Author Topic: Important Double Sheet Bend query  (Read 19788 times)

Seaworthy

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Re: Important Double Sheet Bend query
« Reply #15 on: June 18, 2014, 05:15:06 PM »
Seaworthy,

If you're looking for a more secure bend, it's probably time to look toward a different bend rather than a different dressing of the double sheet bend.  If, for the sake of argument, your favored dressing is more secure, it's still not that great when compared to the continuum of other bends.  In mismatched line, a snag of the larger rope's free end may destroy the bend! And just to make sure the preferred dressing is made and maintained during tightening, you'll need expert and vigilant eyes.

It comes as a surprise to some, but the sheet bend family can become difficult to untie after hard strain.

For all these reasons, I would like to suggest the use of the Zeppelin Bend, which is more secure, stable, determinant in dressing, is more jam resistant, and better handles differences in line diameter:


Roo that does not help LOL. The best alternative to a DSB is a totally separate issue. The DSB is still being taught and is still in use. Go have a look at the home page here. It is taught to Sea Cadets here.

The Zeppelin has been reported to be not good if the line is of quite different diameter. That is where the DSB is primarily used sailing. The Zeppelin is not a substitute.

roo

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Re: Important Double Sheet Bend query
« Reply #16 on: June 18, 2014, 05:18:02 PM »

The Zeppelin has been reported to be not good if the line is of quite different diameter.
It happens to be an incorrect report.  The Zeppelin Bend is far better with lines of different diameter than any member of the Sheet Bend family.
« Last Edit: June 18, 2014, 05:19:15 PM by roo »
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Seaworthy

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Re: Important Double Sheet Bend query
« Reply #17 on: June 18, 2014, 06:07:34 PM »

The Zeppelin has been reported to be not good if the line is of quite different diameter.
It happens to be an incorrect report.  The Zeppelin Bend is far better with lines of different diameter than any member of the Sheet Bend family.

Any evidence to support this? Who has tested and confirmed this and with what variations in diameter and what type of lines?

roo

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Re: Important Double Sheet Bend query
« Reply #18 on: June 18, 2014, 07:25:21 PM »

The Zeppelin has been reported to be not good if the line is of quite different diameter.
It happens to be an incorrect report.  The Zeppelin Bend is far better with lines of different diameter than any member of the Sheet Bend family.

Any evidence to support this? Who has tested and confirmed this and with what variations in diameter and what type of lines?
You should be able to do this yourself.  It's not a hard test.  Snagging the free end of the larger, U-shaped rope in sheet bend variants is a well-known weakness.

While this issue has been discussed at length in this forum in various places, there's nothing like having a first-hand experience.

ref:
http://igkt.net/sm/index.php?topic=1872.msg12785#msg12785
http://igkt.net/sm/index.php?topic=1872.msg12788#msg12788
« Last Edit: June 18, 2014, 07:44:12 PM by roo »
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Dan_Lehman

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Re: Important Double Sheet Bend query
« Reply #19 on: June 18, 2014, 11:11:08 PM »
THINK about this : substitute "sheet" for "Lapp"!!
After centuries of use, has anyone reported testing
as you ask for this venerable knot,
noting sizes and which side --they're different-- breaks???!
(I know of none, including even myself, say, using
cheaply got mason-/fish-line.  .:.  lazy me!)

Well, I am not aware of load tests, but how these knots function best has certainly been passed down through the years. How much is anecdotal I don't know, but the old salts from years gone by were a canny lot and would have worked out pretty quickly what worked and what didn't.
Perhaps, in some cases, and for some situations
(which might've changed, in time).  Whether the
popular literature captures this knot knowledge
is an entirely separate question --mostly, knot
books seem to copy other knot books, even errors!

Quote
For example, if the lines are of a significantly different diameter, sailors don't use a single sheet bend.

