Climbing Sling Myths

The image of a sling straight vs doubled vs girth hitched and it's relative strengths float around and is taken as doctrine. So we tested it.
BD 18mm nylon slings were 22kn MBS found at hownot2.store/...
Straight (broke 30%+ above MBS or the same as the chart)
Test 1: 29.02kn
Test 2: 27.62kn
Doubled (should get around 56kn)
Test 3: 53.58kn
Test 4:52.26kn
Wrapped 3x (should get around 56kn)
Test 5: 43.90kn
Test 6: 47.76kn
Doubled Twice (should get around 112kn)
Test 7: 78.72kn
Test 8: 82.82kn
Girth Hitch (should get 50% or 14kn)
Test 9: 25.22kn
Test 10: 23.48kn
Girth hitch with a 22kn MBS dyneema sling 15.48kn
Girth hitch nylon sling directly on hanger 9.50kn
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Intro
00:41 The Test
03:41 Reddit
07:29 Straight
08:02 Doubled
09:04 Wrapped
10:26 Doubled Twice
13:11 Girthed
15:02 Conclusion
17:05 Extra Test
18:48 Ending

[@HowNOT2]

Check out our new store! hownot2.store/

[@tomedinburgh4490]

"It's not that helpful when you're trying to research something just to find your own research". Aka the terrifying moment you realise you're the subject matter expert now.. Great work as always guys!

[@BryanHaddon]

Agreed, you guys are top of the field! Thank for doing the hard work to help us make the right choices!

[@DaddyBeanDaddyBean]

IT guy here. I had an absolutely baffling problem with a Windows server and was searching the interwebs for a solution, and came across a forum post describing my exact symptoms, underlying cause, and easy solution. It had been posted to that forum about 9 months prior ... by me.

[@daniilkulikov2489]

Thank you very much. An interesting idea from Bobby to test gear multiple times with 50% load and then break it! I am stoked with 45 K subscribers. This channel is GOLD!!

[@HowNOT2]

I am hoping to find someone with a cyclic loading machine that I could abuse on weekends of off days :).

[@cosmiceon]

Could you use a thermal camera on the slings to see the warmth build up during the strain test?

[@SnakebitSTI]

I'd be really curious to see that, especially in high speed. Stretching the fibers in the rope should cool them down, but friction will of course generate heat.

[@petr0news]

I reckon if the sling is just doubled, than it self equalizes the load easily, whilst when it's wrapped around than the wrap pinches the sling and force might not be distributed evenly, resulting in lowered strength, whith one part of the sling getting more load than the other. Seeing Your test is always an improvement for my intuition. Visual thinking is king.

[@Yellonet]

Yep, I was going to reply this as well.

[@katatat2030]

I think it's more about the friction between the strands as they pull, not any difference in load distribution. I don't really know the answer to this, but it seems like any tiny potential difference in equalization would be less significant than the change in friction

[@btodoroff]

This was my conclusion as well. If the sling was free to slide it would distribute the load to all eight strands evenly. In reality, as soon as you put tension on, the strands are locked in place on the bar and the shortest of the strands takes a higher load. It breaks while the rest of the strands are still at partial load, so you never get full utilization out of the other strands.

[@photomattmills]

Came here to say this. I think what's happening is a parallel to the test they did with the pulleys that didn't get the theoretical advantage. The friction of the looping over the shackle, and any friction between loops, causes the load to not get distributed evenly among the loops.

[@phreload1]

Hey, the reason for decreased strength is due to overlapping the straps. When they are under that much tension they will lock together rather than slip past each other. That will lock the length once the load gets high enough (well below MBS). Once you do that the shortest length will see a much higher load. The best way to mitigate that problem is to use longer test pieces so you can use larger shackles. This will allow you to avoid overlapping the test pieces.

[@spayced]

Yeah I would like to see a slightly longer one I think it would perform the same as the regular (shorter one.) I dont get why anybody expects that hitch to be half strength, its not THAT much different than a regular loop.

[@davewilson4493]

Also, if the issue was effectively having multiple pieces of slightly different [unloaded] lengths once everything locks, then presumably using a longer sling but keeping the shackles the same (so tending to keep the same absolute differences in lengths between pieces) and increasing the overall length between the shackles would mean the relative differences in [unloaded] lengths between the pieces would be lower, so the differences in load between pieces would also be lower.

