety.
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cracklover
Dec 20, 2012, 5:24 PM
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Thanks for sharing this!
jliungman wrote: The results, in short, show that under heavy but entirely realistic loads (ff 2 with new rope and and test dummy), a new dyneema sling fails completely. This happens when the dyneema is shortened using two techniques which, at least in Scandinavia, are common and taught by instructors. Any thoughts? To me the results imply that we should avoid knotting dyneema altogether, and use this fantastic material only in full length, stitched slings (like quick draws). At least until we know more about which nylon/dyneema/widths/knots combinations work and which donīt.
My conclusions are different from yours.
I would say that we should absolutely avoid any situation in which a serious load could conceivably come onto a single strand of knotted dyneema. The first test shows one such situation. However I've never done that, and would not be likely to. So that raises the question of whether this failure mode has any bearing on my climbing?
To answer that, I will generalize the failure mode to see all the cases in which it could apply. After doing that, I conclude that to be safe, a dyneema sling should never have more than one knot/hitch put in it. Not unless it is only one part of a more complex rigging.
GO
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healyje
Dec 20, 2012, 6:43 PM
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Syd wrote: healyje wrote: More of an issue with skinny dyneema slings is keeping and using them to long. They are designed as a ultralite, short-lifespan, alpine consumable and were never intended for long term use on trad racks or sport draws. It's not just dyneema that's short lived. I was surprised reading this recently: " Testing by Todd Vogel at Blue Water Ropes showed consistent strength losses for most cords and tapes, after one or two years use the strength dropped to 60% even when there was no obvious wear. Id be replacing critical slings such as cordellettes every year or two." Also: http://www.efclimbers.net/resources/Knot-and-cord-strength.pdf
The testing here is pretty scattershot with regard to the knowing the ages of the materials under test - some they do, some they don't. The conclusion you draw is far too sweeping. It does a better job on knots than on material aging and I'd personally look elsewhere for that testing. A two year replacement cycle is not necessary on much beyond skinny dyneema - certainly not 1" nylon or 11mm dyneema/nylon. Cords are a somewhat different matter and I don't use them.
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patto
Dec 20, 2012, 7:05 PM
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bearbreeder wrote: ummmm ... that petzl diagram was very specific for descending (rappelling) on a gri gri ...
bearbreeder wrote: so you are saying that its 100% safe for one to go "hands free" on a gri gri if the cam is engaged ...
bearbreeder wrote: so for example is my climber is resting on the rope, the cam is fully engaged, i can let go of the brake hand ?????????
bearbreeder wrote: of course if you are swinging around theres absolutely no chance anything will happen at all will there now 
I am not advocating rapping or belaying like this. That is a decision only you can make yourself. But personally I am happy to rely on the grigri hands free for MY personal safety when the cam is engaged.
In fact I did so a hundred or so times three days ago as I used a gri-gri method to jug up a 50m line.  Know and understand your gear. This goes beyond simply reading the instruction manual!
Likewise, my partner spent about 40 minutes typing emails on his android tablet while belaying me the other day. He had me on a gri-gri and had a grip on the brake rope so I was not concerned.
(Aid climbing is not the fastest of sports )
(This post was edited by patto on Dec 20, 2012, 7:09 PM)
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JimTitt
Dec 20, 2012, 7:15 PM
Post #30 of 64
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cracklover wrote: Thanks for sharing this! jliungman wrote: The results, in short, show that under heavy but entirely realistic loads (ff 2 with new rope and and test dummy), a new dyneema sling fails completely. This happens when the dyneema is shortened using two techniques which, at least in Scandinavia, are common and taught by instructors. Any thoughts? To me the results imply that we should avoid knotting dyneema altogether, and use this fantastic material only in full length, stitched slings (like quick draws). At least until we know more about which nylon/dyneema/widths/knots combinations work and which donīt. My conclusions are different from yours. I would say that we should absolutely avoid any situation in which a serious load could conceivably come onto a single strand of knotted dyneema. The first test shows one such situation. However I've never done that, and would not be likely to. So that raises the question of whether this failure mode has any bearing on my climbing? To answer that, I will generalize the failure mode to see all the cases in which it could apply. After doing that, I conclude that to be safe, a dyneema sling should never have more than one knot/hitch put in it. Not unless it is only one part of a more complex rigging. GO
The University of Stuttgart did drop tests on most of the common materials clove hitched into a karabiner as part of DAV research for various cordalette/equalette systems where a single hitched strand may well ultimately be called on to take the entire load. Dyneema wasnīt the winner!
