What is the strongest way to rig an anchor?

[Iceaxe]

Some good stuff:

QC Lab: Sling Strength in 3 Different Anchor Configurations
A few weeks ago a crew of super badass climbers rolled through the QA lab and one question came up more than just a few times: [i]

[jman]

Interesting....didn't know that.

Thanks for sharing.

[denaliguide]

i'll go with the plain sliding x. anytime you use a knot it creates a weak link.


oops. didn't see the link to the answer on the first read. thought we were taking our best guess and the answer was coming later. just the same it's what i thought.

[oldno7]

The drawback to a sliding X would be it requires a solid anchor point(marginal won't due) if by chance, one side does fail, it creates a huge extension and shock load on remaining anchor point.

[Bo_Beck]

I will first inspect each anchor and determine if one of them is decidedly weaker (or suspect) and if I find one to be very questionable, I would then rig the anchor focal point to favor the stronger of the two anchors. Hence using separate slings or an "8" on a bight to prevent any shockload in the event of one anchor failure. If I feel it necessary to create a floating focal point, and each anchor appears very solid, I would then use a semi-equalizing "X" with knots to prevent a large shockload in the event of an anchor failure.

[Brian in SLC]

i'll go with the plain sliding x. anytime you use a knot it creates a weak link..

Sliding X is nice if you have two bomber anchors (or two really crappy ones), but, if one were to fail, then the shock load you'd get would negate the benefit of using that system. Is pretty good for equalizing bad anchors. I rarely use it. Ditto most folks, I'd think (based on direct observation of a ton of folks in the field). I think it used to be more popular, but, now it seems like folks use three points and equalize (or attempt to) with a web-o-lette or cord-a-lette. For instance, you'd probably never see folks climbing a wall use a sliding x as their anchor point. Sliding X seems to violate the "SRENE" (solid, redundant, equalized, NO EXTENSION).

Hence the configuration of the sliding X with two overhands and a "magic X" to prevent extension.

Interesting to note that all three configurations tested higher than the closed gate strength of a carabiner.

One comment posted, that I kinda agree with, is a figure eight knot will have some dynamic effect on a rapid load into the system (ie, will probably reduce peak loading). A drop test would be fairly interesting.

There's been some pretty healthy debate of climbing anchors on the supertopo website. Some of the stuff is pretty interesting. John Long, who's written several climbing anchor books, and a few other notable folks who do a fair amount of high load type rigging chime in. Its all good in the lab, but, in the field, its never quite optimal. Hence, folks still gettin' killed when their anchors fail.

K to the P in da house! Still kinda dislike the new BD website...takes so darn long to load! Anyhoo, K13, I mean, K12c (ha ha), puts up some great testing stuff, kinda extending the stuff that especially Chris did when QA big cheese at BD.

Good stuff.

-Brian in SLC

[Jaxx]

I think the figure 8 is best because it is easier to get the correct length on each sling assuming you correctly guess the pull direction. I am assuming that most use one piece of webbing at the anchor while canyoneering. Reason being is the article points out that the 8 is about as strong as biners are rated for. Hopefully I will never be putting 5000 lbf on my anchors at anytime while rapping.

Actually I think I have only ever seen overhands, not eights on the anchor in canyons. What is the opinion on that. Is the overhand going to be weaker as the other thread points out it is the weakest knot to tie two ropes together?

[Deathcricket]

Hopefully I will never be putting 5000 lbf on my anchors at anytime while rapping.

I dunno man, I've seen the backpack you carry around.