[@AlphaGamingCa]

Came here to say exactly this but vid being 2y.o I first check comments. Glad to see some people with a brain here and experience here, shows thoses guy have no clue what they are doing.

[@davewilson4493]

@@AlphaGamingCa I guess it depends on what a viewer thinks they were doing. They did say they were inspired by the diagram (showing what were effectively "ideal" results for the first 4 arrangements), and that diagram was using a carabiner, which would end up with straps overlapping and resulting uneven load distribution. In the real world, not many people are going to carry around huge shackles to use in setting up a belay, so wouldn't end up with an ideal setup either.

[@amiller0185]

The wrapped sling introduces an angle to the attached leads of the sling, would be interesting to divide the measured breaking strength by the angle cosines to see if the straight tensile breaking force is close to the original double looped variation

[@trevdawg9182able]

Been watching your channel for a few months now, just donated! Really appreciate all the hard work you guys do, and the production value is insane!

[@lionknives3]

18:45 OK this is what I think! You guys are just awesome! Thank you so much for everything you do! Greetings from Austria!

[@LZmiljoona]

Hey, another Austrian

[@lionknives3]

@@LZmiljoona servus

[@diamondflaw]

The one that you’re calling a “double fold” is rigged incorrectly. It is instead a double loop - a spiral, not a fold. Look at the routing arrows near the drawing. If done correctly, it does indeed hang parallel and not at 90 degrees - it also does not lay on top of itself as much as how you had it.

[@iain_nakada]

Was going to comment this, doing it as drawn would also avoid the folded over strand in the configuration. I'm guessing you'd still have the unequal loading between strands / self-friction that's reducing the strength, but I'd expect a few more kN strength as a minimum. Great video, though!

[@w8stral]

While that is true, that is not how in Reality, one actually is able to USE said sling alignment.

[@diamondflaw]

​@@w8stral TIL that I apparently do not live in reality as proven by my use of this exact arrangement before with block and tackle to hoist significant loads.

[@w8stral]

@@diamondflaw If you are hoisting significant loads all the time, what the Hell are you doing using a paltry wrapped sling instead of a dedicated sling when there are superior methods for attaching a sling.

[@diamondflaw]

@@w8stral "all the time" was nowhere in my comment. Niether was any claim that it was the best, or even a smart solution. Just that it works.

[@TristanAnderson31299]

Loving these videos man. Thanks so much.

[@HowNOT2]

Glad you like them.

[@alextemus]

Yeah, as other people have brought up, There are basically two different factors that are not addressed in the original photo. 1. Friction is almost impossible to anticipate in situations like this. Friction between the strands and between the strands and the steel shackles, means that each strand will likely be stressed unequally (as seen many times on this and other channels, perfect equalization is a myth!). 2. There are angles on almost all of these set-ups and, while the angles are easier to account for with physics, they were clearly not accounted for in the original drawing/photo. The original sketch is basically the answer that you get in High school math when the problem says "There is zero friction in the system".

[@Lew114]

Manufacturers try to do every test the same way and control every variable for certification and QC. This is completely valid for its purpose. Theory ignores the fine details and makes different predictions. Also valid and expected. Both are useful for choosing gear and deciding how to solve a particular problem in real life. Having a healthy margin of error on individual pieces of gear and also having redundancy on things like anchors covers real world variations and the fact that a lot of my gear is old and a little worn. I think all this is why climbing accidents are almost always caused by human error and not by a piece of gear failing under loads we'd expect it to hold. It says a lot about the industry that makes our gear and our culture of safety. I love this channel because you do real-world tests. Things are a little messy and imprecise. You might pull a random sling off your rack. It's much more like real life. It's interesting to see just how much forces our safety systems can really handle e . It's educational because it encourages us to stop a think about stuff we take for granted. And it's just plain fun to watch you test stuff to destruction. Thanks!

