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Chockstone Photography
Australian Landscape Photography by Michael Boniwell
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Chockstone Forum - Gear Lust / Lost & Found

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 Page 1 of 2. Messages 1 to 20 | 21 to 26
Author
Sliding X revisited
TimP
27-Jan-2015
11:05:15 AM
I like the sliding X and have been thinking about how to retain its great equalisation.
Post and video clip here:
https://climbdesign.wordpress.com/2015/01/19/sliding-x-revisited/
Dave_S
27-Jan-2015
12:51:01 PM
There was something similar proposed a while back, after the release of John Long's Climbing Anchors 2nd Ed, but as a belay anchor system rather than something for equalising marginal gear placements.

http://www.rockclimbing.com/cgi-bin/forum/gforum.cgi?post=1329483

Personally, I'm not massively keen on the use of the X for protection, just because it's fiddly to set up. If I'm in a position where I'd want two pieces of gear right next to each other (because they were poor placements or I was protecting a crux), then I'd rather have the speed and convenience of just clipping quickdraws and settle for redundancy without perfect equalisation. This way, I'm getting my rope though at least one piece as soon as possible, rather than not being able to clip the rope until the X is set up. (Although you could always clip a quickdraw to one piece, set up the X, and then remove the quickdraw.)

That said, a (redundant) sliding X is my standard anchor for bolts, because there it is very convenient to set up.
kieranl
27-Jan-2015
1:02:50 PM
I can't say that I like the sliding-X in any case and this doesn't improve my view. If your anchor is that marginal you should be rigging your anchor with dynamic rope to minimise impact forces rather than with slings.

phillipivan
27-Jan-2015
1:31:57 PM
I think the main, perhaps only, thing to recommend the sliding x is not it's equalising properties but the ease and speed of set up and break down. It is an anchor configuration I am really only happy to use when I have a high level of confidence in the individual pieces. Adding extra slings, or stopper knots, to prevent extension beyond a certain limit, more or less defeat the only advantage it provides.

BBSR
27-Jan-2015
4:54:19 PM
I read through these in detail a while back. There was another option called 'the quad' or something which seemed like another option, as long as you don't mind carrying a bit more cord...
Dave_S
27-Jan-2015
5:00:24 PM
Yeah, the "Quad" was advocated by John Long for belaying off bolts, though I'm not convinced that it's worthwhile carrying a piece of equipment whose only purpose is for belaying off bolts. It consisted of a dyneema sling or tied loop, folded in half, and then having permanent limiter knots tied in it, such that there are four strands between the limiter knots. You'd then clip in to two or three of these strands.

http://www.mountainproject.com/images/92/1/107359201_medium_9ff536.jpg
Wendy
27-Jan-2015
8:19:25 PM
I'm with Kieran in the non-fan field. If your anchor is bodgy - put in more than 2 pieces for starters! 6 bodgy pieces equalised with a knotted off cordelette or similar with the rope, whilst not perfectly equalised, are still better than 2 bodgy pieces with a sliding x even if it is backed up with slings where if a piece fails, there's more movement onto the remaining piece than in a knotted equalised system. And if you are bothering to set up the other slings, it's going to be quicker and simpler to just use a cordellette to rig. Really, would you set up a series of these backed up xes in a real anchor situation of 3-4? and then do you have to run more sliding xes down from each until you get to a centralised anchor point? Isn't it just getting carried away about very little?

I don't even like sliding x on 2 bolts - even if you accept that each individual bolt is bombproof, which for lots of bolts, I wouldn't, you still have 1 sling in the system. If the sling fails, the whole belay is gone. I like redundancy.

It's not that hard to clip your sling into the 2 bolts, slide it around a bit to find the most likely direction of pull, chuck in an 8 or overhand there, double check the loading when you weight it and have 2 independant really bloody close to perfectly equalised legs. Presumably most of us manage a similar exercise on 3-4 pieces of trad gear on a regular basis. When was the last time you saw a reasonably well equalised knotted system fail from a cascade started by one piece failing? I'd be much more worried about the single sling with nylon on nylon movement built into the system.

