Author Topic: Bowline Cinch  (Read 14557 times)

davidmiles

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Bowline Cinch
« on: March 04, 2011, 11:19:34 AM »
Here is a not I developed for climbing and mountain rescue.
I would appreciate any feedback.

http://www.milesgear.com/BowlineCinch/BowlineCinch.html

Thanks,
Dave

Mike in MD

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Re: Bowline Cinch
« Reply #1 on: March 04, 2011, 03:27:24 PM »
Dave,

I'm another newbie.  Your post is the first time I have seen a Yosemite bowline.  I think I'll use this in place of my regular bowline. 

Thanks,
Mike

SS369

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Re: Bowline Cinch
« Reply #2 on: March 04, 2011, 03:57:23 PM »
Hello David and welcome to the forum.

I've tied this just a few moments ago in small accessory cord (3mm) and while I think it is neat and ingenious, I am wondering about the necessity of it and what are characteristics make this better than let's say the Y-Bowline and just thread through the open loop instead of threading through the nipping areas?
The captured rope seems to be under more abrasive stresses and possibly weaken the knot(?) when more advanced angles are encountered.
Aside from the leg of the sling being captured I am unsure of the need of tying complexity. (Not all that complex, but more so than just passing the end through the loop.)

I'd love to know more about the tests you ran and where the examples failed.

Thank you for sharing this.

SS

davidmiles

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Re: Bowline Cinch
« Reply #3 on: March 04, 2011, 04:54:33 PM »
Mike,

The Yosemite bowline is very nice since the end is tucked neatly and secure.  It is used in climbing to secure the climbing rope directly to the harness.  Very compact and secure.  A substitute for the figure 8 follow-though.

SS,

I'm not sure I follow your comment.  The whole idea of this is to form a loop of rope where the end is captured.  Is the end captured after you thread it through the Y-bowline?  Do you have a picture?  You can tie this loop at home and not have to re-tie on the rock.  We do this with prusik loops and webbing runners.

The testing was a pull of 1 sample on a Instron.  Broke on one of the tightest nips in the bowline.

Thanks,
Dave

roo

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Re: Bowline Cinch
« Reply #4 on: March 04, 2011, 05:21:08 PM »
Mike,

The Yosemite bowline is very nice since the end is tucked neatly and secure.  It is used in climbing to secure the climbing rope directly to the harness.  Very compact and secure.  A substitute for the figure 8 follow-though.

I've been disappointed by the security of the Yosemite add-on.  There are more secure bowline variations, such as the intuitive Water Bowline, and the less intuitive Janus variation, although the Janus variation has some possible evil impostor issues if the wrong leg gets the extra wrap.
« Last Edit: May 29, 2015, 07:23:20 PM by roo »
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roo

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Re: Bowline Cinch
« Reply #5 on: March 04, 2011, 05:23:36 PM »
Here is a knot I developed for climbing and mountain rescue.
I would appreciate any feedback.

http://www.milesgear.com/BowlineCinch/BowlineCinch.html

Thanks,
Dave
I'm not sure of all the particular demands of your application, but could a Slippery 8 Loop be adapted to do the same thing?:

http://notableknotindex.webs.com/slippery8.html
« Last Edit: March 04, 2011, 05:24:58 PM by roo »
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SS369

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Re: Bowline Cinch
« Reply #6 on: March 04, 2011, 05:28:53 PM »
Hi Dave.

No I don't have any pictures at present. Didn't think my passing the end through the open loop needed graphics.
I haven't needed a set up like this during my climbs though I can see a potential use of being able to adjust the length of a Prusiking sling at infrequent times, etc.
I'm not dissing your set up, far from it, I am trying to see the or any advantage to it for my own use.
And just doing the feedback thing as requested.

Did you capture any pictures of the Instron test? I would love to see which nipping coil the break occurred. And any other testing/pictures you care to share.

Thanks.

SS

Dan_Lehman

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Re: Bowline Cinch
« Reply #7 on: March 04, 2011, 09:28:53 PM »
I would love to see which nipping coil the break occurred. And any other testing/pictures you care to share.

