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pjcozzi
Dec 2, 2005, 6:12 PM
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In reply to: When he says "not long enough" he means not long enough that the angles between pieces is acceptable.
Exactly. Thanks for clearing that up.
Patrick
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el_jerko
Dec 2, 2005, 6:18 PM
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My $.02
I use the sliding knot under two circumstances; very good placements, and very bad.
With a couple of bolts the issue of extension is diminished and the scale tips toward equalization.
With very bad placements equalization once again becomes a priority in my mind and I will connect sketchy placements via the sliding X and then tie that into the rest of a static achor.
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bill413
Dec 2, 2005, 6:29 PM
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Nowadays, I most frequently use the sliding-X to equalize "sub-components" of an anchor that will then form one leg for my cordelette. (e.g. I've got 4 pieces in, equalize two with a sliding-x, join it's power point to the other two pieces with the cordellette, giving me 3 legs). It's quick, I don't have to worry about getting the direction of pull exactly right for that subsystem. It avoids having 4 arms in the cordellete...
I also use it on intermediate pro to share the load among two pieces when both (or at least one) is questionable.
The problem is, as has been noted, with the lack of redundency - having only one sling. On running pro, we usually only have one sling anyway, so I accept that. When I'm using it in an anchor, I make sure that there is not just one critical sling.
I'm surprised at the people who won't use the x for manky pro - in my mind, that's the place where you want it, to try & reduce the initial loading of the por pro, and share the load, as equally as possible. Yes, extension may be a problem, but the first issue is to try & distribute the load (or else either the piece is bomber, so you don't need to distribute load, or it is so bad you shouldn't be loading it anyway).
John - thanks for letting us have input, your books (not just the factual ones) have done the community a great service.
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dingus
Dec 2, 2005, 6:32 PM
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I'd like to say I have a carefully thought out strategy for when to use the sliding X but truth is, I don't. I rarely use a cordelette except for big wall belay type anchors.
For trad it has to be a questionable anchor before I'll worry about equalization at all. I will use it with either the knot trick or an extra sling or most likely the lead rope itself, to prevent undue extension.
For two bolt belays I'll use it with a lead rope backup or a daisy or extra sling backup.
DMT
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landgolier
Dec 2, 2005, 7:21 PM
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Most of this has been said already one way or another, but since this seems like as much of a poll as anything I'll jump on the dogpile:
A. Where the Sliding Knot is especially useful and effective, and why.
My main use of it is in single pitch trad cragging, when you know your anchor would never see a leader fall. Not that this makes shortcuts acceptable, of course, but in my mind it does make equalization a higher priority then extension. I worry most about extension when forces could come from different directions and thus put most of the pull on once piece, causing it to blow. When I know right where it's going to come from and I know the gear is good, I'm more comfortable letting really good equalization be my guard against extension. Anyway, if all the gear is turbo-bomber, I'll often have 2 truck pieces in the same crack with a sliding x on them for quick and dirty equalization, and then another piece or pair of pieces and then lace it up with the rope so my cordelette can stay on the rack.
I used to have one of those "2 slings pretied for a redundant sliding X" rigs for uneven 2 bolt sport anchors, but I've taken to just using a skinny 48" sling like a 2 arm cordelette for that situation since I bought a few double length mammuts (thicker slings eat up too much length in the knot). Nothing wrong with the X way, but it's kind of cluttery and not everybody understands how to set it up so it's not foolproof if you just hand it to somebody.
And as always, 2 micros in the same seam often calls for a sliding x or even an x plus a screamer. Possibility of extension is here sacrificed for ease of setup when out there on lead.
B. When the Sliding Knot is NOT effective, and why.
I remember seeing test results saying it basically acted like a clutch under sudden loading (rgold, maybe?), so any time the change in direction of pull and the fall force could happen at the same time it's a bad idea. Hence my worry about anchors that could see leader falls. Also, sliding X'd micros should therefore be slung generously.
