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oldnutz
Trad climber
OAKLAND
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Sep 24, 2014 - 12:55pm PT
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Like in the picture below from prrdylady. The tests done for the DAV show that with dynamic loads on thinner cord clove hitches fail at lower levels than previously thought. The DAV have a criteria of requiring (or expecting) a single point on a belay to hold 6kN (in case it is taking the full load) and with most cord and tape the clove fails below this. From memory 8mm was the only one that held from the ones they tested. JimT: when you say "fail" does that mean the hitch slips with no friction, or that it slips with some friction?
I'm using 7mm nylon or 6mm tech cord for my equalette, and I'm using cloves on all 4 strands. Typically I would have no more than a foot of slack rope between the cloves on each side.
Since it's impossible to exactly equalize the two strands, one hitch is going to take most of the force until it starts to slip, at which point the other hitch will start to absorb some force as well (and of course the other side of the equalette is going to be similarly loaded and absorbing some of the force).
Unless you're asserting that when a clove hitch slips it goes from static to zero friction, this is not analogous to a typical "extension" scenario where a piece blows and the load freefalls onto the next piece. So even if there's quite a bit of slack in the equalette, it doesn't seem that the knot slipping would be the same situation as a piece blowing. In fact there is little to no extension even if an entire side blows out with this rig.
While this scenario is very specific, it does represent the majority of trad anchors I build, and I've been very fortunate to never catch a leader fall directly on the anchor to see what happens. All kidding aside, if this is a dangerous rig then I'll stop doing it, but my back-of-the-napkin noodlings leave me hopeful this is a safe rigging method.
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RyanD
climber
Squamish
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Sep 24, 2014 - 01:38pm PT
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Bump spam
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BG
Trad climber
JTree & Idyllwild
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Sep 24, 2014 - 03:13pm PT
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In all the testing we've seen/done over the years, it seems that problems arise in proportion to the elasticity of a given piece in the roped safety system. The more stretch, the less the poroblems. Tech webbing and cordage is "stronger than steel," but it gives so little that this often compromises a system built to produce "soft" falls by way of the inherent stretch of the components.
Long story short, the old nylon is heavier and bulkier but in many regards is still the go-to stuff in rock climbing.
JL
Well said. Ten years ago when I was training to become an AMGA Instructor/Examiner, all my mentors had skinny Dyneema double runners for critical applications like building a redundant extended masterpoint or extending a rappel device. Now the same dudes (and myself) all carry big, fat, old school nylon slings.
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maldaly
Trad climber
Boulder, CO
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Sep 24, 2014 - 04:11pm PT
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Okay, I'll pitch in here.
First of all, let's geek out on fixing problems in climbing that actually kill and maim people. If you look at the accident stats published in ANAM you have to go pretty deep to find a single accident in which belay anchor failure ever hurt or killed people. I think there have been three, none of which would have been prevented by any of the discussion in this thread. Two of them were cordalletted and master-knotted SRENE anchors which were loaded in a direction that was not anticipated for by the anchor builder. The third was from broken tat at the Red.
Second, I tell people in my clinics about the three rules of anchor building. Bomber, Bomber, Bomber and Multi-directional. Some bright young attendee always points out that I had, in fact, listed four. Thanks for paying attention, now back to BBBM. That's right, if you want to be uber-safe, place three bomber anchors, two of them should be for a downward pull and the third, tensioned to the other two in the opposite direction so the whole sh#t pile won't pull out when the belayer gets pulled up or to the side when the next leader falls. Imagine that...
Third, getting back to ANAM, looks at what causes the majority of accidents. It's getting stuck, benighted, stormed or slow, setting up a cascade of events that you can no longer control. All that sh#t happens because you weren't moving fast enough (re: Donini) because you were bogged down trying to construct, then arguing about, a SRENE anchor.
Climb safe,
Mal
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BG
Trad climber
JTree & Idyllwild
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Sep 24, 2014 - 04:45pm PT
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If you look at the accident stats published in ANAM you have to go pretty deep to find a single accident in which belay anchor failure ever hurt or killed people.
Good point. In pure rock climbing the number one accident is leader falls. Entire books are written on the subject of anchors (JL and I just finished another one- Climbing Anchors Field Guide, 2nd edition) but the bottom line is that anchors rarely have to absorb much force at all- it's that single piece that the leader falls on that must withstand a big impact force.
