I'm a whitewater rescue instructor and your work is gold to me!!! There is too much myth around rope and you debunk them and help making the rope sports a safer place. Love from Montréal Alex
Hello, actually it is not a fair comparison. If you read the Treeclimber's Knotbook, you will read, that the klemheist needs one more wrap, than the prusik to perform in a similar way. The autoblock (machard) needs some more wraps to be able to show its advantage. You need a longer cord and you have to make as many wraps as possible, making sure that the connecting-knot is in top of the autoblock. Than it does not slip. My results of my own tests with 6 mm cord: klemheist and prusik: 950 kg, autoblock 2400 kg (!!). Thanks for your video. Dirk from germany
Adding here since I don't see this in the other comments. The Sterling Hollowblock is made from aramid fiber (hence the yellow color) and is much more heat resistant than common rope materials. This might matter in a friction hitch where things do get hot.
Am underrated comment for sure. I always worry about how hot my cord might get if I don’t put enough wraps on my auto block if it were to start slipping down the rope while I’m hands free!
personally i learned those three knots pretty early as i started mountain climbing, i use them as secondary safety for rappel and stuck with the prusik for purely practical reasons. prusik works both ways (which allows very comfortable details while getting in a rappel, like having it hold some slack in the rope for you), it stays on the rope even without a carabiner, and is vastly easier to get moving again after it locked tight.
I really like this channel. I work as an arborist and sherrill, which is a american dealer for arborist gear, did some tests several years ago. Their conclution was that for maximum friction the friction cord has to be 5 7ths of the climbing rope. Thanks for great entertainment.
What some may miss is the concept of fit for purpose. The Autoblock is fit for purpose when used below the device to as you say, "add friction" in an abseiling context. So in effect it doesn't need to hold all the weight, it merely needs to add enough friction so you stop if you let the Autoblock grab the rope to go hands free. Very comforting to me to see it slip and not break. As always though, test before you commit to any set up you use when abseiling or for that matter perform any transition when up in the air. Awesome set of tests. Will be using some of that data in future training sessions.
The only way I could see an importance to support all your weight would be a total brake failure of the rappelling device, chances are really low. Worse case you do not clip rope strand to your carabiner on the ATC and for sure you do not test the system before unclipping your landyard but at least you took time to do a perfect prussik before this operation. By the way if you clip to the carabiner only one strand of a double rope rappel, the prussik may not save you, I used to test this on the ground (prussik works great if it is moving on rope but it could fail if rope strands are moving in opposite direction, prussik can grab the strand locked in your ATC and the free strand simply move up without any resistance).
As a general note, when the ropes get wet, everything changes. The value of hollow block is that it takes higher temperatures compared to nylon. If it slips down the main rope, it will last longer than nylon will. Also, being small & sewn, with no large knot, you can attach it to a leg loop & have it be short enough to use as a third hand under a repel device that is attached directly to a belay loop
If you get knocked out, you roll upside down, your leg loop can ride up your leg and easily reach a rap device that is not extended on your belay loop.
Much better and safer to extend the rappel device and attach the autoblock to the belay loop. Not only is it a smoother rappel, and eliminates any risk off loosening your leg loop, but also that provides a fully redundant backup your rappel device. Even if somehow your rappel device became fully disconnected, your autoblock with any of these knots will hold your weight. Even if it somehow slips under body weight, it will slip slowly enough to prevent a catastrophic fall (at least if you keep your hands off of the hitch!)
The friction hitches are really used on arborism. But always on double rope system. If u want to use in 1 line u got to add an extra friction device. Most used are rope wrench from ISC and chicane from petzl. Anyway, the knots that u tested is not common used. If you want to try the blakes hitch, distel, michoacan will be something nice to see. I like your vids! thanks for doing its!
This has been a question in my head for more than 20 years. Your guys' channel officially wins the internet. Been watching a bunch of your videos. Subscribing. Thumbs Up
As a military mountaineer we are trained to use tubular webbing tied with a water knot and use that in the autoblock. I'd be curious to see the numbers on that combo.
Good to know I’ve been rapping on the weakest slippyest friction hitch this whole time! The thing is it works well when used for the purpose of backing up an ATC.
Yeah its not like your considering that your atc is gonna break. After all we belay people all the time on an atc or other devices without back up. So I agree I think the point is to be able to go hands free on an atc when rapping to deal with shit.
It's not about your atc breaking, but you setting it up wrong and have a redundancy if you accidentally, say, forgot to run the rope through the biner. It does not matter much if in this video the knot slipped, I'm sure my autoblock holds my weight, its a combination of ropes and diameters that will make most difference. I prefer smaller diameter cords because I feel like they block the most and need less wraps.
I would imagine maxing out at 300lbs of force is enough to hold the brake position on your atc when rappelling. That aside, comment above made me think though about the usefulness of the friction hitch as a backup if you accidentally failed to thread both ropes. Thanks for that @IacamiGevaerd
@@iacamigevaerd376 Honestly, if you’re adding redundancy just in case you forget to do something right, you have a problem. Cos what if you forget to do the redundancy right? You need to thread your belay plate right, and redundantly make sure you have done it right lol as many times as it takes to be sure it’s right, and not go until you’re sure it’s right. Not do other things in case you do it wrong,
Great video! I would have loved to see the VT prussik bluewater product included here because the valdotain tresse hitch is releasable under load, you can rig onto and descend a weighted rope, and the technora sheath will not melt like nylon or polyester. My guess is that the hitch will slip under a high enough load but adding wraps very effectively increases friction in my experience using it on longer rappels here in Utah.
There's no rule of only 3 wraps, that's just a starting point, when the diameter of the cord is closer to the size of the rope you need to have more wraps to create more friction. For rescue rigging a 8mm prusik is common and requires many more wraps against a single rope. The test of using 10.5mm prusik around a single 10.5mm rope will work just might need 15-20 wraps or more, haven't tried to know the exact number. Ryan should be testing how many wraps does it take to hold to be more accurate here. Also, autoblock is used with a belay device in the system, and more common around 2 ropes at the same time where there's a lot more surface area to create friction, and is more of a use case for the Hollowblock. That said, an autoblock is not intended to be directly loaded as an ascending device or progress capture. Hollowblock also comes in a longer length, probably needed for achieving more wraps when using on a single rope with friction hitches. Overall should revise the test for number of wraps needed for diameter differences to achieve the same slipping strength, number of wraps needed to achieve MBS, and comparing application of different friction hitches when using the same materials. Not trying to give Ryan more work, but think the major point of number of wraps was missed...
Prusik still rules.. my camping and hammock goto. Love your channels tempo and tests (have answered most of my knot and carabiner questions I had over the over the years)
Yep, VT is the go to for sure, very efficient when combined to a pulley for assending. I got it on my lanyard even in industry work for moving around on beams. Much better than mechanical blockers/descenders
@@vlravn2358 for our work positioning line I use a vt and a pulley. Also on my secondary I put both legs of the VT through a metal ring before cliping in to make it even smoother again!
Great video. If you ever want to stray more out of the climbing scene (similar to your recent video on rope access) and are interested in friction hitch based life support systems you should take a look at some of the equipment used by arborists. The stitch hitch, hitch hiker, rope wrench, climbing doubled rope with various hitches, etc.
