Low Friction Ring strop methods survey

[Dockhead]

Originally Posted by 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.

Hmm, so I wonder whether then I need to redo the splices in my drogue after all. I was in the Arctic without Internet and was using my Father's old dog-eared first edition of the Brian Toss book. I can't remember the bury length, but it was less than 72x, and when I got back to civilization and found out that 72x is the present standard, I decided I needed to redo them. Most of the cordage is 14mm, so those would be some long buries (more than a meter).

[Breaking Waves]

Originally Posted by Dockhead

Hmm, so I wonder whether then I need to redo the splices in my drogue after all. .. first edition of the Brian Toss book.

can't be sure without knowing it is 45x or more, but if it is, with some cleanly done lock stitching it 'should be good mate' as the Aussies say. Lock stitching can be screwed up - too tight, distort weave, etc so study up and take your time.

Brian does not always get it right but is usually reliable.

Edit: just looking at an old copy - it looks like Brian was recommending 24x bury except for the brummel where he says 48x, 24 is not enough, 48 is. But not sure if that's the copy you were reading and what you did or not.

[Dockhead]

Originally Posted by Breaking Waves

can't be sure without knowing it is 45x or more, but if it is, with some cleanly done lock stitching it 'should be good mate' as the Aussies say. Lock stitching can be screwed up - too tight, distort weave, etc so study up and take your time.

Brian does not always get it right but is usually reliable.

Checking back - it was 48x, with brummels per Brian's instructions, with careful tapers, and proof tested on a big electric sheet winch like all of my splices.

[Breaking Waves]

The Antal bury is 29 or 30x. That is tested around about's (27x is sometimes quoted) as the absolute minimum which will hold high load under perfect load conditions (slow and steady loading). But it should have lock stitching. And the load is never perfect, so more is needed in the real world.

In terms of absolute maximum strength, about a 30x taper is often quoted (with 16x often used being quite close 95% of maximum), which is just usable with the 45x bury.

[fxykty]

Originally Posted by Breaking Waves

The Antal bury is 29 or 30x. That is tested around about's (27x is sometimes quoted) as the absolute minimum which will hold high load under perfect load conditions (slow and steady loading). But it should have lock stitching. And the load is never perfect, so more is needed in the real world.

In terms of absolute maximum strength, about a 30x taper is often quoted (with 16x often used being quite close 95% of maximum), which is just usable with the 45x bury.

Please explain the length of bury untapered and the length that is tapered. In the above, do you mean ‘a 30% taper is often quoted’? So if my bury is 45x, 16x of that (just over a third) is the taper? 29x are all strands, then the remaining 16x is tapered? Or is it 45x all strands and an additional 16x tapered?

For lock stitching, I’ve read that one should use thread that is the same diameter as for one strand of the 12 strand that is being spliced. Does it need to be the same material, or can one use polyester thread or line? When stitching through the bury, is it important to not split strands on the inner rope just the same as not splitting strands of the outer rope?

[Benz]

Originally Posted by Dockhead

Hmm, so I wonder whether then I need to redo the splices in my drogue after all. I was in the Arctic without Internet and was using my Father's old dog-eared first edition of the Brian Toss book. I can't remember the bury length, but it was less than 72x, and when I got back to civilization and found out that 72x is the present standard, I decided I needed to redo them. Most of the cordage is 14mm, so those would be some long buries (more than a meter).

If you have brummels, 45x bury is more than enough. At the shop we only do the full 52-ish diameters (we count it in 'fids'; a three-fid bury is our standard) if it's a straight bury. Often we do 14mm with a brummel and a 14" bury. Seems short, but we put 20% of BL on them with the hydraulic puller to set the splices, and they never budge.
You have to consider that a fatter line will have more surface area of constriction in a shorter distance, so your lines can safely have a lesser percentage of bury as they get fatter. I do my longest buries (percentage-wise) on the thinnest line.

