THAT DMM climbing video: the myths and misinterpretation, many years on! Knots in Dyneema slings.
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- čas přidán 21. 08. 2024
- THAT DMM video: • How to Break Nylon and...
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The biggest advantage of the Petzl Connect Adjust is not that it uses a stretchy rope instead of a static piece of Dynema. The advantage is that you can easily adjust its length so that there never is any slack.
They’re great bits of kit 💪
Not sure if you have seen the how not 2 video, but if the connect adjust is not at the maximum length you actually "only" get roughly 5kN of breaking force.
It is obviously still a bad idea to have a fall factor 2 fall on your anchor, but it seems like it's actually kind of safe with a device similar to the connect adjust. (They are a bit dynamic and the connection thingy slips at 5kN)
@@audiojck1 I have seen the video and they are by far superior to attaching yourself with a static sling. However, the manual on the Petzl website defines climbing above the anchor as out of spec. The How Not 2 videos show that a fall factor 2 fall could be survivable in many cases, though. You can easily take out any slack while you‘re below the anchor so there should be hardly any fall at all. This is what I meant with my comment.
Yeah. It's obviously never a great idea to have a fall factor 2 and I will still try to stay tight on a connect adjust, but sometimes there are situations where you are moving around on an anchor and having the added safety is pretty great, I think.
The petzl connect adjust will also slip a bit which makes the the force even lower. HN2 did a recent video on that.
Yeah, good point :)
Ryan (HowNot2) did tests on 7 year old Dyneema slings which startet at like 26 kN breaking strength and went down to around 11 kN over those 7 years. In the same video, an overhand knot reduced the breaking strength of another (new) Dyneema sling by as much as 2/3. Worst case, you have around 4 kN breaking strength with your knot (instead of perfectly safe 11 kN) - you can definitely reach those forces with just a little slack in your sling and a static fall.
I assume those 7 year old slings were either v worn or had been in UV?
I put knots in dynema slings ~9 times just today alone (did some cheeky multi-pitching after work). It's not a thing we worry about in the US. Me and my partner are never taking factor 1s, let alone factor 2s!, on anchors.
After work climbing is the best 💪
FF1 or 2 onto a lanyard of any sort is so scary! Context is everything. Always stay tight
Oh for sure!
Excellent: good points, all well presented and explained. Thank-you.
My pleasure!
FF is meaningless on non-dynamic slings. Fall distance is what matters. Falling 120cm on a 120cm sling (FF1) is better than a 240cm fall on a 480cm sling (FF0.5).
Really well explained, I sometimes struggle with videos where there’s lots of diagrams/numbers on screen (perks of the ADHD I think) but this helped me grasp it a little clearer, cheers!
Glad you liked it 💪
Great video. Important info for climbers to have. We should know the limitations of our gear but also the different situations in which those limitations can change.
I use a 480cm sling with overhand knots for my PAS. I typically use one of the overhands as a shelf. I like how versatile it is. Can be a quad if needed, or a step for an ascender. Can even string it together with a microtrax for a ghetto ascender in a pinch.
Plus an overhand in dyneema slips are 8kn, so as long as I'm clipped into a shelf, it should slip, not tear. Still don't clip into anything with a fall risk though.
Thanks JB, great vid. Slightly tangential comment (nerd alert!): the force on protection points (e.g. Dave Mac's bust nut) is higher than the climber feels: basically it is the tension from the belayer plus the tension from the climber minus the energy absorbed by the rope and other dissipating bits (knots etc). So trad gear and compromised rock can break even if the fall isn't massive. Soft catches (or quickdraw screamers) can help in scenarios where the leader isn't going to hit something!
Yeah, I can only say so much in one already long video!
Petzl explain it well here :)
m.petzl.com/US/en/Sport/Forces-at-work-in-a-real-fall?ActivityName=Multi-pitch-climbing
Great video I use slings a lot and true if they are use correctly and your mindful on the incorrect use it’s all about boing your kit and watt could happen if used wrongly!!! Keep up the great work on the vids
Cheers 👊
makes you think, i use a safty harnis at work somtimes and this is stuff they don't tell you!! now we do use rope think it's 13mm normaly but its not dynamic so there's no strech if i did fall coz not all off them have a shock absorber on them some are just adjustible, normaly to as long as posible so you can move. then if you did fall you also have suspention traumer to deal with wich is another kettle off fish!!
As always a well thought out and excellent explained video. Keep,doing these please great work
As someone with serious back issues who has not been doing roped climbing for very long i chose to go with a kong slyde specifically because i could choose a really stretchy rope for it (and take out any slack).
