Comparing techniques used for eye splicing double braid polyester (=Class 1)

[s/v Jedi]

Pages 5, 6 and 11 of this document need more attention.

http://www.paci.com.au/downloads_pub...tions_2006.pdf

[Seaworthy Lass]

Jedi, thanks for all the links. It is very appreciated.
The last one was for Milne and McLaren's paper that Alan was discussing earlier.
I still have to read that well. Lots to catch up on .

Originally Posted by s/v Jedi

And here is another good test video that shows the break occurs in the typical spot just in front of the splice, which is considered the weakest spot of the line:

Several tests would give more accurate data, but this is a very interesting link.

I wonder what initiated the break for the sliced rope - the core or the cover? The mode of failure would tell us lots. I suspect it was the core due to the issue of bunching of the cover there. The alternative of cover breaking first would be due to poor taper of the cover tail. This is less likely to me. There is no sharp junction at the end - they have tapered the very end of the cover tail. Also, in the splicing procedure there is no risk of inadvertent damage to the cover there - it is not spiked below the point the core tail exits, which is close to the base of the loop.

Their splice broke at 82% of line strength. Lots of room for improvement there. No reason why close to 100% can't be achieved.

In their splicing video, English Braids follow the "Selma type method", as Premium do (these are the only two rope companies I have found that do this). The amount of "shrinkage of cover" English Braids allow for with their dimensions chosen is about 11 rope diameters by my estimates, one of the very highest. This results in lots of core being cut off unnecessarily at the end, creating a high imbalance in core:cover length past the splice. The fact that their splice broke at 82% is very informative. We don't know if they spliced here as they teach in their video, but if they did it confirms it is not one of the best techniques.

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Regarding the bowline breaking (did it break or slip, they did not actually show), it did so at 51% of rope breaking strain. Again just one measurement, but very low.

In his load tests, Evans Starzinger found bowlines in New England Ropes dacron double braid broke at about 67% of line strength for an assortment of diameters. Bowlines in Samson dacron double braid broke at about 74% for an assortment of diameters. New England put a higher breaking strain on on their line, which evened out some of the discrepancy.

So English Braid at 51% was low. Maybe it was due to poor dressing (the knot may not have been well snugged up before any load was applied) or maybe high load was applied too soon that gave high slippage, which in turn generated more friction and heat and caused early failure.

Thanks again for that video link, it adds to our knowledge base.

SWL

[s/v Jedi]

Here's another interesting thread:

Rope/knot/splice load testing - Gear Anarchy - Sailing Anarchy Forums

[Juho]

Originally Posted by s/v Jedi

Well, for a somewhat different angle we could consider this German splice from Gleistein Ropes

- This splice is interesting since it is architecturally different from all the other discussed splices.
- This technique may give a smooth structure to the body of the splice since it is very much based on having one component within another, not on having them parallel inside the outmost cover.
- Long and smooth tapering too.
- The main load of both cover and core come directly to the loop, not via a crossover. That could give it some strength. But on the other hand both the incoming cover and core go round the loop in the same direction, which might make the stress in the loop one-sided. The strength of that part may however be >100% in all splices, so this point may not be very important.
- This technique could be good for ropes whose cover is weaker than the core since the buried segments are mostly core.

Good addition to the list of splicing techniques.

Juho

[s/v Jedi]

Originally Posted by Seaworthy Lass

Jedi, thanks for all the links. It is very appreciated.
The last one was for Milne and McLaren's paper that Alan was discussing earlier.
I still have to read that well. Lots to catch up on .

They tested splices with the core only partly into the eye etc. Exactly info you need now

[Juho]

Originally Posted by s/v Jedi

And here is another good test video that shows the break occurs in the typical spot just in front of the splice, which is considered the weakest spot of the line:

The free segment of the rope was so short that it is not easy to say if the rope broke just in front of the splice or just at some point along the rope.

