Not sure if it's useful or even interesting, but you could try desheathing the ropes and pulling the cores and sheathes separately to see where the strength increase is coming from.
Not an expert by any means, but my understanding is that the main strength is the core strands. The sheaths main purpose is to protect the core from abrasion and being cut on edges.
@@cdans2202 often you can find literature that states its a 70/30 split of strength, the core being 70 and the sheath being 30 but both parts can be constructed differently to tune the desired properties.
I suspect that there is an actual difference in how they are made. If you calculate the breaking stress(MBS/area) you find that the 5 and 6 mm cords are very similar(.28), and the 7 and 8 cords also give the same number(.34). But those two pairs are different.
This was fascinating. One thing that popped out to me from the chart is that the safety margin for 6mm may be higher than that of the 7mm. So maybe...with the smaller diameter rope they have to add a higher safety margin, because it might not be possible to control the precision of the smaller fibers as well. Or in other words, if the strand spec is Xmm +/- .01mm or whatever, that's going to be a bigger percentage change for smaller strands than larger. Guessing here! Fascinating tests.
At 08:06 he is actually 100% right. It is very old knowledge and I'm even surprised no one in the comments shared the bit of trivia: That statement is known as Goodwin's Law, and is as old as usenet groups are.
@@kenmoum162 Noooo, you corrected me in the wrong way lol. That is a joke that tries to get people to reply like "It's not Goodwin's law, it is Cunningham's Law!!" Therefore proving the law is correct 😅
@@prgnify That is effing hilarious. But then what can you expect from a 75-yo cyclist and golfer who watches some goofs on the west coast breaking climbing gear. LOL
If they need to hit MBS 99.7% of the time, the larger leap between diameters seen on the manufacturer's rating could be the larger diameter being more consistent, while the smaller diameter may be more prone to inconsistency reducing numbers?
I also wonder if maybe the numbers for the smaller diameter are from an older material or manufacturing method, and the increased strength wasn't carried into an increased MBS because it was a side effect or unintentional
@@briancarr9663 sorry, I wasn't more specific because I did actually mean that magnitude of leap because the manufacturer rating and the ones tested here. The leap is there, but not as massive, and I wonder if this is because the smaller diameter is just a little less consistent for establishing an MBS.
I think you missed something in the fill area calculation with different-sized ropes. Rope diameter is including the outside sleeve, of which the thickness differs and allows for different amounts of nylon ropes inside. And 12.86 KN isn't lower than 13 KN in significant figures.
Many years ago I read, or somebody told me, that 7mm and above is classed as climbing rope (twin presumably) while below it is accessory cord. Rope is constructed to higher standards than cord (not sure what that means) so the result is the sudden jump in performance. I always thought the colored tracer strands were for dating ropes.
Really interesting and great video! It would have been great if you cut the different cords and measured the thickness of the sheath and/or counted the number of nylon strings in the core. This could explain the initial jump. Also super nerdy: it would be interesting to test single strands of nylon in different cords to see whether they are all the same and if yes(no?) you could infer someting about the strength of the cord/rope just by the number of nylon strands.
I think the odd numbers are likely coming from the way you can’t scale down all components equally ie the sheath might become thicker in proportion to the core as you lower the diameter. I am just assuming here but could explain.
This is a realy important thing to understand generally ....... Increases in diameter of round things. One way or another this applies to everything round and every propertly that round thing has. AND, it might be more than you think.
Wrapping rope 3 or more times around a tree or round pole is called a "tensionless hitch" and doesn't reduce the strength of the rope as you demonstrated. We used tensionless hitches around extra super good enough trees as anchors.
Are all those nylon accessory cords? in Italy it's very common to find 5.5mm accessory cord with kevlar core and given its high strenght(18kn usually) it is used for a lot of different purposes, but looks like in the USA isn't used so much.
I was going to ask about Bluewater's Titan cord which has the HMPE. Having been out of climbing for 20 years and just getting back into the game, Im amazed how thin a line can be used as a cordellete.
I use a 7mm for emergency repelling because i can carry a decent amount and not have it fill my pack when in the woods. Definitely makes for a quick decent but it holds just fine.
I'm going to guess the size of microscopic defects stays the same, but when the diameter increases they become relatively smaller and don't cause as significant of a stress concentration
8:05 the colored string inside is date of production. You can mail the manufacturer with the model of rope that you have nad color of the internal string at he will tell you what year it was manufactured.
Most rope manufactures, run a ten year color strand cycle. Different color every year, then repeat/recycle the colors. There's only so many colors to choose from lol.
Hey Ryan, can you test the strength of a nylon sling with a bowline on a bight, as used in the fixed point anchor? I'm curious to see if it would slip under a fall and at what force the double loop would break.
When you show the graphs, the force / load is the x axis. Is the Y axis time, or distance pulled? Do the hydraulics move at roughly constant speed, or do they slow down as load goes up? Elongation vs force would be interesting (if the distance pulled is being recorded along with the load cell outputs) when modeling systems...
hey @HowNOT2 I see this 5 mm dynema accessory cord from blue water (mbs:13.5kn on a single strand) What are your thoughts on using this as an anchor building material given its looped with a tripple fisherman's?
