“Twisted” & “Reinforced Super Strength” Soft Shackles

[Breaking Waves]

Originally Posted by s/v Jedi

What size Dyneema did you use for shackle and for the insert? I often use 1/4” Amsteel Blue and am considering trying it with a 3/32” Dyneema insert...

This is part of my reluctance here - we tried a whole bunch of combinations. And my conclusion was that you could add an arbitrary amount of fiber (chasing the failure point in sequential designs) and get an arbitrary amount of extra strength. But it is arguable how much 'better' design that is or just using more fiber.

But to answer your question more helpfully . . . the sort of baseline design we had was 6mm plus 3mm insert. Which generally produced the sort of rough strength gain I mention above.

I only did one (large) batch (and a second run of a few smaller weaker ones) of these so we did not iterate on the design much. I don't know what the optimal efficient (strength for fiber weight) insert would be.

[Seaworthy Lass]

Originally Posted by Breaking Waves

.....But to answer your question more helpfully . . . the sort of baseline design we had was 6mm plus 3mm insert. Which generally produced the sort of rough strength gain I mention above.

Using a 3mm insert in 6 mm line (and was it 16x line diameter for the length ie 96mm, or shorter?) was the breaking point still the eye or did it shift to the base of the stopper?

It is helpful to know whether or not there would be any point strengthening the eye further. I used the same diameter of line as the rest for my insert and chose 40x line diameter for the length of the insert

[Seaworthy Lass]

Originally Posted by s/v Jedi

What size Dyneema did you use for shackle and for the insert? I often use 1/4” Amsteel Blue and am considering trying it with a 3/32” Dyneema insert...

I used 5mm line for both the shackle and insert.
The insert was 200mm long. 50mm at each end was tapered. I figured it generally needed an absolute minimum of 30 x line diameter for splices, a third of which is tapered, so I added another 50mm for the taper at the other end, bringing the total length to 40 x line diameter.

[Breaking Waves]

Originally Posted by Seaworthy Lass

Using a 3mm insert in 6 mm line (and was it 16x line diameter for the length ie 96mm, or shorter?)

Oh, we had a misunderstanding the 16x was for the tail bury (a whole different test sequence), not the insert - responding to some discussion above about whether the tails needed bury. I don't have good records on the insert lengths (because brion made most of them) - I just know there were 3 lengths, and they got stronger. The ones I made I made 'long', as in well past the eye on both sides (something like 75mm past the eye on both sides just looking/guessing at a photo I have), but I was trying to match brion's length rather than go for any particular x factor.


was the breaking point still the eye or did it shift to the base of the stopper?

We had some of the bigger diameter ones (I think they were 1:1 like yours) actually shift the break to the body of the shackle, but it was not completely consistent like it should be with high-quality consistent construction.

It is helpful to know whether or not there would be any point strengthening the eye further

The 2:1 ones (6mm/3mm) mostly still broke at eye. So yes, I think adding more fiber there up to 1:1 probably does add strength

Sorry, this was a decently long time ago now and I was mostly not the one making the samples and we did not explore it in depth. Really, please don't take this as any sort of specific guidance . . . all I would really want to say is that they were definitely stronger.

......

[Seaworthy Lass]

Originally Posted by Breaking Waves

Oh, we had a misunderstanding the 16x was for the tail bury (a whole different test sequence), not the insert - responding to some discussion above about whether the tails needed bury.

I have been making 30 x line diameter the length of the tail bury. I vaguely remember anything less than that gave less consistent results for load testing. If the shackle can be strengthened so it starts to break at the button, 50 x line diameter for tail bury (that seems to be the minimum recommended for other splices) may increase strength further.

Originally Posted by Breaking Waves

I don't have good records on the insert lengths (because brion made most of them) - I just know there were 3 lengths, and they got stronger. The ones I made I made 'long', as in well past the eye on both sides (something like 75mm past the eye on both sides just looking/guessing at a photo I have), but I was trying to match brion's length rather than go for any particular x factor.

We had some of the bigger diameter ones (I think they were 1:1 like yours) actually shift the break to the body of the shackle, but it was not completely consistent like it should be with high-quality consistent construction.

I took a guess that 1:1 would be needed to shift the break to the shackle base. Also the thinner the insert, the longer it would probably need to be, and I had absolutely no idea by how much, so I stuck with 1:1.
1:1 seemed to be constructed easily when I first tried it in the twisted version so I repeated that.

Originally Posted by Breaking Waves

The 2:1 ones (6mm/3mm) mostly still broke at eye. So yes, I think adding more fiber there up to 1:1 probably does add strength

Sorry, this was a decently long time ago now and I was mostly not the one making the samples and we did not explore it in depth. Really, please don't take this as any sort of specific guidance . . . all I would really want to say is that they were definitely stronger.

No apologies needed. Any scraps of info help to satisfy curiosity and are useful. I am quite taken with the reinforced version and had never seen it discussed so I previously assumed efforts constructing this failed.

[Breaking Waves]

Originally Posted by Seaworthy Lass

50 x line diameter for tail bury (that seems to be the minimum recommended for other splices) may increase strength further.

The long burys (60-70x) are mostly to prevent the possibility of low load slipping and 'more is better' type design. I have seen no indication (from anyone's tests) that they increase strength. The commercial guys I hang with (using expensive rope they don't want to use extra of) do 45x burys (lock stitched) on end loops and they are super conservative and careful and everything proof tested (and tuck splices if that length bury is too expensive in rope terms or length for the application).

I would have to go look but I seem to remember that my testing on end loops indicated that you could go down to like 28x without any loss in static strength so long as there was no slipping allowed. But that was exploring the edge minimal case. The commercial guys would never do that because the stitching could take up load in the low load slip situation and then distort the weave in a higher load situation later.

