CLIPS video complementing this video of other tests we did that afternoon - "Can you get Twin Tension rescue ropes evenly tensioned" kzfaq.info/get/bejne/fpZ9aalim9y7hHU.html Check out our new store! hownot2.store/

I've always used a Prusik on two strands below my repel device when repelling. So this was pretty cool to see.

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

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! 🙏

Former rock climber turned firefighter. I love this and and the other rescue videos you have done!

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

Like it. Using prussics as backup for descending on double ropes. Until recently only 2 turns. Now I am using 3

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 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.

Love it. Thanks for going the extra effort in testing.

Arborists use something called a foot locking Prusik. And that is meant to go around two strands

Love it! Can’t believe it took me this long to find you!! Keep it coming!

Great to see this test, thanks HowNOT2

Loving it. Thanks for all the knowledge.

Definitely want more rescue gear content. Thank you so much for all you do.

Loved this! You guys have such great set-ups for testing, I will always watch these videos.

Fantastic content! I really appreciate these kinds of videos, as they are very relevant to my climbing practices. Thanks!

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.

Yes! Lots more of this, please! As someone who works on a rope rescue team, this stuff is fascinating!

Nice! Yes. As always, great stuff ryan. Keep pushing

I like all of your content but I love the rescue content!

Love the videos as a saddle hunter I appreciate the variety of information you put out.

Awesome. So much value for rope users.

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 content. As an engineering student, I am always excited to see your videos and ponder why these results happen. Thanks for the videos.

As an arborist, I really love that !!!! Thanks

Thats some jolly good content right there

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 any testing 👍🏼👍🏼

This is the kind of content I like as a patron!

This is what I come to this channel for! I love the nerdy stuff.

Awesome learning new stuff about two rope repel. Thx

Great video! I'd like to see the hollow block put through several rope configurations or different diameter accessory chords tested too

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

a very practical and awesome experiment 👍

Great video!

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 !

Epic safety services rope content!!

Appreciate the content 🤙

68,000 views in 10 months. Well on the way to 100k. Most excellent channel.

Just leaving a comment to help with the algorithm. Thank Ryan for all you do.

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!

Yes yes yes!! Want more of this.

Liked it. Great video!

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!

Love this kinda stuff!

I love the content focused on fire and rescue.

This was great, thanks

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.

Just the video I need today. What a coincidence!

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.

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!

That’s a great shirt idea, if not already in play. Heart beat of a Prusik

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

Hell yeah I like it!! The way I see it is _Content is Content_ and I'm just happy to get it. 👍👍

I like this content!

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. 👍

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.)

I would love to see prussiks of different material or other hitches. Great videos!

Very helpful video, please make more friction hitch testing, maybe autoblock or Klemheist?

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.

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.

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.

This is a great vid Ryan, is there any new bobby tshirts coming out?

Awesome Just the type of KZfaq I like

Loved it

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

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.

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.

Would like to see other versions of the prusik. VT, french, autoblock etc.

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

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.

"That's the heartbeat of a prusik!" Ha! Ryan's got jokes! =-D

I had this exact question when using a prussik as a third hand on a two rope rappel

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.

love it

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.

Awesome video! due to my long-ago NCRC cave rescue training including vertical rescue, I am familiar with using prussiks for haul-system brakes, safety catches and haul line ratchets. I also have used prussiks for ascending in vertical caves and related training. I was gratified to see things behave in your tests as I expected based on my training, education and experience, namely the greater the size difference between the prussik and the main/haul line, the higher the the loop's gripping force before the loop slips and releases some energy. The double rope main line tests behaved as I expected, i.e. behaved as a larger single rope. Possible future testing - how does a double main line behave with respect to the prussik if one strand is dynamic rope and one is static rope? If the two ropes are notably different sizes (e.g. 8mm & 11mm)? In a minimal gear self rescue situation, will prussiks cut from main line rope grip a doubled main line? Thanks!

Very interesting

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 😊👍

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.

I would be curious to see different mantle materials and weaves compared. Would be nice to know if there was a combination that could slip at a given load to prevent overloading equipment and or act as an indicator.

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.

great video, what if you pulled each rope in different directions?

I’ve always done that!!

I Like this

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.

Would some kind of a friction knot be a good idea to join to end ropes? Creating a bite on one end and wrapping a friction know around with other, keeping all system pretty much in line without sharp bend? Would it be stronger than other ways to of joining two ropes?

I like it :)

Would love to see the vt prusik tested

Why is your prussic diameter so big? Is it required for SAR? I use 5 mil or flat weave aramid (which grabs better). Both have been proven for me. Wet ropes, dry ropes, iced ropes and sandy ropes. I switch out the 5 mil when it starts to glaze which will happen after a while. Always under the device. Great content, I almost wish I could send you my setups and test those specifically!

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.

Have you done a test on two ropes where one of the tensioned ropes fail? The scenario would be a sharp edge in a TTRS above the prusik, single person load on the prusik wrapped around 2 ropes, the rope failure on sharp edge on 1 rope. Curious on the reaction on compression on 1 rope loaded the other slack and a single rescuer on the prusik.

Would be interested to see the tests on smaller ropes, i.e. lead climbing sizes like 8.6 or even smaller.

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.

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'm curious to see if you get a different result if you thread the rope through the anchor, instead of tying both strands in. Would the prussic grab one side before the other and cause the rope to start moving through the anchor? My prediction is that it wouldn't, but it would be interesting to see.

We got a tubular sling prusik slipping on a rope while tensoning. After sliding over a meter the sling was in parts melted and some sling resedue melted to the rope.

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).