Author Topic: Janus Bowline or an equivalent secure bowline for climbing/rescue purposes  (Read 122440 times)

roo

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Re: Janus Bowline or an equivalent secure bowline for climbing/rescue purposes
« Reply #15 on: December 11, 2008, 06:58:55 PM »
As promised, here is a link to a pdf file which illustrates some bowlines... www.paci.com.au/IGKT/BOWLINES.pdf


Thanks for the images.  I'll just note that the Double Bowline with the repeated finish approaches the rope length usage of the Figure 8 Loop, but on the upside, should be jam resistant.  

The Double Bowline halfway violates your #2 requirement, as it tends to require a little pre-fiddling to form the coils, which can also introduce some possibility for error.

Just thinking aloud.
« Last Edit: February 18, 2011, 09:52:57 PM by roo »
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Dan_Lehman

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Re: Janus Bowline or an equivalent secure bowline for climbing/rescue purposes
« Reply #16 on: December 11, 2008, 11:20:28 PM »
As promised, here is a link to a pdf file which illustrates some bowlines... www.paci.com.au/IGKT/BOWLINES.pdf

I have included a terminology page to ensure that we are all cooking from the same recipe book...any errors/omissions please advise.

Change "loop" to "eye"--"loop" is a much overloaded term, and it can be rid of this job to
a ready, understood non-confusing one.
     [ "EYE SPLICE" is a univerally used term, yes?  (Dutch, German, French folks ... ?!)
             I'm shifting from "loopknot" to "eyeknot", myself. ]
 Now, seeing the Bwl as a marriage of a bight and loop returns the term and
possible confusion, where here "loop" must go vice your (or should we say, Chisholm's)
"hitch"--but this is how many knots books define "loop".
(And you could end up talking more easily of a "double loop" rather than "double hitch",
aka "round turn" (which really sn't so well defined as 720degrees but more like 540).)

Also, for "hitch=>loop" and "bight", the arrow should somehow--by multiplication or different
graphic from arrowhead--point to a broader segment of material (as the bight entails both
the end and one leg of the eye).  "Stem" (a dubious distinction) is shown as an outlined
segment--which, btw, will quickly move out of the nub on serious loading (or the exact bit
of material so delimited will change.

MOST IMPORTANTLY, I REJECT THE DEPICTION AS "FRONT" / "REAR"--that is one damnable
failing of the presentation of the Bowline, and actively works against ready comprehension of it,
as I have well argued above (prior msg. here)!!  I do not care re Bwl what others have done;  I do care
about getting it RIGHT for a change (if that is how to see it--"for a change", i.e.).

Quote
I would particularly appreciate comments/analysis of the #1013 (3 core variant) on page 3.
Why depart from the EBDB, which is pictured previously in this thread?
I see no reason to prefer the variant you show.  You wrote above that you were going to do something
which was tantamount to tying the EBDB (though why you didn't refer to that puzzled me)--to wit:
> I've used #1013 as the starting point and then
>  taken the tail and performed a 360 degree loop around the cross-over of the hitch

which yields precisely the End-Bound Dbl.Bwl.  But now in your pdf, you do NOT go around the
CrossOver Point
, but beside it--omitting the key element of security that the EBDB had
--preventing the SPart-through eye leg from loosening, from jointly w/SPart relaxation loosen
the central, nipping loop of the knot!

Quote
Just to recap my objectives/performance criteria with ... the Bowline ... :
1. Easy to untie - particularly after high loadings
2. Can be tied around an object (eg tree or structural member) without first having to pre-tie a knot (eg re-threaded figure 8 loop)
3. Offers security
4. Is stable in all loading profiles
5. Relatively easy to learn and remember (with correspondingly low error rates with learners)
6. Offers reasonable level of strength relative to same design/model of unknotted rope

