CLIPS video complementing this video of other tests we did that afternoon - "Can you get Twin Tension rescue ropes evenly tensioned" th-cam.com/video/H0M6F16vWTA/w-d-xo.html Check out our new store! hownot2.store/
@@Mike-oz4cv prussik is good normally for failure but not if you secure only one rope in the ATC on a double rope rappel, I used to test it on ground and the prussik was grabbing only the secured rope and the free rope was going up while simply walking back, would have been a big crazy fall. We must always test the system on top and not thinking everything will be ok cause we use a prussik.
@@pascaljutras178 Just thinking about unlikely scenarios here. For example the ATC carabiner accidentally opening and unclipping itself. In that case it’s nice to know that a prusik is plenty good enough to hold you.
Footlocking a doubled rope with a prusik or klemheist has long been a standard method for arborists ascending trees. It’s fascinating to see these systems tested
Not like this - what arborists called 'double rope' (now 'moving rope system') is a rope fixed to their harness, over a branch, back to their harness. One end is fixed to their harness and one end is prussiked to their harness. The prussik sits on one leg of rope.
@@smallcoppercoins01no they are correct brother, a foot lock line is a static double line, different than moving rope system. old technique you should check it out online , super cool. need a very long prusik which is called a foot locking prusik
This result would indicate that the defining factor of a prusik is the ratio of the prusik cord diameter to the net diameter of the line it is attached to. In the case of the double rope, the effective diameter should be about 1.5 times the rope diameter, which would indicate a higher grip and less slip. Which is what you saw. A neat test would be to try a prusik on a thin rope (like 8.5mm), then double the thin cord, and then try a single larger rope (13mm) and see if the force to start slipping is the same.
This channel has some of the most absolutely useful and IMPORTANT information I've found online. As a climber for over fifty years and instructor for more than forty, I'm delighted to still be learning from you guys! 🙏
Manufacturers match the size of the prusik cordage to their ropes, those factors along with how the rope is constructed determine the performance of how the prusik will perform under a load. Prusik cordage diameter is a critical factor in the equation
I'm a mountain climber and arborist, Ryan and Bobby thank you for answering every question I have ever had about gear's ability and many more I could never have thought of. In all my experience it's the pink naked upright walking monkey dangling from the gear thats ALWAYS the weak link! Yes even me! If there is enough interest from the community I should like to volunteer to be tested on the slack snap machine. lol Please carry on break-in gear fear
I really like this sort of content. The rope rescue world is full of practices that are based on tradition and we are not sure what they would actually fail at. 8mm prussiks on 11mm and 12.5mm ropes have been tested to death, and their behavior and peak forces are all over the map.
As a retired?? climber, in other words the spirit is willing but the flesh is weak, this fascinating. I used to sew my own gear and had a friend at GA TECH materials science lab who would test a sample for me but this way way better. Super good enough.
TIL that prusik on two ropes ends up having more friction than a single. But I guess that makes sense in that two ropes will have more surface area than a single.
Enjoyed the content. Am a arborist and Firefighter and watch a lot of your stuff because eventually it crosses over and I find things that are applicable to our profession. Good stuff
I’m happy to see this video Ryan. It’s common practice in Rope Rescue for a litter attendant to put a prusik around both main lines just above the yoke knot of the little bridle, and then have that be their primary attachment point to give a little extra space for litter attendant movement. The speculation was that it might not hold properly. This proves that holding power is not an issue. The only other concern is when using, a freestanding artificial high directional, like an Arizona Vortx in the easel leg configuration. If the rescuer has set that prusik two or 3 feet above the yoke knot, it can run into the high directional pulley and quickly change the force resultant creating an instability. It’s just a concern to watch out for and I think that this test shows that a single prusik works well attached to two main lines.
Thanks for making this! I’m a firefighter and we were just talking about this very thing today, so it was great to have your testing to answer questions we had. More testing like this or more testing with fire/rescue service personnel and systems would be invaluable as we continue to evolve our training.
