UKC

fully equalised vs asymmetric belays?

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 Pay Attention 26 Jan 2018

Now that forum topics from last year (winter grades) are being recycled is it time for another chance to gather views on fully equalised vs asymmetric belays?

 

Last year I saw a video which seemed to show that a belay with focal point close to one of the two ice screws had much less impact on the *belayer* than when the focal point was midway between the two anchors.

 

I'm danged if I can find that video now!

 

However , I have since preferred to fix up asymmetric belays on this principle, since the idea of full equalisation between anchors seems to be a technical fetish for those with OCD.

 

 

I am, of course, completely open to persuasion by practical reasoning rather than theoretical sophistry.....

2
 Sophie G. 27 Jan 2018
In reply to Pay Attention:

Here's a line of reasoning.

"Suppose you have two points and one will take a load of 7N and the other will take a load of 5N. Now suppose the force of a fall on those points is 8N. Then:

a) if the points are not equalised then the first point that the load hits will take 8N and blow out; the second point that the load hits will take less than that, but if it still takes 6N and it's the weaker of the two points, that's bad enough--the whole belay will go.

b) if the points are equalised then the force of the fall will be 8N and the capacity of the belay will be 12N. So you'll be fine." 

That's a line of reasoning. Is it right or wrong? I'm not a physicist. But I thought this was the line of reasoning that led us to say that we MUST equalise our anchors.

 GridNorth 27 Jan 2018
In reply to Pay Attention:

It's advisable to attempt to equalize anchors but in practice tests have shown it is actualy very difficult to achieve. 

Al

 HeMa 27 Jan 2018
In reply to Sophie G.

> That's a line of reasoning. Is it right or wrong? I'm not a physicist.

It’s correct in theory. 

How ever, on practise a fully equalized anchor is next to impossible to create (If more than 2 pieces). So real world situation might differ greatly. 

 

Edit. Slow.

 

to add, basically the closest thing to a fully equalized anchor is to always connect two pieces/parts-of-the-anchor together with sliding x’s. But even that is not fully equalized If more than 2 pieces due to friction. 

Post edited at 19:01
OP Pay Attention 28 Jan 2018
In reply to Pay Attention:

Thank you SophieG, GridNorth and HeMa for your considered replies.  I appreciate the points you made. 

 

I accept that distributing potential force of impact among all anchors will reduce the potential force on any one anchor.  Realistically, all ice anchors appear equally safe when placed, otherwise you’d replace the weakest one, no?

 

A couple of days ago I had to set a hanging belay on the Spiral of Contingency.  A pair of ice screws were equalised with a quad anchor for the main part of the belay.  By the by, there were three other anchors as back-up.

The problem with the quad anchor is that it is static tape and creates a wide angle when fully deployed.

 

I’m thinking it would be better to set my main two ice screws vertically rather than laterally (as a  vertical A-thread is considered preferable to a lateral V-thread).

 

To reduce belayer movement I’d tie my rope in to a focal point using the lower screw as a fixed anchor.

 

I fond the ACMG fixed point anchor video link I was referring to.  Of course, it’s lateral not vertical, but you’ll get the picture.

At 03:52 it does say: “If the option exists, vertical placement works best”.

vimeo.com/44869774

 

 

 

 Wayne S 28 Jan 2018
In reply to Pay Attention:

You seem to be suggesting symmetry and equalisation are exclusive qualities.  Perhaps I am not understanding the thread?  If you have a high and low piece of gear you can be very much biased towards the lower point, however this does not mean you will not load share with the higher.  

If anchors are bomber with huge headroom (20KN +) such as bolts then being totally anal about equalisation serves little purpose.

I usually equalise via the ropes so, as to introduce a dynamic element to the belay, though appreciate that if not swinging leads you may want to come to a single point belay. 

In those times if I have good confidence in the anchors I usually prefer a sliding x to achieve good equalisation whilst understanding I have no redundancy in the sling element.

If I have low confidence in two bits of gear then it’s time to place more.  Then more effort is needed to ensure equalisation and redundancy.

I am not sure it’s a one statement fits all question.  

Wayne

 Sophie G. 28 Jan 2018
In reply to Wayne S:

> > If I have low confidence in two bits of gear then it’s time to place more.  

 

Gotta love my partner. On our route on Friday he had one *six* point belay. Never seen that before

Post edited at 17:48
 HeMa 28 Jan 2018
In reply to Sophie G.:

I believe my host a few years back on the BMC Winter meet had also a 6 piece stand... including one BD Viper in the crack. And my pitch started with a rather thin, balancy and no-gear start above the big ass roof. This was my third ever route in Scotland.

That said, my stands tend to be 1 to 3 pieces... on good ice, 1 to 2 screws.

 Sophie G. 28 Jan 2018
In reply to HeMa:

Myself I love massive-block belays. Lump the size of a bus, rope threading it, tie off, sorted. I always place a second piece anyway, because them's the rules, but I do like it when I know the second piece is actually just a formality, because that block's not going anywhere without an earthquake or a nuclear war.

But when making a belay, you keep going till your head and your gut both tell you you're safe. 

Post edited at 20:29
 HeMa 28 Jan 2018
In reply to Sophie G.

> But when making a belay, you keep going till your head and your gut both tell you you're safe. 

True, which is why I use one 13cm screw and not a 10cm one.

Or I sling a twig.

 Sophie G. 28 Jan 2018
In reply to HeMa:

Tree belays are a thing in Angus mixed

http://www.scottishwinter.com/?p=6646

Post edited at 23:04

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