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radtrad
Apr 6, 2007, 4:01 PM
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lets say you have to use two opposite and opposed biners in lieu of a locker, and the circumstance dictates you need to clove hitch them as if they were one biner.
if this a safe practice?
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scrapedape
Apr 6, 2007, 4:12 PM
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Why don't you run some tests, and report back.
That is the point of the lab forum, if I'm not mistaken.
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trenchdigger
Apr 6, 2007, 4:21 PM
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Yah, but I'm not sure the question ever really got answered there...
The clove will be a little more likely to slip a bit, but dressed and set properly, I wouldn't hesitate to attach a clove to two carabiners as I would to a locker in a system.
(This post was edited by trenchdigger on Apr 6, 2007, 4:22 PM)
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greenketch
Apr 6, 2007, 5:15 PM
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I don't know if it was posted in the other thread. but considering the loads and such it is worth shareing some annacdotal eveidence. In the Slackline world, which puts a big load on the anchors, it is a fairly common practice to clove two biners. This is used as part of the anchor and then afterwards by wiggleing them you can work enough slack easily into the knot to get it apart.
The major difference here is that slackers are tieing webbing and I am assuming that this discussion deals with rope. Big knot performance difference.
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binrat
Apr 8, 2007, 1:17 AM
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I've done this numerous times, just make sure that you dress the hitch properly first and you'll have very limited slip.
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knudenoggin
Apr 9, 2007, 7:16 PM
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An interesting/perplexing counterpoint to the evidence of the Clove H.
holding when tied around a *ring* (like-diameter object) in dynamic
rope is testing reported by Adam Fox of Fox Mtn Guides (-c- 2003).
He reports that there was slippage on a 10mm pin (not exactly a
'biner, but similar) at about 1_000#, and that "we had to hold the
free end of the rope as it was just sliding through the testing machine
off the pins." !?
*kN*
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coastal_climber
Apr 11, 2007, 5:38 PM
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There is nothing wrong, I do it when I am belaying a second. You can back it up with a figure 8 as well.
>Cam
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binrat
Apr 11, 2007, 7:29 PM
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kN:
At what load did it start to slip, and was that load a dynamic load or static?
Binrat
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mtnfr34k
Apr 13, 2007, 5:01 AM
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knudenoggin wrote: An interesting/perplexing counterpoint to the evidence of the Clove H. holding when tied around a *ring* (like-diameter object) in dynamic rope is testing reported by Adam Fox of Fox Mtn Guides (-c- 2003). He reports that there was slippage on a 10mm pin (not exactly a 'biner, but similar) at about 1_000#, and that "we had to hold the free end of the rope as it was just sliding through the testing machine off the pins." !? *kN*
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coastal_climber
Apr 13, 2007, 5:55 PM
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kN
Kilonewton. An abbreviation usually found on karabiners and other climbing gear. For those of you who are not engineers, one kilonewton is about 100 kg or about 220 lbs. (And for those of you who are, don't bother lecturing me).
>Cam
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bkalaska
Apr 13, 2007, 6:30 PM
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WHy bother with two biners? If you are clove hitching the knot isn't going to move an cross load a gate, or out of the basket. Just clove hitch one biner and you're safe. Use the other biner for your backup figure 8.
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rgold
Apr 13, 2007, 6:59 PM
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knudenoggin wrote: An interesting/perplexing counterpoint to the evidence of the Clove H. holding when tied around a *ring* (like-diameter object) in dynamic rope is testing reported by Adam Fox of Fox Mtn Guides (-c- 2003). He reports that there was slippage on a 10mm pin (not exactly a 'biner, but similar) at about 1_000#, and that "we had to hold the free end of the rope as it was just sliding through the testing machine off the pins." !? *kN*
Even more interesting and perplexing is that the Fox Mtn Guides site requires that candidates for their Rock Instructor course arrive with certain skills, one of which is tying the clove hitch.
A 10mm pin is pretty close to a biner. Why would they require a knot their own tests indicate slips completely free at 1000 lbf?
The test is not, as far as I can tell, reported on their site. No one else has reported anything like this in dynamic ropes. Static ropes have, however, slipped at 1000 lbf. Small amounts of slippage (eg 1/4 inch) have been reported in smaller diameter ropes before the knot tightens and holds.
