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AntinJ
Feb 2, 2009, 6:37 AM
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Yes, I realize this issue has been touched upon a few times, but I was hoping for an answer more specifically related to cordelettes-
I have been climbing for a little over six months now and have heard conflicting advice regarding this issue. I carry 2 Sterling 7mm x 21-Foot Cordelettes for building anchors. I connect the cordelette using a double fisherman. Is it a bad idea to leave this knot in the cord' for an extended period of time?
Same question for 6mm prussik loops?
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salamanizer
Feb 2, 2009, 7:04 AM
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No!
Why would it be?
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tradrenn
Feb 2, 2009, 9:15 AM
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No!
Why would it be?
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AntinJ
Feb 2, 2009, 10:04 AM
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I heard it can weaken the rope...
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patto
Feb 2, 2009, 10:13 AM
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What is the alternative?
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mikebee
Feb 2, 2009, 10:20 AM
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All knots will weaken the rope to some degree.
Generally, the tighter the radius of the knot, the greater the decrease in strength.
That said, there is so much over-engineering in the strength of cord and ropes these days that it's not an issue to worry about.
Leaving the knots in nylon rope shouldn't have any issues long term at all.
I've read in the past (can't remember where) that repeated knotting in the same section of Spectra cord can result is a significant reduction of the strength of that cord. But,again, the strength of 5.5mm spectra cord is high enough that the reduction still means the cord is way more than strong enough for most climbing applications.
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AntinJ
Feb 2, 2009, 10:25 AM
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patto wrote: What is the alternative?
Untying after every trip vs. Leaving the knot in for a while
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johnwesely
Feb 2, 2009, 12:54 PM
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AntinJ wrote: patto wrote: What is the alternative? Untying after every trip vs. Leaving the knot in for a while
I will leave my knot in and not take the risk of having to do anything extra to prepare for a climbing trip.
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billl7
Feb 2, 2009, 1:55 PM
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As for a knot weakening software, maybe someone will post various reductions in strength. Seems like with nylon 40% might be a good conservative rule of thumb but I have not checked the literature laterly. It may be worthwhile for you to look up the expected reduction for the double fishermans and factor that into the overall strength when your anchor rig is fully configured. Then decide how much of a concern it is to you.
Also, perhaps not what you were thinking but ...
I have noticed some extra wear on the exposed parts of the knot. Besides what your anchor rig has, the equalette adds a couple more knots that generally stay tied. Also consider the time-honored tied sling: semi-permanent loop of webbing tied with, say, a double fishermans. I have seen all of these knots exhibit that extra wear due to contact with the rock.
One can sometimes make minor adjustments to avoid the knots rubbing on rock (e.g., move the knot out of contact with the rock by rotating the loop). And if I leave slings at a rap anchor, I'll choose the most worn-looking sling(s) - I would not have brought it on the climb if it were not adequate. Once in a great while there will be some reason to untie the knots for an unrelated reason; at those times I'll re-tie the knots in a different location if I can (not very practical for short slings).
Is the "extra" wear of software dangerous? It can be - consider Todd Skinner's belay loop. However, I would say generally not. Virtually all leaders know to keep an eye on their software including the age of varous pieces. And these things don't usually wear to the breaking point in one outing (watch those sharp edges!). This (the 'extra' wear issue) is just another reason to keep up with periodic inspections and retire things before there is much of a question about integrity.
Bill L
(This post was edited by billl7 on Feb 2, 2009, 1:58 PM)
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Tree_wrangler
Feb 2, 2009, 2:35 PM
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If you use it for a long time, you'll see dirt accumulating in the "crevices" of the knot, which would cause the same concerns as working particulates deep into the core of your rope.....
But, I rapped off some "fixed" cordelette that had been out in the elements since last summer....it looked flawless, and was still pliable....
so, if it worries you, buy a new piece of cordelette once a year or whenever.
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trenchdigger
Feb 2, 2009, 3:05 PM
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Much more so with spectra/kevlar core cords, repeated tying and untying will, over time, weaken the cord. With Nylon cord, I wouldn't consider it significant enough to ever be an issue. The only safety related reason I can think of to untie a cordelette is if the knot shows signs of abarasion and you want to either remove those abraded areas or move them away from the knot where they won't keep getting abused.
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umeroz7
Feb 2, 2009, 3:15 PM
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if the cord is thin and you never retie the knot eventually the core will slip out of the knot. this takes a long time but i have seen and old cord with a knot in it that was just sheath the core of the cord had retraced itself through the knot. but like i said this takes a long long time so im sure your fine
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salamanizer
Feb 2, 2009, 3:44 PM
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umeroz7 wrote: if the cord is thin and you never retie the knot eventually the core will slip out of the knot. this takes a long time but i have seen and old cord with a knot in it that was just sheath the core of the cord had retraced itself through the knot. but like i said this takes a long long time so im sure your fine
I call bullshit.
