Author Topic: square knot or double sheet bend?  (Read 13168 times)

edt71

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square knot or double sheet bend?
« on: October 20, 2014, 06:50:56 AM »
Guys, Ive recently obtained a rigging job in a local shipyard in the U.S. But for some strange reason they use a square knots to tie two ropes together with half hitches at the ends in case it slips. I found this unacceptable since Ive learned square knots shouldn't be used with heavy loads.

So I showed them instead to use a a double sheet bend as a quick way to join two ropes of similar sizes. (since of course there are other more secure ways to do so) Nope, they didnt trust me and thought I was crazy.

So I post my question here since I cant find definite answers on the internet and several pages have different views.


roo

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Re: square knot or double sheet bend?
« Reply #1 on: October 20, 2014, 03:29:56 PM »
Guys, Ive recently obtained a rigging job in a local shipyard in the U.S. But for some strange reason they use a square knots to tie two ropes together with half hitches at the ends in case it slips. I found this unacceptable since Ive learned square knots shouldn't be used with heavy loads.

So I showed them instead to use a a double sheet bend as a quick way to join two ropes of similar sizes. (since of course there are other more secure ways to do so) Nope, they didnt trust me and thought I was crazy.

So I post my question here since I cant find definite answers on the internet and several pages have different views.
So they seem to already recognize the problems with a reef knot as a bend or they wouldn't be throwing on added layers. 

I'd recommend a Zeppelin Bend:

http://notableknotindex.webs.com/Zeppelin.html

It'll save them time and mess and it's more secure.  But don't just tell them that it's more secure, show them.  Tie both type of knots in front of them in the stiffest or slickest rope you use and shake/flog each to show the difference in time for things to spring apart and come undone.

Showing results in dissimilar rope sizes and materials may also be instructive.
« Last Edit: October 20, 2014, 11:16:10 PM by roo »
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Twine

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Re: square knot or double sheet bend?
« Reply #2 on: October 21, 2014, 04:01:15 PM »
I agree with Roo, it would be ideal if they would use the Zeppelin bend, but since those riggers apparently have trouble learning or understanding even a double sheet bend, I guess they can't easily be convinced to learn the more complicated Zeppelin bend. Perhaps they could learn to make a double harness bend (with opposite or parallel ends, Ashley #1420, 1421). The double harness bend looks superficially a bit like a reef knot (small, sort of square) so it wouldn't look too scary to them. It's easy to make, too. The version depicted and discussed by Xarax as the "short" Double Harness bend in his post http://igkt.net/sm/index.php?topic=2851.msg17097 seems (to me) to be easier to untie than the "long" one.
« Last Edit: October 23, 2014, 12:19:24 AM by Twine »
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KenY

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Re: square knot or double sheet bend?
« Reply #3 on: October 21, 2014, 06:28:59 PM »
Just keep it simple, it may be useful to point out to the rest of the world this knot is named the Reef Knot, and reefs could be shook off with one hand .

I am sure if 9year old  Cub Scouts can learn a sheet-bend, you can re-train a professional rigger..KISS


KenY

edt71

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Re: square knot or double sheet bend?
« Reply #4 on: October 21, 2014, 07:45:26 PM »
Yeah I had read the earlier post on the the double sheet bend and was quite interested on the posters stronger method of it (which now I tie for better security) compared to the traditional "Ashleys book of knots" version. I did also read about "Roo's" post on how the zeppelin knot is more secure.

Believe me, I started practicing it right after reading it. From what some other websights mention it can take alot of weight as the other bends but has the uncanny ability to untie easier. Its a bit harder to tie but with practice maybe one day I can out tie myself with the double sheetbend. (have been using the sheetbend for years)

Yeah this yard Im are full of guys x U.S. navy boatswain mates and anything I say they just seem to throw out the window. Most of them are simply stuck they learned in their previous carreers. And usually they only know a few of the practical knots. Some others being more skilled at it, while others dont seem to have a clue. But, their basic knots to know mostly are the reef knot, the bowline, and the clove hitch. It just shocks me that they know so little. But then again, due to our countries newer safety laws ropes are slowly being illegalized during heavy lifting and require tested slings and shackles. ropes are simply now used for taglines and to secure something to a pallet to be craned off.

Twine

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Re: square knot or double sheet bend?
« Reply #5 on: October 22, 2014, 09:45:32 AM »
Hi edt71
If your workmates already know the bowline, then things are looking better already. I was going to suggest that you find another job, because sooner or later an accident will happen where people use the reef knot to bend ropes together.

(EDIT: I now - after some primitive testing - think that it may actually be safe for its purpose when it is secured as you describe, see my answer to enhaut http://igkt.net/sm/index.php?topic=5075.msg33465#msg33465 )

Instead, making two interlocking bowlines is really easy, it holds much better than a reef knot, it is quick to make and unmake, and it is more practical, because you only need to untie one of the bowlines to release the ropes, and on the other rope you then still have a loop, which may or may not come in handy for some other purpose, like a handle for pulling on the rope or something. Only drawback I can see is that two bowlines consume more rope than the reef knot you describe.