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bearbreeder
Dec 20, 2012, 8:49 PM
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patto wrote: bearbreeder wrote: ummmm ... that petzl diagram was very specific for descending (rappelling) on a gri gri ... I've never said otherwise. bearbreeder wrote: so you are saying that its 100% safe for one to go "hands free" on a gri gri if the cam is engaged ... I have made myself quite clear. bearbreeder wrote: so for example is my climber is resting on the rope, the cam is fully engaged, i can let go of the brake hand ????????? Yes. You can safely do so. bearbreeder wrote: of course if you are swinging around theres absolutely no chance anything will happen at all will there now No there isn't any chance provided the cam isn't forced open. Simply swinging around wont do this. I am not advocating rapping or belaying like this. That is a decision only you can make yourself. But personally I am happy to rely on the grigri hands free for MY personal safety when the cam is engaged. In fact I did so a hundred or so times three days ago as I used a gri-gri method to jug up a 50m line. Know and understand your gear. This goes beyond simply reading the instruction manual! Likewise, my partner spent about 40 minutes typing emails on his android tablet while belaying me the other day. He had me on a gri-gri and had a grip on the brake rope so I was not concerned. (Aid climbing is not the fastest of sports )
asked
Hi Petzl,
Ive been told that
"A loaded grigri is 100% safe to go hands free provided the cam isn't forced open."
Is this true? Can i take my brake hand off the rope when rappelling or belaying without any backup knots if the cam is fully engaged?
Thanks,
answered
Hello, sorry to say that what you have been told is absolutely wrong. In all our technical instruction we clearly say never let your brake hand go off the rope. Please consult :
http://www.petzl.com/files/all/technical-notice/Sport/D14-GRIGRI2.pdf
we are RCers, we know better than the manufacturer when something is "100% safe" ... take those brake hands off those gri gris now ya gumbays, cause we at RC say so !!!
(This post was edited by bearbreeder on Dec 20, 2012, 8:50 PM)
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patto
Dec 20, 2012, 9:35 PM
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 Oh dear.... You are a very odd character.
I wouldn't have expected any other response from Petzl.
That doesn't change the facts though!
Also this is something I have not encouraged or advocated: Can i take my brake hand off the rope when rappelling or belaying without any backup knots if the cam is fully engaged?
(This post was edited by patto on Dec 20, 2012, 9:41 PM)
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jliungman
Dec 20, 2012, 10:58 PM
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Sorry, been busy elsewhere for a day, but will try to clarify a few things that seem to be in question!
1. The person talking in the video has a stopper knot further down the rope under the grigri. It shows in sequences I have edited out. So let us focus on the relevant bits.
2. All the material (sling, rope) is new.
3. The end of the rope that is normally held by the belay device is here tied directly to the anchor. I assume that this is just a way of making the tests comparable, since having a human belayer would add randomness to the tests. In a proper standard test scenario, the rope would have been wound a couple of times around a bar to add some simulated dynamism, but would not have inlcuded a belay device. Correct me if I am wrong. Also, this test uses a dummy doll to simulate the slightly dynamic properties of a body rather than the rigid test weight used in a standard test, so it will balance out at least partially.
4. True, in the second scenario, with the double overhand, there is not complete failure. Bad wording from me in the OP. The stitching seems to be stopping the knot sliding. I would have to go back to the raw material to see if there were examples where the stitching was differently positioned. The sliding it itself would, of course, completely alter the direction and loading of a two point anchor.
5. The technique of equalizing an anchor by tying a clove hitch around a carabiner and loading only one strand of a sling is still common here in Sweden. If it is not so in other parts of the world then all is well there and we need to look at this only locally. I for one will avoid it, but itīs not something I thought of before this video.
Then, adding some of my opinion here rather than fact... The argument that other things kill climbers, or that the scenario is somehow extreme, is faulty. If you donīt plan on having ff2 falls, and always having two perfectly weighted pieces - or if you plan on getting hit in the head by a rock rather than take a whipper - then why not climb with much weaker (and lighter, and cheaper) setups? The point, as has been mentioned here, is that we want great margins of safety in our systems. And I think these clips hint that this margin of safety is reduced with Dyneema in some setups. Sure, if we add a belay device and two pieces of pro we have smaller loads. But to me the video still indicates something is wrong, since this is still a dynamic fall (as opposed to DMMs videos of competely static testing). It needs more testing, and I have asked some manufacturers about this. They have promised to look into it, but I guess they have a lot on their lists of things to check in the lab.
