This is interesting to get more into different type of personal anchors. Looking forward to seeing Petzl adjust and hopefully Kong slyde as well. I guess that would cover almost all common personal anchors.
@@thefack149 I never noticed eashook. That could be so handy in some applications and you can attach it to a sawn loop too (unlike some other similar models I have). In general use I tend to find triple locking carabiners or ball lock ones quite fast to use.
I appreciated this simply because of the knit tying tutorial. Then, additionally the shock absorption was quite interesting. I’m not a fall-geek, and still enjoyed your efforts.
Been using things like this purcell prussik for roof and chimey jobs for years. Never taught , but seemed good use of knot skills learned in my youth helping arborists. So glad to see testing on something I do. But yes, It is not my sole safety for steep pitch or other serious consideration where I may think a deadly whipper would be on the agenda before the next break.
Glad I'm a caver, not a climber. We don't have to worry about shock-loading. All of our lines are static, most of them 11mm pit rope. Avoid sharp edges and you're fine. In fact, we have a couple of 13mm static ropes that will cut a groove in the limestone rather than get damaged themselves. We use those for fast and dirty recon of new sites. The only drawback is they're very heavy.
Yeah, fewer wraps generally means it slips at a lower force. That's good if you're trying to get a bigger ratio between the slipping force (ideally ~4-5kN?) and the breaking force (ideally 15kN+).
Love the Purcell Prusik on a loop! I've been using them for over 10 years as my primary anchor system. I use 2 of them as my PAS for sport climbing and 1 when multi-pitch climbing. 6mm accessory cord tied with a double fishermans knot girth hitched to my harness hard points It's so nice to be able to easily get into the most comfortable position at an anchor. Great video, thanks for testing!
I use this as an adjustable manual handbrake on a temporary rope zip line on my property. It trails behind the zip line pulley with no weight on it. You lightly wrap your hand around it (with gloves on of course) and as you’re approaching the end of the line you take your hand off. As the prusik is trailing the pulley and all of your forward momentum and weight are on the pulley which is clipped into your harness as the prusik starts to engage it starts to shift your weight from the pulley to having your weight on the prusik giving you a soft catch. Work’s beautifully! As the pulley then naturally travels back to you as it has less resistance, it shifts your weight back onto the pulley at which point you can easily reach up and tend the prusik with your hand again. The system also does a wonderful job at not turning you into a human pendulum. I know this is not ideal zip line setup but for a line that gets moved around the property and setup with dramatically varying levels of speed and height the system works extremely well. Way better than trying to rig and re rig tire, compression spring or bungee breaking systems all the time.
Not sure if this is going to make sense, but there are two concepts I was given for the Purcell Prusik. 1st: You can tie it with the knot inside the prusik loop to maximize how short you can make the loop, but limits the extension a little. The std design with the knot outside of it limits how short you can make it. 2nd: This concept came from an OG SAR climber I know...you can make double Purcell Prusik by using a much longer cord (30'?), and tying a second Prusik on the tail end (where you usually connect to your harness) after completing the construction of the std Purcell. You then pass the first/completed Purcell Prusik through that second one and you can girth hitch the middle to your hard points. This gives you two adjustable tethers (and a mountain of cord).
Recreational tree climber Arborist climber Bushcraft enthusiast I start your videos without enough time to finish them, but I usually look forward to and do come back … I love your videos Thank you for making them!
I find an easy way to make the purcell is to make the Prussik on an empty toilet paper roll, that way it's shaped nicely and easy to dress. then put the other end through and then pull out the roll and tighten. Yes other methods are easy enough, but especially on longer purcells its nice to get all the twists out and such before putting it through the prussik and this holds it all in place nicely.
This is all super interesting!! But, I'd also love to see some less "extreme" fall examples. Yes, I know these fall factor ~2 falls are interesting to see, and it's always fun to see gear break. However, I think some "sensible" falls where the person isn't really above the attachment point (FF < 1) would be very informational!! It would be amazing to be able to see the different forces one would feel if one fell on pas (dyneema loops), dyneema sling, nylon sling, purcell, connect adjust, etc.
Cool to see these results! I use a 60cm nylon sling (girth hitched) for my PAS when single pitch climbing and when I am multipitch climbing I always clove in using my rope. Seems like regardless of what method you use, the basic gist is don't go above the anchor and if you do then don't fall onto your PAS
The effect you describe with the maximum force is called jerk or jolt, thats the change of acceleration over time (da/dt). Love your videos, great job!
Great stuff. I use a Purcell prusik as a personal anchor, but I place the double fisherman close to the prusik knot to maximise the length adjustability. Probably doesn't effect the strength much but a friend had the double fisherman get partially inside the prusik when the prusik got loose, so that's a risk to be aware of.
Ryan brings up a very valid point against purcell prusiks, and i want to give my work around You cannot tighten a purcell prusik one handed. You have to completely unweight it and use 2 hands which really sucks if you're trying to tighten up on an anchor My solution is to get some paracord or something similar and make a small prusik loop on the 2 strands that feed back into the prusik, NOT the strands going through the prusik You can pull on your small prusik to introduce slack into the purcell, and use that same hand to pull the knot in and shorten everything up. Its not perfect but its very handy to know about
I know it's an old video but the updated way of tying a purcell does not have a bfk; just a double fish, a prusik and the girth hitch to your hard points. If you need a shelf you can add or remove an overhand. It's much more simple to tie and can be easily converted to a loop of cordalette.
