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bluefoxicy
Apr 15, 2012, 11:31 PM
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The gym I hang in refuses the yosimite bowline as a valid climbing knot. It's pretty much my favorite knot for the general purpose (that being of securing something with a loop).
The obvious reason I favor the Yosimite bowline is because it's easy to tie, although I'm told it's hard to verify. That aside, there are more technical reasons I want to put up here to hear some other thoughts on this.
Let's start with the knots that the gym allows.
First off, they allow the figure 8 retrace knot as a valid climbing knot. I'll likely use this in all cases since yosimite bowline is not allowed. It takes longer to tie and is harder to slide more slack through for a back-up knot, but it's a very secure knot. The Figure 8 retrace knot is an extremely secure knot, self-tightening under any direction of load, with lots of internal friction and clamping against everything.
They also allow the double bowline for lead climbing. Lead climbing carries extra risk for longer falls, so a secure knot is critical.
In the Bowline, there is a loop (formed first), a bight (formed by running the free end up through the loop, around the work end, and back down through the loop), and a free end pointing inside. The Bowline relies on friction between the bight and the loop: the free end can easily slip back, but unless it is negatively loaded (pushed back) it probably won't. Load on the bight from the opposite end (the end loaded by a falling climber) will clamp the bight around the work end of the knot.
That means the Bowline is theoretically pretty secure, and in reality it performs well. The double bowline, accepted by the climbing gym, is more secure because of increased frictional force by a second turn of the loop.
Claiming that the double bowline is necessary for improved security of the knot stands out to me: this claim asserts that the friction of the loop to hold the free end in place is significant and important.
That's where I have a problem.
Let's reference here:
The Yosemite bowline finishes a normal bowline by first looping the free end behind the right side of the working loop. Then it comes around, behind the entire knot, and then up through the bight. Tightening the knot not only adds extra friction to the working end of the work loop, but also clamps the free end at the critical position--the Yosimite Bowline acts as its own back-up knot! On top of this, you also proceed to tie a regular back-up knot, of course; but it still stands that the Yosimite bowline clamps its free end firmly, providing a much more secure hold than a Bowline or Double Bowline.
To summarize briefly:
- the bowline and double bowline clamp the final bight around the work end when under load, providing a high amount of friction to prevent the free end from sliding out--the free end is doing the clamping, not being clamped. If the frictional forces fail during this loading--an extremely unlikely event--the knot would immediately come undone.
- The Yosemite finish puts two more high-friction bends on the free end, then clamps it under what is the final bight in a regular bowline. When loaded in the same way, the Yosimite bowline clamps down hard on the free end to hold it in place. If the frictional forces preventing the bight from sliding were to fail during this clamping, the free end would be held via clamping force (and more friction at 2 subsequent points), simply tightening the knot.
Because of this, I'm inclined to NOT use the double bowline when climbing and stick with the double figure 8, which they allow and which is also a self-tightening, extremely secure knot.
(Yes, I'm aware that clamping works via friction; but clamping generates friction from at least two ends and also deforms the rope such that an increased amount of energy would be needed beyond simply overcoming friction. The rope segment that's clamping down is experiencing at best half as much friction as what it clamps.)
Is this insane? Is it a failed assessment that the Double Bowline is fundamentally less secure than a Double 8 or a Yosimite? I understand that it's probably adequate for the task--obviously either history shows or everyone involved in climbing is too stupid to notice people keep dying from failed double bowlines, and the later case seems unlikely--but it's not a decision between something ridiculously more difficult and something with a much lower cost associated. The trade-off using a Double 8 versus a Double bowline is effectively nil, so I'd rather stick with what's more secure.
(This post was edited by bluefoxicy on Apr 15, 2012, 11:32 PM)
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lofstromc
Apr 16, 2012, 2:11 AM
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If you want to climb at that gym, you probably have to follow that gyms rules.
Its not a discussion about what is safer, blah, blah, blah. ITS POLICY.
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bluefoxicy
Apr 16, 2012, 2:39 AM
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Actually, you're wrong. This is a discussion about what is safer.
In reply to: First off, they allow the figure 8 retrace knot as a valid climbing knot. I'll likely use this in all cases since yosimite bowline is not allowed.
