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EdBannister
Mountain climber
CA
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Aug 18, 2010 - 06:41pm PT
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Dyneema is manufactured by DSM in the Netherlands.
Spectra in manufactured by Monsanto in the US, but with more at least reputed irregularity than Dyneema, so if you are a discriminating manufacturer, you use Dyneema.
but, you can make a crude version at home.
Get the poly bag from the grocery run, or from some of the dry cleaners.
Pull on the sheet in one direction, as the stuff gets stretched, it gets stronger. The long poly molecules become increasingly paralell as they align in one direction, elasticity decreases and strength increases. As all fibers become paralell, there is no stretch, just loading, or failure.
hence:
Dyneema & Spectra are like using a swaged cable in their inherent properties! not true, the braided steel stretches, dyneema or spectra, do not.
Please, forgive the tongue in cheek, i try not to joke about anything safety related, obviously it is correct to think that cable does not stretch, but an engineer would tell you that cable does stretch a bit, and that Dyneema does not.
In an application where stretch should be managed or minimized, dyneema is wonderful, i used it in a touniquet i designed a few years ago...
but my slings? the rope is dynamic, but i still use nylon slings.
edit, unlikely, but why not have the sling stretch rather than your spine compress... ?
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Ain't no flatlander
climber
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Aug 18, 2010 - 06:51pm PT
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Dyneema is manufactured by DSM in the Netherlands.
Spectra in manufactured by Monsanto in the US, but with more at least reputed irregularity than Dyneema, so if you are a discriminating manufacturer, you use Dyneema.
Or if you're BD, you call it your own special sauce named Dynex so nobody knows what they're buying.
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Jaybro
Social climber
Wolf City, Wyoming
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Aug 18, 2010 - 07:02pm PT
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Do they still make Dyneema™? Why? Failed technology, move alone, there are better ways to save
weight.
cause my guts to shoot out my anus
absolutely classic!
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EdBannister
Mountain climber
CA
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Aug 18, 2010 - 07:05pm PT
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Now THAT is Funny!!! perfect call on BD.
Coonyard, as near as i can tell never designed anything, well,
since Tom Frost left,
but they sure have been good at copying and marketing.
Bill Forrest introduced pile to the climbing world because of it's functional perfect fit, his stuff pilled though and look like crap after a while, but it sure did work...
three years later Malden was weaving a softer, cushier version of "pile."
and whala "Synchilla" was born! amazing.
Allen A was selling the socks and ahem the underwear they private labeled for patagucci, at half the price... when i was at Liberty, i wanted to put the socks in the catalog as "Shoe-E-Nerd" socks but the owner just would not go for it.
and don't bring up camalots, they outsourced the design.
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Moof
Big Wall climber
A cube at my soul sucking job in Oregon
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Aug 18, 2010 - 07:13pm PT
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While scary, it is an extreme test to drop 80 kg into a sling with zero give in the system. In the real world a climber who, for example, climbed up at a rap station to frig with something and slipped would be much squishier than the 80 kg weight. We have give in our harness, give in our spare tire waists, as well as our spine/legs/neck etc. I would really doubt the sling itself would break at forces below where it would snap your spine, rupture your aorta, etc.
So I would guess breaking a sling is unlikely using spectra/dyneema/nylon, but serious injury and possible intestinal inversion from a daisy/sling factor 2 fall is likely. Avoid it.
Yurr Gunna Dye!
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Thorgon
Big Wall climber
Sedro Woolley, WA
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Aug 18, 2010 - 07:19pm PT
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Thanks, Ed.. O.K. Dyneema, doesn't have the same stretch that nylon does, that was the point I was trying to make!
I agree No Joking Matter, it's life and death.
Thor
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sethsquatch76
Trad climber
Joshua tree ca
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Aug 18, 2010 - 07:35pm PT
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Coz,
DO NOT girth hitch with either specta or Dyneema runners!!!!!!!!!!!!!!! Dont have the numbers in front of me byt they are BAD!!!!!!!!!!!!! Stick to good old nylon!!!!!!!!!!!!!!!!
