whipping - antal method - low friction ring

[Seaworthy Lass]

Originally Posted by Alan Mighty

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).

Alan, thank you for your very kind words. I am blushing here .

If load test come up trumps, I would love it if sailors and cruisers would benefit from the Bullseye and I would not want it trademarked to one manufacturer, although they too should use the best designs, as we are the consumers of their goods.

Although I came up with the design itself entirely on my own, it was a community effort getting me there:

Worldwide, a huge amount of work has been put into designing and testing dyneema soft shackles and splices, without which this weave would be only decorative.

Specifically though:
StuM initially sparked my interest in knots several years ago and patiently answered many of my questions in those early days.
Dockhead provided the initial impetus for me to try and improve what we currently had with dyneema strops and he reported how his own system was working and what had failed and tested a system of lacing (I am still trying to entice him away from it LOL).
Without Evan's load testing data document I would not have known what limited systems when lines went around bends and also when throats were created. Plus all the general data on failure modes of various soft shackles and splices etc. was invaluable background information. He answered a heap of questions when I was struggling to interpret his data correctly and shared his experinces.
Both Dockhead and Evans would have spent hours posting on the subject of strops in the last 3 recent threads on this.
Members such as CruisingScotts shared what they were doing and provided very useful constructive criticism of earlier restraining designs using lacing, which sent me off on a quest for a completely different system not involving whipping or lacing or gluing. So few people seem to be prepared to chip in with their views, and I think pointing out flaws is vital in being able to progress rapidly.
My husband was fantastic through all this.

I did not come up with the name, even that was a team effort, with you playing a large part. Dockhead finally came up with the idea of incorporating the name "Bullseye" after a comment Stu made. Nice he got to name it after starting all this .

I am very grateful to Conachair who checked figures for me in this thread. This was not the first time he has generously provided vital help. Given I had made so many errors in the early stages of trying to understand load issues, once I finally grasped a little of the basics, I was at the head banging stage, as no one was responding to any of my questions any longer. I just didn't know if I was on the right track. I think I had worn everyone out . Physics is clearly not my forte.

So this was not a solo effort. I do not want the use of the Bullseye to be restricted.

There are 3 strops I have incorporated the Bullseye in at the moment - a soft shackle, and two loops, one for a single LF ring and one for what I think is a very simple elegant solution to combining two. I have more ideas, just not enough time to try them out yet.

SWL

[estarzinger]

Originally Posted by Seaworthy Lass

I have my doubts

Does this sit comfortably with you?

I sent you a PM.

........................................

Back to the discussion of how the antal whipping is constructed . . . . I got a follow up e-mail from Antal this morning with this thought/comment ". I give you tip, it is useful during construction if you use a bit of spray glue on the line."

[Seaworthy Lass]

Evans, the same standards apply to PMs, as they do to posts.

---------

Antal's strops could conceivably be used in situations where their SWLs are approached for long periods, particularly by racers who are keen on reducing weight.

As you have not corrected the theoretical calculation put forward here that the tension on the whipping is 37% of the load for the Antal 10/7 ring with loop, I can only assume it is roughly correct. The throat angle could be a touch higher, reducing this figure, but not by much or the ring could be forced off.
If this theoretical figure is not correct, what is the right one? I fully realize there could be an error here, although another member has also come up with this result.

If the calculation is correct, these are the figures for two loops with rings Antal is producing:

Antal 10/7 ring with 4.5 mm dyneema loop: Antal state SWL of 700 kg of the system
Calculated tension at whipping = 37.5%, therefore 262 kg at SWL

Antal 14/10 ring with 6 mm dyneema loop: Antal state SWL of 1500 kg of system.
Calculated tension at whipping = 32.3%, therefore 485 kg at SWL


The following is only my personal opinion and I have zero expertise in this area:

Firstly: As I stated earlier, it concerns me what the effect this force on the whipping will have after prolonged use. In my opinion the whipping is going to weaken the dyneema fibres with time, particularly since the loop is being strongly forced apart and constrained by thin whipping.

Antal do not state expected life for these, but Tye Tec, who don't use whipping, recommend replacement after 3 years for their systems with dyneema and low friction devices.

Secondly: The figure Antal have stated for the SWL for their 14/10 ring with loop bothers me too. Looking at a few brands using SK75 dyneema, they list breaking loads of approximately 3300-4200 kg. Dynex Dux has a breaking load of 6800 kg according to online data. I don't know what kind of Dyneema they are using, but it does not look like the latter.

