Forums: Climbing Information: The Lab: Re: [blondgecko] Holey dogbones, Batman! (Yet another anchor thread): Edit Log


Jul 13, 2012, 10:18 AM

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Re: [blondgecko] Holey dogbones, Batman! (Yet another anchor thread)
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The anchor systems I have seen to date that have 2 redundant & extension-limited strands bearing the central locker and one or two additional strands closing the loop to lock it in were based on the following 3 systems:
- a single strand folded in an S shape, as in the mexican system discussed in the other thread mentioned here. This has a single locking strand, which means less clutter and weight.
- one huge sling looped so as to create a smaller ring inside a larger one (havenít been able to retrace the original reference on this one so if someone has it, please pitch in): this gives the less efficient two strands for locking or 3 strands for bearing.
- two separate slings, a smaller one inside a larger one as in the holey dogbones system discussed here and other cord-based ones. In addition to the two locking strands this also has the downside of having two sling-closing knots or bar-tacks.

The main advantages of these systems are that:
- only one central locker is required (as opposed to two for the equalette);
- they have the absolute minimum amount of friction (no squeezing of the strands between the 2 lockers when they are loaded, as in the equalette; and no crossings of strands or clutch effect, as in the sliding X).

The main drawback of these systems is that they are not adjustable in the field. Even if knots are used instead of bar-tacks to create the extension-limited central system, moving those knots in the field to adapt to an asymetrical belay configuration is not realistic because it is not just a matter of loosening and shifting the knots. You have to undo them completely, refold the cord in a new S shape or move the smaller loop to one side of the larger one and redo the knots.

My take on these systems is that they are most useful to equalize 4 not-so-bomproof pros, as shown, using a system inspired from one proposed by healyje a long time ago. This is where, in my mind, it becomes critical to have the best possible dynamic equalization with the most even distribution and the least amount of friction, and where it becomes worthwhile to take the time to build a system that will achieve that over all 4 pros. Of course, thereís a good chance that these pros will be all over the place instead of neatly lined up so the system needs long arms to avoid having to add several extra biners and slings to reach the pros. These long arms make undoing and redoing the knots in the field particularly impractical.

This poor field-adjustability led me to switch to the more easily adjustable system shown. It is essentially one long cord sling with two Fig8s delimiting 2 central strands, to which a third locking strand is added once the Fig8s have been shifted to the correct positions for the belayís specific configuration. This locking strand is rethreaded once through each Fig8 and backed-up with cloves on the secondary lockers. As an alternative to clipping these secondary lockers directly through the extension-limiting Fig8s as suggested by healyje, it is possible to set up each secondary arm and its Fig8 as 2 bunny ears: a tiny one for clipping the locker and a long one for the equalized/ extension-limited arms, as described recently by Neoshade.;#2542669

For 3-pro anchors, I actually prefer to use stacked sliding Xs (or in my case, sliding double Xs) because I can take advantage of the friction to achieve a better load distribution than the theoretical 50:25:25. This involves setting up the "50" arm on the same side as the probable load, as I discussed in one of my last posts to Neoshadeís thread. Since I reserve the fancy system for equalizing 4 or more somewhat iffy pros, I carry only one on multipitch trad routes that do not have bolts at the belay stations and park it on the belayerís harness. If I were to come to the end of a pitch and find that I have no choice but to set up this kind of 4-pro belay anchor, Iíd find a way to quickly and temporarily rig it well-enough to bring up the second and Iíd replace it with the fancy one for the next lead. However, Iíve not had to use this system for real yet since I came up with it and thatís just fine by me.

(This post was edited by jktinst on Jul 13, 2012, 12:30 PM)

Edit Log:
Post edited by jktinst () on Jul 13, 2012, 12:28 PM
Post edited by jktinst () on Jul 13, 2012, 12:30 PM

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