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Ross

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  1. >good info Ross and Matt and Cpt. although Ross might have shared it a bit differently... Talk about spray... Tons of people, including me, thought this about doubles: if you use them as doubles -- clipping even just the most recent two pieces alternately -- the second rope will share the load from a fall. That's not true, except for falls past the anchor. Try it on paper or with a gumby doll and string or whatever. The backup rope would face exactly the same force or more as the first -- it doesn't "share" the load at all. So I wanted to know how they could get away with being thinner when they're facing the same falls as singles. Sure, it's good to have a backup. Sure, most rope failures come from being cut. That matters to us as climbers, and so do techniques that reduce drag and weight, but what I'm asking about is diameter and strength standards for singles vs halfs. The UIAA has an edge test, and while there's demand for it to be more popular, it isn't used in certification yet. Even the Edelweiss ropes mentioned above get their excellent cut resistance from superior fibers, not sheer thickness. The question is, why is there a different standard in strength alone if they don't share the load from a fall? They really don't, when used as doubles, except in falls below the anchor. The UIAA test was mysterious, too, using a factor 1.78 fall with only 55 kg. Did you know before this thread that a double CAN'T face that factor 1.78 fall, ever? I didn't. They're really simulating a factor 1.2 with 80Kg. Now I see why: doubles -- used as doubles and clipped alternately even just twice in a row-- take the load alone for all falls except those below the anchor, which they share. Other people posted info that, while true and obvious, totally missed the question ("thinner ropes weigh less", "thicker ropes are more durable", "half ropes reduce drag"), and while trying to understand how doubles are actually designed to work, I get called an "idiot," and "comprehension challenged." I guess it's true: I came to the Boards for help with a climbing question. Ross
  2. Matt, >"If you lead on double ropes, and place a piece of gear every fifteen feet, alternating clips, without regard for where the crux climbing lies, you are not properly using double rope technique in my opinion. " I was using the classic example from my first post, of stemming up two cracks and clipping alternately to reduce drag. Since it's such a good time for double-rope technique, it's often used for illustration. Col, >"That's what people have been saying, just not in idiot terms." Actually, people have been saying all kinds of things ("Here's the UIAA test info," "you save weight with thinner ropes") that didn't address the question. I really wanted to know what about double-rope technique justified a difference in the rope design, and it isn't obvious. >"BTW: Why did you ask a question and than argue with every person that gave you and answer" I didn't know the answer when I posted, and I argued with "answers" that said things like "double-rope technique reduces rope drag." Much of what people posted is true without getting at the question. Unlike you, I didn't belittle anyone who posted -- just tried restating my question to make it clear and avoid mis-answers. While working out examples, I discovered that you CAN'T get a factor 2 fall on one half rope. Weird, huh? Unlike for singles, the UIAA test for doubles exceeds the max possible force on a rope. I never knew that, never read it, and never understood why. At least now we have one theory for what makes half ropes different: the second one CANNOT face the factor 1.78 fall used in the test -- not even close. Have you seen that posted anywhere before? >"are just an argumentative prick." And thanks for your contributions here. Ross
  3. >obvious enough for those posting and those simply reading. I'll take that, and I'll also give a possible answer to the question ignored. The previous answers miss the mark -- maybe my fault for not asking clearly, maybe theirs for assuming without checking. Here are the standard answers (Question: why can half ropes be smaller than singles?) and what's missing: - half ropes are redundant, so you can get away with a thinner rope. (In fact, they often aren't redundant: If you fall putting a piece 60 feet up, putting them every 15 feet, and the first rope breaks, will the second catch you? Nope. The ground will. See my first post. Fortunately, the first one won't break from a fall alone. See below.) - bigger ropes are more durable. thinner ropes save weight (Yes, Rope Knowledge 101. The question was NOT "why does anyone climb on an 11 mm?" but rather "what is different about double rope technique that makes it possible to get away with smaller ropes?" It ain't the redundancy. See above.) - The UIAA tests them at a lighter weight, dummy, so they can be smaller. (Um, WHY does the UIAA test them at a lighter weight? Not because they both hold the fall -- they aren't twins and don't share the weight. I think I know the answer now -- see below.) - All ropes can hold you, stupid. The bigger singles are just for safety. (same as above. What, if anything, makes double ropes appropriate for a different standard?) - If a fall breaks the first rope, the second will hold you since the first will have taken some of the force. (Sorry: if you place your pieces the same distance apart, the second rope will face at least as much force as the first. There's one exception -- see below.) - A second rope is a good backup in case the first is cut. (Totally true, but the UIAA tests in question are about breaking strength, not the edge-cutting test (which should be more popular, yes). Still the same question: what about half rope technique makes it possible to accept a lower standard in pure drop strength, compared to singles?) ---- I think this is why: * The second rope will never see a fall factor of much above 1. It's not because of redundancy. There is NO redundancy on the first pitch until you are higher than 4x(distance btwn pieces). Above that, the falls put less strain on the rope anyway. It's for the second, third, and fourth pitches, at the start of the climb. The UIAA single rope tests cover a fall factor of 1.78 for an 80kg climber -- a fall that could only happen near the anchor on a second+ pitch. The half rope test is for a 55kg climber. That's odd -- why 55Kg? The ropes DO NOT SHARE THE