Low Friction Ring strop methods survey

[Breaking Waves]

Originally Posted by Seaworthy Lass

Load testing results on cow hitched loops have already shown this.

source?

Im just not sure what argument you are making ... of course all solutions, including the soft shackle, will be weaker when put around a smaller bend if that is where they are already breaking. The cow hitch testing I have seen has mostly been rope around rope (as in joining two) which has different dynamics than what we are talking about here - you have compression issues there which this case does not.

Originally Posted by Seaworthy Lass

Given nothing failed at the LF ring end for all five samples you constructed,

in fact the cow hitched one failed at the ring lol . . . but because it caused ring deformation rather than line weakness.

[Seaworthy Lass]

Originally Posted by Breaking Waves

out of curiosity "these loops are often cow hitched in situations where the diameter of the attachment point is about the same as the line diameter, or at least not much more." you are saying that a pad eye rated to 9500lbs would have a bail 3/16" or smaller? Do you want to double check that for me, please.

You are correct. The pad eye is then the weak point in the system . I have heard cruisers complain of these ripping out of the deck (more commonly than breaking), so the strength of the attachment point and how it is secured does need serious consideration.

The soft shackles or loops (none cow hitched) with or without LF rings that take the highest loads on board our boat are all attached to the toe rail, which has a diameter of 36mm (D/d of around 5:1 or 7:1 depending on line diameter), so bending losses there are not the weak part of the system.

However, if loops were cow hitched onto this same toe rail (as the loops with LF rings would be), given there are bends that are somewhere between 1:1 and 2:1 in the cow hitch itself, I think breaking strength is likely to drop to very roughly 50% system strength. A soft shackle will not see this.

SWL

[Breaking Waves]

^^

As I said to dockhead recently: perhaps, perhaps not, testing would reveal

I can and have speculated with the best, but I learn something new from almost every test I do (which means my speculation, which is decently informed, was often wrong).

I do like the soft shackle base to the strop.

[Seaworthy Lass]

Originally Posted by Breaking Waves

source?

Evans Starzinger.

I bet you are now going to ask where and make me hunt for hours .
It may be that I am remembering incorrectly, but in one thread on CF a few years ago I recall him discussing a figure of 42% of system strength for full loops (85% for eye spliced loops) when cow hitched on.

Originally Posted by Breaking Waves

Im just not sure what argument you are making ... of course all solutions, including the soft shackle, will be weaker when put around a smaller bend if that is where they are already breaking. The cow hitch testing I have seen has mostly been rope around rope (as in joining two) which has different dynamics than what we are talking about here - you have compression issues there which this case does not.

Not an argument at all, I am just pointing out that in practice these loops are generally cow hitched onto attachment points that are not huge in diameter. The main point I was making (or trying to make ) is that system strength will decrease much more for a loop compared to a soft shackle, as there are only two legs in the former and four in the latter.

Apart from the added complexity of construction (not actually much harder if someone already makes soft shackles) I think soft shackles are a much better option for retaining LF rings rather than loops. Construction cost is lower, they can be significantly shorter, they are removable with the line still passing through and time taken is not much more than for the loops retaining LF rings. Bonuses all around .

A few of the designs you made up could be incorporated into soft shackles, it is not just the Bullseye weave.

Originally Posted by Breaking Waves

in fact the cow hitched one failed at the ring lol . . . but because it caused ring deformation rather than line weakness.

That is a surprise for me! (The whipped one also performed much better than expected).

Given the dyneema was probably bending between 1:1 and 2:1 in the cow hitch on the ring side, why do you think the failure of the loop was still at the pin end where the bend was nearly 4:1?

Edited to add: is it because the portion around the ring is a form of an additional loop, so loads seen in that portion are halved? Late at night here and my mind is getting fuzzy.

SWL

[Seaworthy Lass]

Originally Posted by Breaking Waves

source?

Bingo!
I found it.

There was initially some confusion in this discussion (mainly on my part) between loops on eye splices and full loops (and as well % of system strength or % of line strength being referred to when strength was discussed), but here is the reference. As the system loss with a 1:1 bend without any cow hitch is already around 50%, the 85% strength referred to here must be % of line strength (where maximum system strength is 200% line strength):

Originally Posted by estarzinger

This is a bit more complicated that that - for instance if a loop is around a 1:1 padeye, the strength is 100% (or 95%). But if that loop is around a payeye in a cowhitch it would be 85%.

I will call it quits for tonight as matchsticks are holding my eyes open (late at night on top of a couple of long flights).
Thanks for the interesting discussion.

SWL

[Breaking Waves]

^^

Searched that website and don’t see any specific cow hitch testing. So guessing that comment is simply picking up Samson’s comment on rope to rope connections.

