|
rgold
Mar 15, 2006, 7:23 PM
Post #126 of 164
(31354 views)
Shortcut
Registered: Dec 3, 2002
Posts: 1804
|
OMG, I did V8 in the 60's? Is that really true John? I find myself in the sixties once again, only now they are MY sixties, and it is a very rare day indeed when I can get up a V4. I just look at V8's and think about the trip to the emergency room that would result from my trying the first move.
I think I like the other 60's better...
More seriously guys, cut Craig some slack here. I'm afraid my critical post could be part of a pile-on that is typical enough of life on the internet, but doesn't really help the discussion of equalized anchors any. Lets get back to the elusive question about whether it is possible, in any practical sense, to fully equalize a multiple-piece anchor and douse the flame wars before they start.
|
|
|
|
|
vivalargo
Mar 15, 2006, 7:48 PM
Post #127 of 164
(31354 views)
Shortcut
Registered: Nov 26, 2002
Posts: 1512
|
One problem in particular, Rich, involving a heel hook up and right and a two finger pull through on a slanting hold pasted to a 120 degree wall. Can't remember the name (we knew it as the Goldstone problem). Bachar is the only other guy I ever saw do it. I probably did it five times in ten years--and not for lack of trying.
Per Scott C. For the record I learned more from Scott about forces and fall factors than I learned from anyone else. His presentational style doesn't bother me at all. His knowledge is invaluable, as is his basic message: the highest anchor in the roped safety system always sustains the greatest loading. All the more reason to make sure the belay anchor is never your "highest anchor" during a fall.
JL
|
|
|
|
|
healyje
Mar 15, 2006, 8:34 PM
Post #128 of 164
(31354 views)
Shortcut
Registered: Aug 22, 2004
Posts: 4204
|
I do think this thread is really more about another climbing author unnecessarily trying to establish an substantive peer / authoritative presence in the matter here on RC. But I'll step back from the brink and say as Craig's solution is a solid contribution to the whole of the discussion relative to exploring the boundary of solution sets exhibiting a clean separation of extension and equalization. That in turn has contributed (in my case) to much fuller understanding of the advantages of, and appreciation for, mhabicht's rig which incorporates both within a single cord design.
|
|
|
|
|
fingertrouble
Mar 16, 2006, 3:59 AM
Post #129 of 164
(31354 views)
Shortcut
Registered: Sep 11, 2005
Posts: 54
|
You guys, and Richard, undoubtedly know that I had no intention of dissing Richard. I actually like the guy and I certainly value his contributions to this forum. We may even have climbed together at Devil's Lake, back in the day. I just wouldn't guess that he's on the list of "famous climbers" that was implied.
Tough crowd here.
|
|
|
|
|
fingertrouble
Mar 16, 2006, 4:13 AM
Post #130 of 164
(31354 views)
Shortcut
Registered: Sep 11, 2005
Posts: 54
|
No, colkurtz, you might be among those who actually "get it."
In my view, equalization is just one tool of competent anchor building, yet somehow it overshadows the others and, worse, overshadows the fundamental requirement to understand the direction of forces (including non-fall forces) that will impact the anchor and to design the anchor so as to accommodate them.
This observation hasn't been totally missing from these discussions, but it's only rarely mentioned. That might be because here we're focused on just the equalization subset of the anchor building tool set. Still, many climbers will wrongly conclude that the correct approach is simply to throw together several placements and attempt to equalize them. "To a man with a hammer, everything looks like a nail." Including his thumb. There might be a different slant to this if a thread were started, "What's the best way to conceptualize anchor building?"