I have a hollow block as a third hand (French hitch) as part of my abseiling kit. It’s comfortable to use, glides smoothly along the rope for Abseiling and can be used on different diameter ropes for different activities. the benefit of it is it’s ability to hold well on a large variety of rope Diameters without the need to carry a different diameter prusik cords. That said it is a pain in the backside to use for ascending a rope using it as a prusik (the knot becomes hard to loosen). Great videos I be learnt loads from your channel and the knowledge gain gives me confidence in the equipment Keep it up mate 👍
Someone might have already mentioned this, but I use accessory cord for my prusiks while climbing and use the hollow block for kayaking. I find that the hollow block bites into ropes better when everything is soaking wet and I'm setting up Z-drags and other mechanical advantage systems in the water!
Amazing videos ;) I'd love to see tests from arborist blocking knots, I left my prussik knots for using the distel hitch, compact and in line with the rope instead of offset
Here are some links to the Purcell Prusik Purcell Prusik - Google Search Purcell Prusik | How to Tie the Purcell Prusik Loop - RUclips Climbing tips: How to tie a Purcell-Prusik loop (Personal anchor system) - RUclips Everything About the Purcell Prusik for Climbers - RUclips How to tie series: Purcell Prusik - RUclips Purcell Prusik Loop | How to tie a Purcell Prusik Loop using Step-by-Step Animations | Animated Knots by Grog
If this gets tested I'd like to see how a tautline hitch backed up with a fisherman's compares, because its the same concept. Adjustable sliding friction hitch.
Like you said, the closer in diameter your accessory cord to climbing rope are, so I would imagine the more likely they are to slip or fail to create a nylon saw, especially in autoblocks, as they are notorious for this for the same reason we see them consistently slip even with extra wraps. I'm intrigued to see how a Bachmann holds up to the RBS and others! Best, Isaac Also, I have a hollowblock, but it still has yet to inspire confidence, this video coaxes me to leave it at home from now on...
It probably would not affect the breaking strength because that is a material property of the cord used to tie the friction hitch. However, a lot of the tests where the hitch slipped might have not slipped because of the increased contact area between the cord and the rope.
@@HowNOT2 yes part 2 is definitely needed. Would also be interesting to see a presewn prusik vs tied, but maybe too similar to a hollowblock to be worth testing?
yes please, I always use a 6mm prusik wrapped twice around two strands of usually 9.8 ish rope. I see a lot of people using 5mm too and im just wondering if going so thin it is getting possible to "cut" the larger ropes.
Material also matters a ton! I recently switched from nylon to polyester in 6mm (PMI to Maxim brands if that matters) and the polyester is much more supple and grippy in the same length and number of wraps. I feel like polyester accessory cord might be a real win. Something else to think about!
Material makes sense for sure. I'm wondering about Amsteel loops for friction hitches. I can't quite get over how 'slippery' amsteel seems, but they bite pretty well when I test them and I like how light they are (as well as having no knot to worry about)
With regards to the Sterling Hollow block product, while I've always used a 5mm cord and been fine, the sterling product just wraps up easier and is much less intrusive on the harness.
The advantage of hollowblock or VT prusik is that they are more RELIABLE when being used as a backup. Accessory cord does not = a good prusik. Stiffness of the cord makes them very unreliable unless they're old and fluff on an old and fluffy rope. With a designed for purpose prusik once it's wrapped the chance if it actually wanting to bite the rope is significantly better than with some random cord. The hollowblock will loose strength very quickly as it has no core, but unless it's obviously not fit for purpose it will still be strong enough to be used as a french prusik/autoblock below a descender. This is why I recommend built for purpose backups like a hollowblock or VT prusik for going down and then regular old accessory cord prusiks or slings for ascending. (All this is ehat I've observed in a decade of playing with ropes and instructing various courses)
i do most of climbing in trees. i use prusiks most the time but instead of the 3mm less rule i use 50% for biting and 70% for sliding (for instance if i were using a 10mm rope for holding me in place id prolly be using a 5 mm but if i were ascending id use a 6.5 or 7 cause it easier to break to push up the rope). the sheath/mantle also matters quite a bit based on what im trying to do and the rope characteristics, dyneema prusiks slide quite a bit more than polyester. really appreciative for your videos not all of us can have such a pretty machine.
This vid was particularly interesting as an arborist. We use friction hitches as life support in the form of eye to eye spliced or sewn. 8mm - 10mm Totally off your radar but I would love to see how one of our 8mm (smallest) eye to eyes holds up in your slack snap rig.
Peter and Conrad.. Since you are on static lines and constantly tending slack, break testing your hitch chords is IMO irrelevant. A 8 ft fall would never happen in arborist work, and even if it did (fire that employee immediately) you are looking at 1-2kn max, prob closer to 1. For 6"- 18 arborist 'falls' on static line you are safe, safe, safe
I usually use on of Edelrid's Aramid Cord Slings to make my friction hitch, not sure if they're selling them in the US. I really love these things, they've practically replaced my dyneema slings for pretty much all purposes (lanyard, setting up a belay on multipitch, ... ) apart from in extendable draws, and I also prefer them to using accessory cord. Thing is, having a pre-tied prussic sling from accessory cord is a piece of equipment that I can't really use for anything else while I always have a few of the aramid slings on me anyway. I always prefer multi-purpose gear, plus it feels good to know that it's rated for full strength :) for the other purposes, where I use it instead of dyneema slings, it also feels more reassuring, having a sheath and all. It is heavier though.
I use the 22Kn Edelrid ones to. And I disconnected my belay device and keep the Prussik on loads of time for different reasons during rappels. With the idea it’s full strength 22kn armide core rope. Now I’m curious what there strength is on a rope in a prusik knot 😅.
my personal favourite way to abseil/ rappel is using a Hydrabot on a short sling to raise it up. this then gives me room to put a hollow block wrapped 3-4 times as an autoblock (french prusik). this gives me the safety of a self-belay while being able to abseil as fast as I want (hollow block is heatproof) and 1 handed for technical sections. having the belay below your repel device means it is so much easier to get going again as it doesn't have your whole body weight on it. the auto block is also super quick to tie and gives heaps of control.
Many years ago I used to solo climb, S roping (belay point at bottom, tie in with enough rope to reach a gear point, retie to next point, abseil back down when I run out of rope (clearing gear), then climb back up rope). Longest climbs were 3 pitcvhes. No ascender, so I used a couple of prussik loops. They worked, but it was very slow and hard work! Tried Kleimheist, but it was very hard to keep the knot 'dressed' as I slid it back up the rope. Prussik was easy to keep neat.
This test would be nice on the test tower you’re building. To see the effect of the slippage. I use it to backup atc, to switch between shunt and atc and in case of a rappel from one bolt mid route.
I'm not sure whether this is 100% accurate, but I was recently talking to an IFMGA guide about different material strengths, and thought I'd share an idea on why the hollow block may have failed dramatically below it's MBS, beyond just the fact that it is old and well used. I believe this is because technora has a fairly low "yield point." Given that we use this piece of equipment to add friction to rappels, and as a rope grab in various other scenarios, this point is not hard to reach, and as such the MBS of our Hollowblock will likely decrease more quickly than climbing ropes, slings, quickdraws, and other soft goods - even of similar age / with similar wear. That said, it will likely remain strong enough for it's primary application as a friction hitch, but if you run out of quickdraws and want to extend a piece of gear... don't whip on it! ;) Like you said lots of variables, but interesting to think about as I personally do use a hollowblock regularly.
It would be interesting to see friction hitches on steel ropes (for zip lines, via ferrata bridges, etc). At work we sometimes use them if we forget the tensioner clamps and they always slip with slings.
