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diplodocus
Jan 5, 2004, 6:01 AM
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In a pinch, is it safe to use ONE single rope as a double rope (20 meter pitch)? ie.:
1) Climber makes a figure-8 on a bight in the middle of the rope, clips that into his harness
2) Belayer sets up both sides of the same rope as in double-rope belay
3) Climber leads up using double-rope technique
4) Belayer 2nds up with the 2 ends of the rope
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boltdude
Jan 5, 2004, 6:22 AM
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Sure, but it's safest to have the leader tie into the ends and the belayer use a couple lockers on a figure 8 on a bight in the middle of the rope.
In fact, some folks (especially mountaineers) use 100m skinny ropes and do this as a regular practice, since it's far safer on long rappels (you don't have to worry about the knot jamming on double-rope rappels if you don't have a knot).
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ropeburn
Jan 5, 2004, 6:42 AM
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It seems like you'd be in for a harsh "catch". Half the normal dynamic elongation.
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lukeskywalker
Jan 5, 2004, 7:25 AM
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There's no problem with using singles for double rope technique (one strand clipped to each biner), just don't do twin rope technique (both strands clipped to the same biner).. Ropeburn is kind of correct regarding the higher impact force, but only if you clip both strands into the same piece.
Also, you don't have to use lockers or other biners to clip into the middle of the rope.. You can tie in directly to the middle of a rope.. Just tie a big figure 8 on a bight, pass the bight trough the two loops on your harness and then pass the loop over your head and step trough.. If you've done this correctly you would have girth hitched the rope to your harness..
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coldclimb
Jan 5, 2004, 8:29 AM
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If you have effectively turned one rope into two, then you are no longer climbing on only one rope, and therefore it would be just as safe as two full length ropes. Right? ;)
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crushingfinger
Jan 5, 2004, 8:44 AM
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Look at the rope realy hard, somtimes it turns into two. :mrgreen:
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overlord
Jan 5, 2004, 1:02 PM
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its safe, but itll probably be a hrad catch unless you do a proper dynamic belay.
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j_ung
Jan 5, 2004, 2:15 PM
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Double, not twin, right? I don't think the catch will be any harder than the same fall on a single, since it's likely that only one of the two ropes will catch you anyway. Follow boltdude's suggestion to avoid crossloading a biner in a lead fall on a short rope, e.g., lead on the ends, not the middle.
j_ung
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geezergecko
Jan 5, 2004, 2:23 PM
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When you climb using proper double rope technique (as opposed to twin rope technique), a catch is almost always done on one and only one rope. Even if you use 2 carabiners on a piece to clip both ropes, the different length path of the ropes would insure one takes more strain than the other. The second rope is essentially a backup if the piece on the first rope pulls and then you fall on the piece for the second rope. This is good because you get 2 shots at a soft catch. Think of this as a series system not a parallel system.
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diplodocus
Jan 5, 2004, 2:32 PM
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To be clear, it would not be a ‘hard’ catch if I use the “double rope technique” and NOT the “twin rope technique” right? If not, could someone please explain to me why it would be a hard catch.
I get the impression from some of the comments that it would be a hard catch whichever the method.
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esoteric1
Jan 5, 2004, 2:35 PM
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yall ever seen those really long thin chords? ive seen some euros climbing on one of those...120 meeter single line and they double it over, at like 8.5 or something like that, pretty keen idea if ya ask me...
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j_ung
Jan 5, 2004, 9:32 PM
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In reply to: To be clear, it would not be a hard catch if I use the double rope technique and NOT the twin rope technique right? If not, could someone please explain to me why it would be a hard catch. I get the impression from some of the comments that it would be a hard catch whichever the method.
Welllll, sort of.
The more rope length you have in the system, the more stretch you get during a fall, thus a softer catch. Working with only half the rope's total length, as you suggest, means that you'll never get to have more than half the rope in your system. However, the difference isn't going to kill you (unless your protection really sucks).
Some folks, myself included, have cautioned against twin roping (clipping both ropes into every piece) because 2 ropes won't stretch nearly as much as one - that may mean a hard catch, depending on your rope diameter. Instead, most of us seem to think it's OK to use doubles (clipping separate pieces to minimize drag (and a few other reasons)).
Twins = bad
Doubles = AOK
You may, however, encounter other safety concerns. Has your partner belayed on doubles before? It's much trickier. Also how long is the route in total? I ask because with half the rope length, you may have to climb twice as many pitches :( .
But a better question is this: What exactly is the "pinch" that you spoke of in your original post?
Common reasons why people climb on doubles (in no particular order):
1. Minimizes rope drag
2. No extra rope to carry solely for rappelling later
3. No extra slack in the system if you blow a clip
4. Minimizes risk of your only rope being cut in a fall or by rockfall
Is your reason one of those?
