International Guild of Knot Tyers Forum

General => Practical Knots => Topic started by: Lhillgamer on April 20, 2016, 08:34:16 PM

Title: Which way is the true sheet bend?
Post by: Lhillgamer on April 20, 2016, 08:34:16 PM
I recently have noticed many people tie the "sheet bend" this other way that i have never seen before. So my question is which one is the sheet bend, and if the other one is a sheet bend as well, or a completely seperate knot, and if it is a seperate knot, what is the name and/or ABOK #?
Thanks, Lhillgamer
P.S. Sorry the images are bad
(https://marinemax.files.wordpress.com/2014/09/sheet-bend-full.png)
(http://www.paracordguild.com/wp-content/uploads/2014/10/sheet-bend-1024x545.jpg)
Title: Re: Which way is the true sheet bend?
Post by: knotsaver on April 21, 2016, 11:22:02 AM
Hi Lhillgamer and welcome,
have you got a copy of the ABoK?  because the Sheet Bend is #1 !  ;)
However you can find it (/them) again at #66 and #67, #485, #490, #492... #1431, #1432...
Your second picture (bottom) is a (Right-Hand) Sheet Bend (#1431) (the tails are on the same side = the "true" Sheet Bend), whilst the sequence showed in your first picture (up) is for a Left-Hand Sheet Bend (#1432, tails on opposite sides) that (as Ashley said) "is not so reliable a knot as #1431" (the Right-Hand Sheet Bend).
Have a look also at
http://igkt.net/sm/index.php?topic=3117.msg18597#msg18597
--
Ciao,
s.


Title: Re: Which way is the true sheet bend?
Post by: Lhillgamer on April 21, 2016, 04:47:18 PM
Thank you very much, and yes, i am an owner of a copy of the ABOK and i did see that the sheet bend was #1 right after i posted, (i felt dumb), but i still was wondering what he other knot was, so i decided to not take it down. either way, Thank you!
Title: Re: Which way is the true sheet bend?
Post by: Dan_Lehman on April 24, 2016, 07:21:59 PM
I recall that Rob Chisnall --one-time IGKT Pres., & rockclimber--
did some testing (of a casual sort, IIRC) of the two forms and
found that there was some variance in which performed better;
possibly, had his testing run to rupture (I think it did not), he'd
have had different results?  (And alas we can only guess which
form was used in the Dave Richards tests of a trio of kernmantle
ropes (12.7mm low-elongation, 10.5mm dynamic, 7mm low-elon-
gation), in which he saw all, IIRC, slip at significant loads).)

NB : taking your red-&-blue cordage knot in reverse (i.e., load the
tails/short-ends)
yields the Lapp bend.  What is currently in my
favor is what I'll call a "double Lapp bend" in which the (as above)
red tail (here, the long one, upon the reversal stated) around one
--or 2, 3-- more time(s)
(around its own SPart and the side of the U
lying beside it) gives a knot that is much more secure-when-slack
and perhaps even stronger (unlikely to be or matter much).

It's able to be forcibly loosened by pulling the ends (SPart & tail
of the U-part apart, just enough to pry out a little of the SPart
which nips them, and to then work further loose the knot
--YMMV w/materials & force, but at least in small stuff for
simple tasks, this loosening method works.  (It only needs
to pull a part that though maybe tightly gripped by the
wraps around it runs straight beneath them and
so can move, not having to overcome any deflection.)


Recall that allegedly the sheet bend was the name used
for a knot that tied the "sheet" --a rope (no, a "LINE" !)--
to an object --a "clew", roundish or pear-shaped,
semi-flexible or firmer!?  --which in pure cordage would be
better matched by tying ("hitching" we might prefer to say)
to an eye --both legs of U-part being loaded.
(Incidentally, when hitching in the dbl. Lapp bend way to an eye,
I might try to orient the eye legs so that the one taking the
hard initial nip of the hitching line is a little more slack and
so can shift a bit from pure parallel form to its partner leg,
matching how the tail of a single line will be pulled in this
knot, which I think gives a preferable geometry!?)