But don't totally reject equalization, either. More than likely, in the general case, you'll mostly focus on achieving redundancy ("If this piece fails, what piece will then take over and what then be will the direction of applied force?"), but well-placed pieces, equalized, can achieve that, too. If you minimize any resulting untoward extension and unfortunate directions of loading should any placement fail, you'll also approach the optimum setup in terms of redundancy and equlaization. An equalized rig also offers the benefit of lowering the jerk on each piece when holding a fall (not a bad thing). If you can get good equalization for cheap, then you'd want to use it--and that's what we're looking for: good equalization for cheap. The most important characteristic, however, is that equalization (or redundant joining) of well-placed pieces decreases your dependency on any single one of them, thus increasing your odds of having a secure anchor when you take a whipper on it.
|
|
|
|
|
vivalargo
Mar 16, 2006, 5:57 PM
Post #131 of 164
(31354 views)
Shortcut
Registered: Nov 26, 2002
Posts: 1512
|
The reasoning behind cooking up the equalette was to accomplish what Scott is saying here--to provide a high degree of equalization and -- with it's sliding master point -- to allow a workable degree of off axis loading. People have now taken the basic equalette master point and two arm configuration and cooked up a couple alternatives, and I hope more are forthcoming.
Also, the basic equalette configuration took account of two other things: first, the no-extension part of SRENE. Testing showed that so long as you had limiter knots in the rig, you were not going to encounter any terrible load multiplication if one piece blew.
Lastly was the issue of redundancy. As I've said elsewhere, when I looked closely at the issue of redundancy (in light of possible "cascade anchor failure") I realized that redundancy and equalization were--or at any rate, should be--two sides of the same coin. The basic credo of redundancy is that we never hang our lives on one piece of gear. That means in any belay anchor, potential falls should never be absorbed on one primary anchor--which largely happens with a cordelette (w/ unequal arms). The fact that the cordelette has no extension means that this is merely a backed-up system, not a "redundant" system in the way that I'm suggesting. If you don't want loading to be sustained by one piece (true redundancy), you have to have some equalization over at least two pieces, and load distribution going to more pieces if necessary.
In this sense equalization and redundancy go hand in hand.
JL
|
|
|
|
|
g-funk
Deleted
Mar 16, 2006, 7:25 PM
Post #132 of 164
(31354 views)
Shortcut
Registered:
Posts:
|
Largo,
I have been following both of these threads for quite some time now, and all I can say is that I'm looking forward to the book coming out.
Until then it seems like I've learned 3 things.
1. Using an Alpine Equalizer isn't really as unsafe (from an extension standpoint) as I had thought in the past.
2. A cordelette with a knot to prevent extension isn't really as safe as I had previously thought.
3. I need to learn more about body stance and belay position.
Thanks for all the input and discussion, and once again, looking forward to the book.
|
|
|
|
|
lambone
Mar 16, 2006, 7:56 PM
Post #133 of 164
(31354 views)
Shortcut
Registered: May 1, 2003
Posts: 1399
|
My post is in response to the first post in this thread, I haven't read any of the other 9 pages....and don't care to.
After you have used 2 cordelettes in each anchor (meaning you must now carry 4 cordelettes on a multi-pitch route), what do you use top escape the belay in a emergency self-rescue situation?
I am in Greg Barnses camp. I will trade off less equalization for no extension.
|
|
|
|
|
healyje
Mar 16, 2006, 7:56 PM
Post #134 of 164
(31354 views)
Shortcut
Registered: Aug 22, 2004
Posts: 4204
|
g-funk,
Yeah, the stance aspect of belaying is a really underconsidered aspect of climbing that more or less has gone out the window as a conscious practice. I, and other old timers I suspect, try to not depend on an anchor anymore than I have to. Sometimes it is unavoidable, but in general and regardless of the anchor quality I try to see if I can't have my stance bear the brunt of a fall - I view stance as the first line of defense. Part of that involves how and where the rope runs. For instance, sometimes when belaying a second either sitting or standing I'll brace my foot so I run the rope over the top of my lower ankle (hightops) so that any fall will lock my foot/leg in place. I pay very specific attention to how I brace and lean various parts of my body and the collected whole relative to the direction of the load in any fall. Even when you are wholly dependent on an anchor, stance still counts as this all goes hand-in-hand with a belayer being situated such that you don't get slammed into the rock in front of you.