WEIGHT, unless clipped as twins, which is a different technique, with different pros and cons. Because they're trying to simulate a lower fall factor. A fall factor of 1.78 at 55Kg is the same as an 80Kg fall at factor 1.2. In fact, "factor 1.2" is sometimes cited as a standard in other discussions about half ropes, even though the UIAA uses the strange 55kgx1.78 fall factor test. They could, of course, change the drop distance and use an 80Kg weight, but I bet it's easier to change the weight than to move the equipment set at a given distance. Why does 1.2 make sense? Because unlike a single, half ropes can never face a factor 2 fall, not alone. Unlike singles, double ropes always face fall factors of less than 1.3. A fall right off the anchor on pitch two is a factor 2 fall, but it's shared by both halfs. A fall higher up can exceed 1.2 for the first rope but not the second. Say the first piece is 4 feet up and the climber falls putting in another 12 more feet up: 24 foot fall on 16 feet of rope= fall factor 1.5. It might break. The second rope, though, now faces a fall of 8 more feet feet on 16 feet of rope=.5, much smaller. 5 feet and a big 25 feet to the next? Factor 1.6 on the first, but only .16 on the second. You just can't generate a huge fall factor on the second rope alone. Overanalysis? Ask the folks 60 feet up who think the second rope will hold them. It won't, but it doesn't need to. The second rope is redundant for only two cases: when one is cut, and at the start of the second-and-higher pitches -- because THAT is when you need the backup. Except for those cases, you ARE climbing on a skinny single. And it'll hold you just fine then. Ross
  4. Look, here's the question, same as at the start: - How can double ropes get away with being smaller than singles? Here are the answers we've had so far: - double rope technique is good for a variety of reasons. (true. now back to the question) - ropes rarely fail (ditto) - the second rope acts as backup for the first (true, if cut. Yes, cutting is the primary reason for rope failure. But if we're talking about rope strength for absorbing a fall, the second rope faces at least as much force: not good when it was enough to snap the first. (We're talking double-rope technique here, not twins clipped together, which have their own pros and cons.) Also, if you clip alternately every 15 feet, the backup rope won't kick in until 60 feet plus rope stretch: 30 feet for the first one to fail, plus the 30 out on the second. Double ropes have low impact forces which means big rope stretch. On the first pitch, then, you need to be pretty high up -- or make your initial placements closer to each other-- before the redundancy applies.) No question about the advantages of the technique. No question that rope failure -- like most gear failure -- usually comes from human error and not integral weakness. But unlike twins, doubles take the force from a fall individually, and if the first breaks, the second faces a force at least as great. The only time this isn't true is for brutal falls exceeding fall factor 1, on later pitches, if the first piece is close enough to the anchor. So either our singles are also way too fat and heavy (which I can totally believe) or double-rope technique should include closer placements on the start of the initial pitch and and an even-more-crucial close first piece on following pitches.
  5. No offense to Forrest, but that's not right. The assumption that double ropes are "redundant" overlooks two problems: - even the backup rope must take the full force of the original fall and more (see the first example above). - when placing gear every 15 feet, the second rope will catch you without cratering only when you're above 75 feet or so. (again, see above). Until then, that first rope had better hold. I'm not saying double ropes don't work, but I am asking how they can get away with a smaller diameter. If they really are adequate, maybe our singles are fatter than they need to be -- since doubles each need to take the full force applied to a single. Ross
  6. Ok, gotta be clear. Yes, there are advantages to using double ropes, and that would make a fine additional thread. I'm with you on the benefits of the technique. Yes, ropes aren't likely to fail. Most accidents are human error. I'm with you there, too. The question is: - Why are half ropes made in smaller diameter than single ropes? In use, they'll face the same falls as single ropes -- see above -- so why a lower standard in strength? The UIAA force tests even subject them to a lighter test than singles. The "backup" idea is pretty questionable. In my example above, you'd have to be maybe 75 feet up for the second one to keep you from cratering -- the low impact force of double ropes means a lot of stretch. That leaves alotta time for you to climb essentially on one thin rope... And if it's just a lower standard we're accepting, why isn't that also the case for singles with limited use? I'd gladly take a rope on my next alpine climb if it could hold only three factor 1.5 falls -- instead of 11 at factor 2 -- but weighed half as much. Still baffled: half rope technique makes sense -- but don't the ropes face the same abuse as singles? Ross
  7. Why the smaller diameter? Totally puzzled. I've climbed on halfs/doubles a few times and see the rope-management advantages, but I just can't make sense of the skinny width. Take the classic half-rope scenario: stemming between two cracks, alternating pieces in each every 15 feet or so. A fall while placing a piece means a 30 footer (plus stretch), just as it does for a single -- except it's on an anemic little strand. If it blows, the "backup" rope sees a situation just as bad and worse -- 30 feet, plus all the remaining energy that wasn't absorbed by blowing the first. Here's a common response: "the work done on the first rope will have used up most of your KE, so the second rope will have an easy catch. " but he's suffering from a head injury. You've got out 30 feet on that second rope, too, and in the very best case -- that the first piece absorbed all of the KE from the first fall but blew just as you were coming to halt -- you face a fall of the same factor as before. In reality, it's going to be harder than the first one : more KE, and a fall of the same distance plus a few more feet to span the distance between the cracks. So why are half-ropes any different from singles? Don't they need to take the same kind of punishment? Ross
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