Three point anchor - The Saga Continues

In addition to the items about Jim's two-point anchor setup already mentioned by David, it is worth noting that, especially in Germany and Italy, it is frequently assumed that the belayer will be belaying both the second and the leader directly off the anchor (the leader belay typically with a Munter). A potential problem with the direct leader belay is that the carabiner and Munter fly up when there is a leader fall. To minimize the upward displacement, the Munter carabiner is clipped to a very short loop, which is then clipped to one of the anchor points. (In Jim's photo, the Munter carabiner would be the one clipped to the third anchor from the left---the lowest one in the picture.) So an important role for that BoB loop is to provide a low-displacement location for the leader's Munter belay.

Since the typical European 2-point anchor has one bolt higher than the other, rather than the typical Murcan 2 bolts at the same level, the belay is rigged with the Munter biner on the lower anchor and the sling cloved to the upper anchor. With anchors placed at the same level, the clove just goes horizontally to the other bolt with no pretense of load distribution. Dave calls this a "banshee" belay on multipitchclimbing.com/

Although I'm not particularly drawn to what seems to me to be the pointless minutiae of the arguments for the different systems mentioned here and elsewhere, I can't help but note that the rigging with the rope that I posted on page 2 is just dandy with 2 anchors (just end at point #3) and is within seconds of being as fast as using any kind of dedicated pre-equipped sling (if you are not belaying the leader directly off the anchor). One advantage is that you rig everything, bolts, trad gear, plants, and combinations thereof in exactly the same way, every time.

David Coley wrote: In the normal application to a two-bolt anchor, both strands of the sling are used in the clove hitch, not just one.

... Ah, I think I understand; because the bolts are vertically aligned in Europe (as rgold mentions), you clip one end of the sling to the top bolt, and clove hitch the lower bolt in the middle of the sling with both strands? An "inline" anchor rather than a "hub-and-spoke" or "star" pattern?

Patrick Shyvers wrote: ... Ah, I think I understand; because the bolts are vertically aligned in Europe (as rgold mentions), you clip one end of the sling to the top bolt, and clove hitch the lower bolt in the middle of the sling with both strands? An "inline" anchor rather than a "hub-and-spoke" or "star" pattern?

Well normally the loop goes on the lower bolt and you clove the other strands into whatever else there is, the photo shows a three point anchor as that´s what was asked for by the OP.

Patrick Shyvers wrote: Well, yes, both strands are used, but one per bolt. Because of the clove hitches, the force cannot be evenly shared on both strands unless the pull is in the perfect equalized direction. Or are you saying this photo is not the normal application.

Correct - not the normal application, as the photo shows three bolts.

Brian L. wrote: Tying the bowline on a bight becomes very difficult when incorporating both strands. At least with a 18mm Nylon sling that I tried it with. Also, if you did that you wouldn't need the cloves, and this would just be a BFK anchor.

This might be due to a lack of practice :)
Remember you only tie the knot once a day, or even once per trip, so not really a pain.

Patrick Shyvers wrote: ... Ah, I think I understand; because the bolts are vertically aligned in Europe (as rgold mentions), you clip one end of the sling to the top bolt, and clove hitch the lower bolt in the middle of the sling with both strands? An "inline" anchor rather than a "hub-and-spoke" or "star" pattern?

Normally, you clip the BoB loop to the lower bolt and clove the sling to the upper bolt. There isn't normally a third bolt.

rgold wrote: Although I'm not particularly drawn to what seems to me to be the pointless minutiae of the arguments for the different systems mentioned here and elsewhere, I can't help but note that the rigging with the rope that I posted on page 2 is just dandy with 2 anchors (just end at point #3) and is within seconds of being as fast as using any kind of dedicated pre-equipped sling (if you are not belaying the leader directly off the anchor). One advantage is that you rig everything, bolts, trad gear, plants, and combinations thereof in exactly the same way, every time.

