Author Topic: Some tests about the slippage of some bends using ropes with different diameters  (Read 2117 times)

Luca

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Hi all,

Some homemade, totally informal,superficial,trivial tests.
Ropes used:some 2,5 mm polyester nautical braided rope vs some 9mm... ehm...unknown material(nylon?PP?) braided rope.
Loading mode:the bare force of my arms(which are not very strong...).
Number of tests:not counted;casual and unknown.
After these promising premises, these are the results of my tests:
("failed" indicates that I was able to completely slip away  the knot, "passed" indicates that I could not:possibile clarifications will be exposed  case by case)

Lapp bend                                                           failed
Double Lapp bend 1                                            failed
Double Lapp bend 2                                            failed(*1)
Sheet bend                                                         failed(*2)
Double Sheet bend  #1434                                passed(*3)
Double Sheet bend #488                                   passed
"Tresse" Sheet bend                                          passed
 Simple Simon under                                           failed
Simple Simon over                                              failed
Simple Simon double(*4)                                    failed
Zeppelin bend                                                    passed
Asymmetric Zeppelin bend(*5)                                 passed
Lee Zep A1 structure bend version(*6)              passed
Lee Zep A1 X srtucture bend version(*7)           passed
 
(*1)On one occasion the thinner rope is oddly capsized in a way that I could do not slip it away.
(*2)Slipped away about 80% of the times, in other occasions I noticed some slippage without that I could do it slipping away,in other occasions I have not noticed any slippage;on one occasion I found in my hands the thicker rope straightened,with the thinner rope that formed a sort of double wrap hitch  around it...
(*3)I was never able to completely slip it away, but in a couple of occasions I have actually noticed some slippage.
(*4)I tested the "standard" version: in reality can be performed four versions of this bend: over-over ("standard"), under-under,          over-under, under-over.
(*5) http://igkt.net/sm/index.php?topic=2159.msg15189#msg15189
(*6)The Lee Zep A1 Bowline is visible at the first pic in this post: http://igkt.net/sm/index.php?topic=3908.msg27595#msg27595 ,
to obtain the bend I refer "cut" the eye of the loop,use the standing end of the loop as the standing end of the one link(and use the thicker rope for this link),and use the second leg of the loop as the standing end of the other link.
(*7)The Lee Zep A1 X Bowline is visible at the second pic in this post: http://igkt.net/sm/index.php?topic=3908.msg27595#msg27595 ,
to obtain the bend I refer "cut" the eye of the loop,use the standing end of the loop as the standing end of the one link(and use the thicker rope for this link),and use the second leg of the loop as the standing end of the other link.

The diameter ratio between the two ropes is a bit extreme,but this was good for testing with my bare arms...
I think that all the bends tested, if tied using ropes of the same diameter,probably are more appreciable in terms of security than the Sheet Bend,or the Double Sheet bend(in whatever way is dressed),or the "Tresse" version of the Sheet bend.Regarding the bends that have failed these tests(but if my tests were worth something ...),surely remains interesting to test when (ie progressively increasing the ratio of the diameter of the two links) the use of these bends stops being interesting with respect of the use of the Sheet bends and the other bends that have passed the test (or rather: who might have  passed a test better than my. ..).

                                                                                                                           Bye!
« Last Edit: June 21, 2014, 10:55:00 PM by Luca »

Dan_Lehman

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Try this --as you say, this is a case of
rather large difference in diameters of the
ropes--:  come through as for a sheet bend
maybe reaching a little father down the bight,
and turn around the big-bight legs & hitching
line SPart a couple times,
and next time go Over-&-tuck-back-under
the hitching line's SPart, going around (now
in opposite direction to initial wraps) and
come back to tuck tail between SPart &
big-bight and through the just-formed
U-turn/bight of the hitching line.

Using similar-to-yours rope & cord (and the
rope moderately stiff poly-combo twisted),
this holds well, and seems to show no inclination
to loosen (though the hitching line's SPart IS
amply loose coming through the big-bight).

(Heck, I've even fiddled a version that is holding
--when slack-- in damningly intractable thick
monofilament nylon (the working of which is
flexing parts of my vocabulary better left silent!  >:( >:(
=> take the tail OVER its own SPart & collaring
bight and down through that bight AND through
the big-bight legs at point between its final wrap
and preceding ones (and now I see that its SPart
has also nipped it there, but either way ... re that).
)


--dl*
====

Seaworthy

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Hi Luca
I, too, am on a quest to find out what works for lines of different diameter. This is really not well known at the moment, either for quick and easy bends, or more time consuming ones.

It is a tricky quest, as results are likely to vary with different diameters and various differences in diameter and various materials, but any info would be useful.

I have a query. Did you dress the knots as tightly as you possibly could by hand first? I found this made a huge difference. As I commented earlier some knots "slid like a hot knife through butter" when I was playing with them initially and this was when I had not paid extra attention to the pre-tightening. They held when dressed super tightly and the load applied quickly.

Even if the answer is 'no', I think your info is still useful. I have always hand pre-tightened knots, but not taking the extra special care and time to do so as I am in the tests I am doing at the moment.

Not only pre-tightening made a difference, but it was important for some of the bends to apply the load as quickly as possibly (eg for the sheet bend) as otherwise they loosened very easily. The sheet bend also loosened easily after load was released, making it a less suitable bend if load is applied and released and applied again. I bet this also occurs to some degree even when line diameter is the same.