I'd be interested if the friction of the Purcell Prusik could be tuned with a lower friction material lining the knot or a sheath. Granted it would either have to melt during the slide as to not slip too much or the sheath would need to have a gradient where the friction would increase the farther the knot slips.
@hownot2 Thanks for the video. I do rescue so we use Purcell Prusiks all the time. Are you familiar with the Aztek Edge Kit? We use them as personal anchor, travel restraint and for patient rescue and a million other things.
I've been using the klemheist version of this for years with a 6mm cord. Not sure I'd ever go to anything else for the price. I've got mine set to a fully stretched arms length. I'd love to see what you could get if you fell with your super long one. Haha
You already covered a lot but I feel like if people are really worried about shock load they could just do one less wrap when setting up the Purcell Prusik.
I've been using this setup for multipitch rock climbing with 5m of 6mm cord, but I use a double fisherman's and add a butterfly above for an extended rappel!
Have you tried this with Robert Chisnall’s Modified Tarbuck Knot? Intended for anchoring rope to a tree or post. Requires at least 3 wraps around the tree before tying the knot.
Great content Ryan. Regarding the long high line one you used. I found it more practical to use a climbing rope or section of rope tied in with a standard tree climbing system. Weave it through/around the anchor, clove hitch one side to a biner/harness, and leave a tail for a Blake's hitch. Super practical and you can have about as long of a system as you want while being able to wrap it around things like trees and poles if you want. Perhaps even more practical with a split tail or eye n eye. Idk maybe one more thing to play with.
With dyneema woopie sling you can theoretically find the optimal length for "stuck through" part. It is also possible to make few such parts with pulled out parts of rope between "stuck through" parts. This can make gradually increasing stopping forcethat can be adjusted. Friction parts of rope will be distributed so heat problem should also be less of a worry
FYI: spine breaking is probably what you worry about when talking about the body taking the force. The part of the spine that is probably most worrisome can resist about 2kN before accounting for soft tissue that'll absorb some force. (in vitro) When they studied forces on patients in vivo, it seems that the back can take about 3.4/3.7 kN before ~50% of folks will break their low/mid back (granted, the studies include older folks, avg age ~50 since that's who gets most back fractures in the medical world). Younger folks can tolerate ~4-6kN and part of that depends on how much time the force is spread over (as Ryan mentions), but also other factors like if you're upright/vertical vs horizontal when you the rope catches (e.g. horizontal = more torque and force on weaker parts of the spine vs vertical = more compression on the parts of the spine that are used to seeing some compression... same concept as compressive vs shear forces when you're talking about breaking bolts... except on your spine...). Also, in the physics/biomechanics world, the technical term for force over time is "impact". Force spread out over more time = less impact. Concentrated into less time = more impact. Makes sense if you think about a whip. Barely any force, yet cracking a whip hurts because it's such a short time = more impact.
Im a boulderer and about a month and a half ago fell 25 feet, thus breaking my spine exactly where you just said (L1 burst fracture) I’ve been curious about how many kilonewtons the fall was but it’s hard to tell. I’m assuming it was somewhere in the 6-8kn zone. Got surgery and am doing better now, soon to return to climbing
pre-watch thoughts: the biggest issue i see with using a friction hitch for "shock absorption" is that the shock is just going to lock the hitch. it you want shock absorption, you either need something elastic or something mechanical which will always slide at a specified load, no matter how off-center or angled the applied load is.
08/02/2023 Hello How. This video was very interesting. I did not know about using this rope knot on a rescue basket. The second point is what if you use one additional loop in the prusikis. I have used this knot but not very often because I do not do tree work. My weight is over 300 lbs when loaded to work. My naked weight is just under 250 lbs. The four loop prusiks are both for climbing and movement in the tree. I do enjoy watching the profession plan for a fall. That tales BALLS Thanks again, DON
My takeaway is that for factor falls greater than 1.5 ish you really need a screamer of some sort. But that's not really a thing when climbing and walking around above the anchor is really common.
I use the Purcell Prussik as my personal anchor/leash with a 7mm nylon cord but I drop one of the loops on the load side of the prussik knot. This (in theory) will reduce the friction in the prussik knot and maybe reduce the peak loads on your tree drop test.
I made my own Personal Anchor out of a section of Resc Tech (teufelburger) and a 7mm Sterling acc cord in a michoacan hitch, and use a kong Ottino as a prussik tender. it works great for single handed adjustment to shorten or lengthen, and is #supergoodenough that I don't feel the need to buy a connect adjust, etc.
Great video! Even though it was a long one you packed in so much information and clever tests. I can see myself sharing this with people in the future :)
I can appreciate the skill, knowledge and consideration of so many factors demonstrated in these tests. The one thing missing, I think, is an explanation of the relevance/meaning for the "average climber". Is one sling construction significantly better/safer than the others? Or are these sling variations just for use in 'advanced' climbing and not relevant for the rest of us? Yes, I did watch the last few minutes of this video. But telling us to go watch other videos and blogs and suggesting (sort of) that we shouldn't use "personal anchor systems" (at all?) because the tests seem to show that they aren't safe doesn't seem like a satisfactory conclusion to a 18 minute 'technical analysis'.
