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mattm
Nov 29, 2007, 9:27 PM
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The last R&I had a BAD article on clipping your lead rope through the anchor. I totally disagreed with their recommendation TO DO IT. I believe that it's actually better to factor 2 your anchor directly from a few feet up rather than factor 1.8 it AND introduce a pulley system that greatly increases the force on the anchor.
While they do mention the pulley factor with numbers they fail to COMPARE it with the "Dreaded" factor 2 numbers.
http://www.rockandice.com/...=66&type=gearguy
I was trying to find an old article DIRECTLY discussing falls onto the anchor. a friend had scanned it for me years ago - I think it was from mountain mag and discussed as part of the article, Paul Boving's fall and death on Thin Fingers. It basically said a factor 2 onto an anchor with a belay plate will slip through said plate creating a dynamic belay and thus really not causing a factor 2.
Anyone want to help me out with a scan? RGOLD? Thoughts on this?
Here's my rough Quick and Dirty numbers.
Climber (185lbs) leads out 5 feet and falls the full 10 feet onto the atc belay.
Factor two with a force on the belay of ~ 9.44kN (used an online cal - that doesn't factor in dynamic slippage or rope impact force)
Now let's assume the climber clipped the anchor 1 foot above the ATC (typical) and falls. We now get a FF= 1.79 and a force of 8.496kN
Using the R&I 1.66 pulley factor the load on the anchor is now 14.1 kN! A difference of 4.66 kN Now, correct me if I'm wrong but that's not a trivial load on you anchor.
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reg
Nov 29, 2007, 9:53 PM
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mattm wrote: The last R&I had a BAD article on clipping your lead rope through the anchor. I totally disagreed with their recommendation TO DO IT. I believe that it's actually better to factor 2 your anchor directly from a few feet up rather than factor 1.8 it AND introduce a pulley system that greatly increases the force on the anchor. While they do mention the pulley factor with numbers they fail to COMPARE it with the "Dreaded" factor 2 numbers. http://www.rockandice.com/...=66&type=gearguy I was trying to find an old article DIRECTLY discussing falls onto the anchor. a friend had scanned it for me years ago - I think it was from mountain mag and discussed as part of the article, Paul Boving's fall and death on Thin Fingers. It basically said a factor 2 onto an anchor with a belay plate will slip through said plate creating a dynamic belay and thus really not causing a factor 2. Anyone want to help me out with a scan? RGOLD? Thoughts on this? Here's my rough Quick and Dirty numbers. Climber (185lbs) leads out 5 feet and falls the full 10 feet onto the atc belay. Factor two with a force on the belay of ~ 9.44kN (used an online cal - that doesn't factor in dynamic slippage or rope impact force) Now let's assume the climber clipped the anchor 1 foot above the ATC (typical) and falls. We now get a FF= 1.79 and a force of 8.496kN Using the R&I 1.66 pulley factor the load on the anchor is now 14.1 kN! A difference of 4.66 kN Now, correct me if I'm wrong but that's not a trivial load on you anchor.
notsure what i can offer here but most plates and tubes slip around 500-800 # (4-5kn). here's some thing of interest:http://hv.greenspun.com/...sg.tcl?msg_id=0004tT
also J. Long talks about the "jesus nut" or at least gettin cliped into a leg of the anchor - preferably a big solid nut! i'd rather deal with an upward pull then say spinnin upside down tryin to hold ah 2.
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glytch
Nov 29, 2007, 10:21 PM
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As to whether or not to use a redirect at the anchor, "It depends" (tm).
Here is something that I have been considering a lot recently, and I believe it's worth considering:
A redirect does not necessarily multiply forces to the extent to which we often assume it does. A thought experiment: suppose you are hanging on an anchor, and I mean literally hanging, as in, under a roof. Not at this really ever happens, but suppose you were. Now, consider that your partner has fallen and you are holding their weight using your belay device.
Case 1) the rope runs from your device, through a redirect at the anchor, and down to the climber.
Case 2) The rope runs directly from your device to the climber.
In either case, the anchor is holding exactly the weight of the two of you. No more, no less! While this is not exactly a real world scenario, it goes to show that if you are already weighting an anchor, a redirect does not increase forces by a factor of 2 (or ~1.6, discounting friction)! I don't know exactly the forces exerted on an anchor during a fall when the rope runs through a redirect, but it is clear that in such a scenario, forces are not multiplied by a factor of 2, since the anchor must, no matter what, support the weight of the belayer. A multiplying effect comes when an anchor that might support just a climber must now support a belayer as well; if the belayer must be supported either way, the multiplier will be reduced.