That's all a pretty random taste of the subject but I do feel strongly that stance is a very important aspect of any belay...
|
|
|
|
|
lambone
Mar 16, 2006, 8:20 PM
Post #135 of 164
(31354 views)
Shortcut
Registered: May 1, 2003
Posts: 1399
|
In reply to: g-funk, Yeah, the stance aspect of belaying is a really underconsidered aspect of climbing that more or less has gone out the window as a conscious practice....
what? really? oh shit!
:lol: :roll: :?:
|
|
|
|
|
lambone
Mar 16, 2006, 8:22 PM
Post #136 of 164
(31354 views)
Shortcut
Registered: May 1, 2003
Posts: 1399
|
In reply to: g-funk, Yeah, the stance aspect of belaying is a really underconsidered aspect of climbing that more or less has gone out the window as a conscious practice....
what? really? oh shit!
:lol: :roll: :?:
|
|
|
|
|
knudenoggin
Mar 16, 2006, 11:05 PM
Post #137 of 164
(31354 views)
Shortcut
Registered: May 6, 2004
Posts: 596
|
In reply to: If you have an anchor where outer pieces are at about 45 degree angles then you must consider that part of the angle into the equation. In my calculations if the total load is 10, then the load on the middle piece is 50% of that or 5. On the other pieces it is 25% * 10/cos 45 or 3.5 Now the effective loads are 3.5, 5, 3.5 or in percentages: 30%, 40%, 30% So it isn't as bad as first appears. Note though with smaller angles the load will increase on the center piece.
No, this is funny: you think you've improved things by increasing the force
on some anchors?? What the anchors feel isn't percentage, but absolute force,
and in your analysis that center point stays with 5--it's just that now the others
are feeling more load by virtue of angle. (But my head hurts in trying to figure
what occurs with frictionless sheaves for the cord in, say, CraigShort system
--the aggravating/increasing-force factor of wide angles must get distributed?)
One problem I see w/mhicht's structure is the rigging to limit extension--e.g., as
pictured, all that slack cord at extreme left is going to yield extension if the partner
anchor point on right fails. Yeah, one could knot it or tie off the anchors with
2 Half-hitches, taking care to limit slack appropriatley.
Someone maintained that the cordelette equalized as set (but not off-angle),
but recall that JL's (and other's) testing has shown that in fact they don't.
As for CraigShort, I'd like to see actual equalization data for any off-angle
fall: in a book by a like-named author, I believe the use of a 'biner as a pulley
sheave is given as 60% efficient, so how all that rope around the powerpoint
is to shift to equalize I'd think will suffer similar (in)efficiency--far from "Perfect".
--though perhaps amply well distributed, which is good enough, as some note.
I continue to miss any consideration of the ELET structure I introduced long ago--cf
http://i2.tinypic.com/qwx3ro.jpg
Instead of the perhaps overly clever (?!) knotting shown in a single-strand
solution of the image (small ELET is of Spectra thin 60cm tape sling),
one can make the 'biner-sliding V of each half with a 60cm tape sling doubled
("dogboned"? so to speak), and tie each end with a Sheet bend (actually the
loading by the sling makes it a "Becket Hitch"--same geometry), having
to tie the cross part (which contains the sliding 'biner and fixes extension)
to the 2nd bight-end of the sling in reverse (so, wrapping around the end bit
and tucking out through the eye).
Using 2 pieces of cord--perhaps doubled 7mm (as does cordelette)--, the structure
could probably be pre-tied for deployment; in any case, making sizing adjustments
by working material through the simple Sheet bends as needed wouldn't be hard.
(One might e.g. prefer to clip in the bight end of a doubled cord, adjust to
position the sling, and only tie off the paired ends of the cord.)
