Discussion Topic |
|
This thread has been locked |
tomtom
Social climber
Seattle, Wa
|
|
|
Oct 30, 2006 - 07:06pm PT
|
From the look of the photo and where the failure occured I'd suspect that ANY knot in that thin a Dynemea sling could produce a similar failure. I fully expected to see the failure in the sling that was girth hitched to, not in the one that had the girth hitch tied in it. I'll bet an overhand, figure 8 or anything else could do the same thing. Aybody done any testing?
Keep in mind that that stuff is just UHMW Polyethylene and has about the same melting point as a plastic sack.
I use them, but would never tie a knot in one except under dire circumstances. It also could be critical to not use them in the belay in a position where the rope or anything else could come in frictional contact with them.
I have, on a number of occasions, taken a double length 8 mm runnner, used carabiners to clip to a two bolt anchor, and then tied a figure 8 into the doubled strands (a la a cordelette). Then clipped the bight with a biner and used it as a power point for a top rope anchor or for fixing ropes for jugging. I haven't noticed any issues with knotting the runners in this fashion.
|
|
TGT
Social climber
So Cal
|
|
|
Oct 30, 2006 - 08:02pm PT
|
I've cliped into plenty of anchors built the same way by partners. That's what got me thinking, especially if any testing has been done with that configuration with a loosely tied knot and shock loaded where the knot cinches down in an instant creating friction on the strands. Or, the cyclical loading that can happen on belay anchors in a semi hanging or hauling situation in particular.
I'll bet the girth hitch looked perfect till the instant it snaped also.
I like the shoe string runners and will continue to use them as such. But, I think I'll stick to the thicker ones for building anchors other than caribiner to caribiner applications.
I've used nylon string to saw thru PVC pipe and HDPE tanks on many occasions. It works faster than a saw.
|
|
MZiebell
Social climber
Prescott, AZ
|
|
|
Oct 30, 2006 - 09:17pm PT
|
"At times the sling may have been stored in the same pack as a Bosch battery."
vs.
"Sport Climbing Is Neither"
Hmmm...
Evolution happens?
: )
|
|
bspisak
climber
|
|
|
Nov 10, 2006 - 02:24am PT
|
Any further info on this?
|
|
Brian in SLC
Social climber
Salt Lake City, UT
|
|
|
Nov 10, 2006 - 10:08am PT
|
Excellant, K13!
Whew...makes me feel better...(I girth hitch and knot dyneema slings all the time...).
-Brian in SLC
|
|
couchmaster
climber
|
|
|
Nov 10, 2006 - 11:34am PT
|
Brian: before you breath too easy: the track which Joseph H. was sniffing down, was trying to answer the question:"What is the effect on aging on strenght of super thin Dyneema material?"
That is a different question than BD was asking which was: "What is the effect of girth hitching NEW Dyneema vs nylon sling material (and various combos thereof?"
I thought that the BD summation that Shermans slings may have been nicked ignores Josephs supposition, suspicions and suggestions concerning older Dyneema material and aging. I suspect JH is on the right track, and that we may have seen the first incident of this effect just take place with John Shermans slings.
A better test would be for some of you guys who climb a lot, like Werner or Ron O, to send in some well used, desert bleached, dyneema slings to BD and see what happens in those tests. Critical to the test would be knowledge of how old and how many climbing days/days out which the slings were subjected to.
To better view real world conditions girth hitch a skinny supersling that is 3 years old or older and been out a lot (Probably like Shermans was) and lets see what those numbers looks like. Maybe even run it over a rough surface when it gets pull tested to simulate real world conditions. Shermans slings may have had a rough surface against to rub against which may have excaberated the effect of aging and helped cause that clean break which the BD engineers are discussing.
Don't breath too easy until the age issue is looked at.
Joseph was talking about doing this test himself, but maybe BD can follow up and pull some old ones since they have the testing facility all set and gaged for it.
regards:
Bill
|
|
Brian in SLC
Social climber
Salt Lake City, UT
|
|
|
Nov 10, 2006 - 02:10pm PT
|
Just scroll down to the testing KP and folks have done earlier this year. UV light aging type data, comparing nylon to dyneema. The dyneema stuff seems to lose less percentage strength. Some great stuff in there. The old draws info is pretty interesting. Anyhoo, worth reading through the older testing info. I think he gets a ton of info on older spectra/dyneema, albiet quickdraws and wider material.
Yeah, didn't maybe exactly simulate John's debacle, but, gave me what I was really looking for.
