Author Topic: Versatackle ABOK CrossRef#  (Read 10392 times)

Dan_Lehman

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Re: Versatackle ABOK CrossRef#
« Reply #15 on: May 11, 2012, 08:07:02 AM »
Thanks 369, in my confined space rescue class,
we were taught to always add a safety measure to any knot.
What is the cost of a few more inches or feet of rope to ensure security?
Rope is cheap, human lives or equipment are not.

How are you taught to join rope ends?  --perhaps w/a grapevine bend?
What safety measure does the class suggest for that?!

As Roo replied, "those extra inches or feet of rope could cost you much
needed time as you tie and untie them or it could cost you needed reach."

These points are also made by OnRope1.com's Bruce Smith, in
that site's MythBusters collection --and one of that set that
I mostly concur in (and the grapevine bend case is raised there). 

But it's a tricky situation of wanting to ensure safety vs. trying to
instill and demand competence : if you get it right in the basic knot,
why go further?  There is a positive answer to this, but it should
not yield ground to strong efforts to get it right !

Btw, does this class stipulate some set of basic knots for use?
(Typically such classes do, wanting to build uniformity in the
practice --which itself has safety aspects.)  If so, which ... ?


--dl*
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firebight

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Re: Versatackle ABOK CrossRef#
« Reply #16 on: May 23, 2012, 07:37:41 AM »
First, I see what you mean about knot strength VS security. Knot strength as I read it is the breaking strength of the knot in proportion to the rope strength. Say your rope will break at 100 lbs. and the knot breaks at 70 lbs. the knot efficiency would be 70% (I just picked those numbers for ease of clarity). Google yielded this tidbit on knot security:

Quote
Security

Even if the rope does not break, a knot may still fail to hold. A knot which holds firm under a variety of adverse conditions is said to be more secure than one that does not. The main ways knots fail to hold are:
Source of above text: http://en.wikibooks.org/wiki/Knots/Properties_of_knots

While using Google to find data on knot security all I could find was knot security in medical usage such as sutures. So if I have a rescue line and my line is to short, I would maybe put a bend to attach another rope. So in attached image I made a 2 inline fig8 bend. It would seem to me this would enhance security a great deal, what say you?

Now for your last question, yes we have task books that have to be signed off, one section of the task books was knots, for this particular class we had to master the following knots, tie each one under 30 seconds:

    Figure 8 Stopper
    Figure 8 on a bight
    Figure 8 Follow Thru
    Figure 8 Bend
    Square Knot
    Overhand Bend
    Double Fisherman Bend
    3-wrap Prusik
    Modified Trucker Hitch
    Basket Sling
    Single Loop Anchor Sling
    Wrap 3 Pull twice

Of course we learned many more, but the above mentioned knots were the minimum requirement.

knot4u

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Re: Versatackle ABOK CrossRef#
« Reply #17 on: May 23, 2012, 08:06:43 PM »
I like the list. It should allow somebody to accomplish many rope tasks in a safe manner.

=====

I don't like the Two Figure 8 bends in series. It looks like something a novice would tie, with the idea of "just tie more knots." It would be difficult to set right. If there's a slack on one rope between each Figure 8, then that would be difficult to get out and wouldn't get out under load. A better, more elegant knot is one Fig 8 Bend backed up with Strangle knots on each side:

http://ojaisar.org/photogallery/Knots/Figure%20Eight%20Blend_400w.jpg

By the way, a Figure 8 Bend is already quite secure. I don't imagine someone doing anything to it to "enhance security a great deal". It's already there. The Strangle Knots in the pic above just add to the bomb-proofing.
« Last Edit: May 23, 2012, 08:17:57 PM by knot4u »

firebight

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Re: Versatackle ABOK CrossRef#
« Reply #18 on: May 23, 2012, 10:06:56 PM »
Quote
A better, more elegant knot is one Fig 8 Bend backed up with Strangle knots on each side:

Wow, great insight, and your knot looks much cleaner. I am gonna try that method.

I should point out that in previous training we have different knots in our task list. For example in Wildland fire class, we used the water knot, various hitches etc.

Thanks for the good tips :)

Dan_Lehman

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Re: Versatackle ABOK CrossRef#
« Reply #19 on: May 24, 2012, 05:51:07 AM »
Quote
So in attached image I made a 2 inline fig8 bend. It would seem to me this would enhance security a great deal, what say you?