Note that the sling knotted (Overhand loops shown; clove hitches possible)
at the belayer end as shown hold with a single strand; one could either use two
such slings (both knotted, i.e., same size), or just back up this one with an
unknotted sling clipped through the 'biners (which would only offer again a single
strand of load holding).
This ELET system has 3 'biners that will slide to equalize, and this
coming over slick Spectra tape--not the back'n'forth looping of material through
various 'biners at both ends (anchor & belayer) of some other systems, such
as CraigShort. It is like MHicht's in this regard.
RGgold doesn't see this working for vertical placements, but I don't follow his
reasoning. I will note that one could bias the positioning of the limiting knots
to anticipate adjustment being only in one direction.
*knudeNoggin*
|
|
|
|
|
healyje
Mar 17, 2006, 12:45 AM
Post #138 of 164
(31354 views)
Shortcut
Registered: Aug 22, 2004
Posts: 4204
|
In reply to: One problem I see w/mhicht's structure is the rigging to limit extension--e.g., as pictured, all that slack cord at extreme left is going to yield extension if the partner anchor point on right fails. Yeah, one could knot it or tie off the anchors with 2 Half-hitches, taking care to limit slack appropriatley. *knudeNoggin*
Actually if you check out the discussions and pictures of his rig in the other thread I think you'll find that the fact you have complete control over managing extension is the very best aspect of mhbight's rig. It gives you complete control to balance and manage both extension and equalization while maintaining them in isolation from one another.
|
|
|
|
|
rgold
Mar 17, 2006, 1:05 AM
Post #139 of 164
(31354 views)
Shortcut
Registered: Dec 3, 2002
Posts: 1804
|
In reply to: In many of the 3 piece anchors some people don't like them because they are in 25% 50% 25% configurations. With the middle piece having 50% of the load. My theory is that this does not really matter that much. If you have an anchor where outer pieces are at about 45 degree angles then you must consider that part of the angle into the equation. In my calculations if the total load is 10, then the load on the middle piece is 50% of that or 5. On the other pieces it is 25% * 10/cos 45 or 3.5 Now the effective loads are 3.5, 5, 3.5 or in percentages: 30%, 40%, 30%
If the system uses pulley-type equalizers, then the 1:2:1 distribution holds regardless of arm angle. If you think the 1:2:1 distribution matters, it really does matter.
The kind of calculation you are talking about only applies to fixed master point set-ups like the tied cordelette. But the situation for more than two strands is rather subtle and cannot be done by just assuming that the middle strand takes half the load.
The engineers refer to such configurations as "statically indeterminate," because there are fewer equilibrium equations than there are variables and so there is a whole subspace of solutions. (In the case of a perfectly symmetric three-arm cordelette, you end up with one equation in two unknowns.) If the structure in question is made of rigid arms (i.e. a cordelette-shaped truss) then additional equations can be obtained by insisting that there must be no net torque at any anchor point. But with cord, the arms don't exert any torque on the anchor pieces and so the additional equations must come from Hooke's law applied to the arm deformations under loading.
I think that the middle strand can, in principle, bear any proportion of the load from 1/3 up, and so there must be some angle between the outer strands when the middle strand takes half the load as you assumed. I don't know whether or not that happens at a 90 degree angle between outer strands, but in any case none of this is relevant to the case of an equalized anchor.
|
|
|
|
|
knudenoggin
Mar 17, 2006, 1:58 AM
Post #140 of 164
(31354 views)
Shortcut
Registered: May 6, 2004
Posts: 596
|
[quote="healyje"]In reply to: Actually if you check out the discussions and pictures of his rig in the other thread I think you'll find that the fact you have complete control over managing extension is the very best aspect of mhbight's rig. It gives you complete control to balance and manage both extension and equalization while maintaining them in isolation from one another.
extension, otherwise unused--you're running either a heavier cord, or lowering
your safety margin.
