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silkyerm
Nov 28, 2005, 8:25 PM
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Maybe, maybe not, but the website you listed is a sailing website, not a climbing site so it has no relevance to my life and death decisions in climbing.
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qtm
Nov 28, 2005, 8:54 PM
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In reply to: In reply to: One of the best knots in GENERAL to join differing diam. ropes is the sheet bend, which is really a version of the bowline. Especially if you tie it with 2-3 turns on the smaller rope (analogous to the two bends in the mountaineering bowline). No comment on how well/poorly it performs concerning jamming when pulling ropes. I would say that it is more symmetrical than asymmetric. At least someone knows what their talking about. A sheet bend (with backup hitchs) is the best method for different diameter ropes. http://www.tollesburysc.co.uk/Knots/Sheet_bend.htm
Not according to two well quoted books on knots.
"The Ashley Book of Knots" lists the overhand (EDK) as more secure than the sheet bend. The double sheet bend came apart in only 36 pulls.
Budworth's "The Complete Book of Knots" says about the Sheet Bend: "Security tests have shown it to spill after an average 22 tugs out of 100, and it is not a very strong knot, with a breaking strength of 55%."
Maybe it's a "better" knot. The Double Fisherman is is certainly the *best* knot as far as knots go. However, for rapping, I prefer the EDK.
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jv
Nov 28, 2005, 9:34 PM
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No reputable climbing information source has ever, to my knowledge, advocated using a sheet bend for any rock climbing application. I am certain I have seen sources warning that it should not be used for rapelling. Please prove me wrong.
A sheet bend is inferior to the DF because the knot has a tendency to loosen. Even without tied tails, a DF is a secure knot, not that anyone in his right mind would ever omit tying the tails. But a sheet bend without tails tied practically unties itself.
Furthermore, because a sheet bend is not asymmetric, it has the same proclivity for jamming as the more secure and highly-recommended DF. So there is no earthly reason to use a sheet bend instead of a DF. But there are two good reasons to use and EDK instead of a DF. See above.
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knudenoggin
Nov 30, 2005, 7:28 AM
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In reply to: No reputable climbing information source has ever, to my knowledge, advocated using a sheet bend ...
--just as the Square/Reef (& Thief) knots have been recommended (e.g.,
cf. Duane Raleigh's Knots & Ropes for Climbers, and Clyde Soles's
book previously cited (though Clyde goofed on the image and shows a Thief
vice Reef knot).
In reply to: Even without tied tails, a DF is a secure knot, not that anyone in his right mind would ever omit tying the tails. Furthermore, because a sheet bend is not asymmetric, it has the same proclivity for jamming as the more secure and highly-recommended DF. So there is no earthly reason to use a sheet bend instead of a DF
If more security is needed (e.g., for tying off an HMPE sling), the TF is used.
The Sheet bend IS Asymmetric, but that jamming is a non sequitur re that.
In fact, the SB doesn't jam or become as tight at rap. forces as the DF/G,
and that's why it has been used or suggested (w/safety knots). Given that
the OOB has more good qualities, both the DF & SB can be put aside.
In reply to: Not according to two well quoted books on knots. "The Ashley Book of Knots" lists the overhand (EDK) as more secure than the sheet bend. The double sheet bend came apart in only 36 pulls. Budworth's "The Complete Book of Knots" says about the Sheet Bend: "Security tests have shown it to spill after an average 22 tugs out of 100, and it is not a very strong knot, with a breaking strength of 55%."
other books--so citing some number could be just counting echoes.
In the case you mention, Budworth's "22" matches Ashley's table of ONE testing
he did: coincidence? --no. (And writing "tests" exagerates the fact, geesh.)
Hey, try it yourself and see what happens after 22 or 30 or ... jerks on it.
And, btw, Ashley was testing mohair fibers for a fabric maker (car upholstery):
do you want to transfer his results to 10mm nylon kernmantle rope? Similarly,
the oft'-quoted strength figures come from some testing whose conditions are never
fully stated. Hard to replicate that, for the scientific method, etc.. But you're not
concerned w/strength when rapping, just keeping the knot tied--even as it might rub
against rock.