[@ivan_bland]

Yessssssss. As an engineer I’m always curious how stuff works in the real world

[@Thesupremeone34]

As a mechanical engineering student The number is calculated from where 50% of samples fail when their entire cross section reaches a specific principal stress, something on the order of several tens of megapascals is usually where polymers fall. Pressure is force divided by area, so the force they rate to is that tens of MPa times the cross section area when in simple axial tension. From there, usually, there is a safety factor. For human use where someone's life is on the line, it's usually 4 to 5, hence why him falling in that video was 5KN but the strap supports 22KN of axial loading. This is entirely expected. Angled loading from wrapping is not axial, it creates internal sheer and axial loading. Sheer loading causes *massive* increases in the principal stress on a body. That's the first reason why all the wrapped portions failed early. The second reason for failure was the rubbing, which creates concentrated stresses at the contact point that are higher than the axial tension. The third reason for failure I can pull off the top of my head is the strain rate, how fast it is loaded. The faster a polymer is loaded, the less stress it can handle, and if your strap is loaded faster than the manufacturing test strap, it will fail before the test strap does. Seeing as your strap failed at 29ish but was rated for 22, I suspect you were slower than the test, which makes sense because the strap is designed to resist shock loading, not gradual loading. The heat you felt in the strap actually occured once it unloaded rapidly and the energy stored in the tension of the strap was released. Because the strap is permanently longer at failure than it originally was before testing, any energy stored in the elongation cannot be mechanically returned to the strap, and so is lost as heat.

[@TheSnowManKind]

Thanks guys, i used the informstion you brought here in a high-rise rope access safety meeting after a sling incident report, playin your video.

[@johannessporer]

A really helpful test would be a piece of dynamic rope put directly on a hanger with an overhand knot. I see this a lot at the crags in my area when a bolt is a bit too high.

[@igottajoe9294]

It would be interesting to see things break in slow motion. Seeing the failure mechanisms and locations would help understand why it fails. And how to improve our assumptions for the theoretical models to get them closer to reality!

[@juanmanuelfleitas4916]

Estimatedly speaking, it would reach 88 Kn, but theory teaches us that there are factors that are not taken into account when carrying out the tests, one of those factors is the friction that the material generates with itself, I think that would be the greatest difficulty. Excellent work.

[@alejandroperezhse267]

English is not my native language, but I'll try anyway to explain a little mistake I saw in the video. Girth hitch is supposed to halve the resistance of the sling if you apply a dynamic load (like in a fall). In static force application, as you get from a testing bench, it only takes out 20% of the total MBS, what is consistent with the obtained results. I'm an instructor for lifting equipment and you can find it in the label (what we call 'form factor' compared with that of direct pull) of an EN 1492 textile lifting sling. Hope that helps. Great video by the way. Regards from Spain.

[@FailedZerg]

As a climber with an extensive background in occupational safety. The similarities in standards between mountaineering and OSHA is absolutely delightful. You gentlemen did an absolutely wonderful job with this demonstration. I'm actually subscribing to you guys. :)

[@doaimanariroll5121]

My guess for the 4X wraps breaking early is that it’s not evenly pulling on the 4 length. Is locks itself tight, but 1 strand will inevitably be slightly tighter than the rest and will brunt more of the load.

[@chuckhightower2730]

Something interesting: I was retiring some rope by chopping it into sections with an axe over a stump, and the ends automatically melted/fused from the axe going through it. It doesn’t take a whole lot to melt these things.

[@junkmail4613]

Interesting. Never thought of rapid effects of a sharp versus a dull axe, and melting its way through (or not)! Wow.

[@vitodrolec9826]

I work a lot in industrial environment, working with static ropes and experiencing static falls. Once we calculated forces and even 2m fall can produce over 20kN and thats why we dont use hitches anymore at all.

[@otm646]

In what possible scenario are you getting 20 kN?

[@onebylandtwoifbysearunifby5475]

As Expected: load will NOT be shared equally on parallel members. Some load will be higher, some lower. Analogous effects are Parallel Electrical circuits. Some formulas for parallel resistors, or parallel batteries, will shed light on this effect. (Also, the more members you have sharing the same load, the wider the variation from average they become. Some members will feel almost no load, others will pick-up the slack and have higher loads. There is friction in the system, and the members cannot self-adjust their length to compensate for load variations between them.) Your results agree with calculated expectations; they were just using the wrong equations for their estimates. They needed a RMS (Root Mean Squared) term. Happens all the time. ... GOOD VIDEO 👍

[@PaulMansfield]

Great video, might be a life saver one day. I think KZbin suggested this because I watch Project Farm or Engineering Explained, as I've never been interested in climbing.

