Is a sliding X using a doubled over sling ever redundant?

Forgive me, I am new to climbing, maybe I am missing something.

I saw this video, youtu.be/she8vH1DCBU and at around 13:30, they talk about how you have to choose specific strands out of the 4 to twist into the X in order for the anchors to be redundant. However, not wanting to make this mistake, I was testing with my own 240cm sling and getting very different results.

This is where my inexperience shows, because I really can't explain how I was testing it.

The best I can do is that depending on which combination of strands I was using for the X, it would change between one anchor being redundant if it failed, while the other caused a complete failure if it failed.

It also seemed like it depended on how "neat" the sling ran through the two anchored carabineers. I.e. if it was twisted or crossed.

Perhaps I am overthinking it, but this gumby appreciates any help.

Tie the limiting knots and it may become more apparent. Also, it seems people are more in favor of the quad theses days than the sliding X for many applications. 

K.I.s.s =keep it simple silly.

If you are new to climbing, focus on building a solid anchor with a 120 sling or do what the other guy suggested and make a quad. No need to do a sliding X with a 240 cm sling if you do a quad with limiting knots on both sides. Every anchor application has its advantages and challenges. 

I do have a 7mm cordelette quad, I was just wondering if there is a way to make the doubled over sling sliding X redundant.

Assuming you are talking about the part that begins around 13:40, the easiest way is to fold the 240cm sling so that it looks like a 120cm sling made of 2 parallel loops.  Then pretend you're working with a single 120cm sling.

Alternatively, you could try all 6 combinations of 2 out of 4 strands. 2 of the 6 combinations should work. But this is probably harder.

I don't think this is part of the question, but to be clear, the video is only talking about redundancy with respect to the bolts / carabiners failing. Nobody claims any of the knot-less versions to be redundant in the event that falling rock/ice cuts one of the strands. Also, it's important to note Bobby is pretending the carabiner failed - the behavior would be less catastrophic if the bolt failed but the carabiner stayed intact.

Also FYI the amount of extension with a doubled-over 240cm sling (equivalent to a single 120) is quite high.  I'm under the impression a pure sliding X w/o limiter knots is not recommended for slings that long (even if you're not worried about sling-cut redundancy).

Just another option to have in the toolkit, a girth hitch master point would be a good way to make the doubled over 240 sling in the video into a redundant anchor

https://www.alpinesavvy.com/blog/try-a-girth-hitch-at-the-master-point

To the OP… Why are you considering this particular anchor? What is it you are trying to accomplish? Did you run in to a situation in which this seemed to you like the best anchor option? I’m legitimately looking for more context because I’m almost 100% certain there are other options out there that would be easier/better. With context, maybe we could offer up more focused suggestions.

Kevin DeWeese wrote:

Yes there is. The video showed it. You answered your own question when you posted:

That combination shown in the video was: if you take the loops that are brought down from the anchor biners and consider one to be front and one to be back, you take one strand from the back loop and one from the front loop to create the twisted loop that is paired with the loop created by the remaining strands

Also the application and premise of the video isn’t to instruct the principles behind building a solid anchor but the strength of the quad (using Dyneema) with limiters. So, you are not getting the adequate answer because you are looking at an inadequate(to your question) video. Which won’t address your question. I would suggest taking an anchor building course, buying an anchor building book, or hiring a guide. There is also a new page that popped up on this forum where people have listed YouTube and social media accounts where solid instruction is taught.

I think you are asking the right questions. Either way, it will help you as you learn. 

W J wrote:

Forgive me, I am new to climbing, maybe I am missing something.

I saw this video, youtu.be/she8vH1DCBU and at around 13:30, they talk about how you have to choose specific strands out of the 4 to twist into the X in order for the anchors to be redundant. However, not wanting to make this mistake, I was testing with my own 240cm sling and getting very different results.

This is where my inexperience shows, because I really can't explain how I was testing it.

The best I can do is that depending on which combination of strands I was using for the X, it would change between one anchor being redundant if it failed, while the other caused a complete failure if it failed.

It also seemed like it depended on how "neat" the sling ran through the two anchored carabineers. I.e. if it was twisted or crossed.

Perhaps I am overthinking it, but this gumby appreciates any help.

Don’t use such a long sling (4 strands) with a sliding X because as hownot2 says “it’s too easy to screw up”. The strength off these scenarios doesn’t matter, it’s all strong enough.

