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charlesjmm
Mar 21, 2006, 5:21 PM
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In reply to: In reply to: Healyje, a close inspection of the b---- will reveal it is in fact a 2 separate structures design joined by 2 biners to the lower powerpoint mechanism. Charles, I object to it being made out of two separate cords vs. a single cord in the equalette/mhabicht. In reply to: Maybe I don’t understand what you mean by “….multiple strands are created but only one is clipped…..”, but in the b---- multiple strands have been created but only one is hitched. Is there any difference? Why not simply use two plain sliding-X slings instead of all the hoopla with a cordalette? In reply to: If you call for better equalization, you need the complexity of the mhabicht. In such a case, the difference in complexity lies in how the slack cord (controlling extension) is being used. In mhabicht’s, the slack cord is used vertically while in TIA it’s used horizontally. I much prefer the slack be vertical and made from the same piece of cord.
Healyje,
“…….I object to it being made out of two separate cords vs. a single cord in the equalette/mhabicht……”
TIA is made out of one cord; in my post I made the observation that my original cordelette was not long enough so I lengthened it with the orange cord; I will post a picture of TIA built with a single cord. I also mentioned that TIA needed an extra long cordelette.
“…..Why not simply use two plain sliding-X slings instead of all the hoopla with a cordalette…..”
I agree and this thread would have been much shorter. But I think a number of great ideas have come to surface during this intense search for the better.
“….I much prefer the slack be vertical and made from the same piece of cord….”
I think the system will not really notice where the extension limiting is coming from.
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healyje
Mar 21, 2006, 5:22 PM
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In reply to: You raised the point about our showing a single 'biner (to which I argue there's no problem w/twins), but I must stress the mhabicht problem of running SINGLE CORD--with single-cord extension back-up! Why are you not concerned about dropping 50% of some fall force on a single cord? (Note that in my first sketch of a compound ELET system, I also used single cord; but there one could see to using thicker rope (e.g., 8-9mm), as it essentially was replacing twin cord throughout, as opposed to mhabicht's structure which has these shadow strands standing guard against extension.) So, either you're going, ah, 'i]Lite in protection, or you're going heavier in cordage for same protection.
No, I'm not concerned as that is the point of redundancy relative to the number of active strands in play.
In reply to: I should note that you're also willingly taking the effectiveness / strength of those mid-level Fig.8 knots loaded in the butt w/o any data! |
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healyje
Mar 21, 2006, 5:27 PM
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In reply to: Healyj I am not missing the point. The point is to come up with a new system that works? I appreciate all the work you guys are putting into it. Most of this stuff is over my head. Come up with something simple enough for me to grasp and I will be verey gratefull 8^) Your picture looks pretty simple but also looks like it is not redundant? Also has a weird knott in it that i don't know how to tie? The system should be simple enough that even AMGA certified TOP ROPE Guides can build it :D
Again, all those question's such as how to tie the knot are back in the thread. The point is a thorough exploration not only of completed rigs but of the fundamentals, concepts, compromises, and components that go into developing them. If you take this thread to simply be about coming up with the best xxxxxx rig you're really short-changing yourself.
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healyje
Mar 21, 2006, 5:31 PM
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In reply to: In reply to: healyje-The beauty of mhabicht's design is that you have complete control to fine tune extension. Exactly, and with the AstroGlide as well.
In the end I prefer the cloves on the top biners as the mechanism of that control.
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glowering
Mar 21, 2006, 6:16 PM
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In reply to: I have similar concerns about glowering's approach to accomodating a single biner by lengthening one of the "boxed" strands which essentially loads only one side of the 8 - I'd rather endure the friction of putting them in a sliding-X to keep the knot loading uniform.
I take it you are discussing the limiter knot? It is an overhand not an 8. In a complete anchor (or side piece failure) it is the same as any other loop at the end of a rope. (e.g. tie an 8 at the end of the rope and clip to the anchor for a fixed line, or the tie in at your waist harness). If the middle piece fails it will load like an EDK (why it should be an overhand not an 8), which testing has shown is fine.