Have Ryan and the team done testing of individual kermantles from old ropes? I've been re-using this stuff as strong string (works great) and wondering what the approx load each strand can take
Ryan, Yet another fascinating clip. On my first Mountaineering trip to New Zealand, I met a German guy who was soloing ...super lightweight, and he only had a 20m piece of 6mm to abseil with ( this was 1985 and long before Spectra or Dyneema was readily available..so his was plain old nylon 6mm )....I was horrified at the thought but he was adamant it was entirely adequate for a static abseil force. Seeing how the "Bollard" system works in collaboration with your snazzy breaking machine makes me wonder?? What about the knot we used to use in Scouts...the "Round turn ( or two or three ) and two half hitches. Theoretically, if you wound a few turns around a nice fat carabiner, and then finished with some half hitches, you could dramatically increase the working strength of your rope. I know that normally, with a rope between say 9 and 11mm you already have miles of extra strength anyway. Have you tested a round turn and half hitches yet?? compared to a figure 8 or even a clove hitch. Also, I note that most ropes break IN the knot, and that's largely due to the rope cutting itself. I have sometimes placed a carabiner WITHIN a knot for two reasons...firstly so it's way easier to get un-done, and as a bonus, I believe it's stronger. TRUE or False??
This is great stuff. It feeds my brain. Keep it up! The summary chart that you post at 8:25 shows a blur in the sizes for each run. Is this a real thing? do the diameters vary slightly, or is this an intentional typo to make it easier to see the three runs in the chart?
To compare cross sectional area of the loaded portion of the cord you also have to consider that the core isn't perfectly solid. It's circular strands butted up against each other. There will be gaps. The size of those strands dictates the amount of the area that is gaps versus strands. So the real jump in area you are seeing might not be the simple area of the circle with a diameter equal to the rope. The advertised diameter is probably also with the sheathing. There is also elongation that would reduce the cross section of each of those strands which is the difference between real and engineering strain that would come into play when considering different strand diameters. The sheathing might also begin to squeeze inward which would add to the load applied, which would also possibly change with sheathing diameter.
Did you guys count the number of strands in the rope? Assuming all ropes have strands with the same diameter its possible that between 6mm and 7mm, while the area of the rope only goes up by 36% the number of strands that make the rope can go up by 70% (or 55% by your measurements). And between 5mm and 6mm the area of the rope goes up 44% but the amount of strands it has can only go up only by 35%.
It wouldn't surprise me if there was a closer relationship between the areas and the MBS if you measured it under load (ideally close to what it would break at, but that's maybe dangerous
From a mathematical and engineering stand point its pretty obvious why the increase in strength is not linear with respect to diameter increase. The formula for cross sectional area strain (the area under tension or tensile load) of a medium (rope, in this case) is what determines the tensile strength of the medium. So the larger the area the larger the tensile strength and thus for a circle or rope, the area is related to the diameter via A=Pi*(d^2/4) If you notice the diameter term is squared which means that the strength cannot increase linearly with respect to linear increase in diameter. Probably doesn't necessitate the INSANE title, but it is very cool and unintuitive how tensile strength of rope works.
Swiss machine Ueli Steck used to rappel off of 6mm accessory cord. He's dead tho. Nothing to do with accessory cord failure, but probably his general attitude to risk-taking?
Ok, I know this is a year later, how the different colored "tracer thread" works. Most manufactures have a "shelf " life of ten years for there rope. Each year has a different color thread. After ten years they change the color sequence for the next ten. This is for rope inspection, to determine the age of a rope. This is for your own peace of mind, and also for accident investigations. Some industry's, fire, rescue, policy's have a five year "working" life replacement.
I've found the fraction of sheath to central (core) fibers varies a lot in cords. The sheath, measured separately, often amounts to about 40% of the strength. When the sheath is on the core, it has a higher lay angle, so is probably weaker, but it really serves to hold the core strands in place. My abrasion tests wear through the sheath rather quickly. Again, great work, so we don't have to speculate thanks to you. I would recommend getting a jeweler's scale (0.01g accuracy), and weighing a small section of the rope tested, then weigh the same length of sheath without the core fibers.
So what is your (and anyone else’s) preferred diameter for cordalette for anchor building? Are brands vastly different? I just watched a vid in which the guy’s cordalette looked much more smooth, supple and “nice?” than mine. Wondering if it is brand or material. I’ll see if I can find the vid and edit in a link.
Both Tendon and Edelrid (Powerloc pro SP) make very high kN cords that are ridiculously supple. I regularly use both brands in 6mm (10/9kN) and 7mm (12/13kN). I've not found any better.