--dl*
====
Title: Re: Which way is the true sheet bend?
Post by: KC on August 08, 2016, 11:45:56 AM
Left-Hand/ ends on opposite sides:
The hardest Nip/hardest rope pressures don't trap the Bitter End of the Bight side only the Hitch side with most intense pressures.
.
In the Sheet Bend shown as proper / ends on same side:
The trapping mechanism of the Nip of pinching pressures to hard tightened line;
DOES trap thru both Bitter Ends of both the Bight and Hitch sides
.
If look at last of 4 drawings:
See pulling the ends to set, traps hard only the Bitter End of Hitch leg;
>>Any trapping Nip to Bitter End of Bight leg is residual, not tightest pressure nor hardest rope section to nip/'pinch' with
But looking at photo picture:
Blue and Red Standing Tension Parts, sandwich both Bitter Ends together with highest tensions/hardest part of lines
.
?
i thought Dr. Cyrus Day argued this, and said 'Left' was right; or at least equal.
i thought he favored Left version, and in fact differentiated it from Weaver's Bend,
that he noted Weaver's worked better in some/smaller materials;
AND gave a finished side for tailors to present
i don't have "The Art of Knotting and Splicing"/Naval Institute anymore, but thought i had read this arguement.
(figured in knubby, Natural rope/hairy 3 strand was 1 reason)
.
Make a Round Turn around (only really need to trap end 1x) neutralizes arguement.
Extend to Simple Simon Over (at least 1 over); even better and cleaner package/ no right angle sore thumb pieces.
Title: Re: Which way is the true sheet bend?
Post by: bj on August 08, 2016, 04:11:24 PM
Day says the opposite side version is inferior, but also has a paragraph talking about  E.D. Fowle's (from 'Textile World, 21-May-1927, pp. 96-99) statement about the opposite side being preferred because it blends with the fabric better.
Title: Re: Which way is the true sheet bend?
Post by: KC on August 12, 2016, 11:46:25 PM
Thanx,
.
Tried to draw this out again
.
(http://mytreelessons.com/images/sheet_nip_1.png)
.
(http://mytreelessons.com/images/sheet_nip_2.png)
Title: Re: Which way is the true sheet bend?
Post by: Dan_Lehman on August 18, 2016, 08:43:36 PM
Let me register here a note that the above post's
implication that sheet-bend mechanics transfer (well)
into those of the bowline is not right --not in full,
at least : the *loop* part of the latter knot is loaded
on both ends (100% vs. 50%, SPart vs. eye leg).

--dl*
====
Title: Re: Which way is the true sheet bend?
Post by: KC on August 19, 2016, 10:54:43 AM
Thanx,
In the drawings i try to show this with the arrows showing force patterns;
single bottom arrow on Sheet Bends, but double arrows / half force each side of eye for Bowlines.
.
Thus in Sheet Bend, each side is tensioned same AND just as stiff/hard from said tension.
Bowline however, has the S_Part leg as single, most loaded ; because eye pulls are divided.
So, target becomes how to Nip the Bitter End into this hardest pushing back surface;
>>tail outside misses getting sandwiched into this target.
.
Just as in Square Knot, HH w/Better Nip etc. need HARD convex preferred surface to Nip against;
Here in free floating knot w/o host that hitch would Nip against, lacing must provide it's own HARD surface is key.
.
In either mechanic, the hitch side tries to trap the bight side that is trying to escape.
In the Bowline, there is only half as much force on the escape/ bight side; but full force on trap hitch side.
(other half of line for eye is securing hitch side; property that Sheet Bend doesn't have)
Title: Re: Which way is the true sheet bend?
Post by: agent_smith on September 06, 2016, 08:54:06 AM
For an in-depth treatment of Bowlines, nipping loops and the Sheet bend, go here: http://www.paci.com.au/knots.php
Click on item #2 in the table (Bowlines Analysis).

Its still freely available in the public domain... :)

I had posited that cable grip orientation on steel wire rope cable is a useful analogy for the behavior of different tail positions in a Sheet Bend (although not published in the Bowlines paper). It is something I am still investigating...

Mark G
Title: Re: Which way is the true sheet bend?
Post by: Dan_Lehman on September 07, 2016, 09:56:55 PM
I had posited that cable grip orientation on steel wire rope cable is a useful analogy for the behavior of different tail positions in a Sheet Bend (although not published in the Bowlines paper). It is something I am still investigating...

With what rationale(s) --for the recommended cable clamping,
and its relevance to the eye knot?

--dl*
====
Title: Re: Which way is the true sheet bend?
Post by: Groundline on September 07, 2016, 11:24:35 PM
I think he's referring to the fact that the end will work its way loose if the knot or cable clamp is tied (applied) backhandedly.
Title: Re: Which way is the true sheet bend?
Post by: agent_smith on September 08, 2016, 02:17:25 AM
Quote
With what rationale(s) --for the recommended cable clamping,
and its relevance to the eye knot?

