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nick d
Trad climber
nm
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Nov 29, 2008 - 02:27pm PT
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John R., I guess my question is how far could the belayer really go? I've been jerked a couple of times over the years while standing at an awkward stance, but thats a distance of maybe ten inches, a foot at most? I think I probably absorbed some of the energy before I came tight to the anchors.
I'm not a math guy, I'm just relating this to my personal experiences, so I might be full of it! I just don't see how I could have added much more than my bodyweight to the system, and in most cases I would have already been semi-hanging on the anchors before the fall.
I still see my contribution as a shock absorber more than a huge increase in the ultimate load.
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JohnRoe
Trad climber
State College, PA
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Nov 29, 2008 - 02:42pm PT
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nickd wrote
"John R., I guess my question is how far could the belayer really go?"
Yes, this is the key question. Think about it this way. The force needed to stop a factor 2 freefall is about 7kN. The rope modulus is about 11kN. So, the tether could stretch by well over 50% under the kind of forces that are going to be developed in a factor 2 situation. (This is just a ballpark figure of course.) Since this stretch happens in a few hundred milliseconds the belayer is moving surprisingly fast - in my model the belayer ends up moving at 4 m/s. Not as impressive as the 12 m/s the leader achieves when he hits the end of the rope after the factor 2, but enough to require quite some retarding force.
Of course, the belayer's stance can mitigate some of this.
JohnR
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nick d
Trad climber
nm
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Nov 29, 2008 - 03:05pm PT
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John R., I guess I kind of got away from my original point, that being the forces have to be lower with a dynamic tether rather than a static one. I still believe that.
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rgold
Trad climber
Poughkeepsie, NY
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Topic Author's Reply - Nov 29, 2008 - 03:43pm PT
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Karl Baba wrote: "It seems that your technique is the worst of both worlds to some degree. In a big factor two fall, the anchor is going to have to hold you and the leader, and you still have the disadvantage of being pulled down."
Karl, here's the situation: The maximum elongation you are going to see in a dynamic rope is perhaps 38% (according to the Beal site---Beal ropes are typically among the stretchiest.) That's after the first fall under carefully controlled conditions; in the field with a used rope you'd expect a bit less.
Sticking with 38% and assuming a 3 foot tie-in, the biggest elongation you might possibly see is about 14 inches. So the belayer, who is not taking the direct load of the fall on his or her harness, will be forced, in the worst-case scenario, to do a deep-knee bend as the load is absorbed by the anchor, even if the belayer is hanging in slings. This is very far from the belayer being another falling object in John's calculations; it is conceivable if not likely that the belayer's presence would have no effect at all on the peak load, and it is also conceivable that the application of belayer quadricep power could effect a minor reduction.
By the way, as a reality check, this is pretty much exactly what happened to me on the factor-two fall I caught.
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GOclimb
Trad climber
Boston, MA
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Nov 29, 2008 - 03:48pm PT
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Rgold said: "John Stannard... is the only person I know of personally who has placed gear, made an evaluation, and then tested the placement to see how his judgements corresponded to reality."
For what little it is worth, I have also done the above.
My takeaway from the experiment was two things:
1 - I personally developed a better eye at evaluating the placements (within the narrow range of types of rock and types of gear I used). This has some value to me personally as a climber, but no relevance to this discussion.
2 - The realization that in small to mid sized cam placements (up to around 1 inch) the conventional wisdom about which placements are "bomber" is so naive as to be effectively wrong.
To elaborate on point 2: What I found was that very minor features of the placement (nearly impossible to determine without a trained eye and plenty of time to fiddle) can mean the difference between a piece ripping out versus holding, in relatively small falls (on the order of FF = .2 - .5) Factors like a little grit in the crack, or the relation of one lobe on versus behind a crystal.
Basically, the only "bomber" small to medium-small cam placement is one behind a constriction in good rock. All others take a very very careful eye to determine the likelihood of holding. And honestly, it's so variable depending on the quality of the rock in the crack, that you're better off just assuming that if it's not behind a constriction of some type that it is *not* bomber.
GO
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rgold
Trad climber
Poughkeepsie, NY
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Topic Author's Reply - Nov 29, 2008 - 04:34pm PT
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Gabe, I salute your wisdom and industry and welcome your observations.
I've always assumed that cams 1" and less belonged to the grey part of the spectrum I described earlier. Within the last year I was forced to use such an anchor, four sub-1" cams in a horizontal sandstone crack. Each one was "good," but I was not happy. It was clear that the next pitch wouldn't have any protection for a long while, and the rock that we were on was not perfect. I had plenty of confidence in my companion, but still thought a factor two fall onto this set-up was a possibility.
