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lobito
Sep 28, 2002, 12:06 AM
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I've heard that the water knot tends to slip under a cycling load. I'm wondering if this is still true if backing up the free ends with double fisherman's
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wlderdude
Sep 28, 2002, 12:22 AM
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What kind of cylical loading do you plan on doing to the webbing? Regular climbing won't do that to nylon webbing.
Protocol calls for at least 2" tails on nylon webbing to compensate for any unforseen slipage. I usually use more.
Knoting specta is not advised by the makers of it, regarless of cylical loading or not.
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lobito
Sep 28, 2002, 12:27 AM
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I was thinking about lowering while top-roping. Or that does not stress the anchor too much to worry about the knot?
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apollodorus
Sep 28, 2002, 1:09 AM
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It takes hundreds of loading cycles to get the water knot to slip past 2" tails. All you have to do is visually make sure that the tails are sticking out each time you use the sling.
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wlderdude
Sep 28, 2002, 2:05 AM
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If you are leaving tails, you do not have to worry about the knot pulling throuh.
Just make shure you are lowering through a biner or rap ring, not the webbing itself. Nylon rubbing on Nylon mean heat and that means bad stuff. Like death.
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winkwinklambonini
Sep 28, 2002, 2:45 AM
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Don't forget the reason it's called a waterknot, soak it to get it nice and tight. that'll help with loading cycles
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xcit
Sep 28, 2002, 3:32 AM
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I also double fisherman my waterknots as "back up"
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caerbannog_rabbit
Sep 28, 2002, 5:16 AM
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i ALWAYS use a back-up knot, but maybe im just too cautious
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djnibs
Sep 28, 2002, 3:48 PM
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hey, i just leave long tails. atleast 4" minimum. the knot hasn't slipped yet. good luck
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socialclimber
Sep 29, 2002, 12:07 PM
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You could put a stitch through your tails as an alternative to a back up knot. dental floss works well cause it's waterproof and cheap.
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coclimber26
Sep 29, 2002, 1:25 PM
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The UIAA did some testing with the water knot after several climbers were found dead with half a water knot in a sling. They found it wasn't the water knot slipping, the knot had been placed against a rock nub and under the weight of a rapeller it would wedge under the bandsling and work itself loose. so keep the knot away from the top, keep atleast 3" of tail and try not to use spectra with the knot because it has less of a holding strength. The knot reduces the overall strength of the sling by 55%. So if your bandsling was rated for 10kn then the strength at the knot would be 5.5kn.
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jamison
Sep 30, 2002, 6:25 PM
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My understanding the of the waterknot is that it slips 1000ths of an inch per cycle. However, for some reason is slips easier under low loads. I don't quite understand this except that maybe as the load increases, the knot tightens on itself and tends to hold better.
the point is, long tails are great. Check it often (after each climb). And tie safety knots. I use overhands.
I completely agree with keeping the knot away from objects that can push on the knot. That is good advice in general. When things are tested in laboratories, they ususally take simplified situations, so it is likely that no one really knows what happens to a knot when it is being resisted by something.
I think the key thing with waterknots is to only use them for temporary anchors. Not for slings for nuts or cams or whatever else.
Jamison
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monkeyarm
Oct 13, 2002, 7:16 PM
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From what I have heard the waterknot losens and can come undone due to the fact that weighting and unweighting the webbing causes the webbing in the knot to oscilate and loosen the knot no matter how tight it is tied. And once the knot it loose it is very easy for tails to slip through.
This is why NOLS requires ridiculously long tails on waterknots. You generally want to tie a backup knot if the webbing is going to be left tied for a while, or leave at elast 3-5in of tail if the knot is only going to be used for a short time.
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tigerbythetail
Oct 15, 2002, 7:38 AM
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Tying double fisherman knots in your slings is a good way to make sure they stay knotted.
Keep a few slings with water knots in case you need to thread something.
