Author Topic: Fishing Knots - Joining Lines  (Read 40886 times)

roo

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Re: Fishing Knots - Joining Lines
« Reply #45 on: June 29, 2010, 05:44:51 PM »
It seems that that the Zeppelin Bend doesn't put as much stress on a rope as does the Double Fisherman.  The angles in the Zeppelin Bend are not as extreme.  So, perhaps the rope failure wouldn't happen in the first place.  I don't know, but again I'd be interested to know if the Zeppelin Bend would cause the rope to fail in the same manner.  I understand that you're not interested, and that's fine.  I am.
But the very report you cited shows on page 5 how the Double Fisherman's Knot is nearly as strong as the Triple Fisherman's Knot which is well respected for strength!

In the strength arena, it doesn't make sense to say that you'd prefer a weaker knot (Zeppelin in this case) to a stronger knot just because the stronger knot has an unusual behavior after rupture.
« Last Edit: June 29, 2010, 05:49:39 PM by roo »
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knot4u

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Re: Fishing Knots - Joining Lines
« Reply #46 on: June 29, 2010, 06:15:35 PM »
It seems that that the Zeppelin Bend doesn't put as much stress on a rope as does the Double Fisherman.  The angles in the Zeppelin Bend are not as extreme.  So, perhaps the rope failure wouldn't happen in the first place.  I don't know, but again I'd be interested to know if the Zeppelin Bend would cause the rope to fail in the same manner.  I understand that you're not interested, and that's fine.  I am.
But the very report you cited shows on page 5 how the Double Fisherman's Knot is nearly as strong as the Triple Fisherman's Knot which is well respected for strength!

In the strength arena, it doesn't make sense to say that you'd prefer a weaker knot (Zeppelin in this case) to a stronger knot just because the stronger knot has an unusual behavior after rupture.

How is the Triple Fisherman a stronger knot than the Zeppelin Bend?  I haven't seen any evidence.

I'm not even convinced the Triple Fisherman is more secure generally.  I'm not referring to your shake test.  I mean brute force pulling in slippery rope.

roo

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Re: Fishing Knots - Joining Lines
« Reply #47 on: June 29, 2010, 06:23:51 PM »
How is the Triple Fisherman a stronger knot than the Zeppelin Bend?  I haven't seen any evidence.

I'm not even convinced the Triple Fisherman is more secure generally.  I'm not referring to your shake test.  I mean brute force pulling in slippery rope.
You're avoiding the issue.  Why would you judge strength not by percentages of rope strength but by irrelevant behavior after rupture?

The tests you cited made no mention of slipping before rupture.  Slipping after rupture isn't a security issue.
« Last Edit: June 29, 2010, 06:25:24 PM by roo »
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knot4u

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Re: Fishing Knots - Joining Lines
« Reply #48 on: June 29, 2010, 06:34:13 PM »
How is the Triple Fisherman a stronger knot than the Zeppelin Bend?  I haven't seen any evidence.

I'm not even convinced the Triple Fisherman is more secure generally.  I'm not referring to your shake test.  I mean brute force pulling in slippery rope.
You're avoiding the issue.  Why would you judge strength not by percentages of rope strength but by irrelevant behavior after rupture?

The tests you cited made no mention of slipping before rupture.  Slipping after rupture isn't a security issue.

I'm right at the issue that I original brought up.

According to the test in the source I cited above, "The sheath breaks at the knot and the slippery core unties, pulling the sheath through."

That is, the sheath breaks at the Double Fisherman Bend.  I'm wondering if that same sheath would break at the Zeppelin Bend in the first place.  That brought up my comment about how the Zeppelin Bend may be easier on the rope than is the Double Fisherman Bend.  I don't know, but would like to know.