For my cordalette’s I favor using at least 7mm chord. Unless using a high strength tech chord anything below 7mm isn’t strong enough for me to be comfortable using it. There are times where a thicker cord would make sense/become necessary. The first that comes to mind is for a team of three climbers that are hauling heavy loads. In that case I would size up to at least 8mm maybe even 9mm. If I was using 6mm accessory cord (which would be for prussiks, not anchor building) I think Petzl and Maxim both have pretty high ratings for this diameter. Bonus points for cords that are made in the US or Made in Europe (not outsourced to China). Looking up as many companies as you can to compare the ratings for the diameter of cord you’re after can be illuminating due to the varied results (the maker of the strongest 5mm cord won’t necessarily have the strongest 7mm or 8mm cord). Which is why its not as simple and easy as "brand X has the strongest accessory chords period”. Also I wouldn’t worry about what a cordalette in a video looks like, whatever catches your eye may not be indicative of anything relating to strength/durability. You will certainly feel some variation between the various brands and options, some are stiffer/tighter and others are looser/supple. One alternative option to chords altogether that Ive been liking lately is the sewn web-o-lette type anchor sling. I have the Metolius web-o-lette style anchor sling, the longer of the two sizes, that I really like. Some of its advantages: integrated pouch that it stuffs into (vs having to coil it). This is really convenient & fast plus it provides protection from UV damage as well as abrasion. Also the fact that it has sewn loops on each end (reinforced/double layered) instead of relying on a knot or knots. This allows for it to meet the 22kN standard for sewn runners and it eliminates the concern over knotted dynema’s tendency to slip/untie when under load.
@@brianrodman1033 thanks for the thorough reply. With the sewn loop products you mention. Does each loop go direct to an anchor point? If I’m picturing that properly, those two points would have only one stand so there isn’t a redundant shelf. Shelf isnt really essential in a usual non-big wall setting but I’m curious if what I’m picturing is how you’ve used it.
I think it wouild have been interesting to see a certain length of each cord tested deconstructed, then the sheath and core components weighed to get an idea of sheath percentage. Perhaps not the most accurate way of doing it, but this along with examining the actual construction and braiding of each cord might have brought more insight about the difference in strengths
Let x denote the area of a circle: x = π r^2. Take logs: log x = log π + 2 log r then differentiate (d log x) / (d log r) = 2. Log differences are approximately percent changes for small percent changes hence an approximate 1% increase in radius (or diameter) leads to a 2% increase in area. An ideal 6mm diameter circle has an area of 28.3 square mm while a 7mm diameter circle has an area of 38.5. 7mm is about 16% larger than 6mm, but a 7mm diameter circle has about a 36% larger area (which is close to the approximation of twice as big a percent change).
Isn't it because nylon strands come in relatively thick strings, and maybe going from 6mm to 7mm you can suddenly fit 2 more strings, rather than just one more for 5mm to 6mm because of the geometry of the cross-section?
High tensile strength cords even tho suitable for repelling are a disadvantage when distributing forces. I would not like to use a HTS 6mm and have to try and arrest a fall or even worse a get caught in a bite or up against a solid surface. A lot of force pushing against my meat: last thing I want is to get cut/crushed.
I want to get a Scream to have a device that’s intended for rappelling on accessory cord down to 6mm or 7mm in diameter. Good to hear that it works well for you. Are there any other devices that you would recommend checking out in addition to the Scream. Also any downsides to using the Scream to look out for?
@@brianrodman1033 the Scream is a simple binding plate so it is more fiddly to use than a standard tube device. It also has 4 modes that it can be used in creating various degrees of friction on different sized ropes. They are not the easiest to discern. All this is to say that it’s not the simplest to use. Gotta practice with it before deploying it in anger. As to other devices to use, I picked up the Petzl RAD system, containing a Tibloc and MicroTraxion. If you don’t already have an ascender, and don’t use them often, pick up a Tibloc or two. On a recent trip to the Alps, my guide and our crew used some purple static 7mm line for everything. I felt perfectly comfortable rappelling using that. It felt plenty substantial. The Petzl Rad line, on the other hand is spooky thin. Were it no for the purposefully high friction sheath and low compressibility of the rope it would be even creepier. I get a feeling that normal accessory cord won’t perform as well as a dedicated rappelling line as the ones designed for the task. Petzl suggests using beam cross-section type HMS ‘biners when rapp’ing on the RAD line. This probably applies to all other similar ropes. They are higher friction than round stick ‘biners. Adding multiple into your normal rappel device adds friction. Lastly, if you haven’t/don’t already, learn and practice how to climb a rope that you are suspended from. An ATC Guide/Petzl Reverso/most binding plates like the Grivel Scream can easily be turned into a progress capture device while on an extended rappel. Combined with a second prussik cord, a double length sling, and 2 extra locking ‘biners you have a very versatile system that gets you up and down the rope with zero drama. Also learn the Texas Prussik technique of ascending a rope with two prusssik cords. Always keep that kit with you. Lean how to rappel without a device. The Munter Hitch can save you or your partner when you inevitably drop your Rappel/Belay Device. Personally I would consider 2 double length slings, 3 locking HMS carabiners {Petzl Attache are favored by me}, 2 prussik cords, a cordalett, and a guide mode belay device should always go out into the field with you as your Emergency Rappel Kit. Add in a Tibloc and MicroTraxion with their accompanying carabiners, and you also have basic ski mountaineering kit, too. As to other devices designed for use on such thin cords, I know of none.
I've got big bollards, I've got big bollards, They're such big bollards, And they're dirty big bollards, And he's got big bollards, And she's got big bollards, But we've got the biggest, bollards of them all!
Suggestion: full strength tests of dynamic ropes. Beal opera 8.5, edelrid Swift protect 8.9, edelweiss performance 9.2, mammut crag lines 9.5, sterling vr9 9.8 for range recommendations
John Harlin is generally reputed to have died on the North Face of the Eiger whilst jumaring on a 6mm fixed rope. 6mm is nice and light and compact to carry if your going to fix thousands of feet of it, but like any rope it frays if you leave it out in a storm and then the slender but arguably adequate safety margin that it provided is gone! It's better than you mothers washing line though!