If the rope broke next to the splice (more than 10mm away) and not within the splice, then the most natural explanation is maybe misbalanced cover and core. It is possible that the long end of the rope is balanced, and the misbalance (too much cover of too much core) is right next to the splice after splicing. When tension grows, also friction grows, and the misbalanced section might stay misbalanced (not sharing the misbalance efficiently with the rest of the rope), and therefore the rope would with 100% certainty break around that area. There was not enough evidence to conclude this, but if the rope systematically breaks near the splice but not right next to the bulky part, this story could be true.

[Seaworthy Lass]

Originally Posted by s/v Jedi

Here's another interesting thread:

Rope/knot/splice load testing - Gear Anarchy - Sailing Anarchy Forums

Good find! Thanks.
I have not seen this thread.

Estar is Evans Starzinger. The user "Allen" participating in the thread is Allen Edwards. He has the LC-36 website with very useful information about working with dyneema: L-36.com. He and Evans worked with Brion Toss to create the High Strength soft shackle using Brion's ingenious Button knot.

The SA thread you found looks like the start of Evans's load testing. He must have continued on to do the full series of tests on bowlines using various diameters of dacron double braid.

I will add it to the reading list. There will be all sorts of useful bits of information there I think.

There was a long thread here on CF a few years ago too when Evans was doing his load tests. I will look that up as well.

SWL

[Seaworthy Lass]

I found Evans's thread here on CF when he started load testing:

http://www.cruisersforum.com/forums/...ts-118009.html

There may be info there about eye splices in double braid. It has been a while since I looked at it and I can't remember now.

SWL

[s/v Jedi]

And this page needs to be bookmarked as well. I finally found test results for the "big overhand knot" soft shackle.

A comparison of Soft Shackle methods | Slack Science

[Seaworthy Lass]

Originally Posted by s/v Jedi

And this page needs to be bookmarked as well. I finally found test results for the "big overhand knot" soft shackle.

A comparison of Soft Shackle methods | Slack Science

The results for the Big Overhand Knot (224% of line strength) agree roughly with what Evans found. It is not clear how many samples Evans tried using the Big Overhand Knot, but he said strength was 230% of line strength, with failure occuring at the noose end (indicating limitation was not the stopper). The Balance Community study found a similar failure mode. They attach photos of where the soft shackles broke, which is very informative.

The same strength of around 230% applies for soft shackles using Brion's beautiful Button stopper.

The same applies if a toggle is used.

All these methods double the thickness at the base of the stopper compared to soft shackles using the Diamond stopper (the ends are buried back into the legs), so failure then occurs due to the limitation in strength at the noose end.

In soft shackles using the Diamond stopper, the base of the Diamond is the limitation instead.
Evans found the strength of these was 170% for the original design.
The Balance Community study found 140% for the original design and 148% for the Better design. They do not indicate if this difference is statistically significant.
I think the difference in strength found here is due to the care taken with construction. Loading must be equal on the two legs to maximise strength. How the central bury is milked will affect this a lot. That is one advantage of the Kohlhoff style soft shackles with no central bury. The only way you can stuff up load distribution is by making the noose too small.


Rope manufacturers are slow as molasses to update their websites with best techniques. All I have found still give instructions only for soft shackles using the Diamond stopper and generally not even for Allen Edwards' Better design with the improved method of opening the noose. It will be interesting to see how long the lag is .

Jedi, the soft shackles you made and posted images of here on CF were the first I had seen. My interest grew in leaps and bounds from there . What style of construction are you using now?

SWL

[Seaworthy Lass]

This comment was made in response to Juho's consideration of what an extreme splice would be like (a super thin one with no core in the loop and both core and cover tails well tapered):

Originally Posted by Seaworthy Lass

If the core is somehow gripped, as far as I understand, the proposal is based on the assumption that the cover is responsible for 50% of the strength of the rope. I am not sure that is correct .........

I am rewatching the videos to check the data we are collecting and I came across this interesting snippet from Premium Ropes when the little arrow is clicked at the bottom of their June 2016 video (May 2016 in Dutch). I hadn't picked it up before, as I was looking at the Dutch version:

"A core-dependent rope (polyester or nylon core) takes approximately 30% of its breaking strength out of its cover".

Therefore 70% is from its core.

If this is correct, then it is critical that core is well secured in the loop of the splice. A loop of cover alone will not provide line strength, even when new.