I've broken out of a tree twice and was saved by my rope without my split tail slipping. The bounce in my True Blue made both events comfortable so my opinion is that whether or not your fiction knot slips doesn't matter.
it would be cool if you got a thermal camera to monitor the friction heat during slow pull tests, if not for actual data then just for the visual aspect
Just out of curiosity, why would you or anybody else need/want a measurement of energy here? It's not a very useful metric for the use of this kind of equipment, which is why everything is rated in terms of force. Theoretically you could get a rough approximation of the energy by slapping a meter stick to the drop tower and using E = m*g*h where m is mass, g is 9.8 m/s^2 (gravity on earth) and h is the total distance traveled from the beginning to end. This would only work with really static lines though, like dyneema. If you wanted to find it with a more dynamic system you could do a simple pull test to find the spring constant k via hooks law (F = k*x) and then use E = 1/2*k*h^2. That said, your value for k will be very different when the system has knots that slip, deform, etc. and hooks law would still be a rough approximation at best. My point is you *could* roughly calculate the energy and power with relative ease, but it doesn't give you any useful information so why would you bother? It's appropriate that force is the primary metric to consider here. Energy is kind of an abstract measurement for assessing safety in these kinds of systems, force is all we need to make well informed decisions. It's like wanting your car speedometer to measure energy; sure you can do it but it's kind of irrelevant as speed is a much more useful thing to know.
@@BridgetWirth A spring is poor model for textiles (cordage, webbing, rope, etc) in destructive pull tests: energy is dissipated in the frictional heating and melting of the weave, plastic deformation of the fibers, chemical bonds being stretched and broken, etc. Once a metal spring experiences plastic deformation, you can throw Hook out the window. The human body is incapable of generating the same forces as a rigid mass, especially for shorter drops and less elastic/dissipative textiles, a rigid mass is a poor predictor. But, like you said, gpe is trivial to calculate, and it might be interesting to compare that to the Joules/meter that a textile can dissipate during failure.
@@BridgetWirth For example, we know that a 1m rope will survive the 700J of energy in a 1m fall. The complication I guess with doing the same exercise with dyneema, a larger portion of that 700J is going into the climber's kidneys and spine.
@@BridgetWirth Energy is a measure for how much of a fall it can hold on its own before it's fully extended (or breaks). A shock absorber that can absorb 6kJ over 1.5m of distance before it is fully extended can hold an 80kg person that fell 6.14m (from start of the fall to the first point where the shock absorber is under tension), assuming there are no other shock absorbing parts in the system.
Hi! Maybe for the "not adjustable end" you could try a... Double bowline... I'm not sure how call it. I mean the same knot which is used by Stefano for example. Anyway, thanks for this one, I really enjoyed it
I kinda just want to use a screamer as a personal anchor now. Yikes! Absolutely breaking my gear fear and placing it where it should be. On fall factor twos!
I use double Purcell Prusik (PP), 1 big loop with 2 PP at the ends girth hitch it to the harness, with big wirelock carabineer. Find it super useful, Apples to apples seems safe enough.
I've never done climbing, but I am a sailor & Tugboat operator, so I've done a lot with ropes. In construction and shipboard safety harnesses, they include an engineered shock absorber that is a replace after it dose its job tool . I'm sure it weighs more than the slings you are making, but you can count on the amount of shock absorption it will provide.
In climbing, a single use absorber is called a screamer. They're not used very much at all because of the cost of replacement, bulk, and at we simply avoid taking any falls that generate enough force to need a screamer. They are used in ice climbing for marginally strong ice anchors, but on rock you'll pretty much never see them.
With the dyneema you tested near then end, with it slipping well below 1KN, we shouldn't even expect it to slow you down, only make you accelerate slightly less quickly. That slight drop in the rate of acceleration is completely counteracted though I would suspect from the additional travel distance of the fully extended prussik. Meaning it basically it is worse than nothing and you are taking a hard fall on static protection.
We’ve made Purcell prusiks out of 8mm dynamic half/twin rope with the thought that it will provide even lower forces in a fall. I’d be curious how that compares and if there’s anything we’re overlooking making that a bad idea.
Nice video! I was hoping you'd try taking loops out of the pruzuk. Maybe if it was 2 on one side and 1 on the other, instead of 2 on both sides, it would slide more. Having the too loops above and the single loop below i would expect to slide easiest
After you video on cow's tails, I was wondering, "OK, but how does a Purcell-Prusik anchor do in similar conditions?" I had not gotten around to asking directly, but here you are, anyway, with a video on the Purcell-Prusik. As if you'd read my mind... Background: I come from a world that is not generally populated with rope-climbing knowledge but nevertheless fall protection is of great interest: namely square-rigged sailing ships. The things we climb are intentionally designed to be climbed and, in general, falls are actually pretty rare. In the old days of wooden ships and iron men, there was no fall protection at all. If you fell, you fell. End of story. But as this world has moved on, over the course of the last 120 years, evolving from commercial shipping into sail training and historical interest, there is a greater emphasis on safety. Fall protection has taken a higher priority due to insurance and the desire of organizations not to damage their volunteers/employees. These organizations have, slowly, evolved various systems to protect (at least, in theory) their sailors. But in many ways, this world is still a long way away from the climbing world. A common way of thinking is that, as long as the gear doesn't break and you stop the fall, life is good. Climb down and have some tea. Not a lot of thought is given to shock loading or what a fall factor 2 can do to a human body if abruptly arrested. You would absolutely shudder if I told you what was being used for fall protection 20 years ago. We've evolved since then, and currently, in my organization, we are using a Purcell-Prusik as a personal anchor (we say "lanyard" because, well, it's nautical...). It's made 10mm dynamic line. I'm told that it was tested and deemed "plenty good enough" if one were to fall on it. And perhaps it may be, but I have always been thankful that I have never found myself putting the theory to the test.