If lines are of a thick diameter, neither the sheet bend nor double sheet bend is preferred, instead a Carrick is used.
Really?
I've never found a carrick bend tied anywhere
in the Wild !  I've heard, well, seen on t.v., that
it is used by the Alaskan crabbers.  The zeppelin
would be good one for them, too, though they might
want to bind the tails (tape) and the former makes
that easier.

Quote
I generally tie an Alpine Butterfly Bend
if I need to join two ropes of roughly the same size.
In the last few days I have practiced the Zeppelin
until I am super comfortable with it and will make that
the knot of choice now.

And you'd use these *fashionable* knots instead
of Ashley's bend #1452 (or 1425!) because ... fad?

Nope, because I have read that the Ashley and Hunter
could not be untied after a load had been applied, so I never
bothered even glancing at them.  Sailors generally prefer to learn
how to tie the minimum number of knots they can get away with :).
I have never come across anyone using the Ashley bend on
board a boat and simply dismissed it as an option.
!!
Pity what misinformation can do --and that you
gave up so easily, rather than testing assertions
(which must've come from the Net).  #1452 can
be dressed to jam or not to jam; Ashley doesn't
illustrate the knot well, and might not have known
it so well, either.  You want to orient the tails so
that they start being rotated against each other
in a locking manner and are further so rotated by
the draw of the SParts.  (Unlike the butterfly bend,
#1452, #1408, & zeppelin have SParts rotating in
the same direction --the b.'s go opposite.)
(The jamming state might be beneficial when working,
e.g., with polypropylene rope in some light-load situation;
w/o heavy loading, you will easily be able to untie.)

Ashley's #1408 & the zeppelin have similar shapes
of their overhands, with the former interlocking
them more fully, but the latter giving more of a
sharp bend to the tail at its tuck, which I think
helps it resist *flowing* loose --material doesn't
move through the right-angle bend well, whereas
#1408 has a smoother bend here.

Quote
So, my question remains.
Is #1434 or #488 going to perform better under load,
particularly when the diameter of the lines is different?
If so, 1434 should be banished from sailors' repertoires :).
You shouldn't be so narrowly Index-to-exact-knot-minded,
but understanding of how the knots work so that
you can make adjustments per situation.
E.g., Roo warns of snagging of the bight-side tail
with the sheet bend-like knots : this vulnerability
can be redressed by essentially seizing the tail to
the SPart with the end of the hitching line,
using a multiple strangle knot (or, if you want
to keep to *fad*, a less-well-oriented vis-a-vis tails
alignment, constrictor  :P ); the first-formed
will do the heavy work, the seizing knot just will
keep things in place, and be no tighter than it
was set, roughly --and thus, loosenable.
[Here I'll remark at how "untiable" is an ambiguous
term --can we NOT tie it, or can we UN-tie it?!]

Frankly, the two previous knot alternatives I suggested
--those using overwraps of either hitching SPart and
one leg of the bight side, or both legs but then
with a more or less normal sheet bend front end,
will provide some *seizing-like* security vs. snagging.
(Of course, the zeppelin is woefully awkward with much
line-diameter difference, and will please only the most
pedantic & z.-zealous of mariners.   ;)  )

Btw, FYI Dave Richards of the Cordage Institute (or of
a member firm --but I believe he was on the board ...)
did testing of kernmantle ropes (rockclimbing, caving,
SAR), and found that sometimes the dbl.S.B. slipped
but not the single (& also the fisherman's knot(!),
sometimes both (resp. 12.5mm & 7mm low-elongation),
and once only the single (dynamic).  So, that was eye-opening!
(No photos to show details, et cetera, so much must be
presumed or left to question.)
((This report was taken off-line, sadly, for some minor
discrepancies --which should've been redressed quickly
and simply (and there were even offers to assist!)--,
and appears to be yet NA, unless maybe by something
called the Internet WayBack Machine or whatever ... !?))


--dl*
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xarax

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Re: Important Double Sheet Bend query
« Reply #20 on: June 18, 2014, 11:37:53 PM »
mostly, knot books seem to copy other knot books, even errors !