In a perfect loop the system strength theoretically doubles if there is nothing else restricting a loop, but, as I understand, your load tests showed that looping a loop around an object with a diameter the same as the dyneema reduces the system strength by 50% to 100% of line tensile strength (95% in practice), and cow hitching decreases this to 85% of line tensile strength. Antal do not state what you can attach it to, but taking using D/d of 1:1 would not be too conservative in my opinion.

So the system strength of a loop using 6mm dyneema and cow hitching it to something with a diameter the same as the dyneema is anywhere from around 2800 to 3600 kg with standard SK75 (ie from 3300 to 4200 x 85%).

Antal have given their 14/10 ring with a 6 mm dyneema loop a SWL of 1500 kg. They show an image of it cow hitched and give length when cow hitched. The system seems to have been designed to be cow hitched.
Are they using some kind of exotic dyneema? If standard SK75 dyneema is being used, assuming a bend ratio of 1:1 (and this is not worst case scenario) I can't see how this was load tested to 4500 kg.

Evans, I accept Antal have a very good testing laboratory and they are using a SWL based on one third of the breaking strain they measured for these loops with rings, but the above two points bother me.

SWL

Antal's data for their 14/10 ring with a 6 mm dyneema loop:

[Benz]

Coming in late here, as usual. Attached is a pic of the solution I have come up with for avoiding having to lash to a ring. Not having seen it before, I have named it the "Euler Loop," after the guy who popularized our infinity symbol (it kinda resembles it).
Having only one leg of line, as it were, around the ring, you can use the maximum thickness the ring will take. The brummeled eye can be spliced around a shackle instead of a ring if desired, or be just a loop that will accept toggles (or 'dogbones' as some folk wrongly call them).
If a whipping at the crossover, as shown in the second picture, is undesirable, you can grog it there, but I'm not perfectly comfortable with the way the grog method distorts the line.
I have put step-by-step directions to making these on my website. They're really super-easy, and I've already incorporated half a dozen into my boat.
Ben Zartman

[estarzinger]

Originally Posted by Seaworthy Lass

Evans, the same standards apply to PMs, as they do to posts.

Ok, you want me to say in public what I said by PM . . . . I would be happy to post the full texts or you can . . . . below is a succinct summary.

As you have not corrected the theoretical calculation...., I can only assume it is roughly correct.

LOL - I honestly thought only school children used that rhetorical taunt.

I explained in my PM to you that (1) you know everything that you need to know to make a correct assessment of the whipping, (2) that your current assessment is incorrect, and (3) I was tired and it was no longer fun to try to teach you to fish.

And lol - you tearing into those 1:1 bends in the bullseye like you are the Antal design?

............

[Seaworthy Lass]

Originally Posted by estarzinger

LOL - I honestly thought only school children used that rhetorical taunt.

I explained in my PM to you that (1) you know everything that you need to know to make a correct assessment of the whipping, (2) that your current assessment is incorrect, and (3) I was tired and it was no longer fun to try to teach you to fish.

And lol - you tearing into those 1:1 bends in the bullseye like you are the Antal design?

Evans, it was not taunt. It was a serious request for help on these load issues.
We are all here to help each other. This is your area of expertise and I am not the only novice on CF in regard to load issues. Members would benefit from knowing what percentage of the load was acting perpendicularly on the whipping.

I am not sure why you are raising the issue of the Bullseye if you do not want it mentioned on this thread, but your comment requires a response:
Regarding the 1:1 bend ratios at the attachment point, I stated earlier that the Bullseye loop strop and the Antal loop with whipping would have exactly the same SWL, as both are limited by the cow hitch at the attachment point. I even put it in bold, so people would not miss this point:

Originally Posted by Seaworthy Lass

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.

The possible 1:1 bend ratio at the attachment point has absolutely nothing to do with the loads at the throat of either design and nothing to do with the likely longevity, which is my primary concern with the whipping.

SWL

[estarzinger]

Originally Posted by Seaworthy Lass

Regarding the 1:1 bend ratios at the attachment point, I stated earlier that the Bullseye loop strop and the Antal loop with whipping would have exactly the same SWL, as both are limited by the cow hitch at the attachment point.

you are not reading carefully.

I was not referring to the 1:1 at the attachment point.