No way in hell would I have clipped that anchor. I equalized the placements in pairs with sliding X's and clipped each one with one strand of our double climbing rope. Fancier set-ups would have resulted in too long an anchor and would have forced me to hang from it, and I wanted to get braced as much as possible to spare the anchor. The belay was in a kind of sloping dish and such bracing as was possible was cramped and not very effective, but I judged it better than nothing.
I went over and over in my mind how I would not instantly clamp down hard if there was a fall, feeling certain that a longish dynamic ride for the leader that ended with a stop would be considerably more welcome than the much longer fatal ride that a non-dynamic belay might provide. I felt some gratitude for an old-school past that included actually practicing such things; my intentions were not entirely theoretical.
Of course, nothing happened, as is usual. I think I had it covered, but am happy to say we'll never know.
P.S. No calculators were used during this process, nor was the system of differential equations for coupled harmonic oscillators consulted.
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TradIsGood
Chalkless climber
the Gunks end of the country
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Nov 29, 2008 - 04:48pm PT
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JohnR,
I could not get access to the spread-sheet on your server...
EDIT:
BTW. Check the belayer's displacement in your model. It probably will NOT show him moving down.
The force on the tether will grow as the force on the faller side increases (with stretch). Eventually the force may exceed his weight, at which point he will accelerate upward.
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JohnRoe
Trad climber
State College, PA
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Nov 29, 2008 - 05:22pm PT
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TiG
Sorry. It should be accessible again now.
rgold
I feel that the dynamic aspect of belaying (whether intended or not) may be the downfall of many of these models. In the new anchor book, p104, JL claims that "the maximum force a modern belay device can put on the rope without slipping is 2-3kN".
Let's assume for a moment that the force at the belay device is limited to 3kN. Then the maximum anchor force in the factor 2 situation (scenario 1) is about 4kN (3kN plus the belayer). In the "pulley" situation (scenario 2) it will be 3kN to the belayer plus 3/0.7 kN to the climber - total over 7kN. If the anchor is marginal, as in the situation you just described, this is a big difference.
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JohnRoe
Trad climber
State College, PA
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Nov 29, 2008 - 05:25pm PT
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TiG wrote "BTW. Check the belayer's displacement in your model. It probably will NOT show him moving down."
This is "scenario 3", right? I measure the diaplacements downward, and so as this displacement becomes negative, the belayer is actually moving up. I'm sorry the graph is confusing.
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chainsaw
Trad climber
CA
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Nov 29, 2008 - 08:09pm PT
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this topic rules! Bump
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jstan
climber
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Nov 29, 2008 - 08:16pm PT
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GO
At the time I was doing my work cams had as yet to be invented. This is why I talk about observing the area of aluminum which would have to shear in order to result in failure. By looking at the area to be sheared one is able to avoid placements where small rugiosities may cause a failure.
I never tested a cam either in the lab or in the field.
When cams did come out their complexity caused me to hold off on adopting them.
Each of us is conditioned by our past experience. Rgold's past experience revolves around his understanding with quite some precision the forces he is able to withstand. I have learned not to question his judgment. He has always been right and has been so with great regularity. My own experience picking stone in the fields convinced me early on I was completely helpless when faced with a rock weighing 1000#. If a force of that magnitude were applied to my midsection as a millisecond impulse, I have not the slightest doubt as to the result. Not surprisingly I don't propose to do an experiment.
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Karl Baba
Trad climber
Yosemite, Ca
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Nov 29, 2008 - 09:01pm PT
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One important things about cams is they don't have the same sheer problems that nuts do because they expand. (there may be some devils in the details) Just because they drag a bit because of rock texture doesn't mean they blow.
They can trench their way out of soft rock but I stay away from that stuff!
peace
karl
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Largo
Sport climber
Venice, Ca
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Nov 29, 2008 - 10:35pm PT
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RGOLD wrote: "I clip my belay device into both the harness belay loop AND the tie-in knot loop of my anchor rope. This means that loads to the belay device are transmitted to the anchor directly, rather than loading up the belayer's harness first. However, since the anchor rope stretches, the belayer has some opportunity, in the case of the high loads of a factor-two fall, to resist with appropriate stancing, to use Joe's term, and thereby reduce to some extent the total load to the anchor. Since the connection is direct, the increase in load guaranteed (sorry, Karl) by the pulley effect after the break-even point is not a consideration."
That's an interesting and IMO, hopeful new wrinkle on the "direct belay." There's no load multiplication/pulley effect from a standard clip-through redirect, and the two to three foot shank of lead line/tether adds an important dynamic quality into the belay chain, while at the same time allowing for "stancing."
A curious thing per those rare cases of total anchor failure - I wonder how many times the leader actually fell onto the belayer? No way to ever know, perhaps, but in the case of the DNB team, that was last seen alive high in the upper chimneys - it's not steep enough up there to fall over the belayer, and a fall in many places in those chimneys would essentially funnel the leader right into the belayers lap.