I know this is old but would love to see the Hedden knot tested like this. It’s like the klemheist pulled in the “wrong” direction (or tied “upside down”). Or similar to the RBS here but without the carabiner. Supposedly much stronger holding power than klemheist (though I was taught otherwise at my mountaineering club), definitely easier to dress.
Some thoughts: - I was taught that 4 wraps was the minimum for an autoblock or klemheist. Based on your results I definitely agree and would not ever rely on 3 wraps. - Anecdotally I've always felt that the prusik knot was the most secure friction hitch. The autoblock and klemheist trade gripping power for ease of unlocking and sliding. - I'd be interested to know what the history of that hollowblock was. The Sterling hollowblock is made from aramid fibers, which are much more susceptible to UV degradation than any of the other common synthetic fibers.
I was taught 4 for autoblock too. However it doesn't have to be very strong if itks used for rappelling on the leg loop as a block since there is a multiplier through the ATC/rappelling device. How hard does your hand grip the rope ?
The number of wraps totally depends on the application. For an autoblock as a "third hand" to backup a rappel, you just want it to add friction to the system. You want it to slip, but still have enough friction to engage your ATC to stop the rappel. So the number of wraps depends on the diameter of the loop and the diameter of the rope. There is no 'one size fits all'. For newer skinny ropes with dry treatment I'd agree 4 wraps minimum. For older well worn, fuzzy and fatter ropes 3 is usually sufficient.
Outstanding content - this must be the best use of RUclips so far. Do more like this - test stuff we all do all the time! (Would also be interested in klemheist vs. viking [klemheist upside-down], but probably would enjoy your next idea just as much.)
I tried a prusik on a 60mm smooth aluminum tube using a 10mm wide nylon webbing loop, it grabbed very well. (We were hauling a 6 meter long thick wall antenna tube up a pole, and needed something to hold it when we weren’t lifting it or trying to feed it through a clamp, not supporting a person, nobody below it if it fell etc etc).
I use a Prusik as a back up when i am backing of a route because i can't reach the ankor or when i don't trust the anchor. I connect my harnes with a carabiner and a prusik to the side of the rope which goes to the belayer. The idea is that if the ancor or single point from which i am descending fails the prusik will prevent me from falling all the way down. Still a big fall if the next quickdraw is far bellow me at the time of the anchor failing but better than no back up at all. I wonder what would happen if i fall into my prusik backup.... So this video is very intresting to me! But i'm not sure if it will behave differently if you fall into it as opposed to slowly increasing tension like you did with the machine. Very good video anyway!
If you absolutely have to use the same diameter you can tie a Blake's hitch, works like a klemheist ie in just one direction. Using friction hitches as life support is quite standard in tree work but we use 8mm minimum cord.
I think auto bloc definitely works better for double ropes rather than single. Ive seen it slip in single ropes where a klemheist was super good enough. Thanks for the science maaaaaaaan.
I like that you tried those hitches with the 10.5mm just to be thorough. Would be interesting to see how a blake's hitch would stand up to the slacksnap machine
I use an autoblock when rappelling regularly, and the one thing I've notices is that the knot doesn't bite unless it is shock loaded. It'll slip all day until you give it a good hard jerk. Maybe some day you can give this another try but instead of pulling straight away with the jack, you give the knot a sharp tug first so it can bite.
There is another big part to this that seems to be overlooked in the video, and that is the material science side of things. I would agree that for a friction hitch to work properly on your nylon / polyester ropes, you need a smaller diameter. However when you switched to the Sterling autoblock, that is technora. Technora interacts with nylon in a completely different way. Additionally, (not sure if you tested it or not) but the Klemheist or Multi wrap Hedon is a way better hitch when using that Sterling kit; due to the shape of it. In my line of work an instructor we typically use only technora - technora based kit; and we very regularly use 8mm VT prussiks on 7 or even 6mm technora lines. My point being that when using different materials, or intermixing, you will have widely different results. I'd like to see you test dynema slings and autoblocks on technora lines. I think you'll be surprised in the holding power (and the fact that you don't need dissimilar sized lines) :D Keep up the great work, you guys are an amazing resource!
One of the perks of the hollow block is that its Technora (similar to Kevlar) instead of nylon, which has a substantially higher melting temperature. This makes it less likely to weld. For rapping with a back up, the kevlar will handle the heat generated better and won't risk degrading the material as much, especially on long, fast, free-hanging raps. Also, given the fiber's chemical resistance, I suspect it holds up to the elements a bit better than nylon over time. Plus, I just like having a sewn connection instead of a bulky knot, but that's just preference. I have also found it to grab much better on the ropes I use. I suspect the condition of the rope sheath influences friction a ton, and I wonder if you were using the same section of rope for all your tests. If so, maybe the repeated heating and rubbing smoothed it out a bit and made it more slippery?
Always good to see other tree guys on this, I've tried getting other guys to watch the videos! Some stuff isn't relevant but knowing about loading and strengths of stuff is essential.i think!
@@kaimcguire5086 no just tree work! I have looked at rock climbing. I feel like tree work to rock climbing wouldn't transfer super well, but rock to tree would be great as the strength and stamina from that would help a lot!!
I think since most of the strength comes from the core you'd need to slip quite are while to wear through the mantel and significantly reduce the strength.
I mostly use the klemheist, with only two wraps, and I find that works perfectly for a smooth rappel. If I need a safety line while rigging a top rope, I use a prussik.
I used a hollow block for years, or worked well, but eventually I replaced it with a sewn piece of kernmantle cord (either 5 or 6mm, I'm not sure). Kernmantle construction gives me more piece of mind, because as long as the sheath is intact, the core should be completely undamaged and also largely protected from dirt and abrasion. I mostly use the klemheist, with only two wraps, and I find that works perfectly for a smooth rappel. If I need a safety line while rigging a top rope, I use a prussik.
Long repels could burn through your 5 or 6 mm cord auto block knot, that's why the hollow block is made from Technora material. It has higher melting temperature so it won't weld itself to the rope, also used for firemen excape ropes they melt somewhere around 1100ﾟ I believe.
Can you test a few of these using static rope? For rappelling, ascending, or a backup line while climbing I use a static rope. When the dynamic rope stretches the diameter decreases and the diameter of the main rope approaches the diameter of the friction hitch. Similar to the test with the 10mm on 10mm friction hitch. Thanks!! Really enjoy your channel!!
I bootied a hollow block on a classic multi at City of Rocks, been using it since then because it was brand new. On my mammut rope I have to throw an extra wrap on my auto block because they're both pretty silky, its not a problem on our maxim. I personally would never pay 20-whatever dollars for one though. My thought would be to test the knots with 2 strands of rope inside like most people rap. Thanks for the video!
You have to test friction hitches on the drop tower once it‘s completed. Different results there. I participated in some drop tests at a course at the Petzl Technical Institute with a dummy. We simulated a fall from a lege with some slack between the prusik and the anchor. It cut the mantle sometimes but the fall was stoppe after 30cm to 1m by the prusik.
Another tree climber here. I'd also be curious to see an eye to eye with a valdotain tresse (with 5 and 6 wraps) and distel hitch. The valdotain should slip but I'd love to know at what point. Feel like the distel would be more likely to break🤷🏿♂️
I use a 6mm cord and I mostly use autoblock with 3 or 4 wraps (if I'm the first person rappelling and knowing there is some snag on the rope, I use 4 wraps, otherwise, 3 wraps) for rappelling, as long as it is not completely vertical or negative wall, on these cases I use climb heist. To ascend I use prussik always
I use 6 mm klemheists quite a lot in anchor building and in rappelling as well. I took a different conclusion, seems like those are pretty darn good and I still feel comfy with it.
