Author Topic: Compact loop on a bight!?  (Read 14108 times)

JustKnot

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Compact loop on a bight!?
« on: September 18, 2006, 09:38:14 PM »
This loop tied itself when I was braiding lanyard...
Looks quiet compact compared to alpine butterfly or overhand loop.
Does it has a name?


Its a pity that complex woven knots can not tie themselves accidently :D

KnotNow!

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Re: Compact loop on a bight!?
« Reply #1 on: September 19, 2006, 10:08:32 AM »
Hi, I need more photo or loose photo.... I can't see what you have.  Blind and dumb.
ROY S. CHAPMAN, IGKT-PAB BOARD.

JustKnot

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Re: Compact loop on a bight!?
« Reply #2 on: September 19, 2006, 07:28:31 PM »
Sorry for the jumbo size pics... resized them a bit...
And here is the photo of the loose knot:


Mike

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Re: Compact loop on a bight!?
« Reply #3 on: September 20, 2006, 02:57:41 AM »
Thats a constrictor knot with one loop pulled through the other. At least thats what mine spilled into when I tried it.
« Last Edit: September 20, 2006, 03:05:06 AM by Mike »

KnotNow!

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Re: Compact loop on a bight!?
« Reply #4 on: September 21, 2006, 04:59:20 AM »
Hi All,
  The constrictor can be a binding knot, a mid span loop with a good lead in both directions or an end loop, with only one lead.  It is sad that it requires some care to hit the loops after the binding knot has been formed, but once the deformation is solid the good old binder becomes a fine loop or a fine end loop.  It is all in ABOK so we have not to reinvent the wheel.  Sorry, my ISP is kicking me off or I'd post the ABOK reference to end loop and mid loop and the Knot New reference to my one hand constrictor (to use as such or colapse to mid loop or end loop). I really enjoy the www but my ISP... not my best friend.
ROY S. CHAPMAN, IGKT-PAB BOARD.

DerekSmith

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Re: Compact loop on a bight!?
« Reply #5 on: September 25, 2006, 05:34:40 PM »
JK,

Thank you for introducing me to this neat little in-line loop.

I use the constrictor regularly, so tying it is automatic whenever I need an extra hand to grip something.  Being able to so easily fold the constrictor into an in-line loop is a great bonus.

Generally, for an in-line loop, I would prefer the Alpine with its symmetry and strength coming from the lines taking a lazy 240 degree turn around a 3 diameter core.  However, the constrictor loop has an advantage in that it is easily adjustable before it is set.

you will see that in this image, the red leg can be slipped to adjust the size of the loop.

To set the loop, the top RHS white loop must be crossed over the red loop as shown here

then tighten to lock the knot.

A second advantage of this little in-line loop is that it is very easy to untie, much easier than the Alpine.  Simply bending the gripping constrictor loop down the back of the large formed loop, unfolds the knot.  As soon as the formed loop has been drawn back through the gripping loop the whole knot falls apart.

There does however appear to be one drawback to this otherwise almost ideal little in-line loopknot - and that is its strength.  One of the lines (in this case the red line) takes a tight 270 degree turn around a single diameter core, coupled with a gooseneck strangle as it enters the turn.  This has to go on my list of to-do's to find out how that particular element of the knot performs but it cannot be good.

Altogether though, this little knot will certainly become part of my list of frequently used knots - it is just so easy and so handy.

Thanks
Derek
« Last Edit: September 27, 2006, 07:50:46 AM by DerekSmith »

knudeNoggin

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Re: Compact loop on a bight!?
« Reply #6 on: September 26, 2006, 06:00:46 PM »
Generally, for an in-line loop, I would prefer the Alpine with its symmetry and strength coming
from the lines taking a lazy 240 degree turn around a 3 diameter core. 
The Butterfly is asymmetric.  (A similar but symmetric knot is Ashley's #1408,
which cannot be tied in the bight.)  As for strength, on this forum some time ago
Paul Kruse reported testing this knot and the bowline and finding this quite weak.
Being asymmetric, one can wonder what exactly was tested.  There is also a
question of dressing the butterfly.  Many times the knot is shown in a form with
pretty sharp, 1 diameter bends around the legs of the eye.

