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redpiton
Apr 9, 2003, 12:37 AM
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I heard from a NOLS climbing guide that they are not using waterknots anymore to join two ends of webbing...Has anyone else heard this? Apparently waterknots can "slip" and deaths have occured. Granted I did not ask this fellow for a NOLS badge or any type of proof, but he's a climbing instructor at a Vermont College as well...Anyone heard of this? I'm still going to use my waterknot but I didn't know if he was blowing smoke up my tailpipe.. :wink:
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calpolyclimber
Apr 9, 2003, 1:14 AM
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As far as I know, water knots are still the knot of choice for joining webbing. They can/do slip SLOWLY with time, but this is a very gradual thing. They do not just slip all of a sudden. As long as you tie them with LONG tails, and keep an eye on them, they are the way to go.
Alex
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1269topper
Apr 9, 2003, 5:48 AM
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This guy said water knots are bad what did he suggest instead. I never had much kuck removing any other knot out of webbing? I would be interested if anybody has a opinion about this.
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cliffhanger9
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Apr 9, 2003, 6:11 AM
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this is the first i have heard this (yeah i ll keep usin it) but if u can make the tails longer that will help as mentioned above especially if u took those long ends and tied like a double fishermens with them :idea:
wait...now that i think about it, this prolly wouldnt work with webbing to well...nevermind...
i also would be interested in what they DO recommend if this is no longer acceptable :?: :!: :?:
ROCK ON!! http://66.227.101.70/otn/tongue/tongue3.gif
PS - y is this in the East Coast forum?...just curious...
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coldclimb
Apr 9, 2003, 6:17 AM
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I've read that they slip too, but they're still the only/best knot I've seen for the job. A variation that I have seen that supposedly eliminates slippage is using tubular webbing, tying the overhand, then threading one end through the other and moving the knot to the middle of the doubled section and tightening it. This seems logical to me, but I read it on this site, and I have no absolute confirmed proof, so correct me if I'm wrong. ;)
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climb4life
Apr 9, 2003, 6:22 AM
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that's really odd hearing from an instructor choosing not to use a waterknot. i am on a search and rescue team, and we use webbings all the time. i use waterknots for the job. just make sure the tail is long enough and keep an eye on it. never had a waterknot failed on me. if you see or hear from that guy again, ask him what kind of knot he uses for webbings. but it sounds to me that he is pulling your leg. but then again, if there is a new knot, i would like to learn about it.
climb on
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apollodorus
Apr 9, 2003, 6:57 AM
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Under many repeated loadings, the water knot in nylon webbing tends to work itself loose, with the tails becoming shorter and shorter. It does not slip under a single, high load. So, leave the tails out a bit, and keep an eye on them. The water knot is rather easily retied (tap the knot with a hammer, and it will almost fall apart in your hands).
I've also used the double fishermans for webbing, but it is nearly impossible to untie if you want to. For example, you might want to untie a runner to add to a group of faded, crusty and dangerous belay/rap slings, something you run into all the time.
Another thing, don't use the water knot for spectra webbing. That stuff is not nylon, but polyethylene. For you plastics chemists out there, polyethylene is in the same family as teflon, and is almost as slippery. A triple fisherman's knot is usually recommended for spectra. Spectra also degrades faster in sunlight than nylon.
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pico23
Apr 9, 2003, 8:18 AM
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:shock: cyclic loading. there have been actual test by competent people and below is the summary of the testing. as you can see it takes 806 cycles for the top 3 inch tail to pull through. Thats a lot of cycles. If you think you'll be putting that many cycles on the knot put the recomended overhand safeties in. The water knot is a bomber knot and one of the safest in terms of knot strength.
Test Methods
I used a small MTS load frame to pull on a loop of 9/16" tubular webbing tied with a water knot. The load was
cycled from 0 to 250 lbs at a fairly slow loading and unloading rate (about two seconds per cycle). Loads and
extensions were measured directly by the load frame. The test was halted automatically upon failure of the knot.
Results
The test showed consistent slipping of one of the tails into the knot at an average rate of 0.0035 inches per cycle. A
knot that started with tails almost three inches long had one tail gone after 806 cycles. It was interesting to note that
only one of the tails slipped into the knot - the one on the "top" side of the knot.
A test with overhand safeties on the water knot gradually slipped through 1.75 inches of tail, and then cinched and
did not slip any further. Interestingly, the slip rate was not linear as in the first test, but decreased as the safeties
gradually tightened.
A loop tied with a water knot was loaded with a static pull of 200 lbs to check whether the knot was slipping by
creeping. The test was run for thirteen minutes. After an initial period of setting the knot, no further slipping
occurred. The water knot seems to be affected by loading and unloading, not by a static pull.
