Bowline Extensions for Security

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Re: Bowline Extensions for Security

Postby Chads93GT » Jan 1, 2009 2:18 pm

ek wrote:EDIT: Replaced an instance of "bowline" with "figure eight" where "figure eight" was originally intended. ("well, you know how long it can sometimes take to untie a figure-eight")

Are you reading On Rope, 2nd Edition? That is the most current edition.


I have the version copyrighted in 1996, has an autograph in the binder from 1997, so I doubt its the 2nd edition? I figured the bowline was used for the same purposes as the figure 8 and you are right, untying the figure 8 is a pain in the ass. After taking a few whippers rock climbing, untying the 11mm rope from the harness is a royal pain after your fingers are burnt out from.

Thanks for the info.

When you tie off to a tree, for an anchor to rappell into a pit, do you tie a bowline around the tree, or do you simply wrap the rope around the trunk a few times then clip the end back onto the main rope. I always figured a fig8 or bowline around the tree is what people did, but people I know wrap the rope around the tree. Either way works fine I guess?
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Re: Bowline Extensions for Security

Postby Bob Thrun » Jan 1, 2009 2:39 pm

Heinz Prohaska presented his thoughts on bowlines in Nylon Highway No. 26, May 1988. Note that he does not use the term "Janus Bowline", he uses the term "Double Bight Bowline". NH26 is not posted on the Vertical Section pages. I find that I can make a high resolution scan and post them as pictures here. I would like to attach a PDF to this message, but that option is not available here.

Image

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Last edited by Bob Thrun on Jan 1, 2009 7:52 pm, edited 1 time in total.
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Re: Bowline Extensions for Security

Postby ek » Jan 1, 2009 6:23 pm

Chads93GT wrote:I have the version copyrighted in 1996, has an autograph in the binder from 1997, so I doubt its the 2nd edition?

That sounds like the 2nd edition to me...but the real key is of course to look and see if it says "2nd Edition" on it. The 2nd edition is indeed copyright 1996 (an excellent and informative source, though!). The first edition is even older.

Does the cover look like this?

Chads93GT wrote:I figured the bowline was used for the same purposes as the figure 8 and you are right, untying the figure 8 is a pain in the ass. After taking a few whippers rock climbing, untying the 11mm rope from the harness is a royal pain after your fingers are burnt out from.

Well 11mm rope is generally easier to untie than thinner rope.

But...why are you using 11mm rope for leading? You'd probably be fine with something a bit thinner...

Chads93GT wrote:When you tie off to a tree, for an anchor to rappell into a pit, do you tie a bowline around the tree, or do you simply wrap the rope around the trunk a few times then clip the end back onto the main rope. I always figured a fig8 or bowline around the tree is what people did, but people I know wrap the rope around the tree. Either way works fine I guess?

You may recall from my earlier post that I referred to the tensionless hitch. That means wrapping the rope around the tree (at least twice) and affixing the tail via a loop knot to the standing end of the rope (the end that's going down the pit). This can be done with a carabiner or maillon (usually with a figure-eight on a bight), or it can be done by tying the tail of the rope directly around the standing end (usually with a rethreaded figure-eight or bowline).

The tensionless hitch tends to hold very well onto the object wherever it is tied, so it's good for tying around trees when you don't want it to slip down toward the base. Provided that it is tied to that the wraps don't cross one another and there is no (or very little) load on the knot, the tensionless hitch is easily releasable under load, and can even--with extreme caution--be slowly unwrapped to the point (with about one full turn around the tree) where it can be used to lower someone down if they're stuck. (To do this you either had to have rigged it in the middle of the rope, or tie on another rope before unwrapping it.)

The other benefit of the tensionless hitch, which is the most common one bragged about but actually by far the least important, is that if it is tied correctly around a large enough object (4" or greater diameter, generally), it preserves 100% of the strength of the rope. If you're throwing a rope down into a pit and this matters, then something is already very, very wrong. Anyway, if you were to do a pull-test or a drop-test of common caving rigging, the weak part of the rope would usually be where the rope goes over the lip rather than the anchor knot. Also, in a shockload, your descender will slip, and your ascenders will cut the sheath and pull it down at lower forces. A locked off descender (which is like a knot) will likely be weaken the rope more than an anchor knot too, and an ascender will sever the rope at a far lower force than any approved anchor knot. (If you're lucky then on a 11mm 30kN rope your ascender might not cut the rope until a force of 6kN is achieved.) On the other hand, when dealing with tensioned highlines and the wide-angle force multiplication entailed therein, tensionless hitches are one way to rig so as to preserve every last ounce of the rope's strength.