What eye knot?

A Sheet bend isn't an 'eye' knot. Unless you were thinking of a 'Becket' perhaps?

Security is thought to be improved in one orientation of the Sheet bend versus the other (ie #1431 v #1432).

As far as I know, there doesn't appear to be an in-depth paper describing/explaining why one orientation is more secure than the other. Such a paper might exist...but I have yet to find it. No doubt, someone in the IGKT will know if an in-depth treatment of the Sheet Bend has been done (in a published paper).

Obviously, the material that the rope is constructed from will play an important role (eg vegetable fibre versus modern synthetic lifelines)...including the effect of a 'hawser' / twisted lay of the rope.

I decided not to publish the cable-grip analogy in the Bowlines paper because I had difficulty with developing a theory to link the two systems.

On steel wire rope, the cable-grips are oriented so that the 'saddle' lies on the SPart (or 'live' end of the cable). The 'U' bolt lies on the tail.

In a #1431 Sheet Bend, the SPart of one rope is oriented so that it clamps/crushes the 'tail' of the other (opposite) rope.

This appeared counter-intuitive to me when trying to develop a rationale for why cable-grips must oriented as such...and why a Sheet bend allegedly is more secure when the SPart of one rope initially contacts and crushes/traps the tail of the opposite rope. There is more going on here (obviously) - because one rope is actually trapping and crushing its own tail.

Anyway, this has been something that I have been thinking about for some time - but could not correlate my thoughts sufficiently well - so i did not advance it further.


Mark G
Title: Re: Which way is the true sheet bend?
Post by: KC on September 08, 2016, 11:08:21 AM
Bowline paper very nice rite down to color choice!
.
in my imagery i think there are 3 force parts in Bowline to watch for, to see Left Hand doesn't Nip as well.
.
i see these things as electrical schematics;
and blurring it more see, whether positive/negative, north/south, male/female etc.
Yin/Yang the Equal/Opposites seek each other;
in Left Hand Bowline, the Bitter End is not in the force path between the Equal/Opposites;
so doesn't incur their direct forces, only residual/side forces.
.
The S_Part is key in tension and thus hardness;
to trap into it, Bitter End needs to turn towards, not away from S_Part.
.
Even in Sheet Bend, theory carries; even though 2 Bitter Ends now.
The Cross Over Loop/Hitch is the lock, the Bight is trying to escape.
The lock side Bitter End can't help but be in force path;
It must end up on top of it's own S_Part, that bight S_Part seeks (so gets Nipped between).
Bight side Bitter End lays next to it's own S_Part, not crossed over  it;
whether Bight side Bitter End gets good Nip depends:
on if it lines up to the side of it's S_Part that sandwiches it properly
between the 2 Equal/Opposite forces seeking each other (or not).
So, Bight Bitter End must again end up towards, not away from lock/hitch side S_Part for best Nip.
(http://mytreelessons.com/images/bowline_3parts.png)
(full size) (http://mytreelessons.com/images/bowline_3parts.png)
Title: Re: Which way is the true sheet bend?
Post by: agent_smith on September 09, 2016, 05:00:43 AM
Quote
Left Hand (Bowline) doesn't Nip as well.

Is this something you have tested and proved?

The term 'left-hand Bowline' is problematic - in consideration of handedness / chirality. The nipping loop of a Bowline can be described as being left hand (S twist) or right hand (Z twist)... same as a coiled spring - which can be Z or S twist.

I would immediately point out that #1034 1/2 Bowline is in fact more secure when ring loaded.
In contrast, #1010 is insecure in a ring loading profile.

Tail orientation in a Bowline is - in my view - not a primary factor for measuring security of the common Bowline in a straight line axial loading.

...

In terms of a Sheet bend (which isn't an eye knot) - I had posited that there is no nipping loop - and therefore, the way it functions is different to a Bowline.
Derek had posited that Bowlines have an 'SB core' (sheet bend core) - and he discussed this at length with diagrams in the Bowlines definition thread.
However, I think the definition of a nipping loop has been tightened, and as such, the core of a Sheet bend does not function in the same way as the core of a common (#1010) Bowline. There are similarities - but the nipping loop is key to the Bowline structure - and is missing from a Sheet bend.