Taking any kind of shock load when I'm already in a lot of pain all the time is something i can do without.
That was a belter Jez! As you said it’s understanding of what’s behind the decision making that is key. I think that people latch onto the number that is associated with the knot making the sling weaker. They don’t necessarily marry that up with the presence of a rope, or not, in that system. I use a Petzl Connect, but would not like to take a FF1 on it, let alone anything bigger. Even at maximum extension of just under a metre, that’s not a lot of rope. I would be interested to know how much it would stretch in a fall situation and therefore how much force/energy it would absorb?
Dynamic lanyard/sling standard limits max force for a ff2 < 10kn. High, but made not to break.
The only thing you did'nt mention and you hopefully know is that if anyone tie a knot on anything (dynema, nylon, or rope) it should be removed/untied immediately after use. This is very important for dynema and nylon because a lot of people get lazy and don't untie it for months or even years and you cannot inspect if it is damaged from inside. Otherwise whatever you said I agree with you.
The way I understood the how not to video is that the rock enforcer result of 4.4kn was an erroneous result as it wasn’t set up for shock load measurement. Both linescales measured 2.9 ish iirc.
Good info well presented.
Thanks! 👊
Sound. 👍
👊
Ok, so, if I am belaying a leader who is heavier than me, and I'm clipped into a dyneema anchor with a petzl adjust, and the leader falls, yanking me into the air... should I then be wary of the petzl adjust? I generally get pulled higher into the air with a lead fall than the length of my landyard and anchor. Meaning they would be subject to force. Just upwards rather than downwards.
You’re not going to break any slings or anything in normal circumstances but clearly you’ll need to make sure whatever setup you’ve got can take an upward pull. The leader pulling you up still has dynamic rope involved so you’re not going to see sling breaking forces.
@@JBMountainSkills thank you! And thank you for this video and all the other videos!!
Loved the video.
If I remember correctly the DMM literature that comes with their slings tells you not to tie knots in them?
Glad you liked it!
I checked the DMM user info that comes with slings before the video. It warns of having slack etc, it also shows knots weakening slings by 50% but doesn’t say don’t do it. Similarly BD shows a caution notice, not a do not do it notice and says knots will reduce the 22kn breaking strain.
@@JBMountainSkills thanks for your hard work.
As a fellow climber these videos are really helpful in preventing paralysis by fear!
My pleasure :)
I don't think you mentioned it, but the DMM tests used a steel weight. Humans are fairly squishy, so forces will be a lot lower than the DMM test results
Yeah I did mention it at the beginning, 80kg metal lump
I dont think you conclusions are correct. You need the 80 kg rigid steel mass to break the sling. I definitly dont think you will be able to break a sling by falling onto it with your body. You will have other problems, but not breaking the sling.
Thanks, JB for the great video However, the real tragedy is the simple fact that you have to make such a video. Climbing is objectively hazardous and the data and testing on every single piece of gear has been completed and analyzed into oblivion. Compounded with the eternity of climbing experience of those working professionally, along with those performing the gear tests. How there can still be so much incessant and mindless chatter around this issue is absolutely baffling!! and for those who still find climbing dangerous and desperately and earnestly try to root out every conceivable hazard and danger, YOU WILL MAKE A BOZO NO NO MISTAKE BEFORE YOUR GEAR FAILS! I could go on forever about how tying knots in Dyneema or nylon will not cause the universe to implode. though, it never keeps folks from mistying their knot, putting the rope through the belay device backward, and not paying attention when belaying. Or simply overwhelmed by problems that have already been solved.
A common scenario that happens a lot is that the leader forgets to unclip from the master point as they continue the climb. A slip before unclipping could mean a potential FF2 into the Anchor (without having "loads of stretchy rope").
For me, the lesson from this video is that Dyneema is often misused, for example for lanyards and anchorbuilding. It's literally the worst possible material for this use. Try anything else and it works better. Dyneema Slings are for extending protection, slinging trees, quickdraws etc.
I disagree that dyneema is not suitable for anchor building. I thinks it's definitely appropriate in many situations.
A nylon quad anchor (or similar) is also going to generate very high forces in a FF2 as described above, so it's probably best just to be careful and not rush things + be methodical, especially when things are going on that are taking your attention away from what you're doing (even if only momentarily)
@@JBMountainSkills you should have a look at this chord. Iam using it right now and performs quite good. Salewa Ortles Master chord 6MM. Dyneema core and PE sheath. Makes the knotability better, at least that is what the manufacturer promises. Don't get me wrong, if iam on a dyneema sling anchor iam feeling save, but iam feeling saver with another type of material used as sling like Kevlar, Master cord or a Dynaloop.