There's only one that's under any real strain --that would be it.

Though, if one adheres to "AllAboutKnots" article about where the
break occurs, you'll be amazed that it indeed occurs in the loop
and not the "stem"!


 ;)

Dan_Lehman

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Re: Bowline Cinch
« Reply #8 on: March 04, 2011, 10:02:10 PM »
Here is a not I developed for climbing and mountain rescue.
I would appreciate any feedback.
http://www.milesgear.com/BowlineCinch/BowlineCinch.html
Thanks,
Dave

Dave, welcome to the scene!   :)

Regarding this knotted structure, I'm not happy with a few things
about it:
 I find the tuck of the structure's tail to be insecure
(yes, so it held to break in a test, but, still, I don't like it's
too simple pass-through in this knot (bowline )).

And I'm not happy with how the reeved tail loads the knot.

As I understand your  desired structure, you want a small eye
at one end and an adjustable eye (essentially) for the remainder.
And you want the structure to be self-locking (as opposed to there
being a tie-off step).

It occurs to me that one could use a bowline-terminated end
but then bring the "tail" (of the structure --the S.Part of the
bowline, as you show) up through a larkshead/Girth Hitch
through the 'biner and back down through (so, twice through
the larkshead); the tail will now be twice-nipped by both of
the two loops of the larkshead.  This seems to slip a bit as
tension is built and the loops tighten.

I know of a (what I call) "symmetric Fig.9" eyeknot in which
this pass-through of a tail seems to be well nipped if loaded qua
eyeknot (and not end-2-end loaded or ringloaded).

And the structure that Roo gives as a "Slippery 8" would suit this
task better if the tail is reeved through in the opposite direction
(which I name "Quick8"), AND you make the Fig.8 a Fig.8 eyeknot
to start with (replacing your YoBowl).  This seems well secure and
easily adjusted and reasonably easily untied, I think, given the
extra strand running through the knot.
And one could try the same thing but with the tail run up around
the 'biner and then brought back into the knot (nice the the Fig.8
is the same "comin' as going'", for this).  It seems that this should
be slightly stronger, but ... --you're not going to be breaking ropes.


Btw, is that  Bonati 'biner (w/orange (& red-taped?) gate)?
--looks similar but differently stamped to an OLD 3_000kg fat
one I have.

Cheers,
--dl*
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davidmiles

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Re: Bowline Cinch
« Reply #9 on: March 04, 2011, 10:53:25 PM »
Roo,

I like the Slippery 8 Loop.  It's a little to harder to adjust than the one I posted.  Very important to be able to do with one hand while climbing and not require a lot of effort.  This one does require that both strands of the loop are loaded the same.  This is done by the biner.  Do you know the break strength % for the Slippery 8 Loop?  I have other applications for it. 

Dan,

I know that it does not look like it would hold that one strand as well as it does.  I was actually very surprised by the strength.  I was hoping for 1500 lbs in 8mm cord.  This would be similar to another surprising knot I made 3 years ago.  I called it the secure bowstring.  It is a bowstring knot formed with a double overhand knot instead of a single overhand.  This prevents it from traveling down the rope.  We use this on our rescue stretcher now.  It will slip at 1500 lbs until it reaches the stopper knot and then hold full strength (8mm cord).  In fact, out of the 3 samples shown here for testing, one broke at the figure 8 on the bight first!

http://www.milesgear.com/SecureBowstring.jpg

I really appreciate everyone's feedback on this.  My friends are tired of me showing them knots.

Dave

roo

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Re: Bowline Cinch
« Reply #10 on: March 05, 2011, 12:25:22 AM »
  Do you know the break strength % for the Slippery 8 Loop?  I have other applications for it. 
Break strength percentages for knots in rope are fairly irrelevant, in that if you're even close to approaching the breaking point of the knotted rope, you're doing something horribly wrong.  A rope loaded too heavily can rupture if it encounters a tight curvature from passing over miscellaneous objects even if you had huge, gentle-curvature knots employed at all other points.