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healyje
Dec 20, 2012, 11:45 PM
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jliungman wrote: But to me the video still indicates something is wrong
I'm inclined to disagree. Skinny dyneema slings were developed in a deliberate alpine trade-off for weight and are not a durable good, neither do they bear knotting of any kind.
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bearbreeder
Dec 20, 2012, 11:48 PM
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jliungman wrote: The point, as has been mentioned here, is that we want great margins of safety in our systems.
well first of all, tie off a gri gri when going hands free as per the manufacturers recommendations ... that will be most beneficial to your "margin of safety" in the video ... i presume you dont go hands free with a gri gri with your clients as guides and instructor ...
second of all its all about choices ... for example there are REAL incidents with cut ropes, yet no one is suggesting we ONLY use twin ropes ...
third of all ... put a belay device in the system ... you claim that it is a "realistic" test with dummies and dynamic ropes ... but when was the last time you belayed without a device or munter or hip belay in the system???
im not saying the results arent interesting or concerning to some degree ... if you claim to be testing realistic conditions, then do it with as close to a real life scenario as possible ...
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patto
Dec 21, 2012, 1:19 AM
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bearbreeder wrote: well first of all, tie off a gri gri when going hands free as per the manufacturers recommendations ... that will be most beneficial to your "margin of safety" in the video ...
No matter how many times you repeat it it wont be true bearbreeder.
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gunkiemike
Dec 21, 2012, 2:42 AM
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Syd wrote: It's not just dyneema that's short lived. I was surprised reading this recently: " Testing by Todd Vogel at Blue Water Ropes showed consistent strength losses for most cords and tapes, after one or two years use the strength dropped to 60% even when there was no obvious wear. Id be replacing critical slings such as cordellettes every year or two."
Well, that's interesting. I just had 3 old (16-18 yr old) Dyneema slings pull tested. All were lightly used. They broke at:
4600 lb
4800 lb
and stayed intact to 5000 lb.
And two of them were BW brand.
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Syd
Dec 21, 2012, 5:27 AM
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healyje wrote: A two year replacement cycle is not necessary on much beyond skinny dyneema - certainly not 1" nylon or 11mm dyneema/nylon.
I use 18mm nylon. Mine were all well used, 5 to 7 years old and looking rather furry, so I replaced them all after reading the article.
Accidents are usually a combination of factors, and I'd rather remove any possible factors for a measly few dollars than put my life at risk. Todd Skinner is a classic example of someone who pushed his gear rather than spend a dollar.
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jliungman
Dec 21, 2012, 7:50 PM
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As for whether or not a single strand should be loaded I have added a sketch of a typical (for where Iīm from) anchor setup. A clove hitch on each carabiner and slack between the two. One strand from each carabiner runs to the master point (fig 8). It can be used to get some extra length out of your single sling compared to pulling four strands down to the master point.
This is not the exact same setup as the video, but the doubled version. Still, only a single strand from each point. If the clove hitches were to slip, you would at the least get a change in load direction on the anchors. I say this just to explain why the first setup was tested.
Iīm by no means campaigning against dyneema and I am a bit surprised at the emotional reactions. I do think it is relevant to show that there are a number of situations where dyneema cannot be used like nylon. And it IS being used like nylon (although many here on the forum seem to be well aware of the problems).
One recent example is a friend who was out ice-clogging, using a baudrier parisienne to keep his clogging device in a good position (a 120 cm sling around the shoulders). When the dyneema was wet and he weighted the knot, it slipped and compressed his torso, and would have killed him had he not had the presence of mind to transfer weight to his backup rope in time. There are specific details involved, but again, an experienced climber used dyneema like he would use nylon - and it did not work.
Dyneema has one significant advantage - low weight. But my impression is that when improperly used this advantage vanishes - nylon is stronger per weight unit as soon as you start factoring in dynamics and knots. This means that unless you want to bring both types on a climb - which would negate the weight reduction you wanted when you bought dyneema in the first place - then you might as well stick to a couple of nylon slings. Theyīll get you through most situation and you donīt need to worry about all the scenarios where it might slip or break. 100% of my slings are still dyneema, but Iīm beginning to wonder why? Maybe because thatīs all they had in the store?