C. Contrast the use (giving specific circumstances) of the Sliding Knot with the Cordelette.
I can't really think of a situation that wouldn't clearly favor one over the other, except of course the X vs mini-cordelette for 2 bolts thing in part A. Generally I think of the X as a component, and the cordelette as the whole show.
D. Comment on the common use of the Sliding Knot and the Cordelette within the same anchor matrix.
I do very occasionally use it when the anchor is 4 pieces and running a 4 leg cordelette would put the power point too high or make the angles between the piecess too big, as cutting it down to 3 legs gets the job done quicker and with less gear than extending stuff, as you usually have to extend 2 to get enough length freed up. However, I'd say in 90% of those situations I would have been fine just nixing one of the pieces. The only situation where I both do and should use it is if I have 2 close together but less than ideal pieces, and 2 other more respectable ones. Slizing X the 2 stinkers and run a 3 leg cordelette.
Warning: driftage ahead. One somewhat wacky trick I have done to get a 4th piece into a cordelette anchor without running a 4th leg is to throw a skinny sling or a long prusick on the lowest piece so that the sling hangs below where the power point will end up. When you gather the strands to tie the power point knot, just lay it in there and tie it in with the rest. It will be equalized with the rest, and while its loop will hang lower than the others and not be weighted this doesn't matter as the force will be transferred to it via the knot, and the other 3 strands form a bomber power point loop by themselves. A little bit rube goldberg, maybe, but nothing wrong with an extra trick in the bag if you know when _not_ to use it.
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cfnubbler
Dec 2, 2005, 8:29 PM
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IMHO (which is considerably different from many expressed here) the sliding x is best employed on two marginal to fair pieces, where, in my assessment, both are of roughly equal quality. Its use in this situation maximizes the overall strength of the resulting anchor point, minimizing the chance of complete failure. True, it introduces the possibility of extension, but in these situations, I'm most concerned about complete failure of the anchor point since both component pieces are questionable.
Where I would not employ it is in equalizing 2 pieces that are in my judgment of significantly different quality, i.e one is bomber and one is marginal. In this case, the relatively high chance of failure of the weaker of the two unnecessarily exposes the better one to a possible shock load, and may well decrease the overall reliability. I don't have any hard data, but this seems intuitively true to me.
Where one chooses to use the the composite anchor point created with the sliding x is a different question. To me, two obvious applications are as a component of a larger anchor matrix (in which case I consider the pieces joined by the x as a single "placement"), and when equalizing two marginal pieces on lead. I'll frequently place two RPs equalized with the x for example.
Another difference of opinion I have with many of the prior posters: I never use the sliding a at a modern, high diameter 2-bolt anchor. If swinging leads, I use the 2-loop eight, and if leading all the pitches or in blocks, I use a double length runner knotted for static equalization. The former is faster than the sliding x, and the latter offers better redundancy. With two strong anchor points, these are more important considerations for me than dynamic equalization. Now if the bolts are rusty quarter-inchers, I might reconsider....
Just my 2 cents,
-Nubbler
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antiqued
Dec 2, 2005, 8:40 PM
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(Thirty years of trad, and unable to type fast enough to keep up with the posts coming in.)
A. Where the Sliding Knot is especially useful and effective, and why.
Whenenver I wish to distribute the load between two pieces not in a near- vertical line. It is the only effective way I know. In a vertical line, clove hitching works better.
B. When the Sliding Knot is NOT effective, and why.
For a belayer in a hanging stance, clipped in with a static sling or a short length of rope. If one of the two pieces fails, the belayer falling on the static sling will increase the load comparably to the load sharing you expected from the failed piece. If the belayer can hold his own weight, then that ‘shock’ load won’t occur.
