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venezuela
Aug 14, 2003, 10:16 PM
Post #26 of 34
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Registered: Jul 15, 2002
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In reply to: In reply to: should I tie in with independents slings?? and if so, where do I redirect from?? Yes/ sling and the rope, equalized. redirect/ I probably wouldn't if the anchor was bad
what alpnclmbr1 responded cought me a little off-guard....how can you have an equalized anchor setup with out the sliding X?.
I thought that the only way to distribute the weight equally was to use the slider knot. I'm aware of other setups, like using a cordalette, but does it equalize the anchor, or just provides several points to tie in without distributing the total weight?
what are those other methods?...
this has become a great class.....i'm eager to keep learning
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alpnclmbr1
Aug 14, 2003, 11:32 PM
Post #27 of 34
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Registered: Dec 10, 2002
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Assume a bomber two bolt anchor for simplicity.
A sliding X is equalized and automatically adjusts if you move the direction of load. These benefits are usually outweighed by the shock load risk. If you do use a sliding X make sure to use two slings to maintain redundancy
A cordelette is equalized for a predetermined direction of load. (I personally do not like cordelettes)
If you use two equal length slings it is equalized for a straight down direction. It is just as good as a sliding X for that direction without the risk of extension. Useful for a hanging belay.
Clove hitch your rope into one bolt and use a sling (or daisy) for the other bolt. This provides an easily adjustable system for different load angles. Redirect off one of the bolts (or not for a toprope) and tie a fig 8 on a bight into the second bolt for extra back-up. This is what I usually do as I almost always swing leads.
some may disagree with this
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allthetime
Sep 2, 2003, 9:49 AM
Post #28 of 34
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Registered: Aug 29, 2003
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In reply to: Consequently, the very least the anchor can be subjected to if the belay device is attached directly to the anchor is twice the second's weight.
I have two questions for you:
1) What do you believe is the force exerted by a 150 lb. climber who is hanging on the rope and is being belayed directly off the power point of the anchor with a munter hitch? Assume the force needed by the belayer to lock off a munter hitch and hold the climber is 0. You can take your pick between a static rope or a dynamic rope, and you can substitute a Reverso for the munter hitch.
2) Same situation as in 1) except you are belaying off your waist and you have redirected the belay through the power point of the anchor. Assume the force of friction at the power point is 1/3 the weight of the climber.
Hear are the correct answers:
1)Belaying directly off the anchor: the anchor is subjected to a downward force of 150 lbs. regardless of whether it's a static rope or a dynamic rope. (not a minimum of 300 lbs. as you seem to claim)
2)Belaying off your waist with the belay redirected through the anchor: If the power point were frictionless, the force on the anchor in the downward direction would be the 150 lbs. from the hanging climber on one side of the power point carabiner plus the 150 lbs. of force provided by the belayer and his belay device on the other side of the carabiner. Since friction is supplying 1/3 of the force necessary to hold the hanging climber, the force required by the belayer and his belay device to keep the hanging climber from falling is only 2/3 of the weight of the climber, or 100 lbs. So, the total force on the anchor in the downward direction, is 250 lbs.(not 500 lbs. as you seem to claim).
If the anchor is somewhat sketchy, you want to belay directly off the anchor to keep from multiplying the forces on the anchor by 1 2/3. If rope slips through the belay device or munter hitch as the climber impacts the anchor, that will also serve to reduce peak forces on the anchor. Another plus for belaying directly off the anchor is that in a self rescue situation, you don't have to escape the belay.
In reply to: when you have a 2 point anchor, tying in with the slider knot, and decide to belay from the waist you redirect from a). the strongest point alone, or b). from the slider knot point ??" The situation is when the anchor points are NOT bomb proof...
Since your anchors are not bombproof, and there are only two of them, then choosing a sliding x will serve to direct half the impact force of a fall to each piece, and eliminate the possibility of one piece being subjected to significantly more force than the other.
You wouldn't redirect through one piece because that would defeat the whole point of your sliding x anchor: with a belay redirected through one piece you would be causing 1 2/3 times the impact of the climber's fall to hit that piece alone. Let's assume a climber fell and exerted a peak force of 610 lbs., and that the piece you redirected through could withstand 1000 lbs of force. The force on that one piece would be 610 x 1 2/3 = 1016 lbs, and so that piece would rip, and assuming the other piece was equally poor, then the second piece would rip in succession. Therefore, your anchor would have completely ripped out when a climber's fall generated 610 lbs of force.
On the other hand, if you redirected through the sliding knot, and if your pieces formed an angle of say 40 degrees, then that same fall would exert 1016 x .54 = 549 lbs on each piece, and your anchor would easily survive the climber's fall.
The best solution would be to belay directly off the sliding x. That way the 610 lbs of force the climber generated would not be multiplied by 1 2/3 as with a redirected belay and each piece would experience only 610 x .54 = 329 lbs of force, so each piece could be as weak as 500 lbs and still survive the impact of the fall with some margin to spare.
