The difference is INSANE

00:00 Accessory cord size differences
02:38 How we are testing it
03:30 5mm
05:28 6mm
05:56 7mm
07:20 8mm
08:19 All the data

[markkNL]

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.

[two_feet_in]

Not sure if it’s common for all ropes. But for Beal, the colored strand is a marker for the manufactured year.

[rianfelis]

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.

[zacharylaschober]

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?

[tomsmith]

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.

[simonrobbins]

This is such a professional setup. Great consistent results and impressively reproducible.

[prgnify]

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.

[hidden_sense]

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.

[spogulitR]

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!

[JippaJ]

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.

[antrumkfpsalatschleuder]

Yeah rappelling on a Petzl Rad line is scary especially if you rappel into a crevasse.

[WyomingMtnMan]

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.

[ErstwhileStrong]

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.

[quickstream]

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.

[StephaneDubois-ietb]

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

[tobiasbrewin]

You should weigh the amount of core vs sheath for the different diameters to see how the ratios vary across the different diameters.

[danielwendell]

Hell yeah, love seeing you break stuff for data.

[andreasantoro]

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.

[Spder]

I just found out that apparently I am a niche nerd because this examination was very interesting and the results enlightening. Great stuff Gents. 👍

[andybyrne]

Thank you for the videos. Super useful to know especially for people new to climbing and building anchors !