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Ed Bannister
Mountain climber
Riverside, CA
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Topic Author's Original Post - Apr 22, 2008 - 06:28pm PT
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I read some miss information on supertopo today,
she was sitting right next to Kevlar, so I thought this might help. The bad info was that Dyneema weakens with bending and the writer prefers Spectra.
Interesting, Dyneema and Spectra are identical in chemistry, and only minutely different in construct quality consistency.
Both are ultra high molecular weight polyethelene arranged as generally paralel fibers, thus the qualities of super slick gliding surface, and no knot retention. Both fibers will not accept dye and are white, they must be woven with another yarn in order to retain a knot, or accept color in the cord or web.
The difference, between Dyneema and Spectra is this, Spectra fibers are observed to be less consistent as shipped by the factory.
The two factories:
Spectra is made by Honeywell, in Colonial Heights, VA
Dyneema is made by DSM in Heerlen, Netherlands.
Hence, the best small diameter cord weaver in the world reccomended to me to use dyneema rather than spectra in the last 60,000 yards I have purchased for use in the MATourniquet.
have a look at matourniquet.com
One device was used in army training for 10,000 cycles, which, coursing through the pulley sytem and resetting, 120,000 bends of the cord were exerted on a .9mm cord, half under load, and it still bore the working load without failing.
In other words, the fiber does not weaken when bent, in theory, and test data from the factory, and not in practice. Spectra or Dyneema.
It may be that the writer was recalling that Kevlar does get weaker as a cord of this material is bent, Kevlar's surface is very rough and fibers under load sand each other to dust as the pass by each other when bending over an edge. Edelrid made 5.5 mm kevlar cord with a nylon sheath and passed it over an edge, weighted one end with 11 lbs. (5 kg) and after 700 or so cycles checked the cord to find the nylon sheath intact, and powder inside.
hope that helps,
Ed
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healyje
Trad climber
Portland, Oregon
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Apr 22, 2008 - 07:02pm PT
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Great and informative info - thanks.
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bluering
Trad climber
Santa Clara, Ca.
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Apr 22, 2008 - 07:13pm PT
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That is good to know, thanks for posting it.
That's a badass looking tourniquet too! One-handed!!!
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MZiebell
Social climber
Prescott, AZ
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Apr 22, 2008 - 07:57pm PT
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Thanks - very useful info.
Martin
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Mungeclimber
Trad climber
sorry, just posting out loud.
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Apr 22, 2008 - 08:27pm PT
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So what can we extrapolate when we combine this with the Verm thread? Tight bends with dyneema apparently failed.
I'm back to using BD nylon. You can cut em and retie them without issue if you need a rap station in a pinch on bolts with tiny holes.
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maldaly
Trad climber
Boulder, CO
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Apr 22, 2008 - 09:56pm PT
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mungeclimber, Verm's sling was cut with something sharp. Look up the report that Mammut put out. It's very informative and it supports my findings. He brought the failed sling over along with 4-5 others from the same batch. Observation inder 40X magnification looked like they were cut. All even, no mushrooming and no elongation that would be seen in a tensile or compression failure.
We tested the others of the same age that were bought at the same time. When rigged identically (girth-hitched to a 12mm dyneema sling) we saw any sling failure at all.
What's the lesson? Don't let anyone cut your slings...
Climb safe,
Mal
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Mungeclimber
Trad climber
sorry, just posting out loud.
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Apr 22, 2008 - 10:35pm PT
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thx mal, much appreciated. good to hear, I'll check the site and maybe even go back to those. so conveniently sized.
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Ed Bannister
Mountain climber
Riverside, CA
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Topic Author's Reply - Apr 22, 2008 - 11:23pm PT
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ok, it was not "possible" bad info, it was bad info.
The good thing here is that is was not a life and death dangerous error.
This forum as well as being a great meeting place, has a real wealth of knowledgeable people.
but, when you don't know...better to ask, than to pass out bad info.