as a sideline, I was chatting with someone at dinner last night who was saying that the recommendations on sling replacement these days are way lower than I thought - that for spectra in particular, if you are climbing regularly on it, there is suficient sun exposure in only 3 years to warrant retiring it. I'm not sure that any of my slings are actually less than 3 years old. So that single sling may be even more of a concern.
Jayford4321
27-Jan-2015
9:39:28 PM
On 27/01/2015 Wendy wrote:
>I'm with Kieran in the non-fan field. If your anchor is bodgy - put in
>more than 2 pieces for starters! 6 bodgy pieces equalised with a knotted
>off cordelette or similar with the rope, whilst not perfectly equalised,
>are still better than 2 bodgy pieces with a sliding x even if it is backed
>up with slings where if a piece fails, there's more movement onto the remaining
>piece than in a knotted equalised system. And if you are bothering to set
>up the other slings, it's going to be quicker and simpler to just use a
>cordellette to rig. Really, would you set up a series of these backed up
>xes in a real anchor situation of 3-4? and then do you have to run more
>sliding xes down from each until you get to a centralised anchor point?
>Isn't it just getting carried away about very little?
>
>I don't even like sliding x on 2 bolts - even if you accept that each
>individual bolt is bombproof, which for lots of bolts, I wouldn't, you
>still have 1 sling in the system. If the sling fails, the whole belay is
>gone. I like redundancy.
>
>It's not that hard to clip your sling into the 2 bolts, slide it around
>a bit to find the most likely direction of pull, chuck in an 8 or overhand
>there, double check the loading when you weight it and have 2 independant
>really bloody close to perfectly equalised legs. Presumably most of us
>manage a similar exercise on 3-4 pieces of trad gear on a regular basis.
>When was the last time you saw a reasonably well equalised knotted system
>fail from a cascade started by one piece failing? I'd be much more worried
>about the single sling with nylon on nylon movement built into the system.
>
>as a sideline, I was chatting with someone at dinner last night who was
>saying that the recommendations on sling replacement these days are way
>lower than I thought - that for spectra in particular, if you are climbing
>regularly on it, there is suficient sun exposure in only 3 years to warrant
>retiring it. I'm not sure that any of my slings are actually less than
>3 years old. So that single sling may be even more of a concern.
>
>
Hey Wen, I have a packet of teeth floss that I acidentally left on the dash of the car exposed to huge heat and sunlight through the glass. I later noticed their use by date was faded.
Do you think they are still ok to use?
If not, what about if I double them up?
Am I getting carried way about very little?

Last time I saw a belay cascade fail, everyone involved thought that a strong possibility due the obvious shit placements involved.
Knowing this they put more double ups in.
The amazing thing was that even though two legs of the cordelette failed, the third and seemingly most unlikely anchor piece, held.

Sliding X's in original concept for trad are plenty ok for most situations, and nearly all situations with an extension limiting knot incorporated.
They are a wank on bolts.

Getting carried away is the armchair critics perogative.
Dave_S
27-Jan-2015
9:50:49 PM
On 27/01/2015 Wendy wrote:
>
>I don't even like sliding x on 2 bolts - even if you accept that each
>individual bolt is bombproof, which for lots of bolts, I wouldn't, you
>still have 1 sling in the system. If the sling fails, the whole belay is
>gone. I like redundancy.

Definitely agree that any anchor that will fail completely if a single sling fails is inadequate. That's why I use two slings to make a sliding X for bolted belays.
One Day Hero
28-Jan-2015
12:20:20 AM
On 27/01/2015 Dave_S wrote:
>Definitely agree that any anchor that will fail completely if a single
>sling fails is inadequate. That's why I use two slings to make a sliding
>X for bolted belays.

Do you also make sure to double up your belay device, carabiner, harness, and rope?
patto
28-Jan-2015
1:17:52 AM
My slings, belay device, carabiner, harness and rope are all rated and CE certified. So they don't need doubling up.

My belayer however isn't rated. I double up on my belayers.
Wendy
28-Jan-2015
8:13:07 AM
On 27/01/2015 gnaguts wrote:


>>
>Hey Wen, I have a packet of teeth floss that I acidentally left on the
>dash of the car exposed to huge heat and sunlight through the glass. I
>later noticed their use by date was faded.
>Do you think they are still ok to use?
>If not, what about if I double them up?
>Am I getting carried way about very little?

Depends on if you kept a log book. If you didn't, they are definitely not safe for use on teeth. You should retire them to fingernail cleaning.
>
I keep a log book on my belayers. That way I don't need to double them up.