It also seems silly to X a very weak and very strong piece. But if those were the only options (suspect bolt and an RP not in a vertical line?) then maybe I would do it with a snug knot for the RP
C. Contrast the use (giving specific circumstances) of the Sliding Knot with the Cordelette.
I have rarely constructed cordelette anchors that can distribute the load if the left or right piece fails. Therefore cordelettes would be superior only if at least three pieces were required to carry the load, not if 3 pieces are desired for safety sake, but when there is the real expectation that two pieces would be insufficient. The exception is when the three points can be the base of a pyramid, with the apex pointing to the direction of fall. (Doesnt have to be a perpendicular pyramid). Now load can distribute to three,and then to two if one fails.
D. Comment on the common use of the Sliding Knot and the Cordelette within the same anchor matrix.
I've done it sometimes (say two RPs), but I may be fooling myself. If the order is rock – sliding X – cordellette, then if one piece fails on the sliding X, the other is out of the system, tied off or not. There are geometries in which this is not true, but for ‘planar’ arrays of pieces and pull, it is. That is the most common scenario. Using a cordelette to group three pieces into a sliding-X is not using it as a cordellette, IMO. Slings can do the same thing.
Regarding redundancy vs extension. For trad multipitch, the direction of a factor two will be down, barring rope catching on something. below the belayer. So a wide range in angles is not often necessary. If it is, the redirection is taking some of the fall energy. If the sliding X equalizes over +- twenty five degrees, it is pretty good to me.
I will usually clip one or more strong pieces directly as a partial backup, unless using a cordellette. This provides some redundancy. Given the one belayer, rope, belay device, harness we already deal with, not too mention the one sling, one biner, one piece keeping us from long falls, I don’t lose sleep over a single sling as an anchor connector. It’s not like an untended top rope anchor being sawed away by repeated swings.
John
In a follow up, you wrote about the importance of avoiding the factor two situation entirely. If you put on the safety engineer hat, this can’t be done. You can only try to do it by putting in other gear*. If that other gear is close and it sees a quick fall, that fall is near factor two - near enough that it might as well be. With the pulley effect, this one piece of gear sees 50% more load than we are arguing about how to distribute among 2 or more pieces. So if there is a ‘statistically’ significant need for distributing this load at the anchor, then there is a very much higher ‘statistically’ significant chance that the lead piece will fail, and then the anchor will indeed see a factor ~2..
(* actually, with a dynamic belay, the anchor should never see that type of load – so using a tube type device, and keeping the line clean and free of kinks should protect against the 8kN loading.)
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joshy8200
Dec 2, 2005, 9:35 PM
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A. I like it at 2 bolt belay station, it equalizes the load between 2 equally bomber points of an anchor...fast and strong.
I would possibly (though never had to) use a sliding knot on two placements that were BOTH marginal. That way since they're as truelly equalized as possible with a slidding-x when loaded...they truelly share the load.
B. I wouldn't use it to equalize two pieces that were of varying quality...Quality meaning the trustworthyness of the placement. Because obviously if one placement is of lesser quality and fails under load...will shock load the remaining piece (which might or might not hold).
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mcfoley
Dec 2, 2005, 9:41 PM
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A. Where the Sliding Knot is especially useful and effective, and why.
Dynamic equalization, Fast.
B. When the Sliding Knot is NOT effective, and why.
When 2 pieces are placed farther apart than ideal for this "knot".
C. Contrast the use (giving specific circumstances) of the Sliding Knot with the Cordelette.
For multipich anchors the "X" is less redundant than a typical cordalett.
D. Comment on the common use of the Sliding Knot and the Cordelette within the same anchor matrix.
I use them together all the time...X as a componet of a larger cordalette anchor
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vivalargo
Dec 3, 2005, 4:04 AM
Post #35 of 47
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[quote="antiqued"]
John
In a follow up, you wrote about the importance of avoiding the factor two situation entirely. If you put on the safety engineer hat, this can’t be done. You can only try to do it by putting in other gear*. If that other gear is close and it sees a quick fall, that fall is near factor two - near enough that it might as well be. With the pulley effect, this one piece of gear sees 50% more load than we are arguing about how to distribute among 2 or more pieces. So if there is a ‘statistically’ significant need for distributing this load at the anchor, then there is a very much higher ‘statistically’ significant chance that the lead piece will fail, and then the anchor will indeed see a factor ~2.."