Being a Brit, most of my anchors are rope based. The BoB system being discussed can be very useful, and is worth trying out when:
1. you want some form of powerpoint (good with 2 seconds) on bolted anchors
2. one person is doing all the leading
3. you want the powerpoint as high as possible
4. if you are directly belaying the leader
5. you don't want to untie stuff each pitch
6. you don't like the other Euro approach of metal-to-metal when swapping leads. (i.e. big locker on one bolt, clove hitch one rope to this; clip guide plate carabiner to this locker; locker on second bolt and clove second rope to this.

20 kN wrote: Well, everyone has a different way of doing things. Many climbers carry a tether of some sorts, so I use my tether to build the anchor off of. I am a fan of completing tasks using equipment I normally bring on the climb anyway, so if I am going to bring a tether I am going to use it for more than one thing. In the case of bolted belays, I build my anchor using my PAS. This eliminates the need for me to bring extra slings or cord or the sole purpose of building an anchor. Further, if one wishes they can tie in with the rope as well (I do), to provide redundancy over the PAS.

Sure, normally I build my anchors with a cows tail/slings/whatever and the rope. If it becomes nescessary to build a masterpoint anchor for rescuing someone or setting up a haul etc then using what most climbers already are carrying (a sling) is the most logical thing to do and since Germans are familiar with the sling/BoB system that´s the best way to teach.

Patrick Shyvers wrote:I feel like a broken record, but it occurs to me that the BoB sling setup is potentially a little lacking from a strength standpoint too. Slings are typically 22kN in loop form. Clove hitching so that only one strand of the loop is loaded hypothetically reduces the strength of the anchor leg to 11kN, and then taking off 33% for the knot you're at 7kN per leg (or if the 50% reduction for knotted dyneema is to be believed, 5.5kN) If one is a guide with two followers, as David suggests, that's a 3kN load just in a static hang... leaving you a rather small margin of safety. And considering dyneema has virtually zero stretch, you cannot count on any stretch-based partial equalization. Edit: found this, though it seems only girth hitch (a pretty weak knot) was tested in this case alpinist.com/doc/ALP18/news…

Splitting the sling onto two seperate points with clove hitches is considered strong enough by the DAV, if one is real worried or challenged by actually tying a knot like Brian then you can buy the sling already made up in Tech Web from Edelrid bergzeit.de/edelrid-standpl… or others.
The DAV´s opinion on the nescessary strength and tests are on the webpage linked to on page 7 of this thread.

For the record: I can tie the knot just fine in your configuration, Jim.

David Coley wrote: This might be due to a lack of practice :) Remember you only tie the knot once a day, or even once per trip, so not really a pain.

I see how it can be tied just once how Jim shows the configuration (this can also be done with a figure 8, too. The advantage being the BoB is easier to untie at the end of the day). However, what you described - with both strands of each leg engaged to their respective anchor points - I don't see it. Or I should say: it's no different than any other BFK (big fucking knot) master point. The 8 has a slight advantage in horizontally aligned bolts because it takes up less material.

Tying the BoB this way you have 4 strands to do deal with in the knot (as opposed to 2 the way Jim shows), and with the twist induced in how you tie the knot it becomes more troublesome to dress than the figure 8.

Maybe I misunderstood what you were trying to say. Here's what I pictured:

Edit: got clarification from Jim below.

You are misunderstanding it a bit, take a look at banshee belays in David´s book which makes it all clear enough. multipitchclimbing.com/

Oh, I think I see it now. I was following your 3 point anchor images.

So the lower biner goes directly to the loop. Then you clove BOTH strands of the sling to the upper biner, and clip the tail.

Considering your previous stance on extending anchors, I assume you only use this on vertically aligned bolts?

