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 Page 1 of 5. Messages 1 to 20 | 21 to 40 | 41 to 60 | 61 to 80 | 81 to 98
Author
SRENE anchors may go the way of the dinosaur

Phil Box
7/03/2006
12:56:30 PM
The Sliding X thread over on rc.com may be one of the most useful discussions to ever come out of the internet as far as climbing goes. John Long has put many posts into that thread and he discusses recent testing on the powerpoint cordalette and webolette.

The upshot is that these anchor setups for trad climbing may not be the set up that is best. The discussion so far indicates that the improved sliding x may be the way of the future. The test results indicate that extension may not be the evil thing that it was thought. If one leg of a sliding x goes then yes there will be a small amount of extension but the transferred load is not that great.

So SRENE anchors are now being explored to gain a greater understanding of the dynamic nature of the forces applied to them under the load of a falling climber.

I shall also flag that there is a deal of local experimentaion about to be undertaken on this subject, more to come when that is undertaken more fully. Preliminary results indicate that there is a huge amount of new data that will become available that will be extremely useful in the inevitable anchor debates that will occur now that the subject is needing to be reexamined.

If anyone has some sort of tricky and easily set up anchor system that offers complete equalisation then I strongly suggest heading over to the thread on rc.com quoted above and state your case.

Note that rc.com has been experiencing a very slow load rate so if you get a slow page load then check back when all the yanks are asleep.
gfdonc
7/03/2006
2:52:36 PM
What page has got the interesting data? Seems to be pages of uneducated waffle. The early posting - that someone has put together a book on this - lacks any hard data and only hints at the conclusion.
JamieF
7/03/2006
3:48:25 PM
On 7/03/2006 gfdonc wrote:
>What page has got the interesting data? Seems to be pages of uneducated
>waffle. The early posting - that someone has put together a book on this
>- lacks any hard data and only hints at the conclusion.

Well who would buy the new version of the book if the hinted at information was online for free?

Phil Box
7/03/2006
5:48:44 PM
Yeah it is a huge thread but definitely worth trawling through for the gems.

Chalk Free
7/03/2006
6:08:31 PM
On 7/03/2006 Phil Box wrote:
>Yeah it is a huge thread but definitely worth trawling through for the
>gems.

Sure but how does the novice cut through the crap. Take clove hitches for example, reading some of the posts would suggest that if you use them your belay will fail. Not only have I use them without incident in 20 years climbing. We use them when waterskiing to even up the lengths of ropes and have never had one slip.
gfdonc
7/03/2006
8:36:08 PM
Clove hitches. Hmphh. Another death-knot used by alpine climbers.
;-)
kieranl
7/03/2006
10:06:03 PM
Pardon my ignorance, but what are SRENE anchors and what is the sliding-X?

tmarsh
7/03/2006
10:31:01 PM
SRENE = solid, redundant, equalised, no extension

The classic SRENE anchor would be 3 pieces, equalised with a cordolette in a fashion that should one piece fail, there would be no resulting shock loading on the remaining pieces.

The sliding X is two pieces (or two groups of pieces), with a long sling between them, with a half-twist on one of the strands of the sling and a biner clipped though the resulting loop and over the other strand. hard to describe, but very simple in practice. Think of the sort of set-up you would use to set up a top-rope for a meandering route.

The sliding X has the benefit that it dyamically equalises itself and ensures the load is always shared between the two groups of pro, but has the drawback that should one of those groups fail, it will extend itself to the full length of the sling and possibly shockload the remaining piece.

SRENE was a concept promulgated by John Long in his book 'Climbing Anchors'. While I'm not surprised to hear that it's not the be-all and end-all in anchor systems, it's not a bad way to look at how to set up anchors. It's a simple system which, if followed, will maximise the effectiveness of the available placements most of the time. I have no doubt that there are other approaches that will be better in some circumstances. It's kind of like arguing that a double bowline is better than a figure-8. It might be in some situations, but the figure-8 is still good enough, reliable and easy to do under adverse circumstances. ie, it's not a bad practical solution.

shmalec
8/03/2006
12:45:02 PM
Thread looks like a good way to waste your entire lunch hour.
how many recorded instances of failed 3 piece cordolette anchors have we come across?
The main weakness of the cordolette is shifting from belaying from above to belaying from below when multipitching. In this instance you (should) have the belayer's weight to take much of the load anyway.

ampedandwired
8/03/2006
1:18:13 PM
>how many recorded instances of failed 3 piece cordolette anchors have
>we come across?

Probably very few, if any. But then how many anchors are put to the test with high factor falls? I'd like to think that if I had to catch a factor 2 sometime my anchor would be up to the job. If the best available evidence suggests that the cordelette is a bad choice for this (which seems to be what JL is indicating is coming out of his testing results), then I think its maybe worth paying attention.


