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Chockstone Forum - General Discussion

General Climbing Discussion

 Page 1 of 4. Messages 1 to 20 | 21 to 40 | 41 to 60 | 61 to 79
Author
bow line

PreferKnitting
23/08/2006
4:25:27 PM
looky here, quite an interesting read....

The Secret Flaw of a Bowline (http://www.allaboutknots.com)

"...Many experienced not tyers are surprised to discover that the Bowline, which they esteem so highly, has a secret flaw. This knot has long been the favorite fixed-loop knot because it is so easy to tie and it works so well. Everyone knows that it holds securely when arranged and applied in the normal way, with the standing part attached at one end and a weight suspended from the loop at the other end. What few knot users seem to realize is that a sharp jerk that pulls the tail to one side can deform a Bowline. If you happen to snag it so that the tail and the right leg of the loop are yanked hard in opposite directions, the structures may not be stable enough to resist deformation. The bight can straighten out and disappear and the hitch that circles the bight can be transformed into a slip knot. If the knot is deformed in this way, the hitch will no longer have either squeezing power or anything to squeeze against. It will not be able to create enough friction to hold the knot together and can be easily stripped off.

Every time I demonstrate this marvel to a group of knot tyers, someone responds “Wow,” and someone else calls out “Do that again.”

These responses indicate that there is a gap between the way unstable knots behave and our awareness and understanding of their instability. The fatal flaw of a Bowline is that it depends on the stability of one exposed bight. Although the tail is protected somewhat by its position inside the right leg, it can easily be snagged. Ashley comments that “Properly tied in ordinary rope, there is little or no danger of a Bowline Knot’s capsizing before the breaking point of the rope itself is reached” (186). But he says nothing about the effect of a strong snag or yank to the side on the tail.

Analysis of a few examples of unstable knots reveal some of the complexities of studying knot stability. Although these knots are quite secure when they are loaded in the way they were designed for, they can be unstable and become insecure when they are not loaded that way. The study of knot stability leads in numerous fascinating directions, with many applications, both practical and theoretical...."

manacubus
23/08/2006
4:38:56 PM
So, anyone actually use a bowline without a stopper knot? (Which is what the above is warning us about). No? Good.

PreferKnitting
23/08/2006
5:07:16 PM
Um, no, the article mentions nothing about stopper knots. Rather it discusses the stabiltiy of this knot. But it's good that you pointed out a stopper knot is essential with this tie in method.

A- for you, comprehension let you down there mate ; )

sliamese
23/08/2006
8:18:53 PM
...and if you soak your rope in battery acid, leave it in the oven and drop rocks on it, it might not withstand a rope jump off taipan...

AlanD
23/08/2006
8:30:47 PM
I'm not interested in getting into a debate about the affect various knots have on rope strength, I assume most people know the basic figures and how close they operate to the breaking limit of their ropes.

I will point out that a bowline was never designed for kermantel ropes (cored with sheath), but for the traditional twisted rope. With kermanel ropes, unless the bowline is under constant load it can slip. If you're going to use a bowline in a situation where your life is dependent on it, then make sure that stopper knot is there. In sailing, I've had heaps of bowlines fail.

Nick Kaz
23/08/2006
8:57:37 PM
Sorry, but I fail to see how you can make this knot invert, please show me. Who climbs on an un-rethreaded bowline anyhow? As far as I can tell this article is irrelevant to climbing.

AlanD
23/08/2006
9:15:14 PM
On 23/08/2006 Nick Kaz wrote:
>Who climbs on an un-rethreaded bowline anyhow?

You might be shocked what you'll see people use when you look closely and I don't mean just with knots. Lots of accidents just waiting to happen through a lack of knowing any better.

Hawkman
23/08/2006
10:06:26 PM
i climb in a non retreaded bowline. i do a double twist of the rope and have a stopper knot on it.
anthonycuskelly
24/08/2006
7:26:22 AM
PK, actually, I'd say Lee's just skipped the skips he used to get to that conclusion. Basically the problem can't happen if you have rethreaded and then a properly tied stopper, because the knot can't be arranged in the directions mentioned. Lee's just gone straight to the conclusion.

I'm going to be more paranoid about my stoppers on bowlines now (I alternate between Fig-8 and bowline), they're always there anyway, but I'll be doubly sure of them now.

JJ
24/08/2006
8:25:10 AM
Got the re-threaded bowline. It hasn't come undone.....yet.

manacubus
24/08/2006
9:55:24 AM
>Um, no, the article mentions nothing about stopper knots.
No it doesn't - which is exactly my point. How can you unstabilise the knot using the tail (as described) if the tail is firmly tied using a stopper? Which is what every climber who uses a bowline does.

On 23/08/2006 steve wrote:
>i climb in a non retreaded bowline. i do a double twist of the rope and
>have a stopper knot on it.

Same here steve.

nmonteith
24/08/2006
10:19:56 AM
On 24/08/2006 manacubus wrote:
>On 23/08/2006 steve wrote:
>>i climb in a non retreaded bowline. i do a double twist of the rope and
>>have a stopper knot on it.
>
>Same here steve.

Same here!

Paulie
24/08/2006
10:20:46 AM
Unless the loop holding the stopper knot from pulling through fails or becomes grossly enlarged (which by cinching will never happen), then there is no way in hell a rethreaded bowline is ever going to come undone.
CanBeDone
24/08/2006
10:22:09 AM
I’ve been using the double bow line for 10 years or so and never had any problems. I must admit I have had the “stopper knot” come undone on the odd occasion, but still the blow line holds. Every one that uses the blow line for tying in do so for there own reasons. If they have had a scare from using it, I’m sure they would had changed there ways
Bob Saki
24/08/2006
10:37:50 AM
Just for my own knowledge is there anything wrong with just using a rethreaded figure 8 as a tie in if it is the safer knot?

or does it just come down to personal preferrence?

Hawkman
24/08/2006
10:45:46 AM
undoing a figure of 8 after working a project can be harder than pulling the moves on the route!


nick kaz
24/08/2006
12:47:48 PM
ok, Steve, Neil and lee thanks for that. Possibily I should have said backed up rather than rethreaded?
NEVERCLIMBED32
24/08/2006
2:21:31 PM
On 23/08/2006 AlanD wrote:

>You might be shocked what you'll see people use when you look closely
>and I don't mean just with knots. Lots of accidents just waiting to happen
>through a lack of knowing any better.

I think this is the point here. When enthusiasim outweights knowledge (or ability for that matter) accidents are just waiting to happen. There is no certificate of competancy for climbing and many don't know any better than the bad habits taught to them by mates who introduce them to the sport.
Didn't we just have a thread "What knot to tie a cordolette ?"
NEVERCLIMBED32
24/08/2006
2:31:15 PM
Another interesting read is

http://www.chockstone.org/TechTips/ProtectingAnAbseil.htm

I was suprised by the poor performance of the klemhiest knot which I always use for abseiling, prusiking, etc. Just wonder what others do to protect an abseil.

nmonteith
24/08/2006
2:47:11 PM
On 24/08/2006 NEVERCLIMBED32 wrote:
>Just wonder what others do to protect
>an abseil.

Double ropes = Petzel Shunt
Single ropes - Gri-gri (or Eddy!)

 Page 1 of 4. Messages 1 to 20 | 21 to 40 | 41 to 60 | 61 to 79
There are 79 messages in this topic.

 

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