12.86 kN is not below MBS if it is specified as 13 kN, since 13 kN is only given with two significant figures. 12.86 kN is 13 kN with two significant figures.
Im not a physicist or anyone who understands in depth the structural integrity of ropes, but however i just have some sort of feeling that the tensile strength of the rope may vary depending on the length of rope used. Id recommend testing with larger distances and compare to find out if true.
The reason the jump from 6mm to 7mm that you measured was lower than the manufacturer's specs showed was clearly that the 6mm ropes you tested were simply too strong. All but one sample broke over MBS, but the smaller diameters were higher over their MBS than the larger ones.
the strength increased almost is exactly in proportion to the cross sectional area. the larger the cross section of fibers, the stronger it is. it becomes obvious if you plot area vs. strength on a graph. No mystery.
Neither the relative increase of the diameter *nor of the cross-sectional area* should have been compared to the relative increase of the breaking strength for meaningful results. It is the actual mass of the material per unit length (prestretched by some small nominal amount - I think 5 kg equiv is the standard when measuring the nominal diameter) that matters. 🤦♂️ But kudos big-time for using mm squared instead of "sixteenths of erected other roughly cylinder-shaped body" standard units.
you may be making a mistake in assuming the sheath is the same size. you need to check the sheath to see if it increases in thickness. As a Ski patrol we used 6mm rope to rappel off of a chair lift.
Watch a few more wand wait for him to saw “sewn” or “known” etc and you’ll realize he would be hopelessly unable to to a Trump impression. Lol (he has called this out on a video so I’m not being a jerk.)
Great video, but I wish you would not classify cord by 'diameter'... cord should be classified by lineal weight.. then you can plot strength (kN) VS linear weight (g/m)..
@@francismartinevans think his premise is manufacturers label this in diameter, this is sold and discussed in diameter, and the channel is usually about use in the field and by consumers. Wouldn't make sense for him to not classify cord in diameter.
@@zacharylaschober the manufacturers seem to tell so many 'pork pies' about rope/cord diameter... hence i think weight per metre is a more scientific/geek way to 'classify cord'... im convinced the testers would see a different data / trends when plotting their results... especially when you start weighing your ropes, and find your 8.9mm and 10.5mm weigh so similar
@@francismartinevans not disagreeing there, more explaining why the phrase "I wish you would not classify cord by 'diameter'" is more to do with how manufacturers and the public classify cord, and more of a "have you tried classifying cord by X" might be more appropriate for the channel.
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7 is so strong because 7 ate 9
10 is the strongest, he survived 9-11
Not sure if it's useful or even interesting, but you could try desheathing the ropes and pulling the cores and sheathes separately to see where the strength increase is coming from.
Sounds interesting, probably not useful but it'd still be cool to see.
Quite interesting, questionably useful. Sounds like RUclips
Not an expert by any means, but my understanding is that the main strength is the core strands. The sheaths main purpose is to protect the core from abrasion and being cut on edges.
@@cdans2202 often you can find literature that states its a 70/30 split of strength, the core being 70 and the sheath being 30 but both parts can be constructed differently to tune the desired properties.
Interesting vid.
I suspect that there is an actual difference in how they are made. If you calculate the breaking stress(MBS/area) you find that the 5 and 6 mm cords are very similar(.28), and the 7 and 8 cords also give the same number(.34). But those two pairs are different.
This is such a professional setup. Great consistent results and impressively reproducible.
This was fascinating. One thing that popped out to me from the chart is that the safety margin for 6mm may be higher than that of the 7mm. So maybe...with the smaller diameter rope they have to add a higher safety margin, because it might not be possible to control the precision of the smaller fibers as well. Or in other words, if the strand spec is Xmm +/- .01mm or whatever, that's going to be a bigger percentage change for smaller strands than larger. Guessing here! Fascinating tests.
At 08:06 he is actually 100% right. It is very old knowledge and I'm even surprised no one in the comments shared the bit of trivia: That statement is known as Goodwin's Law, and is as old as usenet groups are.
Well, it's Godwin's Law, and applies to calling someone Hitler....🤣
@@kenmoum162 Noooo, you corrected me in the wrong way lol.
That is a joke that tries to get people to reply like "It's not Goodwin's law, it is Cunningham's Law!!"
Therefore proving the law is correct 😅
@@prgnify That is effing hilarious. But then what can you expect from a 75-yo cyclist and golfer who watches some goofs on the west coast breaking climbing gear. LOL
If they need to hit MBS 99.7% of the time, the larger leap between diameters seen on the manufacturer's rating could be the larger diameter being more consistent, while the smaller diameter may be more prone to inconsistency reducing numbers?
I also wonder if maybe the numbers for the smaller diameter are from an older material or manufacturing method, and the increased strength wasn't carried into an increased MBS because it was a side effect or unintentional
You also saw the same phenomenon (just not quite to the same magnitude) in the actual tested numbers in this video though. So I don't think that's it.