These are good criteria--to the point and readily comprehended (#2 might take some example
to make clear:  around a big boulder, e.g.; and possibly the forming of an eyeknot when at
first it wasn't expected (and so, of course, no Fig.8 was pre-tied in anticipation)--a sort of,
impromptu, on-the-fly capability).  I still believe that #6 is overstated:  it comes with such
a nice apparent ranking aspect--i.e. e.g., 75% >  65% --, that it appeals; but it hardly
comes with direct relevance to what is of importance (even at THIS point of immediate testing
--i.e., the slow-pull standard might yield a different result that rapid loading (as per Dave
Merchant's asseritons re Fig.8 & esp. Fig.9 eyeknots vs Overhand)).  At this point, we don't
have testing of any of the 3-dia Bwls; we can look at testing non-differences between
2- & 4-leg (bunny ears) Fig.8 eyeknots, and muse that the extra material will NOT matter;
but we can also cite >one< test report showing breakage in the Fig.8 to come at the collar
but in the Bwl at the loop/"hitch", and muse that since that is where the extra dia. will come
into play, that it might matter, at least a little (and not much separates the two).

Also, "security" has practical significance for both in-tension & out-of-tension states:
testing of Amstel Blue  HMPE half-inch (IIRC) 12-strand rope saw it slip free in a Bwl,
as it did in testing reported by Brion Toss in SAIL mag (2001-09?).  Putting an Overhand
stopper resulted in the knot holding for the former testing (Left Coast forestry interest
in replacing heavy cable for logging), but breaking at about 33% (!!).  YOUR and most
kernmantle-rope concerns are NOT of this sort, but of UNtensioned loosening; and the
testing of this property takes some innovation & insight--my "jiggling" remark, above.
(I think of maybe a washing-machine's vibrations, but really something with a cyclical
back'n'forth of, what, 6 inches (stroke) would be good?!  Flapping from a flagpole line
might be nice, but I'd think that were several eyeknots attached, there might be some
variation in the stimulus given to each; still, if one treats it as I assert with pass/fail
judgement at the end of sufficient duration, the flagpole shaking might suffice.
(It seems that the Bwl loosens most readily if the end points UPwards, and gravity
thus is pulling it out--otherwise, the end will have to be raised:  for rockclimbers,
LEADING, thus the Janus re-tucks have the benefit of pointing the end down.)
(Re "not of [tensioned loading] sort" concern:  Dave Richards did testing of kernmantle
ropes--10.5mm dynamic, 12.7mm low-elongation, & 7mm low-elongation--and did find
tensioned slippage (instead of breakage) for some knots (Sheet Bend, Fisherman's).
--not for Bwl, which was tested.)
cf. www.caves.org/section/vertical/nh/50/knotrope.html
[advisory NB re report:  2 bar graphs 3,4 have swapped indicated data (12.5, 10.5mm);
"bend back" = bight, "turn through" = loop/hitch, re Sheet bend; data listings are right, IMO]


The inclusion of a 2nd diameter of rope through the collar (sorry, but I see this as a section
of the "bight") tends to increase the collar's size ("tends", for in stiff rope that collar might be
wider just from resistance to bending around the 1-dia of SPart), and a larger collar makes
the Bwl more vulnerable to capsizing--where the "hitch"/=>loop goes from a HH-like form to
a round turn form to an opening coil, and nearly straight.  The side-by-side end & SPart will
in my experience tend to orient themselves more, should we say, parallel with bight sides
than compressed against each other--the SPart will press against the bight/collar tip, alone.

Secondly, let me remind you that the Bwl (#1010) is vulnerable to ring-loading--a sort
of "abnormal loading" in some people's terms.  So, starting with the Cowboy Bwl (#1034.5),
you have a base that is resistant to coming untied upon ring-loading (it becomes a Reverse
Sheet Bend so loaded).

I will use your Terminology image to define a "Janus" variation that look good:
1) (magically/mentally) swap legs of the bight--i.e., make this a Cowboy Bwl #1024.5
2) take the new-end --as per (1), the rightmost strand-- leftwards OVER TOP of eye legs;
3) then turn the end around the left leg, and come BEHIND all parts to tuck INTO the
 triangular open small space at the knot's center (where the end, emerging, will run OVER whatever.