And
In reply to: Because of this, I'm inclined to NOT use the double bowline when climbing and stick with the double figure 8, which they allow and which is also a self-tightening, extremely secure knot. [..] Is this insane? Is it a failed assessment that the Double Bowline is fundamentally less secure than a Double 8 or a Yosimite?
Make a habit of reading things before replying, and comprehending what you read.
(This post was edited by bluefoxicy on Apr 16, 2012, 2:40 AM)
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lofstromc
Apr 16, 2012, 2:51 AM
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You should definitely present all your skills and knowledge to those fools at your local gym and demand to tie in how you want, not how they say.
I am so happy that you are the first person ever to post this most important and ground shattering information.
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bluefoxicy
Apr 16, 2012, 2:58 AM
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lofstromc wrote: You should definitely present all your skills and knowledge to those fools at your local gym and demand to tie in how you want, not how they say. I am so happy that you are the first person ever to post this most important and ground shattering information.
You're being a dick.
If you had bothered to read--twice--you would have undoubtedly noticed that the gym accepts the figure 8 retrace I have decided to go with. You would have noticed that the question was mainly if the assessment of the double bowline being weak for the reasons I cited was valid. This kind of querying is done to verify that self-determined information is valid, which avoids the situation of self-determining incorrect information and doing something stupid (and also serves as information sharing if the information is valid, or for refinement if the information is only semi-valid).
Also, as an aside, I actually am that kind of person that tends to move things forward. At my dojo, we follow the proscribed method of tying our Gi belts by crossing left side over right side, then left side over right side. This is a granny knot, and often comes undone. I intend to suggest to my sensei and to the regional Shihan that we modify this to make the first cross right over left, preserving the aesthetic while moving to the more stable reef knot and preventing peoples' Gi from falling open repeatedly during training.
If I don't suggest it, nobody else will, you see.
Your responses are not useful. You neither validate nor invalidate the technical claims I have made, and thus have not given me any useful information. When I am outside the gym, I can do one of two things: espouse to climbers going up sheer natural cliffs that the Yosemite bowline is superior and they should use it; or espouse to them that it is inferior and should be avoided in favor of the double bowline. In either case, if I am incorrect, I am putting said climbers in peril; in the case that the Yosemite bowline is superior and I convince many others to use it and supply a valid verification method, I am advancing the state of the art by spreading little-known knowledge. Outside the gym there is no such policy, thus these distinctions are important.
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jt512
Apr 16, 2012, 3:10 AM
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bluefoxicy wrote: [T]he free end [of a bowline] can easily slip back, but unless it is negatively loaded (pushed back) it probably won't.
That is false. A bowline can loosen and eventually completely untie itself without pushing on the free end, as I recently noted here. Tying in with single or double bowline without a backup knot is patently unsafe.
Jay
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dan2see
Apr 16, 2012, 3:12 AM
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bluefoxicy wrote: ... You're being a dick. ... Also, as an aside, I actually am that kind of person that tends to move things forward. At my dojo, ...
You actually are that kind of person that tends to go on and on and on about how your way is valid, correct, and useful.
Your problem, however, is that the gym already has a way that is valid, correct, and useful.
So what will you do about it? Gripe gripe gripe? Or shut up and climb?
My advice to you is to shut up and climb.
And learn later.
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bluefoxicy
Apr 16, 2012, 3:30 AM
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jt512 wrote: That is false. A bowline can loosen and eventually completely untie itself without pushing on the free end, as I recently noted here. Tying in with single or double bowline without a backup knot is patently unsafe. Jay
I toyed with a double bowline a bit, it seems if I repeatedly load and unload the bowline in alternation (load the hanging end, then unload that and load the loop), the free line will creep maybe half a centimeter.
The Yosemite doesn't suffer from this at all. The double figure 8 also doesn't seem to suffer from this.
The climbing gym I climb at proscribes some kind of simple knot that I dislike as a back-up. It forms an X on one side and an = on the other, that's the verification mechanism. It's used to back up both the Double Bowline and the Double 8 Retrace.
dan2see wrote: You actually are that kind of person that tends to go on and on and on about how your way is valid, correct, and useful.
