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ptlong
Mar 31, 2010, 9:46 PM
Post #26 of 45
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cracklover wrote: I'm open to other interpretations of the pic...
...except for the only other interpretation so far offered (which you unequivocally rejected).
In reply to: If you want to make an argument about...
I'm just saying that the photo is ambiguous. You're sure you can see all of the strands, but what if two of them are hidden as in the photo I posted? Then it comes down to interpreting small groups of noisy pixels down near the bottom carabiners. The written description doesn't help. The data, while interesting, do not resolve the question. And the fact that they did not correctly calculate the ideal values for all of the other anchors makes it harder to use that for support.
Who knows? And who would really care except that since the point of the paper is at best barely tangent to what recreational climbers are interested in it turns out that it's more fun to argue about a fuzzy photo.
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cracklover
Apr 1, 2010, 2:35 PM
Post #27 of 45
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ptlong wrote: cracklover wrote: I'm open to other interpretations of the pic... ...except for the only other interpretation so far offered (which you unequivocally rejected). In reply to: If you want to make an argument about...
Sorry if it came across that way. But I wouldn't characterize your supposition as an "interpretation of the photo". You pretty much said that the photo is not interpretable. Is that not your position?
If I'm misunderstanding, then please explain where the two hidden strands are going after they come down from the middle anchor. Or are they consistently hidden entirely, throughout every curve and bend? Frankly, I don't even see what the configuration you're suggesting *is* that would allow two more strands to come off the top anchor. Perhaps you could explain that as a start.
GO
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ptlong
Apr 2, 2010, 1:29 AM
Post #28 of 45
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cracklover wrote: But I wouldn't characterize your supposition as an "interpretation of the photo". You pretty much said that the photo is not interpretable. Is that not your position?
I've been referring to two different interpretations so how is it that you would conclude that I believe the photo is uninterpretable? As I've said repeatedly, I think it is ambiguous.
In reply to: Frankly, I don't even see what the configuration you're suggesting *is* that would allow two more strands to come off the top anchor. Perhaps you could explain that as a start.
So after all this you don't even know what the configurations we've been talking about are? That's funny. Okay, let's start with your configuration since you haven't described it in detail. Your diagram doesn't show how the strands travel through the carabiners. And the relative forces you indicated can't be right either, as you must have figured out by now. Let's see a more complete diagram from you.
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cracklover
Apr 2, 2010, 4:15 AM
Post #29 of 45
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ptlong wrote: cracklover wrote: But I wouldn't characterize your supposition as an "interpretation of the photo". You pretty much said that the photo is not interpretable. Is that not your position? I've been referring to two different interpretations so how is it that you would conclude that I believe the photo is uninterpretable? As I've said repeatedly, I think it is ambiguous.
Ambiguous is not an interpretation. Nor is saying there may be four strands to the middle anchor. An interpretation would be saying: "I see the loop of sling traveling through the anchor as such..."
I did not go into detail about how I thought the sling traveled because I thought it was clear from a combination of my diagram and then also my later description of the strand that connects the two sides. But if it's not clear to you, I'd be happy to give you a clearer schematic... tomorrow.
In reply to: So after all this you don't even know what the configurations we've been talking about are? That's funny.
Huh? I have put forward an interpretation of one of their anchors. You have not.
In reply to: Okay, let's start with your configuration since you haven't described it in detail. Your diagram doesn't show how the strands travel through the carabiners.
I thought that would be pretty obvious to anyone who took the time to really look at the photo, and look at my diagram. But as I said, I'd be happy to spell it out more clearly if you like.
In reply to: And the relative forces you indicated can't be right either, as you must have figured out by now. Let's see a more complete diagram from you.
No, I have not figured out that the relative forces cannot be right. If you see a problem with the forces in my diagram, please point them out.
GO
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ptlong
Apr 2, 2010, 6:15 PM
Post #30 of 45
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cracklover wrote: Ambiguous is not an interpretation.