JL
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tito
climber
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Nov 30, 2008 - 01:33am PT
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> If both the tie-in and the belay both come off the crotch loop you
> better have a loop of 1" tubular directly backing that up to your waist loop.
No need for the 1" tubular. There's a loop of climbing rope available to clip into, which also serves to reduce the number of single point failures in the system.
> Now here's the critical detail: I clip my belay device into both the harness
> belay loop AND the tie-in knot loop of my anchor rope.
I was taught to do the same. I would think the practice would be ubiquitous by now.
> There's no load multiplication/pulley effect from a standard
> clip-through redirect
Huh? Redirect = pulley effect, so then what's a "standard clip-through redirect"?
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Largo
Sport climber
Venice, Ca
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Nov 30, 2008 - 03:13am PT
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> There's no load multiplication/pulley effect from a standard
> clip-through redirect
Huh? Redirect = pulley effect, so then what's a "standard clip-through redirect"?
You're puling this out of context. There is no pulley effect so long as you clip in as Rich described, unless I'm not visualizing it correctly.
JL
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healyje
Trad climber
Portland, Oregon
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Nov 30, 2008 - 03:34am PT
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sibylle: "What I mentioned earlier - what if a climber that weighs 100 to 120 pounds belays a climber who weighs 180 to 220 pounds? Have any of you caught a leader who weighed almost one hundred pounds more than you? I have. It sucks no matter how you belay them."
Sibylle, it's hard not to sympathize with a situation you clearly encounter all the time. As jstan said, dealing with a large weight differential is an under-discussed affair. But in the end, the onus is on you to mitigate the situation by either tying down or using the sort of hybrid system rgold describes. I still think employing the anchor for that purpose isn't the best idea, but if that's your chosen solution then I hope you beef up your anchors [where possible] for such situations.
Karl Baba: "You still get plenty of "feel" for the climber (like fishing) if you use your hands on both sides of the device when bringing up the second. It's so easy you get a better cool down at the belay and makes it easy to manage the rope for the next lead."
I consider managing and stacking the rope to definitly be part of the craft of belaying and orderly climbing in general; for that matter finding interesting ways of stacking over natural features around the belay can actually make it almost entertaining (I suppose that unavoidably makes me an uber geek)".
jstan: "If someone criticizes another's technique but cannot give a persuasive argument you know right away what to do."
I'm not really trying to be 'persuasive', just give my opinion - folks can take or leave it. But when I say belaying off the anchor "divorces you from any number of sensory pathways" I mean way more than just the 'fishing' part of things, but it quickly gets back to stancing issues and facets of a belayer's interaction with, and on-going knowledge of, the anchor and constituent elements. Even knowing what's happening after a fall comes into play as well.
rgold: "If you do not accept that some of the time you are belaying off anchors that may not be bombproof, read no further."
There's probably some influence on this topic due to the kind of rock folks are used to. I'm a sandstone climber by history and proclivity. I suspect the notion of an 'anchor' for me connotes something a bit different than for Valley climbers used to what, for me anyway, is granite of an almost alien hardness. Maybe there's a generational element at play as well; back in the day we tackled lots of lines and FA's with a set of hexs and one of nuts and on occasion arrived at a belay or the end of a rope with just a stopper or two. The whole notion of an 'anchor' was definitely a means of last resort for stopping a partner's fall in those situations. Stancing played an enormous role in our climbing as we tried to never rely on anchors unless there was absolutely no other option, no matter how bomb.
rgold: "It does mean, for upper belays, that the belayer has to be actively engaged in the belaying process,"
"Actively engaged", in as comprehensive a context as possible, would seem the name of the game everytime.
Karl Baba: "A not-insignificant advantage of the gri-gri belay of the second is this. If there is a spray of rockfall from above (and this happens!) It would be possible for the belayer to fall and the belayer to get hit by rocks at the same time."
This I do consider an edge case I'm not willing to let drive how I belay beyond where I put a belay and how much slack I give myself to move in cases where known or suspected loose rock is involved with a pitch.
GOClimb: "To elaborate on point 2: What I found was that very minor features of the placement (nearly impossible to determine without a trained eye and plenty of time to fiddle) can mean the difference between a piece ripping out versus holding, in relatively small falls (on the order of FF = .2 - .5) Factors like a little grit in the crack, or the relation of one lobe on versus behind a crystal."
I think that placing pro well in general requires being fairly critical and paying attention to a very fine level of detail. I found once I started doing that my pro and anchors improved. Then again, it also greatly increased my awareness and consideration for all the 'grey areas' of climbing. Those grey areas are what reiterated for me the importance of stancing and having the human body in the 'chain' to protect the anchor.
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Karl Baba
Trad climber
Yosemite, Ca
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Nov 30, 2008 - 10:16am PT
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"> Now here's the critical detail: I clip my belay device into both the harness
> belay loop AND the tie-in knot loop of my anchor rope.