Quote
A second advantage of this little in-line loop is that it is very easy to untie,
much easier than the Alpine.  Simply bending the gripping constrictor loop down
the back of the large formed loop, unfolds the knot.
As I reach for a marlinespike to untie one quite jammed such knot, I can only
assume that you are working with much less material & force!  This knot has
Reef-like aspect of on the one hand being able (so it seems) to slip a little in
coming tight, and to jam.  (body weight on 5/16 inch firm lay combination rope)


Quote
One of the lines (in this case the red line) takes a viscous 270 degree turn around a single diameter core, ...
Much the same as for a Blood knot, which tests favorably in some materials.
(Barnes found the Blood to break where loaded parts passed on either side of
the tucked ends, center of knot, not at the end where this tight bend occurs,
in nylon monofilament line & gut.)  But the Blood knot has much tightened
bearing on the main loaded part before the sharp bend.

The knot in question has been presented as "The Algonquin Bowline" in e.g.
The Knot Book by G. Budworth, but I do not see it in later of his books,
or in some others.  In Ashley, it is #1045 (see figure-8 like loopknot #1043, too),
but is not shown for use mid-line.  I do not like its functioning mid-line.

*knudeNoggin*

DerekSmith

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Re: Compact loop on a bight!?
« Reply #7 on: September 26, 2006, 11:59:16 PM »
Generally, for an in-line loop, I would prefer the Alpine with its symmetry and strength coming
from the lines taking a lazy 240 degree turn around a 3 diameter core.
The Butterfly is asymmetric.  (A similar but symmetric knot is Ashley's #1408,
which cannot be tied in the bight.)  As for strength, on this forum some time ago
Paul Kruse reported testing this knot and the bowline and finding this quite weak.
Being asymmetric, one can wonder what exactly was tested.  There is also a
question of dressing the butterfly.  Many times the knot is shown in a form with
pretty sharp, 1 diameter bends around the legs of the eye.

You know, I have a real problem thinking of the Alpine as asymmetric.  But then, symmetric is one of those words like 'unique' and 'pregnant', you can't be nearly unique or nearly pregnant or nearly symmetric.  In the mathematics or physics sense something is only symmetrical if it remains unaltered when rotated or reflected about its planes.  Clearly, in these terms, the Alpine cannot be symmetric because the loop pokes out only on one side, so if you flip it over 180 degrees it looks totally different, also the front looks different to the back, and the two lines do not go into the knot exactly matching, because one has to go in on top of the other.

So if your assertion that the Alpine is asymetric is based on the purist view, then I understand and accept your correction.

However, I used the word 'symmetry' which also has the dictionary definition of "Beauty as a result of balance or harmonious arrangement" and for me the Alpine has this aspect of symmetry.

As for strength, I would quite like to read Paul Kruses analysis to which you refer but cannot find it via the search function.  Could you give a link to his post please.
« Last Edit: September 27, 2006, 07:45:09 AM by DerekSmith »

DerekSmith

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Re: Compact loop on a bight!?
« Reply #8 on: September 27, 2006, 12:24:03 AM »
Quote
Quote
A second advantage of this little in-line loop is that it is very easy to untie,
much easier than the Alpine.  Simply bending the gripping constrictor loop down
the back of the large formed loop, unfolds the knot.
As I reach for a marlinespike to untie one quite jammed such knot, I can only
assume that you are working with much less material & force!  This knot has
Reef-like aspect of on the one hand being able (so it seems) to slip a little in
coming tight, and to jam.  (body weight on 5/16 inch firm lay combination rope)

I have just tied it in 5mm PP braid and applied my body weight to it (190lb), then untied it with my thumbnail by rolling the gripping loop over the formed loop.  I tied it in good old 'hairy string' and loaded it til it broke.  It was hard to distinguish where the gripping loop was, but once identified, it was rolled forward with only thumbnail pressure.  However, I tied it in 500# Spectra and stood on it !  It took me a good 10 minutes to find the gripping loop before I could even begin to pick it open.  I have no doubt that there will be many materials which would prove impossible to untie once heavily loaded, but the rolling gripping loop makes it achievable vs many knots which prove impossible to open even having reached for the marlin spike.
« Last Edit: September 27, 2006, 07:46:25 AM by DerekSmith »

DerekSmith

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Re: Compact loop on a bight!?
« Reply #9 on: September 27, 2006, 09:22:22 AM »
One of the lines (in this case the red line) takes a tight 270 degree turn around a single diameter core, ...
Much the same as for a Blood knot, which tests favorably in some materials.
(Barnes found the Blood to break where loaded parts passed on either side of
the tucked ends, center of knot, not at the end where this tight bend occurs,
in nylon monofilament line & gut.)  But the Blood knot has much tightened
bearing on the main loaded part before the sharp bend.