In reply to: In the end I prefer the cloves on the top biners as the mechanism of that control.
Why? In a 4 piece mhabitch anchor the clove hitches gives 25/25/25/25% loading and work great, but in a 3 piece the Astroglide gives 33/33/33 and ties with only 2 overhand knots, much faster than 4 cloves and better load distribution.
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tradklime
Mar 21, 2006, 7:28 PM
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In reply to: Jake - I like that system too. As you probably know, you can get around the possible drawbacks of the setup as pictured (which include 1) large amount of extension if 1 piece blows, and 2) total anchor failure if the single strand is cut or the double-fisherman's knot unties) by adding a limiter knot to the center strands, as shown on Trango's website
I know I'm a day late in this one, but if you knot the middle leg of a AE rig it kills the equalization. You basically have cordelette anchor, with the differential leg stretch and cascade failure issues.
I think the safest approaches to an AE rig are to: 1) Build it with the climbing rope, thus mitigating extension issues with the dynamic material, or 2) build one similar to the one I presented a couple pages ago with doubled up cord; keeping the size limited to prevent extensive extension and use other slings, rope, etc. to extend the rig to pieces that are spread out ("firewall").
Personally, I currently own the 3 foot Trango version and have used it for ice screw anchors this past season. I've liked it just fine for this application and haven't been that concerned with the lack of redundancy with the sling.
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healyje
Mar 21, 2006, 7:43 PM
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In reply to: In reply to: In the end I prefer the cloves on the top biners as the mechanism of that control. Why? In a 4 piece b---- anchor the clove hitches gives 25/25/25/25% loading and work great, but in a 3 piece the Astroglide gives 33/33/33 and ties with only 2 overhand knots, much faster than 4 cloves and better load distribution.
From the third picture in your series showing the Astroglide I don't see how you can make that assertion - the center point is supporting both sides for 25/50/25 from what I can see. I can't tell what knot your using from the pictures - maybe a closeup? I explicitly prefer the strands secured at the top biner and the total control of extension that provides. I also prefer that method of redundancy.
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tradklime
Mar 21, 2006, 7:46 PM
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In reply to: the big thing that has allways turned me off with slidingx is the fact that if one strand cuts you go splat.
A couple of limiting knots basically addresses both the redundancy and extension issues of the sliding-x. With limiting knots, total failure would require a simultaneous placement failure and a strand of the sling being cut between the knots.
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charlesjmm
Mar 21, 2006, 8:05 PM
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.
Remember the Mhabitch variant I proposed on page 45 which used the Double Figure 8? This design was only applicable to scenarios that allowed compact anchor arrangements and so it was dismissed for that matter.
http://i49.photobucket.com/...losjmm/MHExplExt.jpg
But, what if you apply this idea to the master point instead and apply limiter knots if necessary (so simple yet did not realize it until now)? A very clean design that would substantially amplify the range of applicability and make it useful for any scenario.
This time I used a Bowline on a bight to create the master point :
http://i49.photobucket.com/...sjmm/MHVarRedExt.jpg.
My joy came to a hault when I realized that it still is a 25% - 50% - 25% design. :cry: ...... the search continues......
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healyje
Mar 21, 2006, 8:15 PM
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In reply to: But, what if you apply this idea to the master point instead and apply limiter knots if necessary (so simple yet did not realize it until now)? A very clean design that would substantially amplify the range of applicability and make it useful for any scenario. This time I used a Bowline on a bight to create the master point.
Charles, I immediately gave both a double 8 and bowline a whirl for the masterpoint when I first tried mhabicht's rig. Unfortunately the functional essence that makes these knots a reality - the sliding loop around the standing part - makes them unsuitable in this application as a failure anywhere in the cord beyond the limiting knot blows the entire side unless you tie yet another knot as you have to prevent it. An inline-8, however bulky is probably the best choice...