Mostly, knot books ( and sites ) seem to mimic other knot books ( and sites ), in erring...
« Last Edit: June 18, 2014, 11:39:13 PM by xarax »
This is not a knot.

roo

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Re: Important Double Sheet Bend query
« Reply #21 on: June 18, 2014, 11:38:51 PM »
[...]
Of course, the zeppelin is woefully awkward with much
line-diameter difference, [...]
With much line diameter difference, any bend is going to look awkward.  Did you have some elegant exception in mind outside of a hitching solution?
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Luca

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Re: Important Double Sheet Bend query
« Reply #22 on: June 19, 2014, 12:11:36 AM »
Hi Seaworthy,

For ABOK #488, the version I use, there was always no slippage of the thicker line and only tightening, not slippage of the thinner one:

Discard them both!
Try this similar knot, intead:
looking at #488, follow the path of the
thinner (hitching) line from the tail
through the knot --it reaches across the
bight (not through it),
turns around it fully,
then turns around again but is tucked through
the bight.
So, with this vision, tie $488 in reverse
(tails are SParts & vice versa --which keeps the
"same side" relationship (tail & tail, SPart & SPart)).
BUT on both turns around the bight, tuck the
working end (of thinner line, in your example)
through the bight (otherwise, you'll have a jamming
knot!). .......
I will work through your explanation of the lapp bend later today, as it is not instantly apparent what you mean. Do you have a link to an image of it?

(the "standard" Lapp knot: http://davidmdelaney.com/Lapp-knot/Lapp-knot.html )

I suspect that is something similar to the structure visible in the first image at the bottom of this post (to get the bend mantain the standing part in blue,cut the eye and use the second leg of the eye(in red) as the other standing part),but I expect to be disproved...

http://igkt.net/sm/index.php?topic=4321.msg27309#msg27309

As a bend it seems to be really good and secure, but do not use the loop version illustrated there if you do not want to risk of heavily imprecate while trying to untying it...(in fact even the bend can be a little difficult to untie, also for this I expect to be disproven ...)
(for the record,in the second diagram there,is illustrated that can be seen as a loop version of #488.The offer for try the "Tresse"(the term is by alpineer,which has presented the Tresse Bowline) version is still valid, the difference between the two is(apparently) minimal (continuation of the standing part over itself vs under it self).)
Regarding the Zeppelin topic, it may be interesting to this thread:

http://igkt.net/sm/index.php?topic=2159.msg15189#msg15189

                                                                                                                           Bye!



Seaworthy

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Re: Important Double Sheet Bend query
« Reply #23 on: June 19, 2014, 03:51:09 PM »
Dan, firstly, thank you for all the info. It has been very interesting reading your responses.
I will have a play with all 4 twin overhand bends.

If lines are of a thick diameter, neither the sheet bend nor double sheet bend is preferred, instead a Carrick is used.
Really?
I've never found a carrick bend tied anywhere
in the Wild !  I've heard, well, seen on t.v., that
it is used by the Alaskan crabbers.

It is still used for very thick line. Best bend for that, as far as I am aware.

So, my question remains.
Is #1434 or #488 going to perform better under load,
particularly when the diameter of the lines is different?
If so, 1434 should be banished from sailors' repertoires :).
You shouldn't be so narrowly Index-to-exact-knot-minded,
but understanding of how the knots work so that
you can make adjustments per situation.

Yes, agreed. But I am raising this issue because very few people using a DSB are at all aware there is a second version. So how can they make informed decisions?
If only one version is taught or displayed anywhere, why is it the worse one?

Btw, FYI Dave Richards of the Cordage Institute (or of
a member firm --but I believe he was on the board ...)
did testing of kernmantle ropes (rockclimbing, caving,
SAR), and found that sometimes the dbl.S.B. slipped but not the single

Ah huh! EXACTLY!!!

That is what I am jumping up and down about on this thread. I bet he ties #1434 (ducking for cover if not LOL), that all books teach, as does everything online and sailing school and even this website to Sea Cadets. #1434 can certainly slip in even double braided polyester. It is the un-snugged version of 488 and therefore not pre-tightened properly if it is only tightened and left in this form.

