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Old 28-07-2016, 12:02   #31
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Re: whipping - antal method - low friction ring

Quote:
Originally Posted by Seaworthy Lass View Post
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.
The force trying to put the splice apart is 37.5% each side, equal and opposite. So if you imagine all the force will end up on the last loop of whipping then it would be half that again on the whipping twine.
Though what might be an issue is not just the whipping, but the small radius formed by the whipping which the main dyneema will be subject to. Dyneema has so little stretch that when going round under a small radius all the load can end up on just a few fibres.
But again we're pretty much guessing here, fun though it is
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Old 28-07-2016, 12:13   #32
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Re: whipping - antal method - low friction ring

I did manage to have a conversation with a nice guy at antal - just before all of antal Italy left to take the whole month of august off. . . . he explained how they terminate the two ends.

One end is how I explained above - it is tied around the ring several times, then taken under a strand of the main dyneema strop, and initially not pulled tight, left with a loop sticking out.

The other end - the one that is used to work the half hitches up the body, is finally half hitched to just one strand of the main strop (rather than around both like in the body of the whipping), then it is tucked under/thru the loop left from the other strand (and described just above). Finally that other end is pulled tight and both ends are clipped short and tucked under the ring.

So both ends finish with a couple half hitches that are not stressed (one around the ring, and the other around only one strand of the strop). Then both are tucked/trapped under (one under a strand of the main strop, and the other under this first end).

Quote:
Originally Posted by classic1899 View Post
not sure why all the surprise and wonder this particular technology has been in existence for a few hundred years
This whipping/seizing of antal's is a bit different than the classic/traditional whipping/seizing. The half hitch body is the same. But the tie around the ring and how the ends are terminated is different. I was curious how they did it, because the loads are significant on the whipping..

So it is more a matter of figuring how to handle the higher loads that the new materials allow, rather than surprise/wonder at the basic concepts.
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Old 28-07-2016, 12:26   #33
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Re: whipping - antal method - low friction ring

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Originally Posted by conachair View Post
The force trying to put the splice apart is 37.5% each side, equal and opposite. So if you imagine all the force will end up on the last loop of whipping then it would be half that again on the whipping twine.
Though what might be an issue is not just the whipping, but the small radius formed by the whipping which the main dyneema will be subject to. Dyneema has so little stretch that when going round under a small radius all the load can end up on just a few fibres.
But again we're pretty much guessing here, fun though it is
A huge thanks for clarifying that .

That resolves a big issue for me. The maths was simple, but the physics was doing my head in regarding what to do with the 75%. Also, until Stu brought it up I had forgotten the whipping was circular and would halve that again.

I am comfortable hopping off the fence and making the load on the dyneema cord 18.75%.

With Antal's listed SWL of 700 kg for this strop, that is a 131 kg essentially on one strand of what looks like 1 mm dyneema (breaking strain around 195 kg?). I can't see how they have rated their strop to 700 kg,

I agree with the concern with what this is doing to the main dyneema strop. I made this comment earlier about the potential damage as the whipping cuts into it. I made this comment back in post #23:

Quote:
Originally Posted by Seaworthy Lass View Post
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.
To me, whipping does not look like a very favourable way at all of retaining a LF ring at all .

SWL
PS yes, it is great fun .
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Old 28-07-2016, 12:51   #34
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Re: whipping - antal method - low friction ring

Conachair, while I am on a roll with getting help , in the other thread on the Bullseye I posted this diagram yesterday and asked if it was correct (I was just about on my knees begging for a response, but the silence has been deafening):


This issue is important, as it partly explains why the throat of the Bullseye seems to be so little stressed under load.

SWL
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Old 28-07-2016, 13:02   #35
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Re: whipping - antal method - low friction ring

By the way, if anyone has not seen how the Bullseye weave retains a LF ring yet, this is it.

No whipping of any other kind of additional binding or lacing is required. It is dead easy to weave:
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Old 28-07-2016, 18:58   #36
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Re: whipping - antal method - low friction ring

I have woken up and I am back on the fence again LOL.

It seems the light goes on, then flickers out on this issue. At least some of the lights that have come on in the last couple of days are staying on. I was groping around in inky darkness before .

My mind keeps returning to the thought that the throat is an enclosed system. I don't know if this this the right term, but it has no idea how the load on it is being applied. You could be pulling with one bit of line, or somehow magically attached ten and pulling on those. The load on each of those pulling lines is of course affected, halving if you have a loop strop rather than a single line.