There's no doubt that these thinner slings will have a shorter life. Just like a smaller diameter rope (ie a Twin v a Double v a single). It is going to be hard to retire them, though, as older nylon slings are hard to judge the age of, if they've been kept out of the elements.
I'll have to say, some of the first thin dyneema sling I've been using for over a year now is looking pretty dirty and a bit ratty. Maybe their while color will help highlight that issue more. Are gettin' fuzzy a bit too.
Can be hard to extrapolate some of this data, but, I did wig a bit when I saw that original busted thin dyneema sling. What I wanted to see was testing that I hadn't seen done before. Dyneema girthed to dyneema and nylon. What was neat was the drop test v the tensile (and somewhat unexpected). Pretty cool.
Anytime I knot a sling or a rope, I kinda mentally make a 50% reduction in strength.
Retire the thin stuff sooner: check.
-Brian in SLC
|
|
couchmaster
climber
|
|
|
Nov 10, 2006 - 04:24pm PT
|
OK I see that now: thank you. Guess I should have looked at the older data. It is still hard to tell what the superthin Dyneema/Spectra would look like in a few years: but this gives ya pause:
"March 15 , 2006 — Spectra vs. Nylon–Real World Wear
So I've been wondering how Spectra wears vs nylon slings. I'm currently working on an experiment, but until I get the results, check this out.
A guy here at work had two quickdraws sitting in the back of his open pickup truck for over 6 years. They have seen sun, snow, rain, heat, cold, etc, etc.. Fortunately for me, one was spectra, one was nylon. Ah ha....
Remember, when new, the rating for a sling is 22kN. Also remember that typical falls in the field are in the 2kN (sporto soft catch) to 5kN (harsh, kidney-wrenching) range.
The nylon sling (top) broke at 11.6kN
The Spectra sling broke at 5.3kN
Based on this as well as earlier findings (in emails below), it's looking to me like Spectra deteriorates moreso than nylon...and to the point that it's SCARY.
Bottom line—retire old beat-up gear.
Later,
Kolin"
They don't give out diameters of slings tested in that one or the draws tested in the other one. Given that the thin stuff (like Sherman had break) is generally pretty new, I suspect that it would not be unreasonable to get half that strength when it's that age, which means easy potential to break with bodyweight only when it's aged and well used. It looks like they plan on more testing of aged Spectra. I like and agree with the bottom line too: "Bottom line—retire old beat-up gear."
Nice job getting on this BD ! Thanks from us all.
|
|
healyje
Trad climber
Portland, Oregon
|
|
|
Nov 10, 2006 - 04:34pm PT
|
Bill,
Yeah, just replaced all my Mammut dyneema slings and am sending the old ones out to be tested and will post the results when I get them. I think we can all do a lot of girth hitch testing and find it hard to reproduce John's result under test conditions. My opinion is that our possible inability to reproduce John's result is completely secondary to the reality of what occured in this incident. I'd say take a second hard look at that close up photo - the sling didn't "break", it was clearly and cleanly "cut" on itself.
My take away is that these skinny slings are quite capable of doing that when girth hitched irrespective of the fact we have difficulty reproducing it. I suspect the diameter / size of what is being hitched is more than a little relavant as is how the hitch is "dressed" relative to 'how on edge' the sling is to itself. Bottom line - I wont be girth hitching skinny dyneema slings unless I feel so under the gun for some reason and never in a situation where it would be subject to a continuos load such that "sawing" could occur.
I've been climbing on the Mammut dyneema slings exclusively for three seasons now and will continue to do so, but I also have some of their 12mm versions and that's what I use at key clips. After two or three seasons I can feel enough irregularities in some of the slings to get the idea their at the end of their useful life. Also, these babies "fuzz up" hard with use as a result of fibers breaking and that alone is probably a fair indicator or remaining utility. I'm going to rate the "fuzz" factor of each sling and see how that correlates to tested strength so it will be interesting to see the results.
|
|
Brian in SLC
Social climber
Salt Lake City, UT
|
|
|
Nov 10, 2006 - 04:35pm PT
|
Those dyneema slings from Mammut haven't been on the market that long. Less than two years?
I could see if you left them outside in the sun for a while, but, most of us just expose gear to sunlight and weather when in use (ie, not fixed like some of the draws in KP's tests, or that old webbing from the back of a truck). Not that I don't run into crunchy old webbing at rap stations from time to time...
Good stuff, though.
