Author Topic: Help with naming a Bowline variant  (Read 10891 times)

Pete K

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Help with naming a Bowline variant
« on: February 05, 2013, 07:26:15 PM »
Greetings, my search for the identity of a knot has led me to find this website and I'd like to fish in the pool of knowledge here if I may.
Some quick background. I am a caver and have been involved with some testing of various double loop knots recently. One of the most commonly used knots in caving is the Bowline on the Bight, its two loops making equalised rigging from a pair of bolts easy.
We have been using a version of the Bowline on the Bight for some testing and have called it the Double Bowline on the Bight as it seems to follow the standard convention of naming that the Bowline and Double Bowline follow.
It has been brought to my attention that a Double Bowline on the Bight already exists, a 4 loop version similar to a Double French Bowline.
I think that the knot we are using should be called the Double Bowline on the Bight but I'd like to see if it has a correct name.

Here is a link to the tying method for our DBotB: http://www.peakinstruction.com/blog/knots/how-to-tie-a-double-bowline-on-the-bight/
And for anyone who is interested the context of the enquiry: http://www.peakinstruction.com/blog/ & http://ukcaving.com/board/index.php?topic=14602.0
Thanks for looking and your help is appreciated.

roo

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Re: Help with naming a Bowline variant
« Reply #1 on: February 05, 2013, 07:57:54 PM »
Some quick background. I am a caver and have been involved with some testing of various double loop knots recently. One of the most commonly used knots in caving is the Bowline on the Bight, its two loops making equalised rigging from a pair of bolts easy.
A bit of a detour:  I'm hesitant to go down this path.  Double loops tend to use an huge amount of line (especially in this case), don't get much testing, and due to their complexity they often tend to have hidden vulnerabilities.

A cleaner, more reliable route would be using a separate line for your two anchors and in the middle of this line a clove hitch can be made over a carabiner to equalize as needed.  A Pile Hitch may be used as a more jam resistant alternative to the Clove.

All other connections can be made with standard, tested, secure hitches or loops:
http://notableknotindex.webs.com/gnathitch.html
http://notableknotindex.webs.com/waterbowline.html
http://notableknotindex.webs.com/zeppelinloop.html
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Pete K

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Re: Help with naming a Bowline variant
« Reply #2 on: February 05, 2013, 08:08:22 PM »
The pool of knots we use are well tested. I had this one on a drop test rig last week.
Cave rigging tends to follow a line of anchors (traverse) along to a pair of bolts at a pitch head which we call a y-hang. The rigging would follow the bolts from the start of the line to the y-hang and on down the pitch giving an abseil line. The use of multiple strands of rope of this would introduce too many weaknesses. There are dozens of ways for me to rig traverse lines and pitch heads but the Bowline on the Bight is the most appropriate knot for its simplicity, ease of tying and adjustment and shock absorbing ability when a bolt fails. The Double Bowline on the Bight has shown to be better as absorbing shock loads over and over again.
Thanks for the ideas but I'm really only looking to see if this 'DBotB' has a true name.

roo

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Re: Help with naming a Bowline variant
« Reply #3 on: February 05, 2013, 08:26:52 PM »
The use [an extra short piece of rope] on this would introduce too many weaknesses.
Why?  Don't you know how to size rope?
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Pete K

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Re: Help with naming a Bowline variant
« Reply #4 on: February 05, 2013, 08:38:34 PM »
What do you mean by size the rope? I'm not following your explanation sorry, long day.
I'm probably not explaining myself well. The continuous path of the rope, without break or the introduction of extra components, is integral to the safety chain of the system. The exception being using karabiners to attach the rope to the bolts in the rock.

roo

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Re: Help with naming a Bowline variant
« Reply #5 on: February 05, 2013, 08:41:54 PM »
The exception being using karabiners to attach the rope to the bolts in the rock.
My point exactly.  You already use separate components without worry, because they meet load rating requirements. 

P.S.  In your testing, I hope you remember to test all combinations of load paths.
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Pete K

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Re: Help with naming a Bowline variant
« Reply #6 on: February 05, 2013, 08:51:40 PM »
Ahh, I'm with you now hopefully. The karabiners or maillons are stronger than the 9mm semi-static rope that we generally use so no worries there. It is also much faster to use them instead of rethreading the rope through the bolts, something I can do but is very slow and not very user friendly.
The testing is a comparative set of tests not designed to give a statistical certainty but an indication of mentionable differences in performance, which it did. The variables do not matter here, there will be little difference in real world usage.

Dan_Lehman

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Re: Help with naming a Bowline variant
« Reply #7 on: February 06, 2013, 08:58:46 PM »
I am a caver and have been involved with some testing of various double loop knots recently.

Hi, Pete, thanks for your query & presentation.

Why have you been testing double-eye knots recently?
--i.e., what of the de rigeur ones used for caving has moved
you to look further?

And what sort of testing are you doing.  You mention making
a drop test (so, strength in dynamic, worst-case loading);
were there other sorts of tests?

(Okay, wrote the above prior to browsing the lonnnng
thread on UKCaving.  Still, a summary might help, here.)

Quote
One of the most commonly used knots in caving is the Bowline on the Bight, its two loops making equalised rigging from a pair of bolts easy.
My concern with some various double-eye bowlines is that
if the eye that leads directly to the loaded end is not itself
loaded --say, if its bolt fails--, the unloaded eye can collapse,
which entails perhaps too much frictional heat/abrasion,
and an extra dynamic of additional extension.  (This could
be prevented by joining the two ends of the dbl.-eye knot
into a single-eye knot such as the bowline --maybe
tucking the tail through the dbl.-eye knot for security.)