Luca

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Hi Seaworthy,
First of all, I feel obliged to warn you that maybe I'm the worst tester of knots with whom you can communicate in this forum...
Coming to your question:compatibly with the large difference in diameter between the two ropes,and with the fact that the rigidity of the thicker rope that I used does not allow contact between the two strands of the rope at the point in which is bent to form a bight or a turn,leavingfor example in this way the possible standing part of the thinner rope that passes through it completely free to move,I just tried to keep the geometry of the thinner link  as similar as possible, while I have "modeled" it around the thicker link,as it would have appeared if I tied  the bend with two ropes of equal size,avoiding leave any slacks of the thinnest string and trying to give the thicker link a form as "compact" as possible.
This has surely resulted in some form of pre-tightening, but in reality I did not care to tighten the knot as much as possible before putting it under load (if it can be called "load" that to which I have subjected these bends ...).
Regarding the way in which I loaded these bends, I acted in a "soft" way, without giving jerks,nor at the time to start loading the knot, nor after.
As you may have noticed, for my test I blatantly based on your list, adding some other bend ( ;)): the aim was to see what was going on exaggerating the difference in diameter of the two links(not to discredit in any way,with some different result, the initial results of your tests, which among other I think they are much more reliable than my...).
Thank you, I also wait to see the further results of your test! 

                                                                                                                          Bye!

                                                                                                                     
« Last Edit: June 23, 2014, 02:04:19 AM by Luca »

Seaworthy

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......
Regarding the way in which I loaded these bends, I acted in a "soft" way, without giving jerks,nor at the time to start loading the knot, nor after.
As you may have noticed, for my test I blatantly based on your list, adding some other bend ( ;)): the aim was to see what was going on exaggerating the difference in diameter of the two links(not to discredit in any way,with some different result, the initial results of your tests, which among other I think they are much more reliable than my...).
Thank you, I also wait to see the further results of your test! 
                                                                                                                          Bye!                                                                                                         

Yes, the way the load is applied (slowly or rapidly, smoothly or in jerks) will certainly make a difference as well. So may variables aren't there!

I didn't include the Zepellin, as I stuck with "simple" bends (I will test one just to see what it does for interest later). For a while I have used the Alpine Butterfly bend when connecting knots of a similar diameter (just so they can be untied), but recently practiced the Zepellin to try and get it into my muscle memory, as I know it is a better bend (i was interested to read Dan Lehman's comment that it could be untied). The Hunter I suspect is better again, but probably can't be untied after load.

Would be nice to find the best simple and more complicated bends (sometimes time is critical, so the best simple version is useful info). The Zeppelin keeps cropping up. I think it was Dan Lehman who suggested earlier that the Zeppelin could be used for line of different diameter. When it came to line of different diameter someone on cruisers forum said "I prefer the Zeppelin, with a double turn on the thinner line if the diameters are very different." Load tester would be needed for this, as my limited gear will not be sufficient to determine anything at all.

Still, it would be really nice to know what % difference between tying the best of the "simple" bends and something like the Zeppelin (with and without the double turn). Is it actually worthwhile going to the trouble of the bend that takes longer to tie, it harder to do in the dark and is easier to make an error with? Load tester is needed for this :(.

xarax

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   It is very difficult to me to understand ( or define ) what exactly a "simple" knot is (or what it means)...(1). And this happens even for the most simple property of a knot, which does not involve the knot tyer : its form - so, about how "simple" a knot is regarding understanding, learning, memorizing, remembering, tying, untying, dressing, inspecting, adjusting, etc, things are much worse !  :)
   However, I tried to forget all my prejudices about this complex issue, and tie some bends which I suppose that will appear "simple" to most people - whatever that means.
   I believe that the single overhand knot is considered as a "simple" knot - and the same is true for a simple p- or q- shaped bight. Joining an overhand knot, tied on the smaller rope around the Standing Part of the bigger rope, with a bight, tied on the bigger rope around the Standing Part of the smaller rope, should look like a "simple" bend to most people, I guess. ( See the attached pictures )
   An overhand knot tied around a line may jam - but as the diameter of the line gets larger, it jams less often and less easily. Also, instead of the single overhand knot, we may enhance the self-locking ability of the knot/hitch tied around the bigger line, and use a double overhand knot, or even a fig.8 knot, without sacrificing much more in the temple of "simplicity".
   First, with the last segment of the smaller line, tie a tight overhand knot around the bigger line. Then, form the p- or q- shaped bight on the last segment of the bigger line. Finally, pull the two free ends of the bend until the two links "lock". You have tied a "simple", asymmetric, mixed harness / fisherman s knot, which I had seen that, at least on marine lines as the red/blue ones shown in the pictures, is quite secure. To be on the safe side, leave long tails, so the two links can consume some part of thems during their "closing" around themselves and around each other.   

1. http://igkt.net/sm/index.php?topic=3740.0
« Last Edit: June 23, 2014, 11:54:55 AM by xarax »
This is not a knot.

Luca

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Hi Dan,

Try this --as you say, this is a case of
rather large difference in diameters of the
ropes--:  come through as for a sheet bend
maybe reaching a little father down the bight,
and turn around the big-bight legs & hitching
line SPart a couple times,
and next time go Over-&-tuck-back-under
the hitching line's SPart, going around (now
in opposite direction to initial wraps) and
come back to tuck tail between SPart &
big-bight and through the just-formed
U-turn/bight of the hitching line.

Thank you.... :'( :'( :'(
...But now it is time to stop whining, and begin to try ...
First attempt.

                                                                          Bye!


« Last Edit: June 23, 2014, 11:39:34 PM by Luca »