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antigrav
Jun 29, 2004, 5:30 AM
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In reply to: Well, the problem here appears to be that a few RC.com posters who apparently do not have enough climbing experience to actually determine what is safe vs. what is not safe are pretending that they do--and becoming holier-than-thou in their approach to climbing safety.
Mm. But are those the ones with little or a lot of experience? Sometimes not all the experience in the world is enough.
In reply to: Let's be absolutely clear about one thing and not confuse the cause with the result. Redundancy is not the goal in setting up a safe climbing anchor. Do not take your eye off the ball-- safety itself is the ultimate goal and redundancy is only one tool that may be used to effect that end result. Redundancy can indeed sometimes cause an anchor to be safe enough to climb on--but equally so can other things. And, redundancy by itself does not make an anchor safe. Curt
I like the picture of redundancy as insurance. In this particular case, a TR setup, there is probably more material avaliable, at least another 15 seconds to build the anchor, and finally the possibility to retreat from the climb. So, the insurance seems to be totally free. Why would anyone throw away free insurance against one's own misjudgements about safety?
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alpnclmbr1
Jun 29, 2004, 5:55 AM
Post #202 of 219
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If you are referring to me.
I do feel that sticking to a strict policy of redundancy is safer than considering it optional or as you seeming feel, useless. (I consider this a fact despite the fact that I cannot really quantify it other then claiming a significantly lower failure rate.)
As far as the original anchor. It is redundant everywhere except for where it needs to be the most. If you do not need redundancy at that point in that anchor, then I have a hard time imagining that you would ever need it. By the rules you have stated in this thread a single stopper top rope would be perfectly fine.
Did you read largo's post? Are you still having trouble with his position on the matter?
You have yet to offer a reason of why you would forgo redundancy beyond feeling that you can. As far as I am concerned that isn't much of a reason.
=-=-=-=-
You brought this up in this thread as a justification for accepting the non-redundancy in the original post anchor. (it is how i found out it was non-redundant)
I remembered why I didn't notice that you set up a non-redundant top rope anchor the one time we roped up together. I didn't top out the 5.5 part at the top, to save time. The only reason I didn't top out and check the anchor was because you set it up. Normally, I would always check the anchor before I actually weight the rope.
Now this was an 11c with a line of 6 people, only two of which had much of a chance of sending it. You extended the anchor (from a cordelette)
over an edge with a single sling despite having three racks sitting at the base. Joshua tree rock to boot.
In this situation, I would be pissed at a beginner climber for doing this to me. I don’t like being a hypocrite, and to not judge you in this matter would be hypocrisy.
How do you think the other four people feel about redundancy?
=-=-=-=-=-=-
Redundancy is the primary tool in my toolbox for staying alive. You don't always have good gear. You cannot always build what is commonly considered an equalized anchor. You can always build a redundant anchor.
With no gear left whatsoever, and no slack in the rope to sling something. I can still build a redundant anchor. All I need is my right and left foot.
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guitar256
Jun 29, 2004, 6:07 AM
Post #203 of 219
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In reply to: Or perhaps if I told everyone I knew that Curt Shannon tied quadruple fisherman's knots.
Is there something wrong with a quad fisherman's knot??
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curt
Jun 29, 2004, 6:38 AM
Post #204 of 219
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In reply to: If you are referring to me. I do feel that sticking to a strict policy of redundancy is safer than considering it optional or as you seeming feel, useless. (I consider this a fact despite the fact that I cannot really quantify it other then claiming a significantly lower failure rate.) As far as the original anchor. It is redundant everywhere except for where it needs to be the most. If you do not need redundancy at that point in that anchor, then I have a hard time imagining that you would ever need it. By the rules you have stated in this thread a single stopper top rope would be perfectly fine. Did you read largo's post? Are you still having trouble with his position on the matter? You have yet to offer a reason of why you would forgo redundancy beyond feeling that you can. As far as I am concerned that isn't much of a reason. =-=-=-=- You brought this up in this thread as a justification for accepting the non-redundancy in the original post anchor. (it is how i found out it was non-redundant) I remembered why I didn't notice that you set up a non-redundant top rope anchor the one time we roped up together. I didn't top out the 5.5 part at the top, to save time. The only reason I didn't top out and check the anchor was because you set it up. Normally, I would always check the anchor before I actually weight the rope. Now this was an 11c with a line of 6 people, only two of which had much of a chance of sending it. You extended the anchor (from a cordelette) over an edge with a single sling despite having three racks sitting at the base. Joshua tree rock to boot. In this situation, I would be pissed at a beginner climber for doing this to me. I don’t like being a hypocrite, and to not judge you in this matter would be hypocrisy. How do you think the other four people feel about redundancy?