[Breaking Waves]

Originally Posted by fxykty

Please explain the length of bury untapered and the length that is tapered. In the above, do you mean ‘a 30% taper is often quoted’? So if my bury is 45x, 16x of that (just over a third) is the taper? 29x are all strands, then the remaining 16x is tapered? Or is it 45x all strands and an additional 16x tapered?

If I used the "%" sign anywhere, that was a typo and sorry. It should all have referred to "x" diameters.

So, my recommendation for you would to do a 60 diameter bury, with 30 diameters of that (eg half) tapered. There are lots of other measurements that would work fine, but we all would have absolute confidence in that recommendation (assuming you do a good job).

There is some good testing that has been done on bury lengths and tapers, and there are some subtle points, but it boils down to a 'long enough' bury and a taper with as fine a point on it as you can make.



For lock stitching, I’ve read that one should use thread that is the same diameter as for one strand of the 12 strand that is being spliced. Does it need to be the same material, or can one use polyester thread or line? When stitching through the bury, is it important to not split strands on the inner rope just the same as not splitting strands of the outer rope?

I am aware of less good testing on lock stitching techniques. The various suggestions you are referencing here are suggested on the samson website. They have some viedos and instructions for lock stitching which is worthwhile reading. You can not go wrong following them.

However, I will note that I personally do not do it that way. I have no test data to suggest that my way is better, it probably is not, but it is a bit easier and test data suggests it is not noticeably worse (eg I get good test results using it). I use smaller diameter thread than they suggest. For small line and loads (like this strop test and almost all yachting applications) I just heavy polyester carpet thread (V138 size), for bigger loads I move to small Dyneema kite line. It is good not to split strands, and I try not to, but this is easier in a really big line than small yachting line and I don't fuss over it in a small line.

Your mission is to not distort the lay of the line - stitches snug but not tight, straight thru, not at odd different angles, as cleanly thu as you are able.

hope that all makes sense. again, look up the samson instructions, and Yale also used to have some good stitching stuff online not sure if they still do.

[Breaking Waves]

Just thinking of improvement direction.

I think we would be justified just saying those are very good and strong designs, way good enough for our applications, and if you need more strength go up one size in the line.

but I do have a couple of quick thoughts

1. crossing the bury's so that there is no unburied section in the line would target the main weak spot. I am usually against throwing extra line length at a weakness, but in this case we usually only have a really short section without bury, we usually are having to make the strop longer than we prefer to get the minimum bury in, so this would not be much extra line and would allow us to go just a little shorter strops. The downside is that while pulling the bury's across each other is not rocket science, it is a bit more complicated and does occasionally take a little muscle. I typically have to use a puller sleeve to get it done cleanly.

2. using smaller diameter strop line in multiple loops would greatly reduce the importance of the unburied section and make the strength much more even all around the strop. You could pick the diameter so you did not end up using more weight of Dyneema. The drawback is you would have a multi-part strop, which would just be a bit less elegant when moving around. You could put the strop inside a chafe cover so it was 'one piece' and the chafe/UV protection would not be for naught. (see like the loups construction). I think you would have to use a tapered whipping design for this approach.

3. Whippings - the flat whipping (like antals) can be done but it gets progressively harder the bigger the ring, so for DIY, I would remove it from the very top tier solutions (leaving the tapered whipping, the double eyes and the bullseye in the top tier). The 'trick' to the tapered whipping is to pull the strop really really hard and then make the whipping on it when it is set up bar tight. This ensures the whipping is the right taper and that it does not get slide down when the strop comes under load. I think it would help to put a tight flat strong whipping in the middle of the strop. This would protect the tapered one from different pin sizes at the attachment end and reduce any sliding pressure.

I need to contact samson and see if they will give me instructions on how they make this one - I am sure it is well tested to enormous load, and it looks pretty clean.



we are fishing for a max possible gain of 20%, so perhaps none of this extra complexity is worthwhile given how strong they are.

[jharding]

thanks for all the work and great reporting, I feel more confident in the ones I have made up.

[Juho]

Thanks for the information. Real world tests give us a solid base for our theoretical discussions.

[Seaworthy Lass]

Hi Breaking Waves
Many thanks for all the time and trouble taken with this.