[@niezbo]

Interesting results! What is also interesting is that @09:10 upper-right side of a sling is tearing apart first (the inner side). It looks like the angles makes quite a difference, and probably its possible to achieve above 44 kN if sling would be aligned more perpendicular to the shackles.

[@paulwilkinson8785]

All of these test results are awesome. One crucial point is that the human body will disintegrate at any thing greater than 10Kn.

[@finnagerkvist2971]

In a simplifier analysis it makes sense that the girth hitch preserved strengh. Slings is rated to 22 kN, this means breaking tension in the material is half of that. if the girth hitch is considered as a single layer sling put across a double layered sling at an angle of 90 (hope this makes sense), 11 kN tension pr layer of sling would give a break pull force of double that. Nylon probably comes closer to that in real life compared to dynema, since nylon stretches more and distributes the loud more evenly on the width of the sling, whereas dyneema puts more load on specific parts of the sling. As small diameter carabiner probably also means more locally high tension and therefore lower breaking force.

[@justinmeyerr]

im sure its the friction against the shackles/other webbing as the sling stretches. the heat/friction increase is exponential so that's why the breaking point is lower than 88 I think.

[@nlb137]

I think the way the doubled up+ rigging can potentially be 'wearing on itself' is, if anything, *part* of a realistic test. If you can't reliably/quickly set up your rigging perfectly to avoid the problem, then any 'field use' isn't going to either, and the weakness just becomes part of the setup.

[@mfpmf]

you could've marked the pieces around the bars with a sharpie or something to know where it broke or melted and what might've been the cause of those effects. great vid I just came across!

[@cbat09]

Girth hitch: Climbing on Giant's Washbowl (Adirondaks NY) ~1980. Partner was leading, girth-hitched the eye of an in-situ piton with a 1" nylon sling (pretty standard for the time), placed a nut some feet higher, and fell from some more feet higher. Nut ripped, piton pulled, next nut down caught the fall. The shock load on the sling in the piton welded the girth hitch in to one blob of nylon in and around the eye of the piton. I think he still has that souvenir.

[@DanQuoLives]

Dan Merrick here. One issue I've had with testing is that the shackle pins rotate pretty freely. Rubbing seems to reduce sling strength pretty significantly so I am curious if the girth hitch would perform as well if the pin didn't rotate while loading. I think the result should be close to the same but I am not certain.

[@grahamheath9957]

I’m not sure that you would get the mechanical expected in the wrapped scenario as the wraps are touching and would add friction that would impact the spread of the load

[@bigmike-]

The answer to why all straps break below their theorized (or sometimes advertised) maximum is because of heat. And heat, as we know, is the enemy of plastic, which webbing is made from. As you put energy into the webbing by means of tension, the excess gets shed out of the webbing in the form of heat, and that heat *necessarily* changes the mechanical properties of the webbing. In theory, you could achieve a higher (e.g. much closer to theorized maximum) load on the straps by 1) Stretching them much slower, 2) cooling them as you're stretching, and 3) stretching them in small, stepped intervals. Now, obviously, this isn't really a *practical* way to achieve the maximum because there's no real-world use case where loads are slow and stepped *and* the webbing is being actively cooled at the same time. But.. that's how you'd get to the listed max's. You basically have to cheat and have super granular control the conditions that the webbing is being stretched under.

[@Citrus_6]

As a tower climber I find these videos quite informational

[@guardrailbiter]

Shirt Idea... front: picture of Bobby with text "Watch me whip" back: picture of a Hawaiian goose (aka nene) with text "Watch me nene"

[@zourin8804]

My first guess with the double-double over-wrap is that under tension, rather than all sections of strap equalizing the load, the tension instead locks the load onto the shortest/least stretchy sections causing an uneven load and a break at a lower strain. The sections can't slide past each other under tensision to equalize the load, thus, sub-theoretical performance.

[@jonettang]

Great work. The twist and the friction wrapped around itself.