*knudeNoggin*
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devonick
Nov 30, 2005, 7:47 AM
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after getting involved with search and rescue i managed to get hold of some test results and they came to the conclusion that around 50% (dont have exact numbers with me) stayed as they were but the other half rolled and came undone. if you do use the EDK then tie it with enough tail and also tie it properly, whenthey tested a EDK that was tied and sloppy it rolled at only 300lb
just something to think about, i will continue to use the DF over the EDK though
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kricir
Nov 30, 2005, 7:58 AM
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I use a 6 mill rap line, and use a retrace 8, because it is slim, and usually easy to untie. Iv been doing this for 6 years, and so far so good.
I must say, NEVER, use a 8 (rap device), or an army style biner wrap to rappel on different diameters, your ropes will become an impossible tangle. I learned this the hard way, hanging off the N face of longs peak for 3 hours in winter (I was 13) wile my dad untangled the ropes.
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azrockclimber
Nov 30, 2005, 12:48 PM
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I have joined different diameter ropes many times. However, I can't say that I have ever joined diameters as far apart as 10.5 and 7mm....I usually don't like to mess with anything over a 2mm spread. Personally, I wouldn't use anything less than 7mm
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climbrox391
Nov 30, 2005, 1:22 PM
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I could be wrong, but I don't think an EDK would be the best choice for joining ropes of unequal diameter. It is the preferrable knot for joining ropes of equal diameter, but I would think the DF would be much more sound for two different sizes. Just my .02
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pendereki
Nov 30, 2005, 2:12 PM
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It seems that in all discussions of rappel knots, I read that the EDK has contributed to accidents by coming undone. I have not heard of a double fishermans ever untying under body weight. I am sticking with the 100% track record for now. I can fix a stuck rope, I can not fix a rap knot that has come untied during a rappel.
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csproul
Nov 30, 2005, 2:47 PM
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In reply to: Posted: Wed Nov 30, 2005 6:12 am Post subject: Re: Joining Different Diameter Cord -------------------------------------------------------------------------------- It seems that in all discussions of rappel knots, I read that the EDK has contributed to accidents by coming undone. I have not heard of a double fishermans ever untying under body weight. I am sticking with the 100% track record for now. I can fix a stuck rope, I can not fix a rap knot that has come untied during a rappel. |
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roy_hinkley_jr
Nov 30, 2005, 4:28 PM
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In reply to: I could be wrong, but I don't think an EDK would be the best choice for joining ropes of unequal diameter. It is the preferrable knot for joining ropes of equal diameter, but I would think the DF would be much more sound for two different sizes. Just my .02
You are wrong -- at least for rappel applications. The OOB (EDK) is a superb knot for joining a single rope and tag line or half rope.
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qtm
Nov 30, 2005, 5:41 PM
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The retraced figure 8 (not an inline figure 8 with both tails on one side of the knot) has been reported to be stronger than the double fisherman and have less rope slippage. However, with it's symmetric profile, it has the same drawbacks as the DF when getting caught up in things.
Here's a great discussion of various knots, slippage, and pull tests by a canyoneering club at Sydney University.
http://www.bwrs.org.au/research/index.html
Yet another group who deterimined that while the EDK is not as strong as the DF (or retraced figure 8), the reduced risks of getting the knot caught while pulling make it a better knot to use.
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redpoint73
Nov 30, 2005, 5:58 PM
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I remember reading a first-person accident report in on of the mags LONG ago (several years). The author used 2 different diameter ropes for a rappel. Since the larger diameter rope was engaging his tube device more than the skinny rope, the fatter rope was pulled downward, and the skinny rope actually pulled upward (so the knot actually moved down away from the anchor).
He didn't realize this was happening, and eventually ended up rapping off the end of the skinny rope. He took a tumble, but walked away from it.