From South Africa here. In the guiding industry we use 4-5 wraps for the French Prussik or what you’re calling auto lock. The French Prussik is releasable under load while the clemheist bites like a possessed pit bull. Also use 4-5 wraps for that. We avoid using three wraps in anticipation that some unravelling occurs.
If u use a tied prusik u can tie in a Michoacon. It has been the most stable going up & down the climbing rope. A lot of the time I use an eye to eye prusik that has small factory sewn eyes which helps from side loading the carabiner.
I know this is an old video and my comment isn't particularly climbing related, however I use prusiks camping on my ridgeline to secure my tarps to (I use a prusik trough the tarp tieout with a toggle or just a random stick to adjust/hold tension on the tarp) my ridgeline is 550 paracord, for a long time I used 550 cord for the prusiks as well and they hold just fine even in 50km/hr or stronger winds (i have since switched to 325 cord or #36 bank line for the prusiks just for a smaller packing size mostly. I do get how a thinner rope grabs better but in some materials a like sized rope seems to grab prety well still without sliding so easily. And as for the one rope cutting the other, I know as a "survival tip" that you can cut (see through) a thicker rope with a thinner one prety easily in a pinch if you dont have a knife but cutting a rope with a thicker or same sized rope doesn't work well of at all.
I was taught in France, that Prussik, autoblock and kleimheist knot were to be used when you have 2 strands of rope like when rappeling. On a single strand, they tend to slip. On a single strand, the knots i was shown were valdotain tresse, distel or schwabisch knot. Which are used in tree climbing.
I use a hollowblock on one strand (10-11mm static) as a third hand, never seen a slip, this is of course of very low loads, nothing even getting close to 1kN, but it holds and doesn't slip at all....
In arboriculture, I use a knot called a BLAKE. It's not only a friction knot, it's the entire rappel system. And it's made using the other end of the rope. So, you guessed it, using same diameter rope! I would not hesitate to use it in a situation where there nothing left but the rope itself
Although for ascending or descending (lifting or lowering), the prussik and klemheist the turns are not even to either side so that it rides easier in one direction and theoretically locked stronger the other. Haven’t really used them in the “standard form”. Also these were developed in times that ropes were presumably natural fibers, which is passé now - but having the ropes in more contrasting materials may give altogether different results?
Regarding 9:07 , if you were needing to use similar to equal diameter cord to form a hitch, a blakes hitch would be a more appropriate option. This certainly derivatives from the channel topic, as this is primarily used by arborists. However, it could be useful to know for climbers as well, as this allows you to create a hitch that allows you to both ascend & descend a rope using only the rope itself, without cutting a section off. Certainly, there is some emergency usage potential there.
I tried using a hollow block the other day as a prusik to ascend a static rope (with my gri gri). It did not work at all! Any time I would weight the damn thing to pull slack through my gri gri, it would just slip! Had to switch it out and use a sling instead, which worked like a charm
Use prusik for 3rd hand repelling. Found that klemheist is better for ascending than a prusik on lost arrow spire . When weighted the prusik is tough to slide up. Also you can put the klemheist around a carbineer to give a handle to your ascender.
I realize that the Blake’s hitch or the taut line hitch are only used in tree work, but they’re commonly used with either the other end of the rope you’re climbing, or a split tail system with a separate shorty piece of rope that is the same diameter as your climbing rope. I’d be interested to see what those break/break loose at.
@@eyescreamcake Perhaps the type of rope requires more turns or to dress it correctly, it is a knot used for that specific purpose, a friction knot that retains even with rope of the exact same size, that is why it is in the safety catalog
I'm an arborist I too use the Blake's hitch all on the same rope I use the tail of my rope to tie it on a mrs system I have found that it will slip on kernmantle ropes but holds tight on 16 and 24 strand ropes.
I’ll have to try the kleimheist. Although when backing up a rappel you should never get extreme forces, I’ve never felt secure using an autoblock and this video validates that. I stick with prussik.
ive used 5mm prusiks on 10mm rope for years even to the point of rappelling off one single prusik single rope no backup. its scary (and stupid I know) looking at dental floss holding onto your life but under static load that stuff is damn strong. Climbing rope technology is absolutely amazing.
I'm a member of a regional technical rescue team. We use 9mm prussics on NFPA G 1/2" static rope for almost every thing. Tandem prussic belays, progress capture, quick adjustment for anchors, anchor tie backs, adjustable fall protection, accending, holding edge pro in place, etc.
Would love to see the bachman’s knot/Prussik tested. It’s where you put the spine of a carabiner to the climbing rope and then wrap the Prussik cord around the rope and spine and then clip the rope into you harness or whatever. Normally used for ascending
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I'm a whitewater rescue instructor and your work is gold to me!!!
There is too much myth around rope and you debunk them and help making the rope sports a safer place.
Love from Montréal
Alex
Hello, actually it is not a fair comparison. If you read the Treeclimber's Knotbook, you will read, that the klemheist needs one more wrap, than the prusik to perform in a similar way. The autoblock (machard) needs some more wraps to be able to show its advantage. You need a longer cord and you have to make as many wraps as possible, making sure that the connecting-knot is in top of the autoblock. Than it does not slip. My results of my own tests with 6 mm cord: klemheist and prusik: 950 kg, autoblock 2400 kg (!!). Thanks for your video. Dirk from germany
Adding here since I don't see this in the other comments. The Sterling Hollowblock is made from aramid fiber (hence the yellow color) and is much more heat resistant than common rope materials. This might matter in a friction hitch where things do get hot.
Am underrated comment for sure. I always worry about how hot my cord might get if I don’t put enough wraps on my auto block if it were to start slipping down the rope while I’m hands free!
Particularly good for multi pitch climbing with lots of long raps (so I hear). +1 for Aramid
personally i learned those three knots pretty early as i started mountain climbing, i use them as secondary safety for rappel and stuck with the prusik for purely practical reasons. prusik works both ways (which allows very comfortable details while getting in a rappel, like having it hold some slack in the rope for you), it stays on the rope even without a carabiner, and is vastly easier to get moving again after it locked tight.
I really like this channel. I work as an arborist and sherrill, which is a american dealer for arborist gear, did some tests several years ago. Their conclution was that for maximum friction the friction cord has to be 5 7ths of the climbing rope. Thanks for great entertainment.
What some may miss is the concept of fit for purpose. The Autoblock is fit for purpose when used below the device to as you say, "add friction" in an abseiling context. So in effect it doesn't need to hold all the weight, it merely needs to add enough friction so you stop if you let the Autoblock grab the rope to go hands free. Very comforting to me to see it slip and not break. As always though, test before you commit to any set up you use when abseiling or for that matter perform any transition when up in the air. Awesome set of tests. Will be using some of that data in future training sessions.
The only way I could see an importance to support all your weight would be a total brake failure of the rappelling device, chances are really low. Worse case you do not clip rope strand to your carabiner on the ATC and for sure you do not test the system before unclipping your landyard but at least you took time to do a perfect prussik before this operation. By the way if you clip to the carabiner only one strand of a double rope rappel, the prussik may not save you, I used to test this on the ground (prussik works great if it is moving on rope but it could fail if rope strands are moving in opposite direction, prussik can grab the strand locked in your ATC and the free strand simply move up without any resistance).