These "Janus" variants, as I've defined them, amount to making the same "rabbit-around-tree"
maneuvre a 2nd time, around the tree's *root* so to speak; if one can be expected to do that
once, surely it can be repeated.
AND, frankly, most any such re-tucking even gone slightly awry will still give a more secure
knot and the trio of rope diameters through the nipping loop.  QED.


Quote
I'm going to add photos of the water bowline, Janus & EBDB tomorrow... I'll end up having
 a smorgasbord of photos illustrating high quality photos of all the secured bowlines and its derivatives!

Great.  And do try making the 2nd around-the-tree(root) maeuvre with the Water Bwl,
and see THAT variation; you might then be moved to do so with a Larkshead vs. Clove base,
and achieve "Mirrored Bowlines" variation.  They seem to survive even when amply loose
(in the two nubs, if you will--keeping these two halves close to each other).  Conceivably,
the Water Bwl can be tied in the quick-tie method by simply repeated the loop-forming
maneuvre, but practically I don't find this so easy; better to form the intended base
structure (Cow, pref. to me, or Clove), and make the "rabbit" run.

--dl*
====

agent_smith

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Re: Janus Bowline or an equivalent secure bowline for climbing/rescue purposes
« Reply #17 on: December 12, 2008, 02:40:33 PM »
I have uploaded a new and revised version of the Bowlines pdf file... have tried to incorporate all of Dan Lehman's and others comments.

Grab the file at: www.paci.com.au/IGKT/Bowlines.pdf

I'll leave it up for 2 days.

I hope I have achieved the correct terminology - this is important to ensure that we all interpret information consistently and accurately.

At this point in time, I am at an impasse and don't know which way to proceed.

I need to select a candidate Bowline that is worthy of incorporating into climbing, rescue and industrial roping curricula.

It has to meet the baseline criteria I highlighted previously which are:

1. Easy to untie - particularly after high loadings
2. Can be tied around an object (eg tree or structural member) without first having to pre-tie a knot (eg re-threaded figure 8 loop)
3. Offers security
4. Is stable in all loading profiles
5. Relatively easy to learn and remember (with correspondingly low error rates with learners)
6. Offers reasonable level of strength relative to same design/model of unknotted rope


Help me Obi Wan Lehman!


agent smith
« Last Edit: December 12, 2008, 02:42:55 PM by agent_smith »

Fairlead

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Re: Janus Bowline or an equivalent secure bowline for climbing/rescue purposes
« Reply #18 on: December 12, 2008, 05:36:57 PM »
If I might add just a couple of small things that seem to have been missed =
1.  Tucking the working end of the Yosemite tie off method was, as well as adding security, intended to provide an eye which is clear of obstructions (as it is/was common practice to half hitch the working end around the eye on one side) and the working end taped to the standing part (not shown in the pictures) also has advantages.
2.  Remember 'Ashley' was not referring to modern braided ropes - pinch points and sharp bends (bowline eye in a Karabiner)
affect braided polyamide/polyester/polypropylene/polyethelene in a very different manner to three strand natural fibre ropes. And dont even think about pinching or bending some of the later rope fibres like PBO.

Gordon

roo

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Re: Janus Bowline or an equivalent secure bowline for climbing/rescue purposes
« Reply #19 on: December 12, 2008, 07:56:55 PM »

It has to meet the baseline criteria I highlighted previously which are:

1. Easy to untie - particularly after high loadings
2. Can be tied around an object (eg tree or structural member) without first having to pre-tie a knot (eg re-threaded figure 8 loop)
3. Offers security
4. Is stable in all loading profiles
5. Relatively easy to learn and remember (with correspondingly low error rates with learners)
6. Offers reasonable level of strength relative to same design/model of unknotted rope

Just my opinion based on your requirements above, assuming a standard Bowline is not in the running:

Regarding 1:  All proposals seem acceptable

Regarding 2:  I'd give preference to a Water Bowline or Janus variant for being free of pre-fiddling as I mentioned before.  In almost all situations this will be irrelevant anyway since you have easy end access when tying an end loop.