@@briancarr9663 sorry, I wasn't more specific because I did actually mean that magnitude of leap because the manufacturer rating and the ones tested here. The leap is there, but not as massive, and I wonder if this is because the smaller diameter is just a little less consistent for establishing an MBS.
Good hypothesis for 6 vs 7 In isolation, but not for why 6 vs 7 breaks the pattern established by 5 vs 6 and 7 vs 8.
@serges5681
As Ryan alluded to there is probably a change is weave at6/7 making 7,8 comparable and 5,6 comparable and 6,7 brake the pattern.
Color tracer is for batch tracing.
Thanks Ryan.
I think there is a video in the channel "hard is easy" with Mammut engineers and they say it is for the year of manufacture
Hell yeah, love seeing you break stuff for data.
Ryan you're such a legend. Always bringing clarity and interesting topics with a true excitement. My fav channel for sure! Thanks for a good work!
I think you missed something in the fill area calculation with different-sized ropes. Rope diameter is including the outside sleeve, of which the thickness differs and allows for different amounts of nylon ropes inside.
And 12.86 KN isn't lower than 13 KN in significant figures.
Many years ago I read, or somebody told me, that 7mm and above is classed as climbing rope (twin presumably) while below it is accessory cord. Rope is constructed to higher standards than cord (not sure what that means) so the result is the sudden jump in performance. I always thought the colored tracer strands were for dating ropes.
Really interesting and great video! It would have been great if you cut the different cords and measured the thickness of the sheath and/or counted the number of nylon strings in the core. This could explain the initial jump. Also super nerdy: it would be interesting to test single strands of nylon in different cords to see whether they are all the same and if yes(no?) you could infer someting about the strength of the cord/rope just by the number of nylon strands.
Thank you for the videos. Super useful to know especially for people new to climbing and building anchors !
I’m impressed with how effective bollards are at holding a rope, while not reducing the rope’s breaking strength.
I think the odd numbers are likely coming from the way you can’t scale down all components equally ie the sheath might become thicker in proportion to the core as you lower the diameter. I am just assuming here but could explain.
This is a realy important thing to understand generally ....... Increases in diameter of round things.
One way or another this applies to everything round and every propertly that round thing has.
AND, it might be more than you think.
Wrapping rope 3 or more times around a tree or round pole is called a "tensionless hitch" and doesn't reduce the strength of the rope as you demonstrated.
We used tensionless hitches around extra super good enough trees as anchors.
I just found out that apparently I am a niche nerd because this examination was very interesting and the results enlightening. Great stuff Gents. 👍
Are all those nylon accessory cords? in Italy it's very common to find 5.5mm accessory cord with kevlar core and given its high strenght(18kn usually) it is used for a lot of different purposes, but looks like in the USA isn't used so much.
We tested the 5.9mm power sterling rope as that is used sometimes. You can see that here ruclips.net/video/yA4gcc2ExsQ/видео.html
I was going to ask about Bluewater's Titan cord which has the HMPE. Having been out of climbing for 20 years and just getting back into the game, Im amazed how thin a line can be used as a cordellete.
Interesting video, thank you...
Yess would love to see break tests of the rad line and edelrid rap line as well!
Looking forward to the next video about the climbing gear !!!
Yeah rappelling on a Petzl Rad line is scary especially if you rappel into a crevasse.
We are also interested in 6mm glacier travel rope like the Petzl radline.
I have some old technical information from Kong on how to rappel on 5mm rope with their descenders.
All the best
Great video as always Ryan, thank you for uploading! 👍👍
I use a 7mm for emergency repelling because i can carry a decent amount and not have it fill my pack when in the woods. Definitely makes for a quick decent but it holds just fine.
You could test the inner cords separately to see if the size of rope provides different inner cords.
THANKS!
I'm going to guess the size of microscopic defects stays the same, but when the diameter increases they become relatively smaller and don't cause as significant of a stress concentration
8:01 this man is adjusted
Did that 6mm comparison video happen? Im looking at getting some soon and would be keen to learn a bit
Area calculation checks out.
8:05 the colored string inside is date of production. You can mail the manufacturer with the model of rope that you have nad color of the internal string at he will tell you what year it was manufactured.
Most rope manufactures, run a ten year color strand cycle. Different color every year, then repeat/recycle the colors. There's only so many colors to choose from lol.
Wondering if the sheath is constraining the available cross section for the strands. Maybe?
Red strand should be a year of manufacture indicator changing every year and looping every 10 years
Hey Ryan, can you test the strength of a nylon sling with a bowline on a bight, as used in the fixed point anchor? I'm curious to see if it would slip under a fall and at what force the double loop would break.
Ryan and I tested that with dyneema, not nylon. It broke at 20.4 kN. #SuperGoodEnough.
When you show the graphs, the force / load is the x axis. Is the Y axis time, or distance pulled? Do the hydraulics move at roughly constant speed, or do they slow down as load goes up?
Elongation vs force would be interesting (if the distance pulled is being recorded along with the load cell outputs) when modeling systems...
hey @HowNOT2 I see this 5 mm dynema accessory cord from blue water (mbs:13.5kn on a single strand) What are your thoughts on using this as an anchor building material given its looped with a tripple fisherman's?
Nerd question.
What is the % increase excluding the sheath?