As a general note, when the ropes get wet, everything changes. The value of hollow block is that it takes higher temperatures compared to nylon. If it slips down the main rope, it will last longer than nylon will. Also, being small & sewn, with no large knot, you can attach it to a leg loop & have it be short enough to use as a third hand under a repel device that is attached directly to a belay loop
If you get knocked out, you roll upside down, your leg loop can ride up your leg and easily reach a rap device that is not extended on your belay loop.
Thats so not recommended these days ( off the leg loop).
Much better and safer to extend the rappel device and attach the autoblock to the belay loop.
Not only is it a smoother rappel, and eliminates any risk off loosening your leg loop, but also that provides a fully redundant backup your rappel device. Even if somehow your rappel device became fully disconnected, your autoblock with any of these knots will hold your weight.
Even if it somehow slips under body weight, it will slip slowly enough to prevent a catastrophic fall (at least if you keep your hands off of the hitch!)
The friction hitches are really used on arborism. But always on double rope system. If u want to use in 1 line u got to add an extra friction device. Most used are rope wrench from ISC and chicane from petzl. Anyway, the knots that u tested is not common used. If you want to try the blakes hitch, distel, michoacan will be something nice to see. I like your vids! thanks for doing its!
This has been a question in my head for more than 20 years. Your guys' channel officially wins the internet. Been watching a bunch of your videos. Subscribing.
Thumbs Up
As a military mountaineer we are trained to use tubular webbing tied with a water knot and use that in the autoblock. I'd be curious to see the numbers on that combo.
Good to know I’ve been rapping on the weakest slippyest friction hitch this whole time! The thing is it works well when used for the purpose of backing up an ATC.
Yeah its not like your considering that your atc is gonna break. After all we belay people all the time on an atc or other devices without back up. So I agree I think the point is to be able to go hands free on an atc when rapping to deal with shit.
It's not about your atc breaking, but you setting it up wrong and have a redundancy if you accidentally, say, forgot to run the rope through the biner.
It does not matter much if in this video the knot slipped, I'm sure my autoblock holds my weight, its a combination of ropes and diameters that will make most difference. I prefer smaller diameter cords because I feel like they block the most and need less wraps.
I would imagine maxing out at 300lbs of force is enough to hold the brake position on your atc when rappelling.
That aside, comment above made me think though about the usefulness of the friction hitch as a backup if you accidentally failed to thread both ropes. Thanks for that @IacamiGevaerd
Well, we all know how crazy rappers are. They are always in the news 🤣
@@iacamigevaerd376 Honestly, if you’re adding redundancy just in case you forget to do something right, you have a problem. Cos what if you forget to do the redundancy right?
You need to thread your belay plate right, and redundantly make sure you have done it right lol as many times as it takes to be sure it’s right, and not go until you’re sure it’s right. Not do other things in case you do it wrong,
Great video! I would have loved to see the VT prussik bluewater product included here because the valdotain tresse hitch is releasable under load, you can rig onto and descend a weighted rope, and the technora sheath will not melt like nylon or polyester. My guess is that the hitch will slip under a high enough load but adding wraps very effectively increases friction in my experience using it on longer rappels here in Utah.
ruclips.net/video/szd5upswbVQ/видео.html Tu duh
Rad. People been asking me this for ages. Thanks lads
There's no rule of only 3 wraps, that's just a starting point, when the diameter of the cord is closer to the size of the rope you need to have more wraps to create more friction. For rescue rigging a 8mm prusik is common and requires many more wraps against a single rope. The test of using 10.5mm prusik around a single 10.5mm rope will work just might need 15-20 wraps or more, haven't tried to know the exact number. Ryan should be testing how many wraps does it take to hold to be more accurate here. Also, autoblock is used with a belay device in the system, and more common around 2 ropes at the same time where there's a lot more surface area to create friction, and is more of a use case for the Hollowblock. That said, an autoblock is not intended to be directly loaded as an ascending device or progress capture. Hollowblock also comes in a longer length, probably needed for achieving more wraps when using on a single rope with friction hitches.
Overall should revise the test for number of wraps needed for diameter differences to achieve the same slipping strength, number of wraps needed to achieve MBS, and comparing application of different friction hitches when using the same materials. Not trying to give Ryan more work, but think the major point of number of wraps was missed...
Prusik still rules.. my camping and hammock goto.
Love your channels tempo and tests (have answered most of my knot and carabiner questions I had over the over the years)
I use a Valdotain Tresse for ascending rope. I prefer it over mechanical ascenders!
It even works for ascending ? I thought it was a blocking knot I’m gonna try it it’s better than To have to carry multiple ascender
We use it in tree work a lot. I use it as a secondary friction knot, as I use a Petzl Zig Zag as a primary (which I do prefer)
@@zackbroad4293 exactly, VT is my favourite
Yep, VT is the go to for sure, very efficient when combined to a pulley for assending. I got it on my lanyard even in industry work for moving around on beams. Much better than mechanical blockers/descenders
@@vlravn2358 for our work positioning line I use a vt and a pulley. Also on my secondary I put both legs of the VT through a metal ring before cliping in to make it even smoother again!
Ryan: Prusik knots don’t work when they’re the same diameter as the rope
Blake’s Hitch: Am I a joke to you
If a knot fails to stop you hitting a hard surface it's failed.
Yeah with the appropriate type of rope it works, but with the dynamic climbing ropes it does not :/
@@magnetohidrodinamika hmm, I guess it varies rope to rope. I've definitely gotten it to work with a 9.8mm climbing rope before 🤷♀️
@@magnetohidrodinamika it works best with a dynamic climbing line. You got it backwards. Static it won't work well
@@jhuntley575 works fine on 11mm static line, though i usually run 10mm knotted loops as prusik. - arborist, not dead.
Thank you how not to highline team. I've been waiting for this break test for a while. Keep up the good work.
Great video. If you ever want to stray more out of the climbing scene (similar to your recent video on rope access) and are interested in friction hitch based life support systems you should take a look at some of the equipment used by arborists. The stitch hitch, hitch hiker, rope wrench, climbing doubled rope with various hitches, etc.
I have a hollow block as a third hand (French hitch) as part of my abseiling kit. It’s comfortable to use, glides smoothly along the rope for Abseiling and can be used on different diameter ropes for different activities.
the benefit of it is it’s ability to hold well on a large variety of rope Diameters without the need to carry a different diameter prusik cords.
That said it is a pain in the backside to use for ascending a rope using it as a prusik (the knot becomes hard to loosen).
Great videos I be learnt loads from your channel and the knowledge gain gives me confidence in the equipment Keep it up mate 👍
Finally, i was searching so long for a video on a prusic break test 👍
Someone might have already mentioned this, but I use accessory cord for my prusiks while climbing and use the hollow block for kayaking. I find that the hollow block bites into ropes better when everything is soaking wet and I'm setting up Z-drags and other mechanical advantage systems in the water!
Please test the Purcell Prusik, it's commonly used as an adjustable personal anchor system usually from 6mm cord and up
Thank you for the content !!
Amazing videos ;) I'd love to see tests from arborist blocking knots, I left my prussik knots for using the distel hitch, compact and in line with the rope instead of offset
Purcell Prusik
Here are some links to the Purcell Prusik
Purcell Prusik - Google Search
Purcell Prusik | How to Tie the Purcell Prusik Loop - RUclips
Climbing tips: How to tie a Purcell-Prusik loop (Personal anchor system) - RUclips
Everything About the Purcell Prusik for Climbers - RUclips
How to tie series: Purcell Prusik - RUclips
Purcell Prusik Loop | How to tie a Purcell Prusik Loop using Step-by-Step Animations | Animated Knots by Grog
If this gets tested I'd like to see how a tautline hitch backed up with a fisherman's compares, because its the same concept. Adjustable sliding friction hitch.