Seriously though, whilst there are a few single pieces in the system, why choose to add more to the system, especially in a configuration that is going to provide nylon on nylon friction? We all agree you don't run a rope through slings because of that. In the course of self equalising, a sliding x has constant small amounts of movement and if one fails, a slide along half the length of the sling rubbing on itself. I just don't see that the slight improvement in equalisation is worth the weakening of the system overall. And I am fussy about my harness and rope as well, but they are designed and recommended for use by themselves, although we have seen what can happen when these single points fail.
>
gfdonc
28-Jan-2015
9:14:00 AM
A sliding X will ensure both pieces are weighted equally regardless of which direction the load comes from. Sometimes it's hard to accurately predict this, and tying a cordalette locks you in to a particular arrangement.
When/if I use a sliding X I tie off the lead rope as a backup anyway.
I'll concede, where paranoia rules I tend to tie off the cordalette.
YMMV.
kieranl
28-Jan-2015
9:43:22 AM
On 28/01/2015 gfdonc wrote:
>A sliding X will ensure both pieces are weighted equally regardless of
>which direction the load comes from. Sometimes it's hard to accurately
>predict this, and tying a cordalette locks you in to a particular arrangement.
>When/if I use a sliding X I tie off the lead rope as a backup anyway.
>I'll concede, where paranoia rules I tend to tie off the cordalette.
>YMMV.

No the sliding X does not ensure that both pieces are weighted equally - it ensures that both pieces are kept in tension. The force on each piece will be equal only when the ttie-in point is centred between the two anchors. If that point shifts more force will be applied to the leg which has just been shortened somewhat. It's basic rigging physics, change the angle, change the forces (a diagram would explain this better).

Also, if there is a shock load off the anticipated line of force, the transition to the new orientation isn't instantaneous, momentarily one side of the anchor will take a hit until the krab moves to the new alignment.

* edited for (hopefully) clariity

IdratherbeclimbingM9
28-Jan-2015
9:55:55 AM
Re cascade failures and sliding-X's vs cordelette's.

~> Old memory fading now as I have followed the sliding X thing since concept inception, though quite a while afterwards I recall hearing something along the lines of testing being done of cordeletts (Info from Phil Box), that confirmed anything outside of 5° of alignment (anchor - loadpoint - load), pretty much loads up the extra protection pieces fully, such that there is very little effective load sharing. This is not always obvious, particularly when the system is under load and things appear to be tensioned.

In my experience for most belay constructs it is reasonably straightforward to anticipate general loading direction/s, and I like the load limited knot version of a sliding-X to cover a bit of variance if I get that wrong, as 5° isn't much...

For trad (and aid), I use a spectra cordelette sliding-X system with pre-tied load limiting knots quite close* to the load point. This limits the range of slide-X load variance, but as I mentioned above I reckon I can anticipate that, and only require the fine tuned bit to negate the '5° effect'.

(*Knots are about 200 mm either side of load point).

gnaguts, re sliding X's being a wank on bolts; for most applications I agree, though in my experience the sliding-X truly comes into it's own for bolts when hauling heavy haulbags (or I guess, people in a rescue situation), particularly if the haul has any diagonal component to it, which can come about due a haulbag snagging on cliff features.

IdratherbeclimbingM9
28-Jan-2015
10:23:08 AM
On 28/01/2015 kieranl wrote:
>On 28/01/2015 gfdonc wrote:
>>A sliding X will ensure both pieces are weighted equally regardless of
>>which direction the load comes from. (snip)
>
>No the sliding X does not ensure that both pieces are weighted equally
>- it ensures that both pieces are kept in tension. The force on each piece
>will be equal only when the ttie-in point is centred between the two anchors.
>If that point shifts more force will be applied to the leg which has just
>been shortened somewhat. It's basic rigging physics, change the angle,
>change the forces (a diagram would explain this better).
>
>Also, if there is a shock load off the anticipated line of force, the
>transition to the new orientation isn't instantaneous, momentarily one
>side of the anchor will take a hit until the krab moves to the new alignment.
>
>* edited for (hopefully) clariity

?, ... although I see your point (key word being 'centred'), especially for transition loadings, but for practical* climbing anchor purposes, the loading is still better distributed with a sliding-X than if relatively static by comparison (tied off), cordelette legs are involved.
I suspect any dynamic elements of belay system rigs are small bikkies compared to what is going on with the lead rope / protection enroute / belay device etc.