This all true in a sense, but the consequences are different.
A. If the "first pro" blows, you don't die; if the anchor blows, you most likely will.
B. The first piece, even if it blows, can provide some load limiting, meaning it can slow the falling climber down before he shockloads onto the belay.
C. Protecting the belay against factor 2 forces is key and requires whatever we can do to keep mambo loads from shockloading the anchor.
Is the anchor better suited than a single piece of pro to sustain a huge shock load? Yes, but why test it if you have to? IOW, sticth the fricking crack off the belay, and keep plugging stuff in till you feel comfortable that you won't plunge onto the belay anchor--usually a worst case scenario.
JL
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el_jerko
Dec 3, 2005, 10:13 PM
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If you are concerned about a factor 2 leader fall onto the anchor, just give the leader a big loop of slack, you can get the fall factor down to 1.5 no problem.
No, I am not serious, but I think there is a tendency to get carried away with the math.
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asandh
Dec 3, 2005, 10:26 PM
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My general anchor preference is for Redundancy and "Approximate" Equalization with No Extension.
I'm not a fan of the "sliding X" and rarely use it.
Because of the potential forces involved in extension due to one side of the sliding X failing, I always consider a sliding X setup as only one piece of pro. I use this setup only to combine marginal pieces so they reinforce each other across a multi directional range.
When climbing multi pitch trad, I rarely use a cordelette unless I am leading every pitch. I prefer instead to employ the rope for anchor building because it adds some dynamics to the anchor. I use the following method to equalize 3 pieces :
1. place gear #1 in rock
2. make a fairly big loop with the rope and create a figure 8 on a bite with the knot close to your harness
3. within this bite clip in to piece #1 with a clove hitch
4. place piece #2 in rock
5. clip in to piece #2 with another clove hitch within the large bite. cinch it up so that these 2 pieces are equalized at the figure 8 knot.
6. place piece #3 in rock (piece #3 should be the farthest one from you)
7. grab the rope coming out of the figure 8 on a bite (not the one going to your harness) and clip into piece #3 using a clove hitch, making sure it is equalized with the other 2 pieces at the figure 8 knot.
8. other pieces can be added to this setup as needed. slings may be employed at piece #3 to minimize the amount of rope used if necessary.
The above essentially creates a dynamic coredellette out of the rope.
Of course if your next pitch is 200 ft long you may not want to use this method.
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csgambill
Dec 3, 2005, 11:58 PM
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It's not redundant. Spend 8 bones and get a cordlette. Once I tried it I never went back.
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slcliffdiver
Dec 4, 2005, 1:33 AM
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In reply to: A. Where the Sliding Knot is especially useful and effective, and why.
Why: in part because it's fast.
Also sometimes in pairs or some other wierd configuration for belaying a climb that starts with a traverse.
In reply to: B. When the Sliding Knot is NOT effective, and why.
Also with cr*p anchors generally I think I've had some pieces that I was happier with than others. I think I've generally been happier using the rope(s) and adjusting the length of the arms of the rope and how I had the biners hooked in to distribute the forces the way I'd like at least for the arms of the anchor and maybe X's for pairs of pieces.
I do remember doing the linked X thing periodically to put about 50% of the force on one piece and halve it between the others but I don't recall when it was neccisity, convience, playing around or showing off.
Anyway I think my general instinct has been when I realized I wasn't going to be super happy with an anchor is to start with the rope(s) (less chance of shockloading) then make things up from there instead of starting with an X or a cordellette (if only to make it slightly easier to argue the other person leads the next pitch :wink: ).
In reply to: C. Contrast the use (giving specific circumstances) of the Sliding Knot with the Cordelette. D. Comment on the common use of the Sliding Knot and the Cordelette within the same anchor matrix. |
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iclime
Dec 9, 2005, 6:24 AM
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I agree with a lot of what has already been said, particularly that with two beefy bolts, whatever tickles your pickle is great.