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knudenoggin
Apr 13, 2007, 7:56 PM
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At what point does slippage begin? --pretty much as my post said, 1_000#
(+/-100#, reports Fox).
Is there a URLink? --maybe; Google suggets that cavers captured some
pdf of it:
http://www.caves.org/...-equal%20anchors.pdf
(I've not tried this. Some years back Adam posted in here--RC.com--and
by that info I e-mailed and got the report in hardcopy; there was/is some
DVD of the testing, in fuller bloom. Again, I see a copyright dated 2003.)
And Google also reveals some rather interesting indications re knots (what
is a "Patagonia" knot--a yuppy Yosemite bowline or something?)--to wit:
In reply to: FMG Climbing Equipment Materials Testing Last summer [2003? --kN] I managed to complete another long standing project, the materials testing DVD that will now be used on all the FMG AMGA courses and Climbing Anchors Courses in 2004. It was completed with help from our friends at Misty Mountain Threadworks here in WNC. Special thanks to Goose for helping out with this project! We managed to test pretty much every knot possible in the ongoing tests as well as various friction hitches in different diameters, materials and configurations (5-6mm cord, nylon and spectra webbing, Prusiks, Autoblocks, Klemheists, Kruzeclimbs[ !!], etc.). Figure eight’s, Overhands, Bowlines, Patagonia Knots (all were tested wet/dry in different diameters and rope types [dynamic, static and semi static] all were tested in different configurations). Runners, tied and sewn, wet and dry in different sizes and ages (from new to 12 year old samples and rotten old rapp slings were tested). Belay loops, and a harness was tested in the MMT harness tester. All results are shown in detail on the DVD!
There isn't that much information in the printed report I hold.
Btw, I'll interject (off topic) an observation about how biased some reports
get, with assertions/conclusions reached more by the strength of an agenda
than by support of results (such as those about dangers of "girth-hitching"
HMPE slings):
Fox's conclusion betrays a bias: "Samples 1, 2, and 3 show clear graphic
results; as steady increase in strength from girth, basketed, to straight
pull. This shows the reduction in strength when using a girth hitch in
your systems, and proves the theory that is should be avoided if at all
possible." !!! Really? (no)
Leaving aside the (unseen, really) exact orientation of material in
the Girth hitch, the resp. results of these structures are: 3_710, 4_870, &
5_672#. BUT the basket hitch uses TWICE as much material (each sling
is folded in half *basketing* the other); were that much expended for
a Girth Hitch, well, double its rating (=> 7_400# vs. 4_870).
(Put in material terms: with two 4'-long slings, the basket hitch will
extend 4', each sling, again, folded in half around the other at mid-point;
Girth-hitched, their combined length would be near 8', and THAT could
be folded in half, doubling the material then spanning the anchors, for
about double the sling-2-sling strength.)
But that wasn't what Fox wanted to "prove", apparently.
As for the Clove h. results, yes, RGold, surprising, etc.; I just relay the
report! But I'd certainly not want to depend upon the Clove holding,
and more so on wider/irregular objects (such as doubled 'biners),
and so have some back up, such as a simple Slipknot stopper or a collar.
Again, one would really like to know the exact details of the testing.
--kN*
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adamfox
Apr 13, 2007, 9:12 PM
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Hi,
Someone emailed me to reply to this forum, so I will do my best.
The tests in that paper were done around 2003 and many new results have come to light since then, more testing done and many things currently being worked on. I’ll try and quickly answer some questions raised. Yes there is a 30+ minute DVD that shows all the testing. No it’s not for sale, I use it for my courses when I have a DVD player available.
The Patagonia Knot is an original name for what many Americans call the ‘EKD’ or ‘Euro Death Knot’. Back in the early 90’s I found this in a very old European climbing manual and many European guides concurred with this original name.
The tests done at the Misty Mountain Threadworks labs back in 2003 were ‘static’ ‘slow pull’ tests, not dynamic loads. Slow pull tests are fine to look at differences in failures (how something fails) and generally gives you an idea, but of course climbers do not create loads above a few hundred pounds ‘statically’. All loads in climbing are dynamic. If only I had a drop tower!