I guess you would have to ask them. One of them, over 200lbs, took many, many falls on this TR that I set up with no bad result. And, by no bad result, I do not only mean that he didn't die--I mean that there was not even undue wear to any of the carabiners or slings used in the set-up.
=-=-=-=-=-=-
In reply to: Redundancy is the primary tool in my toolbox for staying alive. You don't always have good gear. You cannot always build what is commonly considered an equalized anchor. You can always build a redundant anchor. With no gear left whatsoever, and no slack in the rope to sling something. I can still build a redundant anchor. All I need is my right and left foot.
You simply don't understand what constitutes a safe climbing anchor. Perhaps eventually you will, and perhaps not. Until then, I encourage you to continue to back up everything. Since you admittedly can't tell when it is necessary from when it is not, guessing wrong could lead to a very bad outcome for you.
I will leave you with another non-climbing engineering analogy. In 1979, American Airlines flight 191 (a DC-10) crashed on takeoff from O'Hare airport in Chicago because the engine fell off the left wing, killing all 270 people on board. Initially, DC-10 critics noted that a single pin held the engine to the wing on the DC-10 aircraft. However, further investigation found that improper maintenence procedures were used on this particular airplane that stressed the pylon holding the engine to the wing.
The lack of redundancy (as first thought) had nothing to do with this crash. No modifications (i.e. additional redundancy) was built into this aircraft regarding engine mounting. Rather, the maintenence procedures were changed. Result--no other engines have fallen off DC-10 aircraft in the last 25 years. A single pin still holds each DC-10 engine to each wing.
Flash forward 10 years to 1989. United flight 232 (also a DC-10) experiences an explosive failure of engine #2 (the one in the tail) and the pilots notice soon afterwards that they no longer have the ability to move any of the control surfaces of the aircraft. All three of the fully independant and redundant hydraulic systems of the aircraft had been severed by the exploding engine. The pilots were able to crash land the plane in Sioux City and nearly 70% of the people on board miracuously lived.
The relevant point being that a fully independent and triple redundant system can (and does) fail just as easily as a non-redundant system. Redundancy does not equal safety no matter how many times you claim that it does. There is much more to safety than redundancy alone.
Curt
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nonick
Jun 29, 2004, 7:11 AM
Post #205 of 219
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1) Not redundant
2) The biner are not opposed and opposite. Better to use locking ones.
3) Nylon on Nylon - never a good idea....
4) Abrasion on the edge..a good chance of that happening?
5) There appear to be some good chockstones (cant be sure) which would definitely make better anchor points than a crack!
I would NEVER climb on an anchor like this one..
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whitefingers
Jun 29, 2004, 7:16 AM
Post #206 of 219
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My take? I would climb with Curt. As for some of the rest of ya, well thats another story :roll:
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tradklime
Jun 29, 2004, 3:30 PM
Post #207 of 219
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In reply to: The relevant point being that a fully independent and triple redundant system can (and does) fail just as easily as a non-redundant system. Redundancy does not equal safety no matter how many times you claim that it does. There is much more to safety than redundancy alone. Curt
Well, in this case your analogy may very well be correct. Redundancy is not effective if it is subject to the same mode of failure.
With this anchor, doubling up the sling at the edge is likely not as effective as padding the edge, although it would still be better than what was done (i.e. a single sling). Padding the edge was your original suggestion and it was a good one.
I think where things went awry in this thread was your failure to stress that point and your contention that the anchor was fine as is. Perhaps it was for that particular day, but when analyzing anchors as a learning tool, in my opinion, it is important to stress things that were potentially overlooked or could be improved. Start conservative, and with experience, people will hopefully have the appropriate skills to judge when reducing conservatism is reasonable and safe.
In this case I would have done something about the edge. I was not everwhelmingly concerned, so I would have doubled the sling at the edge for just a little something extra. I would have done this because it was the quickest and easiest improvement, albeit not the best, but sufficient in my judgement.
I agree with you that the sling is strong enough. I have made such determinations to rely on a single component in real life. Although in this situation, it seems that there is a potential, significant risk to that single component. And therefor comes the question, why not address it? There are many different ways to address it, and all of them are NOT equal, however, as a learning tool, and as a matter of course, why not stress the point that it should be addressed in some fashion and then discuss the merits of each option?
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dirtineye
Jun 29, 2004, 4:03 PM
Post #208 of 219
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If the climb were straight up to the anchors, then padding would work. If the climb wandered left and/or right a fair amount, then padding alone would not be sufficient, since the webbing could slide off the padding.