His advice was to take care when rapping with vastly different diameter ropes, and arrange the knot so that it blocks up against the anchor (knot on the skinny rope side). He also suggested tying the ends together, as not to rap off the end -- but thats a different debate.
Now, I don't use different sized ropes to rappel ever. So I am simply just paraphrasing an article that I read long ago. It seems that many users here use different diameter ropes on a regular basis. Can any of you comment on this issue? Ever experienced or heard of anything like this before?
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qtm
Nov 30, 2005, 6:36 PM
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I don't like the knot pressed up against the rap ring. It's been said that it's better to pull the lead line and let the skinny static line fall, because that way you'll still have your lead line in hand if the skinny static gets tangled up and you have to climb up to free it; better to lead up on your lead line than lead on a static line to free your lead rope.
There was a report not too long ago about someone who rapped off the end of a rope just 10M below the rings, apparently the rope wasn't fed evenly through the rap rings. You always have to be on the lookout for the end of the ends of the rope. If you can't put knots in the end of the rope, then you better be very careful about where the knots are, and to use a backup above the device.
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joshy8200
Nov 30, 2005, 6:39 PM
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In reply to: I remember reading a first-person accident report in on of the mags LONG ago (several years). The author used 2 different diameter ropes for a rappel. Since the larger diameter rope was engaging his tube device more than the skinny rope, the fatter rope was pulled downward, and the skinny rope actually pulled upward (so the knot actually moved down away from the anchor). Can any of you comment on this issue? Ever experienced or heard of anything like this before?
Yes have heard of it and was warned about it when I borrowed a 7mm rap line from a friend. The description of the 'large diameter rope engaging the rap device more than the skinny rope' is an excellent way to explain what happens in this situation. The small diameter rope is easily running through the belay device while the larger rope is actually 'engaging' it and giving you friction. So you're weighting and pulling on the larger diameter rope much less than the small diamter.
And right-on about remedying the situation by setting the knot so that you PULL THE SMALL-DIAMETER ROPE after rapping.
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bostonclimbah
Nov 30, 2005, 6:50 PM
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In reply to: Now, I don't use different sized ropes to rappel ever. So I am simply just paraphrasing an article that I read long ago. It seems that many users here use different diameter ropes on a regular basis. Can any of you comment on this issue? Ever experienced or heard of anything like this before?
I've used different diameters on many occassions (actually, most of the time for some reason) ranging from 7.X, 10.5 to 9.8, 10.5. In all cases, I've used the flat overhand (EDK if you must). While it's true that there will be some migration, it is not due entirely to the difference in diameter. It's really due to the difference in elongation. So, what I'm saying is that it can happen on 2 cords very clsoe in size but perhaps 1 is very old and the other brand new with very high elongation to begin with. The rope with the higher elongation will move slower through the device, thereby causing the other end to come up short. Not a big deal if you see it coming as you can begin correcting it long before it's a problem.
So, as far as migration of the knot or however you wan tto refer to it, the botom line is that you always have to be mindful of what the rope is doing behind / below you. Knotting the ends of the rope (as you already know - it seems) is not always the answer and can lead to more trouble. Being from NE yourself, I assume you have spent time on Whitehorse and know exectly what I mean.
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joshy8200
Nov 30, 2005, 6:55 PM
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In reply to: I don't like the knot pressed up against the rap ring.
Why's that?
In reply to: It's been said that it's better to pull the lead line and let the skinny static line fall, because that way you'll still have your lead line in hand if the skinny static gets tangled up and you have to climb up to free it; better to lead up on your lead line than lead on a static line to free your lead rope.
I have only on 1 occasion used two different diameters to rap...and never even thought about this. This is a good point.
The quote about the 'larger diameter rope engaging the belay device more than the smaller chord' is a very good description of what occurs to cause the larger diameter rope to be pulled un-evenly.
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qtm
Nov 30, 2005, 9:01 PM
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In reply to: In reply to: I don't like the knot pressed up against the rap ring. Why's that?