Dose the sheath thickness / percentage change with diameter?
Have Ryan and the team done testing of individual kermantles from old ropes? I've been re-using this stuff as strong string (works great) and wondering what the approx load each strand can take
7:16 eye wood lov to send yea a bunch of three strand ropes to test with different knots and splices
It'd be nice to know if they change the sheath thickness between sizes.
You should weigh the amount of core vs sheath for the different diameters to see how the ratios vary across the different diameters.
Soooooo would it be reasonably safe to use a 7mm cord to build an anchor with for lead sport LRS falls??? Asking for a friend lol
Do you have a video on quads but with different size diameters?
Ryan,
Yet another fascinating clip. On my first Mountaineering trip to New Zealand, I met a German guy who was soloing ...super lightweight, and he only had a 20m piece of 6mm to abseil with ( this was 1985 and long before Spectra or Dyneema was readily available..so his was plain old nylon 6mm )....I was horrified at the thought but he was adamant it was entirely adequate for a static abseil force. Seeing how the "Bollard" system works in collaboration with your snazzy breaking machine makes me wonder?? What about the knot we used to use in Scouts...the "Round turn ( or two or three ) and two half hitches. Theoretically, if you wound a few turns around a nice fat carabiner, and then finished with some half hitches, you could dramatically increase the working strength of your rope. I know that normally, with a rope between say 9 and 11mm you already have miles of extra strength anyway. Have you tested a round turn and half hitches yet?? compared to a figure 8 or even a clove hitch. Also, I note that most ropes break IN the knot, and that's largely due to the rope cutting itself. I have sometimes placed a carabiner WITHIN a knot for two reasons...firstly so it's way easier to get un-done, and as a bonus, I believe it's stronger. TRUE or False??
This is great stuff. It feeds my brain. Keep it up!
The summary chart that you post at 8:25 shows a blur in the sizes for each run. Is this a real thing? do the diameters vary slightly, or is this an intentional typo to make it easier to see the three runs in the chart?
Wish you had done it with Knotts vs bullards.
I've rappelled from a 5mm accessory cord. It was not fun😅
To compare cross sectional area of the loaded portion of the cord you also have to consider that the core isn't perfectly solid. It's circular strands butted up against each other. There will be gaps. The size of those strands dictates the amount of the area that is gaps versus strands. So the real jump in area you are seeing might not be the simple area of the circle with a diameter equal to the rope. The advertised diameter is probably also with the sheathing.
There is also elongation that would reduce the cross section of each of those strands which is the difference between real and engineering strain that would come into play when considering different strand diameters.
The sheathing might also begin to squeeze inward which would add to the load applied, which would also possibly change with sheathing diameter.
Did you guys count the number of strands in the rope?
Assuming all ropes have strands with the same diameter its possible that between 6mm and 7mm, while the area of the rope only goes up by 36% the number of strands that make the rope can go up by 70% (or 55% by your measurements).
And between 5mm and 6mm the area of the rope goes up 44% but the amount of strands it has can only go up only by 35%.
The red strand might be a wear indicator like the green rising slings have
I just want to know how thin a cord I can use in a tibloc and what they slip or break at.
Twin 6’s all day. (Skitouring) not hangdoggin around. But with a reverso, no worries
It wouldn't surprise me if there was a closer relationship between the areas and the MBS if you measured it under load (ideally close to what it would break at, but that's maybe dangerous
From a mathematical and engineering stand point its pretty obvious why the increase in strength is not linear with respect to diameter increase. The formula for cross sectional area strain (the area under tension or tensile load) of a medium (rope, in this case) is what determines the tensile strength of the medium. So the larger the area the larger the tensile strength and thus for a circle or rope, the area is related to the diameter via
A=Pi*(d^2/4)
If you notice the diameter term is squared which means that the strength cannot increase linearly with respect to linear increase in diameter. Probably doesn't necessitate the INSANE title, but it is very cool and unintuitive how tensile strength of rope works.
Smashed the like 👍🏼🤟🏼
Its a surface area problem. Also why trees grow substantially more the older they get.
Swiss machine Ueli Steck used to rappel off of 6mm accessory cord. He's dead tho. Nothing to do with accessory cord failure, but probably his general attitude to risk-taking?
Good stuff
mazamas!
What happens if rope is soaking wet?
le fil de couleur interieur c'est pour la date de fabrication, selon la marque et le modéle!
Maybe get a rail system where you can lock down the Anker points?
Ok, I know this is a year later, how the different colored "tracer thread" works. Most manufactures have a "shelf " life of ten years for there rope. Each year has a different color thread. After ten years they change the color sequence for the next ten. This is for rope inspection, to determine the age of a rope. This is for your own peace of mind, and also for accident investigations. Some industry's, fire, rescue, policy's have a five year "working" life replacement.
I've found the fraction of sheath to central (core) fibers varies a lot in cords. The sheath, measured separately, often amounts to about 40% of the strength. When the sheath is on the core, it has a higher lay angle, so is probably weaker, but it really serves to hold the core strands in place. My abrasion tests wear through the sheath rather quickly. Again, great work, so we don't have to speculate thanks to you. I would recommend getting a jeweler's scale (0.01g accuracy), and weighing a small section of the rope tested, then weigh the same length of sheath without the core fibers.
