Author Topic: Bowline on a Bight - slip knot mistake!  (Read 8409 times)

Hopkins

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Bowline on a Bight - slip knot mistake!
« on: September 01, 2013, 11:38:48 PM »
Hello!  I'm new here but I have a question that searching the internet alone has not answered.  I recently learnt to tie a "bowline on a bight" but, while doing so, sometimes I ended up with a pair of slipping loops instead of the desired knot.  After a while, I realised that this is the result of "pulling the wrong loops through".  I could not find any reference to this resulting knot, nor could I find any instructions specifically warning of this pitfall.  I was wondering if this distinctly different (let topologically equivalent) slipping knot has a name?

Thanks in advance!
« Last Edit: September 17, 2013, 12:55:23 PM by Hopkins »

kd8eeh

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Re: Bowline on a Bight - slip knot mistake!
« Reply #1 on: September 02, 2013, 04:02:19 AM »
The knot you made is a the same as a polmar knot, used in fishing to secure a hook to the line (although some fishermen will tie a polmar a bit differently, leaving the collar around the hook).

Also, welcome to the forum.

Hopkins

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Re: Bowline on a Bight - slip knot mistake!
« Reply #2 on: September 02, 2013, 06:46:32 AM »
Thank you, on both counts!

I have just confirmed that this is exactly what I meant by way of this animation:

http://www.animatedknots.com/palomar/

brianw

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Re: Bowline on a Bight - slip knot mistake!
« Reply #3 on: February 24, 2017, 05:30:22 PM »
I know this is an old thread but thought I would ask for further comments.
I too was recently tying the B on the B repeatedly (as practice) and noticed that about 10 - 20% of the time I ended up with the Palomar knot. As far as I could tell I was "tying" it correctly and the problem resulted from tightening it the wrong way. Since this would seem to be a situation that could easily happen to an inexperienced user I decided that this would be a very dangerous knot to use in real life when a slipping rather than fixed loop could have disastrous results.
By trial and error I discovered that the Double Bight Figure 8 Loop was much more reliable. Trying to tighten it the wrong way the worst I could do was to get to a form which looked weaker but would still not slip unless strain was placed on one of the bights forming the loop. I'm surprised that such a well known knot as the B on the B has such a weakness and wonder if there are similar (like the Reef knot) that suffer from the same limitation.
Thanks.

Sweeney

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Re: Bowline on a Bight - slip knot mistake!
« Reply #4 on: February 25, 2017, 11:57:23 AM »
The bowline on the bight is easily tied incorrectly largely because some of the instructions in books and online are either wrong or easily confused (I have at least one knot book - The Knot Handbook by Maria Constantino -  where the tying method shown is wrong and a noose results). This is a weakness in the method of tying rather than the knot itself. Below is a link to a YouTube video which is the way I would tie it and teach anyone else - it starts similarly to an ordinary bowline and is thus easy to remember and reliable as a tying method.

https://www.youtube.com/watch?v=FR8tA2Gvq8Y

Sweeney

brianw

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Re: Bowline on a Bight - slip knot mistake!
« Reply #5 on: March 01, 2017, 11:29:10 AM »
Thanks for that reply Sweeney. It is still alarming to me that such a classic knot is easy to tie incorrectly and sometimes described wrongly (or badly) in sources. Personally I will be using and recommending the Double Bight Figure 8 Loop in future unless it has any disadvantages over the B on the B. Do you happen to know of any?
Thanks.

Knutern

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Flat rope extra prone
« Reply #6 on: March 01, 2017, 05:09:52 PM »
It appears for me - after some testing - that flat ropes is more prone to this failure than more traditional rope.

To test the knot reliability I use to hold one of the standing parts (on this kind of knot I choose to call both ends for that) in one hand and for each eye, I pull both eye-legs to see if the knot tends to collapse.
And based on that I'm agreed that the Bowline on a Bight does have this collapsing tendency.

Personally I prefer the Spanish bowline because it doesn't collapse that easy.

I'm aiming for knots that is secure, AND that is easy to untie.

Sweeney

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Re: Bowline on a Bight - slip knot mistake!
« Reply #7 on: March 02, 2017, 06:15:42 PM »
Personally I will be using and recommending the Double Bight Figure 8 Loop in future unless it has any disadvantages over the B on the B. Do you happen to know of any?

Both the double bight figure 8 and the Spanish bowline allow rope to be moved from one loop to the other - this may or may not be a disadvantage depending on your application. The figure 8 is also much more bulky than the bowline but again it depends on your circumstances. The Portuguese bowline also allows movement between the loops but is another option.

Incidentally the B on a B can be tied by first tying an ordinary bowline then completely following the original lead - possibly the safest method of all.

Sweeney

Hrungnir

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Re: Flat rope extra prone
« Reply #8 on: March 02, 2017, 06:54:46 PM »
To test the knot reliability I use to hold one of the standing parts (on this kind of knot I choose to call both ends for that) in one hand and for each eye, I pull both eye-legs to see if the knot tends to collapse.
And based on that I'm agreed that the Bowline on a Bight does have this collapsing tendency.
Hey, you shouldn't load just one of the standing parts of the bowline on a bight. You should load both!

If your rope isn't long enough, and you have to tie the bowline on a bight at the end of the rope, you should secure the none loaded standing part with a bowline. This is demonstrated in The Ashley Book of Knots. The knot number is 1075 and is named Bowline on the bight and Bowline.