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Old 27-07-2016, 13:15   #16
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Re: whipping - antal method - low friction ring

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Originally Posted by estarzinger View Post
I took apart an antal strop/ring - very interesting . . . .

Attachment 128526

The bury is (only) 33x, which my testing did identify as 'minimum for full strength' with steady state loads. The blue dots are where the bury's end - so they are as long as they can possibly be given the strop length.

There is an industry debate about whether this is satisfactory for cyclic/shop loads - antal obviously thinks so, others think in the 40's is needed and others think in the 60's or even 70's is needed.

It is not sewn, but it is very tightly whipped (which will also prevent low load slipping).

Attachment 128527

The whipping is as close to 1:1 as they could accomplish. The whipping cord is dyneema. I am guessing it is done on some sort of jig because the whipping is extremely tight, but it still seems like handwork and not automated.

The main part of the whipping shows the telltale sign of half hitches (that spiral row of strand crosses), which is confirmed when I took it apart. The key question is how are the ends terminated. . . . see next post.
The wide throat angle also costs them; you would need to see how much the strope and ring deform to know how much that matters.

At the end of the day, the 33x is not going to matter because of cumulative minor inefficiencies. Which is fine--it's still light.
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Old 27-07-2016, 14:00   #17
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Re: whipping - antal method - low friction ring

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Originally Posted by Seaworthy Lass View Post
Odd that they have chosen to work up to the throat with the half hitches, rather than away?
SWL,

I think the reason they do that is to make the loop around the ring as tight as they can to prevent the ring "popping out" of the loop. If the half hitches start close to the ring then it won't get much tighter as more hitches are added. But starting low and working up can really grip the ring better.
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Old 27-07-2016, 16:57   #18
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Re: whipping - antal method - low friction ring

Dan, right on. The seizing always works towards the eye. Jams tight against the turn before it.
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Old 27-07-2016, 18:48   #19
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Re: whipping - antal method - low friction ring

Nice.

I think this could be sewn too.

b.
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Old 27-07-2016, 20:02   #20
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Re: whipping - antal method - low friction ring

Most interesting, Evans. A valuable contribution.

From your photo, that looks like the Antal R10.07. The specs seem to be 4.5 mm Dyneema and a Safe Working Load of 700 kg. (and a recommended retail of Euro 10.20 if I read things correctly).

See the specs at: http://antal.it/ENG/RL4-5_en


Question (for Evans and SWL): how does that specified SWL of 700 kg relate to your (and Seaworthy Lass's) theoretical calculations of strength, taking into account 4.5 mm Dyneema and the near 1:1 throat angle?


Question (for SWL): given that, what would be your guess at a conservative Safe Working Load for your Bullseye Strop if you used 4.5 mm?
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Old 27-07-2016, 20:13   #21
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Re: whipping - antal method - low friction ring

Further to the above:

Antal specifies the low friction ring, the 10x7 ring, to have a Safe Working Load of 800 kg.


See those specs at: soft links-antal


It further says: "Antal gives a safe working laod for Rings that corresponds to a situation where the aluminum structure holds, but undergoes a slight (slight) deformation. So they don't break. Nor do they ever loose their low friction property."(typo is theirs, not mine, as is the claim that the smooth anodized low friction surface lasts forever; source: http://antal.it/ENG/friction_on_rings).


So the 700 kg SWL for the R10.07 (the 10x7 ring plus the soft loop + seizing) depends on the Dyneema, not the ring.
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Old 27-07-2016, 22:01   #22
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Re: whipping - antal method - low friction ring

When the ring is used in a strop its SWL is much higher than when it is used to join 2 loops. The latter is what can deform the ring because it is in tension. I doubt a cruising sailboat could put enough compression load on a ring in a strop to deform it even a little. My opinion is that the vendor stated SWL is meaningless when used in a strop.
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Old 27-07-2016, 23:29   #23
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Re: whipping - antal method - low friction ring

Quote:
Originally Posted by Alan Mighty View Post
Most interesting, Evans. A valuable contribution.

From your photo, that looks like the Antal R10.07. The specs seem to be 4.5 mm Dyneema and a Safe Working Load of 700 kg. (and a recommended retail of Euro 10.20 if I read things correctly).

See the specs at: soft links-antal


Question (for Evans and SWL): how does that specified SWL of 700 kg relate to your (and Seaworthy Lass's) theoretical calculations of strength, taking into account 4.5 mm Dyneema and the near 1:1 throat angle?

