Author Topic: Two half hitches versus two reversed half hitches and other hitches etc.  (Read 18947 times)

Dan_Lehman

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You're proposing a Double Loop instead of the Girth Hitch I have pictured? 

Well, yeah, I guess that would be one way, which hadn't
occurred to me.

What I see wrong is this:  the support structure goes from 3-lines
across to a single strand weak point (at whichever knot).

Rather,
replace the girth hitch (which could equally be a clove h. )
with a pile hitch-like anchorage built w/round turn on the vertical
pipe and half-hitch on the horizontal (this orientation because the
former would be more susceptible to being pushed around the elbow?),
and now twin strands run towards the lower pipe turn --which one can
make and then you make a tensioning structure between the ends
on the open span (as you have).
.:. This gives 2 strands across the entire span, no single-strand weak spot.

Alternatively, one  could girth the vertical pipe and then
half-hitch (with the twin lines) the horizontal --might be simpler
to tie and better in abrasion/chafing at the point of crossing
for the half-hitch's feed into the span.


--dl*
====

xarax

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a pile hitch-like anchorage built w/round turn on the vertical pipe and half-hitch on the horizontal
 girth the vertical pipe and thenhalf-hitch (with the twin lines) the horizontal

  Where are the KISS and SISS ( : symmetric is simpler ) principle in this ?  :)
« Last Edit: July 31, 2011, 11:40:39 AM by xarax »
This is not a knot.

knot4u

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Rather,
replace the girth hitch (which could equally be a clove h. )
with a pile hitch-like anchorage built w/round turn on the vertical
pipe and half-hitch on the horizontal (this orientation because the
former would be more susceptible to being pushed around the elbow?)...

There is no risk of the rope being pushed around the elbow.  It's PVC pipe with an elbow joint that provides a step over which the rope cannot slide.

When I designed this thing, I wanted the direction of the force to extend from the center of the corner between the pipes.  The Cow Hitch naturally centers itself.  (A Bull Hitch may be even better because it would tend to squeeze the sling legs together.)  In contrast, a fixed double loop would not naturally set itself on the precise center between the pipes.  A Pile Hitch would be even less centered.

Having said all that, being centered on the corner is UNNECESSARY.  Notice the opposing ropes are NOT centered on the corners.

I do like the idea of extending the sling so there is no undue weakness at the single point.  Unfortunately, I cut the ropes, and so the ropes aren't long enough to tie a Versatackle or Trucker on a sling.  Anyway, I don't think these ropes are close to breaking.  Is there another reason to eliminate the weak point?

If I did this again, I'd try Dan's idea.  I'd use a Pile hitch instead of the Cow Hitch, and I'd tie a Trucker or Versatackle on the extended sling.  Like I said above, the force does not need to extend from the center of the corner.  In fact, the off-center of the Pile Hitch would cause its Versatackle to be closer to the polar opposite of the criss-crossed Verstackle.  See the pic.
« Last Edit: July 31, 2011, 06:05:04 PM by knot4u »

Atomic

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In my line of work (powerlines) we use a rope rig to pull in wire. When we get to the wire stand I like to "make fast" to it using a half loop and two half hitches and then another half hitch in the bight as a safety in case the standing end becomes slack the half hitches won't flip out. I pass a bight through the eye then tie an overhand knot which I flip into a half hitch by pulling the standing end to throw slack so the bight can be pulled. The ropes are usually tight enough to be clear of roads and existing powerlines but not so tight that two people can't pull them one at a time if necessary. The reason for the bight being pulled through the eye is that I can connect the end of the rope to the wire with a kelm grip and swivel without having to have someone to hold the rope tight. Then if necessary the whole half hitch set up can be flipped out by one person losing only 8 or 10 feet of slack that's not going to amount to much over 5500 feet.

Not sure if this will help with your situation but maybe you'll find a use for it someday.

knot4u

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In my line of work (powerlines) we use a rope rig to pull in wire. When we get to the wire stand I like to "make fast" to it using a half loop and two half hitches and then another half hitch in the bight as a safety in case the standing end becomes slack the half hitches won't flip out. I pass a bight through the eye then tie an overhand knot which I flip into a half hitch by pulling the standing end to throw slack so the bight can be pulled. The ropes are usually tight enough to be clear of roads and existing powerlines but not so tight that two people can't pull them one at a time if necessary. The reason for the bight being pulled through the eye is that I can connect the end of the rope to the wire with a kelm grip and swivel without having to have someone to hold the rope tight. Then if necessary the whole half hitch set up can be flipped out by one person losing only 8 or 10 feet of slack that's not going to amount to much over 5500 feet.

I know that's probably not that complicated, but I just can't understand it without a pic.  I read it twice.

Atomic

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I'll try to get one when I get back to the house. I have some rope in the truck that should show it pretty well. The half hitches are in tied in the load part of the line. The safety is in the bight part of the line.

Dan_Lehman

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There is no risk of the rope being pushed around the elbow.
It's PVC pipe with an elbow joint that provides a step over which the rope cannot slide.

So I see; but the offered solution doesn't depend upon this,
thus has generality also as a benefit.


Quote
Unfortunately, I cut the ropes, and so the ropes aren't long enough to tie a Versatackle or Trucker on a sling.