In reply to: I did not go into detail about how I thought the sling traveled because I thought it was clear from a combination of my diagram and then also my later description of the strand that connects the two sides. But if it's not clear to you, I'd be happy to give you a clearer schematic... tomorrow.
Yes, please draw a detailed diagram that shows how the strands travel through the carabiners. Also include the tensions in the strands and how these sum to support the load.
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cracklover
Apr 2, 2010, 6:54 PM
Post #31 of 45
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ptlong wrote: cracklover wrote: Ambiguous is not an interpretation. ambiguous - adj. - 1. Open to more than one interpretation; 2. Doubtful or uncertain.
Okay, so you've clearly got nothing to add to this conversation. You just think that somehow there are two mysterious invisible strands in the photo, and where they go or come from is irrelevant. Thanks, that's *super* helpful.
In reply to: Yes, please draw a detailed diagram that shows how the strands travel through the carabiners. Also include the tensions in the strands and how these sum to support the load.
Here it is again, spelled out:
A -> B -> C -> D -> E -> F -> A
GO
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ptlong
Apr 3, 2010, 12:15 AM
Post #32 of 45
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cracklover wrote: Okay, so you've clearly got nothing to add to this conversation.
Gabe, one thing at a time. You confused ambiguous with uninterpretable so I provided a dictionary definition to hopefully clear that up. Do you now understand the difference?
In reply to: You just think that somehow there are two mysterious invisible strands in the photo, and where they go or come from is irrelevant.
They could be hidden in the photo. Look at the picture I posted for an example of this.
In reply to: Here it is again, spelled out:
That is the same diagram and flawed force analysis. You just tacked on redundant labels. How do the strands wind through the carabiners?
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rightarmbad
Apr 5, 2010, 6:03 AM
Post #34 of 45
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The results in the most simple interpretation simply reflect the tape binding where it crosses.
This creates two separate cells that share a common piece that therefore gets twice the load of the others.
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cracklover
Apr 5, 2010, 3:07 PM
Post #35 of 45
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rightarmbad wrote: The results in the most simple interpretation simply reflect the tape binding where it crosses.
As the tape binds, it should get closer and closer to the situation in which the tape is fixed between biners, which would result in the first force diagram I posted:
In reply to: This creates two separate cells that share a common piece that therefore gets twice the load of the others.
Not sure how you arrive at this. The load should be equally shared between the bottom two biners. Of the three upper biners, each gets two strands. Not sure why you would think the strands to the middle (upper) biner would somehow be transmitting more force than the strands to the outer two (upper) biners.
GO
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ptlong
Apr 5, 2010, 9:02 PM
Post #36 of 45
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cracklover wrote: You can't just state that it's flawed.
You're choosing to ignore the angle which at around 90 degrees results in a fairly large error. Notice how their measurements for the anchors add up to quite a bit more than the load.
In reply to: As far as I can tell, the strands wind through the carabiners exactly as I stated: A -> B -> C -> D -> E -> F -> A
What I meant was how they go through the carabiners and which strands are on top or bottom. It's possible to make more than one anchor that fits your schematic. When I look at a closeup of the photo I can't really be sure how the strands are going through the center. Although you've said you aren't sure either, can you label the photo? Where do these strands go with respect to the carabiners and one another?
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ptlong
Apr 5, 2010, 9:06 PM
Post #37 of 45
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cracklover wrote: As the tape binds, it should get closer and closer to the situation in which the tape is fixed between biners, which would result in the first force diagram I posted
This isn't correct. If the angle were zero as you're treating it, the stretch, and hence the tension, in each strand would be identical.
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cracklover
Apr 5, 2010, 9:12 PM
Post #38 of 45
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ptlong wrote: cracklover wrote: You can't just state that it's flawed. You're choosing to ignore the angle which at around 90 degrees results in a fairly large error.
No it doesn't. I'm not discussing the total force, but rather the distribution of force amongst the anchors. Which, ignoring friction, is unchanged by the angle between anchors.