I've seen this very thing happen.
Again, one reason for a two (DISTINCT and SEPERATE) point top rope anchor is to prevent this sliding along an edge problem.
There's no point in getting personal about this. It's an anchor discussion, not a chest beating seminar. Who cares about who anyone posting in this thread would climb with or not?
Almost every post has had merit. How about just taking in the discussion and trying to learn something, and leaveing the feelings out of it?
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tedc
Jun 29, 2004, 4:45 PM
Post #209 of 219
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In reply to: In reply to: Soles was seeing what he wanted to see. There is no way a girth hitch would hold even body weight if the sling was cut. It is not redundant. Have you actually tried this? I'm not saying that it would hold 1000lbs, and I certainly don't set things up like this, but it will certainly hold body weight. Perhaps not in a tape-cord connection, but in tape-tape, definitely. Cheers, Karl P
Absolute BS dude. :evil: A single wrap prussik with nylon sling CANNOT be expected to hold body weight.
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brutusofwyde
Jun 30, 2004, 5:35 PM
Post #210 of 219
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In reply to: Well, the problem here appears to be that a few RC.com posters who apparently do not have enough climbing experience to actually determine what is safe vs. what is not safe are pretending that they do--and becoming holier-than-thou in their approach to climbing safety.
Curt, I thought you were out of this thread?
Although I see no need to get in a p!ssing match regarding who is experienced and who is not, let me just say that I believe that I have sufficient experience to construct and/or recognize a safe anchor.
Where everyone is disagreeing is the question "is this anchor safe enough." and I have seen enough of the "holier-than-thou" and from both sides of the discussion.
Since each of us has a different threshold of acceptable level of risk, agreeing or disagreeing on this issue is like debating how many angles can dance on the head of a piton. This is evidenced by the length of this thread. And I believe that issue is "the problem here".
Many of alpnclimbr's points are spot-on, and I happen to agree with him regarding the adequacy of the anchor. Not due to experience or lack thereof, but due to my threshold for acceptable level of risk.
In reply to: Let's be absolutely clear about one thing and not confuse the cause with the result. Redundancy is not the goal in setting up a safe climbing anchor. Do not take your eye off the ball-- safety itself is the ultimate goal and redundancy is only one tool that may be used to effect that end result. Redundancy can indeed sometimes cause an anchor to be safe enough to climb on--but equally so can other things. And, redundancy by itself does not make an anchor safe. Curt
All valid points, and a succinct summary.
To that I will add: even the safest, most perfect textbook anchor does not a safe climb make. Safety starts with focus, knowledge, experience, and attitude. The party on the 4th day of their climb of the NW Face of Half Dome belaying off of a SRENE anchor and the HDIAD party party passing them, via an alternate pitch, belaying off a single untested fixed pin and a yellow alien, can each be either extremely safe or climbing wildly out of control.
That said, it seems we all seem to agree that, given the information we have, the webbing running over the edge is less than perfect. "Good enough?" We're back into the "I'm-right"-"No-I'm-right" merry-go-round.
I don't subscribe to dogma. My favorite answer to questions regarding climbing ("what's the best way to...") is It Depends [TM].
Perfect? No. Good enough???
It Depends. [TM]
I wouldn't set it up that way.
:)
Brutus of Wyde
Old Climbers' Home
Oakland, California
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nlmorton
Jun 30, 2004, 6:39 PM
Post #211 of 219
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In reply to: By the way, for those of you who disbelieve my statement that a dynamic rope breaks at ~10kN, check any rope manufacturer website.
NE Ropes website:
In reply to: What is the Tensile Strength or Breaking Strength of a Maxim Rope? A dynamic rope is strong for its size. However, the rope is primarily designed to absorb the shock of a fall. A strong rope may or may not absorb fall better than one that is less strong. For this reason, UIAA does not require a tensile test for rope certification. To appease your curiosity, a dynamic rope will break at approximately 7,000lbs to 9,000lbs [30kN-40kN] depending on size and construction. Tensile strength should not be considered when choosing a dynamic climbing rope. It is not relevant to how a rope performs for rock climbing and mountaineering.
http://www.neropes.com/climbing/contact_us.htm
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sync
Jun 30, 2004, 6:44 PM
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But that's the "tensile" strength, and from the exact part you quoted:
In reply to: Tensile strength should not be considered when choosing a dynamic climbing rope. It is not relevant to how a rope performs for rock climbing and mountaineering.