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rgold
Dec 21, 2012, 9:04 PM
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The two-anchor clove-hitched set-up you pictured in common throughout Europe, less so in the U.S, where much longer slings (cordelettes) are carried and everything is anchored with a single knot at the so-called "power point."
Personally, I typically use both nylon and dyneema slings. My trad draws are all made up with thin dyneema, but I also carry a few over-the-shoulder slings that are nylon. I don't knot the dyneema, and in any case I rarely use anything but the climbing rope itself for anchoring, but that's just me.
By the way, there are a number of hybrid dyneema/nylon slings available. I don't know if he's paying any attention to this thread, but I think Mal Daly has done essentially the same test as the one here with such materials and found the clove-hitched sling to be stronger than some of the carabiners they were using.
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redlude97
Dec 21, 2012, 11:28 PM
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rgold wrote: The two-anchor clove-hitched set-up you pictured in common throughout Europe, less so in the U.S, where much longer slings (cordelettes) are carried and everything is anchored with a single knot at the so-called "power point." Personally, I typically use both nylon and dyneema slings. My trad draws are all made up with thin dyneema, but I also carry a few over-the-shoulder slings that are nylon. I don't knot the dyneema, and in any case I rarely use anything but the climbing rope itself for anchoring, but that's just me. By the way, there are a number of hybrid dyneema/nylon slings available. I don't know if he's paying any attention to this thread, but I think Mal Daly has done essentially the same test as the one here with such materials and found the clove-hitched sling to be stronger than some of the carabiners they were using.
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USnavy
Dec 22, 2012, 9:03 AM
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bearbreeder wrote: patto wrote: bearbreeder wrote: ummmm ... that petzl diagram was very specific for descending (rappelling) on a gri gri ... I've never said otherwise. bearbreeder wrote: so you are saying that its 100% safe for one to go "hands free" on a gri gri if the cam is engaged ... I have made myself quite clear. bearbreeder wrote: so for example is my climber is resting on the rope, the cam is fully engaged, i can let go of the brake hand ????????? Yes. You can safely do so. bearbreeder wrote: of course if you are swinging around theres absolutely no chance anything will happen at all will there now No there isn't any chance provided the cam isn't forced open. Simply swinging around wont do this. I am not advocating rapping or belaying like this. That is a decision only you can make yourself. But personally I am happy to rely on the grigri hands free for MY personal safety when the cam is engaged. In fact I did so a hundred or so times three days ago as I used a gri-gri method to jug up a 50m line. Know and understand your gear. This goes beyond simply reading the instruction manual! Likewise, my partner spent about 40 minutes typing emails on his android tablet while belaying me the other day. He had me on a gri-gri and had a grip on the brake rope so I was not concerned. (Aid climbing is not the fastest of sports ) asked
Hi Petzl,
Ive been told that
"A loaded grigri is 100% safe to go hands free provided the cam isn't forced open."
Is this true? Can i take my brake hand off the rope when rappelling or belaying without any backup knots if the cam is fully engaged?
Thanks, answered
Hello, sorry to say that what you have been told is absolutely wrong. In all our technical instruction we clearly say never let your brake hand go off the rope. Please consult :
http://www.petzl.com/files/all/technical-notice/Sport/D14-GRIGRI2.pdf we are RCers, we know better than the manufacturer when something is "100% safe" ... take those brake hands off those gri gris now ya gumbays, cause we at RC say so !!!
(This post was edited by USnavy on Dec 22, 2012, 9:07 AM)
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USnavy
Dec 22, 2012, 9:12 AM
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redlude97 wrote: rgold wrote: The two-anchor clove-hitched set-up you pictured in common throughout Europe, less so in the U.S, where much longer slings (cordelettes) are carried and everything is anchored with a single knot at the so-called "power point." Personally, I typically use both nylon and dyneema slings. My trad draws are all made up with thin dyneema, but I also carry a few over-the-shoulder slings that are nylon. I don't knot the dyneema, and in any case I rarely use anything but the climbing rope itself for anchoring, but that's just me. By the way, there are a number of hybrid dyneema/nylon slings available. I don't know if he's paying any attention to this thread, but I think Mal Daly has done essentially the same test as the one here with such materials and found the clove-hitched sling to be stronger than some of the carabiners they were using.Not clear exactly what you are saying, but all "dyneema" slings are hybrids of dyneema and nylon. Its easy to tell because dyneema doesn't hold color.