P.S. To be honest, the 25/50/25 thing doesn't really bother me that much though I like looking at the set of possible 33/33/33 solutions...
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glowering
Mar 21, 2006, 8:18 PM
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In reply to: From the third picture in your series showing the Astroglide I don't see how you can make that assertion - the center point is supporting both sides for 25/50/25 from what I can see. I can't tell what knot your using from the pictures - maybe a closeup? I explicitly prefer the strands secured at the top biner and the total control of extension that provides. I also prefer that method of redundancy.
The outer arms have a loop going over the caribiner, a theoretical 2:1 pulley, while the middle arms are tied loops (so on each side the outer loops have twice the load of the inner loops) so you put the two inner loops on the center piece each with 1/6 of the load and it adds to 33% of the load. Let me know if a diagram would help, it's pretty confusing.
The knot is just a simple overhand.
You get total control of extension in the AstroGlide by the amount of slack in the loose strand (VERY little extension, try it) and the distance of the limiter knot from the biner. I'll have to play with the mhabitch some more, but all the pictures show it with much more potential extension that the AstroGlide. I also like the redudancy of the mhabitch, but I think the AstroGlide has enough redundancy and the better load handling and speed of setup outweighs that for a 3 piece anchor IMO.
If you haven't tried the AstroGlide, I encourage you to. Try it in a variety of 3 placement situations. Very versatile, and fast.
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healyje
Mar 21, 2006, 8:24 PM
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In reply to: You get total control of extension in the AstroGlide by the amount of slack in the loose strand (VERY little extension, try it) and the distance of the limiter knot from the biner. I'll have to play with the b---- some more, but all the pictures show it with much more potential extension that the AstroGlide. I also like the redudancy of the b----, but I think the AstroGlide has enough redundancy and the better load handling and speed of setup outweighs that for a 3 piece anchor IMO. If you haven't tried the AstroGlide, I encourage you to. Try it in a variety of 3 placement situations. Very versatile, and fast.
I will give it a try, but I would dispute it or any of the top-equalizing rigs provide the same level of control of extension on each and every individual placement. You can control it for the pair - but not for each point individually.
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hemp22
Mar 21, 2006, 8:39 PM
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In reply to: I know I'm a day late in this one, but if you knot the middle leg of a AE rig it kills the equalization. You basically have cordelette anchor, with the differential leg stretch and cascade failure issues.
with the knot in place, it will still equalize (distribute the load between all 3 pieces) in the single direction of pull that it is built for (straight away from the middle piece) - the differential leg stretch is still taken care of by being able to slide over the biners. But the limiter knot kills any "Range" of equalization. so you can't move the direction of pull and have it still equalize.
But, that's just a matter of terminology. I actually agree with you that the limiter knot isn't ideal because of that loss of range, which is why I also included that 2nd option in the previous post.
in the end, I do really like the aesthetics of the double-fig-8 knot AE, but I think I'm still finding more versatility in carrying a cord pre-tied for the mhabrict/equalette setup instead.
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jakedatc
Mar 21, 2006, 8:48 PM
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Hemp.. Papounet's idea with using the alpine butterly powerpoint instead of the double 8 saves a ton of cordage. and can be left tied (and still easy to untie after loading if need be)
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roy_hinkley_jr
Mar 21, 2006, 9:14 PM
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One more time. Charlesjmm, please edit your images so they are 800 pixels wide! 600 pixels would be better. You're posts really screw up readability of everyone's text.
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glowering
Mar 21, 2006, 10:23 PM
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In reply to: healyje - I will give it a try, but I would dispute it or any of the top-equalizing rigs provide the same level of control of extension on each and every individual placement. You can control it for the pair - but not for each point individually.
Actually the length of the loose strand controls the extension for the middle arms, the distance of the overhand limiter knot above the biner controls extension for the outside arms. The mhabicht is nice cause it's doubly redundant, two independent cords going to each placement, but is that necessary?
In reply to: charlesjmm- My joy came to a hault when I realized that it still is a 25% - 50% - 25% design. ...... the search continues......