Here I must disagree.  I feel that the comparison you make with the one diameter turns in the Blood knot, and the strength of the Blood knot, is inappropriate for a number of reasons.

In the Blood knot each loaded line enters and passes through the wrap section, then the first deviation from straight is a 90 degree turn around two diameters (its own end and the opposing parts end) before starting the series of one diameter turns which I assume you are making the comparison with.  The fact that the cord has already had an opportunity to shed load over a two dia. turn makes the Blood knot stronger than the knot in question in which the line goes straight into the 270 degree one dia. turn without any prior opportunity to shed load.

However, the greatest disparity in this comparison is the fact that the Blood Knot is structured so as to allow the loaded part to shed a great part of its load into its opposing parts coil while still in a straight line configuration.  In fact it can be shown that a pair of Gripping hitches tied back to back (which is what the Blood Knot is) shed 50% of the load while the cord is in a straight configuration into the grip of the opposing parts coils.  Providing of course that the cord in use is not subject to compression failure, the Blood Knot will be significantly stronger because it uses a totally different construction to transfer load before the tight one dia. sections.

Footnote:-
You can test the 50% load shedding ability of these paired gripping hitches for yourself.  Tie two gripping hitches back to back but leave ca 3" of cord between the two knots.  Load them and then test the tension in each of the two cords running between the two hitches by forcing them apart with a 1" spacer.  Provided you made the knot and dressed it symetrically(?), then you will find that roughly half of the load is carried in each cord (demonstrated by the angles subtended in the cords at the displacement point), showing that half the load had to have been transferred while the cords were straight and within the gripping coils of its opposing parts hitch.

knudeNoggin

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Re: Compact loop on a bight!?
« Reply #10 on: September 27, 2006, 04:46:04 PM »
The Butterfly is asymmetric.  (A similar but symmetric knot is Ashley's #1408,
which cannot be tied in the bight.)

You know, I have a real problem thinking of the Alpine as asymmetric. ... Clearly, in these terms, the Alpine cannot be symmetric
because the loop pokes out only on one side, so if you flip it over 180 degrees it looks totally different, also the front looks different
to the back, and the two lines do not go into the knot exactly matching, because one has to go in on top of the other.
Your last point is the one that makes the knot asymmetric--the course of the path of one end
into the knot differs from the other.  Clearly it's not because the eye is on one side, as
that's true of #1408 and others which are symmetric (rotated on an axis perpendicular
to the line of tension in an unloaded eye).

Quote
In the Blood knot each loaded line enters and passes through the wrap section, then the first deviation from straight
is a 90 degree turn around two diameters (its own end and the opposing parts end) before starting the series of one diameter turns ...
I don't see this:  each "SPart" enters and runs straight until making some pretty slight curve in passing
(on the opposite side from the opposed such SPart) over the ends where they exit; then these SParts
make the sharp, single diameter turn in turning perpendicular to the line of tension and wrapping TWO
diameters (the two parallel SParts) on their way to be tucked out as ends.  The one side of the knot
in question (#1045) has such a sharp turn but with just minor interference preceding it.

As for untying it, we weren't clear on how we loaded it (!!) :  I loaded it as a mid-line loopknot w/o
attachment to the eye (as opposed to loading it as a loopknot, which would load the eye).   One
might want to think of this #1045 as only a kind of "directional" loopknot, which is intended to be
loaded in the eye in only one direction (whereas the Butterfly knot can be loaded in either direction,
although there should be some differences following from its asymmetry).  Still, knots like #1045
will tend to jam in rope (such as Perfection loop).  You have chosen some slick rope, though in
the case of the Spectra line even that didn't help so much--but there your load was quite high
in terms of tensile strength?!

As for opposing friction hitches, there is some risk that one will grip in advance of the other,
and that imbalance be increased with tension, the gripping hitch further tightening and thus
preventing the opposed tension getting to the opposed hitch to tighten it.

*knudeNoggin*

DerekSmith

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Re: Compact loop on a bight!?
« Reply #11 on: September 27, 2006, 09:54:24 PM »
The Butterfly is asymmetric.  (A similar but symmetric knot is Ashley's #1408,
which cannot be tied in the bight.)

