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superbum
Apr 25, 2007, 6:09 AM
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Yo. Before I get flamed, just gotta say that while new to a double rope system, I have considerable experiance belaying on multipitch climbs and am aware of the pros and cons of a redirect vs. a belay off the anchor (ex: munter or reverso) as well as direct off the harness...blah blah blah. My question is...When climbing on a double rope system and belaying the second off the harness, through a redirect at the anchor, is it common (safe) practice to clip both strands through the same biner at the redirect? In other threads (and elsewhere) it has been confirmed that double/half ropes, when clipped as twins (two strands, one biner) create a potentially dangerous situation w/ higher impact forces and melting ropes when catching a lead fall... I am planning on climbing on a 9.1 and an 8.6 together as doubles and am curious as to others' opinions on clipping both strands together into a redirect biner at the anchor...or would you ALWAYS use and autoblocking device such as the Reverso...? Will the impact force significanly increase? What do YOU do on multipitch alpine routes w/ doubles? Vic
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vegastradguy
Apr 25, 2007, 6:44 AM
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back when i used doubles on a regular basis (same diameter), i often used a redirect. i also found out quickly that if you clipped both ropes through the same biner and you use anything but an oval, the ropes can get pretty twisted over the course of a single pitch- often enough to force the second to untie. i dont think you have any major force issues, since your second is effectively toproping the pitch (obviously the redirect needs to be bomber).
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drzaous
Apr 25, 2007, 8:02 PM
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It is more dangerous to use different diameters through the same 'biner too. My advice would be to just use the autoblock. With doubles, it's just so much easier. I also just don't ever see a case where a redirect would be better than an autoblock (in both caces, the anchor has to be above you). I would just be worried about rope on rope friction from the different diameters (the thin rope is going to take it in the shorts). Just my thoughts though.
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superbum
Apr 25, 2007, 11:33 PM
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bump
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tallnik
Apr 26, 2007, 3:08 AM
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Autoblock is the way to go. Nik
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lovesclimbing
May 4, 2007, 2:56 PM
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Why do you want to climb on two diffrent size ropes? If you really wanted to redirect you could just take a sling and knot it in the middle in such a way to have a biner on ether side and than the sling cant move and you have your ropes in diffent biners, since your just belaying the follower with this system the knot isnt going to screw with any load issues that you may have. Why not just use an autoblock off the anchor? Is this set up for that you want for transion speed at the anchor when swinging leads? If it is than mabey you could just have 2 quick draws than for your redirect and not worry about the weight/space for a redirect sling.
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reg
May 4, 2007, 3:30 PM
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lovesclimbing wrote: Why do you want to climb on two diffrent size ropes? If you really wanted to redirect you could just take a sling and knot it in the middle in such a way to have a biner on ether side and than the sling cant move and you have your ropes in diffent biners, since your just belaying the follower with this system the knot isnt going to screw with any load issues that you may have. Why not just use an autoblock off the anchor? Is this set up for that you want for transion speed at the anchor when swinging leads? If it is than mabey you could just have 2 quick draws than for your redirect and not worry about the weight/space for a redirect sling. interesting - like a mini two point equalette - tie two overhands with one center strand slightly longer for a twist - X style - good thinking but i still like the autoblock best
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catbird_seat
May 4, 2007, 10:45 PM
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Belaying of the follower was addressed but belaying of the leader was not. Some people like to have a redirect when belaying off the harness to prevent the leader from falling directly onto the belayer in the event he falls before he gets a single piece of pro in. If you do this, the redirect should be either on the power point or a piece of pro separate from the anchor and you should only clip one of the two half ropes. The leader, after having placed his first piece, should clip the other rope. If the first piece is a bolt, I usually clip both ropes into it. Concerning rope diameters, as long as both ropes are rated as half ropes and you are clipping alternately, it does not matter that they are not matched in diameter. If you are using twin rope technique, then it does matter.
(This post was edited by catbird_seat on May 4, 2007, 10:48 PM)
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lovesclimbing
May 5, 2007, 3:52 AM
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I don't think that I have ever seen a bomber bolted belay in the alpine (hope I never do) and even if it is bolted when belaying a leader I would never have the belayer out of the loop. I fully believe in using the dynamic qualities of the belayers body in the system. The only time that I personally have the leader directly attached to the belay is clipping a single piece in hoping to prevent a F2 fall. When I was first using double ropes I once clipped them into the same runner but got in shit and haven't done it since. I have seen other people do and the odd time say something but it is a practice that I have not done save the first time. Although I have not used twin ropes so I would assume that the rope friction in the system comes from using the doubles on a wondering pitch.