Regarding 3:  None of the proposals seem completely inadequate and quite frankly I haven't done much testing on some the non-traditional variants.  I think this is one point where you or your organization can work on investigating more thoroughly with various rope types.

Regarding 4:  Closely related to 3.

Regarding 5:  I tend to give a slight edge to the Water Bowline if it is taught properly, but a Double Bowline isn't bad either.  If someone wraps the rope around the wrong leg of an attempted Janus variation, a very bad knot can result.

Regarding 6:  All proposals are going to be adequate.

Overall, I tend to give a slight edge to the Water Bowline based on your requirements.  Of course if one requirement has a much heavier weighing/importance, that could skew the outcome.
« Last Edit: May 29, 2015, 06:36:58 PM by roo »
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Dan_Lehman

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Re: Janus Bowline or an equivalent secure bowline for climbing/rescue purposes
« Reply #20 on: December 12, 2008, 09:02:36 PM »
If I might add just a couple of small things that seem to have been missed =
1.  Tucking the working end of the Yosemite tie off method was, as well as adding security, intended to provide an eye
which is clear of obstructions (as it is/was common practice to half hitch the working end around the eye on one side)
and the working end taped to the standing part (not shown in the pictures) also has advantages.
I have seen various methods to bind the end:  tucking through the lay OR BRAID (have some pics
of this w/8dble-strand CoExOlefins), electrical-taping it, and tucking it back through the SPart
(of which I thought--yet think--I have some photos, but ...).
The common "Yosemite" wrapping requires flexible rope, and puts a Fig.8 in the end side;
a simpler like-tucking where the end passes around the other side of the particular leg
yields and Overhand there, and cannot deform as can the Yosemite way if the end it too
firmly set to an otherwise loose knot (which vulnerability was pointed out by Heinz Prohaska
in reference to the On Rope (1st ed.) Ch.3 "Knots" cover image of such a misformed knot!).

Quote
2.  Remember 'Ashley' was not referring to modern braided ropes - pinch points and sharp bends (bowline eye in a Karabiner)
affect braided polyamide/polyester/polypropylene/polyethelene in a very different manner to three strand natural fibre ropes.
I don't follow this reference:  the sharp bend around a 'biner/krab (of roughly equal diameter to common
climbing-caving-SAR-canyoneering ropes) seems NOT to be the weak point in break tests--i.e., the
break comes in the knot (and in the SPart for the Strangle noose-hitch in one test).  Mariners who
might employ eye splices--where the apex of the eye is fixed (i.e., the rope isn't variously re-spliced
with different positioning, in contrast to re-tying an eyeknot--are advised to broaden this bend
by use of a thimble or prudent choice of what the eye surrounds; but for the eye of a knot,
there is the prior bending of rope in the knot that will be more severe.  I'm of the belief that
friction vs. relative lack of around smooth metal plays a big role in strrength/material-damage.

The revised/expanded pdf has obvious improvements, and of course retains yet the
"front"/"rear" problem in older images.  Good job.  You really should try the main other
version of the "Janus" I described, as it is more *comfortable* in your stiffish kernmantle.
One can further amend that with a roundturn before re-tucking the end.

Also, note the the EBDB's looped end takes some firm hauling snug:  upon loading,
when the nylon cordage lengthens & shrinks, a gap will actually open up between
this securing wrap and the double nipping loops!  --not that that matters all so much,
for security under tension isn't the issue; but it does show that the knot will not be
overtightened by loading:  its tightening that secures it is manually controlled, and
hence the ability to manually untie it after loading (with the careful method previously
described--first bring some slack through the collar, for the prying apart is going to
draw that collar tight atop the SPart!).