I never intend to climb anything more difficult than a 15 foot ladder. However, I would not do anything with any sort of string, rope or line without checking your videos first. I have seen others do videos on splicing Dynemma and realized your videos are the only ones I trust. BTW, Dynamma is an interesting product. It is super strong, but has some interesting quirks that I discovered on your videos.
Did you clip the end of the daisy or shorten it? If you clipped the end it’s equivalent to testing the fully extended Purcell. A (correctly) shortened daisy seems more useful to test and might absorb better
I like the double fisherman, but i start it like you started the figure eight, and tie the fisherman around both ends, that way it makes an eye that will cinch down on the carabiner when weighted so it stays put better.
hi, I was wandering... close to4:30min, is there any reason why not to do first the prusik and after the figure 8 knot? isn't it be easier to go through the pursik knot if we have the tail free? thanks for the video, by the way :)
11:52 after doing the drop test on the prusik, were you able to move the... knot? up and down again or does it just fuse to the rest after stretching and pulling?
If you get the chance to it might be fun to test the petzl adjust vario it would be interesting to see how strong it is compared to the regular petzl adjust with a sewn end
So call me crazy, but the only application I've ever considered for the PP is for rope soling (on lead) a bolted route where finding a ground anchor (boulder, tree, good low crack) is not an option. The idea being: climb to the first bolt, clip a PP to it, then clip the end of the rope to the sliding end of the PP (having pre-connected other end of rope to my grigri on my belay loop). Crazy? Indeed. But potential advantages: (1) if you fall shortly above the 1st bolt, the PP should keep the fall force below factor 2 (but seeing the video, I'd keep the PP on 6mm or less to get more slippage and lower forces), and (2) once clipped into the 2nd bolt, the PP would add a little bit of dynamic quality for a fall (not much due to friction thru 'biners, but more is better in this case IMHO) and so that's good. I do loads of rope-solo leading and don't bother with a PP if I have a good ground anchor, as there's plenty of dynamic quality in the system once several meters of rope are out and the first piece has been placed, especially given that I'm not (and no one should) ever taking big whippers while rope soling... So I'd love to see the PP tested in this kind of application...
i made my Prucell out of Edelrid Aramid cord sling. been working amazing for years. since the aramid is a lot stiffer its a lot easier to handle and adjust, but id love to know how it compares to nylon or dyneema that you tested here.
Is there an official name for the "figure of 8 bfk flemish sort of a knot"? It looks like a safe variation of the flat 8. Also, why the two specific options for the bend. Wouldnt any critically safe bend be ok?
Hey, would You test via-ferrata kits eg. compare fall on dynamic rope vs kit with absorber. More interesting is how to carabiner lay on the steel line anchor, during the fall on vertical route, it makes the carabiner is cross loaded and side way loaded when hit the anchor point and the steel line is pre-tensioned high - I think this is the weakest point.
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Much love, thank you *I wish we were neighbors
This beginner who's trying not to die appreciates knowing that prusiks should be 3mm narrower than the host rope. Thank you!
This is interesting to get more into different type of personal anchors. Looking forward to seeing Petzl adjust and hopefully Kong slyde as well. I guess that would cover almost all common personal anchors.
Absolutely! Do the Petzl adjust and Kong Slyde!😊
@@testboga5991 for the Kong Kisa also!
Petzl adjust is just so smooth and with an eashook it's so fast. Bulky, yes, but so quick to deploy and take slack
Vote for petzl adjust
@@thefack149 I never noticed eashook. That could be so handy in some applications and you can attach it to a sawn loop too (unlike some other similar models I have).
In general use I tend to find triple locking carabiners or ball lock ones quite fast to use.
I've tried the two finger method and it really makes the hole bigger. Excellent
Phrasing lol
You shoud try four finger
I appreciated this simply because of the knit tying tutorial. Then, additionally the shock absorption was quite interesting. I’m not a fall-geek, and still enjoyed your efforts.
Been using things like this purcell prussik for roof and chimey jobs for years. Never taught , but seemed good use of knot skills learned in my youth helping arborists. So glad to see testing on something I do. But yes, It is not my sole safety for steep pitch or other serious consideration where I may think a deadly whipper would be on the agenda before the next break.
Glad I'm a caver, not a climber. We don't have to worry about shock-loading. All of our lines are static, most of them 11mm pit rope. Avoid sharp edges and you're fine. In fact, we have a couple of 13mm static ropes that will cut a groove in the limestone rather than get damaged themselves. We use those for fast and dirty recon of new sites. The only drawback is they're very heavy.
Glad I'm a sofa rester, not a caver or climber. We don't have to worry about ropes and knots.
@@nomars4827im gland im a human and not racoon, i don t have to warry about searching in the trash for food...
At least for now
glad i’m reading the comments
caving is gruesome and awesome at the same time! former climber and caver here
I'm glad to be alive
as a user of the Purcell Prusik, this is a super useful video! I use a 3 /2 wrap instead of just having 3 wraps on each side.
Yeah, fewer wraps generally means it slips at a lower force.
That's good if you're trying to get a bigger ratio between the slipping force (ideally ~4-5kN?) and the breaking force (ideally 15kN+).
This is an outstanding video. So informative, covering the topic so well. I will recommend it to many people.
Love the Purcell Prusik on a loop! I've been using them for over 10 years as my primary anchor system. I use 2 of them as my PAS for sport climbing and 1 when multi-pitch climbing. 6mm accessory cord tied with a double fishermans knot girth hitched to my harness hard points It's so nice to be able to easily get into the most comfortable position at an anchor. Great video, thanks for testing!