A few add-ons:
A: Sliding-X is a heck of a lot easier to set up with one hand. On crazy leads that I want to bail off, I'll sometimes set up two pieces next to each other and set up a sliding-x so I'm not lowering off of just one piece.
B: While there a lot of situations that I'll use the sliding-x as a part of my safety system, I can't think of a time that I would want it being the only set up keeping me on the wall. I don't share this same concern with a cordellete.
M
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pieter
Dec 9, 2005, 3:35 PM
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This seems like an interesting idea. Not sure if it's safe though.
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reg
Dec 9, 2005, 4:21 PM
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pieter: i'm not familar with the larks foot they talk about but one thing i did notice - an overhand knot was mentioned when using the cordelete. i believe an 8 should be tied at the P point. i'll have to look up the larks foot.
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reg
Dec 9, 2005, 4:25 PM
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larks foot is a girth hitch right? so i think their idea is really bad.
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boltdude
Dec 9, 2005, 5:04 PM
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We put this on the ASCA website years ago, and I see nothing in any of these arguments to change it. We got a lot of flak from all sorts of people including guides who've taught the sliding X for years. Still, the sliding X fails a basic test of logic - if you need it, then it's too dangerous to use. If you don't need it, why are you using it? Especially considering ultra-skinny modern slings that may get frayed over time, may find some edge or burr to slice on in an extension situation, etc. Anyway, here's the note - Greg Barnes
Note: The Sliding X
Many climbers use a "sliding X" to equalize two pieces - ususally beginner climbers with bolt anchors. You should NEVER use this except in two specialized cases (see below). While the sliding X does equalize the pieces, it assumes that neither could break, since if one does break, there is severe extension in the system - enough that it would likely cause the carabiners to break. Since it assumes neither piece would break, it's a stupid system - if neither would break, there's no need for equalization. If one might break, then there is WAY too much extension. This is why many call it the "death X." Instead, use one sling off of each bolt or piece. You can tie one shorter to approximately equalize the pieces if needed.
The two cases where the sliding X is used:
- equalizing tenuous pieces in a larger anchor - for instance, two poor nuts in a large natural pro anchor. The nuts are equalized, then the sliding X is equalized with other pieces through a cordelette, webolette, or other non-extending method.
- equalizing two very tenuous pieces in extreme aid - for instance, a hook and a bashie on A4 terrain.
http://www.safeclimbing.org/education/slidingx.htm
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tradklime
Dec 9, 2005, 5:18 PM
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Greg, I think your assessment is fair with the sliding-x without extension limiting knots. The addition of knots mitigates the issues you raise, in my opinion.
Even 2 inches of dynamic equalization can make a big difference when you compare it to a cordalette. A slight shift on a cordalette anchor can result on the entire load being placed on a single piece, this same load shift can be addressed with very limited dynamic equalization. The knots also mitigate the lack of redundancy.
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roy_hinkley_jr
Dec 9, 2005, 5:36 PM
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In reply to: While the sliding X does equalize the pieces, it assumes that neither could break, since if one does break, there is severe extension in the system - enough that it would likely cause the carabiners to break. Since it assumes neither piece would break, it's a stupid system - if neither would break, there's no need for equalization. If one might break, then there is WAY too much extension. This is why many call it the "death X."
Still waiting for someone to cite any accident in the past 30 years where this has been an issue. Please provide a reference in ANAM or one of the Euro journals. In many cases with trad gear, the sliding-X is safer than the death-o-lette.
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ericbeyeler
Dec 9, 2005, 6:26 PM
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As discussed here, there is a sort of hybrid method that combines the advantages of the sliding X and cordalette (it also has some of the weaknesses of each on multiple point failures) It is similar in use to the sliding X with knots to limit extension, but will work with three pieces.
Eric
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