Another cycle test was done on a loop tied with a single fisherman's knot. Over the first 1000 cycles, the loop
elongated by 1/4 inch as the knot set. After that, no further elongation occurred. The test was discontinued at 1630
cycles.
In reply to: Under many repeated loadings, the water knot in nylon webbing tends to work itself loose, with the tails becoming shorter and shorter. It does not slip under a single, high load. So, leave the tails out a bit, and keep an eye on them. The water knot is rather easily retied (tap the knot with a hammer, and it will almost fall apart in your hands). . |
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apollodorus
Apr 9, 2003, 9:11 AM
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Nice work Pico23. I've seen similar results from cyclically testing the water knot.
Did you use 9/16" nylon webbing?
A similar test using Spectra would be enlightening.
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redpiton
Apr 9, 2003, 7:41 PM
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The guy said that a Figure 8 is his knot of choice for webbing, but at this point I choose basically not to listen as intently...Thanks for the replies. I will continue to use the water knot. I think he was mainly meaning the layers upon layers of water knotted webbing at the belay and rap stations at the gunks for instance. I always feel queasy rapping on them anyway... :roll:
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mother_sheep
Apr 9, 2003, 7:49 PM
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I know this discussion is about the water knot but I'm wondering about the durability of the double fisherman's knot vs. the water knot. The double fisherman is my knot of choice when rapping with double ropes. Is the water knot stonger or just as strong?
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bandycoot
Apr 9, 2003, 8:02 PM
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Tracyroach:
You're talking two different knots and two different lines. The double fisherman's is for round rope and the water knot is for flat webbing. The water knot is NOT something that you should use when attaching two ropes together, instead use the similar but oh so different European Death Knot. The water knot is pretty damn uber. I stopped using webbing because I really don't enjoy those rare occasions where I have to untie the water knot. Now I use it only when I HAVE to. I love cordelette!
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tori
Apr 9, 2003, 8:04 PM
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like they said, the water knot is great but you must watch the tails. guides may be becoming more sensitive to this because of some accidents in north american mountaineering last year. in one accident a guide had a water knot in a sling that he, evidently, rarely checked and he dropped a client when it failed. i think there were other stories about guides falling while setting up top ropes because their old water knots failed as well. maybe some guides have so much gear and whatever going on that they don't want to worry about checking a water knot so they use something more permanent, and bigger. if you pay any kind of attention to your gear it will be easy to handle the water knot tails.
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rodeomountain
Apr 9, 2003, 8:10 PM
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Why don't you just use the double fisherman's knot?
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*thriller*
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Apr 9, 2003, 8:26 PM
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I've always tied webbing using a double fishermans's know because when i was just starting i was told that this is the only real safe knot to use and that the water knot is known to slip. It has to be the most difficult knot i have ever had the unpleasantness to untie. after reading pico23's post i'll have no hesitation to use the water knot - but i will use overhand safeties just to be sure.
i normally use 1" tubular webbing, not the 9/16th" tested, but which would you think would slip faster?
another issue with knotted webbing is that the webbing is strongest when it is flat, with the weakest point being where it is knotted. it'd be interesting to see whether the double fisherman's knot creates a weaker stress point than the water knot since it cinches the webbing tighter. anybody have any thoughts on this?
edited because i can't spell :?
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cheaterstick
Apr 9, 2003, 8:39 PM
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I haven't heard of them slipping, but I think I know why they changed their minds. Water knots are great ONLY FOR NYLON WEBBING. Perhaphs the prevalence of "exotic" materials caused them to start recommending another knot (double or triple grapevine??)
Just a thought :wink:
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wrenrunner
Apr 10, 2003, 10:17 PM
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I have figure 8 knots on all of my webbing because they rarely if ever fail. I still tie and safty barrel know with the tails, and i would definetly tie a safety knot if i tied the webbing using a water knot. I try to be super safe, but in a way that it's not aggravating!! :wink: :D
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pico23
Apr 11, 2003, 3:16 AM
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In reply to: I have figure 8 knots on all of my webbing because they rarely if ever fail.
Can you explain how you tie the figure 8? I know a lot of people assume because the figure 8 is the usual tie in knot it is safe for everything but in many cases it is the wrong knot and often unsafe. I've never heard, seen, or read of tying a figure 8 into webbing I'd like to see a reference to the safety of the figure 8 tied into webbing. Waterknot or grapevine (fishermans) are the only two knots I understand to be safe and effective on webbing.
Thanks for the info.
