Author Topic: Best Gripping Hitch for Vertical Pole  (Read 39986 times)

Dan_Lehman

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Re: Best Gripping Hitch for Vertical Pole
« Reply #30 on: August 02, 2010, 07:07:25 PM »
Actually, this holds extremely well with a downward load without the bottom cow hitch, ....

Whoa, that simply cannot be:  if ... .  Do Not Pass GO !

You mean like this? (See attached photos.)

It holds very well at angles from 0 to 40 degrees on my marlinespike with 1/16" / 1.6 mm braided nylon cord. ...

Okay, yes, it can hold when carefully dressed & set; but it's
critical to get that tail nipped just so, rather than inevitable that it
will hold -- and a big danger lurks of spilling.  (If one can get the tail
positioned more towards the coil and against the collar/cross-part
then it will be further nipped --and at many angles-- by the SPart.)
But I'm concerned about intermittent loading and less-careful dressing.

In sum, there is a rope-on-rope nipping that can be effected, even with
the relatively large object; but the structure is not a good one to employ
in such cases.   Whereas some of these others, where the rope-on-rope
nipping is effected deliberately and more surely/stably, are sure bets.
(Along the lines of thought here, one might consider the Ossel Hitch on
a spar (i.e., an object approximately 3-5x rope diameter) vs. this same
hitch in reverse (pulled by the tail) --the former won't hold as space
opens where nipping  should occur; the latter nips in the rope tangle,
independent of the object.)

 - - - - - -

There can be subtleties of dressing & setting of these friction hitches.
I found one case where the ProhGrip/Blake's wouldn't grip but slide
until I loosened it such that there was some greater spiral at
the start and less turn -- i.e., the angle of incidence was more
towards the  parallel and away from the perpendicular.

It seems to me that loading the near end of the coil will work
better, as loading the away end can bring pressure against the
coil without tightening it (as the SPart bears into the coil), whereas
on the near-pull structures, the extension of the coil occurs with
a tightening effect on it.

--dl*
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Dan_Lehman

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Re: Best Gripping Hitch for Vertical Pole
« Reply #31 on: August 09, 2010, 04:59:22 AM »
   What is a -slippery- vertical pole ? The shank of an eye-less oversized hook.  :)  Should we try fishing knots, that tie lines to hooks, as gripping hitches, possibly better than the above ? Just a -naive- quick question.

I've been surprised to see some that do, i.e. some hooks
that have no eye (though sometimes something of a
different shape at hook's unsharp end).

But, no:  consider that fishing knots can be set with high
relative (to tensile, to expected loading) loads; not so with
rope (conceivable, but no practically the case).  And then
consider also that those fishing knots aren't expected to
UNgrip and be repositioned.

--dl*
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Dan_Lehman

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Re: Best Gripping Hitch for Vertical Pole
« Reply #32 on: August 09, 2010, 07:15:41 PM »
Note that those "eyeless" hooks are not simply straight shanks
-- they have that flattened knob on the end, at an angle.

Some of these knots sure look dubious re strength, IMO -- in
that there is that hard, 1-diameter turn of the SPart going
through coils that aren't tightened by loading, only setting!?

One of the Strangle forms --roughly the center image-- has the
end exiting beneath where it would normally cross over the
shank --wonder if this is intended or some artistic invention?

--dl*
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knot4u

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Re: Best Gripping Hitch for Vertical Pole
« Reply #33 on: August 09, 2010, 10:56:02 PM »
I wonder, on a vertical pole with square cross section, would the same task be more or less difficult ?

That's MORE difficult, at least with the hitches I've tried from this thread.  The friction is concentrated primarily on the pole corners.  The square pole also experiences more stress and wear because of the hard forces at the corners.

In contrast, the round pole experiences uniform friction (and more friction) on the entire circumference of the pole where the rope makes contact.  Also, there is less wear.
« Last Edit: August 09, 2010, 11:00:57 PM by knot4u »

SS369

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Re: Best Gripping Hitch for Vertical Pole
« Reply #34 on: August 09, 2010, 11:23:36 PM »
Perhaps I missed it while rereading this thread, but are we looking for a hitch that is permanent? Or one that must endure all manner of tugs and cycles of loading/unloading? Be able to be relocated along the pole?