[Juho]

Originally Posted by Seaworthy Lass

This comment was made in response to Juho's consideration of what an extreme splice would be like (a super thin one with no core in the loop and both core and cover tails well tapered):



I am rewatching the videos to check the data we are collecting and I came across this interesting snippet from Premium Ropes when the little arrow is clicked at the bottom of their June 2016 video (May 2016 in Dutch). I hadn't picked it up before, as I was looking at the Dutch version:

"A core-dependent rope (polyester or nylon core) takes approximately 30% of its breaking strength out of its cover".

Therefore 70% is from its core.

If this is correct, then it is critical that core is well secured in the loop of the splice. A loop of cover alone will not provide line strength, even when new.

For ropes with strong core the Gleistein method (see s/v Jedi's mail #149) would be a good choice since it relies heavily on the strength of the core, and cuts the cover tail short (instead of the core).

Also the Samson, Selma etc. splicing methods may work well since 30% strength may well be enough to construct a splice that is stronger than the rope.

I attach a similar figure of the Gleistein splice that was used for the other splices, to show how it differs from the other methods, and how core centric it is.

[Seaworthy Lass]

Originally Posted by Juho

For ropes with strong core the Gleistein method (see s/v Jedi's mail #149) would be a good choice since it relies heavily on the strength of the core, and cuts the cover tail short (instead of the core).

Also the Samson, Selma etc. splicing methods may work well since 30% strength may well be enough to construct a splice that is stronger than the rope.

I attach a similar figure of the Gleistein splice that was used for the other splices, to show how it differs from the other methods, and how core centric it is.

That is an excellent diagram Juho!
It lets us easily picture what is happening .

It is a very elegant design and I think this method would provide greater grip, as the core tail is buried in something else other than just the cover.

This design is I think not made for Class 1 rope, but more more slippery stuff that needs that greater grip. It is a more complicated technique, so given slippage of the core tail is not a common problem for Class 1 splices I think there is no need to go to this extreme for polyester. Just my view .

SWL

[Juho]

Originally Posted by Seaworthy Lass

That is an excellent diagram Juho!
It lets us easily picture what is happening .

It is a very elegant design and I think this method would provide greater grip, as the core tail is buried in something else other than just the cover.

This design is I think not made for Class 1 rope, but more more slippery stuff that needs that greater grip. It is a more complicated technique, so given slippage of the core tail is not a common problem for Class 1 splices I think there is no need to go to this extreme for polyester. Just my view .

SWL

The Gleistein method is complex since it extracts core twice. But on the other hand the measurements are quite easy. Many were just approximate, but the splice is still accurately measured.

The shrinking of the rope does not influence the measurements much. The buried segment is buried inside both core and cover, which means that cover and core are expected to shrink about as much, and therefore P' will stay in the finished splice pretty much where it was marked. From this point of view the structure and measurements are simple.

One more benefit might be that the size and type of the rope doesn't influence the measurements much.

He used hydraulics for final milking. I hope it is doable also by hands.

Edit: I think the end of the core needs to be placed quite accurately to get the correct loop size (without any cover / core misbalance).

[s/v Jedi]

Originally Posted by Seaworthy Lass

Jedi, the soft shackles you made and posted images of here on CF were the first I had seen. My interest grew in leaps and bounds from there . What style of construction are you using now?

SWL

The last ones I made were still with the diamond knot. I now have 650' (!) of Amsteel Blue coming, bags full of low friction rings, Antal clutches etc. so will be doing a lot of rope work in the months ahead. I think I will try the big overhand shackle this time for two reasons: I can do the eye splices very quick and I now have one of those miracle Dyneema scissors coming so expect to do them even quicker. Second reason is that I really like how the buried tails of the two eye splices goes all the way through the stopper knot, into the legs of the shackle without interruption. The button-knot method starts the bury right under the knot so that it a weak point, right where the noose goes around to load it up and possibly crush fibers on the ridge where the tails start the bury.

I'm still thinking about toggles, how to keep low friction rings up from deck etc. I'll be making boom vangs with those