That's exactly what I'm trying to determine. So far, I've gotten two replies--including yours--that don't confirm or deny anything I've said, but instead complain that I'm not blindly following what the guys at the gym said like a moron. These responses aren't useful: they don't address the question or comment on any technical issue, but rather just complain that I'm experiencing thoughtfulness and applying some form of critical thinking to things that could very well severely injure or kill me.
I've also gotten one that appears to agree with me on the double bowline being a weak and unsafe knot, though no word on if tying in with the Double 8 Retrace is a better option. Still, this response pushes me away from the Double Bowline, and the only place to go in the gym is the Double 8 Retrace, so this provides the illusion of encouraging that (notably, the encouragement is illusionary and not implied: asserting that the Double Bowline is unsafe does not imply that the Double 8 is safe).
I'm quite familiar with playing with things that can kill me--I used to build guitar tube amps as a hobby, a few mistakes got me a good 780V DC coming across what was supposed to be 344V early on, while I was trying to live-test a hot circuit to bias tubes--and I tend to try to fill out my knowledge and explore a little. If you want to be a lemming that's your prerogative.
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bluefoxicy
Apr 16, 2012, 3:34 AM
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^^^ This is helpful and faster way to kill a discussion that's not worth having for the 47th time.
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jt512
Apr 16, 2012, 3:58 AM
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bluefoxicy wrote: jt512 wrote: That is false. A bowline can loosen and eventually completely untie itself without pushing on the free end, as I recently noted here. Tying in with single or double bowline without a backup knot is patently unsafe. Jay I toyed with a double bowline a bit, it seems if I repeatedly load and unload the bowline in alternation (load the hanging end, then unload that and load the loop), the free line will creep maybe half a centimeter.
Nope. I just tried it, and the double bowline can also completely untie just by continuously shaking it by the standing end of the rope, although it required about four times as much shaking as the single bowline. Without a back-up knot, for use as a tie-in, the single and double bowline are death knots.
Jay
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bluefoxicy
Apr 16, 2012, 5:05 AM
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jt512 wrote: Nope. I just tried it, and the double bowline can also completely untie just by continuously shaking it by the standing end of the rope, although it required about four times as much shaking as the single bowline. Without a back-up knot, for use as a tie-in, the single and double bowline are death knots. Jay
Interesting. I can't get the double to fail like that, but I've gotten it to loosen a bit. The single does simply fail. These stresses are similar to normal climbing but with more force, so you'd need a lot more cycling--long climbs, basically. Though apparently one guy died.
I think you're mistaken about the back-up. When NASA launched the Space Shuttle Columbia, the engineers complained that the main seals on the fuel section would likely fail. It was decided that they had Backup #2 and Backup #3 to handle Main Seal #1 failure, so it would be fine to launch. In other words, NASA launched a shuttle relying on backup systems to provide primary operation.
The shuttle blew up.
Everybody died.
NASA now holds the official stance written in policy that backup systems are for backup only. Relying on a backup to handle a primary function where the primary system is known unreliable is unacceptable.
According to you, a double bowline simply doesn't work. It's prone to failure. I have explained this as being due to the topology of the knot providing inadequate forces to prevent the free end from receding into the knot under certain theoretical conditions; you have asserted that conditions exist which are not theoretical but which do indeed allow the knot to loosen such that force applied to the loop would cause the free end to recede.
The free end is not secured. A back-up knot secures the free end.
According to NASA, a back-up used to handle a known unreliable primary function is incorrect: the primary function is unsafe, therefor the entire system relies on the back-up, therefor the back-up is primary.
A double bowline with a back-up knot doesn't have a back-up knot. The back-up knot provides an anchor for the free end so that the bowline does not come undone under failure conditions that occur during normal use. That makes the back-up knot part of the primary safety system, meaning your backed-up double bowline isn't actually backed up.
Which, again, brings me back to Yosemite bowline with a fisherman's knot backup or Double 8 Retrace with a fisherman's knot backup, both much stronger, actually secure knots with an actual back-up rather than a secondary knot to handle a primary function that the primary knot can't handle reliably.
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dan2see
Apr 16, 2012, 5:39 AM
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bluefoxicy wrote: dan2see wrote: You actually are that kind of person that tends to go on and on and on about how your way is valid, correct, and useful. That's exactly what I'm trying to determine. So far, I've gotten two replies--including yours--that don't confirm or deny anything I've said, ...
