dyneema sling durability?

I was recently talking with another climber who told me that she had read a study regarding the durability of dyneema slings (like the 8mm mammut ones) that stated the slings were only good for about a year before they began to become too weak to safely climb on. Seeing as how my entire set of trad draws consists of mammut slings, this was pretty startling and concerning. I was wondering if anybody else out there has heard anything about dyneema durability, or has any experiences of their own with 8mm dyneema slings either breaking or becoming unsafe?

I haven't heard anything about a time limit on dyneema. I've heard alot of other theories behind why Nylon is better, but I still use/prefer dyneema.

I have a mix of 12mm and mammut skinny slings. I personally won't buy the 8mm ones again because I find that they tangle easily and seem to wear much faster than the 12mm.

Some of the new fangled tech-cord stuff they are coming out with has a large degradation of strength over relatively small numbers of bend cycles(bending of the rope as in clipping and weighting it)

Just my experience,
Evan

"talking with, read a study, I've heard a lot of other theories, I've heard a couple of things"

Quoted from above post.

Please provide something substantial. I routinely fall onto 6 year old dyneema (and I'm still here).

I was wondering that at the Gunks a few weeks ago while climbing with my buddies old and very frayed 8mm slings. old being about 3 years, I think they fray really easy and probably need to be replaced every 3-5 years because of that.

I still trust old nylon runners that were bootied 15 years ago.

"totally static"(????) nothing is totally static. what are you trying to say?

they have little elasticity -- is that a better way to say it?

Comparing nylon webbing to dynemma/spectra runner in respect to elasticity for the system, doesn't really serve a purpose. It's the nylon cord that you can see the benefit of elastic material to help maintain a system; and that would be better served in load distributing anchor systems.

Slinging pro while leading on a dynamic rope you won't see a difference as the rope, belay, & climbers take most of the energy; screamers can help though, if you are given some form of dynamic property also during the fall.

What may be the concern of the op is the repeated knotting that breaks down the fibers. I generally replace the double length slings I use for anchor rigs after about 3 years of moderate use; you can notice the physical condition. Anything that takes a big hit would be replaced immediately, these things don't recover their rating.

that's much better.

I wouldn't trust skinny dyneema runners over 300 days of use.

I have my reasons, I work with Dyneema pretty much every day here at work, and my reasons are very good. You can ask folks who know me if they think i've got any idea what i'm talking about.

If I expose a dyneema runner to temps over about 150 degrees, i throw it out. I don't leave them in the car in the desert in the summer. I don't have them near my rap system.

YMMV.

Okay - so here's a question...

Before BD went skinny with their dyneema, they had a 12mm? Dyneema runner (white stripes) - Are these more durable than the 8-10mm Dyneema slings or should I be concerned with all my Dyneema after about 300 days of use?

crackers wrote:I wouldn't trust skinny dyneema runners over 300 days of use. I have my reasons, I work with Dyneema pretty much every day here at work, and my reasons are very good. You can ask folks who know me if they think i've got any idea what i'm talking about. If I expose a dyneema runner to temps over about 150 degrees, i throw it out. I don't leave them in the car in the desert in the summer. I don't have them near my rap system. YMMV.

What are your reasons? I don't know you or people who know you as far as I know. So, please elaborate.

caughtinside wrote: An engineer on RC.com pull tested some that were 1 year old, 2 years old and 3 years old. Each year showed a decrease in strength, with the 3 year old slings breaking around 14 or 15kn if I recall. Still 'strong enough' but the degradation plus the high price was enough to steer me towards equipment that lasts a bit longer.

About the same time as that rc post, I had an old - but lightly used - Mammut sling pull tested. I don't have the numbers in front of me, but the clear (to me) conclusion was that it's not age as much as it is the amount of use. So I'd agree with the 300 day suggestion.

Jordan, what were the circumstances of this failure? How old was this runner? In the pic it looks like a clean break, almost like someone cut it (?).

My entire rack of runners are 8mm Dyneema, are pretty fuzzy in places, and will continue to see use for a long time. These things don't just break. That's why Jordan's picture is so flustering to me. I know someone who put a whole nest of both nylon and dyneema slings on the roof of the CU engineering building, in the sun, for more than a year. They were drop tested off a tower and still held up fine. Maybe this is unwise and unsafe, but I'm not running to the mt. shop to buy new ones based on circumstantial evidence listed above.

I have used Dyneema and Spectra cords sailing for a while and have had very few failures under load despite thousands of hours of use. I use 7/64" (less than 1/8" diameter) for trapeze lines on my 49er (sailboat type) taking full body weight and impact load and I have not had a failure. Dyneema is a very stable molecule resistant to chemicals and UV (sunlight), but it's strength is temperature sensitive. There are 4 readily available variations: SK60, SK65, SK75 and SK78. All Dyneema has a tendency to creep elongation (meaning permanent) under load, but SK75 and 78 have less. All have very low elasticity, with about 1% elastic (meaning recoverable, like a rubber band) elongation at 30%of breaking strength. Woven Dyneema sets under load, so after the first loading it has less elongation as the fibers lock into place. Dyneema's strength is reduced in tight bends, like over edges and in knots, so I always splice it instead of knot it when I can. A splice has 95% of the strength of the original cord or tape, while a knot has 40-60% (depending on the knot). Sewn slings similarly maintain a high percentage of the material strength. The failures I have had have been very frayed pieces of knotted 1/4" Dyneema with lots of use. I wouldnt girth hitch or tie off Dyneema slings, like in the picture in the previous post.