The X will shock load if one piece fails so don’t use it at all if you question either piece. In general it’s an advanced technique.

I use an X to make a quick anchor on 2 pieces then back it up with a totally independent third piece, makes anchor building quick and easy.

Serge S wrote:

Alternatively, you could try all 6 combinations of 2 out of 4 strands. 2 of the 6 combinations should work. But this is probably harder.

Okay, so I was thinking there would only be 2 correct combinations out of 6. But if that's the case, it just doesn't seem practical because it's too easy to accidentally mess up.

To those wondering why I'm going to the trouble, I have learned about other anchors. I just came across this video, and although its focus isn't necessarily anchor building, it mentioned that easy mistake. Just wanting to be prepared, I started messing with my sling to better understand the mistake when I realized it wasn't as simple as the video led me to believe. 

The one complaint I have about the normal sliding X is that the two limiter knots are reducing the strength significantly. From what I understand, doubling over the sling would help balance the strength back towards it's normal rating.

I also wasn't sure if the limiter knots would make it redundant if it's not redundant without them. Hopefully that all makes sense. Thanks for everyone's input so far.

Here is the easy way Warren:

Serge S wrote:

Here is the easy way Warren:

Wow, that picture makes it so easy to do it right. I was really...really just overthinking it. Thank you so much

OP, are you choosing a sliding x anchor because you are trying to equalize the load on each anchor point? If so, you may want to rethink that. Apparently, recent research indicates that the “clutch effect” of the carabiner(s) in the webbing will negate a lot of the equalization and the load will inevitably fall disproportionately on one anchor or the other. Of course, the type and condition of the sling used, the type of biner(s) chosen, and where the main carabiner happens to be within the sliding x when the load hits, will all influence this clutch effect. Maybe rgold, Jim Titt, et al have done some of this testing?

Also, I’m not sure anyone has mentioned what could happen to the belayer when one anchor point of the sliding x setup fails and the anchor extends. In that scenario, you could have the jolted belayer lose control of the belay.

For some reason, around Barcelona, I’ve seen a whole lot of climbers use a sliding x with a single sling on two bolt anchors. Seems to be the fashion. I’m sort of ok with it if we are talking modern bolts and rockfall is not an issue… but why not tie a simple overhand or figure-8 and make a master point? It takes just a few seconds and you have redundancy, no extension, and a master point. I’m talking with modern bolts here. 

Warren just to be clear... Serge Smirnov is using TWO sling to make the sliding X redundant. IMO this is the best (only?)way.

Good Luck out there.

Rob

Two slings does add redundancy (so, better), but I can’t see it doing anything but worsening the clutch effect I mentioned above. I’m still wondering, of course, if the OP is interested in this anchor because of the theoretical “equalization” he thinks it might give him. 

Robert Townley wrote:

Warren just to be clear... Serge Smirnov is using TWO sling to make the sliding X redundant. IMO this is the best (only?)way.

Good Luck out there.

Rob

There’s only one join in the pic there - I think he’s doubled over a single long sling as Warren has asked about?

Daniel Joder wrote:

OP, are you choosing a sliding x anchor because you are trying to equalize the load on each anchor point? If so, you may want to rethink that. Apparently, recent research indicates that the “clutch effect” of the carabiner(s) in the webbing will negate a lot of the equalization and the load will inevitably fall disproportionately on one anchor or the other.

Also, I’m not sure anyone has mentioned what could happen to the belayer when one anchor point of the sliding x setup fails and the anchor extends.

I really just wanted to understand this for no other reason than to expand my climbing knowledge. But I will admit I was thinking this to be a pretty bomber anchor.

Could you link something explaining this "clutch effect"? I am only finding things pertaining to manual transmission clutches.

Yes, others have mentioned that. Which is what makes the limiter knots essential for such a long sling. 

Thanks for the response 

Whoa. This thread is a bit out of hand for giving a beginner advice.  

OP, the sliding x is never redundant no matter what loops you pull together if it is a single sling… until you tie limiter knots.  

Furthermore, it does not accomplish what climbers used to believe it accomplishes.  It’s a has been technique.  Forget about it  

The only problem is when you double the sling the wrong way.  If you double the sling correctly, as in Serge's picture, it functions as one sling every time.  I've never witnessed anyone double a sling the way the HowNot2 guys did it in their video.  