I recently had to remove a pump from a very deep well and the pipe (could be considered a vertical pole) was a very slick, moist plastic. I used a Prusik that was formed using a bowline as the base knot to fasten the working and standing parts together. I opted for three coils in 3/8 braided nylon rope.

The knot performed admirably and I was able to "inch" it up after getting the pump to break loose. I had the use of a come-a-long to do the initial grunt and from there on out man power did the rest. Not once during the 300 feet of pipe did the knot fail to grip, at least that I could discern.

It gets my vote, all things considered.

Scott

SS369

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Re: Best Gripping Hitch for Vertical Pole
« Reply #35 on: August 10, 2010, 01:36:00 AM »
Hi knot4u,

It is the first slide and grip I usually think of and it seems to always work well for the odd jobs I run into in the field of construction.  Works on irregular shapes pretty well too.  If you make a loop of some secure type first to bind the rope to itself and then use the loop to make the hitch.
And no way to install it backwards. ;-)
If I have to do another well pump removal, I will try to remember to try a Klemheist.

Tonight I tried the Prusik on a piece of polybutylene pipe I have in my dungeon (knot lair). I tied it using some recoil starter rope ( very tough cord) and tried valiantly to make it slip and though I had a tough time with anchoring the pipe, I used considerable strength and it did not slip. Was easy to untie even.

Scott

Dan_Lehman

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Re: Best Gripping Hitch for Vertical Pole
« Reply #36 on: August 10, 2010, 10:12:55 PM »
... an ordinary snell knot, with no strangle knot buried underneath the snelling "envelope".

You're confused:  the Strangle knot is what all of these
images show that fit this general mold -- there is only a simple
knot "buried" within a Strangle, if you want to talk that way
-- but they all have it (it might take a partial unwrapping for the
simple knot's crossing to become visible, but it's there).

And in my note above, it was a similar difference in artistic presentation
that temporarily threw me off -- perhaps one could so dress the knot
and with deliberate setting have it hold, but otherwise it rolls around
into proper Strangle form.

And all this surprise at the knot not holding so well is precisely as
I explained:  in fishing line, one sets knots at much higher relative
loads; in rope, that potential is seldom realized, and the knots must
tighten under load a good deal beyond what is set.

--dl*
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Dan_Lehman

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Re: Best Gripping Hitch for Vertical Pole
« Reply #37 on: August 11, 2010, 04:17:22 AM »
My impression is that there are two distinct general patterns, and not just one.
In the first, in the ordinary snell knots, the lines buried under the ( many, at least 7) snelling turns run parallel to each other, they do not cross. The many turns is their mode of securing the tail.
In the second, in the twisted eight knots, the lines buried under the ( few, mostly 4) snelling turns form a strangle knot, they cross. The strangle knot is reinforced by the overlapping riding turns. The crossed ends are their mode of securing the tail.

Let me try again --though I expected that "Strangle knot" alone
was sufficient (Ashley #<whatever>).  In the square page of knot
images that you posted above,
 the top-left knot is a (Double) Strangle knot; it's seemingly parallel
 ends in fact cross, but not in this image -- they will do so in setting;

 the 2nd-from-top-left is <who knows>; it you slide it off of the
 object, it can be manipulated into a *Fig.12* knot (where this
 nomenclature takes "Fig.8" and adds to it as one end turns
 around the other before being tucked out through the loop
 formed at the other (u-turn) end of the structure (the initial
 member would be the Overhand, then Fig.8, Fig.9, Stevedore
 (Fig.10) ... and so on.
 In some thin, finely braided cord around a pencil, this knot
 didn't even hint at holding; in the Fig.12 orientation, and set
 firmly (given small size of material), it grudgingly imparted
 some resistance, but slid pretty easily;
 BUT, then loaded in the opposite direction --as you have
 suggested for the Strangle-- , it held surely (this taken immediately
 from the hard setting and loading of prior test) !?  Interesting;
 but I'd suspect though well gripping, it is not strong;

 Left-center is a Double Overhand knot which will tend to draw
 up into a Strangle (as depicted to its right).  Note why I favor
 "Strangle" as the base for the nomenclature and not "Overhand":
 looking at the full overwraps, one matches their number to the
 name, for "Strangle" (and for "Grapevine") --as the base knot
 has one, in contrast to the Overhand which has zero (and so
 a "Double Fisherman's" = a "(single) Grapevine", the latter
 having the easy wraps-count match, unlike the former).