I was taught to do the same. I would think the practice would be ubiquitous by now. "
I'd have to question the importance of this. Let's say the belay device is just clipped in the belay loop and you're tied into the loop of rope which is also captured in the harness within one inch of the belay loop. Aren't we talking about a few inches of difference before, in effect, the belay device is weighting the tie-in rope in the same manner?
You do get a bit of redundancy but I've only heard of one belay loop failing and that was a freak accident and not in a fall. In any case, you're still trusting one biner and device to save the day. On the other hand, this whole belaying scenario is going to a make it hard to either escape the belay or set up a haul to get an injured or unconscious partner back up to the belay. If you have a redirect, it's WaY easier.
Some have said needing to escape the belay or haul the partner are rare things but so are the other dangers to the anchor discussed here.
Peace
Karl
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Karl Baba
Trad climber
Yosemite, Ca
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Nov 30, 2008 - 10:24am PT
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Healyje wrote
"There's probably some influence on this topic due to the kind of rock folks are used to. I'm a sandstone climber by history and proclivity. I suspect the notion of an 'anchor' for me connotes something a bit different than for Valley climbers used to what, for me anyway, is granite of an almost alien hardness. Maybe there's a generational element at play as well; back in the day we tackled lots of lines and FA's with a set of hexs and one of nuts and on occasion arrived at a belay or the end of a rope with just a stopper or two. The whole notion of an 'anchor' was definitely a means of last resort for stopping a partner's fall in those situations. Stancing played an enormous role in our climbing as we tried to never rely on anchors unless there was absolutely no other option, no matter how bomb"
This is for sure true in many ways. Granite and certain sandstone (like sedona) are so different, it's like the difference between jumping out of an airplane with a parachute and free-soloing with a base rig.
In the valley we almost always have way bomber anchors but "stancing' is often very limited because of so many hanging belays and tiny stances.
Peace
Karl
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rgold
Trad climber
Poughkeepsie, NY
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Topic Author's Reply - Nov 30, 2008 - 01:30pm PT
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Karl has taken exception to the anchor clip-in method I described: "I'd have to question the importance of this. Let's say the belay device is just clipped in the belay loop and you're tied into the loop of rope which is also captured in the harness within one inch of the belay loop. Aren't we talking about a few inches of difference before, in effect, the belay device is weighting the tie-in rope in the same manner?
It could conceivably be similar if you cranked the anchor tie-in tight enough, but you'd be uncomfortable, and I've just never seen anyone do this in practice. Even cranked tight, you'll have the anchor tie-in pulling up on the harness and the belay loop pulling down---opposing forces that threaten harness integrity in the factor two scenario. Since people never ratchet up their tie-in this tight in the real world, what actually happens is what Sibylle described and I responded to: a fallen second ends up with a lot of weight on the harness and the belayer experiences all the discomfort she alluded to. In the set-up I described, the belayer experiences no stress whatsoever.
In the case of a factor two fall, the difference is that the belayer's harness and body aren't subject to the violent impact of the shock, giving them a better chance of staying in control, not to mention sparing them the bruising the harness would otherwise impart. The belayer is less likely to be flung off their stance and become another falling object the anchor has to stop, and the belayer's harness is less likely to be damaged by large opposing forces. In this regard, perhaps we should attend to what the harness designers have to say about this situation. Here is BD harness designer Tom Jones, as quoted by Chris Harmston on rec.climbing in 1995:
"The leader could fall directly on the belayer with no intervening pieces
so the belay loop system must be able to hold that 3372 lbs of force. This
brings up why it is important to clip your belay device into
both your belay loop and the loop of the rope on multi pitch climbs. The
lead rope should be your primary anchor - your primary link from your
harness to the anchor - because it is dynamic and flexible. Your belay
biner should connect directly to the rope tie in loop so that the forces
of the belay can link directly to the anchor. Otherwise, the forces from
a severe fall would run from your belay biner to the belay loop,
to the harness, to the rope loop to the anchor. This would tend to rip
the harness apart and the results are very unpredictable. It is much
better to have the forces transfer as directly as possible to the strong
point in the system - your fully equalized, three bomber pieces anchor."
I learned the technique from this post.
By the way, although I don't necessarily agree with a harness designer's take on anchor construction, honesty and a respect for getting at the truth oblige me to also record that Tom said,
"The worst case fall is where the leader does not get any pieces in, then pitches
off and falls directly on the belay. Climbers are usually smart enough
to clip the lead rope into a draw on the anchors, so that the belayer
experiences an upward force, but this is not always the case."
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Steve Grossman
Trad climber
Seattle, WA
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Nov 30, 2008 - 01:58pm PT
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Having sucked many a light belayer up into the first piece of pro in line, I always chuckle at this Sheridan cartoon.
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