Not saying it is wrong, but I am not sure it is right. This rope to metal connection we are talking about has several different physical characteristics.

It is tricky to abstract those sorts of comments to different situations, without knowing the specifics of what they tested and the results detailed. The 3:1 and throat tearing comments are an example. I am sure there is something to that, but we did not see it in these high angle splices and the Huston boys said they had never seen a throat tear. Logically you can see how it might happen, but I don’t think either of us know in what particular situation it could.

Bottom line, I am happy to speculate but reluctant to draw a conclusion without testing. I’v just Ben “educated by the results” too often.

When you get a moment, would you please give me an easy link to the instructions for the soft shackle bullseye. I’m trying to decide if it is worthwhile having the boys do another test run, but if I do that should certainly be included. My lazy half is telling me that our focus on strength is misguided - these are already strong and going up in size will make then strong as anyone wants - so strength might be a diminishing returns focus and ease of construction and use might be more important.

[Breaking Waves]

Out of curiosity - what size line are people using when they make (or buy) low friction ring strops?

And do you have any expectation for working or breaking load? (Might be reference to the load capacity of a block which the ring replaces).

Just trying to get a sense what sort of ballpark is the sweet spot for design and testing.

[Seaworthy Lass]

Jet lag keeping me awake so I am up again. No point lying there counting sheep .

Originally Posted by Breaking Waves

^^

Searched that website and don’t see any specific cow hitch testing. So guessing that comment is simply picking up Samson’s comment on rope to rope connections.

Not saying it is wrong, but I am not sure it is right. This rope to metal connection we are talking about has several different physical characteristics.

Ah, I took that comment as gospel .

Samson’s comments must be based on something they found though, so I would not be quick to dismiss this.

Originally Posted by Breaking Waves

It is tricky to abstract those sorts of comments to different situations, without knowing the specifics of what they tested and the results detailed. The 3:1 and throat tearing comments are an example. I am sure there is something to that, but we did not see it in these high angle splices and the Huston boys said they had never seen a throat tear. Logically you can see how it might happen, but I don’t think either of us know in what particular situation it could.

Bottom line, I am happy to speculate but reluctant to draw a conclusion without testing. I’v just Ben “educated by the results” too often.

Yes, I agree. I was very surprised the buries did not tearat the throat in your middle sample.

There are so many variables though, that I have found it best not to take figures as definitive, even when statistically significant. For example, if the study Thinwater presented a link to recently is anything to go by, results are likely to vary dramatically depending on line diameter being tested and that is not even taking very thin line into consideration.

Also, any trial only gives data for the unique set of not only parameters, but testing conditions. Real world conditions can be very different. For example, these rings are not simply loaded to near maximum strength once in otherwise static conditions. These strops will sometimes be subject to flogging, often be subject to moderately high loads for long periods, etc etc. So although test data is invaluable and all we have to go by other than reports of usage (also invaluable, but not under contolled conditions), we need to be careful about making absolute judgements.

Originally Posted by Breaking Waves

When you get a moment, would you please give me an easy link to the instructions for the soft shackle bullseye. I’m trying to decide if it is worthwhile having the boys do another test run, but if I do that should certainly be included.

The instructions are in post # 43 here:
http://www.cruisersforum.com/forums/...-169764-2.html

If a soft shackle strop vs a loop strop is tested with these rings it would be good to use a LF most people are using with 5mm UHMWPE. I am using a much larger ring (25 hole diameter) than you used. As two lots of line need to go around the rim with the weave, I have found 5 or 6 mm line sits super neatly (8 mm is jammed up in not a nice looking way). Also a larger ring just seems to function more smoothly (may be imagination). I think Dockhead is also using larger rings than needed. I have no idea what others are doing, but feedback would be helpful.

The other big variable is what attachment point size to select for the trial. Something used most commonly would be useful as well (feedback from others would be good here too).
I guess the 36 mm toe rail I am using to attach these is not common and selecting a smaller diameter may give more useful data?

Also what was the spread of results in this last trial? Were 3 samples enough to provide statistcally significant results?

I am happy to help here make up some samples for testing, but I am restricted to using 5mm Stealth Super 12 as it is all I have in a reasonable quantity on board at the moment.
It is heat treated though (both when coating the strands then again after braiding) and the coating is unlike anything I have handled with dyneema or spectra so this may skew results.

Originally Posted by Breaking Waves

My lazy half is telling me that our focus on strength is misguided - these are already strong and going up in size will make then strong as anyone wants - so strength might be a diminishing returns focus and ease of construction and use might be more important.