What you really need to look at is this: (from the exact same web page that nlmorton provided)
http://www.neropes.com/...namic_spec_table.gif
In reply to: 3 sigma MBS (Minimum Breaking Strength) is the method of calculating minimum breaking strength by taking the mean result of five test samples less three standard deviations. This provides a 99.87% certainty that any given rope will meet or exceed the reported MBS
If I'm understanding this table correctly, then I would agree with DM that the ropes break at about 10kN.
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alpnclmbr1
Jun 30, 2004, 6:55 PM
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Ropes are designed to limit the forces imparted to the falling climber to around 10kn.
In the same way that a sling is rated to 22kn, a rope would be rated to 30+kn. ie a rope is much stronger then webbing.
The reason it is set up this way is because people break around 12kn.
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nlmorton
Jun 30, 2004, 7:04 PM
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In reply to: If I'm understanding this table correctly, then I would agree with DM that the ropes break at about 10kN.
You're not. Maximum Impact Force is not the same as the force that breaks the rope.
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sync
Jun 30, 2004, 7:10 PM
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In reply to: In reply to: If I'm understanding this table correctly, then I would agree with DM that the ropes break at about 10kN. You're not. Maximum Impact Force is not the same as the force that breaks the rope.
So what do they mean by "Impact force" in the table? They don't list the "Minimum breaking strength" in their table then. How does that differ from "tensile strength"?
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nlmorton
Jun 30, 2004, 7:36 PM
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In reply to: So what do they mean by "Impact force" in the table?
They mean the upper limit for the force on the anchor in the first UIAA drop test.
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alpnclmbr1
Jun 30, 2004, 8:10 PM
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In reply to: In reply to: So what do they mean by "Impact force" in the table? They mean the upper limit for the force on the anchor in the first UIAA drop test.
That is two idiotic trolls created for this thread.
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lex04
Jul 3, 2004, 2:49 AM
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The impact force listed under the UIAA guidelines concerns the maximum force transmitted to the falling climber. It is around 10kN because as someone already pointed out that is around where the threshold is force force that the human body can take without snapping.
As for the original thread, IMO the anchor would suffice but why not take all of one minute to make it more redundant? Suppose you arrived at a two 1/2 inch bolt anchor, you knew the person that put it there was competent, and the rock quality was bomber, and suppose you decided to sling the two bolts. You would still put a sliding knot in the runner for fear of one of the bolts blowing even though the tolerance of the bolts are around 5000lbs, and you would probably use a second runner even though those top out around 4500lbs.
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papounet
Jul 6, 2004, 8:27 PM
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I can't help chiming in ;-)
by my leaflet (not yet a book)
Problems
1. the 3 nuts are together => impossible to inspect and subject to fail alltogether if rock fails
2. sling over edge => any lateral movement (pendulum) will see-saw through it very rapidly)
Not a problem:
3. normal biner, (instead of locker) as the setup will always be in tension, they are not crossloaded and the gates are facing away from the rock => OK
4. the orange cordelette is quite redundant as the combination of knot and girthitch means that if one strand is cut, the setup won't slip (see analysis of acident where someone used tape which had been spliced and covered with adhesive tape)
4. if indeed there is a knot above the bottom biner, the lower sling would survive the cut of one leg => quite redundant
Question if an incident would cut one leg of the sling, would it also sever the second leg ?
How to improve:
1. multiple crack system
2. pad the sling
3. add another sling not under tension (ideally below the edge), if first one fails
4. inspect set up
Beware when comparing a TR setup, a belay setup, and a rappel setup
A TR setup has to withstand lower ff, nonetheless even with a tight rope (zero slack), the elasticity of the rope will let the climber "fall" a few meter, thus it is not trivial, it is much more than the weight of the climber and the belayer weigth). The energy of the fall is measured at the lowest point. If the elasticity of the rope lets the climber go down by 5 meters over a total length of rope of 30m the fall factor is 5/30. The experience of a slow motion fall should not let you underestimate the force on the TR anchor, especially if there is no intermediate QD to ad friction.
Regarding the argument "one rope, one harness, one stout tree but 2 bolts, 2 slings, 2 pieces..." redundancy argument, Redundancy is a "cost-cutting" method to avoid having to build the strength needed in one piece. To go back to the airplane analogy, it is possible to armor one set of control wire but it is much heavier than setting up independant multiples sets. If you have a strong enough something, you may not need redundancy. If building it strong enough is too much of a bother, or if you do not have information on the strength of that something, you should look into backing it up. If using double of everything is clumsy, then you build it big, thus single rope are larger/heavier/stouter than double ropes and belay loop can hold over 2 tons.
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