You misunderstood what you saw.
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Gmburns2000
Feb 2, 2009, 3:59 PM
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I leave mine tied for both cordellete and webbing, though I tend to use webbing more for TR and need to adjust that more often.
I do, however, adjust where my harness loops through the buckles on a fairly regular basis so that the same piece of webbing isn't always cinched in the same spot.
I'd do whatever you feel comfortable with. It seems fine to leave the knot in to me.
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dynosore
Feb 2, 2009, 4:45 PM
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AntinJ wrote: Yes, I realize this issue has been touched upon a few times, but I was hoping for an answer more specifically related to cordelettes- I have been climbing for a little over six months now and have heard conflicting advice regarding this issue. I carry 2 Sterling 7mm x 21-Foot Cordelettes for building anchors. I connect the cordelette using a double fisherman. Is it a bad idea to leave this knot in the cord' for an extended period of time? Same question for 6mm prussik loops?
Your cordlette will weaken according to the following formula:
# of days knot has been tied/(sqrt of average troll posting per day)*e^1.72
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coastal_climber
Feb 2, 2009, 5:31 PM
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Dude, how cheap is cordalette? Just get some new stuff.
Next.
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jeepnphreak
Feb 2, 2009, 8:54 PM
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coastal_climber wrote: Dude, how cheap is cordalette? Just get some new stuff. Next.
thank you someone beat me to it.
I buy new cord every season, and leave the knott in the whole time, there no point in tieing and retieing the cord over and over.
Its cheap, toss to old crap and get new cord if in doubt. there no reason to risk you lift over $10 woth of cord.
(This post was edited by jeepnphreak on Feb 2, 2009, 8:56 PM)
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Adk
Feb 2, 2009, 9:12 PM
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Though it is cheap I don't think you need to worry so much. Worry about your shoe laces more.
Honestly. How many climbers use the same cordelette
year in and year out?
Bill is right here. Knots are going to take some abuse from abrasion and that is something to consider but if it's just sitting in your pack?
Use nylon if you are going to use the tie and untie method. As was said above, dynema doesn't take so well to all that hard flexing.
If you are nervous replace it every year. I would assess it this way; How much you climb and use it? Give it a couple years unless you are beating it and fibers are fraying. JMHO
(This post was edited by Adk on Feb 2, 2009, 9:13 PM)
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wanderlustmd
Feb 2, 2009, 10:58 PM
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Yes you will die. Stop climbing immediately.
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time2clmb
Feb 3, 2009, 12:16 AM
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A knot is a weak point. Even if you untie it after you are done for the day, you still have to retie it to use it again thus recreating that weak point. Use the proper knots with the material you are working with and you will be fine in that regard.
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d0nk3yk0n9
Feb 3, 2009, 12:27 AM
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Here's the rule of thumb I've heard regarding leaving knots in anything (rope, webbing, cordelette, prusiks, anything):
you can leave a knot in it for as long as you want without weakening the rope (further than the knot already does), however, if you unknot a rope after leaving it tied tightly for long periods of time (in excess of several days), then the rope is weakened at the spot where the knot used to be. Therefore, if you tie permanent knots, they should be just that: permanent. Don't untie them, even to retie the same knot, or else you risk weakening your rope further.
Most of this information is taken from Life on a Line pages 28-29. Life on a Line is essentially a handbook for how to rig and run vertical rescue operations.
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chossmonkey
Feb 3, 2009, 1:12 AM
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rocknice2
Feb 3, 2009, 3:38 AM
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I know that knot weaken a cord but they always break just below the knot never at it.
Same thing for swaged cable. Always just below the swage.
Cords were snapped pulling stumps with 4x4
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d0nk3yk0n9
Feb 3, 2009, 3:56 AM
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Again, to reiterate and simplify what I said above:
Leaving tightly tied knots in permanently is okay.
Leaving loosely tied knots in for long periods of time, and tightening them or untying them is okay.
Leaving tightly tied knots in for a long time and then untying them is probably a bad idea.
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acorneau
Feb 3, 2009, 4:15 PM
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d0nk3yk0n9 wrote: you can leave a knot in it for as long as you want without weakening the rope (further than the knot already does), however, if you unknot a rope after leaving it tied tightly for long periods of time (in excess of several days), then the rope is weakened at the spot where the knot used to be.
I can say that I agree with this logic.
According to the paper Comparative Testing of High Strength Cord by Tom Moyer, (http://www.xmission.com/...gh_Strength_Cord.pdf) nylon cord has an amazing resiliency to flexing, so I can't see why it wouldn't retain it's strength after a long-term knot has been untied.
From the paper:
In reply to: Last, Nylon cord and webbing may be the best of all. Although heavier, they are cheap, strong, universally available, and seem to have a virtually unlimited flex life.
Perhaps you can site some testing to this effect?
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