In my system of ELETs, tied as verbally illustrated with paired thin cord using
60cm HMPE tape slings for 'biner slide, all of the cord serves in holding the load,
but for the small spanner portions between the tie-offs of each dogboned sling
end (which effectively makes that "triangle" an eye if one side fails, and thus
limits extension pretty greatly.
*kN*
|
|
|
|
|
healyje
Mar 17, 2006, 2:46 AM
Post #141 of 164
(31354 views)
Shortcut
Registered: Aug 22, 2004
Posts: 4204
|
knudenoggin,
My apologies, but another long stretch of programming has left me particularly dense today and I'm just not getting it from the earlier text or this one + drawings. Got a photo or drawing illustrating a completed rig. Again, sorry to be so dense today but I'm tired of staring at screens...
|
|
|
|
|
fingertrouble
Mar 17, 2006, 2:53 AM
Post #142 of 164
(31354 views)
Shortcut
Registered: Sep 11, 2005
Posts: 54
|
In reply to: Hooke's Law makes my brain hurt. In reply to: The engineers refer to such configurations as "statically indeterminate," because there are fewer equilibrium equations than there are variables and so there is a whole subspace of solutions.
The 3-leg analysis is important, because that's probably the most common application. Right now people on the Improved Sliding X thread (maybe even here) are enthusing about 4-placement solutions, but I fear there will be rough sailing when it comes to either designing an effective 3-placement solution or in understanding that when even the best of the 4-placement designs (possibly mhabicht's latest irrespective of complexity) lose one placement, they place twice the initial load (half the total load) on the surviving placement of that side's pair.
Richard, please check your PMs and if you don't see one from me, please let me know so we can get out of this inefficient PM business. Thanks.
Craig
|
|
|
|
|
healyje
Mar 17, 2006, 3:06 AM
Post #143 of 164
(31354 views)
Shortcut
Registered: Aug 22, 2004
Posts: 4204
|
Adapting an equalette-based solution to three points isn't that big a deal, just put two strands on the best piece of the three...
|
|
|
|
|
vivalargo
Mar 17, 2006, 3:28 AM
Post #144 of 164
(31354 views)
Shortcut
Registered: Nov 26, 2002
Posts: 1512
|
In reply to: Adapting an equalette-based solution to three points isn't that big a deal, just put two strands on the best piece of the three...
We're going to do some testing of this configuration over the next week or so. I.e.--one arm conecting an anchor point, and both strands on the other arm connected to one anchor each.
JL
|
|
|
|
|
healyje
Mar 17, 2006, 4:18 AM
Post #145 of 164
(31354 views)
Shortcut
Registered: Aug 22, 2004
Posts: 4204
|
John,
Glad to hear it, I think we'd all like to see the results...
|
|
|
|
|
knudenoggin
Mar 17, 2006, 4:50 AM
Post #146 of 164
(31354 views)
Shortcut
Registered: May 6, 2004
Posts: 596
|
In reply to: Right now people on the Improved Sliding X thread (maybe even here) are enthusing about 4-placement solutions, but I fear there will be rough sailing when it comes to either designing an effective 3-placement solution or in understanding that when even the best of the 4-placement designs (possibly mhabicht's latest irrespective of complexity) lose one placement, they place twice the initial load (half the total load) on the surviving placement of that side's pair.
total load/force? --will it be better to have more heavily loaded it (or will that
heavier, pre-extension load have worked it more nearly loose?!)
Consider: 1,200# load (you see the total chosen for easy division by 3 & 4 :wink: ),
and you with 3 equalized ("Perfectly" (tm)) placements have 400# per, and the
4-point anchors 300# per. If each loses one anchor, the score becomes, resp.,
600-600 vs. 300-300-600. (4pt can yield one more, THEN they're even!)
Which would you prefer, and why not?
