Skinny dyneema slings - 2 years later...

[JosephH]

Olyclimber - I shipped the results off to MammutUSA and I'll let you know if I hear anything back...

[kdawg]

My main take away from this is that it probably is a bad idea to belay with a grigri/cinch or any other relatively static device when climbing trad on these rascals...

[kdawg]

oops... I was trying to quote that last bit... just wondering; I thought that it was generally a bad idea to belay trad with any sort of static device???

[G-spotter]

WE'RE ALL GONNA DIE!

[billcoe]

G-spotter, you working overtime today? It's 5:30, go home.

[G-spotter]

Bill, I didn't start work until 1 today! But I already started

[MattStan]

Joseph, do you happen to remember if there was any apparent wear difference between the short sling and the longer one?

 

As far as pull testing goes, it's my understanding from those who know that pull testing (a slow, progressive loading until the piece or sling breaks) is harsher than a true dynamic fall-tower test, as it starts with any elasticity removed from the system and stresses the piece for a comparitively much longer period of time vs. the sudden impact of a fall test.

 

Mammut had prototypes of 6mm dyneema slings last summer, so I expect they'll be hitting the market soon. Similar construction to the 8mm, but the tube is rounded rather than flat, resulting in a cord-like feel. Whether 8mm or 6mm, it's precious little material, so an aggressive turnover schedule is probably warranted.

[JosephH]

MattStan - All twenty of them appear uniformily worn with no specific points of wear that I can discern. They are also uniformly quite "hairy" or abraided compared to when they are new. I don't know the specifics of the testing but these folks do know all about every aspect of testing climbing gear. My friend commented on first seeing these on coming to the market that they looked great but that he'd probably retire them on an annual basis - pretty smart guy for just glancing at them as that is probably what the deal is - they are essentially a consumable commodity. As get used they abraid and the fibers break; it's a cummulative deal and so these numbers shouldn't be all the big a surprise I suppose. They become a bit pricy as an annual consumable but I really do love the damn things though I am going to take a look at the 12mm version...

 

Kdawg - I only use my grigri for roped soloing as far as trad climbing goes - otherwise stick to an ATC (Reverso).

 

mtnfreak - will give you a shout when I set it up, thanks...

[still_climbin]

The new Mammut 6 mm slings my have as much material in them as the 8's since they're round instead of flat. We'll have to judge that after we see the weight. Being round instead of flat, they'll have less exposed surface area which could help lessen both wear and sun damage.

 

I really like using aramid cord such as that sold by BD. At 5.5 mm they rate it the same as their dyneema cord (although dyneema is typically stronger per gram). Aramid has much better UV and heat resistance. I'm not sure about wear but so far the cords I use for nut slings, etc. are lasting well.

[TrogdortheBurninator]

I'd also be interested to hear what the radius of the mandrel they were tested over is. Load rate is also always a big issue with polymers, so that could also be somewhat of an issue. At a faster load rate one would typically expect a higher peak load with less elongation. As the load rate is reduced, the peak load will reduce as well. It is probably important to know the standards by which mammut tests their slings before trying to make a quantitative analysis of strength loss (or just test a few new slings using your same apparatus as was previously suggested).

[JosephH]

TrogdortheBurninator - Don't have an answer for the details and that's more than I will probably impose, all I can say is these folks test climbing gear all the time and are completely set up appropriately to do it against various standards. They were kind enough to test them due to our mutual curiosity. I'll try to set up another round of testing with a larger sample and I suspect they'd still be curious enough to do it but that's about as far as I'd be willing to press my relationship...

[sony]

If you want to know if this info has any impact

for you when you climb, you can check Beal's nicely

published tests on the impact force measured on falls:

 

Beal Impact Force

 

The answer is:

 

They generated over 14kN with a GriGri,

but only up to 11.5kN with a tube device like ATCs.

Also the results are counter intuitive and by no means

max values.

 

Also makes you wonder about our 12kN cams, and about

our 9kN ropes: Impact forces of ropes are very important

on the outcome.

 

Cheers!

[JosephH]

Break in girth hitchhed 8mm Mammut Dyneema sling...

[Choada_Boy]

Strands that broke under load would appear "necked down" vs melted under magnification.