Very pleased it works to prusik on both because I've climbed up ropes like that and good to know I haven't died and didn't realise ;) Also I've used French prusik (auto block) above my descender (passing knots is easier that way, I know people will reply it is "wrong") on doubled ropes for retrievable abseil (rappel) and that grabs really well - better than on a single rope
Tom Tom, I've always done the same thing and its always worked great. I'm just some old guy in the mountains with minimal gear, double rope fits my needs often.
Love these videos. I do rope rescue and confined space, and seeing how everything works and fails is allowing me to adapt to different methods and equipment I would have otherwise never considered.
The problem is that after you watch the Palikoa Pivot break half the gear he tried to break it with, you start wondering how to build a chain out of them. th-cam.com/video/l8VvEWdDMus/w-d-xo.html
I love seeing the limits and modes of failure on the gear. Seeing what it takes to get gear to fail, and having realistic ideas about actual operational loads and forces is priceless! Love your work! Please keep it up!❤
As an engineer and climber this content is great!! I've always used a prusik under my rappel device and for emergency ascents on double ropes, so this is very interesting. It would also be helpful to see other autoblocking knots for comparison!
Sort of akin to using an undersized friction hitch for the rope diameter. Tree work is generally -3mm, ie use a 10mm hitch cord on a 13mm rope, 8mm on 11mm rope. This makes the rope effectively larger. I assume you can lock up these hitches to point where you can't loose them by hand. Cool video!
I would love to see more rescue stuff. Maybe breaking rescue pullyes or figure 8s or even full z rigs. I got into climbing through firefighting and the military and would love to see that stuff. A swiss seat would be cool too
I've had the question of prusik on single vs double rope for a while now. Been using it but good to see it pushed to the limits without people on the other end. Good video!
I used a prusik on a double rope as a safety line the last few days going up and down a 30 foot ladder trimming an oak tree. The prusik is about the same size rope as the safety line, only required 2 wraps of the prusik to have enough friction.
It's good to see that this works OK, since I definitely used it before in a pinch to ascend a doubled rope to rig/derig some circus aerial apparatuses on a portable rig when I didn't have a ladder handy!
I've ascended two strands wrapped with prussiks many times. I'd always assumed it would have more grip because of the larger combined ratio of rope to prussik. More surface area to grip at the least. Nice to know its super good enough :)
I’m surprised that you were surprised! From your video on the VT prison and other friction knots I vaguely recalled that the ratio of rope to rope determined grippiness. E.g. 8mm Prusic won’t grab on 9mm half rope. But fat dual 13s it would grab really hard. And did.
definitely interested in videos like this. I always thought from personal experience ascending ropes with prusik knots that 2 ropes would have better grab than 1 so it's good to see that confirmed
Today I asked Google if friction hitches on double ropes were effective, and it turns out you posted a video about it 2 weeks ago! I actually rigged up a little test of my own before looking online, but it always feels better to see the numbers.
I did some spelunking with prussiks because I didn't have more appropriate ascenders. Perhaps a bit more muddy than the rope in this test, but worked. IIRC, 6mm cord on 11mm rope. Prussiks are taught as self rescue or backup methods.
I often use prusiks on double ropes. Well, i use schwabisch knots. The capability of double ropes is why i often use friction knots instead of mechanical ascenders. If you get your ropes stuck on the pull after a rap, you want to grab both ropes on the ascent. Only a few mechanical rope clamps will do that. EDIT 3 days later: lest I forget, I really, really appreciate you doing this stuff... so I don't have to worry as much. And you are funny.
The talk about the basket and the train sounded new, I haven't heard those terms before. If it isn't a series of rappelers coming down one after another, then I don't know what it is. I learn an awful lot on this channel beyond what my outdoor recreation degree taught me.
In the fire service, a medical patient is strapped into a "basket" in rope rescue situations to pull them out of a bad spot, and put them in a vehicle. Depending on the situation, firefighters can clip into the basket, maybe that's what he means by train
He was talking about terrain. When using a basket to evac a pt the rescuer has to keep the basket away from the rock face. The basket will some time catch and then the system goes from moving to static rapidly increasing the forces on it. Usually you would use your feet ant legs to push away from the rock. The basket and rescuer is lifted with a mechanical advantage system in the rope. The prussik is used as a grab to connect the MA to the ropes.