Take the limiter knots out of the outside arms and you have an AstroGlide with a 33/33/33% design. :D
It's funny, I forgot about this design I posted back on Feb. 24, as an idea to get us thinking (too time consuming and complicated for actual use), then the mhabicht got me thinking about the benefits of biners on the lower knots again, and this design probably influenced the AstroGlide even though I hadn't thought about it since I had posted it.
http://img159.imageshack.us/...9/6107/cord3x2yu.jpg
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tradklime
Mar 21, 2006, 11:08 PM
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In reply to: with the knot in place, it will still equalize (distribute the load between all 3 pieces) in the single direction of pull that it is built for (straight away from the middle piece) - the differential leg stretch is still taken care of by being able to slide over the biners.
At risk of being pedantic, or an ass if I'm wrong, I'm fairly certain that this is not correct. I think it appears to be equalized, much like a perfectly tied cordelette anchor would, but in fact is not. This is because for these "pulley" type systems to equalize (with unequal leg lengths), the sling needs to be free running between all three biners. The knot on the middle leg effectively prevents this. The same mechanism that prevents "range" of equalization, prevents true equalization to begin with, just very subtly.
I only bring it up because I think it illustrates an important point of the equalization discussion.
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charlesjmm
Mar 21, 2006, 11:24 PM
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In reply to: One more time. Charlesjmm, please edit your images so they are 800 pixels wide! 600 pixels would be better. You're posts really screw up readability of everyone's text.
Thank you for the observation. I have changed all my jpg images to 720 x 540 - 44k.
Hope that helps.
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charlesjmm
Mar 22, 2006, 12:53 AM
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In reply to: Charles, I immediately gave both a double 8 and bowline a whirl for the masterpoint when I first tried mhabicht's rig. Unfortunately the functional essence that makes these knots a reality - the sliding loop around the standing part - makes them unsuitable in this application as a failure anywhere in the cord beyond the limiting knot blows the entire side unless you tie yet another knot as you have to prevent it. An inline-8, however bulky is probably the best choice... ...
Looking at all the possibilities of cord failure while using the Double Figure 8 or the Bowline on a bight, I observe the following :
1) Rupture : Between anchor and limiter knot. Safety : Pair anchor + slack cord
2) Rupture : Where biner clips. Safety : 2 anchors + slack cord
3) Rupture : Slack cord. Safety : no consequence
4) Rupture : Between the knot and the HMS biner. Safety : Fatal if the 2 strands are cut
To blow an entire side, both placements must collapse in which case the other side of the anchor would take over.
This means that our worst case would be scenario 4. Nevertheless, all designs incorporating an Equalette type master point would have the same Achilles heel regardless of the knot used to create the master point.. This would be equivalent to having the rope cut between your harness and the master point biner.
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healyje
Mar 22, 2006, 1:29 AM
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Charles,
Again, just by the way doubled knots on a bight are formed a cut in any part of either loop in a rig that is a straight equalizer and not top-cloved can result in a loss of both loops entirely unless the knot is really well dressed an maybe even in that case with enough force. I wouldn't use either in this type of application where you want absolute integrity in each individual loop.
EDIT: Charles, that post above was wrong in the case of mhabcht's rig and I shouldn't have said it and certainly not that way. I was mixing two thoughts of its suitability in bottom-equalizing rigs in general and in mhabicht's in particular. It results in the loss of a side's equalization in the case of mhabicht's rig and only results in the loss of the total side in the case of non-cloved, non-limited bottom-equalizing rigs. My general take is I do want two loops that are not interdependent in the way they are in doubled knots on a bight.
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fingertrouble
Mar 22, 2006, 1:43 AM
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glowering, I don't know if you realize it, but your 3-placement designs don't equalize, they're 25%-50%-25%--and that's on a good day. rgold ran it down way back in this thread, but here's a brief explanation for those who might have tuned in late.