Slings are typically 22kN in loop form. Clove hitching so that only one strand of the loop is loaded hypothetically reduces the strength of the anchor leg to 11kN,...
Edit: found this, though it seems only girth hitch (a pretty weak knot) was tested in this case alpinist.com/doc/ALP18/news…

I see things like this posted on here all the time and it annoys me to no end because it is very wrong. A sling is formed in a loop and that loop is rated to 22kN, so if any point on that loop breaks then the whole loop fails. So the weakest point of the loop is rated for 22kN. Even if you were to cut a sling so that it was not in a loop any more and pull tested the single strand, it would test to 22kN. Just because there are two strands coming from an anchor point does not mean that you add the strengths together to get the strength of the leg. You should only do that if the two strands have been isolated from each other in an appropriate way, tying a single knot (whether a clove, girth, or figure 8 on a bight) is not sufficient. So no, Jim's anchor legs are not rated to only 11kN, they are still rated to 22kN (ignoring knots). If you took a sling rated to 22kN and tied a clove hitch in one side then pulled on the loop on the other side it would still in theory fail at the clove hitch at a force equal to 22kN minus the reduction from the clove hitch, tying a clove hitch then pulling on both strands from the hitch does not magically make the material in the hitch itself hold twice as much.

Also the link that you posted in the edit says that the sling had been cut, so I'm not sure why that is relevant here.

EDIT: The first paragraph is a quote from Patrick Shyvers but MP is not letting me actually put it in the quote box.

Seth Jones wrote: I aim more for volume and distance than even distribution.

That's your problem right there.

Aim for the bushes.

Brady3 wrote: A sling is formed in a loop and that loop is rated to 22kN, so if any point on that loop breaks then the whole loop fails. So the weakest point of the loop is rated for 22kN.

Not quite. In an idealized system (ignoring friction, stress concentrations) each strand in the loop supports 11kN. The loop tension is 11kN, and thus the strand is breaking when it see's 11kn, if the loop fails at a total of 22kN.

You can see this fairly easily if you evaluate the stress in the system.

This is basically the pulley effect.

Now, realistically speaking, most NEW slings break at some higher load than 22kN, and friction may play a small role, creating unequal load distribution across the strands (but this should be mostly mitigated by the test mandrels, I'd expect). Slings are also pulled on 10mm diameter mandrels, which could cause a stress concentration. So realistically a single strand probably holds more than 11kN, but we can't reliably say how much more, so we assume it only holds 11kN.

UIAA 103 describes how you'd test a single tape. UIAA 104 describes how you'd test a sling as a loop. Here are summary sheet's for reference: theuiaa.org/safety-standard…

Brady3 wrote:Slings are typically 22kN in loop form. Clove hitching so that only one strand of the loop is loaded hypothetically reduces the strength of the anchor leg to 11kN,... Edit: found this, though it seems only girth hitch (a pretty weak knot) was tested in this case alpinist.com/doc/ALP18/news… I see things like this posted on here all the time and it annoys me to no end because it is very wrong. A sling is formed in a loop and that loop is rated to 22kN, so if any point on that loop breaks then the whole loop fails. So the weakest point of the loop is rated for 22kN. Even if you were to cut a sling so that it was not in a loop any more and pull tested the single strand, it would test to 22kN. Just because there are two strands coming from an anchor point does not mean that you add the strengths together to get the strength of the leg. You should only do that if the two strands have been isolated from each other in an appropriate way, tying a single knot (whether a clove, girth, or figure 8 on a bight) is not sufficient. So no, Jim's anchor legs are not rated to only 11kN, they are still rated to 22kN (ignoring knots). If you took a sling rated to 22kN and tied a clove hitch in one side then pulled on the loop on the other side it would still in theory fail at the clove hitch at a force equal to 22kN minus the reduction from the clove hitch, tying a clove hitch then pulling on both strands from the hitch does not magically make the material in the hitch itself hold twice as much. Also the link that you posted in the edit says that the sling had been cut, so I'm not sure why that is relevant here. EDIT: The first paragraph is a quote from Patrick Shyvers but MP is not letting me actually put it in the quote box.