The consistency of inconsistent materials is super comforting, and these videos are great for understanding climbing systems.
Thank you
Very interesting, goes to show that no matter what kind of PAS you're using DO NOT FALL ON IT, at best you'll be hurting.
I use this as an adjustable manual handbrake on a temporary rope zip line on my property. It trails behind the zip line pulley with no weight on it. You lightly wrap your hand around it (with gloves on of course) and as you’re approaching the end of the line you take your hand off. As the prusik is trailing the pulley and all of your forward momentum and weight are on the pulley which is clipped into your harness as the prusik starts to engage it starts to shift your weight from the pulley to having your weight on the prusik giving you a soft catch. Work’s beautifully! As the pulley then naturally travels back to you as it has less resistance, it shifts your weight back onto the pulley at which point you can easily reach up and tend the prusik with your hand again. The system also does a wonderful job at not turning you into a human pendulum. I know this is not ideal zip line setup but for a line that gets moved around the property and setup with dramatically varying levels of speed and height the system works extremely well. Way better than trying to rig and re rig tire, compression spring or bungee breaking systems all the time.
Nice! just check it for wear often, going fast on a zip line you'd have to worry about friction melting the prusik
Three extra guys and an old mattress :)
Not sure if this is going to make sense, but there are two concepts I was given for the Purcell Prusik.
1st: You can tie it with the knot inside the prusik loop to maximize how short you can make the loop, but limits the extension a little. The std design with the knot outside of it limits how short you can make it.
2nd: This concept came from an OG SAR climber I know...you can make double Purcell Prusik by using a much longer cord (30'?), and tying a second Prusik on the tail end (where you usually connect to your harness) after completing the construction of the std Purcell. You then pass the first/completed Purcell Prusik through that second one and you can girth hitch the middle to your hard points. This gives you two adjustable tethers (and a mountain of cord).
Recreational tree climber
Arborist climber
Bushcraft enthusiast
I start your videos without enough time to finish them, but I usually look forward to and do come back … I love your videos
Thank you for making them!
I find an easy way to make the purcell is to make the Prussik on an empty toilet paper roll, that way it's shaped nicely and easy to dress. then put the other end through and then pull out the roll and tighten.
Yes other methods are easy enough, but especially on longer purcells its nice to get all the twists out and such before putting it through the prussik and this holds it all in place nicely.
This is all super interesting!! But, I'd also love to see some less "extreme" fall examples.
Yes, I know these fall factor ~2 falls are interesting to see, and it's always fun to see gear break.
However, I think some "sensible" falls where the person isn't really above the attachment point (FF < 1) would be very informational!!
It would be amazing to be able to see the different forces one would feel if one fell on pas (dyneema loops), dyneema sling, nylon sling, purcell, connect adjust, etc.
Dude, your videos have gotten soooo much better! And still improving man, this was such a good video!! Thank you!
Cool to see these results! I use a 60cm nylon sling (girth hitched) for my PAS when single pitch climbing and when I am multipitch climbing I always clove in using my rope. Seems like regardless of what method you use, the basic gist is don't go above the anchor and if you do then don't fall onto your PAS
From now on, this will be the youtube video I'll search for when i try to remember how to tie this!
The effect you describe with the maximum force is called jerk or jolt, thats the change of acceleration over time (da/dt).
Love your videos, great job!
Great stuff. I use a Purcell prusik as a personal anchor, but I place the double fisherman close to the prusik knot to maximise the length adjustability. Probably doesn't effect the strength much but a friend had the double fisherman get partially inside the prusik when the prusik got loose, so that's a risk to be aware of.
2:20 - 3:15 very helpful sling / general purpose loop knot tying.
Ryan brings up a very valid point against purcell prusiks, and i want to give my work around
You cannot tighten a purcell prusik one handed. You have to completely unweight it and use 2 hands which really sucks if you're trying to tighten up on an anchor
My solution is to get some paracord or something similar and make a small prusik loop on the 2 strands that feed back into the prusik, NOT the strands going through the prusik
You can pull on your small prusik to introduce slack into the purcell, and use that same hand to pull the knot in and shorten everything up. Its not perfect but its very handy to know about
Great video Ryan. Loved the "how to" set it up with different examples. Thank you.
Second video on your channel that covers a topic I was just researching by chance 😂
I know it's an old video but the updated way of tying a purcell does not have a bfk; just a double fish, a prusik and the girth hitch to your hard points. If you need a shelf you can add or remove an overhand. It's much more simple to tie and can be easily converted to a loop of cordalette.
13:08: the tip of making the PP extra short is GOLD!!!
I'd be interested if the friction of the Purcell Prusik could be tuned with a lower friction material lining the knot or a sheath. Granted it would either have to melt during the slide as to not slip too much or the sheath would need to have a gradient where the friction would increase the farther the knot slips.
Been waiting for this!!! Thank you so much, can’t wait wait for the next one
Sobering. Outstanding. Mans out here doing God's work.
@hownot2
Thanks for the video. I do rescue so we use Purcell Prusiks all the time. Are you familiar with the Aztek Edge Kit? We use them as personal anchor, travel restraint and for patient rescue and a million other things.
I've been using the klemheist version of this for years with a 6mm cord. Not sure I'd ever go to anything else for the price. I've got mine set to a fully stretched arms length. I'd love to see what you could get if you fell with your super long one. Haha
You already covered a lot but I feel like if people are really worried about shock load they could just do one less wrap when setting up the Purcell Prusik.