The Cove Hitch did start slipping at around 900-1100lbs in our tests (again, slow pull tests). I have heard of many tests done since that mirror this result.
To answer why FMG requires the Cove Hitch for AMGA Programs is because it is a core knot that is used daily in many applications. Like everything in climbing it comes down to application of techniques, materials and equipment. A single Cove Hitch that would have to take a full dynamic load of a falling climber would be a bad application of this knot whereas using a Cove Hitch as an adjustable way to tie in to the anchor at a ledge would be a fine application. This is the way guides across the globe tie into the anchor.
Girth hitching greatly reduces the strength of a sling. The tests were done looking at the (obvious) dangers of girth hitching a 9/16 sling to a wired stoper. Results of girth hitching were around half the breaking strength of basketing the sling through. You should never girth hitch a wire stopper. Girth hitching materials reduces the strength of the material, basketing is a stronger way to connect two pieces of webbing. Again, girth hitching two slings is not ‘bad’ it is just a weaker way of tying two materials together. It comes back to ‘application’ of materials again.
Please contact me at via email if you have any questions.
Adam Fox
(This post was edited by adamfox on Apr 13, 2007, 9:45 PM)
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knudenoggin
Apr 14, 2007, 4:53 AM
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adamfox wrote: The Patagonia Knot is an original name for what many Americans call the ‘EDK’ or ‘Euro Death Knot’. Back in the early 90s I found this in a very old European climbing manual and many European guides concurred with this original name.
some suggestion that the moniker implies something that looks good
but isn't--to which one reply was that the EDK ("OOB"!) is the opposite.
In reply to: The Cove Hitch did start slipping at around 900-1100lbs in our tests (again, slow pull tests). I have heard of many tests done since that mirror this result.
well (or not) they were performed. The Lyon Equipment testing done
for the UK's HSE ca. 2001 (IIRC) is one known one that found slippage
in the few low-elongation/static ropes yet not in one dynamic rope.
But here is another, which mentions AMGA, also:
http://guidetricksforclimbers.com/cloveHitch.art.html
Note that it, too--as for yours & Lyon's--is by slow pull.
In reply to: Girth hitching greatly reduces the strength of a sling.
look at the testing done by Black Diamond's (then) Chris Harmston and
Tom Jones for SuperTape (11/16") & 5/8" HMPE, you find assertions of
about 70% efficiency--which is roughly that for tying the tape to
form a sling. But one doesn't hear the same level of ranting about
Water knots! (Karl Lew's results on his Climberware site have some
peculiarities that need careful attention, though.)
In reply to: The tests were done looking at the (obvious) dangers of girth hitching a 9/16 sling to a wired stoper. Results of girth hitching were around half the breaking strength of basketing the sling through.
given, say, a 3_000# load (the break point you report), that's a tension
of 750# on each side; with the Girth H., it's 1_500# (not surprising then
that the GH break you got was 1_615#).
In reply to: You should never girth hitch a wire stopper.
In reply to: Girth hitching materials reduces the strength of the material, basketing is a stronger way to connect two pieces of webbing.
Climerware test for a nylon sling tied through a sewn HMPE one:
this is essentially a basket structure with one course of material;
it was much weaker than a Girth hitch (about 75% of GH).
Why do people GH slings? --to lengthen them. If the 4' sling isn't long
enough, you'd need at least three to reach farther by basket connection,
as each is folded in half; that would be stronger (but shorter by a quarter)
than GH'ing two. But if you can spare a trio of slings then GH'ing them
one to the next and then making one big basket of this conjoined sling
would be over 30% stronger--your numbers, btw.
(length figuring noted above is: 3x(4'/2) = (3x4')/2)
And beyond all of this is the continual confusion about the geometric
form of the different things denoted by "girth hitch"--look at those
in Climerware & the Sherman sling's knot and Kolin's knots (somehow
mostly missing what Climerware shows). Mostly, it's a difference re
whether the so-called "girth hitched" sling comes back to collar
itself (as it must around a solid straight object like a tree or 'biner),
or intead reaches farther around the hitched object (like a square knot).
The method of tying can lead directly to the latter or variously give
the former, sometimes capsizing into the latter, sometimes not.
Why this obvious difference goes unremarked just baffles me!?