//

A better, more elegant knot is one Fig 8 Bend backed up with Strangle knots on each side

Firstly, please observe that there are two distinct "fig.8"
knot-dressings shown in the two images above --and the
URLink'd one is slightly different in its exact dressing from
the asymmetric one of the pair shown embedded above!
--this so-"easy-to-recognize-that-it's-tied-correctly" knot!!
(And, of the embedded pair of knots, we can't tell which
ends --upper & lower-- are (to be) loaded, which ... tails.)

It would be a worthwhile research project to study various
user who tie "fig.8"s both "re-threaded" & "in the bight"
to see if they end up with the same dressed knot --or not.
(As we see in the examples above, we got botched fig.8s,
by one tying method and even with one tyer!)

As far as elegance is concerned, to my mind the "twin
fig.8 knots"
end-2-end knot has the edge --not much
to simply tying off tails, esp. at such remove from the
base knot (which might be an un-re-tucked thief knot
(pointing out that the fig.8 end-2-end knot can be seen
as a further tucking ... !), and then some tension would be
brought to the strangles).

Note that, in making a "twin" <eyeknot> end-2-end joint,
the loading in the two eyeknot components (which might be
different --not sure how this will affect the elegance quotient   ;D )
will be that of, well, eyeknots, not end-2-end knots.
Here, i.p., there will be the loading on both end-most collars
and so possibly easier untying; possibly greater strength, too.
(But, oddly, in one shade-tree tester's set of results, where
in each test specimen he tied competing end-2-end knots
and then the specimen's ends were tied in fig.8 eyeknots,
(a) the eyeknots never broke/failed; and the
(b) twin fig.8 knots end-2-end knot wasn't as strong
as some others!?  (I.e., it is essentially two eyeknots and yet
it did break, but never did the equal eyeknots of the
specimens' ends break!?  --might point to Knot4U's doubts
about setting with equal tension (or there might have been
some differences; w/o examination of the actuals I cannot
say (though I vaguely recall raising this point and there
didn't seem to be a good answer)).)

Further, as to "this would enhance security a great deal",
in order for there to be a great deal of that, there must be
a great deal to do!  Given that the fig.8 end-2-end knot
is not known to be a security risk, it's arguable that one
cannot make a great deal of improvement.  (And a similar
point can be seen in some cases of strength : given some
85% strength efficiency, how much better can it be?!)


--dl*
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firebight

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Re: Versatackle ABOK CrossRef#
« Reply #20 on: May 25, 2012, 02:23:34 AM »
Well since you learned me :) I been thinking about security. I do realize adding a second knot will not increase strength. An 80% knot with another 80% knot is still 80%

But thanks for your detail.

firebight

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Re: Versatackle Experiment
« Reply #21 on: May 25, 2012, 02:45:15 AM »
Not to dredge up this old argument, and I don't wish to start a new one. Out of curiosity I decided to test the MA for giggles. So I rigged up the "2:1" configuration using strictly rope.

Setup Exp 1.
Two 3.5 lbs (7 lbs) on load side.
I then added one 3.5 pound weight on the force end. (No movement of the load)
I added incremental weight until force overcame load.
I ended up using 6 pounds for a MA of 1.16

Setup Exp 2.
Same setup as above but added carabiners to reduce friction (See attached photo).
This time adding 3.5 lbs on the force end lifted the load end moved slow but it did move. So I would say 2:1



Dan_Lehman

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Re: Versatackle ABOK CrossRef#
« Reply #22 on: May 25, 2012, 06:02:16 AM »
Well since you learned me :) I been thinking about security.
I do realize adding a second knot will not increase strength.
An 80% knot with another 80% knot is still 80%

But thanks for your detail.

You're right about the adding of knots --the weakest link
is the determinant, not some sum of strengths/reductions.

But you didn't really "add a 2nd knot" to the presumed
basis of a fig.8 end-2-end knot : you changed
the knot to a fig.8 eyeknot (in effect/structure), of which
there are two, efficiently sharing eye legs.  And THAT might
just win you strength over the (single) end-2-end knot.

 - - - - - -

Good to put actual forces in play to check MA.
But I'm lost on what your structure is --I see
too many ends running out of the frame to
understand what's doing what.