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catbird_seat
May 6, 2007, 12:35 AM
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I can think of lots of reasons not to clip both strands of a HALF rope to each piece. Let me count the ways why you should clip alternately: 1) If you clip alternately, and you blow a high clip and fall, the other strand will catch you without the extra rope being out. 2) Less drag as there is less contact with rock and carabiners. If you clip both, you might as well use lighter twins. And a single would have less drag. 3) Lower impact force. Double strands means double the impact force. The only time I don't clip alternately is if I have wandered way off to one side of the route and will be coming back the other way.
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lovesclimbing
May 6, 2007, 5:43 AM
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On routes that have a large funny traverse such as the 2nd last pitch of Forbiden Corner on Yam (must do route with the 5.10 varation) you traverse 15m right climb 5m up and traverse 20m left with the most exposed moves at the start we only clipped the one line to the pro for the leader and once belaying the second used the other line to protect the exposed moves. Worked real well.
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mtnfr34k
May 10, 2007, 11:35 AM
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superbum wrote: Yo. Before I get flamed, just gotta say that while new to a double rope system, I have considerable experiance belaying on multipitch climbs and am aware of the pros and cons of a redirect vs. a belay off the anchor (ex: munter or reverso) as well as direct off the harness...blah blah blah. My question is...When climbing on a double rope system and belaying the second off the harness, through a redirect at the anchor, is it common (safe) practice to clip both strands through the same biner at the redirect? In other threads (and elsewhere) it has been confirmed that double/half ropes, when clipped as twins (two strands, one biner) create a potentially dangerous situation w/ higher impact forces and melting ropes when catching a lead fall... I am planning on climbing on a 9.1 and an 8.6 together as doubles and am curious as to others' opinions on clipping both strands together into a redirect biner at the anchor...or would you ALWAYS use and autoblocking device such as the Reverso...? Will the impact force significanly increase? What do YOU do on multipitch alpine routes w/ doubles? Vic Vic, to go back to your original post - I think the key ingredient is who you're belaying - the second. They won't generate a fraction of the force in a well-belayed TR fall as a leader, and I don't believe the concern of force impact on the gear - in this case a redirect off of the anchor - is as great as if we were talking about belaying a leader. I'd be cool with it. P.S. I still think you'd be better off belaying directly off the anchor in every possible circumstance - buy an ATC Guide!
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microbarn
May 10, 2007, 12:25 PM
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catbird_seat wrote: 3) Lower impact force. Double strands means double the impact force. We should harness your force doubling machine to power the world. Sorry, but this statement is just wrong. Two strands means that the force from each strand is applied to the pro. HOWEVER, the weight of the climber will be split between the two strands. So, the force from each strand is half as large. If one strand is clipped, then one strand will hold all of the weight of the climber. This implies that that one strand would be applying the full equivalent load to the pro. The force felt by the piece would be the same with one or two strands.
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microbarn
May 10, 2007, 12:28 PM
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superbum wrote: Yo. Before I get flamed, just gotta say that while new to a double rope system, I have considerable experiance belaying on multipitch climbs and am aware of the pros and cons of a redirect vs. a belay off the anchor (ex: munter or reverso) as well as direct off the harness...blah blah blah. My question is...When climbing on a double rope system and belaying the second off the harness, through a redirect at the anchor, is it common (safe) practice to clip both strands through the same biner at the redirect? In other threads (and elsewhere) it has been confirmed that double/half ropes, when clipped as twins (two strands, one biner) create a potentially dangerous situation w/ higher impact forces and melting ropes when catching a lead fall... I am planning on climbing on a 9.1 and an 8.6 together as doubles and am curious as to others' opinions on clipping both strands together into a redirect biner at the anchor...or would you ALWAYS use and autoblocking device such as the Reverso...? Will the impact force significanly increase? What do YOU do on multipitch alpine routes w/ doubles? Vic Didn't you post the exact same question here: http://www.rockclimbing.com/...post=1585822#1585822 Didn't you get your answer? What hasn't been explained yet? Is there a difference in the question I am missing?