You don't have to determine anything. I don't have to confirm or deny anything that anybody said.
Your gym has a rule. That's not right, it's not wrong. It's their gym. It's their rule.
So now, what you have to learn, is how to get along with others in a public place. It's not about knots, and their safety, anymore. It's about you, and your preference to troll and browbeat and talk to death. Talk talk talk.
Famous quotation wrote: Those that can, climb. Those that can't, talk about it.
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jt512
Apr 16, 2012, 5:47 AM
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bluefoxicy wrote: jt512 wrote: Nope. I just tried it, and the double bowline can also completely untie just by continuously shaking it by the standing end of the rope, although it required about four times as much shaking as the single bowline. Without a back-up knot, for use as a tie-in, the single and double bowline are death knots. Jay Interesting. I can't get the double to fail like that, but I've gotten it to loosen a bit.
Are you actually tying-in to the rope. I wasn't able to get the double bowline to fail by shaking it if it was just free-hanging, but tying in, it failed in under a minute.
In reply to: I think you're mistaken about the back-up. When NASA launched the Space Shuttle Columbia, the engineers complained that the main seals on the fuel section would likely fail. It was decided that they had Backup #2 and Backup #3 to handle Main Seal #1 failure, so it would be fine to launch. In other words, NASA launched a shuttle relying on backup systems to provide primary operation. The shuttle blew up. Everybody died. NASA now holds the official stance written in policy that backup systems are for backup only. Relying on a backup to handle a primary function where the primary system is known unreliable is unacceptable. According to you, a double bowline simply doesn't work. It's prone to failure. I have explained this as being due to the topology of the knot providing inadequate forces to prevent the free end from receding into the knot under certain theoretical conditions; you have asserted that conditions exist which are not theoretical but which do indeed allow the knot to loosen such that force applied to the loop would cause the free end to recede. The free end is not secured. A back-up knot secures the free end. According to NASA, a back-up used to handle a known unreliable primary function is incorrect: the primary function is unsafe, therefor the entire system relies on the back-up, therefor the back-up is primary. A double bowline with a back-up knot doesn't have a back-up knot. The back-up knot provides an anchor for the free end so that the bowline does not come undone under failure conditions that occur during normal use. That makes the back-up knot part of the primary safety system, meaning your backed-up double bowline isn't actually backed up.
Your analogy is silly. The fact is, any bowline with a back-up knot, finishing knot, or whatever you want to call it, is bombproof. Single and double bowlines without one are fatalities waiting to happen.
I don't know whether the Yosemite bowline needs a backup or not. I've been wondering the same thing about the water bowline.
Jay
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gosharks
Apr 16, 2012, 6:06 AM
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bluefoxicy wrote: I think you're mistaken about the back-up. When NASA launched the Space Shuttle Columbia, the engineers complained that the main seals on the fuel section would likely fail. It was decided that they had Backup #2 and Backup #3 to handle Main Seal #1 failure, so it would be fine to launch. In other words, NASA launched a shuttle relying on backup systems to provide primary operation. The shuttle blew up. Everybody died. NASA now holds the official stance written in policy that backup systems are for backup only. Relying on a backup to handle a primary function where the primary system is known unreliable is unacceptable. According to NASA, a back-up used to handle a known unreliable primary function is incorrect: the primary function is unsafe, therefor the entire system relies on the back-up, therefor the back-up is primary.
Not sure that I trust your account since:
1. I assume you mean Challenger since this description doesn't fit Columbia.
2. In reply to: Each of the two Space Shuttle Solid Rocket Boosters (SRBs) that comprised part of the Space Transportation System was constructed of six sections joined in three factory joints and three "field joints". The factory joints had asbestos-silica insulation applied over the joint, while the field joints—assembled in the Vehicle Assembly Building at Kennedy Space Center (KSC)—depended on two rubber O-rings, a primary and a secondary (backup), to seal them. (Since the destruction of Challenger, SRB field joints now use three O-rings.
Kinda changes your entire "NASA says that a backup-that-isn't-a-backup" thing you have going..