[@adrianmilitaru4967]

Love having Bobby in the videos

[@DirtRoadLanding]

At 14:21, the results displayed of the dyneema break test were 15.48 KN with a LBf of 5279. Now, 1kn equals 225 lbs. So the results should have been that at 15.58 KN, the LBf should've been 3,483

[@tcal113]

On the Melting. Is it the fact that there is no sheathing around the nylon sling? The sling derives it's strength from the weave of nylon fabric. It needs to stay intact to stay strong. As the sling is pressed into itself it deforms the weave and weakens the sling integrity. Spanset has a sheath over it's strong bits so it is able to be stronger when used in basket or other orientation. The sheath protects the weave and the integrity of the fabric.

[@conchosewing]

love your channel! great videos about stuff my friends and I argue all the time :D cant wait for when you build the drop tower

[@HowNOT2]

me either. the materials are washed and sitting next to where it gets built. Larry's mother is not doing well and taking up a bunch of his time. It will get done between soon-ish and eventually haha

[@Myownchanelhere]

I service cellphone towers. I appreciate this video and will probably be sharing it with my coworkers. We use slings and ropes beaners and shackles and a lot of weight.

[@LeoBarnes]

Suggestion - put numbers along the strap so you can track what parts melted and where it broke, if it's not clear from the video

[@mattbaker1683]

Girth hitch or choke hitch in industry is 80% as the angles formed naturally form 120deg, with anything up to 90deg not requiring any calculations, not sure if this is internationally recognised or not, but it makes a mockery of the 'girth hitch is 50%' BS. And of course we use slings in anchors up to and sometimes including 90 degrees. Great work as ever, and regards to Bobby, get well soon. 👍

[@christopherberry8519]

ANY squeezing, folding, overlapping, disturbance is going to cause a weaker point and thus detract from doubling. Girth hitches are variable but essentially you're gripping the nylon onto the surface and running it flat. Thus your ideal condition for the girth hitch is kind of expected. The more interesting aspect was to see pinching and non-ideal set-ups severely affect the results.

[@carlman257]

All considered, the radius on the shackle is huge. That probably helps a lot. If it was around a carabiner or something a lot smaller diameter it would be worse.

[@walatalalaw]

On the 4 wraps it looks like one (or more?) section of the sling is twisted to enable the wrap, which must cause uneven forces on the sling. I’m guessing it puts more force on the edges of the sling than the center, which might be the reason why it breaks at a lower strength than anticipated. I’m not sure but I think it looks like it’s breaking in the twisted spot

[@SonnyKnutson]

I am one of the subscribed! Love this channel! :)

[@ryandavis2415]

Hi guys! I'm curious if you've load tested any of the integrated D ring belts that companies like 5.11 tactical carry ( like the Alta belt), I see ratings on the webbings in many situations or on similar buckles but haven't seen ratings on the D ring section themselves. I know they are not for climbing, but I'm curious whether they could even be considered as an options in emergency situations.

[@philipwindowcleaner]

The drawing is correct. You just basically proved that. Great video thank you for all the testing.

[@chriscox6463]

Super interesting! Have you done a test on a clove hitch?

[@HowNOT2]

No but that does sound interesting. I lock myself off with those all the time

[@SketchySam123]

@@HowNOT2 Love your videos! Can you guys break-test a clove hitch on a single-strand of dyneema? The team at SIET seems to be recommending that people build anchors by attaching to individual pieces with a single strand of dyneema on a clove hitch (see the video here: kzbin.info/www/bejne/aXXbY6ppap2ljbs). If my math is correct (and I've certainly been wrong before), a single strand of dyneema will break at about 12kN, and putting a clove hitch in that single strand will cause it to break at about half of that, or about 6kN. This seems like an unnecessarily weak link in the chain. The result would seem to be even less favorable with a single strand of 6mm perlon (which would also make for an interesting break test).

[@IOwnedGod]

I know I’m just one one lonely comment here in the couple hundred comments, but I really loved the one extra test on the hanger. I would have loved to see the nylon sling setup with the basket attachment straight on the hanger as well! If you have any more nylon, I personally am super curious about the end strength of that. I think most climbers would knot it- but honestly I don’t think it really matters for the test if there’s a knot in it. It’ll either break at the hanger far less than normal or not, regardless of a knot. (Of course- just my thoughts)

[@federicogonzalez8033]

The physics explanation for why the double double failed is because some parts of the sling were not directly in the direction of the force. They will also be pulled slightly to the side, so the total force is slightly more than the force in the axis of the piston. Approximating the highest angle any part of the sling is at to 25, this sling should've withstood about 80 kN of force.