« Last Edit: June 29, 2010, 06:37:19 PM by knot4u »

roo

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Re: Fishing Knots - Joining Lines
« Reply #49 on: June 29, 2010, 06:39:18 PM »
I'm right at the issue that I original brought up.
In response to my request for reports of slippage, you cited an article that showed no slippage before rupture.
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knot4u

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Re: Fishing Knots - Joining Lines
« Reply #50 on: June 29, 2010, 06:47:28 PM »
I'm right at the issue that I original brought up.
In response to my request for reports of slippage, you cited an article that showed no slippage before rupture.

I'd classify the issue in the report as being a security issue.  The definition of security is the ability of a rope to resist slippage.  Thus, there's the link to your question about slippage.  Anyway, the important thing to me is that there is a failure in the Double Fisherman Bend, as I explained above.  The failure is a security issue and/or strength issue.  Whatever you want to call it, there is an issue.

Again, I'm wondering if the Zeppelin Bend would have the same failure in the same test.  You may continue to argue your point.  However, I'm primarily concerned with that sentence I put in bold right there.

roo

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Re: Fishing Knots - Joining Lines
« Reply #51 on: June 29, 2010, 06:57:58 PM »

I'd classify the issue in the report as being a security issue.  The definition of security is the ability of a rope to resist slippage.
Not after rupture.  After rupture, it's game over.  Once a rope ruptures and begins (in that split second) losing cross-sectional material, there's no going back.

I'm done trying to think of different ways to explain this.  Security issues only apply before rupture.  It shouldn't need to be said.

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knot4u

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Re: Fishing Knots - Joining Lines
« Reply #52 on: June 29, 2010, 07:05:51 PM »

I'd classify the issue in the report as being a security issue.  The definition of security is the ability of a rope to resist slippage.
Not after rupture.  After rupture, it's game over.  Once a rope ruptures and begins (in that split second) losing cross-sectional material, there's no going back.

I'm done trying to think of different ways to explain this.  Security issues only apply before rupture.  It shouldn't need to be said.

Well damn, if a person is going to use that type of rope and if it is known that the Zeppelin Bend won't cause a rupture in that type of rope, I would think the user of that rope would want to know such information about the Zeppelin Bend.

This is the "Practical Knots" Forum, not the "The Theoretical Parameters for Knots" Forum.
« Last Edit: June 29, 2010, 07:06:26 PM by knot4u »

knot4u

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Re: Fishing Knots - Joining Lines
« Reply #53 on: June 29, 2010, 07:08:25 PM »
I still haven't seen evidence of how the Triple Fisherman Bend is stronger than the Zeppelin Bend.  Above, Roo, you state that like it's a given:

In the strength arena, it doesn't make sense to say that you'd prefer a weaker knot (Zeppelin in this case) to a stronger knot just because the stronger knot has an unusual behavior after rupture.

I'd guess the Zeppelin Bend is stronger because the angles within the knot are knot as extreme.
« Last Edit: June 29, 2010, 07:10:47 PM by knot4u »

roo

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Re: Fishing Knots - Joining Lines
« Reply #54 on: June 29, 2010, 07:10:51 PM »

Well damn, if a person is going to use that type of rope and if it is known that the Zeppelin Bend won't cause a rupture in that type of rope, I would think the user of that rope would want to know such information about the Zeppelin Bend.

Won't cause a rupture?

All knots eventually rupture in any rope.   No rope is indestructable.  No knot can be stronger than the rope.  These rupture issues are all questions of strength percentages, not security, not slippage.  
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knot4u

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Re: Fishing Knots - Joining Lines
« Reply #55 on: June 29, 2010, 07:17:39 PM »

Well damn, if a person is going to use that type of rope and if it is known that the Zeppelin Bend won't cause a rupture in that type of rope, I would think the user of that rope would want to know such information about the Zeppelin Bend.

Won't cause a rupture?

All knots eventually rupture in any rope.   No rope is indestructable.  No knot can be stronger than the rope.  These rupture issues are all questions of strength percentages, not security, not slippage.  