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pico23
Apr 11, 2003, 3:25 AM
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In reply to: Nice work Pico23. I've seen similar results from cyclically testing the water knot. Did you use 9/16" nylon webbing? A similar test using Spectra would be enlightening.
I didn't perform the test myself. I apologize. They were performed by a Sherrifs SAR team in California or Nevada. I appologize for the appearance that I did the test myself although I didn't intend for that to be the appearance.
From what I understand the cycles involved in the shortening of the top strand are not greatly affected by the webbing size. I think we can all be sure that the waterknot is safe with NYLON webbing. With spectra (dyneema) I've seen valid test that state the safety of knots is actually much better then manufacturers and climbing instruction books will have you believe. However, tying these slippery materials is less safe then nylon.
Also remember that it is really important that all knots be cleanly dressed. The water knot (or overhand EDK) should be flat and neet. No twisted or loose strands. This will lead to increased slippage and possible knot failure.
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mike_ok
Apr 11, 2003, 3:58 AM
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stupid question, but i never know the names of knots... i just tie them. the water knot is an overhand on oneside, with the other end threaded through in reverse, then cinched tight, right? If not, whatever knot I just described is the knot I use with webbing, and never had even a hint of a problem.
Someone please confirm or invalidate my lack of education please ;-)
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bsignorelli
Apr 11, 2003, 4:06 AM
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Sounds right.
In reply to: stupid question, but i never know the names of knots... i just tie them. the water knot is an overhand on oneside, with the other end threaded through in reverse, then cinched tight, right? If not, whatever knot I just described is the knot I use with webbing, and never had even a hint of a problem. Someone please confirm or invalidate my lack of education please ;-) |
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wrenrunner
Apr 11, 2003, 11:13 PM
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In reply to: Can you explain how you tie the figure 8? I know a lot of people assume because the figure 8 is the usual tie in knot it is safe for everything but in many cases it is the wrong knot and often unsafe
pico23, i just tie the figure 8 as it is normally tied in any other application. Because of tublular webbing's flat shape, you have to neaten(not a word!! :? )the knot up. I do this by twisting the webbing around until the knot is nice and flat when loose, then I tighten it. I've never heard that applying the figure 8 when tying webbing is unsafe, and I wouldn't do it if it seemed that it wasn't the safest thing to do. As i think (?) I said in my first post, I think that tying the water know and then tying two strong safetys is stupid, so i'd rather use something that I can totally trust not to fail, even after repeated use and wear on the knot. Hope that helps.
If anyone reading this post is a mountain guide or the trained equivalent, don't hesitate to speak up. We can all stand to learn something :D
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slcliffdiver
Apr 14, 2003, 3:15 PM
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Please don't tie figure 8's in webbing this has been covered before. Webbing is slick. The reason people use the water knot in webbing is because it slips less than the figure 8. There are only two knotts that I've ever heard of being approved for nylon webbing the water knot and the double grape vine. The double grape vine isn't used much for trad slings because of it's bulk also with trad slings you're less likely to have cyclic loading so I don't worry about tight water knots with reasonable tails. For top roping or rapping I use the water knot backed up with double grape vine stoppers (unless I have super long tails) because it takes almost no time to put the back ups in and I don't want to have to worry about how many cycles it's going to take for it to slip through or for some reason my webbing ends up sliping faster than in the tests (pressure on rock who knows).
I'd like some real data for the beer knot it seems ideal but some real data would be cool. Maybe I can talk someone into doing some testing.
Someone mentioned tying spectra slings. If I recall correctly (big if) there is no good way to do it and preserve near full strength the water knot slips and the double grapevine cuts/melts? into itself. Some of the Spectra nylon hybrids supposedly work well with water knots. I think there is data for this in some of the tmyoer testing.
Peace
David
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petsfed
Apr 14, 2003, 3:50 PM
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I read this, but completely forgot about the master's thesis my climbing partner's dad did on this exact subject.
Here we are Its a PDF link so be adequately warned. The waterknot was found to be the strongest for 1 inch tubular webbing. Dave got all sorts of sponsorship for it too. Interesting stuff.
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mesomorf
Apr 14, 2003, 4:34 PM
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coldclimb wrote:In reply to: A variation that I have seen that supposedly eliminates slippage is using tubular webbing, tying the overhand, then threading one end through the other and moving the knot to the middle of the doubled section and tightening it. This seems logical to me, but I read it on this site, and I have no absolute confirmed proof, so correct me if I'm wrong.
It's called a beer knot.
A pain in the ass to tie, but I have never seen it slip over time. I don't bother with it anymore.
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