I think the more compelling reason than fall factor to use a redirect (sometimes, anyway, I'm not claiming that this is a hard and fast rule by any means!) is that it adds substantial friction in the case of a falling climber. I've never had the misfortune or bad luck to catch a steep factor 2 (and hope I won't have to any time soon), but from my experiences of lowering people directly off of my harness (body weight only, obviously), the force required from the belayer without a redirect 'biner is far higher than it is with such a biner. Moreover, there's the risk of spinning, jostling, or hitting the belayer, momentarily weakening their grip; if they lose control of rope for even a split second when they should be arresting a fall, it's very bad news! Every bit of friction helps.
G
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climbingaggie03
Nov 29, 2007, 10:27 PM
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I usually redirect on the anchor because I think it's easier to catch a fall with an upward pull than a downward pull.
On snake dike for example you have a 2 bolt anchor and your next piece of pro is a bolt 75 feet up. I didn't think I was going to fall, but I clipped the anchor cause If I did take the ride, I wanted my belayer to be pulled in the direction he was used to, also factoring in to the equation was that I was clipping one bolt which was pretty bomber so I wasn't worried about it failing.
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mattm
Nov 29, 2007, 10:45 PM
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climbingaggie03 wrote: I usually redirect on the anchor because I think it's easier to catch a fall with an upward pull than a downward pull. On snake dike for example you have a 2 bolt anchor and your next piece of pro is a bolt 75 feet up. I didn't think I was going to fall, but I clipped the anchor cause If I did take the ride, I wanted my belayer to be pulled in the direction he was used to, also factoring in to the equation was that I was clipping one bolt which was pretty bomber so I wasn't worried about it failing.
I'll agree that a bomber bolt on snake dike is not a bad redirect - I think it becomes a lot more important when you're redirecting off a nut in your anchor (10kn strength would hold a factor 2 but not the re-direct)
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coach_kyle
Nov 29, 2007, 10:46 PM
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If you question the strength of your anchors - and on many routes, this is a serious concern - you're right not to clip the leader through them. You essentially want the force to be spread out over the longest distance possible.
F*d = energy absorbed.
Either you can use a big force (rip out the anchors) over a short distance, or a small force (anchors hold) over a short distance.
However, if you are certain that your 3 - 4 pieces of gear are bomber, it is more convenient for the belayer to get pulled up than down. A downward pull that hard could hurt, depending on his body position.
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ja1484
Nov 30, 2007, 1:05 AM
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It's always situational. If the anchor is a bombshelter, I'll commonly re-direct through the powerpoint because the belayer losing control of the rope during a factor-2 directly onto their harness is more of a threat than the anchor ripping.
If the anchor is questionable, I'll usually suggest the leader aid out of the belay for two or three solid pieces, making us both feel better.
mattm wrote: A difference of 4.66 kN Now, correct me if I'm wrong but that's not a trivial load on you anchor.
Maybe, but two things:
1) Calculated fall forces have shown a tendency to be "high balls" in the past for a number of reasons.
2) Thinking in wider perspective, if there's a realistic chance the anchor's going to fail, perhaps it's best to try another route?
mattm wrote: I'll agree that a bomber bolt on snake dike is not a bad redirect - I think it becomes a lot more important when you're redirecting off a nut in your anchor (10kn strength would hold a factor 2 but not the re-direct)
I beg to differ. It's been pretty well good and shown that in actual practice (i.e. outside the lab), a climbing team using typical methods can't hit an anchor for more than ~2200lbs of force (10kN) (assuming they're not heavy climbers - that changes the game - say...185lbs each or less).
Additionally, fair enough, you manage to blow the nut... why didn't you re-direct through the equalized master point?
(This post was edited by ja1484 on Nov 30, 2007, 1:11 AM)
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climbingaggie03
Nov 30, 2007, 1:13 AM
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ja1484 wrote: It's always situational... Thinking in wider perspective, if there's a realistic chance the anchor's going to fail, perhaps it's best to try another route?
I agree, or build a better anchor.