The overhand knot (EDK) is a small knot. I don't want it to get wedged or passed through the ring; if it does then it's prussicking all the way back to the anchor to dislodge it.
Second, with the overhand knot, the ring is pushing against the outside of the knot, or working as a wedge on the "inside"... which could induce the knot to roll or loosen. I don't know if anyone has actually tested this, but it seems possible.
Third, if you tie the knot with 12" of tail, then the knot is always in the same place, and if you put the rope agains the rings, then the rope is bent at the same place every rap. I move the knot at different lengths away from the rings to prevent rapping off the same part of the rope every time.
Lastly, sometimes you have to rap over an edge. I pull the knot with me (letting the rope run through the rap rings) until both me and the knot are over the edge. That way when I pull the rope, I don't have to pull the knot over the edge.
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knudenoggin
Dec 2, 2005, 12:19 AM
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In reply to: It seems that in all discussions of rappel knots, I read that the EDK has contributed to accidents by coming undone. I have not heard of a double fishermans ever untying under body weight. I am sticking with the 100% track record for now.
has been at least one (Zion, Brit. climbers) re the Offset FIG.8 Bend, and a few
test reports citing it as prone to capsizing. And the situation with that one report
for the OOB was speculative.
But please bring any citations re the Offset OVERHAND Bend to light.
The UIAA and some rope vendors recommend this knot, and it is much used.
*knudeNoggin*
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handtraverse
Dec 3, 2005, 12:53 AM
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devonick wrote
In reply to: after getting involved with search and rescue i managed to get hold of some test results and they came to the conclusion that around 50% (dont have exact numbers with me) stayed as they were but the other half rolled and came undone. if you do use the EDK then tie it with enough tail and also tie it properly, whenthey tested a EDK that was tied and sloppy it rolled at only 300lb just something to think about, i will continue to use the DF over the EDK though
Now here's a man who knows what he's talking about.
And I agree with the DF, especially since my very life depends on a dependable knot. I would NEVER use a knot that offers convenience in one area but threat in another. I will reiterate, "why then is there a need for a long tail" with the EDK?...Just for a precautionary measure? To me that's just not good sense. I normally use a TF.
Personally, I don't care about asymmetry or symmetry.:roll: ....although it did sound impressive, but I couldn't figure out what the heck he was trying to say...oh well. :D
Handtraverse
__________________________________________
"Mountains are not fair or unfair - they're just dangerous" - Reinhold Messner
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codhands
Dec 3, 2005, 1:36 AM
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I am not advocating it's use for climbing or joining to different diameter ropes together but I would like to see someone do some testing on the use of a carrick bend, I love that knot. (I have never used this knot for climbing, but it kicks butt for crab fishing.)
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codhands
Dec 7, 2005, 8:16 PM
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In reply to: I am not advocating it's use for climbing or joining to different diameter ropes together but I would like to see someone do some testing on the use of a carrick bend, I love that knot. (I have never used this knot for climbing, but it kicks butt for crab fishing.)
A little follow up-
I did some of my own testing last night. Doesn't look like a carrick bend is a good choice for 10.1 dynamic rope. But I still love the hell outa that knot.
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bostonclimbah
Dec 7, 2005, 8:50 PM
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In reply to: devonick wrote In reply to: after getting involved with search and rescue i managed to get hold of some test results and they came to the conclusion that around 50% (dont have exact numbers with me) stayed as they were but the other half rolled and came undone. if you do use the EDK then tie it with enough tail and also tie it properly, whenthey tested a EDK that was tied and sloppy it rolled at only 300lb just something to think about, i will continue to use the DF over the EDK though Now here's a man who knows what he's talking about. And I agree with the DF, especially since my very life depends on a dependable knot. I would NEVER use a knot that offers convenience in one area but threat in another. I will reiterate, "why then is there a need for a long tail" with the EDK?...Just for a precautionary measure? To me that's just not good sense. I normally use a TF. Personally, I don't care about asymmetry or symmetry.:roll: ....although it did sound impressive, but I couldn't figure out what the heck he was trying to say...oh well. :D Handtraverse __________________________________________ "Mountains are not fair or unfair - they're just dangerous" - Reinhold Messner
Please don't take this as a flame. However, both of you are needlessly perpetuating a heinous myth based on erroneous and inconclusive data. HT, you're closing comment on Symetry is dangerously misinformed and screams "inexperienced".