(* A belay can be over engineered for the need it is likely to have to meet!).
patto
28-Jan-2015
10:42:25 AM
On 28/01/2015 kieranl wrote:
>No the sliding X does not ensure that both pieces are weighted equally
>- it ensures that both pieces are kept in tension. The force on each piece
>will be equal only when the ttie-in point is centred between the two anchors.
>If that point shifts more force will be applied to the leg which has just
>been shortened somewhat. It's basic rigging physics, change the angle,
>change the forces (a diagram would explain this better).

HUH??

"Basic rigging physics" for the sliding-x is equal tension on all legs and equal tension on the two pieces no matter what the angle and position of load. Any unequal leg tension would be cause sliding of sling until tension is equalised.

Of course stepping away from basic rigging physics and you have friction on the karabiners and the x itself. This friction limits the extent of movement and complete equalisation doesn't occur.
Dave_S
28-Jan-2015
11:07:02 AM
On 28/01/2015 One Day Hero wrote:
>
>Do you also make sure to double up your belay device, carabiner, harness,
>and rope?

Nope. Ropes and harnesses are much, much more reliable than slings due to their having protection against wear built-in. I've never even heard of a harness failure ever occurring. (Opening scene of Cliffhanger does not count.) Ditto for belay device and belay carabiner, which additionally are not susceptible to damage from chemical exposure, UV exposure, or being weakened by small cuts.

Additionally, the fact that redundancy is not practical in every single piece of equipment you use is not a reason to forego redundancy when it would have been practicalto have it.


On 28/01/2015 Wendy wrote:
>
>Seriously though, whilst there are a few single pieces in the system,
>why choose to add more to the system, especially in a configuration that
>is going to provide nylon on nylon friction? We all agree you don't run
>a rope through slings because of that. In the course of self equalising,
>a sliding x has constant small amounts of movement and if one fails, a
>slide along half the length of the sling rubbing on itself.

Definitely agree with the point on redundancy, but fabric-on-fabric friction is only a problem when one piece of fabric is moving and the other isn't, at when this happens the heat all concentrates in one spot on the non-moving strand and melts it. When both strands are moving against each other, as in a sliding-X, the heat generated is distributed across the length of the sling, and doesn't cause melting. This is the same reason why a Munter hitch won't melt your rope.


On 28/01/2015 kieranl wrote:
>
>No the sliding X does not ensure that both pieces are weighted equally
>- it ensures that both pieces are kept in tension. The force on each piece
>will be equal only when the ttie-in point is centred between the two anchors.
>If that point shifts more force will be applied to the leg which has just
>been shortened somewhat. It's basic rigging physics, change the angle,
>change the forces (a diagram would explain this better).
>
>Also, if there is a shock load off the anticipated line of force, the
>transition to the new orientation isn't instantaneous, momentarily one
>side of the anchor will take a hit until the krab moves to the new alignment.

Incorrect. The only degree to which magnitude of load on the anchors can differ with a sliding-X is due to friction between the carabiner and sling, which is negligible in comparison with the load force. The carabiner simply cannot exert force on one end of the sling more than the other, which would be required in order for different magnitudes of force to be placed on the anchors. The only way in which forces on the anchors can differ is in direction.

Even in shock loading or sudden change of direction, forces on the anchors are equal, but the system is not in equilibrium because the is a net sidewards force applied to the carabiner, which causes it to shift until the system is balanced.

(And if you cite the DMM article which incorrectly makes this claim that anchor loads are not balanced in a sliding-X I will be forced to put my face through my desk and then start drawing free body diagrams!)

shortman
28-Jan-2015
11:22:30 AM
On 28/01/2015 Dave_S wrote:

>the sling, and doesn't cause melting. This is the same reason why a Munter
>hitch won't melt your rope.
>
Actually it can and does still melt, just not to the point of failure. Hence why webbing and rope can be a bit glazed/scorched.

>(And if you cite the DMM article which incorrectly makes this claim that
>anchor loads are not balanced in a sliding-X I will be forced to put my
>face through my desk and then start drawing free body diagrams!)

Please oh please cite the article Kieran, :)
gfdonc
28-Jan-2015
11:51:36 AM
On 28/01/2015 Dave_S wrote:
>Nope. Ropes and harnesses are much, much more reliable than slings due
>to their having protection against wear built-in. I've never even heard
>of a harness failure ever occurring.

Google "Todd Skinner".

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