*kN*
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adamfox
Apr 14, 2007, 11:33 AM
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Looks like you have a vast amount of experience testing materials. Could you please supply links to your testing and any papers you have written as I am always interested in new material.
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rgold
Apr 15, 2007, 12:17 AM
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adamfox wrote: The Cove Hitch did start slipping at around 900-1100lbs in our tests (again, slow pull tests)...A single Cove Hitch that would have to take a full dynamic load of a falling climber would be a bad application of this knot whereas using a Cove Hitch as an adjustable way to tie in to the anchor at a ledge would be a fine application. This is the way guides across the globe tie into the anchor.
I'm a little concerned that you seem to think this knot is called a "cove" hitch. Did you test something different from the clove hitch?
In any case, a guiding scenario:
There is a fixed pin 40 feet below the belay. The client, who is out of sight of the guide, climbs 10 feet past this pin without unclipping, and then falls trying to recover. The result is that the client falls 20 feet with 50 feet of rope out. If the client weighs 80 kg and the rope has a UIAA rating of 8.5 kN, the result is a 1,000 lbf jolt to the guide's belay.
Although this scenario may be unlikely and the guide might be criticized for letting it happen, anyone who has guided knows that this nightmare is not at all impossible.
But never mind---how about this: as the client is almost at the belay, the guide sneezes. During this allergenic moment, the client steps up and then falls before the booger-encrusted guide can take in the slack. There was 5 feet of rope from guide to client, and the upward step left a foot of slack hanging down from the client's waist. Boom, client falls two feet on five feet of rope and once again the guide experiences the 1,000 lbf jolt of a factor 0.4 fall.
How then, can a guide be practicing due diligence if he is tied to his or her anchor with a knot that slips catastrophically at 1,000 lbf?
It seems to me that if this slippage result is accurate, then dire warnings should be widely promulgated and everyone (including most of Europe if the posts on another thread are accurate) should stop anchoring with a clove hitch. Catastrophic slipping at 900-1000 lbs is not acceptable.
adamfox wrote: I have heard of many tests [emphasis mine] done since that mirror this result.
Knude asked you for references for this claim. (I'm sorry that your response was instead to ask him for references for claims he hasn't made.) Some of us have looked for test results on clove hitches and, except for the report about yours, have not found any tests, much less "many tests," that confirm clove hitches slip (more than, say, 1/4 inch) in dynamic ropes. Please help us out with some references to these "many tests" you know about!
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timm
Apr 15, 2007, 2:39 AM
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rgold wrote: In any case, a guiding scenario: There is a fixed pin 40 feet below the belay. The client, who is out of sight of the guide, climbs 10 feet past this pin without unclipping, and then falls trying to recover. The result is that the client falls 20 feet with 50 feet of rope out. If the client weighs 80 kg and the rope has a UIAA rating of 8.5 kN, the result is a 1,000 lbf jolt to the guide's belay. Although this scenario may be unlikely and the guide might be criticized for letting it happen, anyone who has guided knows that this nightmare is not at all impossible. But never mind---how about this: as the client is almost at the belay, the guide sneezes. During this allergenic moment, the client steps up and then falls before the booger-encrusted guide can take in the slack. There was 5 feet of rope from guide to client, and the upward step left a foot of slack hanging down from the client's waist. Boom, client falls two feet on five feet of rope and once again the guide experiences the 1,000 lbf jolt of a factor 0.4 fall. How then, can a guide be practicing due diligence if he is tied to his or her anchor with a knot that slips catastrophically at 1,000 lbf? It seems to me that if this slippage result is accurate, then dire warnings should be widely promulgated and everyone (including most of Europe if the posts on another thread are accurate) should stop anchoring with a clove hitch. Catastrophic slipping at 900-1000 lbs is not acceptable.
While this scenario may happen, you are making one very false assumption that makes your argument silly ... You are assuming the guide is belaying off his harness. Every guiding course I've taken and every guide that I've worked with will, in almost all circumstances, use a direct anchor belay. There are so many more advantages to this than belaying off your harness regardless of whether the guide's tie-in knot is a clove hitch, figure 8, or something else.
Why would I want to have a client hanging off my harness in this scenario or any potential rescue scenario when attaching a gri-gri, cinch, ATC guide, or reverso on that anchor in autoblock mode has so many more advantages plus makes my tie-in knot irrelevant ??