Like you said, the closer in diameter your accessory cord to climbing rope are, so I would imagine the more likely they are to slip or fail to create a nylon saw, especially in autoblocks, as they are notorious for this for the same reason we see them consistently slip even with extra wraps.
I'm intrigued to see how a Bachmann holds up to the RBS and others!
Best,
Isaac
Also, I have a hollowblock, but it still has yet to inspire confidence, this video coaxes me to leave it at home from now on...
Not longer than two days ago I was wondering about prussiks and thought of you guys! Awesome!
in a lot of atc repells, you are wrapping 2 rope strands instead of one, I am curious if that affects breaking strength
It probably would not affect the breaking strength because that is a material property of the cord used to tie the friction hitch. However, a lot of the tests where the hitch slipped might have not slipped because of the increased contact area between the cord and the rope.
we could chase that rabbit trail
@@feelinghealingfrequences7179 dont kill this. Please, double ropes friction hitches tests!!yaaaay
@@HowNOT2 yes part 2 is definitely needed. Would also be interesting to see a presewn prusik vs tied, but maybe too similar to a hollowblock to be worth testing?
yes please, I always use a 6mm prusik wrapped twice around two strands of usually 9.8 ish rope. I see a lot of people using 5mm too and im just wondering if going so thin it is getting possible to "cut" the larger ropes.
Material also matters a ton! I recently switched from nylon to polyester in 6mm (PMI to Maxim brands if that matters) and the polyester is much more supple and grippy in the same length and number of wraps. I feel like polyester accessory cord might be a real win. Something else to think about!
Material makes sense for sure. I'm wondering about Amsteel loops for friction hitches. I can't quite get over how 'slippery' amsteel seems, but they bite pretty well when I test them and I like how light they are (as well as having no knot to worry about)
@@muppetsfromspace be careful using dyneema for friction hitches, as it has a very low melting point, and like you said, is very slippery.
With regards to the Sterling Hollow block product, while I've always used a 5mm cord and been fine, the sterling product just wraps up easier and is much less intrusive on the harness.
The advantage of hollowblock or VT prusik is that they are more RELIABLE when being used as a backup.
Accessory cord does not = a good prusik. Stiffness of the cord makes them very unreliable unless they're old and fluff on an old and fluffy rope.
With a designed for purpose prusik once it's wrapped the chance if it actually wanting to bite the rope is significantly better than with some random cord.
The hollowblock will loose strength very quickly as it has no core, but unless it's obviously not fit for purpose it will still be strong enough to be used as a french prusik/autoblock below a descender.
This is why I recommend built for purpose backups like a hollowblock or VT prusik for going down and then regular old accessory cord prusiks or slings for ascending.
(All this is ehat I've observed in a decade of playing with ropes and instructing various courses)
i do most of climbing in trees. i use prusiks most the time but instead of the 3mm less rule i use 50% for biting and 70% for sliding (for instance if i were using a 10mm rope for holding me in place id prolly be using a 5 mm but if i were ascending id use a 6.5 or 7 cause it easier to break to push up the rope). the sheath/mantle also matters quite a bit based on what im trying to do and the rope characteristics, dyneema prusiks slide quite a bit more than polyester. really appreciative for your videos not all of us can have such a pretty machine.
This vid was particularly interesting as an arborist. We use friction hitches as life support in the form of eye to eye spliced or sewn. 8mm - 10mm
Totally off your radar but I would love to see how one of our 8mm (smallest) eye to eyes holds up in your slack snap rig.
Love to see that too, but not on alpine rope but on a working line to get the best picture.
+1 I would like to see it aswell. 11.5 mm static rope would be nice to see it on. And maybe on the Valdotain and distel friction hitches
Peter and Conrad..
Since you are on static lines and constantly tending slack, break testing your hitch chords is IMO irrelevant. A 8 ft fall would never happen in arborist work, and even if it did (fire that employee immediately) you are looking at 1-2kn max, prob closer to 1.
For 6"- 18 arborist 'falls' on static line you are safe, safe, safe
I usually use on of Edelrid's Aramid Cord Slings to make my friction hitch, not sure if they're selling them in the US. I really love these things, they've practically replaced my dyneema slings for pretty much all purposes (lanyard, setting up a belay on multipitch, ... ) apart from in extendable draws, and I also prefer them to using accessory cord. Thing is, having a pre-tied prussic sling from accessory cord is a piece of equipment that I can't really use for anything else while I always have a few of the aramid slings on me anyway. I always prefer multi-purpose gear, plus it feels good to know that it's rated for full strength :) for the other purposes, where I use it instead of dyneema slings, it also feels more reassuring, having a sheath and all. It is heavier though.
I use the 22Kn Edelrid ones to. And I disconnected my belay device and keep the Prussik on loads of time for different reasons during rappels. With the idea it’s full strength 22kn armide core rope. Now I’m curious what there strength is on a rope in a prusik knot 😅.
Super useful test for us actually working with ropes. I use my prusiks every day in my towers and masts.
Always watch till the end. Always bummed when it ends. Always want more.
my personal favourite way to abseil/ rappel is using a Hydrabot on a short sling to raise it up. this then gives me room to put a hollow block wrapped 3-4 times as an autoblock (french prusik). this gives me the safety of a self-belay while being able to abseil as fast as I want (hollow block is heatproof) and 1 handed for technical sections. having the belay below your repel device means it is so much easier to get going again as it doesn't have your whole body weight on it. the auto block is also super quick to tie and gives heaps of control.
Many years ago I used to solo climb, S roping (belay point at bottom, tie in with enough rope to reach a gear point, retie to next point, abseil back down when I run out of rope (clearing gear), then climb back up rope). Longest climbs were 3 pitcvhes.
No ascender, so I used a couple of prussik loops. They worked, but it was very slow and hard work! Tried Kleimheist, but it was very hard to keep the knot 'dressed' as I slid it back up the rope. Prussik was easy to keep neat.
Same diameter, try Blake's hitch! You add wraps depending on the work load,
Will also lower under load...
Awesome work!
I use the Blake's hitch a LOT. I'd love to see it tested.
This test would be nice on the test tower you’re building. To see the effect of the slippage. I use it to backup atc, to switch between shunt and atc and in case of a rappel from one bolt mid route.
Holy crap. I was thinking of requesting this from you guys yesterday. You read my mind
I'm not sure whether this is 100% accurate, but I was recently talking to an IFMGA guide about different material strengths, and thought I'd share an idea on why the hollow block may have failed dramatically below it's MBS, beyond just the fact that it is old and well used. I believe this is because technora has a fairly low "yield point." Given that we use this piece of equipment to add friction to rappels, and as a rope grab in various other scenarios, this point is not hard to reach, and as such the MBS of our Hollowblock will likely decrease more quickly than climbing ropes, slings, quickdraws, and other soft goods - even of similar age / with similar wear. That said, it will likely remain strong enough for it's primary application as a friction hitch, but if you run out of quickdraws and want to extend a piece of gear... don't whip on it! ;)
Like you said lots of variables, but interesting to think about as I personally do use a hollowblock regularly.
It would be interesting to see friction hitches on steel ropes (for zip lines, via ferrata bridges, etc). At work we sometimes use them if we forget the tensioner clamps and they always slip with slings.