All that said, I dont know what the useful life of climbing slings is and retire mine frequently.

I forgot to add the links:
Technical specs at dsm.com and samsonropes.com
The graph came from the Samson ropes website. There are several good reports by NASA on the relative strength, creep and life differences between Dyneema and Vectran for use as satellite tethers, but I dont have the links to those reports.

Crag Dweller wrote: What are your reasons? I don't know you or people who know you as far as I know. So, please elaborate.

Crackers can correct me if I'm wrong, but I believe he's the person behind Cilogear, which has a reputation for well-made backpacks. Based on this, I'd tend to take his assessment of things like dyneema seriously.

JL

Greg Twombly wrote: I have used Dyneema and Spectra cords sailing for a while and have had very few failures under load despite thousands of hours of use.... Dyneema is a very stable molecule resistant to chemicals and UV (sunlight), but its strength is temperature sensitive... All that said, I dont know what the useful life of climbing slings is and retire mine frequently.

I manufacture things out of Dyneema. I've been doing it for over four years. I've done thousands of destructive tests on the material and other interesting fibers. I'm terribly sorry Crag Dweller that I don't have the time to elucidate my reasons in greater detail at this time. I will revisit this in February when things have calmed down here at work.

Mike, peace, hope the trees are still scared of your tools. ;)

Andy, the picture is of course from the Verm. If you google Mammut Accident report test sherman or something like that, you'll find mammut's entire testing report. It's an interesting read. IMHO, if your 8mm Dyneema are really fuzzy, I'd make you climb with my slings. Of course, YMMV.

While Greg's info from Samson is true (SK85 is probably the most common fiber right now in textiles, but anyway...), Samson's information and Greg's anecdotal data is kinda worthless to us as climbers because of heat and entirely different construction between climbing gear, spaceship stuff (and yes, i do know what i'm talking about) and boat lines. Full body weight ain't crap in the world of impact forces as I'm sure all of us know from bounce testing a head or a thin nut. Dyneema is probably my favorite fiber. I love the stuff. Don't get me wrong, but...

Dyneema isn't dimensionally stable at about 180 degrees Fahrenheit. Like in your trunk in the desert. Or near your belay device after a long rap. And then weird stuff happens. YMMV.

I've got to get back to work. I apologize for not having the time or the liberty to post more information. 90% of my slings are Dyneema, I just replace them every other year. As they say, $200 of slings prevents unhappy thoughts when I'm gripped above my last piece and whinging for mommy.

saxfiend wrote: Crackers can correct me if I'm wrong, but I believe he's the person behind Cilogear, which has a reputation for well-made backpacks. Based on this, I'd tend to take his assessment of things like dyneema seriously. JL

My name is Graham. I do indeed own and operate CiloGear.

We do manufacture backpacks (and make some other stuff) out of 100% woven Dyneema, 90% woven Dyneema, non-woven dyneema, (even 90% cordura and 10% dyneema ripstops, but in this context does that matter?) and play with Dyneema knits, felts and other stuff.

Like I said above, I love my Dyneema slings. I just replace them on a regular basis.

See my dyneema sling testing. This sling was a couple of years old and I had caused some friction issues by doing something stupuid where a weighted rope drug across it.

The sling was still in great shape.

??

The fact that people say this stuff is static is technically not true. This sling stretched over 2 inches before it broke. Nothing is static. Agreed, compared with a dynamic line this is very stiff. I once broke a nylon sling and that sucker stretched almost double its original length before it broke. For fun we unloaded it then broke it. It stretched back like a rubber band.

I have been climbing on my dyneema slings (the same ones) for five years and I am not dead yet.

Andy Novak wrote:Jordan, what were the circumstances of this failure? How old was this runner? In the pic it looks like a clean break, almost like someone cut it (?)

The picture isn't mine. It's posted up all the time when people start talking about dyneema failure. Anyway, long story short, this one was partially cut (or chewed), was weighted, and failed.

edit: Oh, someone else already posted the link. look there for more info.

I guess my point wasn't clearly made. It was not that the loads in sailing are the same as climbing, but that in sailing we expose our Dyneema cords to the harshest environment; continuous sun, abrasion, and loading, and Dyneema has a long service life under these conditions. We dont put them away in bags until used; they stay on the boat in the sun, wind, freeze, etc.

To simplify my points:
1.) As crackers says, the strength is very temperature dependent
2.) strength is significantly reduced by stress concentrations (knots, edges, stuff like that).
3.) Dyneema is UV and chemical resistant, and has good abrasion life
4.) replace often

On other points, SK85 has not found widespread use in cordage. Yale, Samson, and Marlow all use SK60 thru 78. The website I referred to dsm.com is the discoverer, developer and manufacturer of Dyneema fibers. Websites of the major cordage makers (www.samsonropes.com, yalecordage.com, marlowropes.com) all have good technical information on Dyneema. One manufacturer, Hampidjan uses the thermal characteristics of Dyneema 75 to advantage by heating the fibers under load to make a higher strength product, DynexDux.

As a general matter, stretch is generally a good thing since it dissipates energy. There are probably other fibers that would be a better fit for climbing than Dyneema (eg.aramid fibers like Technora used by New England Ropes), but like crackers I'm a fan of Dyneema.