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hema
Jan 5, 2004, 10:11 PM
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In reply to: In reply to: yall ever seen those really long thin chords? ive seen some euros climbing on one of those...120 meeter single line and they double it over, at like 8.5 or something like that, pretty keen idea if ya ask me... Cool idea. No knot to get stuck on rappel! :D Can you get it in bi-color so you can still which side is which?
Yeah, you do get them in bi-colors. I got myself 100m bo-colored half-rope and atleast Mammut and Millet(Onesport) do them.
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tedc
Jan 5, 2004, 10:22 PM
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8.5mm x 100m: Cool idea until you find out how tangled you can get it. A 100m line is about 10 times more tangle prone than a 50m and you HAVE to have it flaked perfectly on every pitch or the belayer will end up fighting a knot for half the pitch. The knot is a small price to pay for the flexibility of two ropes. IMHO. BTW the same thing hapens when you double over a 50m. It just takes half as much time to clear the cluster F.
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davidji
Jan 5, 2004, 11:13 PM
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In reply to: There's no problem with using singles for double rope technique (one strand clipped to each biner), just don't do twin rope technique (both strands clipped to the same biner).. Ropeburn is kind of correct regarding the higher impact force, but only if you clip both strands into the same piece.
Why not use one half rope instead of one single? That's how I've done it anyway.
David
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climbaddic
Jan 5, 2004, 11:34 PM
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THIS IS REALLY DANGEROUS.
If you are taking a fall, your Fall Force on the anchor will be too big. You will blow out your anchors from big fall force. Sure you have less chance of cutting your ropes, but your chance goes way up for blowing out anchors.
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diplodocus
Jan 6, 2004, 2:54 AM
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To answer "j_ung"'s question ...
By "pinch", I mean if I come to a new pitch that is about 20-25meters, and because its a winding route and looks safer to use a double rope technique. (but I only have one 30 meter rope with me).
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rgold
Jan 6, 2004, 3:02 PM
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The "hard catch" resulting from clipping both strands can be quantified; the sum of the tensions in both ropes will be the square root of 2 times the tension that would have resulted had only a single strand caught the fall. Since the square root of 2 is approximately 1.4, clipping both strands will result in loads to the system that are 40% higher than the loads imposed by a single strand.
If you've redirected the belay through the belay anchor and the leader falls with the anchor at his feet (fall factor 1), the load on the anchor with both ropes clipped and a static belay would be a bit more than 16 kN or nearly 3700 lbf. (The only way to achieve this would be to belay with two Gri-Gri's.) In order to belay statically, the belayer would have to hold nearly 1500 lbf; of course this is impossible(*) and so the belay will be of the forced dynamic kind. Rope burns are guaranteed (assuming no gloves) and loss of control is quite possible.
Of course, rope burns and possible loss of control are features of the single clip-in too. In the same situation with just one rope clipped to the belay anchor, the load on the anchor for a static belay would be about 12 kN or 2600 lbf and the belayer would be faced with a static load a bit over 1000 lbf.
In any case, as has been said several times already, there is no reason to risk 40% greater loads by clipping both strands when each strand is already a single rope.
(*)Footnote: Maybe it isn't impossible, which is worrisome. I suspect that a belayer can momentarily resist much higher loads than the figures we read for belay devices, which are static holding loads. In other words, rope tension and anchor loads might momentarily build much higher than the figures that result from the static load a belayer can hold.
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esoteric1
Jan 6, 2004, 3:19 PM
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I sure am glad that someone does the math on these things.
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reno
Jan 6, 2004, 3:20 PM
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Why couldn't you take the middle of the rope, tie in with a bowline, and leave the ends for the belayer (akin to the middle person on a three man glacier/snow climb)?? This seems more simple than the "Step through-Girth Hitch" method mentioned on page 1.
Never done either, as I climb on a single 10.5 or doubles.
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j_ung
Jan 6, 2004, 4:26 PM
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In reply to: To answer "j_ung"'s question ... By "pinch", I mean if I come to a new pitch that is about 20-25meters, and because its a winding route and looks safer to use a double rope technique. (but I only have one 30 meter rope with me).
I'm assuming you mean that you have one 60 meter rope with you, correct? In that case you're fine, just be sure to listen to the advice in the thread about impact forces on doubles vs. twin. Seems like a no-brainer, but if a mistake is going to occur, it'll likely be low on the pitch. This is because without much gear placed, you're virtually on twins, not doubles, no matter what you do. Place lots of gear early. You should be doing that anyway!
Have fun, man! Figuring out problems like this one is what got me interested in climbing in the first place!
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diplodocus
Jan 10, 2004, 2:31 PM
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opps, yes i meant 60m rope. Tks for the input folks
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diplodocus
Feb 5, 2004, 4:01 PM
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Several people said that it was better to lead using both ends of the rope rather than the middle … is there a reason why it is better?
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scubasnyder
Feb 5, 2004, 4:03 PM
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its safe.......
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