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pbjosh
Oct 15, 2002, 8:38 AM
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Water knots DO slip under cyclical loading. Tie them with reasonably long tails (2-4") and keep and eye on the tails. They're easy to retie longer if necessary. Cinch them down pretty well. I always carry a tied sling or two for rappels and the like. I've used a ton of them in anchors, etc and have on two occaisions noticed clear slipping after a lot of use where they were loaded/unloaded repeatedly. As with all your gear, keep an eye on it. This one is super easy to catch. I usually end up retieing them around/through something and rapping off them before this happens but like I said I've seen it twice and retied them with the tail length restored... and I do tighten my water knots pretty tight. Backup knots will work but require longer lengths of webbing and make it harder to untie/retie for a rap - no biggie really but I personally do not backup water knots.
josh
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ephemeral
Oct 16, 2002, 7:28 AM
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What about the Beer Knot?
It's a lot stronger than the Water Knot and will not slip. Tastes better too!
Check it out at:
www.beerknot.20m.com
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gearweenie
Oct 19, 2002, 10:44 PM
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You should buy sewn slings for general use and tie only for toprope anchors or when you need to cut wone of your sewn slings in an emergency, You should always be rechecking your knotted gear and it is fine without a backup knot.
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dadvntur
Jul 27, 2008, 1:57 PM
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Hello,
I was unsuccessful in finding this UIAA Water Knot study you referred to. It is not one of the twelve downloads/studies available in the 'Safety' section of the UIAA website. I know it has been almost six years since you posted the following reply to the "Water Knot" thread, but do you happen to know where I could find this UIAA study?
"water knot [In reply to] Quote | Reply
--------------------------------------------------------------------------------
The UIAA did some testing with the water knot after several climbers were found dead with half a water knot in a sling. They found it wasn't the water knot slipping, the knot had been placed against a rock nub and under the weight of a rapeller it would wedge under the bandsling and work itself loose. so keep the knot away from the top, keep atleast 3" of tail and try not to use spectra with the knot because it has less of a holding strength. The knot reduces the overall strength of the sling by 55%. So if your bandsling was rated for 10kn then the strength at the knot would be 5.5kn."
I ask account I'm curious as to the application of the studies findings in reference to a "Tree Anchor: Knot Location" thread (?) I've recently posted.
Thanks for your time.
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knudenoggin
Jul 31, 2008, 3:52 PM
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[quote "lobito"]I've heard that the water knot tends to slip under a cycling load. I'm wondering if this is still true if backing up the free ends with double fisherman's[/quote]
The most common cyclic, light loading that climbers will see is rapping
--forces are variable & relatively low.
I'm aware of two studies of this--one is on-line at:
www.xmission.com/~tmoyer/testing/
(or it was). A follow-up study covered some different tapes. What was
found was that cyclic slippage occurred at relatively low loading in SOME
of the tapes--not in new 1" tubular, in one case; some in 3/4" solid and
some Spectra tape. These otherwise held w/o slippage on hard loading
(contrary the rumors re HMPE/Spectra).
So, YMMV. One tester mused that material stiffness is a key factor.
AND, the slippage occurred in ONE end--the exterior end (i.e., that
of the tape whose color dominates the knot, lies on the exterior of
the parallel tape).
You do not back up knots with a "Grapevine" or "Dbl.Fish.",
but (what is meant, i.e.) a "Strangle" knot.
A dressing variation of the Water knot that I devised in order to remove
there being any exterior end is shown in The Lab as one of the knots
tested in webbing. But, it hasn't been tested much, and not for this
cyclical slippage. At least it shows no great problem in this one test.
As for the Water knot being vulnerable to being physically loosened
and untied by contact with some protuberance, I heard that this was
testing done by the German alpine organization DAV. And I remain
skeptical about this, but in any case one should be attentive and careful
about where the knot is placed, about what it my contact under load
(as illustrated in another thread here about HMPE slings being worn
at the point of a "Girth Hitch" joint).
*kN*
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