Three point anchor - The Saga Continues

Kyle Tarry wrote: Keep in mind that half ropes are tested with a different load mass than singles and twins, so you can't directly compare them.

Of course; that's why I mentioned triple certification: the test results for single and twins are comparable.

I am only on page 6 of this 8 page behemoth, but I didn't see any mention yet of strength...

Partly because pessimism, and partly because we know really good equalization is a pipe dream, we can't just add together the strength of all three pieces.

If you build your anchor with cord, and only a single strand going to each piece, you can be considerably compromising the strength of the system.

If you use 7mm cord, taking off 33% for the knot, any one leg is only good to 7kN.

If you use 6mm cord, that drops to 5kN. You plus your follower is already 2kN...

The traditional cordalette anchor, with two strands per leg, should be more like 14kN (7mm) or 10kN (6mm) per leg

(Perhaps not important, but it pops into my head that Black Diamond recommends gear 4kN and below is for direct aid only)

A full 20kN for your triple redundant hanging belay isn't really needed (and in fact may not be possible, as even big nuts and cams top out around 15kN) but knowing really good equalization is very hard, are we really OK with 7kN, or 5kN, per leg?

It is worth noting that rgold's single-leg-style diagram is performed with climbing rope, not cord.

I actually always tie my anchors just like eric moss suggested however I also want a rope masterpoint so I will build a quick moeby knot out of the climbing rope. It's redundant and easy to tie!

instructables.com/id/Moebiu…

Patrick Shyvers wrote:I am only on page 6 of this 8 page behemoth, but I didn't see any mention yet of strength... Partly because pessimism, and partly because we know really good equalization is a pipe dream, we can't just add together the strength of all three pieces. If you build your anchor with cord, and only a single strand going to each piece, you can be considerably compromising the strength of the system. If you use 7mm cord, taking off 33% for the knot, any one leg is only good to 7kN. If you use 6mm cord, that drops to 5kN. You plus your follower is already 2kN... The traditional cordalette anchor, with two strands per leg, should be more like 14kN (7mm) or 10kN (6mm) per leg (Perhaps not important, but it pops into my head that Black Diamond recommends gear 4kN and below is for direct aid only) A full 20kN for your triple redundant hanging belay isn't really needed (and in fact may not be possible, as even big nuts and cams top out around 15kN) but knowing really good equalization is very hard, are we really OK with 7kN, or 5kN, per leg? It is worth noting that rgold's single-leg-style diagram is performed with climbing rope, not cord.

Good point. I guess the shitrope will need thicker cord. I'm definitely leaning toward the standard cordelette model at this point. I'm also considering going HAM with a rigging plate.

Ouch! I just went through all 8 pages, the simplicity of bouldering sounds really good right now :)

Troll?

Eric Moss wrote: Good point. I guess the shitrope will need thicker cord. I'm definitely leaning toward the standard cordelette model at this point. I'm also considering going HAM with a rigging plate.

Rigging plates aren't really my jam, and veteran climbers might sneer, but they can be pretty light & cheap. Probably lighter than a special fancy anchor setup. Rock Exotica makes a 3-hole plate, 36kN, for 50g & $27.

JRegus wrote:Troll?

No not a troll. I enjoy all types of climbing, hell one time I did an FA of a small runnel of ice that just formed, when I topped out I found that it was grey water runoff from a mobile home. But I actually do love the simplicity of bouldering, so no not a troll.

I do think of anchors as links of a chain, with every link being a potential failure point, so the fewer links the better.

Tony A. Davis wrote: No not a troll. I enjoy all types of climbing, hell one time I did an FA of a small runnel of ice that just formed, when I topped out I found that it was grey water runoff from a mobile home. But I actually do love the simplicity of bouldering, so no not a troll. I do think of anchors as links of a chain, with every link being a potential failure point, so the fewer links the better.

Not you Tony. The original post.

I think I have this figured out.

Rick Blair wrote:I think I have this figured out. Bomber!

YASSS, 4/4!!!

4 point redundant, check.

Personal tether? Two hands and ankle straps. Checkity

Naughty bulge? Increasing steadily. Check it

Block leading, no problems. She's having a great time

Rick Blair wrote:I think I have this figured out. Bomber!

Finally!! Someone figures out the highest power point for a given v angle.

Bomber indeed.

20 kN wrote: That is your "simpler, lighter, easier" option...? You're normally fairly spot on but you missed by a mile here. That anchor is way too complicated and totally unnecessary. I also should not have to mention to you that tying knots in Dyneema drastically reduces the strength of the material (by as much as 50%) and you're triaxialy loading your master-point biner using a biner that is especially weakened by tri loading. That creation looks like something out of the Unbelievable Anchors series that Climbing Mag hosts. The alpine equalette is a much better option: Or just the "huge f#cking knot" standard anchor that anyone can setup in 10 seconds and climbers have been using since the beginning of the sport:

To stand up for Jim (although he's more than capable of standing up from himself) - you have to understand the location. He is talking about a part of the world where 1. people don't carry cordelettes, 2. belays tend to be 2-point and bolts.

The approx 120cm sling with a BoB is then very good indeed. It can be undone even by children after loading, and gives a "powerpoint" up high, right by the bolt, which is what you need if you are pulling two ropes through a guide plate all day for a living.

For three or more points, there are better ways, yes, but if you were only used to doing 2-point this way, and only had a few slings it makes more sense than it might look.

By the way, the BoB is only undone at the end of the day, the carabiners and even the reverso can be carried in place on the sling, and the whole thing carried over the shoulder, so it is more plug-and-play than an overhand knot approach for bolted multi pitch.

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…

This could easily be linked to the "Is it OK to pass a slower party" thread because this fuster cluck train of thought is the main component of that.

Jim Donnini would weep. Seriously. Don't make him do that.

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…

Good point. 1 inch webbing, baby - 17.8 KN strand strength.

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, .....

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

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.

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.

David Coley wrote: To stand up for Jim (although he's more than capable of standing up from himself) - you have to understand the location. He is talking about a part of the world where 1. people don't carry cordelettes, 2. belays tend to be 2-point and bolts. The approx 120cm sling with a BoB is then very good indeed. It can be undone even by children after loading, and gives a "powerpoint" up high, right by the bolt, which is what you need if you are pulling two ropes through a guide plate all day for a living. For three or more points, there are better ways, yes, but if you were only used to doing 2-point this way, and only had a few slings it makes more sense than it might look. By the way, the BoB is only undone at the end of the day, the carabiners and even the reverso can be carried in place on the sling, and the whole thing carried over the shoulder, so it is more plug-and-play than an overhand knot approach for bolted multi pitch.

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.

This entire anchor takes me about 20 seconds to build, it will hold 22kN limited by the strength of the PAS, and it meets the requirements of SERENE. Further, it requires absolutely no additional equipment over what I normally bring anyway. It's literally as simple as connecting my PAS to a bolt, throwing a draw over to the other bolt and setting the GriGri up on one of the PAS loops to belay the second. Thrown in the rope on a clove for more redundancy if you wish. For belaying the leader, I just take the GriGri off the PAS and throw it on my belay loop.

If I am rappin' a route, I'll use a trad draw connected to my belay loop as a second sling for redundancy.

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.

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.