So what is your (and anyone else’s) preferred diameter for cordalette for anchor building? Are brands vastly different? I just watched a vid in which the guy’s cordalette looked much more smooth, supple and “nice?” than mine. Wondering if it is brand or material. I’ll see if I can find the vid and edit in a link.
Here is the video ruclips.net/video/9MLXY_UbjRQ/видео.html
Both Tendon and Edelrid (Powerloc pro SP) make very high kN cords that are ridiculously supple. I regularly use both brands in 6mm (10/9kN) and 7mm (12/13kN).
I've not found any better.
For my cordalette’s I favor using at least 7mm chord. Unless using a high strength tech chord anything below 7mm isn’t strong enough for me to be comfortable using it. There are times where a thicker cord would make sense/become necessary. The first that comes to mind is for a team of three climbers that are hauling heavy loads. In that case I would size up to at least 8mm maybe even 9mm. If I was using 6mm accessory cord (which would be for prussiks, not anchor building) I think Petzl and Maxim both have pretty high ratings for this diameter. Bonus points for cords that are made in the US or Made in Europe (not outsourced to China). Looking up as many companies as you can to compare the ratings for the diameter of cord you’re after can be illuminating due to the varied results (the maker of the strongest 5mm cord won’t necessarily have the strongest 7mm or 8mm cord). Which is why its not as simple and easy as "brand X has the strongest accessory chords period”.
Also I wouldn’t worry about what a cordalette in a video looks like, whatever catches your eye may not be indicative of anything relating to strength/durability. You will certainly feel some variation between the various brands and options, some are stiffer/tighter and others are looser/supple.
One alternative option to chords altogether that Ive been liking lately is the sewn web-o-lette type anchor sling. I have the Metolius web-o-lette style anchor sling, the longer of the two sizes, that I really like. Some of its advantages: integrated pouch that it stuffs into (vs having to coil it). This is really convenient & fast plus it provides protection from UV damage as well as abrasion. Also the fact that it has sewn loops on each end (reinforced/double layered) instead of relying on a knot or knots. This allows for it to meet the 22kN standard for sewn runners and it eliminates the concern over knotted dynema’s tendency to slip/untie when under load.
@@brianrodman1033 thanks for the thorough reply. With the sewn loop products you mention. Does each loop go direct to an anchor point? If I’m picturing that properly, those two points would have only one stand so there isn’t a redundant shelf. Shelf isnt really essential in a usual non-big wall setting but I’m curious if what I’m picturing is how you’ve used it.
I think it wouild have been interesting to see a certain length of each cord tested deconstructed, then the sheath and core components weighed to get an idea of sheath percentage. Perhaps not the most accurate way of doing it, but this along with examining the actual construction and braiding of each cord might have brought more insight about the difference in strengths
Let x denote the area of a circle: x = π r^2. Take logs: log x = log π + 2 log r then differentiate (d log x) / (d log r) = 2. Log differences are approximately percent changes for small percent changes hence an approximate 1% increase in radius (or diameter) leads to a 2% increase in area. An ideal 6mm diameter circle has an area of 28.3 square mm while a 7mm diameter circle has an area of 38.5. 7mm is about 16% larger than 6mm, but a 7mm diameter circle has about a 36% larger area (which is close to the approximation of twice as big a percent change).
From 6 to 7 isn't a small percentage change, so the first order approximation isn't much help.
Isn't it because nylon strands come in relatively thick strings, and maybe going from 6mm to 7mm you can suddenly fit 2 more strings, rather than just one more for 5mm to 6mm because of the geometry of the cross-section?
I like that shirt , where can I buy one?
High tensile strength cords even tho suitable for repelling are a disadvantage when distributing forces. I would not like to use a HTS 6mm and have to try and arrest a fall or even worse a get caught in a bite or up against a solid surface. A lot of force pushing against my meat: last thing I want is to get cut/crushed.
I have rapp’ed on a Petzl RAD Line. Used a Grivel Scream. Works just fine.
I want to get a Scream to have a device that’s intended for rappelling on accessory cord down to 6mm or 7mm in diameter. Good to hear that it works well for you. Are there any other devices that you would recommend checking out in addition to the Scream. Also any downsides to using the Scream to look out for?
@@brianrodman1033 the Scream is a simple binding plate so it is more fiddly to use than a standard tube device. It also has 4 modes that it can be used in creating various degrees of friction on different sized ropes. They are not the easiest to discern.
All this is to say that it’s not the simplest to use. Gotta practice with it before deploying it in anger.
As to other devices to use, I picked up the Petzl RAD system, containing a Tibloc and MicroTraxion.
If you don’t already have an ascender, and don’t use them often, pick up a Tibloc or two.
On a recent trip to the Alps, my guide and our crew used some purple static 7mm line for everything. I felt perfectly comfortable rappelling using that. It felt plenty substantial.
The Petzl Rad line, on the other hand is spooky thin. Were it no for the purposefully high friction sheath and low compressibility of the rope it would be even creepier. I get a feeling that normal accessory cord won’t perform as well as a dedicated rappelling line as the ones designed for the task.
Petzl suggests using beam cross-section type HMS ‘biners when rapp’ing on the RAD line. This probably applies to all other similar ropes. They are higher friction than round stick ‘biners. Adding multiple into your normal rappel device adds friction.