I do think this a worthwhile exercise if the strength does prove to be around double for the soft shackle version compared to the loop. This significantly reduces the cost of making these strops strength for strength. It is also very useful being able to make them very short, something not possible with loop strops if they have a reasonable length of bury.

SWL

[Breaking Waves]

Originally Posted by Seaworthy Lass

Samson’s comments must be based on something they found though, so I would not be quick to dismiss this.

I don't dismiss it at all. I am sure it is accurate in the context it was developed. But we really don't know the details of that context, and our context here is almost surely at least somewhat different. Samson's comments are pointed at rope to rope connections. They don't specify in which rope material. We are talking about a rope to metal connection - which does not have the same compression issue and has different frictional properties and there are probably other differences I am not aware of.

There is some small wisdom in knowing how little you know

study Thinwater presented a link to recently is anything to go by, results are likely to vary dramatically depending on line diameter being tested

I missed that - do you still have a link? I have always found that results scale quite well over the range of line I would practically consider for an application - say in yachting within 5mm-18mm range I would normally not expect large differences. And similarily within 1"-3" range results have been pretty consistent.


Real world conditions can be very different.

yes, certainly, shock loading particularly is a major factor, which is pretty hard to measure or predict.

I am using a much larger ring (25 hole diameter) than you used.

yea, that was a cost saving measure on my part - I just threw away 21 rings in that one test. If they had all been distorting or breaking at the ring it would have concerned me as artificial, but given that's not where they broke it is perhaps less of a concern.

The other big variable is what attachment point size to select for the trial.

This would be a major decision for a second test - would depend on exactly what we were trying to discover.
An obvious choice would be to use what was used in the prior test - so the results would be comparable. Another choice would be to use something quite 'thin' (like 1:1 - but I guess the lab might not want to do that in metal because of safety/breakage concerns and in textile I would be worried we were not actually testing what we thought, see the Samson comment above) as a worst case to highlight any small D/d differences. And a third choice would be to use something 'typically used' - I do guess that the range of attachments is quite broad. Obviously, it would be nice to do testing across a whole range but that would, unfortunately, be abusing my test privileges.

Also, what was the spread of results in this last trial? Were 3 samples enough to provide statistically significant results?

yes, because I have quite a past data set of tests in this material I apply a Bayesian approach to these small samples. The variation between all common samples was quite small 3%ish, which based on my test history, indicates the 95% confidence is less than 10% (could even be as tight as 5% but I err on assuming less significance).

I do think this a worthwhile exercise if the strength does prove to be around double for the soft shackle version compared to the loop.

Yes. Just for discussion - my speculation is that if we crossed the buried tails in a loop, so that you had doubled/buried strands all the way around (which is not that hard to do), your strength difference would go away. Then you would just be left with the question of the cow hitch (on metal) strength vs the diamond strength, which I speculate the cow hitch would win, but interestingly in all the soft shackle testing, I don't remember seeing that comparison done.

breaking waves

[Breaking Waves]

Regarding the rings - I see I have a bunch of Tylaska FR10's leftover from a prior project. They are a bit bigger.

Regarding options for the strop pin end - it seems like we have 3 main options for strengthening - cross the bury's, multiple loops of smaller line, and the soft shackle. They all (essentially) carry double strands right around the loop. One or more of these might be the 'stronger solutions' - equivalent of the 'stronger/buried tail soft shackles'

Regarding the ring end - we have three main options, the tapered whipping, the bullseye and the double loops. My speculation is if we got them to break at the LFR end, that would be the order - don't know if it is worth testing or just using one to focus next test on the other end of strop.

I don't have a good thought yet on what bend radius to use at the pin end. My intuition is to use the same as the prior test for comparability, but that may not be best - not sure.

I also have some interest in the Brummel solution which dockhead mentioned. It will certainly be weaker than the above solutions. But I am guessing could be made equally strong to the best of the prior batch. Not sure if it is worth pursuing or not - probably not I guess.

It would be interesting to do a very direct test of doubled-strand cow hitches vs the diamond, and also a series just of cow hitches (regular one strand loops) at different D/d and materials. But that would be a different focus. (oh, and yes, for the pedantic, I suspect I really mean girth hitches, but someone more knowledgable about the nomenclature can correct me - I mean with a loop with both strands loaded).

[Seaworthy Lass]

Originally Posted by Breaking Waves

I missed that - do you still have a link? I have always found that results scale quite well over the range of line I would practically consider for an application - say in yachting within 5mm-18mm range I would normally not expect large differences. And similarily within 1"-3" range results have been pretty consistent.

I will hunt it up shortly. Results were staggering for me. I knew very thin line behaves quite differently, but this was testing diameters that we are using yachting.

