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JimTitt
Jul 11, 2011, 6:15 AM
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rescueman wrote: If you understand why even the friction of carabiner on sling in a slidingX slows down equalization at the impulse speed of a high factor fall, then you should realize that clove hitches are going to offer tremendously more friction and virtually no equalization under impact. In reply to: The friction in a sliding X or any other setup doesnīt slow down equalisation, it prevents it ever occuring no matter the speed or impact. To have the weaker pieces as backup makes no sense since a force great enough to blow out the strong pieces isn't going to be kind on the weaker pieces. The opposite strategy may make more sense: load the weaker pieces first to absorb some of the force and then use the best pieces for backup. In reply to: Surely it is irrelevant in which order the pieces are loaded and fail, the total of the energy absorbed by the work of ripping/breaking them is the same?
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qwert
Jul 11, 2011, 7:14 AM
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JimTitt wrote: rescueman wrote: If you understand why even the friction of carabiner on sling in a slidingX slows down equalization at the impulse speed of a high factor fall, then you should realize that clove hitches are going to offer tremendously more friction and virtually no equalization under impact. The friction in a sliding X or any other setup doesnīt slow down equalisation, it prevents it ever occuring no matter the speed or impact. In reply to: To have the weaker pieces as backup makes no sense since a force great enough to blow out the strong pieces isn't going to be kind on the weaker pieces. The opposite strategy may make more sense: load the weaker pieces first to absorb some of the force and then use the best pieces for backup. Surely it is irrelevant in which order the pieces are loaded and fail, the total of the energy absorbed by the work of ripping/breaking them is the same?
Cheese, meet tits.
Is it right now?
I am unsure how anchor pieces will behave when they fail, but if we are assuming that they only fail after a high load, they should have absorbed that load, thus leaving less load to be absorbed by the remaining pieces (unless the anchor will extend, and thus create new shockloading).
So it shouldnt really matter which pieces you load first (assuming the weak pieces are stiĺl somewhat strong. If they are bodywheight only, you are going to get into trouble).
But then on the other hand you could also construct an anchor that is meant to fail (partly), so that it will absorb force like a screamer. The piece that gets loaded the first, is the weakest, the 2nd is the 2nd weakes and so on.
Of course thats totally impractical, but it would be really interesting to test/calculate all that stuff.
qwert
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qwert
Jul 11, 2011, 7:17 AM
Post #53 of 60
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rescueman wrote: Or, better yet, use a pre-equalized, fixed, focused anchor using a somewhat dynamic nylon cordalette with double strands to each piece and tied into a master point so the load is as distributed as evenly as possible. Then you don't have to bring your calculator or laptop and spreadsheet to calculate the loading potentials for each anchor.
Also, do you know what happens in the master point? Though that is also a problem with the clove hitch anchor pictured in the OP, it could be much more "problematic" (as in: How the hell does that giant knot get pulled thight?) with a four leg cordalette where you have a knot made up of 8 strands, all somewhat twisted
qwert
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JimTitt
Jul 11, 2011, 7:19 AM
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Good man, itīs a bit early! And Iīm somehow not quite recovered from the IG Klettern annual fest.
Jim
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rescueman
Jul 11, 2011, 4:26 PM
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qwert wrote: ... i would say the clove hitch anchor is easier to tie in such a way that it is equalized that the cordalette.
How is tying a separate hitch on each biner and a master point knot easier than simply clipping a cordelette into each biner, pulling in the direction of load and tying a master point knot?
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JimTitt
Jul 11, 2011, 6:04 PM
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As we have tried to point out earlier (but are unlikely to convince a die-hard stretchy-string man) the only realistic chance of getting anywhere near equalised is to clove hitch a dyneema/Kevlar/Spectra sling in the way the OP shows. Unless you first get all the cordalette legs the same length using draws, chain, steel bars or perhaps even Dyneema the unequal stretch will screw it up.
And as is pointed out, tying that enormous knot screws it all up completely anyway.
Iīve tested just about all the configurations and equalised is not the word that springs to mind and that includes after fitting bearings in all the bends, so much so that as a company we have shelved that idea as unworkable and are going to try another tack altogether.
The good news is none of the ideas seem noticeably worse than the other and no worse than loads of random joining together which is why weīve all survived so long!
Jim
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rescueman
Jul 11, 2011, 8:19 PM
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JimTitt wrote: ...are unlikely to convince a die-hard stretchy-string man
I would use the term "die-hard" only for those too stubborn to learn new and better techniques and likely to die hard on the old ones, not those who have investigated the "new and improved" models and choose to stick with the "tried and true" because it really does work just fine and has for a long time.
Until relatively recently, Rocky Mountain Rescue, the oldest Mountain Rescue team in the US of A, used 3-strand Goldline rope because they'd been using it for 50 years with zero failure. Are they "die-hards" or just reasonable and smart? No one died on their system.
In reply to: And as is pointed out, tying that enormous knot screws it all up completely anyway.
In reply to: Iīve tested just about all the configurations and equalised is not the word that springs to mind
I use the term "fixed, focused load-sharing anchor system" to describe a pretensioned and pre-directed multi-point anchor.
As for that stretchy-string comment, I don't have John Long's new anchor book but this was apparently a quote from page 192:
"Considering the cordelette equal riggings, slight differences are noted among the sling materials, though substantively they appear to perform equally well. A different conclusion is reached when examining results from the cordelette unequal configuration. Findings show that nylon or Perlon provide better equalization than Spectra or high-tensile-strength cord, in the case of a cordelette with unequal legs. This suggests that for equalization purposes, nylon is the preferred material to make cordelettes. Though these results are based on limited data, it appears that for a cordelette unequal setup, sling material does matter."
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JimTitt
Jul 11, 2011, 9:22 PM
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But we were talking about equalising, well you were In reply to: "Or, better yet, use a pre-equalized, fixed, focused anchor using a somewhat dynamic nylon cordalette with double strands to each piece and tied into a master point so the load is as distributed as evenly as possible."
To join a load of bits of gear together I would use anything suitable to hand and normally use the climbing rope and some slings. My way is better because it is focused(on me) pre-tensioned (by me) has inertial damping (from me) and requires no knowledge at all! So that will be a Beer-Gut Inertially Stabilised Age-related Macular Degeneration Slighly Focused Belaying System using my Whatever Iīve Got Left Over Belay Kit.
Jim
(This post was edited by JimTitt on Jul 11, 2011, 9:23 PM)
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rescueman
Jul 11, 2011, 10:15 PM
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JimTitt wrote: But we were talking about equalising, well you were In reply to: "Or, better yet, use a pre-equalized, fixed, focused anchor using a somewhat dynamic nylon cordalette with double strands to each piece and tied into a master point so the load is as distributed as evenly as possible." Since you (wisely) donīt trust the word equalised...
You misquoted me.
rescueman wrote: The word I don't trust is "equalizing"
"...so the load is as distributed as evenly as possible." Distributed evenly is not the same as self-equalizing or equalizing by faith or miracle, or...
Anyway, did you all know that God prefers 3-strand rope?
God wrote: "Though one may be overpowered, two can defend themselves. A cord of three strands is not quickly broken." - Ecclesiastes 4:12 |
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