I know this is old but would love to see the Hedden knot tested like this. It’s like the klemheist pulled in the “wrong” direction (or tied “upside down”). Or similar to the RBS here but without the carabiner. Supposedly much stronger holding power than klemheist (though I was taught otherwise at my mountaineering club), definitely easier to dress.
Some thoughts:
- I was taught that 4 wraps was the minimum for an autoblock or klemheist. Based on your results I definitely agree and would not ever rely on 3 wraps.
- Anecdotally I've always felt that the prusik knot was the most secure friction hitch. The autoblock and klemheist trade gripping power for ease of unlocking and sliding.
- I'd be interested to know what the history of that hollowblock was. The Sterling hollowblock is made from aramid fibers, which are much more susceptible to UV degradation than any of the other common synthetic fibers.
I dunno, that 7mm klemheist was pretty bomber
I was taught 4 for autoblock too. However it doesn't have to be very strong if itks used for rappelling on the leg loop as a block since there is a multiplier through the ATC/rappelling device. How hard does your hand grip the rope ?
The number of wraps totally depends on the application. For an autoblock as a "third hand" to backup a rappel, you just want it to add friction to the system. You want it to slip, but still have enough friction to engage your ATC to stop the rappel. So the number of wraps depends on the diameter of the loop and the diameter of the rope. There is no 'one size fits all'.
For newer skinny ropes with dry treatment I'd agree 4 wraps minimum. For older well worn, fuzzy and fatter ropes 3 is usually sufficient.
Outstanding content - this must be the best use of RUclips so far. Do more like this - test stuff we all do all the time! (Would also be interested in klemheist vs. viking [klemheist upside-down], but probably would enjoy your next idea just as much.)
I tried a prusik on a 60mm smooth aluminum tube using a 10mm wide nylon webbing loop, it grabbed very well. (We were hauling a 6 meter long thick wall antenna tube up a pole, and needed something to hold it when we weren’t lifting it or trying to feed it through a clamp, not supporting a person, nobody below it if it fell etc etc).
I use a Prusik as a back up when i am backing of a route because i can't reach the ankor or when i don't trust the anchor.
I connect my harnes with a carabiner and a prusik to the side of the rope which goes to the belayer.
The idea is that if the ancor or single point from which i am descending fails the prusik will prevent me from falling all the way down.
Still a big fall if the next quickdraw is far bellow me at the time of the anchor failing but better than no back up at all.
I wonder what would happen if i fall into my prusik backup....
So this video is very intresting to me!
But i'm not sure if it will behave differently if you fall into it as opposed to slowly increasing tension like you did with the machine.
Very good video anyway!
If you absolutely have to use the same diameter you can tie a Blake's hitch, works like a klemheist ie in just one direction.
Using friction hitches as life support is quite standard in tree work but we use 8mm minimum cord.
I think auto bloc definitely works better for double ropes rather than single. Ive seen it slip in single ropes where a klemheist was super good enough. Thanks for the science maaaaaaaan.
I like that you tried those hitches with the 10.5mm just to be thorough. Would be interesting to see how a blake's hitch would stand up to the slacksnap machine
I use an autoblock when rappelling regularly, and the one thing I've notices is that the knot doesn't bite unless it is shock loaded. It'll slip all day until you give it a good hard jerk. Maybe some day you can give this another try but instead of pulling straight away with the jack, you give the knot a sharp tug first so it can bite.
There is another big part to this that seems to be overlooked in the video, and that is the material science side of things. I would agree that for a friction hitch to work properly on your nylon / polyester ropes, you need a smaller diameter. However when you switched to the Sterling autoblock, that is technora. Technora interacts with nylon in a completely different way. Additionally, (not sure if you tested it or not) but the Klemheist or Multi wrap Hedon is a way better hitch when using that Sterling kit; due to the shape of it. In my line of work an instructor we typically use only technora - technora based kit; and we very regularly use 8mm VT prussiks on 7 or even 6mm technora lines. My point being that when using different materials, or intermixing, you will have widely different results. I'd like to see you test dynema slings and autoblocks on technora lines. I think you'll be surprised in the holding power (and the fact that you don't need dissimilar sized lines) :D Keep up the great work, you guys are an amazing resource!
One of the perks of the hollow block is that its Technora (similar to Kevlar) instead of nylon, which has a substantially higher melting temperature. This makes it less likely to weld. For rapping with a back up, the kevlar will handle the heat generated better and won't risk degrading the material as much, especially on long, fast, free-hanging raps. Also, given the fiber's chemical resistance, I suspect it holds up to the elements a bit better than nylon over time. Plus, I just like having a sewn connection instead of a bulky knot, but that's just preference. I have also found it to grab much better on the ropes I use. I suspect the condition of the rope sheath influences friction a ton, and I wonder if you were using the same section of rope for all your tests. If so, maybe the repeated heating and rubbing smoothed it out a bit and made it more slippery?
1:12 this is such a bloody greatt channel,
As a tree climber I use friction cord almost every day. Try and eye to eye beeline 8 mm
Always good to see other tree guys on this, I've tried getting other guys to watch the videos! Some stuff isn't relevant but knowing about loading and strengths of stuff is essential.i think!
@@zackbroad4293 do you rock climb also? I’ve thought about pursuing arborism and wonder just how many of my skills would translate.
@@kaimcguire5086 no just tree work! I have looked at rock climbing. I feel like tree work to rock climbing wouldn't transfer super well, but rock to tree would be great as the strength and stamina from that would help a lot!!
8mm for sure :) Beeline - great cordage
And maybe try the same tests with some popular tree climbing knots like a VT, Michoacán, Distel...
I think since most of the strength comes from the core you'd need to slip quite are while to wear through the mantel and significantly reduce the strength.
I mostly use the klemheist, with only two wraps, and I find that works perfectly for a smooth rappel.
If I need a safety line while rigging a top rope, I use a prussik.
Ha, all this time I thought hollowblocks were the ideal material for friction hitches. Good stuff.
I used a hollow block for years, or worked well, but eventually I replaced it with a sewn piece of kernmantle cord (either 5 or 6mm, I'm not sure).
Kernmantle construction gives me more piece of mind, because as long as the sheath is intact, the core should be completely undamaged and also largely protected from dirt and abrasion.
I mostly use the klemheist, with only two wraps, and I find that works perfectly for a smooth rappel.
If I need a safety line while rigging a top rope, I use a prussik.
Long repels could burn through your 5 or 6 mm cord auto block knot, that's why the hollow block is made from Technora material. It has higher melting temperature so it won't weld itself to the rope, also used for firemen excape ropes they melt somewhere around 1100ﾟ I believe.
VT prusik!!!
it's often used as a primary hold, I have repelled off one many a time (technora sheath or it burns out)
"OK forget it it doesn't work, just like everyone says" I LOLed at that one
Can you test a few of these using static rope? For rappelling, ascending, or a backup line while climbing I use a static rope. When the dynamic rope stretches the diameter decreases and the diameter of the main rope approaches the diameter of the friction hitch. Similar to the test with the 10mm on 10mm friction hitch. Thanks!! Really enjoy your channel!!
I bootied a hollow block on a classic multi at City of Rocks, been using it since then because it was brand new. On my mammut rope I have to throw an extra wrap on my auto block because they're both pretty silky, its not a problem on our maxim. I personally would never pay 20-whatever dollars for one though. My thought would be to test the knots with 2 strands of rope inside like most people rap. Thanks for the video!
