Consensus on knots in slings

Xam wrote: Do you understand that you should never be falling 'directly' on any static sling (dyneema or nylon or cord)?

How dynamic is a five foot long piece of dynamic rope? How does one factor a factor 2?

Don't Mountain Project (overcomplicate) this. Try to avoid tying your Dyneema slings and use a nylon one instead. If you have to use a Dyneema sling with a knot in it, be aware it is weaker and adjust accordingly.

Robots and Dinosaurs wrote:Don't Mountain Project (overcomplicate) this. Try to avoid tying your Dyneema slings and use a nylon one instead. If you have to use a Dyneema sling with a knot in it, be aware it is weaker and adjust accordingly.

Both nylon and dyneema get weaker when a knot is introduced. The difference is falling directly onto a nylon sling doesn't generate as many Kn's as with a dyneema sling.
the nylon is more dynamic than the dyneema hence less peak force is generated.

rocknice2 wrote: Both nylon and dyneema get weaker when a knot is introduced. The difference is falling directly onto a nylon sling doesn't generate as many Kn's as with a dyneema sling. the nylon is more dynamic than the dyneema hence less peak force is generated.

So which would you rather knot?

neither

rging wrote: How dynamic is a five foot long piece of dynamic rope?

Much much more than the perlon cord or nylon sling you might have used in your anchor because the rope is designed to be dynamic and neither of these are.

rging wrote: How does one factor a factor 2?

If you factor 2 directly onto your belayer, assuming your belayer can hold the fall, the 'top piece' is now your belayer's device. The 'top piece' force is reduced by the 5 foot tie in rope by the time that force gets to your anchor masterpoint. So (Length of Fall)/(Length of Rope out between belayer and leader + 5 Feet). But truthfully, this would be a miss-use of the fall factor concept.

rocknice2 wrote:Don't waste your time with Gaz's response. He's just a bored drunk.

Judgemental aren't we ?? And no I don't drink often and I posted this comment to try and kill the last thread I started because I was unsure of the issue with Dyneema as a 3 piece anchor (which BTW, still has not been addressed). I have watched DMM videos like most of the guys here and totally get the direct fall on dyneema thing and understand knots efficiencies in both nylon and dyneema/spectra. It still does not answer the BFK 3 piece anchor question and I've had no definitive answers, just idle hear-say comments. If no one has the scientific data then say so!!

So the quote: "Tying an overhand knot in a Dyneema sling reduces its strength by 50%; its better to use a 7mm nylon cordelette when rigging the equalette, as you will be tying lots of knots".

is not my quote. It is from Gains/Martin, Rock Climbing, the AMGA Single Pitch Manual, P161, picture #2 (far right).

The reason I put a qualifier was that Xam's comment said I should, so I did it to do a CYA. I was trying to make a general rule of not tying knots in dyneema but that's obviously incorrect to make an 'absolute' statement which is what I wasn't trying to do.

Xam wrote: I don't really want to wade into this but after reading your other thread, I have to ask this pretty basic question: Do you understand that you should never be falling 'directly' on any static sling (dyneema or nylon or cord)? The belayer should always be attached via the rope (using a clove hitch or fig eight or whatever). The leader will also be on a dynamic rope. As such, you will always have a dynamic element in the system that will reduce your load on the anchor to well below the failure point of any commercial climbing sling, knotted or otherwise, even in a fall approaching a FF2. Snapped slings (knotted or otherwise, and people use dyneema slings for anchoring all the time) is a vanishingly small component in climbing accidents. Of course you have to use them correctly.

Xam, I totally understand the points you make above. However on trad gear, it's is usually impractical to tie in with the rope to an anchor. You will be on one piece of pro. The anchor should have at least 2 pieces of pro, then tie into the masterpoint as you know or you could go along tying in cloves as you go but you have a serial anchor doing that (bad juju).

The issue that came up in the other thread was about making a 240cm dyneema sling into a 3 point 'equalized' anchor using a BFK. Problem is that there is a BFK that weakens the dyneema and the issue of zipper shock loading. 11kN is just above the maximum shock load from a big lead fall (8kN) which comes from the dynamic rope and is placed onto the anchor leg(s). That is the concern. You commented about snapped slings being vanishingly small. Is it because most Trad climbers still use 7mm cord ???? That's what I want to know. Basically I will stick with 7mm cord until I have proof otherwise.

Gaz wrote: Xam, I totally understand the points you make above. However on trad gear, it's is usually impractical to tie in with the rope to an anchor. You will be on one piece of pro.

No...still missing the point. The belayer cloves into the masterpoint of the multi-component trad anchor with rope, so they are not on one piece of pro but instead on the multicomponent anchor. But I think we are on the same page.

Gaz wrote: The issue that came up in the other thread was about making a 240cm dyneema sling into a 3 point 'equalized' anchor using a BFK. Problem is that there is a BFK that weakens the dyneema and the issue of zipper shock loading. 11kN is just above the maximum shock load from a big lead fall (8kN) which comes from the dynamic rope and is placed onto the anchor leg(s). That is the concern. You commented about snapped slings being vanishingly small. Is it because most Trad climbers still use 7mm cord ???? That's what I want to know. Basically I will stick with 7mm cord until I have proof otherwise.