(This post was edited by gosharks on Apr 16, 2012, 6:08 AM)
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wmshub
Apr 16, 2012, 7:16 AM
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gosharks wrote: In reply to: Each of the two Space Shuttle Solid Rocket Boosters (SRBs) that comprised part of the Space Transportation System was constructed of six sections joined in three factory joints and three "field joints". The factory joints had asbestos-silica insulation applied over the joint, while the field joints—assembled in the Vehicle Assembly Building at Kennedy Space Center (KSC)—depended on two rubber O-rings, a primary and a secondary (backup), to seal them. (Since the destruction of Challenger, SRB field joints now use three O-rings. http://en.wikipedia.org/wiki/Space_Shuttle_Challenger_disaster Kinda changes your entire "NASA says that a backup-that-isn't-a-backup" thing you have going..
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bluefoxicy
Apr 16, 2012, 11:28 AM
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jt512 wrote: Your analogy is silly. The fact is, any bowline with a back-up knot, finishing knot, or whatever you want to call it, is bombproof. Single and double bowlines without one are fatalities waiting to happen. I don't know whether the Yosemite bowline needs a backup or not. I've been wondering the same thing about the water bowline. Jay
My point was it's not a "back-up" if it's providing the primary function because the primary is known faulty. That means the system doesn't have a back-up, and the primary is unsuitable.
gosharks wrote: Do you have a source for all of this? Not sure that I trust your account since: 1. I assume you mean Challenger since this description doesn't fit Columbia.
Yes Challenger, sorry. And on the article you linked:
In reply to: As astronaut Sally Ride cited in questioning NASA managers before the Rogers Commission, it is forbidden to rely on a backup for a Criticality 1 component. The backup is there to provide redundancy in case of unforeseen failure, not to replace the primary device, leaving no backup.
Backup is there for unforseen failure, not to be the primary device.
dan2see wrote: Your gym has a rule. That's not right, it's not wrong. It's their gym. It's their rule. So now, what you have to learn, is how to get along with others in a public place. It's not about knots, and their safety, anymore. It's about you, and your preference to troll and browbeat and talk to death. Talk talk talk.
Let's make this clear: gym policy is tangential to the discussion. The fact is there are other gyms, there are places outside (have you ever been there? It's where the sun is and there are fewer rules, but more snakes), and, even disregarding all that, there are simply bare technical concerns.
It's possible for policy to be stupid. It's possible for policy to be counterproductive or just plain wrong. It's also possible to die at a gym and not manage to sue the owners--besides being dead, climbing is inherently dangerous and you assume all risks. The gym I go to has already filed the waiver I signed covering exactly this: anything that happens to me therein is my fault, even if holds fail, as I should be properly secured or just not that high (bouldering).
Besides that, I mentioned several times in the initial post that the Double 8 retrace is acceptable by gym policy and appears to be a much stronger knot than the Double Bowline, and that that's the knot I plan to use in the gym. Quit bitching that I should use one of their knots when I already said I was going to.
This entire post is supposed to be about the technical merits of one knot over another, not about whining over gym policy. You seem to want to complain that somebody is using critical thinking in a situation where such things can make the difference between life and death. For the record, that makes me intelligent and you a future darwin award winner: I'm actually thinking about things and asking questions, trying to understand the strengths and weaknesses behind various options that are meant to secure my life; while you think it's a good plan to just swallow whatever's given to you without asking about it when it seems unsafe.
As someone who has accepted an oxygen sensor approaching 600 degrees just because a mechanic pulled it out of a hot engine and handed it to me, I can confirm that people who really do know what they're doing will tell you to do incredibly stupid stuff sometimes. Stopping for a moment to think when somebody tells you something can avoid issues where your hand melts off or you fall and die from a weak knot.
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bill413
Apr 16, 2012, 1:00 PM
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bluefoxicy wrote: jt512 wrote: Nope. I just tried it, and the double bowline can also completely untie just by continuously shaking it by the standing end of the rope, although it required about four times as much shaking as the single bowline. Without a back-up knot, for use as a tie-in, the single and double bowline are death knots. Jay Interesting. I can't get the double to fail like that, but I've gotten it to loosen a bit. The single does simply fail. These stresses are similar to normal climbing but with more force, so you'd need a lot more cycling--long climbs, basically. Though apparently one guy died. ...
Doesn't bother you?
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shockabuku
Apr 16, 2012, 1:33 PM
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The water bowline is an interesting knot. I hadn't seen it until last week after reading one of the other threads on bowline variations. One of the sources I saw on it indicates that it's main advantage is enhanced ability to untie after getting wet.