You know, I have a real problem thinking of the Alpine as asymmetric. ... Clearly, in these terms, the Alpine cannot be symmetric
because the loop pokes out only on one side, so if you flip it over 180 degrees it looks totally different, also the front looks different
to the back, and the two lines do not go into the knot exactly matching, because one has to go in on top of the other.
Your last point is the one that makes the knot asymmetric--the course of the path of one end
into the knot differs from the other.  Clearly it's not because the eye is on one side, as
that's true of #1408 and others which are symmetric (rotated on an axis perpendicular
to the line of tension in an unloaded eye).


So, it was the purist standpoint you were taking.  However in allowing that #1408 is symmetric, you are allowing for degrees of symmetry.  #1408 is symmetric only about one axis.  Other knots such as the carrick have a greater symmetry as they are symmetric about two axis while at the other end of the spectum you have the Alpine which has symmetry only in the esthetic plane.

By the way, I would guess that many of the board members do not have access to the Ashley Book of Knots, and therefore have no idea what #1408 is or looks like.  Do you know of any web resource which shows the #1408 and tying methods?


DerekSmith

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Re: Compact loop on a bight!?
« Reply #12 on: September 27, 2006, 10:04:50 PM »
As for untying it, we weren't clear on how we loaded it (!!) :  I loaded it as a mid-line loopknot w/o
attachment to the eye (as opposed to loading it as a loopknot, which would load the eye).   One
might want to think of this #1045 as only a kind of "directional" loopknot, which is intended to be
loaded in the eye in only one direction (whereas the Butterfly knot can be loaded in either direction,
although there should be some differences following from its asymmetry).  Still, knots like #1045
will tend to jam in rope (such as Perfection loop).  You have chosen some slick rope, though in
the case of the Spectra line even that didn't help so much--but there your load was quite high
in terms of tensile strength?!

*knudeNoggin*

Agreed.  I likewise only loaded the main line with the loop hanging free.  At this point I have no idea of its performance when the loop is under load, either inline, or tangentially.  An important point when the purpose of the knot is to give a midline attachment.  There are so many variants to such an experiment, one wonders where to begin.  I will give it some thought.

What logic do you follow to yeild the arguement that this knot should be used directionally?

Derek

DerekSmith

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Re: Compact loop on a bight!?
« Reply #13 on: September 27, 2006, 10:20:10 PM »
As for opposing friction hitches, there is some risk that one will grip in advance of the other,
and that imbalance be increased with tension, the gripping hitch further tightening and thus
preventing the opposed tension getting to the opposed hitch to tighten it.

*knudeNoggin*

Agreed.  However, my reference to a pair of back to back friction hitches was to demonstrate that you could use such a system to show that in a balanced pair, the loading on the spart was shed 50% before the linear spart started placing any load on its turns.

The Bloodknot does not seem to have a mechanism that would allow an imbalance to be established and this is almost certainly why it is so strong in certain situations.  The strength is not due to its 1 diameter turns and the implied inference that the Blood knot has 1 diameter turns and is strong, so 1 diameter turns alone do not implicate weakness, is faulty.

Are you, through your use of the reference ot the strong Bloodknot, suggesting that readers should start to consider the 1 diameter turn as strong?

DerekSmith

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Re: Compact loop on a bight!?
« Reply #14 on: September 27, 2006, 10:29:01 PM »

Quote
In the Blood knot each loaded line enters and passes through the wrap section, then the first deviation from straight
is a 90 degree turn around two diameters (its own end and the opposing parts end) before starting the series of one diameter turns ...
I don't see this:  each "SPart" enters and runs straight until making some pretty slight curve in passing
(on the opposite side from the opposed such SPart) over the ends where they exit; then these SParts
make the sharp, single diameter turn in turning perpendicular to the line of tension and wrapping TWO
diameters (the two parallel SParts)
on their way to be tucked out as ends.  The one side of the knot
in question (#1045) has such a sharp turn but with just minor interference preceding it.
*knudeNoggin*

I have a feeling that we both agree with one another here, although in the version of the Blood knot I  tie, the wraps are only around the opposite SPart i.e. a single diameter.  But then, that was the point you were making by refereing to the Blood knot in the first place - I think?

Derek