You can add a little loop above and adjust in both directions with one hand
I've been using this setup for multipitch rock climbing with 5m of 6mm cord, but I use a double fisherman's and add a butterfly above for an extended rappel!
Thank you stranger! I'll be trying this next time I'm outdoors
Have you tried this with Robert Chisnall’s Modified Tarbuck Knot? Intended for anchoring rope to a tree or post. Requires at least 3 wraps around the tree before tying the knot.
Terrific video . Why can't We tie a double bowline on bight for the belt anchor point?
Super informative, and love some Prusik knots!
Great content Ryan. Regarding the long high line one you used. I found it more practical to use a climbing rope or section of rope tied in with a standard tree climbing system. Weave it through/around the anchor, clove hitch one side to a biner/harness, and leave a tail for a Blake's hitch. Super practical and you can have about as long of a system as you want while being able to wrap it around things like trees and poles if you want. Perhaps even more practical with a split tail or eye n eye. Idk maybe one more thing to play with.
With dyneema woopie sling you can theoretically find the optimal length for "stuck through" part. It is also possible to make few such parts with pulled out parts of rope between "stuck through" parts.
This can make gradually increasing stopping forcethat can be adjusted. Friction parts of rope will be distributed so heat problem should also be less of a worry
FYI: spine breaking is probably what you worry about when talking about the body taking the force.
The part of the spine that is probably most worrisome can resist about 2kN before accounting for soft tissue that'll absorb some force. (in vitro)
When they studied forces on patients in vivo, it seems that the back can take about 3.4/3.7 kN before ~50% of folks will break their low/mid back (granted, the studies include older folks, avg age ~50 since that's who gets most back fractures in the medical world). Younger folks can tolerate ~4-6kN and part of that depends on how much time the force is spread over (as Ryan mentions), but also other factors like if you're upright/vertical vs horizontal when you the rope catches (e.g. horizontal = more torque and force on weaker parts of the spine vs vertical = more compression on the parts of the spine that are used to seeing some compression... same concept as compressive vs shear forces when you're talking about breaking bolts... except on your spine...).
Also, in the physics/biomechanics world, the technical term for force over time is "impact". Force spread out over more time = less impact. Concentrated into less time = more impact. Makes sense if you think about a whip. Barely any force, yet cracking a whip hurts because it's such a short time = more impact.
Im a boulderer and about a month and a half ago fell 25 feet, thus breaking my spine exactly where you just said (L1 burst fracture) I’ve been curious about how many kilonewtons the fall was but it’s hard to tell. I’m assuming it was somewhere in the 6-8kn zone. Got surgery and am doing better now, soon to return to climbing
pre-watch thoughts: the biggest issue i see with using a friction hitch for "shock absorption" is that the shock is just going to lock the hitch. it you want shock absorption, you either need something elastic or something mechanical which will always slide at a specified load, no matter how off-center or angled the applied load is.
08/02/2023 Hello How. This video was very interesting. I did not know about using this rope knot on a rescue basket. The second point is what if you use one additional loop in the prusikis. I have used this knot but not very often because I do not do tree work. My weight is over 300 lbs when loaded to work. My naked weight is just under 250 lbs. The four loop prusiks are both for climbing and movement in the tree. I do enjoy watching the profession plan for a fall. That tales BALLS Thanks again, DON
My takeaway is that for factor falls greater than 1.5 ish you really need a screamer of some sort. But that's not really a thing when climbing and walking around above the anchor is really common.
With dyneema slipping at 300N, you don’t even need a fall for it to slip. If you just let it hang with the weight of a person, it would already slip.
I use the Purcell Prussik as my personal anchor/leash with a 7mm nylon cord but I drop one of the loops on the load side of the prussik knot. This (in theory) will reduce the friction in the prussik knot and maybe reduce the peak loads on your tree drop test.
I do the same but I recently switched to 5.9mm Powercord
I made my own Personal Anchor out of a section of Resc Tech (teufelburger) and a 7mm Sterling acc cord in a michoacan hitch, and use a kong Ottino as a prussik tender. it works great for single handed adjustment to shorten or lengthen, and is #supergoodenough that I don't feel the need to buy a connect adjust, etc.
My new favorite 3 words....
Super good enuff.
Love it
All your videos are interesting, this one especially Thanks.
Great video! Even though it was a long one you packed in so much information and clever tests.
I can see myself sharing this with people in the future :)
I can appreciate the skill, knowledge and consideration of so many factors demonstrated in these tests. The one thing missing, I think, is an explanation of the relevance/meaning for the "average climber". Is one sling construction significantly better/safer than the others? Or are these sling variations just for use in 'advanced' climbing and not relevant for the rest of us? Yes, I did watch the last few minutes of this video. But telling us to go watch other videos and blogs and suggesting (sort of) that we shouldn't use "personal anchor systems" (at all?) because the tests seem to show that they aren't safe doesn't seem like a satisfactory conclusion to a 18 minute 'technical analysis'.
I've broken out of a tree twice and was saved by my rope without my split tail slipping. The bounce in my True Blue made both events comfortable so my opinion is that whether or not your fiction knot slips doesn't matter.
very informative video, thanks
Thanks for the testing.
it would be cool if you got a thermal camera to monitor the friction heat during slow pull tests, if not for actual data then just for the visual aspect
Can your pull tester integrate force over distance to calculate energy? I think that'd be a useful datapoint.
I think it only measures time and not distance, but with a separate x(t) measurement, it should be possible to calculate.