Lastly, if you haven’t/don’t already, learn and practice how to climb a rope that you are suspended from. An ATC Guide/Petzl Reverso/most binding plates like the Grivel Scream can easily be turned into a progress capture device while on an extended rappel. Combined with a second prussik cord, a double length sling, and 2 extra locking ‘biners you have a very versatile system that gets you up and down the rope with zero drama. Also learn the Texas Prussik technique of ascending a rope with two prusssik cords. Always keep that kit with you. Lean how to rappel without a device. The Munter Hitch can save you or your partner when you inevitably drop your Rappel/Belay Device.
Personally I would consider 2 double length slings, 3 locking HMS carabiners {Petzl Attache are favored by me}, 2 prussik cords, a cordalett, and a guide mode belay device should always go out into the field with you as your Emergency Rappel Kit. Add in a Tibloc and MicroTraxion with their accompanying carabiners, and you also have basic ski mountaineering kit, too.
As to other devices designed for use on such thin cords, I know of none.
Same thing with cigars just because it's shorter doesn't mean it won't last as long..... Among other things 😏
I've got big bollards,
I've got big bollards,
They're such big bollards,
And they're dirty big bollards,
And he's got big bollards,
And she's got big bollards,
But we've got the biggest, bollards of them all!
Watch your videos all the time and realize im not subscribed. Why am i not suscribed?
My 7mm is only 9.5 kN
so maybe I shouldn't be making quads out of 6mm lol
Suggestion: full strength tests of dynamic ropes. Beal opera 8.5, edelrid Swift protect 8.9, edelweiss performance 9.2, mammut crag lines 9.5, sterling vr9 9.8 for range recommendations
That sounds like a very expensive test. If you want to send all those ropes to Ryan, I’m pretty sure he would do it.
BREAK ALL THE THINGS.
nerdy niche !!
2:07 nicee 👌👌😎🚬
the difference is great, ask my ex-wife.
John Harlin is generally reputed to have died on the North Face of the Eiger whilst jumaring on a 6mm fixed rope.
6mm is nice and light and compact to carry if your going to fix thousands of feet of it, but like any rope it frays if you leave it out in a storm and then the slender but arguably adequate safety margin that it provided is gone!
It's better than you mothers washing line though!
Let's go!
12.86 kN is not below MBS if it is specified as 13 kN, since 13 kN is only given with two significant figures. 12.86 kN is 13 kN with two significant figures.
Im not a physicist or anyone who understands in depth the structural integrity of ropes, but however i just have some sort of feeling that the tensile strength of the rope may vary depending on the length of rope used. Id recommend testing with larger distances and compare to find out if true.
Well, that's not now things work, dude, with ANY material.
@admacdo2009 ya i was stupid high when i made that comment lol. I forgot about it till now
Whats the norm for those cords? Pretty sure the EN ones of 6mm habe 7.2kN MBS… 🧐
The reason the jump from 6mm to 7mm that you measured was lower than the manufacturer's specs showed was clearly that the 6mm ropes you tested were simply too strong. All but one sample broke over MBS, but the smaller diameters were higher over their MBS than the larger ones.
the strength increased almost is exactly in proportion to the cross sectional area. the larger the cross section of fibers, the stronger it is. it becomes obvious if you plot area vs. strength on a graph. No mystery.
Neither the relative increase of the diameter *nor of the cross-sectional area* should have been compared to the relative increase of the breaking strength for meaningful results. It is the actual mass of the material per unit length (prestretched by some small nominal amount - I think 5 kg equiv is the standard when measuring the nominal diameter) that matters. 🤦♂️ But kudos big-time for using mm squared instead of "sixteenths of erected other roughly cylinder-shaped body" standard units.
probably the nerdiest video you've got😂
you may be making a mistake in assuming the sheath is the same size. you need to check the sheath to see if it increases in thickness.
As a Ski patrol we used 6mm rope to rappel off of a chair lift.
non climbing related comment. that guys voice sounds like Trump!! he could make a killer impression
no
Watch a few more wand wait for him to saw “sewn” or “known” etc and you’ll realize he would be hopelessly unable to to a Trump impression. Lol (he has called this out on a video so I’m not being a jerk.)
Great video, but I wish you would not classify cord by 'diameter'... cord should be classified by lineal weight.. then you can plot strength (kN) VS linear weight (g/m)..
Take it up with the manufacturer's and retailers.
@@HowNOT2 you could weigh a piece before your test
@@francismartinevans think his premise is manufacturers label this in diameter, this is sold and discussed in diameter, and the channel is usually about use in the field and by consumers. Wouldn't make sense for him to not classify cord in diameter.
@@zacharylaschober the manufacturers seem to tell so many 'pork pies' about rope/cord diameter... hence i think weight per metre is a more scientific/geek way to 'classify cord'... im convinced the testers would see a different data / trends when plotting their results... especially when you start weighing your ropes, and find your 8.9mm and 10.5mm weigh so similar
@@francismartinevans not disagreeing there, more explaining why the phrase "I wish you would not classify cord by 'diameter'" is more to do with how manufacturers and the public classify cord, and more of a "have you tried classifying cord by X" might be more appropriate for the channel.