Looking at the behaviour of the prusik on the doubled rope, physically it looks like the paired rope is squashed to be virtually a single larger diameter rope - changing the prusik cord diameter to host rope diameter ratio. It would be interesting to see if you get the same result with the same size prusik cord on a larger diameter rope.
This is why testing is so important. Even with decades of rope experience I was sure that the prusik would grab tighter on a single strand than a double. Thank you HowNOT2. Can you compare the larks head to the prusik to the prusik^3 to the prusik^4 please (i.e. how each additional or fewer wraps changes the grip.)
Love this I find it crazy that they use it for 10 plus years I'm on sar in Alberta Canada and we have to retire after 5 if it's been used and it has a ten year shelf life if never used but crazy how's much force it still takes
A fascinating examination of this knots characteristics under load. It fails very gracefully all things considered on a single line with the slipping. It's wild how it got hot enough to start melting like that! Great video! Can you do one for the trumpet knot? (Designed to tie out a bad or worn section in a rope without cutting it.) I know that isn't really a climbing knot per se but it is kind of unusual and maybe interesting to see like this. Great stuff. 👍
Thank you so much for the work you are doing! I appreciate the videos on knots , their strength, and the way they fail! Please test and review the JRB ascender hitch !
In our wilderness rescue practice, we have largely moved away from using Prusiks, simply because of the range of their performance variation, which typically encompasses "slips easily" all the way to "breaks host rope". This variation is based on some many factors that it is essentially impossible to predict. We now use mechanical rope grabs that have engineered slip limits that prove far more consistent.
Throw a rope over a tree and prusik up. Easiest way to get up there. Also I learned that the prusik grabs better the bigger the difference in diameter between the sling and the main rope is so that's probably why double rope grabs better.
I used to work at an outdoor centre where we used steel eye carabiners to clip into harnesses. To start with we used rethreaded figure 8's to tie into the eye carabiners but we eventually switched to using Bowline on a bight (we used s stopper knot on the tail for both knots). I'm trying to remember why we did this and thinking that the Bowline on a bight might have been stronger, but I can't find the breaking stats for the bowline on a bight in climbing rope. Would you be able to do an episode for figure 8 vs Bowline on a bight, please? Thanks 😊👍
well, results kinda make sense to me. I was always told that the bigger the difference between ropes, the better the prussik will hold (i.e. a 6mm prussik on an 8mm rope will not grab as much as a 4mm prussik on a 11mm rope). And you are basically "doubling" the rope, so it makes sense the prussik grabs stronger. But now I'm curious about prussik/descender knots (can't remember if you already did), it would be interesting to know how grab changes with the different times you circle the main rope, and coparing prussik, machard and bachman.
Not sure there is an easy answer, but maybe showing at what point other progress capture devices will start to damage a rope. Either a prusik will always be lower or in same cases, a tooth based progress capture device is better suited for grabbing onto rope safely (repeatedly).
As a canyoner (@105kgs) I’ve practiced prusiking 7mm Prusik on double 9mm static ropes heaps of time - no problemmos - though at my weight, I tie asymmetrical knots otherwise I can’t shift up.
The single rope failure is much lower than i thought it would be. What prussik material were you using? Sterling sewed 8mm slings are rated for 17kn and the CMC 8mm cordage with tied double fishes we're more like 10kn. Just an aside, we did a test years ago where we set up a highline with a 440 lb load and cut the mainline. The tandem prussiks were attached to a load cell. After cutting the line the load dropped a couple of meters and the load cell only showed around 5kn.
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CLIPS video complementing this video of other tests we did that afternoon - "Can you get Twin Tension rescue ropes evenly tensioned" th-cam.com/video/H0M6F16vWTA/w-d-xo.html
Check out our new store! hownot2.store/
why was that video on the clips channel? I thought that one was very cool and interesting, and somewhat different
I've always used a Prusik on two strands below my repel device when repelling. So this was pretty cool to see.