Having said that, it's a good estimate that no knot will reduce the strength of the rope by more than 50%.   For a given knot there are a range of breaking strengths based on how the knot is drawn up, the rope material, construction, etc.  I actually prefer to assume a 50% reduction simply because it's hard to be confident of the bell-curve boundaries of knot breaking strengths when only a few dozen tests are conducted in a limited selection of rope, with a limited range of knot dressings, as is typically the case.
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roo

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Re: Bowline Cinch
« Reply #11 on: March 05, 2011, 12:35:10 AM »
Here is a not I developed for climbing and mountain rescue.
I would appreciate any feedback.

http://www.milesgear.com/BowlineCinch/BowlineCinch.html

Thanks,
Dave
I'm finding that this mechanism slips too easily from imbalance in the legs.  In the real world such imbalances will regularly occur from swinging and other similar motion.
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davidmiles

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Re: Bowline Cinch
« Reply #12 on: March 05, 2011, 12:42:54 AM »
Roo,

Yes, the legs must have near equal loads.  Have you tried clipping in with a harness and hanging on it.
That was my first test in the garage.  Swinging and bouncing get get a little slip and re-adjust, but it's stable.
I you just pull on the loop with you hand, it's easy to get it to slip.  However, I do want it to be easy to adjust with one hand.

Thanks,
Dave

Dan_Lehman

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Re: Bowline Cinch
« Reply #13 on: March 05, 2011, 01:12:25 AM »
I like the Slippery 8 Loop.

And the reversal of that that I suggested?

Quote
I was hoping for 1500 lbs in 8mm cord.

What is the strength of the cord?  (nylon?)
#3000?

Btw, on your URLinked page in the OP, you say that the bowline
is good for 3-way loading and thus other connections can be
clipped into its eye (or, that was my take of what you said):
I wouldn't do this, as the bowline is very poor on ringloading
--i.e., pulling the eye apart--, though the Yosemite finish will
help.
Quote
I called it the secure bowstring.  http://www.milesgear.com/SecureBowstring.jpg

A s for your 2nd-linked-to knot, I'd love to have seen what shape
it took when the Fig.8 failed (or simply at any high load) --assuming
that that was a high break strength--, for Fig.8 eyeknots generally
are the survivors.  (You dressed yours one way of various ways.)

AND, I suggest that you send the tail from the would-be double
overhand
out where you have the stoppered tail finishing (which,
yeah, means that you in fact have but a single overhand in the
mainline), and run the tail through both turns of the (*had been*)
double overhand --you should be able to visualize this from the
photos of the knot, just swapping positions/connections.
What this does is give the central knot the form of a sort of
*minimal* ProhGrip (Blake's hitch) gripping the tail.
(And I'd otherwise have run the tail through the full round turn
of the double overhand (which it can be said is loaded partly
like the Anchor Bend ).)

--dl*
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davidmiles

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Re: Bowline Cinch
« Reply #14 on: March 05, 2011, 03:26:55 AM »
Dan,

I haven't tried the Quick 8 you mentioned yet.  I'm kind of pressed for time since every MRA team in CA is getting together tomorrow to do our Rock Recertification.  I will be out for a day or two.  Plus my side business of making bivy sacks limits my knot play right now.  I will be playing with this knot at our recert and should have some notes when I get home.

Is there a better way to dress that figure 8 on a bight?  We use interlocking Bowline with long tails to attach our main and belay lines to the stretcher.  They are much better for ring loading than a figure 8 on a bight.  With rescue we also have to face the challenge of everyone on every team being able to recognize and check you knots.  This makes it difficult to introduce new knots.  This is very important since the knots never break.  Failure occurs from mistakes or bad edge protection for the rope.  KISS principle definitely applies in the cold night rescue.

Secure Bowstring
Don't remember the cord strength, but the last sling with a grapevine knot broke at 6500 lbs.  I have the old broken samples and will try to scare up a picture or two next week.  Is there a better way to dress that figure 8 on a bight?

Haven't tried the other suggestions yet.  I'll get back to you.

Thanks again,
Dave