Not suprising you keep reading it on the web, it´s correct.
The tape used for 22kN slings is normally 15kN-16kN as a single strand, in theory a sling would then hold 32kN but because tape is tested over a large daimeter clamping drum and a sling is tested between two 10mm pins the strength drops to about 23kN. Cord is tested the same so what we will achieve is lower than the rated strength of the cord.
Full-strength tape for our applications is available, TechWeb from Edelrid for example is 2okN and there are 24kN Dyneema hybrid tapes available from the weavers but not on the open market.

Jim Titt wrote: Splitting the sling onto two seperate points with clove hitches is considered strong enough by the DAV, The DAV´s opinion on the nescessary strength and tests are on the webpage linked to on page 7 of this thread.

I can't read German, unfortunately. However the chart seems to suggest this anchor made of 8mm dyneema is 8.9kN for static loads and 5.3kN for dynamic loads (?)

Also knowing that alt is old and neu is new, this seems to say DON'T clove individual strands of tape anymore...



But, like I said I don't speak German :(

Edit: ALT: Festigkeit grenzwertig translates to OLD: Strength Marginal

Patrick Shyvers wrote: I can't read German, unfortunately. However the chart seems to suggest this anchor made of 8mm dyneema is 8.9kN for static loads and 5.3kN for dynamic loads (?) Also knowing that alt is old and neu is new, this seems to say DON'T clove individual strands of tape anymore... But, like I said I don't speak German :( Edit: ALT: Festigkeit grenzwertig translates to OLD: Strength Marginal

OLD : strength borderline

NEW : recommended

Fig.2: Standard model for stands [anchors?] with at least one solid fixed point : the series circuit . The structure with sling in double strands or climbing rope guarantees sufficient strength

According to google, anyway.

Anyway, considering 7mm cord is only rated to 10kN or so, and I've seen plenty of literature that allows for single strands of it in anchor's like a 3 piece equalette, it seems to be generally considered a non-issue.

In my mind, if it does bust, that's what the redundancy is for. And generally, in order to bust, it will absorb impact, making the successive pieces see much less force. (unlike a bolt, or piece of gear, you know the cord/webbing will take a large force before breaking).

Patrick Shyvers wrote: I can't read German, unfortunately. However the chart seems to suggest this anchor made of 8mm dyneema is 8.9kN for static loads and 5.3kN for dynamic loads (?) Also knowing that alt is old and neu is new, this seems to say DON'T clove individual strands of tape anymore... But, like I said I don't speak German :( Edit: ALT: Festigkeit grenzwertig translates to OLD: Strength Marginal

That's just for two bolts. They say the doubled clove hitch absorbs more energy in the case of primary failure, which I believe is to mitigate "crash with injuries and releasing the brake cable threatening"

And I'm guessing they're talking about a static belay (auto locking) vs a dynamic belay.

Here's a good DAV resource: alpenverein.de/chameleon/pu…

I love the cartoons.

Jim Titt wrote: Not suprising you keep reading it on the web, it´s correct. The tape used for 22kN slings is normally 15kN-16kN as a single strand, in theory a sling would then hold 32kN but because tape is tested over a large daimeter clamping drum and a sling is tested between two 10mm pins the strength drops to about 23kN. Cord is tested the same so what we will achieve is lower than the rated strength of the cord. Full-strength tape for our applications is available, TechWeb from Edelrid for example is 2okN and there are 24kN Dyneema hybrid tapes available from the weavers but not on the open market.

Would you mind sighting your sources on this? Because logic says otherwise. There is still only one strand going around each pin, why does that spot hold more with a bend as compared to the straight lengths between the pins? We know that adding bends to the cord/tape makes it weaker (this is why knots weaken cord/tape) so why do bends over a carabiner make it stronger?

I did try searching for more technical information, but could not find any.