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Personal belay anchor in alpine environment
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majid_sabet


Feb 10, 2010, 3:21 PM
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Personal belay anchor in alpine environment
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So I am reading this 155 page long mountaineering manual that suppose to teach beginners on how to climb and section of this book talks about setting up anchors in the snow and ice. Here (not sure where this place is) a guy uses an ice axe or some form snow or ice tool as his main anchor but then redirect the belay to his partner.

Now, why 2+2 is turning to 5 in here ?

if his partner falls or something happens where he has to load the anchor, technically, his fall is going to generate somewhere between 1.25 x to max of 2x of the falling forces on the anchor due to use of his redirect.

is this anchor setup a common practice in alpine and ice ?

The source of information on this foreign educational manual comes from Jeff lowe, Freedom of the Hills and few other well known books but I have not had a chance to do cross references to see where this image came from and why.


http://www.use.com/ea03a86514358a366f84


colatownkid


Feb 10, 2010, 3:37 PM
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Re: [majid_sabet] Personal belay anchor in alpine environment [In reply to]
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majid_sabet wrote:
So I am reading this 155 page long mountaineering manual that suppose to teach beginners on how to climb and section of this book talks about setting up anchors in the snow and ice. Here (not sure where this place is) a guy uses an ice axe or some form snow or ice tool as his main anchor but then redirect the belay to his partner.

Now, why 2+2 is turning to 5 in here ?

if his partner falls or something happens where he has to load the anchor, technically, his fall is going to generate somewhere between 1.25 x to max of 2x of the falling forces on the anchor due to use of his redirect.

is this anchor setup a common practice in alpine and ice ?

The source of information on this foreign educational manual comes from Jeff lowe, Freedom of the Hills and few other well known books but I have not had a chance to do cross references to see where this image came from and why.


http://www.use.com/ea03a86514358a366f84

are you proposing that he instead belay directly off the anchor? or perhaps directly off his harness?

also, we lack context.

we don't actually know how that anchor is built. we also don't know the purpose of that belay. what is the terrain like? how serious are the consequences of a fall? what is the likelihood of a fall?

i'm certainly not an expert on snow anchors, but i'm not sure i'm ready to jump to conclusions yet.


Adk


Feb 10, 2010, 4:04 PM
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Re: [majid_sabet] Personal belay anchor in alpine environment [In reply to]
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Majid,

You know as well as I, just because it's written does not mean it is the best thing nor the smartest thing to do.
Look at the cordelette testing for example. Once thought as the best rig anyone could ever want to connect to an anchor. Yes, I still continue to use it.Wink
Not everyone has a clue on forces applied to anchors.


JimTitt


Feb 11, 2010, 3:05 AM
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Re: [majid_sabet] Personal belay anchor in alpine environment [In reply to]
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Itīs called a slingshot belay.
"if his partner falls or something happens where he has to load the anchor, technically, his fall is going to generate somewhere between 1.25 x to max of 2x of the falling forces on the anchor due to use of his redirect."
Personally I think the maximum force imposed on the belay will be roughly twice the weight of the lower climber and others appear to share my opinion.


builttospill


Feb 11, 2010, 6:42 AM
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Re: [majid_sabet] Personal belay anchor in alpine environment [In reply to]
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Is your concern the use of the ice axe/tool as the anchor point, or the rigging itself?


dan2see


Feb 11, 2010, 7:31 AM
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Re: [majid_sabet] Personal belay anchor in alpine environment [In reply to]
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A picture is worth a thousand words.

Half a picture is wo



(edit for clarity)


.


(This post was edited by dan2see on Feb 11, 2010, 7:32 AM)


lemon_boy


Feb 11, 2010, 7:54 AM
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Re: [JimTitt] Personal belay anchor in alpine environment [In reply to]
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JimTitt wrote:
Itīs called a slingshot belay.
"if his partner falls or something happens where he has to load the anchor, technically, his fall is going to generate somewhere between 1.25 x to max of 2x of the falling forces on the anchor due to use of his redirect."
Personally I think the maximum force imposed on the belay will be roughly twice the weight of the lower climber and others appear to share my opinion.


actually, the final at-rest force on the anchor would be close to twice the weight of the climber, minus a bit for friction on the biner. the peak force on the anchor will actually be close to 4 times the weight of the climber.


(This post was edited by lemon_boy on Feb 11, 2010, 7:56 AM)


JimTitt


Feb 11, 2010, 8:43 AM
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Re: [lemon_boy] Personal belay anchor in alpine environment [In reply to]
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On a snow slope that soft and that angle, youīre kidding surely?


shoo


Feb 11, 2010, 8:44 AM
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Re: [lemon_boy] Personal belay anchor in alpine environment [In reply to]
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lemon_boy wrote:
JimTitt wrote:
Itīs called a slingshot belay.
"if his partner falls or something happens where he has to load the anchor, technically, his fall is going to generate somewhere between 1.25 x to max of 2x of the falling forces on the anchor due to use of his redirect."
Personally I think the maximum force imposed on the belay will be roughly twice the weight of the lower climber and others appear to share my opinion.


actually, the final at-rest force on the anchor would be close to twice the weight of the climber, minus a bit for friction on the biner. the peak force on the anchor will actually be close to 4 times the weight of the climber.

Uuuuuuh, no.

In order for what you just stated to be true, you would have to assume all of the following:

1. The force, as experienced by the climber, is 2x his/her body weight AND the belayer is anchored to a second, perfectly static anchor and perfectly static catch in an opposing direction to the first anchor. This is obviously an absurd scenario to start with, not to mention how you somehow came up with the 2x body weight force of fall.

2. This is all occurring on perfectly vertical terrain, with a perfectly vertical free fall, and a hanging belay. When was the last time you saw someone sink a deadman anchor hanging off a sheer cliff? Oh, right, never.

Before you even say it, in typical crevasse rescue, the belayer has already caught the fall before an anchor is constructed. The fallen climber then either ascends the rope or is hauled, each putting approx 1x climber's weight on the anchor (assuming 0 friction from the rope on the snow / ice and perfectly vertical terrain).

Even in the case where the climber actually climbs out of the crevasse on belay, the rope running over the edge of the crevasse will add a lot of friction to the system.

Edited: Yeah, what Jim said.


(This post was edited by shoo on Feb 11, 2010, 8:45 AM)


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