Quote
Regarding 2:  I'd give preference to a Water Bowline or Janus variant for being free of pre-fiddling as I mentioned before.

I don't see how the Dbl.Bwl entails ANY "pre-fiddling".  It doesn't accommodate the quick-tie
maneuvre which can be used even for the Water Bwl (though is rather awkward to my
experience there), but it is entirely tied after sizing/placing the eye.

Quote
... haven't done much testing on some the non-traditional variants.
I think this is one point where you or your organization can work on investigating more thoroughly with various rope types.

It's important to recognize that much of the "done" testing is not well investigated to see
how applicable it is to the intended cordage/use domain.  The testing cited above by Dave
Richards does use materials of this particular domain of interest to Agent_Smith, though
even there, if used/older materials are in use in practice, those need to be considered
and not just new cordage.  New will bring flexibility & slickness into test; old will in contrast
tend towards inflexibility and frictiveness, both of which aggravate setting a knot (but which
likely help a knot stay tied).  It's hard to conceive what one should expect of any surprise
in testing the EBDB vs. Dbl.Bwl, except maybe improved strength.  But here there are such
variances in how the knot is set vis-a-vis the collar's tightness (and hence guiding) on the
SPart that the testing would have to explicitly and wisely focus on this point, to be valuable.

--dl*
====

roo

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Re: Janus Bowline or an equivalent secure bowline for climbing/rescue purposes
« Reply #21 on: December 12, 2008, 09:20:59 PM »

I don't see how the Dbl.Bwl entails ANY "pre-fiddling".  It doesn't accommodate the quick-tie
maneuvre which can be used even for the Water Bwl (though is rather awkward to my
experience there), but it is entirely tied after sizing/placing the eye.


As I have mentioned earlier, the Double Bowline only halfway violates one of his requirements, and I don't mean to indicate that it is a deal-breaker, but only that other candidates edge it out.

You may argue that the "fiddling" of producing the coils can be done after placing the rope with mild torsion being introduced into the line.  While this may be, it is harder to do this while keeping hold of the end the rope, thus the partial violation, in my opinion.
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Dan_Lehman

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Re: Janus Bowline or an equivalent secure bowline for climbing/rescue purposes
« Reply #22 on: December 13, 2008, 07:11:45 AM »
I don't see how the Dbl.Bwl entails ANY "pre-fiddling".  It doesn't accommodate the quick-tie
maneuvre which can be used even for the Water Bwl (though is rather awkward to my
experience there), but it is entirely tied after sizing/placing the eye.

As I have mentioned earlier, the Double Bowline only halfway violates one of his requirements,
and I don't mean to indicate that it is a deal-breaker, but only that other candidates edge it out.

You may argue that the "fiddling" of producing the coils can be done after placing the rope with mild torsion being introduced into the line.
While this may be, it is harder to do this while keeping hold of the end the rope, thus the partial violation, in my opinion.

 ???
"With mild torsion being introduced ..." :  what is the issue here?  (At first I was reading "tension". which is different.)
Both structures entail two turns (round turn of 720deg), so both can torque the line;
but I figure that this is seldom an issue, esp. in the context of the OP.

And, contrary my assertion above, the Dbl. Bwl CAN be tied w/a quick-tie method:
one operates on the SPart-side eye leg on for the 2nd turn vice the SPart again in Water Bwl.

--dl*
====]

roo

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Re: Janus Bowline or an equivalent secure bowline for climbing/rescue purposes
« Reply #23 on: December 13, 2008, 07:40:06 PM »

 ???
"With mild torsion being introduced ..." :  what is the issue here?  (At first I was reading "tension". which is different.)
Both structures entail two turns (round turn of 720deg), so both can torque the line;
but I figure that this is seldom an issue, esp. in the context of the OP.

And, contrary my assertion above, the Dbl. Bwl CAN be tied w/a quick-tie method:
one operates on the SPart-side eye leg on for the 2nd turn vice the SPart again in Water Bwl.