The shackle pin size : line diameter in the load test was only 3.6 : 1 so results are actually better than expected regarding the break strength compared to the graph presented below.

That predicted the loop would break there at around 148% line strength and suggested 180% could never be achieved.
I suspect the discrepancy is simply because a different diameter rope was used for the data presented in the graph (or that line strength was actually greater than specified in this latest trial).

In practice, 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. This will instantly bring system strength down to roughly 80% of line strength.

Even if the bail diameter is increased, I think the cow hitch will not allow the expected increase in strength to occur. I have not seen results reported, but given the line needs to pass around two legs, I doubt much more than 120% of line strength would ever be seen with a cow hitched loop (and likely to be less than 100%), regardless of how huge the bail diameter is made.

If you haven’t already guessed, cow hitched loops are not my favourite .

Using a soft shackle strop instead of a loop avoids the cow hitch limitation. Even incorporating a diamond stopper knot, using the same diameter rope the strength will be more than double the strength of loop strop that is cow hitched on if the bail : line diameter is 1:1.
This is because potential system strength is doubled for a soft shackle with 4 “legs” compared to a loop with 2 “legs”.

I use the soft shackle form of the Bullseye rather than the loop almost exclusively not just because I am able to select a thinner rope for the same strength (and because it needs less rope to make), but also because I can make it short and it is removable while the line is passing through the ring.

For anyone who has not seen the bending loss graph previously, given the loop strop broke at the “attachment” end for all the samples except the Antal strop, I think one big take home message from this trial is make your strops for LF rings soft shackles rather than loops.

SWL

This graph came from here:
Static Bending Loss in Dyneema

[Seaworthy Lass]

This is how the Bullesye weave looks in soft shackle form.
The length can be made quite a bit shorter than I have opted for below:

[Breaking Waves]

^^ the Hampidjan graph is specifically for dux, a heat set product, which amsteel is not. The specific curve/numbers change a little but the general characteristics of the curve are common across high modulus fibers (and wire).

I can’t comment on the soft shackle vs cow hitched strength argument. Would need to see test data. As we have seen here, actual testing can reveal things, different that we (or at least I) expected.

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.

I do agree the soft shackle is a more versatile attachment than the fixed loop. On the flip side I worry that it adds a level of complexity, on top of the ring connection construction, which is daunting for DIYers and could introduce construction defects which weaken the end solution.

The lab did offer to do another round of testing if we had “ improved solutions”.

[Seaworthy Lass]

Originally Posted by Breaking Waves

^^ the Hampidjan is specifically for dux, a heat set product. The specific curve/numbers change a little but the general characteristic of the curve are common across high modulus fibers (and wire).

I can’t comment on the soft shackle vs cow hitched strength argument. Would need to see test data. As we have seen here, actual testing can reveal things, different that we (or at least I) expected.

I do agree the soft shackle is a more versatile attachment than the fixed loop. On the flip side I worry that it adds a level of complexity, on top of the ring connection construction, which is daunting for DIYers and could introduce construction defects which weaken the end solution.

The lab did offer to do another round of testing if we had “ improved solutions”.

Given nothing failed at the LF ring end for all five samples you constructed, I can’t imagine loops could be improved over and above this, as the weak point is at the attachment end.

In practice, loop strops will be far less strong than tested (possibly less than half the strength tested) if cow hitched onto attachment points around the same diameter or even slightly higher. Load testing results on cow hitched loops have already shown this.

If we are trying to maximise the strength of strops used for LF rings, I do think soft shackle versions are the way to go. I agree though that they are harder to make if someone is not experienced with soft shackle construction, and also there is room for more error if some basic care is not taken. Even manufacturers get this wrong - eg I have seen Kohlhoff style soft shackles with diamond stoppers for sale with eyes that are barely one rope diameter in size .

SWL

[Breaking Waves]

just looking at cad drawings of harken padeyes
there smallest one 57mm base, has a bail of 8mm (1.5x 5mm) and the 95mm base has a 14mm bail (2.8x 5mm)