[@Dodgerambo100]

I need to mention, that these slings not only used by climbers. We use such in Tree cutting. And we use carabines with a Max load of 4 tons (metric) and we busted 2 of them without loosing a sling. If you try to catch a brench or a stump with a waight of 200-1000 kilos (450-2200 pounds) you will reach quite a bit of pulling force. Even with a rope with 10% of cussion? (Dont know how to call it if the Rope Acts like a bungee.) Even if a Human cant get to the limit. Other aplications can do. And also the ware ant tare needs to be compensated till a certain point. Or Pulling trees out of the soil. With a 3 ton pully can Peak by 4 tons till the safetypins snap in that pulling device.

[@faunejrgensen3283]

This is a clear example of the the difference between theory and practise, never trust someone who only knows things in theory!

[@RedCoastLab]

Bobby at 7:58 cracked me up. You guys are awesome.

[@kamel6915]

In lifting gear girth hitch is considered 70%. That fit's perfectly for the dyneema.

[@Cerulean_Frost]

I have some training for using slings to lift things through my job. First off our lifting tools are marked with a Working load limit, this is often based upon the minimum breaking force with a 4 to 7 time safety factor. So a new sling that's used properly and marked with 10kN shouldn't break until it is exposed to a 40kN force. Anyway from what I was taught a girth hitch decreases the strength by 20%. So not all that much. And frankly pretty much what you saw in your test. But if the material it is hitched around has 'hard' edges the strength can fall by a lot, hard in this case meaning with a smaller than recommended diameter bend. For reference: A steel chain shouldn't have a bend sharper than 9 times the chain-links diameter, a steel wire shouldn't have a bend sharper than 6 diameters, and textile slings are more sensitive and should be marked with a minimum bend diameter. Also textile slings shouldn't be knotted and preferably not joined by another directly as the heat from friction weakens them. As for doubling up what we call a U form is straight up double the strength, but if those endpoints of the U isn't parallell and instead meet that is a 30% reduction in strength compared to the U form.

[@destructoau7526]

In an industrial application the girth hitch is seen as less then a full point of contact.

[@lightknightgames]

I think for the last one, you need to look at first failure. Those mini-pops I'd wager are at half. (It's putting more weight onto only one of the sides, so once the first failure happens, it puts a bit more weight onto the other side)

[@jacksonwhitcup1185]

my assumption is that the friction from the wrapping or doubling over creates stress concentrations in the sling, since the friction prevents it from stretching evenly. in addition, theres much more heat generated due to the friction over those sections, leading to failure below 2/4x. I would imagine to get the perfectly theoretical values, the surface of the sling would have to be frictionless.

[@jacksonwhitcup1185]

I wonder if for the girth hitch, the friction in the 'knot' keeps the full load going through the single strand at the hitch, so the forces are shared between the two strands.

[@mattm2207]

can you guys test the broken slings after they break by tying them back together with different knots?

[@shanewilson3653]

I see this "debunking" of the "don't knot a strap rule" and its always done static. The weakness is then the strap is loaded on a angle . The greater stresses due to unequal loading of the strap across its width cause lower load breaking points. It is a very real danger when something swings or moves laterally relative to the fixing points bar angle. For climbers this may be a issue when attaching to a fixed point (non-swiveling) or then two loads are using the same fixing point. The same thing applies to truck straps, winch straps and load slings. There is also a bunch of math relating to strap width vs thickness that can generally be summed up as the the wider it is comparative to its thickness the weaker it will be in lateral loading. Ropes being that they are round can be quite accepting to lateral loading at a knot interface. Also worth noting is that peak loading during a drop may be a lot more than measured on most load cells due to the speed of the loading pulse. the two analogies are snapping cable ties and ripping phone books. To snap a cable tie with a static slow load is hard, your fingers will get indented and maybe slightly hurt. but if you swiftly jerk the cable tie it may break with minimal hand stress due to the quick dynamic loading pulse. When ripping a phone book it is near impossible to pull it apart directly but then laterally loading one edge it will tear apart a lot easily. The same things happen to straps used for restraining, lifting and suspending loads. But honestly 28kN is a good margin for any sensible climbing.