Maybe 1434 never slipped in natural fibres and so it was deemed adequate.

The big question I am raising in this thread is why is it taught exclusively now?

(& also the fisherman's knot(!),
sometimes both (resp. 12.5mm & 7mm low-elongation),
and once only the single (dynamic).  So, that was eye-opening!

Really fascinating stuff! Thank you. Such a pity the report was removed from view.
My theory is that these knots may have been inadequately pre-tightened or not snugged properly before load was applied.
« Last Edit: June 19, 2014, 04:59:16 PM by Seaworthy »

Seaworthy

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Re: Important Double Sheet Bend query
« Reply #24 on: June 19, 2014, 07:51:24 PM »

Discard them both!
Try this similar knot, intead:
looking at #488, follow the path of the
thinner (hitching) line from the tail
through the knot --it reaches across the
bight (not through it),
turns around it fully,
then turns around again but is tucked through
the bight.
So, with this vision, tie $488 in reverse
(tails are SParts & vice versa --which keeps the
"same side" relationship (tail & tail, SPart & SPart)).
BUT on both turns around the bight, tuck the
working end (of thinner line, in your example)
through the bight (otherwise, you'll have a jamming
knot!).  You might even make another turn,
and the tail can be further tucked out through
its own initial turn around the bight.
(If the diameters are much different, this becomes
problematic to secure, as the large-roped bight will
see too much space for the small hitching line to
be nipped.)

Hi Dan
I have been looking at the lapp bend.
Could you please tell me if I have interpreted your instructions correctly?

The single I am reasonably confident with, the double not so:

Seaworthy

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Re: Important Double Sheet Bend query
« Reply #25 on: June 20, 2014, 04:38:23 AM »
Sorry, can see I stuffed up the double (wasn't paying attention).

The image I have attached below is simply the 488 with the standing part and tail reversed and with the tails still coming out on the same side.

The bit I am confused about is "BUT on both turns around the bight, tuck the working end through the bight (otherwise, you'll have a jamming knot!)."

Is a diagram or photo possible please or a link to one? Or now that I have this image any other way of explaining the tucks?


Seaworthy

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Re: Important Double Sheet Bend query
« Reply #26 on: June 20, 2014, 04:43:42 AM »
Oh, skip that LOL, the light just went on. I just had to tuck the end through the bight as you said :). Sorry, my brain just froze completely. I am not used to following knot instructions, but looking at images instead.

I will take a photo in a moment and post it.

I will give both a try on our winch later (making sure I don't use the end of my yankee sheet for the jamming version) and report back.
« Last Edit: June 20, 2014, 04:47:15 AM by Seaworthy »

Seaworthy

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Re: Important Double Sheet Bend query
« Reply #27 on: June 20, 2014, 05:06:18 AM »
Now, if nothing else I am sure I am providing you with some entertainment :).

Take 3 of the double lapp is attached in the next post what I assume is its jamming form. When going to tuck the bight in I realised in take 2 I had not started the first pass over the top.

The tucked version will also be posted.

Anyone going to put me out of my misery and tell me if these are right before I test them? :)

Seaworthy

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Re: Important Double Sheet Bend query
« Reply #28 on: June 20, 2014, 05:16:40 AM »
Double lapp jamming and non jamming versions attached.
Before I go test it, is this finally correct?

If I just followed Dan's instructions it would have made it easier :).
« Last Edit: June 20, 2014, 05:17:43 AM by Seaworthy »

Seaworthy

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Re: Important Double Sheet Bend query
« Reply #29 on: June 20, 2014, 05:24:55 AM »
Interestingly, did anyone notice that the first version I posted of the double lapp was in fact correct for the jamming version, just unsnugged?

ie It was based on the 1434 version of the DSB, not the 488. When finished, just rolling over the first turn in my first version produces the correct bend.
« Last Edit: June 20, 2014, 05:26:17 AM by Seaworthy »