In that case, the prusik is basically only ever going to hold enough force to keep the brake strand in position, which would be much less than 1kN.
@@Govanification This. Unless your rapel/belay device is suffering catastrophic failure.
Its just a backup❤ its good protocol
@@Mike-oz4cv prussik is good normally for failure but not if you secure only one rope in the ATC on a double rope rappel, I used to test it on ground and the prussik was grabbing only the secured rope and the free rope was going up while simply walking back, would have been a big crazy fall. We must always test the system on top and not thinking everything will be ok cause we use a prussik.
@@pascaljutras178 Just thinking about unlikely scenarios here. For example the ATC carabiner accidentally opening and unclipping itself. In that case it’s nice to know that a prusik is plenty good enough to hold you.
Footlocking a doubled rope with a prusik or klemheist has long been a standard method for arborists ascending trees. It’s fascinating to see these systems tested
For a long time!
Not like this - what arborists called 'double rope' (now 'moving rope system') is a rope fixed to their harness, over a branch, back to their harness. One end is fixed to their harness and one end is prussiked to their harness. The prussik sits on one leg of rope.
@@smallcoppercoins01no they are correct brother, a foot lock line is a static double line, different than moving rope system. old technique you should check it out online , super cool. need a very long prusik which is called a foot locking prusik
This result would indicate that the defining factor of a prusik is the ratio of the prusik cord diameter to the net diameter of the line it is attached to. In the case of the double rope, the effective diameter should be about 1.5 times the rope diameter, which would indicate a higher grip and less slip. Which is what you saw.
A neat test would be to try a prusik on a thin rope (like 8.5mm), then double the thin cord, and then try a single larger rope (13mm) and see if the force to start slipping is the same.
This channel has some of the most absolutely useful and IMPORTANT information I've found online. As a climber for over fifty years and instructor for more than forty, I'm delighted to still be learning from you guys! 🙏
I'm just into rigging and find this channel to be the best at examining this subject too. 👍
Former rock climber turned firefighter. I love this and and the other rescue videos you have done!
Manufacturers match the size of the prusik cordage to their ropes, those factors along with how the rope is constructed determine the performance of how the prusik will perform under a load. Prusik cordage diameter is a critical factor in the equation
I'm a mountain climber and arborist, Ryan and Bobby thank you for answering every question I have ever had about gear's ability and many more I could never have thought of. In all my experience it's the pink naked upright walking monkey dangling from the gear thats ALWAYS the weak link! Yes even me! If there is enough interest from the community I should like to volunteer to be tested on the slack snap machine. lol
Please carry on break-in gear fear
I really like this sort of content. The rope rescue world is full of practices that are based on tradition and we are not sure what they would actually fail at. 8mm prussiks on 11mm and 12.5mm ropes have been tested to death, and their behavior and peak forces are all over the map.
As a retired?? climber, in other words the spirit is willing but the flesh is weak, this fascinating. I used to sew my own gear and had a friend at GA TECH materials science lab who would test a sample for me but this way way better. Super good enough.
TIL that prusik on two ropes ends up having more friction than a single. But I guess that makes sense in that two ropes will have more surface area than a single.
Enjoyed the content. Am a arborist and Firefighter and watch a lot of your stuff because eventually it crosses over and I find things that are applicable to our profession.
Good stuff
Like it. Using prussics as backup for descending on double ropes. Until recently only 2 turns. Now I am using 3
I’m happy to see this video Ryan. It’s common practice in Rope Rescue for a litter attendant to put a prusik around both main lines just above the yoke knot of the little bridle, and then have that be their primary attachment point to give a little extra space for litter attendant movement. The speculation was that it might not hold properly. This proves that holding power is not an issue. The only other concern is when using, a freestanding artificial high directional, like an Arizona Vortx in the easel leg configuration. If the rescuer has set that prusik two or 3 feet above the yoke knot, it can run into the high directional pulley and quickly change the force resultant creating an instability. It’s just a concern to watch out for and I think that this test shows that a single prusik works well attached to two main lines.