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Moof
Big Wall climber
A cube at my soul sucking job in Oregon
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Apr 23, 2008 - 01:05am PT
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Please also reconcile multiple sets of measurements showing steady strength degradation of mammut (and other similar) slings over a 2-3 year period. I believe a bunch of Healyje's slings were tested showing a ~40% reduction after 3 years.
Tom Moyer's high strength cord testing paper (http://www.xmission.com/~tmoyer/testing/High_Strength_Cord.pdf) showed sizeable strength reduction in a relatively small number of bend cycles.
Lastly, multiple folks doing 2:1 hauling with the Chongo ratchet using no more than body weight have had their 5mm spectra or dyneema cord fail catastrophically after many many cycles.
Most climbing related useages have pointed to self abrasion, or similar fatigue (if not actual self abrasion) that in climbing applications makes it advisable to replace our spectra or dyneema goods much more often than equivalent nylon/perlon ones.
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Ed Bannister
Mountain climber
Riverside, CA
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Topic Author's Reply - Apr 23, 2008 - 12:51pm PT
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Great Point Moof!
Dyneema fiber by itself when flexed does not weaken.
Individual brands as sold vary wildly in loss of strength depending on the fibers chosen and the nature of the woven blend.
This is because of the nature of the blend of fibers, most are nylon and spectra, and some even use kevlar, guaranteed loss there!
None of the tests cited were dyneema by itself,
because the stuff cannot be used by itself in climbing applications.
me? i use nylon...
but "the fet" stated that spectra was more durable than dyneema, clearly incorrect.
I think there is only one guy on the planet who can really completely answer this, Bernt Prause, he used to be at Edelrid, and I think he works for Mammut now. i will try to track him down and ask.
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WBraun
climber
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Apr 23, 2008 - 01:18pm PT
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OK here's my question.
I see just about everyone now uses this skinny Dyneema sh'it.
I have some too, but only because I've found some on climbs.
Anyways ..... is this stuff strong enough and robust enough for what we do in climbing?
I'm not asking for charts, data and clipboard nerd sh'it, I want the real world scoop from the street. :-)
What's the word on the street on how this stuff holds up and survives daily uses and wear?
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TradIsGood
Chalkless climber
the Gunks end of the country
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Apr 23, 2008 - 01:39pm PT
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Werner, any of it broken? That would tell a better story.
Your word on the street is all going to be that it works. If it did not they won't be reporting it here, for the most part. (Survivorship bias)
I am replacing my WC spectra runners after about 6 years of use. (100-150 days?) They are getting fuzzy. They don't cost that much for a handful.
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rgold
Trad climber
Poughkeepsie, NY
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Apr 23, 2008 - 02:21pm PT
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Alpspitz wrote, "Dyneema fiber by itself when flexed does not weaken...individual brands as sold vary wildly in loss of strength depending on the fibers chosen and the nature of the woven blend. This is because of the nature of the blend of fibers, most are nylon and spectra..."
Moyers wrote, "Spectra/Nylon is also known as Dyneema."
So, two questions:
1. Is there such a thing as "pure dyneema" or not?
2. If there is such a thing as pure dyneema, and nobody uses it for cords and slings, than isn't Moyers the data indicating the blended materials weaken after multiple bending cycles relevant and not "bad information" at all?
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crackers
climber
istanbul/new york city
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Apr 23, 2008 - 02:42pm PT
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I work with Dyneema on a daily basis. There is some incorrect information in the original post. I do not work with cordage, I work with Dyneema fabric and Dyneema ripstops and thread.
Dyneema and Spectra are chemically identical but manufactured in different industrial processes. Honeywell produces Spectra in Virginia and Arizona. DSM produces Dyneema in North Carolina, the Netherlands as mentioned above, and in a JV operation in Japan with Toyoba. There are several factories in China making off brand UHMWPE that chemically resembles Dyneema, most of which goes into fishing line.
There are 100% Dyneema ropes, but AFAIK, they are exclusively used as mooring lines and in the shipping business.
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