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To pre-equalize or not?
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adkeditor


May 5, 2014, 4:44 PM
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To pre-equalize or not?
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For the sake of argument, let's say you build a belay anchor with two solid pieces of pro. The sliding X will distribute the force of a leader fall between them, but if a piece blows, the other may be shock loaded. Using a figure 8 to pre-equalize solves that problem, but if the force comes from an unexpected direction, all the force may be absorbed by one piece.

I understand that you can mitigate the risk with limiter knots and that situations differ, but I'd like to know which, as a general rule, is the safer setup.

Common sense suggests that a shock load would not be as great as the force of a leader fall, so the sliding X is safer. On the other hand, if the shock load is absorbed by your one remaining anchor, that is scary.

Would the answer to my question be any different if you have three pieces of pro?


patto


May 5, 2014, 10:45 PM
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Re: [adkeditor] To pre-equalize or not? [In reply to]
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Now that is a can-of-worms....

http://www.rockclimbing.com/...rum.cgi?post=1306133

Shock loading is bad and should be avoided at all costs. An anchor moving an readjusting an extending is bad and introduce problems such as loss of control of belay.

Having the force of a second fall on only one piece is no issue at all. Pieces generally don't fail because of excess load they fail from poor placements.


So stay away from the sliding-x unless you need to equalise two pieces of marginal pro. (ie RPs and other <5kN pieces)


(This post was edited by patto on May 5, 2014, 10:45 PM)


tomcecil


May 6, 2014, 5:37 AM
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Re: [adkeditor] To pre-equalize or not? [In reply to]
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you can set the pieces to "pre-align" but could never "equalize" the pieces and should not think you can, testing has shown wildly different forces on "equalized" legs in self-equalizing anchor set ups, this is caused by plowing and uneven legs. Solid primary pieces are your only defense against ripping your anchor out of the wall in a fall. Do not waste your time believing you can somehow increase the holding power of your anchor with some fancy trick or through "equalization".--Practice placing gear and learn to back down if you cannot find a solid anchor.


(This post was edited by tomcecil on May 6, 2014, 5:45 AM)


dagibbs


May 6, 2014, 7:44 AM
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Re: [adkeditor] To pre-equalize or not? [In reply to]
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Equalization, in practice, almost never actually happens. In an anchor you want redundancy, no extension, and no force multiplication. I tend towards an overhand, rather than a figure-8 to make my power-point, unless I want to shorten up the slings for position.


JimTitt


May 6, 2014, 9:06 AM
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Re: [adkeditor] To pre-equalize or not? [In reply to]
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First, with two solid pieces of pro one doesnīt blow, by definition it wasnīt solid.
Second. the guys above have it right, bin the equalisation and go for redundancy without extension. And get pieces in that really are solid, not maybe.


socalclimber


May 6, 2014, 10:34 PM
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Re: [adkeditor] To pre-equalize or not? [In reply to]
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Jim is spot on. The biggest problem with new climbers these days is they are trying to complicate simple systems.

Keep it simple.


adkeditor


May 7, 2014, 7:25 AM
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Re: [socalclimber] To pre-equalize or not? [In reply to]
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Thanks for the replies. I am not trying to complicate things. I too like simplicity, and my question is a simple one: I want to know whether, on balance, a sliding X or a pre-aligned anchor is safer. Is this an unsettled question? I agree that it's more important to build solid anchor points than fret about the rigging. Still, the question remains: Which rigging is more secure if the anchor points are less than ideal, because of either incompetence or lack of good cracks?


marc801


May 7, 2014, 9:07 AM
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Re: [adkeditor] To pre-equalize or not? [In reply to]
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adkeditor wrote:
I am not trying to complicate things. I too like simplicity, and my question is a simple one: I want to know whether, on balance, a sliding X or a pre-aligned anchor is safer. Is this an unsettled question?
You've already been supplied with the "simple" answer - read all 37 pages of the link Patto supplied upthread. That's easier for everyone involved than rehashing it yet again.


rocknice2


May 7, 2014, 9:48 AM
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Re: [adkeditor] To pre-equalize or not? [In reply to]
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adkeditor wrote:
Thanks for the replies. I am not trying to complicate things. I too like simplicity, and my question is a simple one: I want to know whether, on balance, a sliding X or a pre-aligned anchor is safer. Is this an unsettled question? I agree that it's more important to build solid anchor points than fret about the rigging. Still, the question remains: Which rigging is more secure if the anchor points are less than ideal, because of either incompetence or lack of good cracks?

Simple answer is don't belay off a manky anchor. Definitely don't belay of a 2 piece manky anchor.

This has been debated to death. There are as many opinions as assholes.
Since there are so many variables it's probably impossible to answer the question.
The short answer is build solid anchors and they will hold regardless of which system you use.


JimTitt


May 7, 2014, 10:16 AM
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Re: [adkeditor] To pre-equalize or not? [In reply to]
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adkeditor wrote:
Thanks for the replies. I am not trying to complicate things. I too like simplicity, and my question is a simple one: I want to know whether, on balance, a sliding X or a pre-aligned anchor is safer. Is this an unsettled question? I agree that it's more important to build solid anchor points than fret about the rigging. Still, the question remains: Which rigging is more secure if the anchor points are less than ideal, because of either incompetence or lack of good cracks?

It depends is the answer. It depends on the orientation of the pieces (vertical a sliding X is better at load distribution because you can allow for angular movement with the limiter knots extremely close together, horizontal they have to be so far apart that shock loading the remaining piece is a real concern.
It depends if the load is going to be applied vertically or horizontally (leader traverses, places a piece and then falls).
It depends if you are hanging the weight of the belayer, the entire party on the anchor or just top-roping through it.
And so on.
Of the two choices the fixed anchor is overall going to give you a better chance of survival if pieces of the anchor start failing. If they donīt fail it doesnīt matter how you tie to them.


dagibbs


May 7, 2014, 10:32 AM
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Re: [JimTitt] To pre-equalize or not? [In reply to]
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JimTitt wrote:

Of the two choices the fixed anchor is overall going to give you a better chance of survival if pieces of the anchor start failing. If they donīt fail it doesnīt matter how you tie to them.

There's the simple answer. Again. Same as you had up-thread.


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