It seems that the properties of the rope, particularly how stiff it is and how tight the sheath, have a lot to do with how well a particular variation of the bowline will hold.
I keep an old Sterling rope in my office to play with knots and besides being somewhat stiff to begin with, it's seen some sheath slippage at the ends (toward the middle) that make it probably a little more stiff. It does not hold an unfinished bowline of any type terribly well.
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cracklover
Apr 16, 2012, 3:05 PM
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shockabuku wrote: It seems that the properties of the rope, particularly how stiff it is and how tight the sheath, have a lot to do with how well a particular variation of the bowline will hold. I keep an old Sterling rope in my office to play with knots and besides being somewhat stiff to begin with, it's seen some sheath slippage at the ends (toward the middle) that make it probably a little more stiff. It does not hold an unfinished bowline of any type terribly well.
Occasionally I meet a rope like this in the field. A few weeks ago I climbed on a friend's new rope. I don't recall what it was, but it simply would not safely hold my double bowline. I did not feel comfortable using that - my preferred tie-in knot - so I fell back on the fig-8 follow-through.
This was the stiffest rope I'd ever seen, but to lesser degrees, the same thing has happened to me from time to time, and is just another example of why I avoid using absolutes like "I always _______" or "You should never _____". Large government agencies and other bureaucratic institutions (like gyms) have requirements on them to set policies for large groups of people. As climbers, we have the opportunity to see the facts on the ground and make the best decision for the exact situation. It's a nice position to be in. Let's honor that by avoiding absolute claims about one knot's suitability or lack thereof.
GO
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bearbreeder
Apr 16, 2012, 3:47 PM
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just use an 8 .... your gym requires it ...
its amazing how much discussion there has been on bowlines and what is "safe" and not ... and all the bowline variations
if RCers get confused ... hows someone who climbs gonna remember it all ... and hopefuly check their partners knots
old ropes, new ropes, stiff ropes ... honestly a tie in knot should hold no matter what ... before you find out mid climb ...
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cracklover
Apr 16, 2012, 4:48 PM
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I've read your OP, and unlike many here, I am happy to engage your question. Tell me if I'm summarizing it adequately here:
My gym does not allow me to use my tie-in knot of choice, and of the choices given, I'm using the fig-8-follow-through, because I don't think the double-bowline is safe. Am I nuts?
It's a reasonable question, but... I do not understand at all what you're claiming to be the failing of the double bowline. Could you try again to explain what about this knot you find to be objectionable, and why this makes it unsafe for the application (leading and following in the gym)?
Thanks,
GO
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jt512
Apr 16, 2012, 5:05 PM
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bluefoxicy wrote: jt512 wrote: Your analogy is silly. The fact is, any bowline with a back-up knot, finishing knot, or whatever you want to call it, is bombproof. Single and double bowlines without one are fatalities waiting to happen. I don't know whether the Yosemite bowline needs a backup or not. I've been wondering the same thing about the water bowline. Jay My point was it's not a "back-up" if it's providing the primary function because the primary is known faulty.
I know that was your point. It's just semantics, as evidenced by the fact that you have to put "back-up" in quotation marks. So call it a "finish" instead of a back-up.
In reply to: That means the system doesn't have a back-up, and the primary is unsuitable.
I agree with you that the knot used to finish a single or double bowline should not be thought of us a backup. However, either knot, with a proper finish, doesn't need any additional backup.
Jay
(This post was edited by jt512 on Apr 16, 2012, 5:08 PM)
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bluefoxicy
Apr 16, 2012, 5:18 PM
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cracklover wrote: My gym does not allow me to use my tie-in knot of choice, and of the choices given, I'm using the fig-8-follow-through, because I don't think the double-bowline is safe. Am I nuts? It's a reasonable question, but... I do not understand at all what you're claiming to be the failing of the double bowline. Could you try again to explain what about this knot you find to be objectionable, and why this makes it unsafe for the application (leading and following in the gym)?
Pretty much.
The double 8 applies clamping force around the middle part from two ends, and a lot of basic friction. It's a very strong knot. It doesn't loosen easily and it self-tightens under load.