Phil Box
8/03/2006
1:38:33 PM
There have been instances of cascade failure of these types of anchors. There was an accident at Tarquitz that exhibited this failure mode. What happens is that the anchor is not perfectly equalised and the load goes on to one arm only, it fails and the load is transferred to another arm and it fails and then the load is transferred to the remaining arm. A perfectly equalising anchor would transfer the load to all three arms. Thus the load is divided by three which may mean that the dodgy piece may now hold.

We may be concentrating on no extension at the expense of equalisation. No extension may not be the huge evil scary thing it has been purported to be. The equalisation factor on the other hand may in fact be the more important thing to get right. It seems that one can get one or the other but not both. The debate leans towards erring towards equalisation over no extension. A small amount of extension does not necessarily equate to a huge amount of extra load on an anchor.
NEVERCLIMBED32
8/03/2006
2:07:21 PM
On 7/03/2006 tmarsh wrote:

The sliding X ........................ has the drawback that should one of those groups fail, it will extend itself to the full length of the sling and possibly shockload the remaining piece.

Of course this would never happen because you would have tied off your sling above the X. While this has the effect of minimising your mobility while attached to the anchor the point of the exercise is after all,...........equalising the anchor. Tieing off you sling in this way means minimal extension and shock loading of the anchor. You may tie off one or both sides depending on how marginal they are. Personally I choose the sliding X over the cordolette as I find it easier to equalise.

Phil Box
8/03/2006
4:13:40 PM
NEVERCLIMBED32 gets it.

anthonyk
8/03/2006
4:37:32 PM
On 8/03/2006 NEVERCLIMBED32 wrote:
>Of course this would never happen because you would have tied off your
>sling above the X. .. You may tie off one or both sides depending
>on how marginal they are.

does that involve a) equalise while sliding and hold equalised loop fixed b) unclip each piece in turn to tie a knot in it. ? (of course tying a knot in the whole thing above the X would make a SRENE anchor)

i suppose that helps give a bit of redundancy to the sling itself, one of the dodgy things about sliding X's is if the anchor sling is running over an edge or something or has risk of being abraded/cut there is no redundancy, if it breaks anywhere the whole thing fails. but i'm sure this is all covered ad nauseum in the other thread.

tmarsh
8/03/2006
5:37:25 PM
On 8/03/2006 anthonyk wrote:
>i suppose that helps give a bit of redundancy to the sling itself, one
>of the dodgy things about sliding X's is if the anchor sling is running
>over an edge or something or has risk of being abraded/cut there is no
>redundancy, if it breaks anywhere the whole thing fails. but i'm sure
>this is all covered ad nauseum in the other thread.

You can always use more than one sling and equalise it as you would the first one. I climb most often on double ropes and will often have a two-piece anchor equalised with a sliding-x on each rope. Can't get much more redundant or equalised than that.

The good Dr
8/03/2006
5:52:15 PM
Try putting two munter hitches in the sliding X as opposed to the loop only. It can equalize, though not as easily, and will slide on the chord in an anchor failure rather than a severe shock load.

anthonyk
8/03/2006
6:27:19 PM
On 8/03/2006 The good Dr wrote:
>Try putting two munter hitches in the sliding X as opposed to the loop
>only. It can equalize, though not as easily, and will slide on the chord
>in an anchor failure rather than a severe shock load.

well equalising slowly seems to miss the whole point to me, it won't distribute the force of the fall evenly & one of the pieces will take the bulk of the load. i don't think you can put something that equalises slowly as a benefit against shocking the second piece AND a benefit in equalising the force in the first place, i'd say they're mutually exclusive.
gfdonc
9/03/2006
10:35:59 AM
I sense a poll coming up .. stay tuned.
uwhp510
9/03/2006
2:27:01 PM
Holy shit welcome to bandwagon land (at rc.com)

its all "I totally never trusted cord-o-lettes and look how smart I look now".

Having said that, I never owned a cord-o-lette because I couldn't be bothered carrying the sucka(s). I don't often use sliding x's either though.


shmalec
9/03/2006
5:42:55 PM
given that the rope must have stretched a fair bit to develope enough load to fail one of your pieces, the "shock" load would not be a shock load in the normal sense of energy absorbtion of a falling weight. I expect the rope would retract when the anchor extends, load up the next piece in the anchor, followed by a second small drop by the climber. So from that point of view, I don't think the shock loading issue is all that big. What I don't like about the sliding X is that you are reliant on only one sling and 2 pieces. It is also easy to mess up the twist if you're not careful with it. I also find that if you are careful with the cordollete direction you can get pretty good equalisation.
Someone needs to invent a reasonably high strength low stiffness anchor chord and all this would be simple.

 Page 1 of 5. Messages 1 to 20 | 21 to 40 | 41 to 60 | 61 to 80 | 81 to 98
There are 98 messages in this topic.

 

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