Warren, the "clutch effect" is what happens when the carabiner on the sliding x doesn't immediately slide into a perfectly equalized position due to the friction between sling and carabiner. Thus, one leg of even this supposedly "equalized" anchor will inevitably take more of the load than the other leg. How much load will the load be distributed to each leg? That will be VERY highly variable and will depend on where the carabiner is in the sling when the load hits (hanging off to one side vs. straight in line with the load, etc.), the type of carabiner being used (fat and round vs. more square-ish), and the type of sling or webbing involved (thin and smooth vs. thick and rough). Make sense? If you have two slings in the sliding x, I would think the clutch effect would be even greater.

So... If I have two modern bolts, I personally don't care as much about "equalization" as I have pretty good redundancy. After redundancy, I personally want to avoid extension so the belayer doesn't get jerked around in case of a very unlikely single bolt failure. So, if I have two good bolts (and I have chosen not use the rope itself), I often will do something simple like this:

If my sling were longer, or with a cordelette, I might have included that third bolt and done a very similar thing. (If you were really worried about those two new, big, modern bolts, you could simply clip a quick draw from the third bolt into the master point.) We were using double ropes in case you wondered about why there are two... I just cloved into the master point with both (with a locker). You could set up a guide mode belay off the back of the master point carabiner, the master point itself, or the shelf. More options than the sliding X system. Also, I don't always use lockers on the two bolts--if I am where I can see them and reach them, like this example, I see no problem using normal biners.

Probably too much information... but kudos to you for wanting to learn and wanting to know the whys and why nots...

Others, feel free to critique or add info... I don't mind learning or getting corrected myself.

Hopefully I don't muddy the waters too much with this...

1. As noted upthread, the sliding x has largely been supplanted by the quad. If you're just getting into climbing, I would avoid the sliding x (use a quad if you want to use a sliding system). There are some edge cases where it might make sense to use it, but those are pretty few and far between, so I would not make it a default choice.

2. The quad (and all sliding systems) suffer the risk of extension and attendant catastrophic impact forces. Here's a link to some small-sample research I did a few years back. Further discussion of the clutch effect, load distribution (or lack thereof), etc. can be found in the bibliography. Some of it is in Italian and French (and maybe German? don't remember); Google translate is your friend.

http://staff.weber.edu/derekdebruin/research/extension.pdf

3. This conversation seems to overlook redundancy as a special case of security (or resilience if you prefer). When building an anchor, the overriding concerns are strength, security, and simplicity (which is a short-hand for attempting to eliminate human error; it's harder--but not impossible--to mess up things that are simpler).

Redundancy is one type of security, where you have additional things (whatever that might mean), that may or may not be used, that provide a backup. When considering redundancy, we need to consider potential failure mechanisms.

The first failure mechanism is component failure: the cam pulls, the ice screw rips from the ice, the bolt blows out of the rock, the carabiner connecting to the component unclips or breaks. In any of these cases, depending on how it is rigged, a sliding system can result in catastrophic failure due to extension. In attempting to create security, strength can be compromised. So...either use fairly closely spaced limiter knots (not more than 6 or 8 inches apart), or only use components that are unquestionably strong even if a carabiner is unclipped somehow. Basically, this means sliding rigging like a quad is reserved for modern bolts in good rock.

The second failure mechanism is material failure due to cutting. Sliding a sling or cord a half dozen times over a sharp edge is a great way to cut it, so when rigging the anchor make sure it isn't loaded over an edge. Maybe consider other options if you've got crampons or ice axes in the mix, too. Finally, understand the risk of rockfall striking the anchor. If it hits between the limiter knot and the component, the limiter knots do add redundancy. However, if the rockfall strikes between the limiter knots, that can sever the anchor completely (another argument in favor of closer spacing on limiter knots). Yes, 4 strands of material in a quad might not all get cut, but that depends on the material used and the specifics of the rockfall. I've seen rockfall cut multiple strands of rope in the same go; cordelette or a dyneema sling is even more vulnerable. If you're only attached to 2 of those 4 strands, that's even less great odds.

At some point, if you make the limiting knots close enough together, you might as well just make a V and tie a knot, as Daniel shows in his photo above. That solves probably 90%+ of your anchor needs when you're first learning to climb. I discuss this and the human factors involved in more detail in this white paper:

http://staff.weber.edu/derekdebruin/research/quad.pdf

4. For other ideas, here's a translation of anchor rigging strategies recommended by our German speaking compatriots across the pond:

http://staff.weber.edu/derekdebruin/research/anchorsdav2020.pdf