"tensionless hitch" a misnomer?

[Scott McCrea]

Don't forget the Georgia/Virginia/Kentucky/West Virginia/Alabama/etc rig. "Wrap the rope around the tree a bunch of times and put a rock on the end of the rope."

Actually, when you wrap a rope around something, once you wrap it enough times, a securing knot is technically not necessary. The number of wraps depends on the rope and the anchor.

[ek]

I have two comments on that.

First, if you're wrapping the rope somewhere other than the base of the anchor point--for example, rigging high on a tree to make a lip easy to pass and/or to make it safer to attach/detach from the rope--then the tie-off becomes much more necessary, as otherwise your tensionless hitch will unwrap itself. (It won't slip, it will just unwrap itself until there is no longer enough tension--and then slip.) This will happen no matter how many wraps you have. This often happens to people as they struggle to tie a tensionless hitch around a large tree, with no one else there to hold onto the rope for them.

Second, the number of wraps depends on the materials of the rope and the anchor. It does not depend on the diameter of the anchor (see the capstan equation; Dave Merchant presents this concept extremely well in Life On A Line, 2nd Edition). Different tree barks have similar enough coefficients of friction that two wraps is virtually always adequate, and three always provides considerably more friction than necessary to hold a nylon cave rope in place. (That's based not just on personal experience and what everybody says--Dave Merchant has a table of friction coefficients, and I looked it up. I can't be sure that's the case for polyester-sheathed rope, but I've rigged numerous tensionless hitches with Petzl Vector 11mm polyester-sheathed rope, and three wraps always provided more than enough friction to hold the rope in place.)

Similarly, when unwrapping a tensionless hitch to lower someone (or do a slow, controlled release), you always need to unwrap it to about one full turn. The exact angle will of course depend on things like your grip strength.

Note to everyone: None of this takes into account factors like ice or mud. Most of my tensionless hitches around trees are done on the surface (where there are trees), and with clean (or relatively clean) nylon-sheathed cave rope. The coefficient of friction of a rope against a canvass rope pad used as a tree protector may be different, too. And even if your scenario is the same as what I'm describing, I am sometimes mistaken about things--so please do not risk your life assuming that what I am saying is true, without (ideally) testing it yourself in a controlled and safe environment, or at least confirming it with others.

[NZcaver]

Is this a hitch? According to the Morrow Guide to Knots “hitches are used for tying a rope to another object” and is a knot “formed with simple turns”. Sounds right to me.

Is it tensionless? Well as it has been said, there is no tension on the knot securing the end to the mainline.

What is the issue here? I see none.

[knudeNoggin]

When I was taught the tensionless hitch, I was taught that it's called that because the knot (or whatever other tie-off you use to secure it) is not (or should not be) under tension. ... it seems to me that "tensionless hitch" is enormously more correct of a term than "high strength tie-off."
Am I wrong?

Once we figure out a way to measure correctness of terms,
yes, you are wrong, possibly enormously so.
There's a sleight of hand going on here with these definitions:
"knot" is cited as apt for the thing in the tail securing (fer-sur!)
this structure, and cited to be w/o tension; but "hitch" is surely
intended for the attachment to the object --viz., tree, e.g.-- which
is quite under tension. You can't swap off as is convenient, now!

Without arguing over the reasonableness of the moniker,
I think that "tensionless hitch" might be the commonly used
name, so ... go with the flow!? (Well, Google thinks otherwise,
much to my surprise!) Frankly, I don't like either of the two
candidate names -- "tensionless" is confusing, at best, and
"high-strength" should denote more than just this attachment.
(Re that what could be stronger? issue, hmmm, not sure,
but if the anchor object if vulnerable to torque, then there
might be a problem ... .)

"Secured multi-wrap anchor" is more accurate, if not elegant.


If there were an expected need for the lowering benefits of this
SMWAnchor (pronouced just as it looks ),
and given that, as Gary remarks (as has Bob Thrun elsewhere),
"If strength was so borderline that the specific knot made the difference
..., I might very well choose a larger rope" ,
might one prefer to use 1 wrap fewer (and take some slight tension
on the closure connection --some sort of slip-knot),
so as to avoid the " need to unwrap it to about one full turn." ?!
As the nature of the SMWA certainly implies that the lowering cannot
begin without taking those further steps of relieving friction.
And my remark about strength is made to dismiss arguments that
some tension in the closure implies a weakening of the SMWAnchor,
which is just silly (likely negligible).

Bruce's "tensionful" doesn't make good sense; better were the
adjective "frictionless", then it would ("frictionful").

*kN*

postscript: My favorite found anchor was a top-rope one with
the SMWAnchor on a massive tree dutifully secured and the tail
run off through no fewer that TWO Sheepshanks (!!) and
into a 2nd SMWAnchor around a puny & seriously life-challenged sapling.
It brought tears to my eyes, and ... no camera, nor the thinking
to *borrow* a couple bits of someone's >>blue<< 1" tubular tape
to fashion the deserved 1st Prize.

[ek]

You have a good point about how it's not the hitch itself that's (idealized to be) free of tension, but rather the tie-off. Perhaps that's what Bruce Smith meant when he said that it should really be called "tension-full." The hitch has tension--the knot that ties it off doesn't.

To lend further credence to your position, it may be valuable to point out that, contrary to what is widely believed, a tiny amount of tension on the tie-off won't reduce the strength of the hitch. It still won't break at the knot, since the tension there is so small a fraction of the tension on the line entering the hitch that the line entering the hitch would surely break first. And if the angle around the carabiner is tiny--tiny enough, for example, that you could "vector out" on the standing end (which enters the cave) to release the tension--then the reduction in strength there would be minuscule or nonexistent. (And suppose our tensionless hitch is for a highline. The highline pulley would then almost certainly apply more stress to the rope then that tiny pull from the carabiner or rope loop.) Remember, I'm talking about very small amounts of tension on the tie-off.

But with regard to the number of wraps used initially, that has nothing to do with the number of wraps you need to reduce it to, to use it as a fixed-brake lower. You could start with ten wraps--you'd have to unwrap it to about one full turn to lower someone. You could start with two wraps--you'd have to unwrap it to about one full turn to lower someone. You could start with one wrap (i.e. one full turn), and it would probably be impossible to release it without a haul system, but if you managed it, then you'd have that one full turn you needed, and you would then need only increase or decrease the wrapping by a few (tens of) degrees to achieve the desired friction for a controlled lower.

But like I also said, conditions like mud or ice could create a bizarre situation where you'd need more or less friction to conduct a controlled lower. Knowing that it's always about one full wrap is no license for complacency.

[hank moon]

Is this a hitch? According to the Morrow Guide to Knots “hitches are used for tying a rope to another object” and is a knot “formed with simple turns”. Sounds right to me.

Is it tensionless? Well as it has been said, there is no tension on the knot securing the end to the mainline.

What is the issue here? I see none.