Such interlocking bowlines were often used without problems by sailors in the days of hemp and manilla. In modern synthetic rope I think it would be wise to secure the tails somehow to prevent slipping.
« Last Edit: October 23, 2014, 12:27:29 AM by Twine »
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enhaut

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Re: square knot or double sheet bend?
« Reply #6 on: October 22, 2014, 06:05:56 PM »
Ashley's point of view is interesting (read below).

If your coworkers are happy with the bend they prefer dont bother to show them another solution, but you should benefit from learning the Zeppelin, learn it and then try  the slipped version it's fun to play with an easier to untie.

Sweeney

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Re: square knot or double sheet bend?
« Reply #7 on: October 22, 2014, 09:28:32 PM »
A reef knot can also be made secure (and more elegant) by tucking the ends down through the centre with the knot lying flat - the result is the same as Solomon Bar but using the ends of the reef knot rather than separate lazy strands. This can be difficult to undo after heavy load though.

Barry

Dan_Lehman

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Re: square knot or double sheet bend?
« Reply #8 on: October 22, 2014, 11:34:37 PM »
Guys, Ive recently obtained a rigging job in a local shipyard in the U.S..
 But for some strange reason they use a square knots to tie two ropes together
with half hitches at the ends in case it slips.
Please say where this is (at least in general terms for regional
and historical aspects).  It is useful/informative to get
reports from actual practice (vs. speculations from arm-chair
readers).  It's quite surprising that there should be such
knotting in a shipyard.  What sort of rigging work is done
(and so on)?  What other knots are employed?

Quote
I found this unacceptable since Ive learned square knots shouldn't be used with heavy loads.
There are various reasons to prefer some other end-2-end
knot (and not to pretend that this, too, isn't such a knot!),
and sometimes reason enough to use this (typically with
ends secured in some manner --it is maybe the trimmest
end-2-end knot).

What applications are being done with this reef knot?
What sorts of materials ... ?!
(Do folks ever expect to untie the knot? --and can they?)

Quote
So I showed them instead to use a a
Quote
double sheet bend
as a quick way to join two ropes of similar sizes.
And even not-so-similar sizes/natures
(size might not be the only influential factor).

But let me suggest a better though similar alternative,
what I call the "double Lapp bend" :
regard the single sheet bend --ends on same side--
when loaded in reverse (i.e., by the tails)
as a single Lapp bend;
to "double" it, take the *hitching* tail (this is the
one making the loop, not the U/bight) around its
own S.Part again and back down through the bight (U)
again --this, to secure it; and this step can be repeated,
for a "triple" such knot, as might be desirable given
some circumstances.

Why this ... ?
Because this wrapping of the one tail will secure the
knot when unloaded, against loosening (if set well),
whereas the sheet bend might never get tightly
set (OTOH, it can jam with heavy loading --YMMV).

To loosen and untie the dbl. Lapp bend,
pull the tail of the U-part (bight) away from its S.Part
(to prise out some of the hitching S.Part), and then
you should be able to work it further loose.
(I will not presume such forcible loosening to be
possible always; and it might be something needing
mechanical help for force, where large forces are
involved.


--dl*
====

Twine

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Re: square knot or double sheet bend?
« Reply #9 on: October 22, 2014, 11:47:19 PM »
Hi enhaut!
I was surprised by your opinion that they should just keep on using the reef knot (secured with halfhitches).

Ashley's point of view is interesting (read below).

If your coworkers are happy with the bend they prefer dont bother to show them another solution, but you should benefit from learning the Zeppelin, learn it and then try  the slipped version it's fun to play with an easier to untie.

Well, I looked up in ABOK the sheet knot you depicted, and there I saw that Ashley has considered the very same knot as edt71's workmates use, and it is his #1404. He apparently considers it safe, but I couldn't accept that, since it was just an expert opinion and not my own experience.

So what I did next was to tie this tagline bend (if I may call it that) and subject it to what I figured would be a quick and dirty simulation of what happens in the long run if it is used in a tagline: The bend will be subject to jerks from both ends, but not smashed into the ground or dragged across edges or things like that. So by way of simulating this, I jerked my tied rope by hand 600 times, and the bend actually held very well, to my disappointment.

Then I thought that surely a softer and more slippery rope would have come undone, and did the same test with such a rope. This time one of the halfhitches came undone (I had on purpose tied the knot with very short tails) after 250 jerks.

"Aha", I said to myself, "now it will be just a matter of seconds before the entire knot slips or comes undone", but no. After 500 more jerks it still held even though there was only ONE half-hitch left to secure the tail. That half-hitch had sort of wedged itself into the reef knot and integrated with it. For some reason this completely stopped all slip.