The button burry is a somewhat different geometry than an end loop (Im not sure, but it may act like the bury is essentially captured at one end), my testing there suggested you could go down further and not lose strength. That is pretty decent empirical data, which I don't have any good reason to question. However, what you are doing is certainly justified and conservative, and just fine if it works good for you.

........

[Seaworthy Lass]

Originally Posted by Breaking Waves

........ However, what you are doing is certainly justified and conservative, and just fine if it works good for you.

I assume a SWL of only 1/5 of estimated break load for my soft shackles and conservatively oversize anyway so have never had a soft shackle break in practice. I don’t need to be working on the edge, as race boats are. It was Ben Lexcen who said something like “If it doesn’t break it is too heavy”

For me it is satisfying constructing these as well as I possibly can, and I do take a great deal of care when making each one.

Improving design also just simply intrigues me.

[Breaking Waves]

Originally Posted by Seaworthy Lass

Improving design also just simply intrigues me.

yea, for us both.

Im just hanging with guys for whom 'improved design' is 'getting the job done with the least possible materials, labor and complication'. That pushes the conversation to a different corner than 'the best possible strength and attractiveness regardless'. Both are perfectly valid objectives.

I just like learning - so it is the 'surprises' that motivate me - like your twists being stable.

[Seaworthy Lass]

Originally Posted by Breaking Waves

yea, for us both.

Im just hanging with guys for whom 'improved design' is 'getting the job done with the least possible materials, labor and complication'. That pushes the conversation to a different corner than 'the best possible strength and attractiveness regardless'. Both are perfectly valid objectives.

I just like learning - so it is the 'surprises' that motivate me - like your twists being stable.

Add handling, reliability and cost/strength to my objectives too . I think all these also apply for most cruisers. Difficulty of construction and time taken are not a major concern for me, at least not initially, as I have found both speed and ease increase dramatically as skill level rises. Only needing to make dozens, not thousands of these alters criteria as well.

[s/v Jedi]

Thread drift: what are your ideas on the Antal dog bones?

[Breaking Waves]

Originally Posted by s/v Jedi

Thread drift: what are your ideas on the Antal dog bones?

I personally am a fan of toggles in general. Strong, easy to operate in cold/wet conditions.

I was disappointed when I tested Antal's 'lfr with strop' - low strength because the bury was too short (the splice pulled apart). I have not tested their toggle shackle but based on what I saw in their lfr, I would not assume it is properly built - it may be, it may not be.

I like metal toggles to be rubber-coated. It is not hard to dip them; and prefer > 1:1 D/d (and <2:1 not sure if that Antal toggle is or not. You can make your own from aluminum rod pretty easily.

[s/v Jedi]

Originally Posted by Breaking Waves

I personally am a fan of toggles in general. Strong, easy to operate in cold/wet conditions.

I was disappointed when I tested Antal's 'lfr with strop' - low strength because the bury was too short (the splice pulled apart). I have not tested their toggle shackle but based on what I saw in their lfr, I would not assume it is properly built - it may be, it may not be.

I like metal toggles to be rubber-coated. It is not hard to dip them; and prefer > 1:1 D/d (and <2:1 not sure if that Antal toggle is or not. You can make your own from aluminum rod pretty easily.

Yes, I would buy just the toggle and make the shackle from bare Dyneema. I would use a chafing sleeve rather than the double braid. It replaces the stopper knot with eye splices, which should be much easier to make for most. I still mess up the button by taking the wrong strand 25% of the time and I’ve been doing these forever. I may try some of these

[Breaking Waves]

Originally Posted by s/v Jedi

I would buy just the toggle

tylaska makes a line of them . . . https://www.velasailingsupply.com/ou...ska-dog-bones/

You can make a toggle shackle that is in fact 'full strength' (eg 400%) - just need to make sure you get > 1.2:1 bend radius on both the toggle and the loop (I usually add some sleeve to the 'neck' the loop goes around to bulk it up a little, may not be needed but makes me feel good).


there are also some (round) button's available. I have never tried them. Idk the pros or cons vs toggles. I would guess toggles are generally all-around better, but have no direct experience with the buttons.

[Benz]

Originally Posted by s/v Jedi

Thread drift: what are your ideas on the Antal dog bones?

I make a lot of these but with dyneema cover all over: it's hard to explain but there's several passes of thinner line--the amount of laps determines the strength--inside a dyneema cover. You can make them either as a plain loop, or as a single stalk with an eye at each end. One of these eyes can be formed around the toggle.
I began playing with these more than a decade ago, using hardwood toggles to connect things on my boat; now there's lots of different commercially available toggles not only in Alu., but in stainless, titanium, and bronze.
Testing indicates that whatever the strength of the loop, the toggled closure takes away some strength--we calculate a 20% loss which gives a healthy margin.
The covered loop was originally developed by Yale in the days when Spectra was new, and that product is still sold by Harken as 'Loups' You might see the white cover with magenta-coded flecks here and there. Now you can get SK99 Dyneema with a silicone coating from Marlow called 'Lashline' in various sizes which is meant to be used inside of cover in this way.
I think the toggled closure is far superior to any knot for ease of use; the disadvantage is that it requires a metal (or wooden) part.
I'd post some pics, but I really don't know how...no doubt someone techy will find some photos of this to post.

[Breaking Waves]

Originally Posted by Benz

Marlow 'Lashline' .

It is interesting stuff - I have been meaning to test whether the silicon actually measurably reduces sliding friction and increases the equality of leg tension (or if it is just marketing). I have not seen any data on it from other sources.

What do you do to join/terminate the two ends of the multiple passes? Way back when I tested quite a number of 'clever' options but in the end I just use a simple knot