When it comes to anchors, people like to go right to worst case scenarios and work back from there. But there are instances, albeit rare, where crafty rigging might have saved the day.
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Mark Force
Trad climber
Cave Creek, AZ
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Sep 24, 2014 - 05:23pm PT
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Beautiful discussion. Thank you everyone!
;-)
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BG
Trad climber
JTree & Idyllwild
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Sep 24, 2014 - 07:24pm PT
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BG
Trad climber
JTree & Idyllwild
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Sep 24, 2014 - 07:33pm PT
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Nope, it's the real deal. Fixed lines (a couple sets) at the Sickle Ledge anchor, Nose Route, El Cap, 1983, before anyone ever heard of SRENE or a cordelette!
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JimT
climber
Munich
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Sep 24, 2014 - 11:59pm PT
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JimT: when you say "fail" does that mean the hitch slips with no friction, or that it slips with some friction?
I meant fail as in the material breaks at that point.
Iīve had to cut enough clove hitches off gear to know that expecting them to slip is optimistic, expecting the slip to provide a dynamic element in a system is wild optimism.
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oldnutz
Trad climber
OAKLAND
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Sep 26, 2014 - 10:28am PT
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I meant fail as in the material breaks at that point.
Thanks JimT...I just want to understand the mode of failure...so in my example of using 6mm tech cord in the equalette, the cord breaks at the clove hitch under much lower force than would be expected?
If so, in my 4-point anchor with "somewhat" equalized strands, the equalette itself could fail well before an individual piece? That would be disheartening :(
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oldnutz
Trad climber
OAKLAND
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Sep 27, 2014 - 01:09pm PT
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Thanks Locker...
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Allen Agopsowicz
Trad climber
BC
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Sep 27, 2014 - 03:48pm PT
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I've had a parachure company sew me some two-point dynamically equalizing slings with extension limiters. They are expensive to make so they might not ever get to the market. A few guides and industry insiders have seen them and the next batch will include their recommendations. Destructive testing revealed a 3200 lb. breaking strength per arm so I'm guessing the theortical limit of 6400 lbs break is probably true for the system. The construction method is under industrial patent pending and the equalization range is nearly 90 degrees. There are limitations of course, three point systems require a brain to set up, and the placement of the anchors has a measured effect on the equalization range. Otherwise, perfect for TRs and newbies who haven't a clue how to build an anchor.
The holy grail remains the dynamic, dynamically equalizing anchor system.
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JimT
climber
Munich
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Sep 28, 2014 - 12:32am PT
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The holy grail remains the dynamic, dynamically equalizing anchor system.
Depends on your religious bent I guess, for me itīs two or three bombproof anchors you can use any way you like.
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overwatch
climber
Arizona
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Mar 20, 2016 - 09:55am PT
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Not really an article but a great primer, especially for kids
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healyje
Trad climber
Portland, Oregon
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Mar 20, 2016 - 10:15am PT
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Two bolts? TR? Two draws, clip the rope, climb.
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healyje
Trad climber
Portland, Oregon
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Mar 20, 2016 - 10:26am PT
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15 hours of which is deciding which end of the draws goes on the bolts...
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Prod
Trad climber
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Mar 20, 2016 - 10:44am PT
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"Two bolts? TR? Two draws, clip the rope, climb."...
Mostly overkill but if we're running sport climbing laps. I sometimes use a locker draw for one of the anchors.
Prod.
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jeff constine
Trad climber
Ao Namao
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Mar 20, 2016 - 12:25pm PT
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Slings.
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rgold
Trad climber
Poughkeepsie, NY
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Mar 20, 2016 - 01:33pm PT
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Some people seem to equate the ability and interest in having a nuanced technical discussion with an inability to construct an anchor in the field in a timely fashion.
It may be that relative beginners with limited practical field experience get bogged down in considerations of little practical value after reading too many of these technical discussions. And I suppose that some climbers get trapped in an arrested state of development and never emerge from the thrall of theoretical exhortations about equalization and redundancy.
But there isn't necessarily any link between the two activities, one primarily an intellectual exercise conducted indoors at one's leisure, and the other an active application of ingrained knowledge under conditions imposed by the environment. It is possible to both know trigonometry and build anchors with speed and efficiency. Just sayin...
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