I was referring to the 1:1 where the strands cross each other on the way to the ring. I called this a 'low deflection 1:1' in my PM to you, and said that I did no testing on this but that samson says even a 10 degree deflection had bend ratio issue.



regarding some of your "Opinions" (from your post above) . . . you probably need to study up on fatigue which we have not discussed much. And UV, which will effect all these dyneema constructions.

In any case . . . . I am now completely done here.

[Seaworthy Lass]

I have looked at the Samson website, which refers to issues regarding rope deflection over 10°. I can see nothing to suggest these figures apply to dyneema. Dyneema does not behave in the same manner as other rope when it comes to bending.

The only comment I can make is that the Bullseye has 4 lines at the throat in the design, not two, so whatever the loads are imposed due to slight deflection, they would be halved.

Load testing would reveal more.

In the same section Samson recommend a throat ratio of no less than 3:1 and preferably 5:1. Again, these high figures may be due to the fact that they do not specifically apply to dyneema.

Although these actual forces wanting to "tear" the throat apart (as Samson aptly describe it) do not depend on the type of fibre, how the fibre handles it probably will. So a throat ratio of 5 : 1 that Samson say is preferable, may be not be necessary for dyneema (just speculating here).

Regardless, with about a third of the applied load acting directly on the whipping if the throat of dyneema is clenched tightly using Antal rings (if our calculations here are correct), I think my concerns about tight whipping with a 1.3 : 1 throat ratio using thin dyneema are not unfounded when it comes to longevity with prolonged use, particularly close to safe working loads.

SWL

[Seaworthy Lass]

Getting back to the whipping Antal uses.

I have played with the calculations and derived a formula to calculate the force trying to "tear" the throat apart, expressed as a percentage on the total force applied when the dyneema is clenched exactly at the edge of a low friction ring by whipping.

Lets call this force F

You just need two figures for any low friction ring to work this out:

D = overall diameter of LF ring
B = diameter of the LF ring where the dyneema sits
X = B/D

F = 50X / square root of (1 - X squared)

I think this is correct. Neat, isn't it . Nothing needed other than a basic calculator.
I will show how I worked this out in the next post.
You can use this formula for any low friction ring.

[Cruisingscotts]

SWl, although it is a impressive effort you are putting into dissecting this, I think you are probably trying to apply too finite logic to the application. Most things marine especially on boat and anything racing operate in the relm of fuzzy logic. There are far too many unknown and variable factors to try and use a constant calculation for a single loading scenerio. In your other thread you were on the right track. Most times things are setup on a sliding scale of "best practices" known static and tested loading factors and charactoristics with the largest safety margin for the practical application. On a cruising boat several hundered percent, a racing crusiing boat moving to the middle somewhat and true racing running right up to the line. If you look at the evolution of application of hi mod lines, although there is plenty of lab work a majority of it is "try it till it breaks than adjust". The cruising boat is constantly reaping the windfall of racers breaking things....

[Paul Elliott]

Originally Posted by Seaworthy Lass

Getting back to the whipping Antal uses.

I have played with the calculations and derived a formula to calculate the force trying to "tear" the throat apart, expressed as a percentage on the total force applied when the dyneema is clenched exactly at the edge of a low friction ring by whipping.

Lets call this force F

You just need two figures for any low friction ring to work this out:

D = overall diameter of LF ring
B = diameter of the LF ring where the dyneema sits
X = B/D

F = 50X / square root of (1 - X squared)

I think this is correct. Neat, isn't it . Nothing needed other than a basic calculator.
I will show how I worked this out in the next post.
You can use this formula for any low friction ring.

Perhaps the force F isn't concentrated at one point as you have shown. I think that the whipping, even though very low stretch, will take on a radiused shape that distributes force F over a non-zero length of the throat. While the total value of F will be as you have calculated, the bend radius and reduced point loads will much improve the load capacity and wear characteristics of the eye.

[Seaworthy Lass]

Originally Posted by Paul Elliott

Perhaps the force F isn't concentrated at one point as you have shown. I think that the whipping, even though very low stretch, will take on a radiused shape that distributes force F over a non-zero length of the throat. While the total value of F will be as you have calculated, the bend radius and reduced point loads will much improve the load capacity and wear characteristics of the eye.

Yes, I agree the issue is going to be complex and all sorts of factors I have no knowledge of are very likely going to come into play.

But the bottom line is that loads are high when the throat is tightly clenched at the ring edge.