I disagree, the weight saving and lack of water absorption in the alpine makes dynema king. Anchor building is totally fine as long as you don't build slack into the system, even then it's fine unless you're doing something else crazy. I mostly agree regarding lanyards, but I also often use my BD Alpine Link System for weight considerations. I think the critical thing is just to understand your gear, what it's meant for, and what the hazards are.
To say dynema is the devil is very limited thinking.
If people are worried about slings, due to newtons law, they should be more concerned about slings on draws not anchors. The last piece of pro you fall on, be that a sport draw or cam with a sling extension, is taking 200% of the fall force (mitigations from rope stretch or friction not subtracted).
The anchor opposes (newton) the forces generated by gravity and the climber which means that a 6kn fall is putting 12kn through that last piece (in theory).
No that’s not how it works. If a 6kN downwards force is applied to the anchor by the rope, then there is an equal and opposite force of 6kN upwards applied to the rope by the anchor. This opposite force is not applied to the anchor. Only 6kN is applied to the anchor.
To think of this, imagine you punch a wall with a force of 1kN. In this example we assume The wall has a breaking strength of 1.5kN. You apply a force of 1kN to the wall. Your hand hurts afterwards because the wall applies 1kN force back on your hand. The wall doesn’t break because the force applied to it is less than its breaking strength. We don’t add together the equal and opposite forces and apply them to the wall.
Hope that helps.
Might be of interest: m.petzl.com/US/en/Sport/Forces-at-work-in-a-real-fall?ActivityName=Multi-pitch-climbing
@@JBMountainSkillsin this article I’m assuming by anchor they mean the last quickdraw? I didn’t make it clear, but I was using your example of a second belaying directly off of the anchor. In the link shared the anchor (last piece) is taking an additive force real world of course rope stretch friction etc takes some out but it shows that the last piece takes more force than either end of the rope.
@@Unbillieveablemaybe I didn’t describe the example well enough. When a second is belaying directly from an anchor and the leader falls (or rests) on a piece, in an ideal theoretical scenario that piece is taking 200% of the force to stop the climber/keep them hanging. That’s the most vulnerable length of dynema/nylon not anything used to build an anchor.
@@Unbillieveable He's right. The force is doubled. Or rather the last piece of pro experiences the combined total force involved in the system. (The Petzl page gives examples.)
The biggest issue is the use of a metal mass. It is simple and convenient and we have built the norms for climbing gear on tests with a metal mass. However, metal does not absorb any energy. So this is not the worst case that could happen in reality, it is a lot worse. (!!)
Nowadays, lots of research into climbing gear does not use a meal mass but instead uses sandbags (still very rigid) or a tractor tire. To my knowledge, the tire behaves best like a human body and is better suited to establish a worst case scenario. Repeating the same test with tires showed that the slings do not break. A climber's back would, however. So this does not change the recommendation to avoid slack when falling on slings
I believe the 80kg mass was adopted because it gave similar results to a 100kg climber in a sit harness. That’s info from someone involved in that side of the industry.
I would have to look through my archive if I find anything relating to that. But I would be surprised if that was the case, as metal is just so much more rigid than a climber, even a heavier one. Basic physics tells us that increasing the time of acceleration/deceleration by just a tiny bit has a very large impact on peak forces.
Experiments by Chris Semmel have shown that for a 120cm sling, it takes a fall of about 4m (FF3 > 3) to break the slings when using a sand-filled tire. So unless someone is misusing their slings as a ferrata set, the sling will not break.
Link to the experiment mentioned (in German, but you might fight a translator)
chris-semmel.de/wp-content/uploads/2021/02/faqs-dyneema.pdf
Some of the comments are funny. Your wasting your breath Jez
I may be one of the persons who commented strongly about this subject and my opinion hasn't changed much over the years: reaching the end of multi pitch and getting any skinny dyneema sling for connecting oneself for abseiling is something I consider sketchy. Especially if you knot it to attach your belay device.
1) its the moment you are most tired and have higher chances of 'falling' into the sling in a shitty belay station
2) you are using gear which you have no intimacy with, perhaps it's the least regarded piece of equipment anyone has in their rack. You often don't know what it has been through and now it's employed as your only life line.
3) i feel like arguing "you should not fall and always stay tight" is unrealistic. even the pros will make basic mistakes when tired after a long day
Still, regarding all that, I'm not saying I would never do it, its just not part of my routine and I would not recommend it to a friend.
I want to add that I really like your videos and the thoughts you share.
terribly english channel, have to play at twice the speed to cut the fluff about the dog and the weather, don't change haha
Shout out to Ryan at @HowNOT2 , love you and him both!