[@Mechman0925]

A question more that a comment. Wouldnt the diameter of the object the sling loops around or wraps around have an effect on the breaking strength? Also what Ive gathered is that breaking strength is fundamentally different when looped vs. wrapped?

[@mausball]

The ratings in the image are theoretical maximums for a one dimensional circular body. The real world has a LOT of mitigation that must be applied, including friction against itself when wrapped, edge degradation against hardware, etc. Always figure in a safety factor.

[@CandC68]

Question about the stitching. It seems that one "row" of the stitching is a where some breaks occur. Knowing the webbing will stretch, wouldn't the stitching be less inclined to break if it were oriented differently? Like in sewing fabric that stretches, you do a zig zag stitch in the direction of the stretch. So, on your webbing, I'd try multiple zig zag stitches aligned to the direction of the pull. Also, the stitches in this video look pretty tight. Meaning that each time the sewing needle passes through the material it can cut or damage the webbing. And it seems tight enough that even ball point needles might not make it through. Just sayin..

[@StabBacker]

on the double double I think it might be the pulling shackle is a bit cramped for the sling to lay nice and flat. I also saw a fold on the second one(top row, one has a fold under the other) so those 2 points might cause it to create that "cutting" effect Bobby mentioned? Just a theory :)

[@ajlaursen]

you should get a thermometer gun to watch the surface temperature as it compresses. I bet sometimes the webbing is actually melting.

[@Freakismsyndrom]

I wonder if nylon performs better if you tie it under load - since it stretches so much otherwise, creating lots of friction. While in the experiment where you quadrupled the dyneema the sling was nice and parallel to the force applied, here you make the sling shorter, which puts the sling at an angle, so the actual force in the sling is higher than what you're pulling at. (Compare 2 times vs 3 times wrapped around). Also, maybe you got more than 4x by using 4 slings because the strain is applied slower compared to a single sling / a tied single sling?(stronger than a single sling, and longer than a tied single sling)

[@2sennheiser]

Just like when you braid 3 ropes together you only get 2 x the strength because the rope isn't straight and turns converts 30+ percent of the tensile load into shearing load . Same applies to knots in dyneema they usually reduce strength by 30-50 percent so splicing is important . Also the low stretch character of dyneema likely contributes to sudden failure like comparing a electrical tape to a box clear tape in character.

[@electrontube]

this is super useful information for belaying my African Bush Elephant. thanks!

[@dyvel]

The one that wraps around several times gets weaker because since it can't slide it acts as two individual pieces of rope, where one is going to be slightly shorter than the other .

[@younztitantube]

I imagine the double double doesn't generate 4x the strength because the friction at the folds. If they could be arranged in a snatch block setup, where the lengths are able to even themselves out as the load is applied, it would perform much better

[@daanschone1548]

Minimal breaking strenght of recreational climbing gear is 6 kN I believe. (Like a snapper loaded sidewards)

[@alexannal]

It was really interesting that the 4 times dubbed sling was not 4x the strength. Must be the interaction with the shackle. This is similar to a tractor tractor situation. You would think that 4 tiers over 2 would give you 2 times the lode. But because of the dynamic nature you can over lod one set resulting in problems.

[@joshmyer9]

Unsolicited input from an internet rando: It might be helpful to put tick marks down the sling, so you can track the wear pattern to where it was on the assembly. This would let you trace the "self-cutting" hypothesis a bit better. It might also demonstrate the stretchiness of nylon, among lots of other new measurements.

[@sailingsibongile]

11:18... The angle of the pull is not perpendicular to the bar for the outer straps, so I'd not expect the strength to be 4x, as there is sheer forces because of that off-centre pulling.

[@bchearne]

I reckon the strength of the loop being higher than rated is a standard scenario. It would be sort of crazy to make them exactly as strong as advertised because any tiny flaw would make it weaker than rated.