Question (for SWL): given that, what would be your guess at a conservative Safe Working Load for your Bullseye Strop if you used 4.5 mm?
I will answer the first question later, as I can now calculate the loads better (slowly learning ).

I have attached the specs from Antal below that I found (yours are different).
With their loop using a 10mm Antal ring, they use 4 mm dyneema. It depends on the dyneema used, but this may have a breaking strain of 2000kg.
They give a SWL of 400 kg for the strop (not 700) in the specs below. Final conclusion is identical regardless of what line they use.


Bullseye loop strop predictions:
Theoretically, if a 2:1 throat is used on a Bullseye (this will make the ring snug) then system strength is around 188% of tensile line strength. Compression issues may or may not lower this a bit. The line does not looks stressed by compression when it action so I doubt this is a big factor. Conservatively you could slice 10% off that, making it 170%.
If the base is looped around a 4mm object, the system strength is around 95% of tensile line strength. If it is cow hitched, it drops to around 85% of line strength.
If the base is looped around an 8mm object, the system strength is around 120% of tensile line strength. If it is cow hitched, it may drop to around 107% of line strength.

So, working conservatively on securing it to a 4mm diameter object, and cow hitching it as Antal suggest, the system strength is limited by the cow hitch to 85% line strength.

This is 1700 kg if 4 mm (2000 kg) line is used.
It depends how you want to calculate SWL.
If 1/3, this would make it 567 kg
If 1/4, this would make it 425 kg
If 1/5, this would make it 340 kg

This is identical to the Antal loop, as both systems have the limitation of the cow hitch.
The Bullseye does not, however, have any issues with whipping giving way, or in time clenching the dyneema so much it would cut through and eventually break. I think this would eventually occur with persistent high loads.
Longevity is a very important factor the calculations do not take into account. How long is that whipping going to last if subjected to the full SWL for long periods?
The Bullseye loop strop has no such limitations.


Bullseye soft shackle strop predictions:
I predict the limitation here is the Diamond knot, giving very conservatively 150% of line tensile strength if tied reasonably and care is taken with distributing the load in the weave (easy to do). It may be around 175%.
No cow hitch is necessary with it, as it opens.
If the base is looped around a 4mm object, the system strength is twice 95% = 180% of line tensile strength, so this is no longer the limitation.
So the diamond stopper limits the system (stronger options could be used that may give up to 230% of line tensile strength).

So working on 150 - 175 % of 2000 kg = 3000 - 3500 kg:
Again, it depends how you want to calculate SWL.
If 1/3, this would make it 1000 - 1160 kg
If 1/4, this would make it 750 - 870 kg
If 1/5, this would make it 600 - 700 kg

So using the same dyneema and same Antal ring, the the Bullseye soft shackle strop is nearly twice as strong as both the Bullseye loop strop and the Antal strop.
Bonus too is that it could be made shorter.
Finally it is much quicker to make. No whipping or splicing of any kind to fuss with.


SWL
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Old 28-07-2016, 04:19   #24
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Re: whipping - antal method - low friction ring

Quote:
Originally Posted by Alan Mighty View Post
Question (for Evans and SWL): how does that specified SWL of 700 kg relate to your (and Seaworthy Lass's) theoretical calculations of strength, taking into account 4.5 mm Dyneema and the near 1:1 throat angle?
Calculations of the forces acting on the throat:

I need a hand here please guys, as I am in my infancy with these calculations. The maths is a breeze, it is just the physics I am finding difficult.

I have drawn the Antal 10/7 ring dimensions below. From my data sheet above they say they are using 4 mm dyneema. For the dyneema not to be forced off (eg with flogging), I think the inner bit of the line needs to just reach the outer edge of the ring, so I have based figures on that. This assumption may not be correct.

Evans kindly drew out for me how ropes behave, so I am using his drawing to fill in the dimensions of an Antal 10/7 ring (it is therefore not to scale).
See diagram below.

I know this is all oversimplified, but here are the calculations based on the figures below:
The throat ratio is 1.33 : 1
The throat angle is 74°
The loss in strength with the throat angle is exactly 20%.
So if nothing was occuring elsewhere, the dyneema will theoretically break somewhere around the ring at 160% of line tensile strength as we are working with a loop.
Am I correct so far?

The next bit I am unclear on.
I think the vector pushing out the whipping is exactly 75% of the load as forces act on both sides in opposite directions.
Is this correct?

Edited to add: it is half this (ie 37.5%) so these calcs need to be modified

Antal have listed a SWL of 400kg and from my calculations in the previous post they seem to be using a safety factor of 4 to calculate this figure.