So, with this thought in mind, if you pull on the throat x amount, each leg is being forced out by 37.5%, so I am back to thinking the total force at the base pulling the whipping apart, is 75% of the applied load.

I have gone back and reread Conachair's last post more carefully and I now interpret that as 75% also. Conachair, is that correct? The 75% seemed so improbably high, my mind was happier accepting the lower figure .

Evans, is the theoretical force pulling the whipping apart 75% or 37.5% of the load applied for the Antal strop you are dissecting?

ie If you apply in this case Antal's stated SWL of 700kg, is there 525 or 262.5 kg of force pulling the base of the throat apart? We have at least decided the whipping line takes half whatever it is, as it is a loop.

SWL
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Old 28-07-2016, 20:35   #37
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Re: whipping - antal method - low friction ring

Quote:
Originally Posted by Seaworthy Lass View Post

With Antal's listed SWL of 700 kg for this strop, that is a 131 kg essentially on one strand of what looks like 1 mm dyneema (breaking strain around 195 kg?). I can't see how they have rated their strop to 700 kg,
Antal use a 3:1 safety factor for they Safe Working Load's.

If you are calculating a failure mode below their SWL, then I will politely suggest it is rather more likely that your calculation is (quite) wrong than that their product will fail below SWL.

They actually have a quite good testing lab - I did some work with their lab on a superyacht project.
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Old 28-07-2016, 21:22   #38
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Re: whipping - antal method - low friction ring

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Antal use a 3:1 safety factor for they Safe Working Load's.

If you are calculating a failure mode below their SWL, then I will politely suggest it is rather more likely that your calculation is (quite) wrong than that their product will fail below SWL.

They actually have a quite good testing lab - I did some work with their lab on a superyacht project.
I am not calculating a failure mode below their SWL, but I have my doubts they are leaving a safety factor of at least 3 x breaking strain, if tested after the system has been taken to the SWL for an extended time. I have no idea what "extended time" is suitable, but maybe what you would expect with a month or two of use? The strops should be able to maintain their strength for a few months use. Maybe plan to discard after 6 months if loads close to the SWL or snatch loads have been applied? All this is guesswork, but in my view the stated SWL should not be just for when a strap is brand new and being used for the first time. There should be a decent reserve left when its usable life has been reached.
The concept of the whipping cutting into the dyneema strop (which is spliced in this area and the outer covering is stretched) even at the lowest figure we are discussing does not sit comfortably with me. I suspect problems have not cropped up as people are not using these strops at anything near the SWL.

Yes, I know extremely little about this and I have made appalling errors since I started looking at this a few days ago, as you have witnessed. I am stumbling about awfully. I fully acknowledge my calculations could be entirely wrong, although Conachair came up with exactly the same figures. What I am unclear about at the moment is how the theoretical 37.5% horizontal force is applied if it is correct. Is the theoretical force pulling the whipping apart 37.5% of the load applied or 75%?

I know this situation is complex and there is a lot more at play, but it would be nice to resolve the above simple issue. What are your thoughts?

SWL

Edited to add: Some tables giving dyneema breaking strains recommend:
"Working loads must never exceed 20% of the strengths show in the table"
"Variations up to 25% can occur with short lengths"

ie SWL when dealing with dyneema should be 5:1
I know very little about this, but in a situation where the whipping is subjecting a huge force on the dyneema strop at the throat, using a SWL of 3:1 possibly tested on brand new unused strops, seems very skimpy to me. Does this sit comfortably with you?
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Old 28-07-2016, 22:54   #39
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Re: whipping - antal method - low friction ring

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Originally Posted by Seaworthy Lass View Post
So, with this thought in mind, if you pull on the throat x amount, each leg is being forced out by 37.5%, so I am back to thinking the total force at the base pulling the whipping apart, is 75% of the applied load.

I have gone back and reread Conachair's last post more carefully and I now interpret that as 75% also. Conachair, is that correct?
It's 37.5%. Picture someone holding a 37.5kg weight on a rope, the guy is pulling up 37.5kg on the rope and the weight is being pulled down 37.5kg by gravity, equal and opposite forces but the rope still only sees a tension of 37.5kg.
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Old 28-07-2016, 23:22   #40
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Re: whipping - antal method - low friction ring