[@50StichesSteel]

The shirts look like rapper RIP shirts because Bobby fell off a mountain and only hurt his finger like a boss lol

[@fernandosanz4422]

Bobby, the O G

[@gardy90]

Random wild idea. What if you were to wrap it with say, wax paper, to see if you can cut down on the friction between the doubled parts of the sling.

[@eliasannila]

Idea for a video although not directly climbing or slackline related. I've been occasionally towing a van with an old climbing rope. Works really smooth but the rope stretches A LOT and I've been wondering if there's a chance it would break. Would be cool if you guys would put a dyno on and test what forces you actually get when towing.

[@allenwc]

very interesting channel. I stumbled on this by complete accident. Anyway, hit the button, so . . .

[@thehodgi1]

Unfortunately it’s not as simple as doubling or tripling the WLL depending on the amount of wraps. There’s many other factors that need to be taken into account, friction, angle and reeve factors are the main ones. Friction factor is quite obvious in these test, it’s around 5% decrease per wrap.

[@devendrasinghpanwar1406]

If I go with girth hitch. How many kg I will attemt in 2km ziplinein . Pls reply me?? I don't know good English.. ?? Pls reply me

[@bluehairsparklepants126]

Is it breaking due to the binding/bunching in the shackle? Looks like a slight bunching going on.

[@mattking3852]

So the yellow slings you tested look like 3/4" webbing. Maybe the illustrations are suggesting actual 1" tubular webbing? Im not sure it will get you to 112kN but it will probably get you to the 56kN. Technically you will never get an actual doubling of strength if you double it up or quadruple it up. The compression of the material at the carabiner will keep you from obtaining that double of strength.

[@cottonrobinson9401]

Notch has a 29 KN and I have seen one other that was listed on Amazon at 23 kn and a second listed as 23 kn however the weight listed was not 23 kn but instead was 22 kn

[@arnearne12345]

i love how they all look alot like the old style of lift starps we have here in sweden

[@chaikohmin]

Thanks for doing the experiment 👍👍👍

[@bjrnarbjrhusdal8963]

Someone prob commented on this; maybe the size of the bolt the girth hitch was hitched is big diameter comnpared to normal carabiner.

[@bjrnarbjrhusdal8963]

Oh sheit watched the rest of the vid now...

[@skilllessbeast7416]

If you have a 5kn fall on 20kn equipment. That's a safety ratio of 4. If people are in danger there usually is safety ratio of at least 10. Elevators have safety ratios of 20 and upwards. 4 is okay in climbing, because weight matters, but considering what is used elsewhere it really isn't much. And you mustn't forget that this 20kn are given for equipment that just came out of the factory and climbing is an outdoor sport. There are multiple reports of slings breaking in the wild. So always use your own slings.

[@FunkcijaDijagonale]

Not sure if there is a video somewhere, but what would happen to a nylon sling if you girth hitched it to your harness and then on the other side girth hitched it to a carabiner so it stays in place. The use is just for resting. Would the strength loss of two girth hitches double to end up somewhere 18/19kN?

[@2rfg949]

yeah as far as the smooth-melted-smooth-melted thing goes I think a breaking table isn't an identical simulation as it is a slower process than a dynamic fall situation induces, so heat can accumulate in the sling material and the metal. In a climbing fall this would be to a much less degree.

[@2rfg949]

you need to add another variable to the equation for time if you're looking at edge cases like prolonged forces that generate heat. something like kNs (where s is seconds). pretty sure the safety ratings are for drop tests and not for lifting scenarios. i guess for slack lining this could be quite relevant!

[@2rfg949]

i like your videos by the way. thanks for making them :)

[@justinmeyerr]

as for the girth hitch directly on the hanger. doesnt matter if its sharp, its about a different bend radius.

[@HowNOT2]

And the difference is?

[@justinmeyerr]

@@HowNOT2 pressure and friction on a small area. Obviously if it's sharper there's more 'slicing' at play. just for the record id never put anything soft directly on a hanger unless I absolutely had to 😛

[@Imageloading...]

Would a girth hitch cause progressive harm, as in Would it weaken over time?

[@TheEbanks7]

Is there a kevlar reinforced sling to attempt the hanger hitch with?

[@Crypt0keeper]

Bluewater ropes company makes 1in loop runners rated at 32 or 35kN.