If the system can handle 85% of line tensile strength before it fails at the cow hitch:
Using 4 mm dyneema: 85% of 2000 kg = 1700 kg, therefore the force on pulling the whipping apart at this stage is 1700 x 0.75 = 1275 kg
Using 4.5 mm dyneema: 85% of 3000? x 0.75 = 1912.5 kg

Anyway, taking a quarter of this for SWL:
For 4 mm = 318.75 kg
For 4.5 mm dyneema = 478.13 kg ( unless they are using exotic dyneema like Dynex Dux, the SWL of 700 kg they state doesn't seem right).

So the whipping needs to handle roughly 320 kg for 4mm dyneema or 480 kg for 4.5mm dyneema, pushing it apart.
Would it do this?
Evans would know far better, but I doubt it, particularly as it just looks like very thin dyneema.
I think the bulk of the force is on the top couple of half hitches. The rest is just stopping the first couple of critical hitches sliding down.
If it does handle it, I think it would certainly damage the underlying dyneema in time with sustained loads close to SWL.

Any engineers here that can please help with the physics? The maths is OK I think.
I would very much like to understand this and I have been struggling badly, drawing appalling conclusions and looking absolutely stupid, so much so I think lots of people have lost patience with me.

SWL

PS Although the Bulleye loop strop would have the same SWL, as it is restricted by the cow hitch attaching these strops, the throat ratio only needs to be 2:1. The perpendicular load at this point is 35%, not 75%.
It us simply acting to compress neighboring bits of the line, there is no whipping being stressed apart.
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Old 28-07-2016, 05:14   #25
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Re: whipping - antal method - low friction ring

wow now that was some good entertainment there
not sure why all the surprise and wonder this particular technology has been in existence for a few hundred years the only difference is the fiber and the eye would have been called an eye (not a low friction ring, ahh i just shook in my seat thinking of that) and made of lignum vitie
it doesn't slip due to the seizing and you must work the seizing up to the eye to get any sort of grip on it because you cant get a seizing mallet that close to a lump in the line like that
why did you take it apart in the first place
it probably will never be the same ever again
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Old 28-07-2016, 06:14   #26
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Re: whipping - antal method - low friction ring

> So the whipping needs to handle roughly 320 kg or 480 kg pushing it apart.

I may be completely wrong here, but my first thought is: since each turn of the whipping is effectively a loop, does it maybe only need to handle 50% of that force?
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Old 28-07-2016, 06:47   #27
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Re: whipping - antal method - low friction ring

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Originally Posted by StuM View Post
> So the whipping needs to handle roughly 320 kg or 480 kg pushing it apart.

I may be completely wrong here, but my first thought is: since each turn of the whipping is effectively a loop, does it maybe only need to handle 50% of that force?
My logic in leaving it as the full 75%, is that the loop around the ring is a system on its own that needs to be looked at. So the above figures are the case regardless of whether the loop is terminating in one line pulling on it or two. For every unit pulling on it, the force pulling the throat apart is 75% of it.

In the case above we have a cinched loop situation, not an eye splice situation. Does this affect things? Maybe not.

It was doing my head in thinking if it is 75% or half this . I opted for 75%.

Thanks for looking at it and thinking about it.

SWL
Edited to add: been thinking more and going the other way .

If it is halved when whipping because you are using a loop, then the calculated load on the whipping line at the SWL is 160 kg for 4 mm dyneema or 240 kg for 4.5 mm dyneema. This is still a hell of a lot for a half hitch or two to be coping with. I don't think the load is spread over the whole lot. The rest of the half hitches (and all the turns around the LF ring) are there are only to stop the first few sliding down I think.
How much will loads like this damage the dyneema with prolonged use?

This is based on breaking strains of an estimated 2000 & 3000 kg for the two (I don't know what dyneema Antal are using). This varies quite a bit between different manufacturers and how they process it.
Are Antal using the same dyneema whipping line for their bigger models?
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Old 28-07-2016, 10:20   #28
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Re: whipping - antal method - low friction ring

Quote:
Originally Posted by Seaworthy Lass View Post
Calculations of the forces acting on the throat:

I need a hand here please guys, as I am in my infancy with these calculations. The maths is a breeze, it is just the physics I am finding difficult.

I have drawn the Antal 10/7 ring dimensions below. From my data sheet above they say they are using 4 mm dyneema. For the dyneema not to be forced off (eg with flogging), I think the inner bit of the line needs to just reach the outer edge of the ring, so I have based figures on that. This assumption may not be correct.