Because of these advantages and the simplicity of the method, the tensionless hitch, also called the HSA (high strength anchor), is by far the most common way for cavers--at least in North America--to rig at the end of the rope to a tree or other object with a near-circular cross-section and without sharp edges.

To answer your question about what I do personally, I most often use a tensionless hitch. I have never simply rigged around a tree with a bowline or rethreaded figure-eight (not with the pit rope, when caving, that is), though there are situations where I would do that. On occasion I have rigged to a tree in mid-rope with a triple bowline on a bight or a triple bowline on a bight on a two-wrap coil (i.e. wrapped around an extra turn so that it doesn't slip down). Other ways I have rigged to trees include the wrap-3 pull-2, wrap-2 pull-1, and basket rigging with webbing (and tying a figure-eight or bowline or, for releasability, even a tied-off Munter hitch or descender at the end of the rope and clipping it to that anchor).
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Re: Bowline Extensions for Security

Postby knudeNoggin » Jan 2, 2009 5:28 pm

Whew, there's a load here.

You can also tie a bowline on a bight of rope. (There's a knot called the "bowline on a bight", but ironically that knot is not a bowline tied on a bight.) This is called the triple bowline on a bight (because it has three loops in total--the major loop becomes two loops and the tail becomes one loop) or the double bowline on a bight (I don't know why it's called that).


Because it is a bowline (up)on a bight--without ends.
As opposed to a "b. WITH a bight", using a bight ("loop"/"doubled") of rope.
Knots nomenclature is quite an adventure, to be sure.
Note the contrast between "Triple Bowline" and the more common use for
"Double Bowline" which is to denote the "Round-turn Bowline", a single-eye
knot with two "minor" loops in your terminology. I'd like to keep the sense
of "double" to denoting repeated/extended parts of the structure (as in
"Dbl.Sheet Bend"), and not number of eyes. But in any case, the use you're
attacking is ancient (Ashley cites 1808 ref.), and pretty common to my reading.

Your distinction of "on" vs. "with" is exactly opposite mine; the variance hinges
really more on what sense of "bight" (seemingly unchanged--in spelling) than
the nuances of the preposition, but I'd say that "with" has a better connotation
of using a structure to perform ... , and "on" more of a passive reception to
the knotting, which fits my observation of traditional useage. YMMV.

We're talking about new and different knots, with potentially quite different properties. It's worth knowing what happens when you load them heavily in a single event, before trusting your life and the lives of others to them.


Except that by the vast field data of rope useage for decades, and some common
sense about the geometries of the knots in question vis-a-vis known knots, and
the strength of the materials employed, it is beyond doubt that they will be amply
strong. I''m guessing some will prove stronger.

The Australian fellow updating the report now plans to perform testing on 5mm
kernmantle (he insists on '...mantel') accessory cord (Sterling), with 3 pieces per knot;
I've urged knots in both ends per piece, so double the tested number (and surviving
knots to examine (or later re-strain to rupture).

[re 'left-handed" connotation] You have on your side a respected (though dated) knot authority.
I was not aware that Ashley had said that. On the other hand, I have on my side an extremely simple explanation.


If one is seeking origin(s), "dated" is a plus, not the latest echoes of misunderstanding
or revisionism. But surely you have Webster's 3rd New and look up the meaning, where
"left-handed" is a colloquial expression for non-standard, dubious things!? And your
long-winded, inventive answer is quite the antithesis to Occam, of all things. Esp.
as in most all of the references I've seen, the bowline is presented as it was in the
2nd post (from NZcaver) here, mainline up (the "tree"), cross of the ("minor") loop
on left, and a Cowboy's end would thus be .. RIGHT--but that is hardly the basis for
the knot name. (And it would be foolish to think that knots books influenced those
using knots, except maybe in some specialized fields such as climbing/caving; sadly,
it seems too much that actual knotting didn't much influence knots books--only prior
knots books did that.)-:

"I don't recall the double overhand stopper finish specifically used with the Bowline ever being taught or shown in NCRC literature."
As you can imagine, the Double Fishermans/Grapevine knot itself is a staple of the NCRC diet.


But my point was: is the Strangle knot (that half-a-Grapevine) expressly noted for
being a useful security knot (whether applied to a particular back-up role or not)?!
Just having the image and knot implicitly available isn't good assurance that such
use will be recognized.

Cheers,
*kN*
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