One thing to consider is that under load a throat will move down, possibly quite considerably (not simply because of slight stretch, but because compression of the splice will occur). This will increase throat ratio and at these low throat ratios we are discussing, even a small shift causes the force at the throat to decrease quite a bit.
I have just done a quick calculation using the formula above and if the throat shifts down 3mm using the ring and loop in the first post, then the effective diameter is 6mm larger, making X = 15/31 = 0.484
The theoretical horizontal force acting on the whipping instantly changes from 37.5% to 27.65%. A huge shift.

Regardless, I think that there is no doubt that the loads on the throat are considerable if the throat is clenched tightly. The formula above is extremely useful in getting some idea what difference it makes if it is loosened a bit.

• In his loops on LF rings, CruisingScotts with the aim of increasing the throat ratio, is using a loose, wide whipping, knotted in the centre. Photos are on Dockhead's recent thread.

• Evans has said he is using a technique of 3M tape plus stitching to do the same.

• Dockhead, with the high loads on his 54 footer's twing system, found his homemade whipping pulled apart and he is trialling a form of lacing to give a very large throat ratio.

It is an issue that is of concern when loads on the system are high.
I do not believe that clenching a low friction ring right at the rim is the best practice and I am not alone in this assessment, particularly if thin whipping is used that could in time cut into the dyneema it is clenching tightly.

If this is currently working on racing boats, then I put forward the hypothesis that the loads on these particular systems are well below the SWL. With the high strength of dyneema, it is often possible to achieve this with a negligible weight increase.

SWL

PS I will post the working out for the formula tomorrow.

[Seaworthy Lass]

Originally Posted by Seaworthy Lass

Getting back to the whipping Antal uses.

I have played with the calculations and derived a formula to calculate the force trying to "tear" the throat apart, expressed as a percentage on the total force applied when the dyneema is clenched exactly at the edge of a low friction ring by whipping.

Lets call this force F

You just need two figures for any low friction ring to work this out:

D = overall diameter of LF ring
B = diameter of the LF ring where the dyneema sits
X = B/D

F = 50X / square root of (1 - X squared)

I think this is correct. Neat, isn't it . Nothing needed other than a basic calculator.
I will show how I worked this out in the next post.
You can use this formula for any low friction ring.

I have attached my working out below.

The formula for horizontal load on the system, expressed as a percentage of the total load, applies not just to low friction rings.

[Seaworthy Lass]

Hi all

I have made up a spread sheet showing how I think the horizontal force at the throat (expressed as a % of the total load) goes up as the throat ratio decreases (throat angle increases) when a throat is clenched at the edge of the ring by any means. Figures have been rounded off to the closest whole number.

For any LF ring you can just take the diameter of the low friction ring and the diameter of the bit the dyneema is going over inside the flange, divide the small number into the big one (=D/B) and look up the results.

It is very interesting seeing how the sharp rise is and how little benefit there is to increasing the throat ratio once it gets past about 3:1.

It seems some kind of load sharing will occur rather than it hitting one point, but regardless, it is a huge amount for the dyneema to deal with. This figure is not just theoretical, as far as I am aware.

It really hits home that it is preferable to find some means of securing a ring that does not involve clenching it tightly. Several CF members I know of are doing this already when they make up these strops for themselves (Estarzinger, Dockhead and CruisingScotts).

Also, that there is a clear need for a manufacturer to produce a LF ring in the shape of a continuous thimble. It would solve this problem instantly. It is not as if dealing with throat angles is a new issue. We have been using thimbles on eye splices for a "little" while now and there is no need to try and reinvent the wheel .


Could someone knowledgable in this area please check this table? .
It is just based on diagrams provided by Estarzinger in a previous thread and calculations confirmed by Conachair in this thread. I have no expertise in this area.
I will modify the table if it is incorrect.

[nigel1]

Regarding shaping the LF ring more in the shape of the traditional pear shaped thimble.
My thoughts are that the LF rings are probably machined, turned up on a lathe, which would reduce the time needed to smooth the ring.
I wonder if a separate rounded top wedge shaped piece could be molded, and then fitted on the ring.
If the top of the wedge was made with a convex top, and the two sides concave, a snug fit could be achieved and then held in place with a suitable whipping or seizing.

When I did my apprenticeship, we had to be competent in the making of pilot ladders. Above and below the each step, where the ropes passed through, wooden wedges were fitted and then a seizing made around the ropes to hold the wedges in place.



For some reason, in the UK, these wedges were known as winnets, I never discovered how they got this name, (I do know the other meaning for winnet), but the term is still used.
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