Edited to add: note: webbing was used

[Seaworthy Lass]

Originally Posted by Breaking Waves

yea, that was a cost saving measure on my part - I just threw away 21 rings in that one test. If they had all been distorting or breaking at the ring it would have concerned me as artificial, but given that's not where they broke it is perhaps less of a concern.

One ring per strop certainly becomes a costly exercise.

If a Bullseye strop vs loop is used in this comparison and a LF ring size was chosen that was larger (as some cruisers, including me, use) and had no chance of distorting, then only one ring is needed for the entire trial. Despite the ring being retained snuggly, it can be removed from the Bullseye weave if the weave is spread apart a certain way. By the way, I have found this extremely useful.

If the pattern of the weave in the samples is secured with some tape it would take only seconds for the lab to swap rings.

SWL

[Seaworthy Lass]

Originally Posted by Breaking Waves

Regarding options for the strop pin end - it seems like we have 3 main options for strengthening - cross the bury's, multiple loops of smaller line, and the soft shackle. They all (essentially) carry double strands right around the loop. One or more of these might be the 'stronger solutions' - equivalent of the 'stronger/buried tail soft shackles'

A few comments just based on personal experience:
- I have tried crossing the buries and my strength lets me down.
I haven’t done this in a while, but the less bulky soft fid option may now make it more viable for me. It found that the only way I could achieve it was to poke though both fids before trying to pull one tapered tail through at a time. It was hard work though and I have been scarred by the process. I would not want to repeat it in a hurry.
Any tips on how to do this easily?

- It is hard to get good load distribution with multiple loops and it looks so very clunky. I am not fond of that option either, but it seems to be reasonably commonly used where short strops are needed.

- Clearly a soft shackle fan here .

Originally Posted by Breaking Waves

Regarding the ring end - we have three main options, the tapered whipping, the bullseye and the double loops. My speculation is if we got them to break at the LFR end, that would be the order - don't know if it is worth testing or just using one to focus next test on the other end of strop.

The latter sounds like the best idea to me, as the LF end has been explored and found to not fail at 160-180% of line strength. The attachment point is the problem.
Picking one of the three retaining options and reproducing that in loop and soft shackle form and comparing the two would be my vote. See which one performs better at the weak end .

Originally Posted by Breaking Waves

I don't have a good thought yet on what bend radius to use at the pin end. My intuition is to use the same as the prior test for comparability, but that may not be best - not sure.

I also have some interest in the Brummel solution which dockhead mentioned. It will certainly be weaker than the above solutions. But I am guessing could be made equally strong to the best of the prior batch. Not sure if it is worth pursuing or not - probably not I guess.

It would be interesting to do a very direct test of doubled-strand cow hitches vs the diamond, and also a series just of cow hitches (regular one strand loops) at different D/d and materials. But that would be a different focus. (oh, and yes, for the pedantic, I suspect I really mean girth hitches, but someone more knowledgable about the nomenclature can correct me - I mean with a loop with both strands loaded).

Testing combinations of the variables would be a daunting task (to say the least), but results would be fascinating.

Regarding nomenclature, I struggle to even get “rope” vs “line” consistently correct. It makes it hard as the terms “line diameter” and “percentage of line strength” are used by manufacturers when referring to what is available for sale, so calling it rope instead in this application just sounds odd to me despite being correct.
I bet anyone pedantic about terminology just cringes with each incorrect usage.

SWL

[Seaworthy Lass]

Originally Posted by Breaking Waves

I missed that - do you still have a link? I have always found that results scale quite well over the range of line I would practically consider for an application - say in yachting within 5mm-18mm range I would normally not expect large differences. And similarily within 1"-3" range results have been pretty consistent.

I have found Thinwater’s link:

https://eu.blackdiamondequipment.com...-together.html

These are the tensile strengths of the slings connected with strop bends in three diameters of Dynex. They vaguely note: “For our purposes, Dynex, Spectra, & Dyneema can be considered the same material”.

12 mm slings connected with a strop bend: 85% sling strength
10 mm slings connected with a strop bend: 58% sling strength
8 mm slings connected with a strop bend: 53% sling strength

Results are so markedly different that given your comment that large difference are not expected I wonder if I am misinterpreting something? Or does UHMWPE webbing behave completely differently with changes in diameter compared to rope?

SWL

[Breaking Waves]

Originally Posted by Seaworthy Lass

? Or does UHMWPE webbing behave completely differently with changes in diameter note: width compared to rope?

yes, this. webbing results (typically) do NOT simply scale with width. The geometry changes as they get wider - Something about edge to middle ratio I think (higher on narrow, smaller on wider) - thinwater could probably explain the physics better. The geometry of round rope does not change (as much).