In reply to: In reply to: As far as I can tell, the strands wind through the carabiners exactly as I stated: A -> B -> C -> D -> E -> F -> A What I meant was how they go through the carabiners and which strands are on top or bottom. It's possible to make more than one anchor that fits your schematic. When I look at a closeup of the photo I can't really be sure how the strands are going through the center. Although you've said you aren't sure either, can you label the photo? Where do these strands go with respect to the carabiners and one another?
I have no idea. Ignoring friction, it makes no difference which strands are on top, and which aren't. If your argument is that my schematic is right (ignoring friction), come out and say so.
But I think that your argument is that you have no idea what's going on, and think that I shouldn't claim that I do.
Until you have a better theory to propose, I'm done discussing the matter with you.
GO
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cracklover
Apr 5, 2010, 9:14 PM
Post #39 of 45
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ptlong wrote: cracklover wrote: As the tape binds, it should get closer and closer to the situation in which the tape is fixed between biners, which would result in the first force diagram I posted This isn't correct. If the angle were zero as you're treating it, the stretch, and hence the tension, in each strand would be identical.
Wrong. I don't think you understand the basic physics of the situation.
Cheers!
GO
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ptlong
Apr 5, 2010, 10:14 PM
Post #40 of 45
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cracklover wrote: I have no idea... I think that your argument is that you have no idea...
To me it's ambiguous, to you it's certain. I was hoping you would explain how you are interpreting the photo since it is difficult to discern the features. I can see evidence for either interpretation but no slam dunk. What happens to those strands in the center is important for that reason. But from your perspective the other information makes what happens in the center irrelevant.
As I've said, I think it's one of two possibilities: the one you advocate and the one described (and illustrated) on the first page of this thread as two sliding Xs with four strands going to the center.
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ptlong
Apr 5, 2010, 10:28 PM
Post #41 of 45
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cracklover wrote: ptlong wrote: cracklover wrote: As the tape binds, it should get closer and closer to the situation in which the tape is fixed between biners, which would result in the first force diagram I posted This isn't correct. If the angle were zero as you're treating it, the stretch, and hence the tension, in each strand would be identical. Wrong. I don't think you understand the basic physics of the situation.
Oh come on Gabe, I know you're better than that. With the strands bound like a tied cordelette it's a simple application of Hooke's Law: six equal-length strands all displaced by the same amount --> same tensions.
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cracklover
Apr 5, 2010, 10:46 PM
Post #42 of 45
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ptlong wrote: As I've said, I think it's one of two possibilities: the one you advocate and the one described (and illustrated) on the first page of this thread as two sliding Xs with four strands going to the center.
Yes, I've described my supposition of what it could be. But while I've repeatedly asked you for your theory, you have given me nothing. What is the two sliding-X configuration you are claiming fits the photo? If such a theory has been described and illustrated, I haven't seen it.
And you're wrong, with fixed lengths, it's not the same as a cordelette. There's no point in explaining to you why, since it's already been illustrated, and you just don't seem to get it. But if anyone else is curious, I'd be happy to explain.
GO
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ptlong
Apr 5, 2010, 11:24 PM
Post #44 of 45
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cracklover wrote: And you're wrong, with fixed lengths, it's not the same as a cordelette.
Fixed lengths IS a cordelette.
In reply to: There's no point in explaining to you why, since it's already been illustrated, and you just don't seem to get it. But if anyone else is curious, I'd be happy to explain.
Ha ha, okay Gabe. You can go now.
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cracklover
Apr 6, 2010, 3:39 AM
Post #45 of 45
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ptlong wrote: cracklover wrote: Yes, I've described my supposition of what it could be. But while I've repeatedly asked you for your theory, you have given me nothing. What is the two sliding-X configuration you are claiming fits the photo? If such a theory has been described and illustrated, I haven't seen it. There's a photo of it on the first page in this thread. Here:  [image]http://i44.tinypic.com/wmckd4.jpg[/image] And since it wasn't as easy to decipher as I thought it would be for you, here's a diagram a-la-cracklover:  A->B->C->F->G->H->E->D->A
If you thought the photo was representing that, why didn't you just say so?!
GO
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