(This post was edited by USnavy on Dec 22, 2012, 9:13 AM)
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jliungman
Dec 22, 2012, 12:04 PM
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rgold wrote: The two-anchor clove-hitched set-up you pictured in common throughout Europe, less so in the U.S, where much longer slings (cordelettes) are carried and everything is anchored with a single knot at the so-called "power point." Personally, I typically use both nylon and dyneema slings. My trad draws are all made up with thin dyneema, but I also carry a few over-the-shoulder slings that are nylon. I don't knot the dyneema, and in any case I rarely use anything but the climbing rope itself for anchoring, but that's just me. By the way, there are a number of hybrid dyneema/nylon slings available. I don't know if he's paying any attention to this thread, but I think Mal Daly has done essentially the same test as the one here with such materials and found the clove-hitched sling to be stronger than some of the carabiners they were using.
You have some good points, rgold. The proportion of nylon vs dyneema would be an obvious starting point for some serious tests. The sling in the video was a Mammut, as far as I know. What model, I donīt know.
Also, I agree that a mix of slings may be the preferable approach to a multi-pitch climber, specifically carrying a 120-240 nylon sling for the multi-point anchor. In most situations itīs unnecessary to knot the sling in the manners shown in the video (and personally I never liked it anyway). But I find that reality does not always permit the school-book anchor setups, and we end up having to shorten some sling or strand, especially on poor pro - when we might add an extra point as an afterthought. I mostly donīt like involving my rope in the anchor unless the pro is within reach (in case I need to retreat quickly).
Anyway, thanks for the input. Iīll get back if I get the guys behind the testing to finally summarize their results into something more solid, or if one of the manufacturers decide to put their minds to it.
Cheers!
John
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jliungman
Dec 22, 2012, 12:06 PM
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cracklover wrote: My conclusions are different from yours. I would say that we should absolutely avoid any situation in which a serious load could conceivably come onto a single strand of knotted dyneema. The first test shows one such situation. However I've never done that, and would not be likely to. So that raises the question of whether this failure mode has any bearing on my climbing? To answer that, I will generalize the failure mode to see all the cases in which it could apply. After doing that, I conclude that to be safe, a dyneema sling should never have more than one knot/hitch put in it. Not unless it is only one part of a more complex rigging. GO
Good points. I think we draw similar conclusions!
John
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bearbreeder
Dec 22, 2012, 12:16 PM
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USnavy wrote: First of all, the guy you emailed was not "Petzl," but rather likely some sales rep who could very well know less about climbing than many of the senior members of this forum. If the guy is actually a solid climber, he knows that statement was bullshit but he had to say it for liability reasons. Second, the GriGri is one of the most commonly used devices in slacklining. We use it to serve as a mechanical brake to stop the pulley system from despooling. When using the GriGri as a brake in long slacklines, the force subjected to the GriGri is far greater than what is normally seen in the climbing world, and the device is always operated "hands free" with nothing holding the rope. To date I have never heard of a GriGri randomly slipping without being overloaded. My GriGri has likely had over 100 hours of "hands free" time on it holding my slackline. I normally tension my longline in excess of 2,000 lbf which means the GriGri has to hold in excess of 400 lbf. at times.
well first of all you do know when swinging around, leaning over with a measuring tape, wearing loose clothes ... things can catch and get bumped ... now you may say this is very unlikely, but then again no more so than a true factor 2 fall on a dyneema sling with a funny knot and no belay device ...
second of all ill still take PETZLs word over yours ... since you believe its perfectly fine to take the hand right off the brake when rapping or belaying by implication once its loaded
that should be the "official" RC line ... just take your hands off babiii
it takes 10 seconds to tie a quick slip knot ...
(This post was edited by bearbreeder on Dec 22, 2012, 12:17 PM)
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patto
Dec 22, 2012, 12:24 PM
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Despite all the words you haven't yet even explained how the statement is incorrect. A loaded grigri is 100% safe to go hands free provided the cam isn't forced open.
Know and understand you equipment. It seems that you don't. I suppose you wouldn't trust a Reverso in autoblock in hands free either. 
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