Low Friction Ring strop methods survey

[Breaking Waves]

Survey of low friction ring strop options

Test materials:
Tested using Antal 14 x 10 ring rated SWL 3520lbs
5mm amsteel avg break strength 5400lbs, Except series A0 used 6mm amsteel avg break strength 8600 lbs
¾” (19mm) shackle on strop, which would be 3.8:1 bend radius
½” shackle thru ring, designed to minimize ring deformation

Sample A0 – commercial benchmark sample - Antal manufacturer flat whipped, ¼”
Test Load 8836 LBS, 103% line strength
This sample did not break. At the max load the splice buries slipped out. Also, the whipping slipped down the strop.

These three statistically the same:

Sample A1 – DIY flat whipped 3/16”
Test Load 9543 LBS, 177% Line strength
All 12 strands broke on the 3/4" pin.

Sample B - B = tapered whipped 3/16”
Test Load 9668 LBS, 180% Line strength
All 12 strands broke on the 3/4" pin.

Sample C - C = two spliced loops 3/16”
Max Load 9754 LBS, 180% Line Strength
11 strands broke on the 3/4" pin.

Just barely Statistically lower
Sample D - D = woven gasket (eg bullseye) 3/16”
Max Load 8713 LBS, 161% Line Strength
11 strands broke on the 3/4" pin side. It broke about 1" from the 3/4" pin, but not at the bury taper

Substantially lower
Sample E - E = cow hitch gasket 3/16 “
Max Load 6666 LBS, 123% line strength
It broke on the ring at the chock point. These was some ring deformation - only sample with ring deformation.


Summary thoughts
1. The weak point in the main contenders was NOT at the low friction ring end. We have probably been overthinking and the various throat issues. This included the very tight, high angle splices to the ring – they did not break or tear at the throats.
2. The weak point in the main contenders was at the 3.8:1 bend radius on the strop attachment/deck attachment end. So, in terms of maximizing strength we have been under emphasizing this area. The main contenders all have 4 strands around the strop and only 2 at the attachment end.
3. Based on the Sample E ‘cow hitched to ring solution’ - Clearly you don’t want to use a solution which squeezes the rings as that can cause ring deformation, which then can cause a point load breaking point on the ring. You also probably need to be careful using a small highly loaded line in a big ring because it would be more prone to ring deformation.
4. The BullsEyes tested just barely statistically lower than the three equally strongest samples. I’m am guessing this is because I may have put more twists in these strops than in the simpler constructions. I expect perfectly made this is as strong as the others, but needs some care not to add twists while you are doing the weaving.
5. The general results suggest DIY the samples were decently well made. They did not break at the taper ends, suggesting the tapers were fine enough. And the variation is reasonably low. The Antal constructed sample seems like a simple failure of splice construction. Not long enough bury, and whipping not constructed to stay in place. It was the only sample where the bury was not lock stitched - all the others I made with lock stitch - in theory that should not matter because this bury pulled out at high load rather than low load.

[Breaking Waves]

An Antal sample with bury pulled out and splice slipped.

[Breaking Waves]

Sample E - cow hitch, with ring deformation and break on top of ring

[Breaking Waves]

Bullseye break - not at the pin and not at the bury taper, which leads to thought about twist being added in construction

[Breaking Waves]

The other breaks are not very interesting, just clean 12 breaks at the pin. I will say this surprised me with the 3.8:1 bend ratio.

[Breaking Waves]

Final thought - the three main contenders were all damn strong. 9500lbs using 3/16" line is going to be good for almost any typical yachting applications, and you could go up a size or two in line and get something really super super strong.

[Steve_C]

Thanks for sharing, this is really interesting and also really comforting to know. Nothing like real world testing!

[Breaking Waves]

This might help people quickly see which sample is which method:

[Steve_C]

Its hard to find a case against "Sample C". Simpler and works as well or better than any.

The results also may suggest that the lock stitching plays a role under load. That would be fairly easy to test and would be very interesting.

Thanks again for this!

[dreffo]

Really interesting, thanks for sharing!

[Breaking Waves]

just for reference - some close-ups of the puller shackle bend area where the strongest options were breaking.





note1: this is with the sample A0 6mm line, the other samples were 5mm line so a slightly bigger bend radius

Note2: I am sure someone with eagle eyes will spot that the shackle body has 5/8 stamped on it - The 5/8” is referring to the dia of the bow, and a 5/8” Bow shackle has a pin dia of 3/4”.

[Breaking Waves]

and this is a picture of a spare bullseye I made (looser version). I was just checking for any obvious twisting in the construction, and I don't really see any. I also talked to the guy who actually did the pull breaks and he said checking for twists was part of his normal setup checklist and that he did not notice anything unusual.

It is possible that the twists are hidden in the bury's.

The only other thing in the area where they broke is the exit point for the bury's - where they come out before being tapered and milked back in. The fibers there are not normally disturbed enough to cause it to be the breaking point.

Given it is right on the edge of statistical significance - It's also possible that this is 'just statistics' and these are really as strong as the others just with unlucky variation. However, we did break 6 of these (3 tighter and 3 looser) so the confidence band is tightest for this solution.



I'm still puzzling this one thru.

note1: the tighter and looser tested the same.

[Dockhead]

Outstanding contribution -- thanks for this!!


I'm surprised that these things were breaking at the loop end. Really interesting. We may be underestimating the bend radius factor. So I guess at 1:1 (more typical of our real cases), then the strength of all of these will be reduced to something like 100% of line strength, right? At that point of course the rest of the construction is meaningless -- not the weak link at all.



But I think the other takeaway is that our collective marlinspike seamanship is up to snuff!! And far better than what Antal sells for money. I'm really pleased with that.



The differences between all the normal homemade ones (excluding the cow-hitched one) are meaningless. They are absolutely fit for purpose, strong as hell, just watch the bend radius! I guess the 1:1 we often use on the loop end is really going to be the limiting factor.




And the Antal thing is crap, on two different fronts. Disappointing.

[Breaking Waves]

^^ yup, good summery.

I’m still trying to understand the why’s of some of the details and the lab kindly offered to do some follow up pulls if I needed.

The lab’s comment when I asked them about the break at the bends was: The max strength possible (for these configurations) is 200% (they noted that we did not test the actual strength of this spool of line, as we usually will for commercial testing, and it could be 10% below average strength and still be within Samson specs). It has to break somewhere, and that (usually) is going to either be the bury end or the bend. The tapers were good so it was the bend. They considered we were ‘not far off max possible’.

It is a bit too bad that your Brummel approach did not come up until a bit late. It reverses the design, putting more strength at the bend and less at the ring. I think I know what would have happened, but would have been interesting to have confirmed it.

I am going to talk to Antal, as this could be easily made stronger at almost no extra costs. I had expected the whipping would slip or fail first, sort of as a fuse, because that then still leaves your load contained by the strop with time to do something about it. But the bury’s pulling out is unacceptable. That should not happen. That all said, it is acceptably stronger than their published SWLs, so if you just use it to their published specs you will be fine.

Edit - the rings themselves performed quite well. I had expected more deformation than we got.

[Breaking Waves]

BTW, regarding bury length - I was using 45x diameter. This is sort of a standard in the commercial world - minimize bury length and rope used while still long enough it will not pull out with some small lock stitching. There is no downside to the 60x and 72x standards and they may be marginally better in some edge cases, but they are really not necessary if the splice hygiene is good.