Evans kindly drew out for me how ropes behave, so I am using his drawing to fill in the dimensions of an Antal 10/7 ring (it is therefore not to scale).
See diagram below.

I know this is all oversimplified, but here are the calculations based on the figures below:
The throat ratio is 1.33 : 1
The throat angle is 74°
The loss in strength with the throat angle is exactly 20%.
So if nothing was occuring elsewhere, the dyneema will theoretically break somewhere around the ring at 160% of line tensile strength as we are working with a loop.
Am I correct so far?

The next bit I am unclear on.
I think the vector pushing out the whipping is exactly 75% of the load as forces act on both sides in opposite directions.
Is this correct?

Antal have listed a SWL of 400kg and from my calculations in the previous post they seem to be using a safety factor of 4 to calculate this figure.

If the system can handle 85% of line tensile strength before it fails at the cow hitch:
Using 4 mm dyneema: 85% of 2000 kg = 1700 kg, therefore the force on pulling the whipping apart at this stage is 1700 x 0.75 = 1275 kg
Using 4.5 mm dyneema: 85% of 3000? x 0.75 = 1912.5 kg

Anyway, taking a quarter of this for SWL:
For 4 mm = 318.75 kg
For 4.5 mm dyneema = 478.13 kg ( unless they are using exotic dyneema like Dynex Dux, the SWL of 700 kg they state doesn't seem right).

So the whipping needs to handle roughly 320 kg for 4mm dyneema or 480 kg for 4.5mm dyneema, pushing it apart.
Would it do this?
Evans would know far better, but I doubt it, particularly as it just looks like very thin dyneema.
I think the bulk of the force is on the top couple of half hitches. The rest is just stopping the first couple of critical hitches sliding down.
If it does handle it, I think it would certainly damage the underlying dyneema in time with sustained loads close to SWL.

Any engineers here that can please help with the physics? The maths is OK I think.
I would very much like to understand this and I have been struggling badly, drawing appalling conclusions and looking absolutely stupid, so much so I think lots of people have lost patience with me.

SWL

PS Although the Bulleye loop strop would have the same SWL, as it is restricted by the cow hitch attaching these strops, the throat ratio only needs to be 2:1. The perpendicular load at this point is 35%, not 75%.
It us simply acting to compress neighboring bits of the line, there is no whipping being stressed apart.
Here's a quick cad for the forces ( I think - please someone check )

Each side of the small bridle will be taking 50%.

Though to be honest, there's a lot going on with the seizing etc, so all of this might well have little resemblance to reality, you'd really need to load test a few samples to know what will actually happen.

A quick look at the antal website doesn't give away much, there's a SWL but no mention of factor of safety or any code which specifies a FOS so they might have load tested a few and got a SWL from that, or maybe just made it up

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Old 28-07-2016, 11:03   #29
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Re: whipping - antal method - low friction ring

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Here's a quick cad for the forces ( I think - please someone check )

Each side of the small bridle will be taking 50%.

Though to be honest, there's a lot going on with the seizing etc, so all of this might well have little resemblance to reality, you'd really need to load test a few samples to know what will actually happen.

A quick look at the antal website doesn't give away much, there's a SWL but no mention of factor of safety or any code which specifies a FOS so they might have load tested a few and got a SWL from that, or maybe just made it up

Hi Conachair
Many thanks for checking that out and putting in the beautiful diagrams.
Your proportions are identical to mine . That bit is nice to know.
Twice 37.5% is where I got my 75% from.

I have enlarged my figures below and you can see they match.
The throat angle is twice your 36.87°. That is where my 73.74° came from.

So my question still is:
Is the force on the whipping 75% or half that (ie 37.5%) because you are dealing with a loop?
This is the issue I am a bit unclear about. I opted for 75%. It is possibly half this.

As Stu points out, with whipping this would halve again.

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Old 28-07-2016, 11:25   #30
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Re: whipping - antal method - low friction ring

If the force at the throat pulling it horizontally apart is 75% of the total load you apply to the system, this is mind boggling.
Even 37.5 % is massive if this is what it is with a loop strop.

If this halves with whipping, to me 18.75% of the load is still a lot for a very thin cord of dyneema to handle. This sounds like the more likely amount to me the more I mull it over.

I can't possibly imagine how the throat copes with that long term, even if it initially holds to the SWL specified by Antal.

The Bullseye, which completely avoids this peeling while retaining the ring as snuggly, is sounding better and better .
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