You have to test friction hitches on the drop tower once it‘s completed. Different results there. I participated in some drop tests at a course at the Petzl Technical Institute with a dummy. We simulated a fall from a lege with some slack between the prusik and the anchor. It cut the mantle sometimes but the fall was stoppe after 30cm to 1m by the prusik.
Another tree climber here. I'd also be curious to see an eye to eye with a valdotain tresse (with 5 and 6 wraps) and distel hitch. The valdotain should slip but I'd love to know at what point. Feel like the distel would be more likely to break🤷🏿♂️
A common belaying technique in high angle rescue is a tandem prussik system. Usually 2x 8mm 3 wrap prusiks on 10mm to12mm static ropes.
I use a 6mm cord and I mostly use autoblock with 3 or 4 wraps (if I'm the first person rappelling and knowing there is some snag on the rope, I use 4 wraps, otherwise, 3 wraps) for rappelling, as long as it is not completely vertical or negative wall, on these cases I use climb heist. To ascend I use prussik always
Nice this is definitely reassuring, thanks for the content!
7:26 i think its the available slack in the presick, that might be the difference
10:30 ohh sorry, this was meant to be fore the auto block
i'm french and we use autoblock with 6 or 7 mm rope but we take off a bit of the inside of the rope to maje it more soft. it works fine
I use 6 mm klemheists quite a lot in anchor building and in rappelling as well. I took a different conclusion, seems like those are pretty darn good and I still feel comfy with it.
From South Africa here. In the guiding industry we use 4-5 wraps for the French Prussik or what you’re calling auto lock. The French Prussik is releasable under load while the clemheist bites like a possessed pit bull. Also use 4-5 wraps for that. We avoid using three wraps in anticipation that some unravelling occurs.
If u use a tied prusik u can tie in a Michoacon. It has been the most stable going up & down the climbing rope. A lot of the time I use an eye to eye prusik that has small factory sewn eyes which helps from side loading the carabiner.
I know this is an old video and my comment isn't particularly climbing related, however I use prusiks camping on my ridgeline to secure my tarps to (I use a prusik trough the tarp tieout with a toggle or just a random stick to adjust/hold tension on the tarp) my ridgeline is 550 paracord, for a long time I used 550 cord for the prusiks as well and they hold just fine even in 50km/hr or stronger winds (i have since switched to 325 cord or #36 bank line for the prusiks just for a smaller packing size mostly. I do get how a thinner rope grabs better but in some materials a like sized rope seems to grab prety well still without sliding so easily.
And as for the one rope cutting the other, I know as a "survival tip" that you can cut (see through) a thicker rope with a thinner one prety easily in a pinch if you dont have a knife but cutting a rope with a thicker or same sized rope doesn't work well of at all.
I was taught in France, that Prussik, autoblock and kleimheist knot were to be used when you have 2 strands of rope like when rappeling. On a single strand, they tend to slip.
On a single strand, the knots i was shown were valdotain tresse, distel or schwabisch knot. Which are used in tree climbing.
I use a hollowblock on one strand (10-11mm static) as a third hand, never seen a slip, this is of course of very low loads, nothing even getting close to 1kN, but it holds and doesn't slip at all....
reading about knot safety and tendency to “roll” or “turn over” is not nearly as interesting or exciting as seeing that happen. 👍🏼👍🏼
haha true
Reading about doesn't equal the ultimate ass puckering moment theory doesnt become reality.
I always use 3/4 " strap and Prussik knots. They wok well and have a lot more surface area than a round cord
In arboriculture, I use a knot called a BLAKE. It's not only a friction knot, it's the entire rappel system. And it's made using the other end of the rope. So, you guessed it, using same diameter rope! I would not hesitate to use it in a situation where there nothing left but the rope itself
This is the episode I have been waiting for!
Although for ascending or descending (lifting or lowering), the prussik and klemheist the turns are not even to either side so that it rides easier in one direction and theoretically locked stronger the other. Haven’t really used them in the “standard form”. Also these were developed in times that ropes were presumably natural fibers, which is passé now - but having the ropes in more contrasting materials may give altogether different results?
one of my fav videos yet!
Regarding 9:07 , if you were needing to use similar to equal diameter cord to form a hitch, a blakes hitch would be a more appropriate option. This certainly derivatives from the channel topic, as this is primarily used by arborists. However, it could be useful to know for climbers as well, as this allows you to create a hitch that allows you to both ascend & descend a rope using only the rope itself, without cutting a section off. Certainly, there is some emergency usage potential there.
I tried using a hollow block the other day as a prusik to ascend a static rope (with my gri gri). It did not work at all! Any time I would weight the damn thing to pull slack through my gri gri, it would just slip! Had to switch it out and use a sling instead, which worked like a charm
Use prusik for 3rd hand repelling. Found that klemheist is better for ascending than a prusik on lost arrow spire . When weighted the prusik is tough to slide up. Also you can put the klemheist around a carbineer to give a handle to your ascender.
I realize that the Blake’s hitch or the taut line hitch are only used in tree work, but they’re commonly used with either the other end of the rope you’re climbing, or a split tail system with a separate shorty piece of rope that is the same diameter as your climbing rope. I’d be interested to see what those break/break loose at.
I use the blake's hitch for the same diameter of rope and it does not slip, you could try it
I tried Blake's hitch with a climbing rope and it slipped under my body weight
@@eyescreamcake Perhaps the type of rope requires more turns or to dress it correctly, it is a knot used for that specific purpose, a friction knot that retains even with rope of the exact same size, that is why it is in the safety catalog
I'm an arborist I too use the Blake's hitch all on the same rope I use the tail of my rope to tie it on a mrs system I have found that it will slip on kernmantle ropes but holds tight on 16 and 24 strand ropes.
Yep the rope needs certain knot characteristics for Blake's to work. The 5 3 variant can help sometimes. Gotta set it right too
I’ll have to try the kleimheist. Although when backing up a rappel you should never get extreme forces, I’ve never felt secure using an autoblock and this video validates that. I stick with prussik.
Really appreciate all your efforts
ive used 5mm prusiks on 10mm rope for years even to the point of rappelling off one single prusik single rope no backup. its scary (and stupid I know) looking at dental floss holding onto your life but under static load that stuff is damn strong. Climbing rope technology is absolutely amazing.
Knott slippage is one of my larger questions. Seeing how they fail does seem like there are a couple variables.
I use to rock climb many many years ago carabiner and clogs and secondary rope . Times has changed so much
Feel like testing a "blakeshitch"...... Great video and very informative 👍👍
Always amazing videos and tests... You should think next time include the VT knot or Valdotain Knot in those tests... Cheers mate...
I think the moving big rope absorbs the heat from the smaller rope as it runs, so it takes much long to heat the prusik to failure.
I always knew I didn't really ever like the auto lock for some reason 🤔The prusik was always my most trusted and favorite rappel back up...
Nice informative video! What about testing figure 8 and bowline knot?
I'm a member of a regional technical rescue team. We use 9mm prussics on NFPA G 1/2" static rope for almost every thing. Tandem prussic belays, progress capture, quick adjustment for anchors, anchor tie backs, adjustable fall protection, accending, holding edge pro in place, etc.
@ 8:06 holy cow! I love this!
Thanks for doing this,
Would love to see the bachman’s knot/Prussik tested. It’s where you put the spine of a carabiner to the climbing rope and then wrap the Prussik cord around the rope and spine and then clip the rope into you harness or whatever. Normally used for ascending
I’ve always heard friction knot accessories 1/2 size of main. Good reminder to pay attention to size ratings of fig 8, progressive captures, belay devices, etc