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Old 17-04-2017, 04:50   #241
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Re: Zeppelin Bend - next best thing to sliced bread

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Originally Posted by Wotname View Post
Okay, the Easter bunny has been and all such matters have been attended to .

Hope all went well...
Quote:
Now is the time for some destruction . I prefer to break things rather than test them but...... I can make some comparisons by breaking stuff and if the results are interesting, I might work out some way of measuring the force required to cause failure .

I don't have formal load testing equipment but Ann T has clocked me; I can only assume she knows me too well!


Yep Ann, that is exactly what I am planning to use. The ram will generate approximately 40 tons when extending and perhaps 20+ tons when retracting. It is far easier to setup rope testing in the retraction mode and also this mode may be easier to monitor the pressure on high pressure side on the ram at the moment of failure. FWIW, the pump has a maximum of 3,500 psi (I think).



First lets break some stuff

I tried some used 10 mm polyester double braid yesterday and it broke it without blinking.

I'm thinking some series knots and bends in different lines to see what slips, what can be undone and what breaks first.

There is not a lot of exotic lines available locally but I can get spectra in common configurations in Hobart (or on-line - I guess).

I will have a look at some DIY way of adding a strain gauge at the end of the ram or perhaps just a pressure gauge on the high pressure side of the pump. Any ideas on how to achieve this are welcome.

Over to SWL and IN...
I understand that Spectra is a variant of Dyneema, so that should work okay.

I'm not experienced with load cells, so can't advise.

Your pull-until-broken scheme should tell us whether the various Zeppelin bends and loops will slip, and whether they can still be easily untied after being loaded. I'm particularly interested in what happens to what I called the iZeppelin loop, and to what SWL called the Tucked Zeppelin bend.

Thanks for contributing to our knowledge base.
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Old 17-04-2017, 23:23   #242
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Re: Zeppelin Bend - next best thing to sliced bread

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Originally Posted by ImaginaryNumber View Post
................

Your pull-until-broken scheme should tell us whether the various Zeppelin bends and loops will slip, and whether they can still be easily untied after being loaded. I'm particularly interested in what happens to what I called the iZeppelin loop, and to what SWL called the Tucked Zeppelin bend.

Thanks for contributing to our knowledge base.
OK will work on doing that. Please don't expect quick results, we are working on Island time here...

Might be able to get some say 8 mm (5/16") spectra / dyneema next week(ish).

Stand by
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Old 17-04-2017, 23:37   #243
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Re: Zeppelin Bend - next best thing to sliced bread

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Originally Posted by Seaworthy Lass View Post
Hi Wottie
Thanks for the generous offer .

What I would love to have tested above all is my Bullseye weave (see my avatar) made up in a removable soft shackle type version.

If you have load testing equipment, what I will do later this year is make up 10 samples for you in about 6mm dyneema and post them to you with a LF ring, maybe with some standard soft shackles using a diamond stopper for comparison. I think this is the number of samples Evans Starzinger used in some of his trials and it should be enough to provide statistically significant results.

A very grateful SWL x
Ahh.. the old bullseye weave eh .

After giving the whole thing more thought, I am thinking that my results would be too coarse for a Lassie like yourself. You will be wanting more finery in the results. So perhaps a custom made rig might be better - dunno exactly how to do that yet but it can't be too hard - mechanical engineers do it all the time .

First things first, what is the expected failure point (in say Kg or Lbs) of your weave? This would be the starting point to find a suitable strain gauge and then a suitable method of applying the force. If there isn't anything suitable in the shed, there is a whole valley here of DIY farmers / engineers etc to call on.

I have advised by a very helpful CF member to be cautious in using hydraulics for breaking high modulus lines - very hard on the seals. So I will be proceeding with caution on that front.
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Old 20-08-2017, 04:49   #244
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Re: Zeppelin Bend - next best thing to sliced bread

thanks for showing how to tie zeppelin bend.

I also learned at the same time carrik bend to use for soft shackles buttons and also alpine butterfly bend as part of my large shade project.

And then studied them all three to pick one for everyday use.

My conclusion alpine bend is the strongest of three, then zeppelin then carrick. Reason for this is that rope coming into bend surrounds two ropes in full circle for zeppelin and carrick and three ropes for alpine bend, hence loop is largest for alpine hence most rope strength retained.

secondary loop that locks the knot and is probably of lesser importance for strength circles 2 ropes for zeppelin and alpine and one for carrick.

Now question to SL: why do you believe zeppelin is strongest/best bend ?
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Old 20-08-2017, 15:53   #245
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Re: Zeppelin Bend - next best thing to sliced bread

I agree than the Apline may be marginally stronger than the Zep. But strength isn't everything. I prefer the Zeppelin over the Alpine for several reasons.