Quote
It has been brought to my attention that a Double Bowline on the Bight already exists,
a 4-[eye] version similar to a Double French Bowline.
I think that the knot we are using should be called the Double Bowline on the Bight but I'd like to see if it has a correct name.
Is there a citation for who calls this other knot that,
where?  --can't say that the moniker has surfaced
to my awareness (and I see one caving forum from
time to time).

Quote
And for anyone who is interested the context of the enquiry: http://www.peakinstruction.com/blog/ & http://ukcaving.com/board/index.php?topic=14602.0
Thanks for looking and your help is appreciated.

Ahhhh, good to have some knots reading (though again
and again one sees the same confusions ...), thanks!

Quote
The karabiners or maillons are stronger than ...
And take to the contact with the bolt hangers much
more kindly than will rope!


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Pete K

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Re: Help with naming a Bowline variant
« Reply #8 on: February 06, 2013, 09:14:42 PM »
Thanks for taking the time to reply, sadly I dont have any myself for a proper response.

I coined the name for our Bowline varient, the name Double Bowline on the Bight fitted with the Bowline/Double Bowline naming convention I had observed already.

It has been shown to me that a knot with that (ABoK#1083) name exists here:
http://www.morethanknots.com/bowline/bowline_list.html
Picture on the left here:
http://www.morethanknots.com/bowline_pics/Bowline_006.jpg

We came to using and testing this knot because the French Caving School advised against the use of the knot we would normally use in this position (Bowline on the Bight). We have done some 'scratch the surface' type testing to show comparativew strengths between the other well known appropriate double loop knots. More will need to be done but we have an indication of the Double Bowline on the Bight's suitability.

All I have time for now. Thanks again.

Dan_Lehman

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Re: Help with naming a Bowline variant
« Reply #9 on: February 06, 2013, 10:13:09 PM »
re the name

Forget worrying about the name : what you did, as you
note, followed a reasonable nomenclature rule
--which is more than one can say for Ashley!  (There
are plenty of contradictions in ABOK.)
("bight" itself is an adventure.)

Btw, I think you'd be a bit better with using the
"water bowline" for a solution --doing the usual
BotB *backflip* of the twin-eyes bight to finish--
as the 2nd turn I think will give a better lock than
in the dbl.bwl structure.  (The water bowline
has a clove hitch base, so to speak, into which
the eyes bight would be reeved.)


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alpineer

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Re: Help with naming a Bowline variant
« Reply #10 on: February 06, 2013, 10:53:35 PM »

Picture on the left here:
http://www.morethanknots.com/bowline_pics/Bowline_006.jpg
 

Hi Pete K,
Your naming convention has good merit and I would continue using it.
The knot in the photo is a Double Bowline On The Bight having the nipping loop closest to the collar simply pulled open to form the two extra loops.

Pete K

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Re: Help with naming a Bowline variant
« Reply #11 on: February 06, 2013, 11:21:28 PM »
Thanks for that. I'm playing with Water Bowlines now. A little harder to tie than the dbl.bwl and botb but I will do some experimenting. They may provide another option for caving use.

alpineer

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Re: Help with naming a Bowline variant
« Reply #12 on: February 07, 2013, 01:05:06 AM »
Hi again Pete,

I have another option for you which is but a simple variation of the DBoB's nipping structure and tying procedure. I'll explain how to make the nipping structure in terms of it's Double Bowline single loop counterpart...

Stack two loops, each of opposite handedness, and such that the Standing Part is sandwiched between the coils of the two loops. That's it. This is the most efficient nipping structure that I've come across for the Bowline and renders it very secure and very stable. 
« Last Edit: February 07, 2013, 01:57:47 AM by alpineer »

Dan_Lehman

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Re: Help with naming a Bowline variant
« Reply #13 on: February 07, 2013, 06:06:59 AM »
We came to using and testing this knot because the French Caving School
advised against the use of the knot we would normally use in this position
(Bowline on the Bight).
Tell me : is it customary (or even not advised against)
to ring-load a knot, as is what the French video
shows being the failure mode?
(For those not seeing the French video, they show the
bowline on a bight with eyes splayed near and far
(to the viewer), AND the short tail tied at a seemingly
perpendicular-to-axis-of-loading angle (eyes are apart
at, what, the fairly extreme angle of 140degrees (!!?)
upwards; THEN one eye is clipped into with a 100kg
weighted runner (!), and ... w h o o o oooossshhHH ...
the entire long, hanging SPart is sucked up through
& out the knot as the weight "decks" !!)

Now, my first thought was "huh, how is that rigging
reasonable (the tying off of the tail, especially), and
then "WHOA, who ring-loads an eye??"!  ???


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alpineer

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Re: Help with naming a Bowline variant
« Reply #14 on: February 07, 2013, 08:56:20 AM »
http://ukcaving.com/board/index.php?topic=14580.0

The Fusion Knot http://fr.wikipedia.org/wiki/N%C5%93ud_de_fusion and the Karash Double Loop http://www.karashknot.com/ are one and the same. How's that for confusion?
« Last Edit: February 07, 2013, 09:00:52 AM by alpineer »