If I'm holding the end of the rope with one hand as I form coils for the Double Bowline rather than forming the coils ahead of time, it's mildly annoying to have the rope twist and kink from the coil making. 

I'll just say that I'm not particularly fond of the quick-tie twist method for the Double bowline.  I find I have a tendency to make less than clean and clear coils.
« Last Edit: January 21, 2009, 05:27:50 AM by roo »
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Dan_Lehman

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Re: Janus Bowline or an equivalent secure bowline for climbing/rescue purposes
« Reply #24 on: December 13, 2008, 09:22:30 PM »
"With mild torsion being introduced ..." :  what is the issue here?  (At first I was reading "tension". which is different.)
Both structures entail two turns (round turn of 720deg), so both can torque the line;
but I figure that this is seldom an issue, esp. in the context of the OP.
--dl*
====]

If I'm holding the end of the rope with one hand as I form coils for the Double Bowline rather
than forming the coils ahead of time, it's mildly annoying to have the rope twist and kink from the coil making.
But how is that any different than forming the two turns of a Clove H. for the Water Bwl ?
Depending how this is done, the torsion should be put into the SPart, and often dissipated
w/o much notice--if tying the knot facing the SPart-side, vs. the eye-side.  Otherwise, the
SPart-side eye-leg will be torqued (facing eye); but, again, this is true for either case.
So how can you single out the Dble.Bwl vs. Water Bwl on this ground?

Quote
I'll just say that I'm not particularly fond of the quick-tie twist method for the Double bowline.
I find I have a tendency to make less than clean and clear coils.
The method loses much of its swiftness (in my hands, anyway); but a key benefit
to the method (for single, esp.) is the correct orientation of the end through the loop,
irrespective of speed.

--dl*
====

roo

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Re: Janus Bowline or an equivalent secure bowline for climbing/rescue purposes
« Reply #25 on: December 14, 2008, 01:27:51 AM »
"With mild torsion being introduced ..." :  what is the issue here?  (At first I was reading "tension". which is different.)
Both structures entail two turns (round turn of 720deg), so both can torque the line;
but I figure that this is seldom an issue, esp. in the context of the OP.
--dl*
====]

If I'm holding the end of the rope with one hand as I form coils for the Double Bowline rather
than forming the coils ahead of time, it's mildly annoying to have the rope twist and kink from the coil making.
But how is that any different than forming the two turns of a Clove H. for the Water Bwl ?
Depending how this is done, the torsion should be put into the SPart, and often dissipated
w/o much notice--if tying the knot facing the SPart-side, vs. the eye-side.  Otherwise, the
SPart-side eye-leg will be torqued (facing eye); but, again, this is true for either case.
So how can you single out the Dble.Bwl vs. Water Bwl on this ground?


There may be a couple reasons for the difference.  First, with the Water Bowline, my right hand finger and thumb are actually conducting the end of the rope and can twist it as it's being maneuvered.  With the Double Bowline, I'm just trying to hold the end of the rope while I would focus on manipulating the coils separately.

Second, with the Water Bowline, the second twist manuever is somewhat isolated from the end of the rope by virtue of the first half hitch structure.

Of course, this is a fairly trivial issue.
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TheTreeSpyder

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Re: Janus Bowline or an equivalent secure bowline for climbing/rescue purposes
« Reply #26 on: December 14, 2008, 01:43:44 PM »
i prefer th DBY; but this Round Turn version is best in more flexible lines (rope type being a consideration of choice of what is maximum.  i like tying the Double (or Water) Bowline by the slip knot method, the dble rings give more of a complication to reeving rabbit around and thru, but in slip knot, the mountain comes to our lil'rabbit (Mohammed).  This also works out well in some situations where can make (DBY using slip knot method) half way (as a slip knot), lay aside, hang or just hold on extended thumb, then seal the deal in a hurry when required(by reeving bitter thru to form eye (after it encompasses host/load/implemeant).  It is easy enough for me to tie blindfolded, behind my back, upside down..