Your friend, who wants to see ya around for awhile Seth
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mucci
Trad climber
The pitch of Bagalaar above you
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Aug 19, 2010 - 12:26am PT
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They are meant to be used AFTER your first piece off the belay.
Only "Biner to Biner" Not made for girthing chicken heads, threading etc.
Never in a belay!
I don't understand why you see people with triple lenght dyneema slings for thier anchoring rig?
I thought this was common knowledge? For YEARS!
The companies that produce these items made very clear the above dangers, and what threats they imposed on a system.
It's all about reading labels these days.
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labrat
Trad climber
Nevada City, CA
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Aug 19, 2010 - 12:43am PT
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BD bashing again Coz? Why single out the company you worked for again and not the the others that produce this type of sling? I wonder if you knew the answer to your question before you posted it in the OP? Mammut, Petzl, Blue Water and Climb High all produce similar products. Any concerns about the Metolius PAS? The instructions for the PAS recommend girth hitching it to your harness.
Erik
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Jaybro
Social climber
Wolf City, Wyoming
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Aug 19, 2010 - 01:06am PT
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The thing I don't like about dyneema/spectra, is that they wear out in no time, Weakrening appreciably by the minute. again,
why own it?
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jfs
Trad climber
Upper Leftish
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Aug 19, 2010 - 01:43am PT
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Are you guys serious?
I'm being honest here...
Most everyone that posts here has been climbing for years. I know coz has at least. Was this a serious question? In all honesty it's way too troll-like.
Who in the hell actually thought that taking a factor 2 fall directly onto a Dyneema sling was OK??? Hell...who thought taking a FF2 direct fall onto a freakin' good ol' nylon sling was all peaches and roses?!?! Of COURSE the Dyneema will break...and of COURSE it will transmit MASSIVE amounts of force onto the climber. The force levels with nylon are huge too.
You mean to tell me all you dudes who've been climbing for DECADES........were unaware of the risk!?!?!
What the.........????? I'm shaking my head...
And to the folks freaking out and cutting up your slings...fine, whatever. Do what you gotta do to feel safe. But you are FLIPPING out over something that's been known and accepted and worked with for years. Yes there are risks...there are risks associated with every damn piece of gear we use as climbers......if we are idiots...
jeez... rc.noob around here.
And I'll second the weird coz and BD dynamic. Coz...if you got a bone to pick with BD...fine. But you're downright comical when you pull something like this. Like BD is the only dyneema sling maker out there... Please...
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jfs
Trad climber
Upper Leftish
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Aug 19, 2010 - 01:51am PT
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Mike - from the DMM website...
It is also important to bear in mind that the characteristics of slings and quickdraws are also affected by the weave and blending of fibres, purposefully used to achieve particular handling qualities. Dyneema® slings are in fact usually a blend of nylon and Dyneema® fibres. http://www.dmmclimbing.com/news.asp?nid=293&ngroup=1
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labrat
Trad climber
Nevada City, CA
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Aug 19, 2010 - 01:53am PT
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jfs,
Check out prior posts by coz about BD harness loops. He has a bone to pick.
Erik
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jfs
Trad climber
Upper Leftish
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Aug 19, 2010 - 01:55am PT
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That's kinda why I commented. I don't get it.
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healyje
Trad climber
Portland, Oregon
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Aug 19, 2010 - 01:57am PT
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Just be aware that skinny [Mammut] 8mm dyneema slings have a finite lifespan nowhere near as long as nylon. Moderate trad use will drop the breaking strength of them from 22kn to 10-12kn at a rate of about 3-4kn per year. They were never designed to last essentially forever (like a nylon sling), but rather were specifically designed as a lightweight consumable item for those looking to go ultralite. These findings were a result of consecutive year testing over three years and I only used the slings about 2/3's of a year of climbing each year up here due to our rain.
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Clint Cummins
Trad climber
SF Bay area, CA
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Aug 19, 2010 - 02:57am PT
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If you need a tether that can handle a short fall and not break itself or you:
Yates Adjustable Daisy with built-in Screamer:
http://www.yatesgear.com/climbing/etriers/index.htm
As for me, I don't use daisies or dental-floss width slings (but they are OK for leading if on my partner's rack; I just don't want to keep track of how old they are if they were mine).