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mtselman
May 10, 2007, 7:08 PM
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microbarn wrote: catbird_seat wrote: 3) Lower impact force. Double strands means double the impact force. We should harness your force doubling machine to power the world. Sorry, but this statement is just wrong. Two strands means that the force from each strand is applied to the pro. HOWEVER, the weight of the climber will be split between the two strands. So, the force from each strand is half as large. If one strand is clipped, then one strand will hold all of the weight of the climber. This implies that that one strand would be applying the full equivalent load to the pro. The force felt by the piece would be the same with one or two strands. Actually, you are completely wrong here. You would be right if the ropes were completely static (zero elasticity). With dynamic ropes, they stretch to absorb most of the impact of the fall. Two strands will stretch half as much thus placing double the impact on the point. To be more precise, by clipping two strands into a single point you are reducing "elasticity" of the system by a factor of two. That translates into double impact force. --Misha
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microbarn
May 10, 2007, 8:04 PM
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mtselman wrote: microbarn wrote: catbird_seat wrote: 3) Lower impact force. Double strands means double the impact force. We should harness your force doubling machine to power the world. Sorry, but this statement is just wrong. Two strands means that the force from each strand is applied to the pro. HOWEVER, the weight of the climber will be split between the two strands. So, the force from each strand is half as large. If one strand is clipped, then one strand will hold all of the weight of the climber. This implies that that one strand would be applying the full equivalent load to the pro. The force felt by the piece would be the same with one or two strands. Actually, you are completely wrong here. You would be right if the ropes were completely static (zero elasticity). With dynamic ropes, they stretch to absorb most of the impact of the fall. Two strands will stretch half as much thus placing double the impact on the point. To be more precise, by clipping two strands into a single point you are reducing "elasticity" of the system by a factor of two. That translates into double impact force. --Misha no You could have a point that the ropes would act as springs in parallel, but the biner DOES NOT impart a pinned end condition. Your assumptions are incorrect
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mtselman
May 10, 2007, 9:02 PM
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microbarn wrote: mtselman wrote: microbarn wrote: catbird_seat wrote: 3) Lower impact force. Double strands means double the impact force. We should harness your force doubling machine to power the world. Sorry, but this statement is just wrong. Two strands means that the force from each strand is applied to the pro. HOWEVER, the weight of the climber will be split between the two strands. So, the force from each strand is half as large. If one strand is clipped, then one strand will hold all of the weight of the climber. This implies that that one strand would be applying the full equivalent load to the pro. The force felt by the piece would be the same with one or two strands. Actually, you are completely wrong here. You would be right if the ropes were completely static (zero elasticity). With dynamic ropes, they stretch to absorb most of the impact of the fall. Two strands will stretch half as much thus placing double the impact on the point. To be more precise, by clipping two strands into a single point you are reducing "elasticity" of the system by a factor of two. That translates into double impact force. --Misha no You could have a point that the ropes would act as springs in parallel, but the biner DOES NOT impart a pinned end condition. Your assumptions are incorrect Sorry, but you are wrong. I think you are confusing weight with force. Let me simplify. Remember F=ma? Well, when you are falling, just before the rope "engages" you have a velocity V. It pretty quickly goes to 0 as you decelerate. That's the acceleration parameter "a". The faster you decelerate, the higher that value is. When the rope is very elastic, the acceleration (deceleration in this case) value is smaller. That makes for a lower value of force. When you double up both strands of the rope, the elasticity decreases, so the acceleration and therefore the force increases. (using absolute numbers here) Just imagine falling on a very soft elastic rope compared to a very stiff 11+mm rope. When do you think the force on the point will be higher? --Misha PS. Draw a diagram with forces.
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microbarn
May 10, 2007, 9:06 PM
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mtselman wrote: microbarn wrote: mtselman wrote: microbarn wrote: catbird_seat wrote: 3) Lower impact force. Double strands means double the impact force. We should harness your force doubling machine to power the world. Sorry, but this statement is just wrong. Two strands means that the force from each strand is applied to the pro. HOWEVER, the weight of the climber will be split between the two strands. So, the force from each strand is half as large. If one strand is clipped, then one strand will hold all of the weight of the climber. This implies that that one strand would be applying the full equivalent load to the pro. The force felt by the piece would be the same with one or two strands. Actually, you are completely wrong here. You would be right if the ropes were completely static (zero elasticity). With dynamic ropes, they stretch to absorb most of the impact of the fall. Two strands will stretch half as much thus placing double the impact on the point. To be more precise, by clipping two strands into a single point you are reducing "elasticity" of the system by a factor of two. That translates into double impact force. --Misha no You could have a point that the ropes would act as springs in parallel, but the biner DOES NOT impart a pinned end condition. Your assumptions are incorrect Sorry, but you are wrong. I think you are confusing weight with force. Let me simplify. Remember F=ma? Well, when you are falling, just before the rope "engages" you have a velocity V. It pretty quickly goes to 0 as you decelerate. That's the acceleration parameter "a". The faster you decelerate, the higher that value is. When the rope is very elastic, the acceleration (deceleration in this case) value is smaller. That makes for a lower value of force. When you double up both strands of the rope, the elasticity decreases, so the acceleration and therefore the force increases. (using absolute numbers here) Just imagine falling on a very soft elastic rope compared to a very stiff 11+mm rope. When do you think the force on the point will be higher? --Misha PS. Draw a diagram with forces. No no I understand what you are saying, and you are still wrong. When I have more time I will try to write out why.