The configurations that allow strength (of line) retention are those that ease the deformity of the Standing; even if that is just by giving the same deformity over a longer distance (thus a less sharp/impacting change/deformity).  The Round Turn of the Dble. does that, but not the Water IMLHO.

A krab in the eye divides the load of the system to 2 legs of line (the eye); their equal and opposite is the Standing, that is therefore double the loading of either leg of the eye(as is the parent device/krab)...  So, i think the tendency would be not to break at the eye; except perhaps in some kind of line that the sharpness of that bend over ruled the half loading (per leg of eye compared to krab or Standing).  Rope gets leveraged (as other things) only when they resist on the across/wide axis.  Various rope materials, constructions, diameters and tensions, give that resistance(to sidewards/non inline forces) at different levels, loadings and occasions etc.  Generally, we find rope to be a tension (not compression), inline (not leveraged) device, because mostly it only resists on inline axis of tension.  Force being made up of distance and power; no resistance means all distance, therefore no power...

The 'open' , 'clean' eye of Yosemite type configurations is a good drawing point when loading devices in and out of that eye all day etc.  Furthermore, for better part of or all day or more useability, i might go further and sieze down the bitter of the DBY with electrical tape (bright red or something that doubles as giving more visablity, and perhaps a different color on other eye/end for further easier identification.
« Last Edit: December 14, 2008, 02:01:57 PM by TheTreeSpyder »

Dan_Lehman

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Re: Janus Bowline or an equivalent secure bowline for climbing/rescue purposes
« Reply #27 on: December 14, 2008, 08:19:49 PM »
Quote
I'll just note that the Double Bowline with the repeated finish approaches the rope length usage of the Figure 8 Loop,

Can you quantify this?
Probably not.  But this is the sort of thing that we could collectively come to put into some
detailed quantification.  Heinz Prohaska had done some of this sort of measuring, and I
undertook to do so for a few knots, too, to move beyond "seems ..." to "is roughly <data>";
I employed colored thread woven through at the *ends* of a knot, then untied and measured.
With a few folks taking such measurements over some misc. varieties of rope, we can build
useful reference data.  (I'd say that manual setting would be the knot-state to use.)  There is
some further consideration to be given beyond the pure consumption of material IN the knot
--how much is needed in order to tie  the knot (some knots might need a more than
others, for formation):  this quantity, however, seems much harder to define & measure.
And, for practical purposes, sizing for some applications will need to include a certain
amount of tail, for safety assurances (often more peace of mind than actual knot need).
((Now, to try to find that old back-of-pale-yellow-envelope (IIRC) list of measurements ... !))


i prefer th DBY; but this Round Turn version is best in more flexible lines\
?!  Rather, the YoBowl (or Dbl.Bwl w/YoTOff) is what really needs flexibility, as its finishing
tuck comes from a wrap of the end around a single diameter of rope.  (This is an aspect not present
if the end is wrapped in the opposite direction, putting an Overhand vs. Fig.8 into itself.)

Quote
The configurations that allow strength (of line) retention are those that ease the deformity of the Standing;
even if that is just by giving the same deformity over a longer distance (thus a less sharp/impacting change/deformity).
The Round Turn of the Dble. does that, but not the Water IMLHO.
Absent testing, this is just speculation.  I think that there might be an element of friction to be
found in variations on what the SPart bends around, in the following sense:  for the common Bwl,
the SPart first draws against the end, and pulls it towards the collar and then a bit to one side;
it then turns around the end-side eye-leg.  In the first case, I think that varied loading will see
movement that shifts the position of the end, as the end comes w/draw of SPart; whereas in
the latter point the eye-leg holds its ground and will feel the SPart draw around it, frictionally.
So, there might be some (probably slight) observable difference over the suffering of several
sudden loadings between some knots & versions of knots given such differences in how the
movement of the heavily loaded strand affects others it contacts--if they can move with it,
then there will be less damage.  Note that this is a result that will NOT show up in slow-pull testing,
yet it could well be more practically significant (for a tow line, e.g., taking varied loading for hours).