Thanks,
--dl*
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firebight

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Re: Versatackle ABOK CrossRef#
« Reply #23 on: May 25, 2012, 07:31:40 AM »
Okay, The setup was kinda long so to get a clear image I had to stand close. I will redo the setup outside for better lighting and get a full length shot. for all I know my setup was wrong. We will see.

knot4u

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Re: Versatackle ABOK CrossRef#
« Reply #24 on: May 26, 2012, 06:32:07 AM »
Yes, in a regular Trucker Hitch with all rope, MA will be substantially less than 3:1. By the way, note the nominal MA in a regular Trucker Hitch without friction is 3:1. Who knows what the nominal MA is for a Versatackle? Every Versatackle is different.

Anyway, the option of using steel carabiners/sheave/rings is not a desirable option for most applications. If you nearly eliminate the friction by using a steel sheave/carabiner/ring, then you also eliminate the holding force that allows you to take a breath before you tie off.  That's bad and dangerous, as you will quickly discover when you're trying to bear down hard to generate a highly tensioned rope. It's also dangerous when you untie the highly tensioned rope. I imagine eliminating friction is useful mainly in applications where you're pulling something and don't need to tie off the load, like maybe a tug-of-war, lifting a heavy object, etc.

In contrast, the friction that reduces the MA in an all-rope Trucker Hitch is both bad and good. Yes, using all-rope reduces the MA, but the friction also provides a valuable holding force before you can tie off the Trucker Hitch. This valuable holding force is particularly apparent in a Versatackle. The holding force is good friction that outweighs the bad part of the reduced MA.

There are ways to increase the MA in an all-rope Trucker if you must do so for whatever reason.  There is a thread somewhere on this forum directed specifically toward MA in a Trucker Hitch.

I currently have some Trucker Hitches in my garage that have a nominal MA of 9:1. It's kind of like a Trucker Hitch within a Trucker Hitch. Of course, the actual MA is nowhere near 9:1.
« Last Edit: May 27, 2012, 06:06:47 AM by knot4u »

TMCD

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Re: Versatackle ABOK CrossRef#
« Reply #25 on: May 26, 2012, 04:49:27 PM »
I wonder how much more MA is generated when you loop the working end twice through the Trucker Hitch's center knot? I've noticed by tying the TH in this manner, you get much more tension and tightening of the whole system. It's very easy to tie off the final half hitches too, much easier than if you just took the WE through the center knot once, which is the traditional way of tying the TH. This manner of tying the TH seems similar to a Versatackle in some ways.

knot4u

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Re: Versatackle ABOK CrossRef#
« Reply #26 on: May 26, 2012, 07:51:48 PM »
I wonder how much more MA is generated when you loop the working end twice through the Trucker Hitch's center knot? I've noticed by tying the TH in this manner, you get much more tension and tightening of the whole system. It's very easy to tie off the final half hitches too, much easier than if you just took the WE through the center knot once, which is the traditional way of tying the TH. This manner of tying the TH seems similar to a Versatackle in some ways.

That's a 5:1 nominal MA if you pull around the second anchor twice and through the loop twice. That's up from nominal 3:1 MA. Also, pulling around the loop the second time forms a nip with the first segment of rope passing through the loop. That nip provides the extra friction that allows the easier tie off. So, this configuration provides more MA and more friction for tie off. It's great if you have the extra rope and need to crank down hard on the tension. I call this configuration the Lazy Versatackle.

Again, the nominal MA is for identification purposes only. The actual MA is always less because you cannot eliminate 100% of the friction.
« Last Edit: May 26, 2012, 07:55:34 PM by knot4u »

knot4u

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Re: Versatackle ABOK CrossRef#
« Reply #27 on: May 28, 2012, 07:50:34 PM »

Dan_Lehman

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Re: Versatackle ABOK CrossRef#
« Reply #28 on: May 29, 2012, 02:23:42 AM »
I wonder how much more MA is generated when you loop the working end twice through the Trucker Hitch's center knot?

Use some weights and find out (even to just witnessing the
"moves" / "doesn't move" differences between different weights,
w/o being able to get more precise about where the tipping point
and probable actual MA is) --it can be an eye-opening experience!
(Report your results : open many eyes.)


 :)