Thanks for making this! I’m a firefighter and we were just talking about this very thing today, so it was great to have your testing to answer questions we had. More testing like this or more testing with fire/rescue service personnel and systems would be invaluable as we continue to evolve our training.
Awesome content. As an engineering student, I am always excited to see your videos and ponder why these results happen. Thanks for the videos.
Very pleased it works to prusik on both because I've climbed up ropes like that and good to know I haven't died and didn't realise ;) Also I've used French prusik (auto block) above my descender (passing knots is easier that way, I know people will reply it is "wrong") on doubled ropes for retrievable abseil (rappel) and that grabs really well - better than on a single rope
Tom Tom, I've always done the same thing and its always worked great. I'm just some old guy in the mountains with minimal gear, double rope fits my needs often.
As an arborist, I really love that !!!! Thanks
I was looking up this very thing the other day and didn’t get the warm and fuzzy from my research, but now I have the data to back it up!
Definitely want more rescue gear content. Thank you so much for all you do.
Great video! I'd like to see the hollow block put through several rope configurations or different diameter accessory chords tested too
Thats some jolly good content right there
Love these videos. I do rope rescue and confined space, and seeing how everything works and fails is allowing me to adapt to different methods and equipment I would have otherwise never considered.
The problem is that after you watch the Palikoa Pivot break half the gear he tried to break it with, you start wondering how to build a chain out of them.
th-cam.com/video/l8VvEWdDMus/w-d-xo.html
I love seeing the limits and modes of failure on the gear. Seeing what it takes to get gear to fail, and having realistic ideas about actual operational loads and forces is priceless!
Love your work! Please keep it up!❤
Love the videos as a saddle hunter I appreciate the variety of information you put out.
Love it. Thanks for going the extra effort in testing.
Yes! Lots more of this, please! As someone who works on a rope rescue team, this stuff is fascinating!
As an engineer and climber this content is great!! I've always used a prusik under my rappel device and for emergency ascents on double ropes, so this is very interesting. It would also be helpful to see other autoblocking knots for comparison!
Loved this! You guys have such great set-ups for testing, I will always watch these videos.
Sort of akin to using an undersized friction hitch for the rope diameter. Tree work is generally -3mm, ie use a 10mm hitch cord on a 13mm rope, 8mm on 11mm rope. This makes the rope effectively larger. I assume you can lock up these hitches to point where you can't loose them by hand.
Cool video!
Awesome
Just the type of TH-cam I like
I would love to see more rescue stuff. Maybe breaking rescue pullyes or figure 8s or even full z rigs. I got into climbing through firefighting and the military and would love to see that stuff. A swiss seat would be cool too
I've had the question of prusik on single vs double rope for a while now. Been using it but good to see it pushed to the limits without people on the other end. Good video!
Awesome. So much value for rope users.
Just leaving a comment to help with the algorithm. Thank Ryan for all you do.
That’s a great shirt idea, if not already in play. Heart beat of a Prusik
I used a prusik on a double rope as a safety line the last few days going up and down a 30 foot ladder trimming an oak tree. The prusik is about the same size rope as the safety line, only required 2 wraps of the prusik to have enough friction.
Hell yeah I like it!! The way I see it is _Content is Content_ and I'm just happy to get it. 👍👍
Love it! Can’t believe it took me this long to find you!! Keep it coming!
I like all of your content but I love the rescue content!
This is good stuff, not everything is about the breaking point, it's about the failure point, and those two things aren't always the same.
It's good to see that this works OK, since I definitely used it before in a pinch to ascend a doubled rope to rig/derig some circus aerial apparatuses on a portable rig when I didn't have a ladder handy!
This is the kind of content I like as a patron!
I've ascended two strands wrapped with prussiks many times. I'd always assumed it would have more grip because of the larger combined ratio of rope to prussik. More surface area to grip at the least.