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crotch
Nov 30, 2007, 2:00 AM
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ja1484
Nov 30, 2007, 3:54 AM
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crotch wrote: climbingaggie03 wrote: ja1484 wrote: It's always situational... Thinking in wider perspective, if there's a realistic chance the anchor's going to fail, perhaps it's best to try another route? I agree, or build a better anchor. Sometimes that's just not possible. Extending the belayer so that they are hanging well below the station and then redirecting through the belay will reduce the fall factor.
But not necessarily the forces (depending on how far the extension is v length of fall, and the second variable can't be known until after the fact), which is the point of the first post entirely.
An building a better anchor isn't always possible, but going home is always an option.
I think some people may be missing the point that I (a little too subtly) obliquely referred to in my previous post:
If you can't continue within a reasonable margin of safety, it's probably not a good idea to continue at all.
I know the drive to finish a route is strong when you're in the middle of the process, and I know everyone's level of risk acceptance is personal, but when we're talking about belay anchors with a realistic chance of failure, we've drifted from "How much am I willing to risk?" to "Am I willing to risk it all?", because that's essentially the situation. Furthermore, it's well known that our sport affords the largest amounts of glory to the people who walk the line closest to the edge - many testpieces are known as such not for their brutal physical toil, but the hazard to life and limb, even on technically easy terrain. Everest could be a well known example here.
I'm sure some of us have free-soloed at times. I'm guilty in that regard. All I can say in my defense is I chose the route carefully and developed a thorough familiarity with it before I attempted it solo.
You're choosing between bragging rights and lottery with the reaper when you climb above an uncertain anchor...if you have a family, or other similarly important obligations, you might wish to ponder for a moment before you make that choice. That's all I'm getting at.
(This post was edited by ja1484 on Nov 30, 2007, 3:55 AM)
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norushnomore
Dec 3, 2007, 9:49 AM
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In my limited experience I don't think there is a practical difference in the load on the anchor if you re-direct or not.
There is a theoretical one that spans great debates here that is for sure.
If you redirect the force of the fall will lift you up and into your redirect biner quickly converting to an off the anchor setup: no force multiplication.
Now what is more convenient, having your belay device jammed against an anchor or being flipped upside down?
I prefer flipped upside down, just make sure you have no slack in the setup: belay loop transferring all the force onto an anchor and not your harness.
Speaking of the Jesus piece. Of course I will plug my first pro as soon as I can but that is the wrong way to approach this issue.
Better option if you are facing a ff2 possibility is to lower your belayer 20-30 feet down. No more ff2, you can take all the falls you want.
Or, continue climbing till you place that Jesus piece and then lower back down to the where your belay station should be.
One last trick, if crux is close to the belay and fall is clean then simply feeding a few extra feet of rope will let you greatly reduce ff to a much more manageable number.
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billcoe_
Dec 5, 2007, 4:54 AM
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Interesting question Mattm. Worth exploring for sure. There are times I routinely do not clip the belay rope in depending on the potential fall situation. It's damn nice not too if you have a good belay stance but gear you don't want to stress in the event of a fall. I feel like you often get more of that with a direct fall onto your belay loop. Which seems to me can being less jarring to the system since your body can absorb some and the belay device can let some slack out. It does seem like you will get some absorbson even if you do clip in, as your body will lift up, softening the catch as well.
But I agree that it's situational, imagine trying to help your buddy out if he falls on a multipitch overhanging route and he's hanging full on right on your belay loop?
I did have that happen to me once to my follower when he blew an aid placemnt that had held me. I was glad that while Bob swung back in forth in space below me unable to touch any rock, with his backpack trying to pull him backwards to the point that he was hanging on hard with both hands (pumping out) to the rope to just keep from being pulled over backwards, that I had the forsight to have clipped the anchor with the belay rope beforehand.
It made fixing and dropping a loop of rope down down with some prussik's pre-arranged an easy and fast solution to his dilemma. Then between me yarding with my full body weight as I locked off and squatted, using my body weight (as opposed to pulling directly up), and Bob working the prussiks it worked out good.
The memorable part was that some other guys I knew were on the other side of the pinnacle, and were unaware that they were sharing it with anyone else till they saw (and heard the squeels) of Bob's feet swinging out, back and forth, back and forth. I still hear that story today.
Very situational it seems to me.
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