Just out of curiosity, why would you or anybody else need/want a measurement of energy here? It's not a very useful metric for the use of this kind of equipment, which is why everything is rated in terms of force. Theoretically you could get a rough approximation of the energy by slapping a meter stick to the drop tower and using E = m*g*h where m is mass, g is 9.8 m/s^2 (gravity on earth) and h is the total distance traveled from the beginning to end. This would only work with really static lines though, like dyneema. If you wanted to find it with a more dynamic system you could do a simple pull test to find the spring constant k via hooks law (F = k*x) and then use E = 1/2*k*h^2. That said, your value for k will be very different when the system has knots that slip, deform, etc. and hooks law would still be a rough approximation at best.
My point is you *could* roughly calculate the energy and power with relative ease, but it doesn't give you any useful information so why would you bother? It's appropriate that force is the primary metric to consider here. Energy is kind of an abstract measurement for assessing safety in these kinds of systems, force is all we need to make well informed decisions. It's like wanting your car speedometer to measure energy; sure you can do it but it's kind of irrelevant as speed is a much more useful thing to know.
@@BridgetWirth A spring is poor model for textiles (cordage, webbing, rope, etc) in destructive pull tests: energy is dissipated in the frictional heating and melting of the weave, plastic deformation of the fibers, chemical bonds being stretched and broken, etc. Once a metal spring experiences plastic deformation, you can throw Hook out the window.
The human body is incapable of generating the same forces as a rigid mass, especially for shorter drops and less elastic/dissipative textiles, a rigid mass is a poor predictor. But, like you said, gpe is trivial to calculate, and it might be interesting to compare that to the Joules/meter that a textile can dissipate during failure.
@@BridgetWirth For example, we know that a 1m rope will survive the 700J of energy in a 1m fall. The complication I guess with doing the same exercise with dyneema, a larger portion of that 700J is going into the climber's kidneys and spine.
@@BridgetWirth Energy is a measure for how much of a fall it can hold on its own before it's fully extended (or breaks).
A shock absorber that can absorb 6kJ over 1.5m of distance before it is fully extended can hold an 80kg person that fell 6.14m (from start of the fall to the first point where the shock absorber is under tension), assuming there are no other shock absorbing parts in the system.
Hi! Maybe for the "not adjustable end" you could try a... Double bowline... I'm not sure how call it. I mean the same knot which is used by Stefano for example. Anyway, thanks for this one, I really enjoyed it
'bowline on a bite' is what I've always heard those called, the one where you start by tying an overhand on a bite and transform it into a bowline.
Thank you! What a great video!!
I kinda just want to use a screamer as a personal anchor now. Yikes!
Absolutely breaking my gear fear and placing it where it should be. On fall factor twos!
I use double Purcell Prusik (PP),
1 big loop with 2 PP at the ends girth hitch it to the harness, with big wirelock carabineer.
Find it super useful,
Apples to apples seems safe enough.
I've never done climbing, but I am a sailor & Tugboat operator, so I've done a lot with ropes. In construction and shipboard safety harnesses, they include an engineered shock absorber that is a replace after it dose its job tool . I'm sure it weighs more than the slings you are making, but you can count on the amount of shock absorption it will provide.
In climbing, a single use absorber is called a screamer.
They're not used very much at all because of the cost of replacement, bulk, and at we simply avoid taking any falls that generate enough force to need a screamer. They are used in ice climbing for marginally strong ice anchors, but on rock you'll pretty much never see them.
Something similar is used in Via Feratta sets.
Question: were your drop tests in 6 or 7mm? Indications are that if they were in 7mm, the impact forces would be less in 6mm.
I use a purcell as an edge restraint Or as a restraining device on an articulated work platform.
2:03 Figure 8 BFK version is definitely better! You can use the tail as a rappell extension if you tie a standard figure 8 follow through with it!
With the dyneema you tested near then end, with it slipping well below 1KN, we shouldn't even expect it to slow you down, only make you accelerate slightly less quickly. That slight drop in the rate of acceleration is completely counteracted though I would suspect from the additional travel distance of the fully extended prussik. Meaning it basically it is worse than nothing and you are taking a hard fall on static protection.
We’ve made Purcell prusiks out of 8mm dynamic half/twin rope with the thought that it will provide even lower forces in a fall. I’d be curious how that compares and if there’s anything we’re overlooking making that a bad idea.
Bluewater actually makes 6.5,7, and 8 mm dynamic cord advertised as for these.
Would be interested to see that cord tested as well
Nice video! I was hoping you'd try taking loops out of the pruzuk. Maybe if it was 2 on one side and 1 on the other, instead of 2 on both sides, it would slide more. Having the too loops above and the single loop below i would expect to slide easiest
After you video on cow's tails, I was wondering, "OK, but how does a Purcell-Prusik anchor do in similar conditions?" I had not gotten around to asking directly, but here you are, anyway, with a video on the Purcell-Prusik. As if you'd read my mind...