Furthermore, this source
http://guidetricksforclimbers.com/cloveHitch.art.htm
has test data that disputes the 1000 lbf slippage of the clove hitch.
(This post was edited by timm on Apr 15, 2007, 2:41 AM)
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adamfox
Apr 15, 2007, 1:09 PM
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I am dyslexic (really), I was referring to a Clove Hitch. I had to smile when I noticed I referred to the Euro Death Knot as an ‘EKD’ in an earlier post even though I checked it many times for accuracy!
In reply to your post, the guide belays directly from the anchor using a plaquette device so your scenarios would not be a problem or relevant to someone connected to the anchor with a Clove Hitch. Again the Clove Hitch was ‘slipping’ at 900-1100 lbs, not “catastrophically failing” and again, these were slow pull, static loading tests not dynamic drop tests.
Timm; I know Alan and SP so I’ll call Alan over the next few days to talk with him about SP’s results. Good info.
For more info please email or call me direct (you can get the number from my website) and I would be happy to discuss this topic.
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timm
Apr 15, 2007, 1:23 PM
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adamfox wrote: Timm; I know Alan and SP so I’ll call Alan over the next few days to talk with him about SP’s results. Good info.
Adam, I spoke with Alan just this past week in JT about this conflicting data and his pull test results regarding clove hitch slipping. He verbally confirmed them to me again. I'll probably see him again this week in JT and I'll give him a head's up about this discussion. He mentioned that he has a buddy at some university with access to a pull machine and he was going to have him run a bunch of testing experiments for him.
Maybe we need a clarification about "slippage" versus "catastrphically failing" and "knot failure" that are used in these pull tests results.
Cheers.
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rgold
Apr 15, 2007, 6:30 PM
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timm wrote: While this scenario may happen, you are making one very false assumption that makes your argument silly ... You are assuming the guide is belaying off his harness.
adamfox wrote: In reply to your post, the guide belays directly from the anchor using a plaquette device so your scenarios would not be a problem or relevant to someone connected to the anchor with a Clove Hitch.
Yes, quite true, the assumptions are wrong, sorry about that---I've never been a fan of belaying off the anchor myself.
But the argument isn't even remotely silly, and saying so misses the point by redirecting attention to belaying styles. The point is that a knot that slips continually at 1000 lbf is not appropriate for tying in, period. It isn't hard to generate 1000 lbf on an anchor. Please don't make me continually make up plausible scenarios until we get one that guides and other climbers understand they could encounter. Is it inconceivable that someone could drop one foot with an anchor tie-in length of 2.5 feet, for example? Why bother to construct a proper anchor if the connecting knot continually slips at a lower load than even one of the pieces?
timm wrote: Furthermore, this source http://guidetricksforclimbers.com/cloveHitch.art.htm has test data that disputes the 1000 lbf slippage of the clove hitch.
We are well aware of that source, which has already been quoted in this very thread, as well as others that dispute this finding. Based on years of personal experience, including at least one time when I know the clove hitch withstood more than 1000 lbf impact, I am very sceptical of this result. Indeed, part of the point of my posts is that it appears to me that those who obtained this result don't believe it either, otherwise I don't think they'd be using a clove hitch for any anchoring purpose.
But whatever my or others' experience has been, we know that an enormous amount of what climbers call experience is just the ignorance of potential problems caused by good luck. This finding adds a very serious question mark to the issue of anchoring with a clove hitch, and I think it is extremely important to figure out how much confidence we should have in the result.
adamfox wrote: Again the Clove Hitch was ‘slipping’ at 900-1100 lbs, not “catastrophically failing”
A fine point, perhaps, is that I said "catastrophically slipping," not catastrophically failing. Knude quotes either the report or Adam's original posting as saying "we had to hold the free end of the rope as it was just sliding through the testing machine off the pins." That's why I referred to catastrophic slipping. Is this quote incorrect?
timm wrote: Maybe we need a clarification about "slippage" versus "catastrophically failing" and "knot failure" that are used in these pull tests results.