The Bowline, in contrast, supplies a knot held in place by weak friction through an unstable loop (the first loop made), with the free end forming a bight around the standing end above this loop. When loaded, the standing end pulls at the bight, loosening up the knot, which is prevented by virtue of the counter-force on the tie-in loop--force supplied on the standing end of the bight, while the free end hangs free. Because of this, the bowline knot tends to shift around a lot under load cycling, but generally hold--if it didn't generally hold, it would be a worthless knot.
The problem I see is that a loading and unloading cycle shifts the bight back, then tugs it down and squeezes the loop, hopefully holding everything together. The movement can slightly back out the free end, though... and if you do that over and over, it fails.
The Yosemite bowline finishes the knot in such away that these failure modes do not exist, clamping the free end and tying the knot such that it simply doesn't come undone in that way under pressure. Part of that is probably from the stable (tightened) state of the knot having the bight standing straight, so loading the standing end doesn't back it out a little anymore; but really it's a lot of complex friction and clamping forces here and there.
The Yosemite bowline not being allowed, and the Double Bowline being a single bowline that has an extra loop to provide more friction as compensation for the failings of the single bowline (i.e. trying the same thing harder rather than just ditching it for a knot that works), it seems to me that sticking with the Double 8 is a lot safer.
As to why I find all this objectionable and unsafe, well... it's hard to argue that something is unsafe when it's in use and past a specific safety threshold (i.e. if 2 people die a decade versus 2 people a century, nobody will care about the difference). My life and my job revolve around adversarial security considerations though: that something has a weakness means that someone will exploit it. A weakness is a failure waiting to happen to somebody, under just the right conditions; fate is as adversarial as determined teenagers, and as well tends to take the easy targets (people with slicker rope, the inexperienced, people who made a minor mistake today...).
I'm pretty geared to base risk assessment on the major cost of a thing--a cripplingly high cost to avoid a small risk is unacceptable--and then on the theoretical merits as not opposed by practical merits (that is, as long as "in practice" things don't happen in way the theory prohibits; it's okay for the theory to show a situation that rarely happens, as long as it doesn't prohibit a situation in theory that really DOES happen in practice). Tying a Double 8 is slightly more tedious than tying any bowline, but it just doesn't matter: it's a few seconds. Yosemite bowline not allowed? Double 8 allowed? Spend the extra few seconds on it. It's not worth the theoretical weaknesses in the bowlines. Theoretically the Double 8 appears stronger anyway (I've seen arguments that the Yosemite is actually the stronger knot), and if you believe that then the only reason to go for a Yosemite Bowline is because it's FAST to tie and untie in comparison without a major safety trade-off.
I know, it's a lot of words for a very small consideration. It's not very easy to summarize without just going, "This one is weak and that one is strong, trust me." If you explain things away that way, you wind up with BioForce all over again: a bunch of people who have never used it, don't know how it works, don't understand what it is, but heard that it was horrible and so the entire world knows BioForce is the most horrid idea that ever came to bicycles.
jt512 wrote: I agree with you that the knot used to finish a single or double bowline should not be thought of us a backup. However, either knot, with a proper finish, doesn't need any additional backup. Jay
Neither does the Double 8, or the Yosemite, but I still back them up--that's what a back-up is: fail safe for a primary system that shouldn't fail in the first place. I think we're basically in agreement here, though.
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jt512
Apr 16, 2012, 5:50 PM
Post #25 of 50
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bluefoxicy wrote: jt512 wrote: I agree with you that the knot used to finish a single or double bowline should not be thought of us a backup. However, either knot, with a proper finish, doesn't need any additional backup. Jay Neither does the Double 8, or the Yosemite, but I still back them up--that's what a back-up is: fail safe for a primary system that shouldn't fail in the first place. I think we're basically in agreement here, though.
None of the "back-ups" for any of these knots—bowline, double bowline, Yosemite bowline, or figure-8—is a real "back-up," in the sense of an independent system that can take over if the primary system fail. In every case, the "back-up" knot serves only to secure the tail of the rope, so that the (primary) knot is less likely to untie. If you are certain (ie, with probability of 1) that the figure 8 or the Yosemite bowline don't need a "back-up," then it is irrational to tie one. The fact that you do "anyway," suggests to me that you're really not certain.
Jay
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