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It's 37.5%. Picture someone holding a 37.5kg weight on a rope, the guy is pulling up 37.5kg on the rope and the weight is being pulled down 37.5kg by gravity, equal and opposite forces but the rope still only sees a tension of 37.5kg.
How does that translate to a tug of war situation with ropes connected to an object in the middle? To me that is more akin to what is happening here.
If one side is pulling 37.5 kg (in this case like one leg of the loop going around the ring) and the other group is pulling the opposite way with exactly the same force (the other leg of the loop), wouldn't the force splitting the object apart be 75 kg?
I am not arguing you are wrong, I just don't understand why the tug of war situation does not apply.
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Old 28-07-2016, 23:44   #41
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Re: whipping - antal method - low friction ring

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Originally Posted by Seaworthy Lass View Post
How does that translate to a tug of war situation with ropes connected to an object in the middle? To me that is more akin to what is happening here.
If one side is pulling 37.5 kg (in this case like one leg of the loop going around the ring) and the other group is pulling the opposite way with exactly the same force (the other leg of the loop), wouldn't the force splitting the object apart be 75 kg?
I am not arguing you are wrong, I just don't understand why the tug of war situation does not apply.
It's the same force at each end, the centre of thebwhipping doesn't know if it's getting pulled apart at each end or if it's tied to a wall, it just sees the 37.5kg force..

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Old 29-07-2016, 01:03   #42
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Re: whipping - antal method - low friction ring

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It's the same force at each end, the centre of thebwhipping doesn't know if it's getting pulled apart at each end or if it's tied to a wall, it just sees the 37.5kg force..
Extra bright light just went on .

Theoretically then, if the SWL of 700 kg is applied to Antal's strop with a 10/7 ring, the force pulling the whipping apart is a whopping 262.5 kg.
The figure may be a bit different if the inner bit of the throat is not in the position I drew, but if would have to be very close or the ring could be forced off. I find that figure mind boggling!

And this is just a small ring, Antal are using whipping on 6mm dyneema around their 20 mm rings, where the forces get high.

I would personally prefer to use a different method of restraining the ring with the high loads we are discussing.

The Bullseye weave needs to be load tested, but is looking extremely promising. The force is dramatically less at the throat, as the throat ratio is around 2, but snug capture is still enabled due to the criss crossing of the weave. Also, the crossing lines result in something akin to the situation I sketched in post # 34 applying, so the horizontal force is less.
The resulting horizontal force then compresses the line to hold the throat in place, rather than tearing it apart.

Is anyone able to do any load tests? Sailors using LF rings would find the Bullseye very useful I think and LF rings are coming into use more and more, not just for people racing, but for cruisers, as they are simple (no moving parts to go wrong), lightweight, amazingly strong and super cheap compared to blocks. The friction is obviously greater than with blocks and they have other limitations, but they are brilliant in the right application.

Manufacturers such as Antal would be interested as well I bet in the Bullseye, as these are dead simple to produce. Much easier than all that complex whipping they are doing. I guess if any manufacturers start using this system, there is a reasonable chance it is OK .

I am confident enough that I am using a soft shackle version of this on our yankee sheet (made with 6mm dyneema and a 25mm LF ring) and, as we have a 47' boat, it is being given a decent workout. So far it is performing very well. The LF ring is not great in this application (friction too high), but I just want to see how it handles itself under load, plus with flogging and panting of the sails.

By the way, I have zero commercial interest in producing any of these.
The instructions can be found here, with the caution this has not been tested:

Unveiling Bullseye Strops (eg for low friction rings)

Conachair many, many thanks for your help .

SWL x
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Old 29-07-2016, 01:32   #43
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Re: whipping - antal method - low friction ring

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Originally Posted by Seaworthy Lass View Post
Manufacturers such as Antal would be interested as well I bet in the Bullseye, as these are dead simple to produce. Much easier than all that complex whipping they are doing. I guess if any manufacturers start using this system, there is a reasonable chance it is OK .
Apply for a patent. Now!
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Old 29-07-2016, 01:44   #44
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Re: whipping - antal method - low friction ring

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Apply for a patent. Now!
LOL! Knots don't belong to anyone.

Maybe Antal will send me a few LF rings as a thank you and share their load testing data with all of us

SWL
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Old 29-07-2016, 01:57   #45
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Re: whipping - antal method - low friction ring

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LOL! Knots don't belong to anyone.
I'm of like mind with StuM.


I'm astounded at your superb work, your effort, and your attitude to sharing, Seaworthy Lass. You're fantastic! Simply wonderful.


I agree that knots cannot be patented in practice.


Terms, such as 'Bullseye strop', can be trademarked. And trademarks can be licensed to a manufacturer.


In many jurisdictions, designs can be protected by a design patent (Noelex will tell you that many anchors, such as the Rocna, were protected with design patents for reasons including the difficulty of demonstrating the uniqueness of their features).
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