Quote
The 'open' , 'clean' eye of Yosemite type configurations is a good drawing point when loading devices in and out of that eye all day etc.
If those devices can take it, the rope would prefer to be cast into twin eyes, to share the load.
However, the added *width* of twin eyes will increase strain on something like a 'biner/krab,
putting load onto a more leveraged point.

Btw, a simple enhancement to the Common Bwl is to reeve into it a 2nd eye, for tying-in for rockclimbing.
Even if the end slips out of the final tuck through the loop of such a twin-eye knot, one still has
two eyes w/some effect, and the base/initial Bwl is intact, with a pretty obvious dangling free end.
A lead climber's Bwl will be oriented eye-upwards, and gravity might help pull the end out,
in contrast to a 2nd or top-rope climber, where the belay line runs upwards to a top anchor or belayer,
and gravity will be pulling the end into place more.  For the lead climber, should the end come out
of final tuck, it should hang long & w/gravity-assist against pulling out of the penultimate tuck
(and still run back through the harness and then to the initial two tucks making a Bwl #1010).
Sadly, in true bonehead fashion, as the only twin-eye bowline climbers can bring to mind,
the 2nd eye is typically finished as though "re-weaving/-threading" a Bowline on a Bight,
rather than simply making a 2nd collar--and gaining 2 diameters of material through the loop!.
Moreover, the 2nd rabbit-out-of-hole-&-around-tree collaring can be dressed & set between
the central nipping, loop and the initial collar, and so thereby inhibit the loosening of the collar
with the end!  Please don't get "hung up"/enthralled by the potential of completely "re-threading"
the Bowline--it's not a great result; it's much better as just described, added a 2nd collar with
the redundant/twin eye.

--dl*
====

agent_smith

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Re: Janus Bowline or an equivalent secure bowline for climbing/rescue purposes
« Reply #28 on: December 15, 2008, 03:02:20 PM »
Have been hard at work and have uploaded another new and revised version of the Bowlines pdf file...

Grab the file at: www.paci.com.au/IGKT/Bowlines.pdf

Once again, it will only be available for a short period.

Having tied and played with all of the variations illustrated, I am leaning towards the last image - the 720 degree variant. Why? Because:
[ ] It has 3 rope diameters which are encircled and gripped by the loops
[ ] It It has double loops acting to encircle and grip the bight
[ ] The collar describes a larger radius
[ ] The tail parallels the Spart leaving the eye clear
[ ] It is simply an extension of ABoK 1013 and improves upon it (in my view)
[ ] The structure exhibits a degree of symmetry and compactness and also appears to be secure and stable

I would of course welcome opinions/feedback...


agent smith

roo

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Re: Janus Bowline or an equivalent secure bowline for climbing/rescue purposes
« Reply #29 on: December 15, 2008, 06:05:00 PM »
Having tied and played with all of the variations illustrated, I am leaning towards the last image - the 720 degree variant. Why? Because:
[ ] It has 3 rope diameters which are encircled and gripped by the loops
[ ] It It has double loops acting to encircle and grip the bight
[ ] The collar describes a larger radius
[ ] The tail parallels the Spart leaving the eye clear
[ ] It is simply an extension of ABoK 1013 and improves upon it (in my view)
[ ] The structure exhibits a degree of symmetry and compactness and also appears to be secure and stable


That's nice, but be aware that you now have a loop that actually consumes more rope than the bulky old Figure Eight Loop.  This may also have implications for how easy or hard it is to adjust loop size, position or excess.

Secondly, I'd be more concerned with what you think "3 rope diameters which are encircled and gripped by the loops" and other simliar appearance-related attributes actually achieves, rather than striving toward appearance.  If you find a loop that is more secure, even if it doesn't look like it "should" be, it should obviously score higher in the security arena.  Don't judge a book by its cover or a knot by its topography.






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