[catbirdseat]

The new Mammut 6 mm slings my have as much material in them as the 8's since they're round instead of flat. We'll have to judge that after we see the weight. Being round instead of flat, they'll have less exposed surface area which could help lessen both wear and sun damage.

A round profile would tend to make the sling weaker when used around an object with a small radius compared to a flat profile. I would never use such a sling with anything but a carabiner. No girth hitches.

 

I really like using aramid cord such as that sold by BD. At 5.5 mm they rate it the same as their dyneema cord (although dyneema is typically stronger per gram). Aramid has much better UV and heat resistance. I'm not sure about wear but so far the cords I use for nut slings, etc. are lasting well.

Heat resistance, yes. UV resistance, no. My experience with Kevlar sails is that light breaks them down pretty quickly, about twice as fast as polyester.

[catbirdseat]

If you want to know if this info has any impact

for you when you climb, you can check Beal's nicely

published tests on the impact force measured on falls:

 

Beal Impact Force

 

The answer is:

 

They generated over 14kN with a GriGri,

but only up to 11.5kN with a tube device like ATCs.

Also the results are counter intuitive and by no means

max values.

 

Also makes you wonder about our 12kN cams, and about

our 9kN ropes: Impact forces of ropes are very important

on the outcome.

 

Cheers!

I would argue that these results are by no means counter intuitive.

 

Low-impact force of rope reduces loading on last point of protection.

 

Static Belay device increases loading on last point.

 

Friction along the chain of protection increases loading on the last point. This is the take home message from the Beal site.

 

Friction from changes of rope angle at carbiners and from rubbing on rock increases the "effective fall factor". Quote are mine. If you restrict movement of the rope, it cannot stretch to absorb the impact. The last segment of the rope has to absorb most of the impact. The best way to think of it is that the true fall factor (or effective FF) is higher than the calculated fall factor.

[chris]

Joseph, Black Diamond is always interested in testing out hypothesis like this, and they have the lab equipment to do so. If you're interested I'll send them an email.

[JosephH]

Got the results of the testing of a sampling of my retired three year old Mammut 8mm Dyneema slings. These numbers are down from the two year old test average of about 14kn. These are normally rated 22kn new:

 

# 1) 8 mm Mammut girth hitched to 3/4" Nylon = 11.55 kN.

 

# 2) 3/4" Nylon girth hitched to 8 mm Mammut = 11.76 kN.

 

# 3) 8 mm Mammut girt hitched to 13 mm Dyneema = 8.32 kN.

 

# 4) 8 mm Mammut girth hitched to biner = 12.28 kN.

 

# 5) Ultimate tensile strength = 11.24 kN.

 

# 6) Ultimate tensile strength = 11.9 kN.

 

[TrogdortheBurninator]

Thanks JH!

[G-spotter]

girth hitches reduce strength by ~33% or more suggesting the strngth for a sling just clipped to biners as a normal runner would be 16-17kN...

[chucK]

What do the "ultimate tensile strength" results mean?

 

Were those slings without girth hitches?

[Weekend_Climberz]

Another good test might be having the shoulder length runner tripled up like I and many others I climb with. It'd be interesting to see if that fails at a higher or lower point compared to a fully extended runner.

[JosephH]

Ultimate tensile strength was just a straight test of the sling itself.

[colt45]

Thanks, those numbers are very reassuring: they seem to match the data from Black Diamond's girth hitch tests which were performed with brand new 8mm runners:

 

link

 

For example, in Black Diamond's tests, for 8mm spectra + 3/4" nylon, the 8mm spectra broke at 11kN (8 samples total): similar to your value of 11.5 kN.

 

It seems like the most relevant test would be to have several new runners, and several that are 1 year old, 2 years old, etc (all having similar amounts of use within each batch), and pull-testing them all on the same machine, with the same protocol, on the same day.

[colt45]

Ultimate tensile strength was just a straight test of the sling itself.

 

Thus the results imply that girth hitching a sling to a biner INCREASES the strength of the sling?? Or else the testing/sling strength variability is fairly large, and girth hitching has no effect on strength? It seems like some statistics would be needed to figure out what is going on here.