Later I did a more severe test, tying the knot between two iron bars (to get more power into the jerks and to protect my fingers), repeatedly jerking the heavy bars apart. Turned out that the tagline bend slipped LESS than the single-tucked double sheetbend. So okay, I have to admit that the knot seems to be much more secure than I first thought, at least for the purpose of tying taglines together. I'm sorry hat I ever doubted the professionalism of those riggers.  :-[

Well, at least I came up with a method of testing that I found easier and more efficient than just using my hands. I'm sure I will use it more in the future. Maybe someone else can have some use for it. Instead of steel bars I would have used two large marlingspikes if I had any.
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roo

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Re: square knot or double sheet bend?
« Reply #10 on: October 23, 2014, 12:18:13 AM »
Later I did a more severe test, tying the knot between two iron bars (to get more power into the jerks and to protect my fingers), repeatedly jerking the heavy bars apart.
A more severe test would to be use more shaking motion, NOT more force and not jerking.  When you use heavy force, it can tighten up the knot and prevent loosening.  Light and lively will  usually cause a given knot more problems.  Think wind flogging.
« Last Edit: October 23, 2014, 12:23:34 AM by roo »
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Twine

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Re: square knot or double sheet bend?
« Reply #11 on: October 23, 2014, 12:38:53 AM »
A more severe test would to be use more shaking motion, NOT more force and not jerking.  When you use heavy force, it can tighten up the knot and prevent loosening.  Light and lively will  usually cause a given knot more problems.  Think wind flogging.

You're absolutely right, and I should have said that shaking was the first thing I tried but that didn't seem to do anything at all, no matter how vigorously I shook the rope, so I decided to stop that and test for slippage instead. I didn't bother to shake test the soft and slippery rope. I guess I will have to try that too. Maybe that kind of vigorous shake test should better be done by some sort of machine.
« Last Edit: October 23, 2014, 12:41:58 AM by Twine »
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enhaut

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Re: square knot or double sheet bend?
« Reply #12 on: October 23, 2014, 01:48:02 AM »
Hi Twine,
You did some tests! Wow! I would never have the patient to go further than
50 jerks.
Maybe Ashley had a mistress on a third floor somewhere and he had this bend in mind for an urgent escape in case of...(kidding)
As Roo point out there are other ways to treat a knot.
Given the time you spend on that bend I pretend that you would be a very good knot beta tester.

[Inkanyezi] gone

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Re: square knot or double sheet bend?
« Reply #13 on: October 23, 2014, 12:57:03 PM »
A bit to my chagrin, knotting has been prohibited here for decades after a deadly accident with a knot involved. Even though the work security board never assessed what the knot might actually have been, the story was that "someone must have tied a granny instead of the square knot".

I never tried to find out which one of the two is less secure for that application. The accident was with a concrete building element, where the elements were supplied with short rope slings tied through holes, and hooks applied to those slings. One knot capsised and the concrete wall element weighing about 350 kg came loose at one end, fell and killed a worker.

From then on, I think it was in the sixties, knots are prohibited for any type of lifting. Only approved slings may be used, and the sling must be attached in an approved way, hooked, cow hitched or run through an eye and both ends hooked.

It seems as there is good reason for that regulation.
« Last Edit: October 23, 2014, 01:15:04 PM by Inkanyezi »
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edt71

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Re: square knot or double sheet bend?
« Reply #14 on: October 24, 2014, 07:43:43 PM »
Well the shipyard in mind is in the U.S. in the state of Virginia. Its owned by quite a large U.K. company. (and now they own about 70% of all American shipyards) Some of you here may already know the name, but I will not personally name it here in case management in my shop suddenly happenstance to run across this thread.

But yes, the shops riggers tend to use the reef knot with two half hitches to tie up two lines together. Im not sure why they use it so much. One of the older riggers mentioned that its easy to remember and some of the newer recruits, are not so savvy in knots and this is one of the knots taught to them. They mostly use this because there are times on the job their isnt enough rope for a job and no one wants to run down the dry dock (about 80 steps) then run all the way to the shop to simply get 6 foot of rope. They simply scour the ship or other work areas for rope.

As a new recruit myself Im not quite sure what they call the rope, but its brown and not the natural version. I think they call it "polypropylene manila rope" the most common size our shop seems to use for everything is about 1 inch.

They use if for everything and can be found everywhere in the yard and other shops rely on it for other things. Mind you its illegal to use as a direct load bearing line here. As one of the posters mentioned, people have died over specific ropes being used to hold up large amounts of weights. 1. because of the knot the last poster mentioned, 2. rope lines can be cut accidentally.

We mostly use different size wires for holding up heavier applications. The ropes are for securing smaller things, tying down items on pallets being moved by forklift or crane, roping off areas where a person may fall down off the ship, tying a tagline onto the item being craned off. etc. etc.

However I will say there are those times when one needs to bend the rules a bit (ehhhh hemmm!) We couldnt get a beam clamp (somewhere on a ship) to chain fall an item being moved from within the ship to the upper deck so it could get craned off. The rigger in question rigged up a small section, of the same rope mentioned, into some holes within the upper beams. He then tied the ends together with a reef knot and half hitches to secure it. Then he put the chainfall on the rope and we proceeded to chainfall the object out the next level (it was coming up the stair well to another level) The object in mind was about 200kg and the rope did not break or unloosen.

The knot apparently does work, but personally I just use a double sheet bend because its so much faster to do it. And because its a knot, and not a bend. Maybe its me because what I have always learned as a kid was reef knots are just not secure enough.
« Last Edit: October 25, 2014, 08:48:01 AM by edt71 »