I don't care what label you put on it.  Call it "all of the above" if you want.  For about the third time, I don't care what you call the issue.  There is an issue.  There is a rupture difference between the knots (Double Fisherman Bend and Zeppelin Bend).  I would like to know about this difference.  Sheesh, this place is impossible.

roo

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Re: Fishing Knots - Joining Lines
« Reply #56 on: June 29, 2010, 07:28:01 PM »
 There is a rupture difference between the knots (Double Fisherman Bend and Zeppelin Bend).  I would like to know about this difference.  Sheesh, this place is impossible.

Repeating your secondary question on strength ad nauseum won't answer it.  The reports than analyze the strength of Double & Triple Fisherman Knots typically do not analyze the strength percentage of the Zeppelin bend in the same set of tests (or at all).

I would have you look at p. 51-52 of this document for even more info on the Double & Triple Fisherman's, however:
http://www.speleo-bg.com/images/stories/pdf/rope1.pdf
« Last Edit: June 29, 2010, 07:33:47 PM by roo »
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knot4u

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Re: Fishing Knots - Joining Lines
« Reply #57 on: June 29, 2010, 08:19:07 PM »
 There is a rupture difference between the knots (Double Fisherman Bend and Zeppelin Bend).  I would like to know about this difference.  Sheesh, this place is impossible.

Repeating your secondary question on strength ad nauseum won't answer it.  The reports than analyze the strength of Double & Triple Fisherman Knots typically do not analyze the strength percentage of the Zeppelin bend in the same set of tests (or at all).

I would have you look at p. 51-52 of this document for even more info on the Double & Triple Fisherman's, however:
http://www.speleo-bg.com/images/stories/pdf/rope1.pdf

So, you have no evidence on whether the Zeppelin Bend is weaker than the Double Fisherman Bend.  You did make that assertion above.

roo

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Re: Fishing Knots - Joining Lines
« Reply #58 on: June 29, 2010, 08:33:23 PM »
 There is a rupture difference between the knots (Double Fisherman Bend and Zeppelin Bend).  I would like to know about this difference.  Sheesh, this place is impossible.

Repeating your secondary question on strength ad nauseum won't answer it.  The reports than analyze the strength of Double & Triple Fisherman Knots typically do not analyze the strength percentage of the Zeppelin bend in the same set of tests (or at all).

I would have you look at p. 51-52 of this document for even more info on the Double & Triple Fisherman's, however:
http://www.speleo-bg.com/images/stories/pdf/rope1.pdf

So, you have no evidence on whether the Zeppelin Bend is weaker than the Double Fisherman Bend.  You did make that assertion above.
Someone did some very limited tests and found that the Zeppelin Bend was weaker than the Flemish (Figure Eight) bend:

Now in my other Zeppelin bend thread, Pulling a Zeppelin bend to failure... I did break it. Since I don't have a way to break test non-knotted rope, I can only go by the manufacturer's published MBS for 10mm PMI of 6070 lbs. That reduces the strength of the rope to about 63% of the rope's MBS.

Since I couldn't measure the non-knot break strength of the rope, I decided to at least pull an F8 bend for comparison. It broke at about 66% of the ropes MBS.

66% seems a bit low for an F8 bend though. That would suggest that the break strength, 63%, of the ZB may be a bit low too.

http://www.treebuzz.com/forum/showflat.php?Cat=0&Number=228120&page=0&fpart=all&vc=1

And the speleo link noted that the Double Fisherman's Knot was "noticably" stronger than the Flemish Bend.

« Last Edit: June 29, 2010, 08:42:56 PM by roo »
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knot4u

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Re: Fishing Knots - Joining Lines
« Reply #59 on: June 29, 2010, 09:24:57 PM »
Since we're comparing the Zeppelin Bend to the Double/Triple Fisherman Bend, we might as well be comparing the Double/Triple Zeppelin Bend instead.

Discussions about strength are always a bit hokie.  There are always a few variables that are conveniently ignored for the sake of continuing the discussion.

 

anything