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Ain't no flatlander
climber
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Aug 19, 2010 - 11:44am PT
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So much nonsense in this thread. HMPE slings have been on the market for about 20 years.Can anyone point to a single failure in the real world? Verm's is the only one I recall hearing about and there were other factors involved. For that matter, the fears about using daisy chains to anchor are pretty absurd too (assuming you're smart enough not to cross-clip). A lot more serious stuff to worry about in climbing.
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Largo
Sport climber
The Big Wide Open Face
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Aug 19, 2010 - 12:38pm PT
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Short course in UHMWPEs.
Dyneema and Spectra are different brand names for the same very strong fiber know in chemical argot as Ultra-High Molecular Weight Polyethylene - UHMWPE.
Both Dyneema and Spectra are gel spun through a spinneret to form oriented-strand synthetic fibers of UHMWPE. Gel spinning, also known as dry-wet spinning, is used to obtain high strength or other special properties in the fibers. The polymer (source material) is in a "gel" state, only partially liquid, which keeps the polymer chains somewhat bound together.
While the common usage of "polymer" suggests plastic, the term actually refers to a a variety of natural and synthetic materials.
In rock climbing, UHMWPE sling material is known as "tech-webbing."
The rule of thumb for "tech webbing" (Dyneema, Spectra, etc.) is to only use it as weight bearing, static links in the belay system. Any link in the belay system where one is moving around (such as with a daisy chain), use nylon, not tech webbing. The tech sling will likely not break in the event of a short fall directly onto the anchor, but as Rock and Ice testing showed some years ago, such shock loading can bust biners and rip anchors with frightening ease because these materials do not stretch much at all.
JL
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dags
climber
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Aug 19, 2010 - 12:47pm PT
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Can someone explain why Dyneema isn't suitable for girthing chicken heads, threading, etc.?
If you're clipping in to Dyneema threads or hitched chicken heads and climbing on a dynamic rope, doesn't the rope provide the necessary dynamic "give" in the event of a fall? How is threading and hitching with Dyneema substantially different from clipping a piece of Dyneema to a cam or stopper?
I can understand if the threading or hitching causes the sling to run across a sharp edge, but that doesn't seem like a particularly safe thing to do with Nylon either...
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HighTraverse
Trad climber
Bay Area
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Aug 19, 2010 - 02:20pm PT
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Mike.
I've heard many state Dyneema doesn't stretch. A shoulder-length Dyneema sling I have that took a fall is now about 1.5" longer than my others. Not propping or panning any particular gear, but clearly [a] Dyneema [sling] does stretch if you take a twenty+ footer on it.
This is a very interesting observation. The sling has taken a significant fall. However you say this sling is now 1.5" longer than the others. This leads to a few questions: Are all the others the same length? (I'll assume yes) Have they taken serious falls? (I'll assume no).
Then the fall sling has been stretched beyond its elastic limit. Retire it immediately, preferably cut into pieces.
Elastic limit is (simply) defined as the amount of force pulling on a material (a spring, a rubber band or your sling) that when the pulling force is released, the material returns to its original length.
Safe working stress for "classic" engineering materials is always much less than the elastic limit.
The energy used to stretch the sling or rope or carabiner is dissipated by the stretching and therefore isn't absorbed by the rest of the system. So in a fall, a stretching rope/sling/'biner reduces the mount of energy absorbed by the rest of the system (including your hopefully non-inverting guts).
By the way, it's not true that "Dyneema doesn't stretch". It certainly does, just a lot less than nylon for the same force IF IT'S THE SAME cross sectional area. Therefore Dyneema slings can be much thinner than nylon to hold the same load. If nylon or hardened steel are loaded below its elastic limit and then released it will also appear to not have stretched.
The entire system is complicated by the fact that nylon and Dyneema are vastly different materials and neither is a "classic" engineering material (like steel for instance).
So the only real data you can go on is dynamic test data.
Read the manufacturer's usage limitations and heed them. If any kind of load bearing material has permanently stretched get rid of it immediately.
I would not use Dyneema without being sure other parts of the system will be absorbing the fall energy.
dags
your reasoning is sound.
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