-Brian in SLC
|
|
healyje
Trad climber
Portland, Oregon
|
|
|
Nov 10, 2006 - 04:40pm PT
|
I didn't get mine out of channel and this was my third season on them...
|
|
Brian in SLC
Social climber
Salt Lake City, UT
|
|
|
Nov 10, 2006 - 04:56pm PT
|
Anyone know how old the Sherman dyneema sling is?
It has a yellowish threader in it, which I don't recall as being in the first generation available (which was gray?).
-Brian in SLC
|
|
healyje
Trad climber
Portland, Oregon
|
|
|
Nov 10, 2006 - 05:09pm PT
|
I believe he said it was less than a year old and in good shape...
|
|
knudeNoggin
climber
Falls Church, VA
|
|
|
Dec 30, 2006 - 01:00pm PT
|
BUMP , 2006'last (nearly)
healyje wrote:
Yeah, just replaced all my Mammut dyneema slings and am sending the old ones out to be tested and will post the results when I get them. I think we can all do a lot of girth hitch testing and find it hard to reproduce John's result under test conditions. My opinion is that our possible inability to reproduce John's result is completely secondary to the reality of what occured in this incident. I'd say take a second hard look at that close up photo - the sling didn't "break", it was clearly and cleanly "cut" on itself.
Any results for the testing?
Btw, it's been 2 months since Mammut promised to investigate this--any results?
Frankly, I find all the scarmongering willingness to believe the most incredible
things about the slings to be way out of line. HMPE is notoriously hard to cut,
yet this sling showed a near razor-sharp cut line, and OUTSIDE OF THE KNOT
(which, by report testimony, was still tight post-break). At least one of those
who regularly tests cordage opined that such sharpness is UNcharacteristic of
breakage from loading alone. Looks to me as though someone with a knife
sabotaged the sling quite carefully. It sat up there from the 15th to break on
the 19th, recall.
Check the climerware site for various test results of HMPE slings with nylon;
there is no alarming result there. Shrinking the sling diameter if anything
ought to make knotting more dependable--the relatively wide aspect of
traditional tape is more awkward for knotting.
But try this: just interlock two slings a FEW times (vs. the ONE time of a "Girth"
Hitch)--and the structure should look like an extended Square knot (Surgeon's
Knot plus, actually), each sling equally twisting around the other. This is something
a bit beyond what Climerware's site shows; it is very simple to do, and very easy
to undo; it should be stronger, too.
*knudeNoggin*
|
|
Curt
Boulder climber
Gilbert, AZ
|
|
|
Dec 30, 2006 - 01:20pm PT
|
"...Frankly, I find all the scarmongering willingness to believe the most incredible things about the slings to be way out of line. HMPE is notoriously hard to cut, yet this sling showed a near razor-sharp cut line, and OUTSIDE OF THE KNOT (which, by report testimony, was still tight post-break). At least one of those who regularly tests cordage opined that such sharpness is UNcharacteristic of breakage from loading alone..."
When I got Sherman's original e-mail regarding this situation, I replied to him that I also thought the sling was cut--the edge where the failure occurred is simply too clean and straight for me to think othewise. Of course, it's quite a stretch from that conclusion to "sabotage" so I hardly think that is very likely. I do think it is possible that the sling was either partially cut before being girth-hitched, or that some piece of glass, sharp rock, etc. somehow became stuck inside the girth-hitch.
As for the OP observation that Verm is gaining weight--it's probably just the two new carbon-steel hip joints.
Curt
|
|
GOclimb
Trad climber
Boston, MA
|
|
|
Jan 22, 2007 - 06:40pm PT
|
Don't breath too easy until...
Frankly, I think a lot of us won't be breathing too easy for as long as there's no definitive explanation for what happened, because frankly, aside from the possibility that they were sabotaged or unusually cut by glass or something, none of the causes of breakage make a lot of sense. That is to say - there *is* a cause of breakage/cuttage that makes sense, but it's out there, unknown.
Reminds me of the case of the canadian climbers who's rope got sliced by something, likely inside the gri-gri, that was never quite understood or discovered.
GO
|
|
ricardo
Gym climber
San Francisco, CA
|
|
|
Jan 22, 2007 - 08:03pm PT
|
you guys do know that girth hitching 2 slings together lowers strength .. (quite a bit -- dont remember the stated ammount) ..