Many do use 7mm cordalettes. Many use the rope. Many also use dyneema slings. Use what you would like but your logic is misguided for the simple reason that ONLY a FF2 directly on the belayer is going to generate loads approaching your 11kN and that risk is minimized by standard climbing practice, such as placing a jesus piece early and having the belayer clove into the anchor masterpoint with the rope. In a FF2, you are much more likely to be injured due to the belayer losing control than anchor failure. There are many excellent reasons to choose cord over a dyneema sling...anchor failure due to snapped slings is not one of them.

Check out this page: dmmclimbing.com/knowledge/s…

It is not exactly the same but is as close to an experimental confirmation that the dyneema sling anchor is fine as you are going to get. The test is much more severe than in practice. Notice that a two point overhand equalized sling broke with 21.7 kN at the master point. This is more severe than a three point anchor rig and gives you more than 2.5 X safety factor over your 8 kN fall. Do you think you are going to generate a >20 kN force in your leader fall? And whatever the leader fall force is, that force is going to be reduced by the time it gets to the anchor by standard climbing practice (i.e. belayer cloving into the anchor with the rope).

BTW, a BFK refers to a specific knot...and one not generally used as the master point in a trad anchor (usually an overhand, fig 8 or fig 9). The BFK is used most frequently as a TR anchor instead of say a double fig 8.

Edit to add: It should be noted that good gear is way more important than any of this (other maybe than the point that the belayer should always clove in with the rope).

Edit to add: Just reread this and wanted to make absolutely sure my point is clear...here it is...wait for it...as long as your belayer is cloved into the master point with the rope, the force on the anchor is never going to hit 11 kN (much less the 21.7 kN they showed at DMM) and you can use nylon, dyneema, rope or whatever reasonable material to generate your multipoint anchor.

Jake Jones wrote:Sheesh. High forces in knotted dyneema=bad. High forces on any static material=bad. We don't really need a dick measuring contest to decipher these things.

Sorry for sounding so pedantic...just trying to make myself clear. My point is that if you clove in with the rope, the forces will not be high on the anchor (which is generally static unless you build it with the rope). It was unclear to me that Gaz understood this.

Xam wrote: Sorry for sounding so pedantic...just trying to make myself clear. My point is that if you clove in with the rope, the forces will not be high on the anchor (which is generally static unless you build it with the rope). It was unclear to me that Gaz understood this.

I understand this.

Xam, BTW, I really appreciate the time you have taken to explain this stuff and your 'pedantic-ness' is not going wasted. Just thought you should know. :-)

FYI, you'll probably find this very interesting....

lamountaineers.org/pdf/xRop…

Gaz wrote: It still does not answer the BFK 3 piece anchor question and I've had no definitive answers, just idle hear-say comments. If no one has the scientific data then say so!!

What else do you want to know? MattN posted a link to tests on various materials in a 3-leg BFK knot anchor already.

Read the conclusion on the last page

http://user.xmission.com/~tmoyer/testing/High_Strength_Cord.pdf

They rate a 7mm cordelette as the best option for several reasons but none of the materials tested failed when used in a 3 point anchor in a normal multi-pitch climbing situation.

rocknice2 wrote:Read the conclusion on the last page http://user.xmission.com/~tmoyer/testing/High_Strength_Cord.pdf They rate a 7mm cordelette as the best option for several reasons but none of the materials tested failed when used in a 3 point anchor in a normal multi-pitch climbing situation.

Perfect! Thank you for your trouble in finding and posting this. :-)

So my conclusion is (and this is my personal choice [I understand your choices/decisions may be different]):

I will continue to use 7mm cord for anchors. Extending a leg with dyneema/spectra is good too but I will not be tying knots in the dyneema/spectra runners.

Thank you for a great discussion. I think I've exhausted this topic and I'm sorry for you who I've subjected to a myriad of questions. I was just trying to convince myself that a knotted 240cm dyneema/spectra runner for an anchor is OK. And I can't justify it to myself. So that said, I'm done with this topic. Thanks again.

Gaz wrote: Perfect! Thank you for your trouble in finding and posting this. :-)

That link was posted in this thread on March 14.

Some illuminating info circa 2013 here: https://www.youtube.com/watch?v=Vrgadjo9niY
Summarizing, ANY knot even just in clipping a sewn Dyneema sling to a biner at an anchor with a clove hitch, or to shorten an anchor, can critically weaken the sling, to failure in several situations, particularly at a stance where factor 1 falls with short lengths of sling but stepping off a ledge, or factor 2 where moving up just a few feet then dropping, as if onto a short daisy while arranging belay anchors, always seem intuitively minor, but which in reality are too often the way extreme shock loads really happen. The paradox is, that despite our informed awareness, most climbers consider a fifty-foot fall at the end of a 150-foot pitch much worse than stepping off a belay with the anchor at your waist with five feet of slack in your tie-in sling. The long fall results in a factor 0.33 fall, while the short step is close to factor 1, and if onto static spectra or dyneema may fail, shock load the anchor to failure, or at least cause significant internal injury compared to tying in with a bight in the lead rope with its intrinsicly better, lower impact force.

Maybe one reason we don't often hear of people breaking their pelvises by falling onto anchor attachments (besides the fact that many use the rope) is that people instinctively grab something (e.g. the anchor attachment) with their hand.

and the entire body takes the hit, it's not a focal injury to the pelvis.

Ian - think of it as a spiral thru time.  It goes around in circles and seemingly repeats, but actually slightly evolves and advances as new knowledge and equipment (and climbers) come out.  

Otherwise we’d all just need 12 issues of “Climbing” 1970-1971 and be done with it.