Background: I come from a world that is not generally populated with rope-climbing knowledge but nevertheless fall protection is of great interest: namely square-rigged sailing ships. The things we climb are intentionally designed to be climbed and, in general, falls are actually pretty rare. In the old days of wooden ships and iron men, there was no fall protection at all. If you fell, you fell. End of story. But as this world has moved on, over the course of the last 120 years, evolving from commercial shipping into sail training and historical interest, there is a greater emphasis on safety. Fall protection has taken a higher priority due to insurance and the desire of organizations not to damage their volunteers/employees. These organizations have, slowly, evolved various systems to protect (at least, in theory) their sailors. But in many ways, this world is still a long way away from the climbing world. A common way of thinking is that, as long as the gear doesn't break and you stop the fall, life is good. Climb down and have some tea. Not a lot of thought is given to shock loading or what a fall factor 2 can do to a human body if abruptly arrested. You would absolutely shudder if I told you what was being used for fall protection 20 years ago. We've evolved since then, and currently, in my organization, we are using a Purcell-Prusik as a personal anchor (we say "lanyard" because, well, it's nautical...). It's made 10mm dynamic line. I'm told that it was tested and deemed "plenty good enough" if one were to fall on it. And perhaps it may be, but I have always been thankful that I have never found myself putting the theory to the test.
It would be interesting to see some testing done on Via Ferrata Sets (which consist of two tethers with a zip-strip to reduce shock loading).
That search and rescue guy is a pretty cool guy ;)
I never intend to climb anything more difficult than a 15 foot ladder. However, I would not do anything with any sort of string, rope or line without checking your videos first. I have seen others do videos on splicing Dynemma and realized your videos are the only ones I trust. BTW, Dynamma is an interesting product. It is super strong, but has some interesting quirks that I discovered on your videos.
Could you also try other friction hitches? Would an autoblock be shock absorbing enough for a safe fall?
Did you clip the end of the daisy or shorten it? If you clipped the end it’s equivalent to testing the fully extended Purcell. A (correctly) shortened daisy seems more useful to test and might absorb better
Have you done testing on the multitude of friction hitches arborists use for ascent, descent, fliplines/ adjustable personal anchors?
Great tips 👍
I like the double fisherman, but i start it like you started the figure eight, and tie the fisherman around both ends, that way it makes an eye that will cinch down on the carabiner when weighted so it stays put better.
I’d be interested to see a Edelrid amarid sewn sling made into one of the prussel and tested.
"secure the victim" that sounds way more ominous than "secure the patient" 😂
Will you test some Via Ferrata kits as well? Curious about the results
hi, I was wandering... close to4:30min, is there any reason why not to do first the prusik and after the figure 8 knot? isn't it be easier to go through the pursik knot if we have the tail free?
thanks for the video, by the way :)
tying the Prusik that way (on your hand) one could tie a lopsided "directional" Prusik - making it easier to extend, and bite a little harder. ???
11:52 after doing the drop test on the prusik, were you able to move the... knot? up and down again or does it just fuse to the rest after stretching and pulling?
Can you also please test a Petzl Connect Adjust lanyard under the same sort of conditions? Drop test & slow pull to destruction.
Finally! Thanks so much!
The swinging thing skews the results. Your drop tower is cool, but maybe some stairs and a way to mske the falls straight. Great video!
If you get the chance to it might be fun to test the petzl adjust vario it would be interesting to see how strong it is compared to the regular petzl adjust with a sewn end
for the knots - how much would a hangmans knot reduce the ropes strength?
I wonder if you were to add a screamer to the system how it would affect the numbers?
It would i terresting to know how much shock is absorbed by the persobal anchor for Via Ferratas in comparison
Suggestion when you test the petzl adjust test the breaking strength if you just clip the metal and not the rope as well
Great work. Thanks.
So call me crazy, but the only application I've ever considered for the PP is for rope soling (on lead) a bolted route where finding a ground anchor (boulder, tree, good low crack) is not an option. The idea being: climb to the first bolt, clip a PP to it, then clip the end of the rope to the sliding end of the PP (having pre-connected other end of rope to my grigri on my belay loop). Crazy? Indeed. But potential advantages: (1) if you fall shortly above the 1st bolt, the PP should keep the fall force below factor 2 (but seeing the video, I'd keep the PP on 6mm or less to get more slippage and lower forces), and (2) once clipped into the 2nd bolt, the PP would add a little bit of dynamic quality for a fall (not much due to friction thru 'biners, but more is better in this case IMHO) and so that's good. I do loads of rope-solo leading and don't bother with a PP if I have a good ground anchor, as there's plenty of dynamic quality in the system once several meters of rope are out and the first piece has been placed, especially given that I'm not (and no one should) ever taking big whippers while rope soling... So I'd love to see the PP tested in this kind of application...
Can you test the Kong Slyde as well? :D
Try the same with one of those Edelrid aramid slings, 22kN rated and they work as a Purcell prusik, would be interesting to find out the numbers.
I wpuld be interested to see bluewater ropes' dynamic purcell prusik cord tested on the drop tower
So should you make it out of 5mm or thinner Nylon so that it slips sooner? If the breaking force is way high anyways.
i made my Prucell out of Edelrid Aramid cord sling. been working amazing for years. since the aramid is a lot stiffer its a lot easier to handle and adjust, but id love to know how it compares to nylon or dyneema that you tested here.
Is there an official name for the "figure of 8 bfk flemish sort of a knot"? It looks like a safe variation of the flat 8.
Also, why the two specific options for the bend. Wouldnt any critically safe bend be ok?
Hey, would You test via-ferrata kits eg. compare fall on dynamic rope vs kit with absorber. More interesting is how to carabiner lay on the steel line anchor, during the fall on vertical route, it makes the carabiner is cross loaded and side way loaded when hit the anchor point and the steel line is pre-tensioned high - I think this is the weakest point.
What about making a prusik with two "wraps" rather then 3? Would not it allow more slip, therefore absorbed better?
thanksalot for all that content 🌞