As your anchor gets worse, you want to put your body between the climber and the anchor so your body can absorb most, if not all, of the impact force. In that case, you would tie into your anchor and then belay directly off your waist: the rope would run from your belay device directly to the climber, and you would try to brace yourself such that the impact of a fall would never reach the anchor.
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gyngve
Sep 2, 2003, 10:37 AM
Post #29 of 34
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Registered: Dec 28, 2002
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In reply to: that question brought other topics to the discussion, like: where on the anchor do you have to re-direct when belaying the second from the waist?; when you only have 2 points to anchor in, what setup do you use?; when the placements are body-wheight only, or very marginal, what setup do you use?...etc...
I don't understand why you're so worried about the follower coming up to that anchor... I'd be concerned about the next lead!
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brutusofwyde
Sep 2, 2003, 5:37 PM
Post #30 of 34
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Registered: Nov 3, 2002
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In reply to: while belaying the second, what setup puts the most stress: belaying from the anchor (reverso, munter hitch, ABS...) or from the waist (figure 8, ATC, grigri, munter hitch...) re-directed through the anchor?
Unless the anchor is bogus, other factors are more important to me than stress on the anchor: location of the anchor, how hard the pitch is, how well my partner is climbing, how much my partner weighs, whether it is a hanging belay or an excellent "keyhole" stance, how much rubble there is laying about that could get knocked onto my partner, heck, even whether we are leapfrogging pitches or climbing block style.
If the anchor is bogus, and I have a bomber stance, I belay from the waist.
Brutus
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alpnclmbr1
Sep 2, 2003, 6:58 PM
Post #31 of 34
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Registered: Dec 10, 2002
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In reply to: Hear are the correct answers:
In reply to: Since your anchors are not bombproof, and there are only two of them, then choosing a sliding x will serve to direct half the impact force of a fall to each piece, and eliminate the possibility of one piece being subjected to significantly more force than the other.
Wrong again, the sliding x does not "eliminate the possibility of one piece being subjected to significantly more force than the other." i.e., if one of the pieces fails.
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squish
Sep 2, 2003, 7:30 PM
Post #32 of 34
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Registered: Sep 2, 2003
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In reply to: what alpnclmbr1 responded cought me a little off-guard.... how can you have an equalized anchor setup with out the sliding X?. (...) what are those other methods?...
You can have something that is pseudo-equalized. Close is good enough. Really, is it such a big deal if it's 40/60 rather than absolutely 50/50? I would rather take that sliding X and tie a knot in it.
Also a note on angles: If the angle (that the slings between the anchor points create) is narrow, then you are putting less (angular) stress on the anchor points. However, small movements can put slack into one of the pieces, where it wouldn't be holding its share. You have to decide where it's going to be a concern. On a straight up route, no big deal.
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brutusofwyde
Sep 2, 2003, 7:53 PM
Post #33 of 34
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Registered: Nov 3, 2002
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In reply to: what are those other methods?... this has become a great class.....i'm eager to keep learning
Read Climbing Anchors and More Climbing Anchors by John Long.
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mreardon
Sep 6, 2003, 12:11 AM
Post #34 of 34
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Registered: Jun 17, 2002
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In reply to: In reply to: You belay attached to you, and put a piece in above you with the rope clipped through (almost a mini-toprope) which gives no impact to the anchor at all. Anything other is getting ridiculous, and provides more ways to screw up. When belaying the second, you usually have the choice to redirect the belay through a bomber multi-piece set-up, i. e. the belay anchor. Replacing this redundant distributed anchor with a single point above the belay anchor raises the screw-up potential rather than lowering it. The belay now depends on a single piece, whose failure (however unlikely) will subject the second to an honest-to god leader fall (equal to double the distance from belay device to redirection anchor) and load the belayer and belay anchor with a corresponding leader fall sized impact load. This outcome may be unlikely, but if we are counting ways to screw up, this method rates higher than redirecting through the belay anchor.
If the belay is attached to you, then goes up two feet to the piece, then down to the second, that's a whopping four foot potential fall if you completely screw it up and the piece blows. Which if that happens on a belay, don't ever lead because you're likely to die from bad gear placements. But in the end it is still attached to you. Only two total ways to screw it up - dropping the belay device (which should already be attached to you in place before you left the ground) and clipping the rope through a piece of gear. But no matter what, you are still in charge and attached to the second. And even if the piece blew - if you rigged an anchor that can't stand the shock of a whopping four foot fall from a second, you need to take a class on anchor building.
In the end, if the belay device is off of you, and your anchor isn't strong enough to hold a four foot fall, how on earth are you going to hold someone that blows the whole anchor out? You can't, you'd let them fall and die. Even with a crappy anchor you can hip belay and no one gets hurt. Sheesh.
Attaching the second to the anchor and off you puts many more obstacles and screw ups in the way. Everything from dropping the device, to making sure the anchor holds you're equalized, your partner equilized, thereby providing at least seven points of potential screw ups. I'm no math whiz, but I think two is less than seven. :wink:
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