.. you'd have to be a little gutsy to girth hitch those skinny slings together for an anchor ..
|
|
couchmaster
climber
|
|
|
Jan 23, 2007 - 01:01am PT
|
It looks like girth hitching 2 together diminishes the stength at least 50%. Depending on who you look at.
Here is the Mammut observations about Shermans break:
http://www.rockclimbing.com/cgi-bin/forum/gforum.cgi?do=post_attachment;postatt_id=469;
It should be up on the Mammut site soon.
Here is Jim at Sterling Ropes observations who came in better: (Wootles on ST?) http://neclimbs.com/forum.php
"OK, so curiosity got the best of me...
I decided I would sacrifice one of my own 8mm Dyneema slings. I rigged up the drop tower with the skinny Dyneema sling girth hitched to a thicker 5/8" one which was Spectra/Nylon mix. Both slings were used.
I hung 100kg on it and then proceeded to bounce the crap out of it to simulate multiple (way over 150) small loads. The bounces were between 2 and 4 inches. I did this by hand by pulling the sling off axis and letting go. Not a lot of force but these were very static little drops; you wouldn't want 100kg to fall on your toe from 4". I stopped periodically to check the hitch and to give my arms a break. The hitch was warm but wasn't showing any signs of damage. It was starting to look obvious that the slings were not going to break, at least not any time soon, so I lifted the 100kg up about 8" and let it drop. The skinny sling broke but does not look quite the same as the one in Verm's pix. I did not measure the force but I have to believe Verm was not generating anywhere near the amount of force I was. Keep in mind he had a rope in his system and while it was static it would still have absorbed some force."
|
|
Mimi
climber
|
|
|
Jan 23, 2007 - 01:22am PT
|
Since no one has posted this yet today. Here's the latest from Mammut on the Verm sling-break incident. Sorry the pics don't copy over.
Hello all,
As you were all cc’d on this original email, I thought you might be interested in the results of our testing of this sling. I apologize in advance if any of you get this more than once, etc. The full report will be available within a few days on the Mammut website, hopefully by the end of the week. If anyone has any questions please feel free to let me know, and I’ll try to help.
Take care,
Dave
Dave Furman
Hardgoods Category Manager
Mammut Sports Group, USA
135 Northside Dr
Shelburne, VT 05482
(800) 451-5127
http://www.Mammut.com
Report on the Breaking of a Girth-Hitched Sling, prepared by Mammut Sports Group.
1/10/2007
Recently a girth-hitched Mammut 8mm Contact sling was broken in what was described as a relatively static, low-load application. The climber sent an email to many of his friends warning them of the possible danger of girth hitching the newer skinny slings, which quickly made its way around the inboxes and internet forums in the US.
After conducting a series of tests using static, dynamic and cyclic load testing to attempt to reproduce the conditions of the accident the broken sling was compared to the broken test samples using a microscope to examine the break characteristics, which are indicative of the mechanism of breakage. The broken sling did not exhibit any sign of chemical contamination, there was no melting of the fiber ends as is always the case in slings broken under load, the break was located outside the girth hitch rather than inside as would be expected if the knot were the source of the weakness, and the linear break very closely matched those achieved by cutting in the test samples.
Based on this and previous testing, climbers should be aware that the strength of any slings that are connected with a knot can decrease over 50%, regardless of size.
However, based on the fact that a UIAA certified sling holds at least 22kn (roughly 5000lbs), when girth hitched 880DaN or 2000lbs strength should remain in the worst case. With normal human weight and under the described circumstances of the accident, this force could only have been reached with a multi-meter drop. Because of the lack of melting and the lack of similarity to any of the tested breaks, we do not believe the sling broke due to any force applied to it, even taking into consideration the weakening effect of the girth-hitch. The most plausible scenario, borne out by the linear characteristics of the break and location of the break outside the knot, is that the sling was cut with a very sharp object. The only difference is the pulled thread—it seems plausible that this thread could have been the only one not cut through and therefore it held the anchor in place so it appeared to be intact, and finally it broke under a relatively low load.
Climbers should be aware that all slings, whether skinny or fat, Dyneema/Spectra or Nylon, are susceptible to significant strength loss due to a girth hitch, and should use any connecting knots with extreme caution. The safest way to obtain a longer sling is to carry and use a longer sling in the first place, rather than connecting them at all. If two slings must be joined, the strongest way to do so is with a carabiner.
Further information on this test report can be accessed on the Mammut website under Technology>Harnesses>Sling Report.
|
|
|
SuperTopo on the Web
|
Let us know!