...in fishing line, one sets knots at much higher relative loads; in rope, that potential is seldom realized, and the knots must tighten under load a good deal beyond what is set.

Quote
I agree. But there are some rope knots, like the constrictor, and in a lesser degree the strangle knot, where the riding turns keep the accumulated tension of the crossed ends constant, and, as a result, we have a highly tensioned, jammed, knot.
???

You completely miss the point:  it has nothing to do with the knot,
but with the relative force vis-a-vis breaking strength in setting it!
Yes, the Strangle will hold those 50#-force you impart:  now, in fishing line
of suitable strength not to have broken, that's rather close to the
maximum strain it can take; in rope, nowhere close.  (Okay, it's not
the breaking strength per se -- snap a magic wand on any gripping
knot and raise it's material's strength by 100 and it doesn't then
slip; but you get the idea -- fishing knots get set to a pretty high
percentage of the force they are going to see,
and to have the same condition for rope you would need to
take some quite unusual setting method.

--dl*
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Dan_Lehman

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Re: Best Gripping Hitch for Vertical Pole
« Reply #38 on: August 12, 2010, 09:40:14 PM »
the top-left knot is a (Double) Strangle knot; it's seemingly parallel
 ends in fact cross, but not in this image -- they will do so in setting;

No, there is the picture of a snell knot. The double strangle/ double overhand /double eight knot is shown in the bottom left picture.  No, they will not cross. They will not cross underneath the snelling turns, and get compressed by them as in the double, or quadruple, strangle knot. It is a standard snell knot, see the many web pages that have methods if tying it, and pictures of tied hooks with it. When the line is transparent enough, you can see the lines running parallel to the hook s shank.

Togologically, the knots are the same.
I find it impossible to believe that the top-left form can
be set tightly and maintain its apparent form -- those ends
must bear against something when they are set, and then
from which the tension is delivered to the overwraps;
and what they bear against is each other (as there is
nothing else).  Now, you go find your supposed photos
of actual snells that contradict this!

--dl*
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knot4u

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Re: Best Gripping Hitch for Vertical Pole
« Reply #39 on: December 28, 2010, 08:36:14 PM »
The "Well-Pipe Hitch" is ABOK #504. You'll find that having more than four coil rings is unnecessary and can sometimes be problematic. Two Half Hitches will get the job done, but it is amazing how a Fixed-Gripper Knot instead of Two Half Hitches (or the Buntline Hitch knot) can noticeably improve the performance of the construct. A Fixed-Gripper Knot can be made tight, be pushed flush into the coil, stay put, actually aid the grip itself, and do the job noticeably better than either Two Half Hitches or (the component knot of) the Buntline Hitch.

The Fixed Gripper is awkward in this situation (i.e., replacing Two Half Hitches in Well Pipe Hitch).  Once the Fixed Gripper is set, it's a pain to perform additional tightening, which is almost always a good thing to do.  For reference, here is the Fixed Gripper (aka, Derived Hitch):
http://igkt.net/sm/index.php?topic=1839.msg12495#msg12495

In comparison, tying the Well Pipe by using Two Half Hitches (or Buntline) allows easy additional tightening.  It's also easy to remember even after months of not tying this knot.

I continue to like the well pipe hitch as being the most obvious simple smooth pole hitch -- six or so turns away from the direction of load then a clove hitch around the standing part with the tail.  If you want to make it secure against jerking, you can make a multi turn buntline with six or so turns away from the direction of load then an inverted clove hitch around the SP with the tail.

I agree.
« Last Edit: December 29, 2010, 02:13:13 AM by knot4u »