Modern synthetic fibre 'kernmantel' ropes also behave differently compared to hawser lay vegetable fibre ropes. Mountaineers in the 1950's routinely used the common bowline as a 'tie-in' knot to their body (pre-harness era) - the ropes were of a hawser construction and vegetable fibre. Modern climbers who use synthetic fibre kernmantel ropes must modify the common Bowline with tail maneuvers to render it secure. I think the Sheet bend is also affected by rope type.

Mark G
Title: Re: Which way is the true sheet bend?
Post by: KC on September 09, 2016, 09:40:29 AM
Is this something you have tested and prove 

No sir; i'm sorry  this is simply what i've always seen handling it and making sense out of lessons handed down.
This is why i didn't reply at first here or other places.
i always thought and felt, of course 'Leftie' isn't as secure;
it mechanically can't be.
.
Sheet Bend doesn't have the Nipping Loop - pulled from what would be the eye side
BUT, same loop would be pulled from it's S_Part;
but any way it doesn't seem to be the side trying to walk off the job;
As it forms a Hitch, it's Bitter End is sitting on one of the hardest surfaces to Nip proper.
Bight side seems the escape side,  not forming a Hitch lock/ not crossing turn nipped by self.
.
To me, they are visually similar, forces do run different loading patterns ;
but still just as the look similar, each has an escape side, and a lock side;
and depends on line tension and hard surfaces as Nipping tools, like any other.
.
So i think, to Nip against the hardest surface, Bitter End of escape/Bight side
must follow into hardest S_Part line
As GREEN Bitter End seats to BLUE S_Part
But, PURPLE Bitter End evades this hardest Nip, by turning away from it.
.
Orange side of eye forms a Hitch on own,
Green side of eye forms Bight w/o hitch, so is focus of trying to 'nail down'.
My eye simply doesn't expect as much Nip on leftie, tried to reveal this with the colors.
Title: Re: Which way is the true sheet bend?
Post by: Dan_Lehman on September 10, 2016, 04:17:10 PM
Quote
With what rationale(s) --for the recommended cable clamping,
and its relevance to the eye knot?

What eye knot?
Ah, the one made w/cables, and your mention of the
*bowlines* paper.

In any case, IMO the (never stated?!) rationale for the recommended
clamp the U-bolt-into-cable-TAIL orientation is that the U-bolt
will physically deform the material somewhat, will grip it thus
more tightly & harmfully, and so it's best to leave the SPart
running between tail & broad base of the clamp --and any
slippage will be of SPart slightly out of this until clamp
nearest eye abuts the eye/object and we'll hope then
that slippage is arrested.
(Note that the quoted source above mentions "strength"
vs. security, so my musing about slippage is probably
much into fantasy.)

In tying the multiple Lapp bend, I do find it best that
the "hitching" line run around to nip hard/first into
the tail; it slips more readily otherwise.


--dl*
====
Title: Re: Which way is the true sheet bend?
Post by: KC on September 14, 2016, 12:46:25 PM
theories:
ropeClamp rule of thumb:
If U bolt is on S_Part side / before frictions around eye, can drop efficiency 40%.
So i always remember 'saddle to solid'.
.
Once again 'pure inline' mantra of not deforming the single loaded leg S_Part for most strength;
(besides next step of providing another leg of support for load sharing)
and Nip  after frictions, on hardest surface, with greatest force for most security.
(usually giving deformity to bury in lacing for most inline support).
.
Cable like rope is maid to be loaded only on the inline axis, and only in tension direction.
(inline axis is the major axis of a device{log, rope, etc.),
whereby forces on inline axis only can leverage across the short axis/minimal
>>cross-axis would be narrow axis across length of device, allowing major axis to then be leverage-able.
>>only across center of perfect circle, would present no axis more leverage-able than other axis)
lines(cable/rope/chain) only have so much tensile, and only support load on inline axis
>>any cross axis/deformations from inline leverage load force higher in line,
>>leaving less usable tensile to support 'nominal' load.
.
But,
The stiffer line placed into rope model, the more sensitive to any deflection from inline.
Thus, cable is most sensitive to breaking/bending 'pure inline' mantra.
Cable even takes larger diameter pulleys for same diameter line, and sheave specially shaped to support 'belly' of cable.
All, because cable is stiffer than rope, so is more leverage-able on cross-axis, to raise tension in line more,
>>to ultimately leave less of line/cable absolute tensile strength remaining;
>> for the relative tensile strength (inline) to support/resist load