Consider the master point carabiner of your latest design. First point: that's a sliding-X, which we'd like to eliminate as it apparently has significant sliding friction that will reduce its ability to equalize in the instant of peak applied force. You can reduce the sliding friction to half that of the equalette (probably 1/4 that of the sliding-X) by simply clipping only one of the strands (John Long has written here that anchor strands simply do not break, so clipping both is like scratching a place that doesn't itch). While you're at it, flip the locker upside down from what you've shown for the absolute lowest sliding friction.
But suppose it does equalize; that means that your two middle carabiners would each see half the load. Next consider each of them. Same problem with sliding-Xs but in less critical spots; just convert to a lower friction "troublette"-type configuration by clipping only one strand. Assuming they actually equalize, however, that would mean that the tension on each of the four upper (double) strands would be equal: 1/4 of the total load on each double strand.
Now consider the top (placement) carabiners. The outer placements each see 1/4 of the load but the middle placement, receiving two double strands (invert your wire gates), sees 2/4 of the load. There's your 25%-50%-25% non-equalization.
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hemp22
Mar 22, 2006, 1:57 AM
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In reply to: In reply to: with the knot in place, it will still equalize (distribute the load between all 3 pieces) in the single direction of pull that it is built for (straight away from the middle piece) - the differential leg stretch is still taken care of by being able to slide over the biners. At risk of being pedantic, or an ass if I'm wrong, I'm fairly certain that this is not correct. I think it appears to be equalized, much like a perfectly tied cordelette anchor would, but in fact is not. This is because for these "pulley" type systems to equalize (with unequal leg lengths), the sling needs to be free running between all three biners. The knot on the middle leg effectively prevents this. The same mechanism that prevents "range" of equalization, prevents true equalization to begin with, just very subtly. I only bring it up because I think it illustrates an important point of the equalization discussion.
My reasoning is something like this:
In the traditional 3-piece cordalette anchor, there are 3 fixed lengths of cord - 1 going from the powerpoint knot to each placement - and because they're all the same material, the shortest leg reaches higher tension first and takes all the load.
For the AE with a limiter knot, there are 2 fixed lengths of cord - 1 from the powerpoint, through left placement, and back down through the ring to the limiter knot, and then 1 on the other side. so, whichever of those 2 lengths is shorter will reach tension first and take the bulk of the load. But either one of those sides is going to load both its outside placement and the center placement, because the cord runs freely between them (neglecting the friction in this case).
But I'm not going to try to hazard a guess as to what ratio it will load them in (50/50, 67/33, or worse?). Given the friction interaction, as well as any dynamic elongation between the limiter knot and the center piece, that would be better left to drop tests than theorizing.
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glowering
Mar 22, 2006, 2:17 AM
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Hey Craig,
Please read the preceding posts before you post.
Are you talking about the AstroGlide (pg.50) or the picture on the top of this page which is from Feb. 24. (pg. 20) and was identified as a dead end design to throw out new ideas?
Your concerns have been covered:
*Check out the improved slidingX I posted on pg. 50
*The locker is "upside down" because that's my powerpoint- I clip at least 3 biners in there, I'm not concerned about the negligible amount of friction and wouldn't happen with an improved slidingX in cord.
*The "troublette" (which I first introduced to this thread) has no redundancy, I would use it in the upper part of an anchor but not for the powerpoint, however it will have more extension than the AstroGlide and take longer to adjust for varying placements
*Outer placements receive 33%33%33% in the AstroGlide I can create a diagram to demonstrate this if it helps.
Craig, try building an AstroGlide, (use other knots if you don't like the figure 8 in the butt, but it's a shame to have an anchor called the AstroGlide and stop doing it in the butt. 8^) ) I appreciate the comments on it, because unless something better comes along or a significant drawback is identified it will probably become my primary 3 placement anchor rig.
Edited for clarity and to remove harshness :)
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healyje
Mar 22, 2006, 6:12 AM
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Charles, Thanks, I'll give that a whirl when I get a break to play again...
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