Nice to know its super good enough :)
I’m surprised that you were surprised! From your video on the VT prison and other friction knots I vaguely recalled that the ratio of rope to rope determined grippiness. E.g. 8mm Prusic won’t grab on 9mm half rope. But fat dual 13s it would grab really hard. And did.
68,000 views in 10 months. Well on the way to 100k. Most excellent channel.
Very helpful content Ryan! I use 8mm prusiks on 11mm and 13mm rope in DMDB and TTRS systems - good to know the options and capabilities 👍
Just the video I need today. What a coincidence!
definitely interested in videos like this. I always thought from personal experience ascending ropes with prusik knots that 2 ropes would have better grab than 1 so it's good to see that confirmed
I had this exact question when using a prussik as a third hand on a two rope rappel
This is what I come to this channel for! I love the nerdy stuff.
Today I asked Google if friction hitches on double ropes were effective, and it turns out you posted a video about it 2 weeks ago! I actually rigged up a little test of my own before looking online, but it always feels better to see the numbers.
I did some spelunking with prussiks because I didn't have more appropriate ascenders.
Perhaps a bit more muddy than the rope in this test, but worked. IIRC, 6mm cord on 11mm rope.
Prussiks are taught as self rescue or backup methods.
I love the content focused on fire and rescue.
I often use prusiks on double ropes. Well, i use schwabisch knots. The capability of double ropes is why i often use friction knots instead of mechanical ascenders. If you get your ropes stuck on the pull after a rap, you want to grab both ropes on the ascent. Only a few mechanical rope clamps will do that. EDIT 3 days later: lest I forget, I really, really appreciate you doing this stuff... so I don't have to worry as much. And you are funny.
Buy an alpine Up from Climb tech
Fantastic content! I really appreciate these kinds of videos, as they are very relevant to my climbing practices. Thanks!
Great to see this test, thanks HowNOT2
Nice! Yes. As always, great stuff ryan. Keep pushing
The talk about the basket and the train sounded new, I haven't heard those terms before. If it isn't a series of rappelers coming down one after another, then I don't know what it is. I learn an awful lot on this channel beyond what my outdoor recreation degree taught me.
In the fire service, a medical patient is strapped into a "basket" in rope rescue situations to pull them out of a bad spot, and put them in a vehicle. Depending on the situation, firefighters can clip into the basket, maybe that's what he means by train
He was talking about terrain. When using a basket to evac a pt the rescuer has to keep the basket away from the rock face. The basket will some time catch and then the system goes from moving to static rapidly increasing the forces on it. Usually you would use your feet ant legs to push away from the rock. The basket and rescuer is lifted with a mechanical advantage system in the rope. The prussik is used as a grab to connect the MA to the ropes.
I think the train is actually the team of people pulling the rope, from up near the anchor
Awesome learning new stuff about two rope repel.
Thx
a very practical and awesome experiment 👍
Looking at the behaviour of the prusik on the doubled rope, physically it looks like the paired rope is squashed to be virtually a single larger diameter rope - changing the prusik cord diameter to host rope diameter ratio. It would be interesting to see if you get the same result with the same size prusik cord on a larger diameter rope.
This is why testing is so important. Even with decades of rope experience I was sure that the prusik would grab tighter on a single strand than a double. Thank you HowNOT2. Can you compare the larks head to the prusik to the prusik^3 to the prusik^4 please (i.e. how each additional or fewer wraps changes the grip.)
Love this I find it crazy that they use it for 10 plus years I'm on sar in Alberta Canada and we have to retire after 5 if it's been used and it has a ten year shelf life if never used but crazy how's much force it still takes
Wow!! Dang! 19 kN is pretty wild for the double. That's pretty crazy, the "heartbeat" at 9 kN for the single
A fascinating examination of this knots characteristics under load. It fails very gracefully all things considered on a single line with the slipping. It's wild how it got hot enough to start melting like that! Great video! Can you do one for the trumpet knot? (Designed to tie out a bad or worn section in a rope without cutting it.) I know that isn't really a climbing knot per se but it is kind of unusual and maybe interesting to see like this. Great stuff. 👍
Loving it. Thanks for all the knowledge.