:roll:
|
|
|
|
|
rgold
Mar 17, 2006, 5:07 AM
Post #147 of 164
(31354 views)
Shortcut
Registered: Dec 3, 2002
Posts: 1804
|
In reply to: have you put this analysis in terms of 2-D space
Yes.
In reply to: and will looking at it in 3-D space expand the indeterminate solution subspace?
You mean the dimension of the subspace? Possibly, I think, but not necessarily. Three equal arms in space (tetrahedral anchor) is not statically indeterminate.
I should emphasize that I have not done the 3D analysis at all and have only played with a special case or two of the 2D analysis, so my comments might be subject to revision.
Presumably there are some real engineers out there (I only play one on the internet) who can do this in their sleep or have programs that do it while they sleep.
|
|
|
|
|
|
|
|
knudenoggin
Mar 17, 2006, 9:56 PM
Post #149 of 164
(31354 views)
Shortcut
Registered: May 6, 2004
Posts: 596
|
In reply to: healyje asked "knudenoggin, Got a photo or drawing illustrating a completed rig.
Papounet wrote "We have independently come to the same idea. "
Yes, as has Fingertrouble Craig C. in his book, in part--the part about how
to replace the "X" with what I'm calling the "ELET".
We have illustrated single-strand implementations of the general
compound ELET system, to which (as with some other systems, notably
that of mhabicht) one might fault the reliance on single strands. For ours,
unlike mhabicht's (NB!), could be done in heavier (retired 9mm?) cord,
as we lack a sort of shadow cord to limit extension--the ELET does
that.
However, it is arguably simpler to adapt one's existing 7mm/5.xmm cordelette
material to suit a twin cord + tape slings system, using 2 cords and 3 slings.
In my illustration below, such a system is presented. What is not made clear
in the image (sorry) is that the slings at the mid level--i.e., those to which the
twin cord is tied--are used in dogbone orientation: they are thus
doubled, and provide double strength & surface to the 'biner; the twin cord
ties easily with a Becket Hitch (sheet-bend-like) to the folded eye-ends of these
slings. The belayer-end sling however is used single-strand, knotted to 'biners
(with either Overhand loops or Clove Hitches); it thus might be prudent to back
this up with a 2nd sling, knotted or loose (pure back-up, then), or use here
simply a stronger sling (12mm HPME vs. 6-8mm?).
http://tinypic.com/rldjb7.jpg
Again, mhabicht's system is a single-strand one with a 2nd strand lying dormant
until anchor failure, when the load-bearing shifts from one strand onto another
--with unexplored consequences at the knot(s). Clipping the butt-end of a Fig.8
doesn't look optimal, IMHO.
Other systems entail much rope-over-'biner movement, and as JL has confirmed
for some, at least, the friction of all this will reduce equalization; maybe it's
adequately distributed, but that's something I'd like to see tested. And it can
make a need for having just the right sort of 'biner to reduce frictional and binding
effects (a 'biner w/much angle at the end will jam cords together).
*kN*
|
|
|
|
|
healyje
Mar 17, 2006, 10:13 PM
Post #150 of 164
(31354 views)
Shortcut
Registered: Aug 22, 2004
Posts: 4204
|
Knud,
Thanks for the image. I could be just a bit easily confused but I don't really see why you wouldn't just X slings for all 3 or 4 components? Not sure what the advantages here are and it all feels a bit awkward and complex at first blush. I also don't understand your mhabicht single strand comment or how those cloved single strands are any less desirable than your [single] loops? Could you elaborate? Also, is the smaller, second device illustration on the bottom right a close up of the lower component of your rig or an additional redundant component the also clips in to it?
In general I share your concern about the efficacy and wisdom of clipping one side of an eight and feel an inline-8 is probably more appropriate even if bulkier - but maybe it isn't a problem beyond just feeling wrong, who knows. I decidedly don't like simply clipping around overhand knots either.
|
|
|
|
|
|
|
|
|