By the looks of both the lengths of tails AND the extent
of overlapping at tensioning structures (rather long),
you have ample rope to re-rig as described.  Beyond
strength --re the single strand-- is **stretch**:  a single
strand will stretch more than doubled, trebled strands.

The suggested improvement is sort of worked qua sling
only at the upper attachment (the girth + half-hitch) ;
it is then a structure of two ends joined with tensioning
mechanism (Versatackle or Gleipnir or ...).
So, you will consume a little more rope at the upper corner,
but not elsewhere (and this is only for the two --each side--
attachments that use the girth h. and not those going
on the complementary diagonal, which have eye purchases).


--dl*
====

xarax

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a fixed double loop would not naturally set itself on the precise center between the pipes.

  A fixed double loop where the two loops communicate, will ! You have discovered an(other) application that answers to your question :  

Does someone know of an application where it's desirable for loops to communicate?
« Last Edit: July 31, 2011, 08:56:22 PM by xarax »
This is not a knot.

knot4u

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a fixed double loop would not naturally set itself on the precise center between the pipes.

  A fixed double loop where the two loops communicate, will ! You have discovered an(other) application that answers to your question :  

Does someone know of an application where it's desirable for loops to communicate?

You would be correct.  It follows that the Cow Hitch part within a Girth Hitch is arguably the simplest double loop that communicates.  Notice I didn't say "fixed", and I don't consider any double loop that communicates to be "fixed".  For example, I don't consider a French Bowline to be a fixed double loop because the loops communicate.

Anyway, it's all academic because if I did it again, I'd run the sling the entire length.  That rules out the double loop that has a weakness at the single point.
« Last Edit: July 31, 2011, 09:11:58 PM by knot4u »

xarax

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a French Bowline is not a fixed double loop because the loops communicate.

   To my mind, a "fixed" loop in a loop that simply is not a "noose". So, a fixed double loop is simply a double loop that is not a double noose, so it can have two loops that communicate, communicate with some difficulty, or do not communicate at all. I am not sure about the correct nomenclature here...
This is not a knot.

knot4u

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a French Bowline is not a fixed double loop because the loops communicate.

   To my mind, a "fixed" loop in a loop that simply is not a "noose". So, a fixed double loop is simply a double loop that is not a double noose, so it can have two loops that communicate, communicate with some difficulty, or do not communicate at all. I am not sure about the correct nomenclature here...

Well, if you call a French Bowline fixed, at least put a WARNING label on it if you recommend it to a disinterested "customer".  :D
« Last Edit: August 01, 2011, 06:58:21 AM by knot4u »

Atomic

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Please note that while there is load on the line it isn't a great load. There are drums of rope that have breaks on the drum to keep them from spooling and the load is the weight of the rope and the tension of the break. By the end of the spool you are keeping around 5500 feet of rope above road crossings.



Here you just pull a bight through an eye. I put a bowline on the end to distinguish the normal working end of the rope. In real world it's an eye splice in braided rope. Also the load end isn't under load in these pictures but use your imagination, I had to take the pictures and tie at the same time.



Go over the rope and back under tying an overhand knot but pull slack in the load line and pull the bight towards the load.



It flips the load line into a half hitch. Do this one more time.



Then add the half hitch to the bight for safety. If you don't have this the other hitches could be twisted out inadvertently. The eye can be attached to our wire through a swivel and kelm grip and the whole shabang can be loosened by one guy in a lot of cases. Never passing the eye splice through the eye (in this case the pennel hitch) it makes it easy to hold until you don't need it to.

Here
is the link to the album in case you need to view them in larger images.

knot4u

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By the looks of both the lengths of tails AND the extent
of overlapping at tensioning structures (rather long),
you have ample rope to re-rig as described.  Beyond
strength --re the single strand-- is **stretch**:  a single
strand will stretch more than doubled, trebled strands.

The suggested improvement is sort of worked qua sling
only at the upper attachment (the girth + half-hitch) ;
it is then a structure of two ends joined with tensioning
mechanism (Versatackle or Gleipnir or ...).
So, you will consume a little more rope at the upper corner,
but not elsewhere (and this is only for the two --each side--
attachments that use the girth h. and not those going
on the complementary diagonal, which have eye purchases).

If I don't do something similar on the complementary diagonal, it's kind of like what's the point of your suggested improvement?  The opposite diagonal would still have that single point weakness, right?  So, on the complementary diagonal, I'm thinking a regular Cow Hitch and then a Trucker (or Versatackle) on the extended sling.
« Last Edit: August 01, 2011, 03:19:24 AM by knot4u »

knot4u

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Thank you, Atomic.  That is a Bell Ringer with Half Hitch (ABOK #173) PLUS a Half Hitch formed by the top bight of the Bell Ringer.


ABOK #173

Add a Half Hitch by using the top bight to get Atomic's contraption:


Topologically, it's three Half Hitches total.
« Last Edit: August 01, 2011, 03:47:25 AM by knot4u »

Dan_Lehman

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If I don't do something similar on the complementary diagonal, ...

Ah, yes, what I was thinking of was just the substitution
for the current girth hitch --yes, you would want to take
a different rigging vis-a-vis the single strand segment;
but this is a clearly simple thing to do.

--dl*
====