I'm sure clarifications would be helpful, since all knots slip. Any knot tightens under load, and if the extension of the ends is called "slippage," that would be of no concern. On the other hand, is there a definition of catastrophic failure that would exclude the unrestrained running of the rope through the anchor point?
adamfox wrote: these were slow pull, static loading tests not dynamic drop tests.
A fact that could be significant. A thousand-poundforce impact load for less than a second is different from the same load continually applied over time. If the difference is significant enough, then we shouldn't be using slow-pull tests at all, except in order to understand the effect of rescue loads. Unfortunately, not many people have access to drop towers and the dynamic load cells needed to measure instantaneous peak forces, whereas hydraulic pulling devices are relatively easy to come by.
This reminds me of the joke about the man who loses a ring in the street at night and walks 100 yards to search for it under a lampost. When asked why he is looking so far from the site of loss, he replies, "because this is where the light is."
adamfox wrote: For more info please email or call me direct (you can get the number from my website) and I would be happy to discuss this topic.
It is better to do it here. There are a number of people with a lot of expertise and substantially different perspectives who will be able to contribute to a public dialogue, which is what this has become. Private communication for the edification of individual understanding seems less important and less effective in ferreting out whatever the truth turns out to be.
Finally, we are all still waiting for references to the many tests mentioned by Adam that confirm that clove hitches in dynamic rope slip (presumably in a non-trivial way) at 1,000 lbf loads. Adam? Please?
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cintune
Apr 15, 2007, 7:35 PM
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rgold wrote: A thousand-poundforce impact load for less than a second is different from the same load continually applied over time.
Yeah, especially with a clove; if it's firmly set at the moment of impact it should pretty much weld itself solid rather than slip. if not, all bets are off.
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knudenoggin
Apr 16, 2007, 7:14 AM
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--a few things here.
I brought up the Fox testing of course as a counterpoint to the non-slip
results found in at least the other site I quoted (also Lyon, in the Beal
dynamic rope they tested), and general experience. (RGold, in your
latest post above, you confuse the non-slipping ref. w/Fox's.)
As for this force maybe being for "for less than a second", I recall some
old Chouinard catalogue reported test data showing that, while the peak
force of falls depended upon Fall Factor (for climbing ropes, at least),
the duration of this force increased with fall length--but I don't
recall the rough range of durations reported.
Lest there be misunderstanding from Adam's remarks, ALL of the cited
TESTING here is of the slow-pull sort--so comparisons between them are
warranted; and caution about how well they model in-use behavior is
needed, too.
The quote "we had to hold the free end" is verbatim (makes me think they
were long ends--I'd not want my hand close to a rupture-tested rope!).
And part of the point of citing contrary results is to make that point about
variety there, as often it seems that one reference pops up and some folks
are ready to justify the world upon it (upon HEARSAY of it--hardly going
for first sources, etc.).
The OP is about the Clove Hitch and here we come in discussion to more
an issue of method & variance & ... . But this makes it all the more apt
for being in "The Lab", and so I think it not too much a hijack to remark
at maybe a more surprising result highlighted by Fox, though it's really
one of degree vs. the somewhat binary slip/no-slip for the Clove.
For the most part, test results I see show the Fig.8 loopknot to be well
stronger than the Overhand LK; but Fox finds in ten tests of A vs. B sort
(the two knots opposed at opp. ends of the test specimen) an equal split!
At this very moment in other parts of the ether LifeOnAline author has just
opined that the overhand is pretty much "a 50% knot"--no matter how
loaded (his point there being that Fig.8s & 9s & 10s can vary w/load rate).
The Lyon testing, too, put a clear bit of results space between the two
loopknots, and tested some of them with either end loaded. (From the
Fox report image it appears that both were loaded with what has been
called "weak form", with the end making the more interior path,
and so sort of pulling away from--instead of into/against--its
twin strand. Lyon, it seems, calls this "on top of" or not, though their
explanation would do well with an unambiguous graphic!)
And the CMC Rope Rescue Manual actually reports a higher figure (85%!)
for the Overhand LK (to the Fig.8's 80% & 79% (yes, by golly, they (also)
actually tested "on a bight" AND "follow through"))--which to my eye looks
like a transposition of digits in the average, which would then put it in the
60% range. (But Jim Frank never (yet) got back to me re digging up the
data.)
. . .
Ahhh, nothing quite like "the hard facts"!
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