Would like to see other versions of the prusik. VT, french, autoblock etc.
Great, a good information for climbing safety 🧗
love it
Looking forward for you to test a Blake's Hitch. I'd really like to see that, since I've been counting on it for years lol.
Yes yes yes!! Want more of this.
Ya know. This make me feel a lot better about my third hand. Do things right and the safety is there.
Thank you so much for the work you are doing!
I appreciate the videos on knots , their strength, and the way they fail!
Please test and review the JRB ascender hitch !
Interesting to see sling prussic around four strands as used in escaping the system when belay is entirely rope built.
"That's the heartbeat of a prusik!" Ha! Ryan's got jokes! =-D
Very helpful video, please make more friction hitch testing, maybe autoblock or Klemheist?
Love any testing 👍🏼👍🏼
Thank you for sharing your great experiment.
I would like to see if the prusik would still work if one of the two ropes breaks.
Love this kinda stuff!
After glaising, how much do ropes still hold?
I Like this
In our wilderness rescue practice, we have largely moved away from using Prusiks, simply because of the range of their performance variation, which typically encompasses "slips easily" all the way to "breaks host rope". This variation is based on some many factors that it is essentially impossible to predict.
We now use mechanical rope grabs that have engineered slip limits that prove far more consistent.
I just trying to learn this. Could you provide a name of a mechanical replacement for a prudish?
Prusik- autocorrect
@@chadhanson3431 We use Petzl Rescuecenders
This was great, thanks
I would love to see prussiks of different material or other hitches. Great videos!
Throw a rope over a tree and prusik up. Easiest way to get up there.
Also I learned that the prusik grabs better the bigger the difference in diameter between the sling and the main rope is so that's probably why double rope grabs better.
Appreciate the content 🤙
Great video!
This is a great vid Ryan, is there any new bobby tshirts coming out?
Thanks
Prusik on double rope rapp just gets in the way.
I used to work at an outdoor centre where we used steel eye carabiners to clip into harnesses. To start with we used rethreaded figure 8's to tie into the eye carabiners but we eventually switched to using Bowline on a bight (we used s stopper knot on the tail for both knots). I'm trying to remember why we did this and thinking that the Bowline on a bight might have been stronger, but I can't find the breaking stats for the bowline on a bight in climbing rope. Would you be able to do an episode for figure 8 vs Bowline on a bight, please? Thanks 😊👍
Liked it. Great video!
well, results kinda make sense to me. I was always told that the bigger the difference between ropes, the better the prussik will hold (i.e. a 6mm prussik on an 8mm rope will not grab as much as a 4mm prussik on a 11mm rope). And you are basically "doubling" the rope, so it makes sense the prussik grabs stronger.
But now I'm curious about prussik/descender knots (can't remember if you already did), it would be interesting to know how grab changes with the different times you circle the main rope, and coparing prussik, machard and bachman.
I'd love to see thw difference between a 3wrap slipping prusik and a 4wrap same diameter. Would it still slip?
Not sure there is an easy answer, but maybe showing at what point other progress capture devices will start to damage a rope. Either a prusik will always be lower or in same cases, a tooth based progress capture device is better suited for grabbing onto rope safely (repeatedly).
As a canyoner (@105kgs) I’ve practiced prusiking 7mm Prusik on double 9mm static ropes heaps of time - no problemmos - though at my weight, I tie asymmetrical knots otherwise I can’t shift up.
Yes! More life safety (1/2”) rope
The single rope failure is much lower than i thought it would be. What prussik material were you using? Sterling sewed 8mm slings are rated for 17kn and the CMC 8mm cordage with tied double fishes we're more like 10kn. Just an aside, we did a test years ago where we set up a highline with a 440 lb load and cut the mainline. The tandem prussiks were attached to a load cell. After cutting the line the load dropped a couple of meters and the load cell only showed around 5kn.
Now that's some results 8:34