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mtselman
May 11, 2007, 1:44 PM
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microbarn wrote: No no I understand what you are saying, and you are still wrong. When I have more time I will try to write out why. Please do! New discoveries in physics are always exciting! --Misha
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paulraphael
May 14, 2007, 3:35 AM
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mtnfr34k wrote: Vic, to go back to your original post - I think the key ingredient is who you're belaying - the second. They won't generate a fraction of the force in a well-belayed TR fall as a leader, and I don't believe the concern of force impact on the gear - in this case a redirect off of the anchor - is as great as if we were talking about belaying a leader. I'd be cool with it. P.S. I still think you'd be better off belaying directly off the anchor in every possible circumstance - buy an ATC Guide! I'd agree with this, except that in an alpine setting sometimes you won't find an anchor that you're 100% happy with. In these cases it's better to use your body braced against terrain features to support the 2nd if he falls, and think of the anchor as a backup. As far as the original question goes, the danger of clipping both ropes through one biner exists on lead, when the ropes elsewhere on the pitch are clipped alternately. In such a case, a fall will pull the strands at different speeds through the biner, with a lot of force. this creates the possibility of the ropes burning each other. not an issue when belaying the 2nd.
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paulraphael
May 14, 2007, 3:40 AM
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mtselman wrote: microbarn wrote: No no I understand what you are saying, and you are still wrong. When I have more time I will try to write out why. Please do! New discoveries in physics are always exciting! --Misha Microbarn, you are indeed proposing a new discovery in physics. I suggest you re-read Misha's explanation. Or at the very least, follow the manufacturer's instructions, and don't try to use ropes as twin ropes when they're rated only for use as half ropes. You could create impact forces that are way higher than what any of the gear (or your spine) was ever designed for.
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iceisnice
May 14, 2007, 3:27 PM
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this thread is a good example why you shouldn't get technical data from this site. don't be lazy and actually look up the research. call the companies that have ACTUALLY conducted these kinds of tests (BD, Petzel, etc). get THEIR opinions. it is VERY dangerous to get this kind of info from the site. most people here don't have a clue. just because someone says their are a "physicist", doesn't mean they know what they are talking about. ask the REAL experts......the guys who do this for a living.
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microbarn
May 17, 2007, 4:56 PM
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iceisnice wrote: this thread is a good example why you shouldn't get technical data from this site. don't be lazy and actually look up the research. call the companies that have ACTUALLY conducted these kinds of tests (BD, Petzel, etc). get THEIR opinions. it is VERY dangerous to get this kind of info from the site. most people here don't have a clue. just because someone says their are a "physicist", doesn't mean they know what they are talking about. ask the REAL experts......the guys who do this for a living. I agree I haven't taken any time out to explain why. Here is a link where papounet does some good explaining. http://www.rockclimbing.com/...post=1596633#1596633 I also want to point out that slack in one rope will be more then the other when used as doubles. Using ropes as twins continuously reduces this problem.
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paulraphael
May 18, 2007, 8:04 PM
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The conclusions of that thread are the same as mine and iceisnice's ... follow the manufacturer's recommendations. There are several ropes on the market now rated for use as both twins and halfs, but you can't assume all are. In the past none were. And the reason is the simple physics that you seem to be arguing against: a pair of ropes has a higher modulus than one rope, so according to hook's law, impact forces will be higher for a pair than for one. If a rope is rated for use as halfs and twins, it just means that the rope can still manage to keep fall forces within the limits set by UIAA. Just keep in mind those limits are high (12kn??) ... so while they're officially approved, it may still not be the safest bet in all circumstances. I would question why, outside of ice climbing, anyone wants to climb with twins at all. But that's a different topic.
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