1. Ease of tying.
2. No need for careful dressing.
3. No danger of mis-tying (see "Evil Imposter" at link below)
4. Less bulky than Alpine Butterfly.
5. Symmetrical ( i.e. Prettier)


Butterfly Bend
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Old 20-08-2017, 20:21   #246
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Re: Zeppelin Bend - next best thing to sliced bread

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I agree than the Apline may be marginally stronger than the Zep. But strength isn't everything. I prefer the Zeppelin over the Alpine for several reasons.

1. Ease of tying.
2. No need for careful dressing.
3. No danger of mis-tying (see "Evil Imposter" at link below)
4. Less bulky than Alpine Butterfly.
5. Symmetrical ( i.e. Prettier)


Butterfly Bend
Absolutely agree

It confused me as I read somewhere that zep bend is the strongest possible bend.

yet to decide which one to use. Zep is not that easy to tighten so that end lengths are nicely balanced. Carrick seem to be the most practical for that.
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Old 27-05-2019, 17:03   #247
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Re: Zeppelin Bend - next best thing to sliced bread

Here is a paper on the Zeppelin bend for those who are interested!

Link: PACI (at #4 in the table)

I would also comment that the notional concept of strength (ie the MBS yield point of a knot) is largely irrelevant. When discussing strength - commentators often confuse that concept with security and stability.

The jury is still out with UHMWPE type cordage (eg 'Dyneema') - in that security is dependent on how 'frictive' the sheath is. For example, the Zeppelin bend will remain secure in some brands of 'Dyneema' but in others, it may 'slip'. Your mileage will vary. Peer reviewed testing needs to be carried out to fully and properly investigate the effect UHMWPE cords have on otherwise known-to-be-secure 'bends'.
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Old 28-05-2019, 04:52   #248
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Re: Zeppelin Bend - next best thing to sliced bread

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Originally Posted by agent_smith View Post
Here is a paper on the Zeppelin bend for those who are interested!

Link: PACI (at #4 in the table)

Thank you!



What a great resource for "knotties"


Ive downloaded several of those documents and spent quite some time this evening going through them!
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Old 28-05-2019, 05:38   #249
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Re: Zeppelin Bend - next best thing to sliced bread

Greetings and welcome aboard the CF, Agent Smith.

Animated Knots by Grog is another excellent site for learning how to tie knots of any kind. ➥ https://www.animatedknots.com/
Zeppelin Bend ➥ https://www.animatedknots.com/zeppelin-bend-knot
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Old 23-09-2021, 12:09   #250
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Re: Zeppelin Bend - next best thing to sliced bread

We are on a charter that included mooring lines that are too short, so I have bent pairs of them together with a Zeppelin Bend. Today I noticed that one of the bends had spilled after a windy night.


1) Is this expected?
2) Is the knot still strong?
3) Is there anything that can prevent it?
4) Should I go back to using a sheet bend?


Here are four photos: two of the knot that spilled, and two of the knot that didn't spill. They were tied identically in identical rope. The rope is about 1" diameter, and appears to be nylon double braid. I have included a fifth photo of our shore tie for perspective.
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Old 23-09-2021, 14:21   #251
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Re: Zeppelin Bend - next best thing to sliced bread

I've just spent some time trying to manipulatee a loosely tied zeppelin so that it looks like the knot in your photos. I am unable to reproduce your last knot no matter how much I twist things. I have also never seen a zeppelin collapse into anything resembling that.


It doesn't seem to be the same knot at all. I suspect that the two knots were not in fact tied identically and the "collapsed knot" is an entirely different configuration.
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Old 23-09-2021, 17:08   #252
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Re: Zeppelin Bend - next best thing to sliced bread

The only difference is that two of the turns that are usually side-by-side are crossed. I will post a video when I have better internet access.
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Old 23-09-2021, 18:32   #253
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Re: Zeppelin Bend - next best thing to sliced bread

I'm pretty sure I managed to replicate your knot (by knotting the left hand rope and then "backfeeding" the right hand rope to get the same structure. The first two photos show views approximating to yours - they appear to me to be exactly the same knot as yours.


The second two are the same knot slackened and spread out. It's pretty obvious that the ends were lead into the loops conpletely incorrectly and you do not have a zeppelin bend.
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Old 23-09-2021, 21:59   #254
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Re: Zeppelin Bend - next best thing to sliced bread

Hello 'Jammer'


Your photos lack the specific detail I need to determine precisely what you tied.
I can confirm that a correctly tied Zeppelin bend does not capsize or undergo any dynamic change under load.

I therefore suspect that you tied a 'False Zeppelin bend'.
Hopefully my photo inserts correctly...
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Old 23-09-2021, 22:11   #255
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Re: Zeppelin Bend - next best thing to sliced bread

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I therefore suspect that you tied a 'False Zeppelin bend'.
Hopefully my photo inserts correctly...

Ah-ha! Yep, my third photo is a rotation/reflection of your first image
Definitely a False Zeppelin.
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