Again, I am not trying to be a jerk but this is bad info. The Flat Overhand is widely accepted and with VERY GOOD reason. All of which has beaten to death here and in countless other threads.
A knot has to do a lot more than keep the two ropes together.
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maldaly
Dec 7, 2005, 9:09 PM
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For a while I used a 7mm and a single rope (Probably 10.2 or 10.5mm) as my alpine rig or whenever I wanted full length rap capacity. To put it kindly, the only time I liked this set up was when that damn 7mm was in my pack. It absolutely sucked and each time I went to throw it or pull it I swore I'd never carry that setup again. Ever tried tossing a 7mm rope in a brisk alpine wind? The 7mm was forever getting tangled up, it was desperate to pull (You are running the larger rope through the anchors aren't you?) and I have nightmares about climbing back up to pull that skinny rope out from behind flakes or off of rubble strewn ledges. Much better is to carry an 8.4 twin. It's only slightly heavier and bulkier but it acts like a real rope just when you need it. BTW, since I came from a sailing background I always used a doubled sheet bend to tie the 7 to the single. For it to be secure you must make sure that the standing bight is formed from the larger diameter rope. I did that before I knew abouot the EKD. I'd use that now.
Mal
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knudenoggin
Dec 7, 2005, 9:18 PM
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In reply to: I will reiterate, "why then is there a need for a long tail" with the EDK?...Just for a precautionary measure? To me that's just not good sense. I normally use a TF.
usage is out there with safe results. There should be no problem, no "rolling", if one
ties/dresses/sets the knot correctly. And, esp. with minor modification I earlier
suggested, no problem. Again, it's not so much for convenience of tying, but limiting
risk of being stuck and of surer/smoother movement over rough surfaces,
that are desired qualities of the OOB.
In reply to: Personally, I don't care about asymmetry or symmetry. ....although it did sound impressive, but I couldn't figure out what the heck he was trying to say...oh well.
path than the other (parallel, yes, but ...), there is a chance that the knot is MORE
suitable to unequal ropes. The Sheet Bend is also and more obviously asymmetric,
and so it is recommended for unequal sizes with advice to form the "U" part (the bight)
with the thicker or stiffer rope, and the "loop" part with the other. The DF/Grapevine
though symmetric has each rope's involvement isolated and therefore also works
pretty well in unequal ropes. And for the OOB (EDK), it is recommended to take
advantage of the asymmetry by positioning the thinner rope so that it
would be first forced to roll over the thicker (and not vice versa, which would make
the rolling easier).
In reply to: I am not advocating it's use for climbing or joining to different diameter ropes together but I would like to see someone do some testing on the use of a carrick bend, I love that knot. (I have never used this knot for climbing, but it kicks butt for crab fishing.)
when slack. If it's tied in the lattice-form (method) with the loaded ends being
not opposite each other, it can slip; tied another way, where one rope's half is formed
and then the other brought into it, one must choose between four versions. A knot known as "Ashley's Bend" (his #1452) can be seen as a sort
of derivative of the Carrick (similar in nice priable-to-untie collars) and is
somewhat less "open"; his #1425 is arguably much surer, more secure (when slack),
suitable for the ropes mis-match of issue here, but still not so free-flowing as the
OOB (nor as easily tied!). --still, interlocking Overhand knots.
For that stiff rope used in Alaskan crabbing, I'd suggest that Rosendahl's bend
(aka "Zeppelin") be tried. It might even run through the pot hauler with less
disturbance? --has a great broad face/aspect for running along deck.
Cheers,
*knudeNoggin*
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