Jordan Series Drogue in Dyneema

[Breaking Waves]

Originally Posted by fxykty

Next question - how long the taper?

Theoretically correct answer - to be 'totally safe and sure' - proper tapers are around 20x, and you want a 'full strength' section in the middle of say 30x, so 20+20+30= 70x for total insert. That is 'conservative' (eg static lab testing suggests you can do shorter but it is nice to have the extra in the vagaries of the real world).

I have to admit that neither Brion nor I made our insert tapers that long in our testing - we did more like 15x taper on each end with 15x full section in middle (45x total). With short tapers like this, the key is a quick but smooth taper of the bulk of the rope to the last two strands and then a very careful taper of the last two strands - unravel them to filaments and then taper them in 6 steps each cut on an angle, totally ensures there is no stress riser there. There is testing that indicates that these shorter tapers are still all good when done carefully (I think it was Yale that did specific testing on the most efficient method). 45x total length normally would be sufficient, but because you have taper at both ends you have a quite short 'full strength' middle section and that does give me a little pause - I suspect we would have been stronger with 30x middle sections.

----------------------------------------------

For reference, usually, for 'normal' buries (with only one side tapered), the full taper is counted as part of the bury length, and that is how it is reported in all the testing I have seen (including my own). I realize here I have been using perhaps inconsistent terminology because I count only the middle full strength section for these inserts. They are functionally different because in a 'normal' bury the strands of the full strength section are still attached to the main line, while in the insert they are just 'floating' so they need enough bury on their own to 'set/grab'.

30x is the tested minimum bury length to set/grab full strength in lab static load and 45x is the shortest used in real life to compensate for dynamic loads and real-life vagaries (and as you know up to 72x).

[Seaworthy Lass]

Originally Posted by Breaking Waves

Theoretically correct answer - to be 'totally safe and sure' - proper tapers are around 20x, and you want a 'full strength' section in the middle of say 30x, so 20+20+30= 70x for total insert. That is 'conservative' (eg static lab testing suggests you can do shorter but it is nice to have the extra in the vagaries of the real world).

I have to admit that neither Brion nor I made our insert tapers that long in our testing - we did more like 15x taper on each end with 15x full section in middle (45x total). With short tapers like this, the key is a quick but smooth taper of the bulk of the rope to the last two strands and then a very careful taper of the last two strands - unravel them to filaments and then taper them in 6 steps each cut on an angle, totally ensures there is no stress riser there. There is testing that indicates that these shorter tapers are still all good when done carefully (I think it was Yale that did specific testing on the most efficient method). 45x total length normally would be sufficient, but because you have taper at both ends you have a quite short 'full strength' middle section and that does give me a little pause - I suspect we would have been stronger with 30x middle sections.

---------------

I know very little work has been done using reinforced sections, so much of the design needs to be educated guesswork based on other testing, but my thought process when selecting bury length for the reinforced section was based on the principle that system strength is only as good as its weakest point.

If the tails are buried, the tapering is generally only around 10 x line diameter if the recommended minimum tail length of 30 x line diameter is used. This is not the weak point in this design, so why make the minimum taper 20 x line diameter for the reinforced piece?

In addition, the higher losses in strength with a poor taper are of primary concern when this section is taking full load. In the case each taper is only subject to a quarter of the load and even with a reinforced piece the shackle’s breaking point will be well short of 4 x line strength.

I doubt that 20 x line diameter is needed for reinforcement of the eye. 10 x is likely to be way more than plenty. It will be the total length of insert, not the taper length that will be critical.

Just tossing around ideas.

SWL

[Seaworthy Lass]

By the way, when I made my first one I selected 40 x line diameter as the length for the insert, but I have upped this to 60 x (40 for the centre and 10 for each taper). My reasoning for this was that from the apex of the eye each bury may be best considered individually. 30 x has been the minimum determined in the past as a bury length, so I use twice this, one for each “side”. Also, I have found the shackle handles better having the insertion a bit longer.

My need for new soft shackles is slowing down so not many have been made in the last few months, but all of them have been reinforced. I like the superior handling for thinner line. I figure it uses very little extra material and it is quick to do, so why not .

SWL

Edited to add: The lengths I am discussing refer to the same diameter line being used for the insert (this is the data we have for splices). I guess that if thinner inserts are used, longer lengths may be needed to maximise strength.

On the other hand, I think we may not need to seek peak strength for the insert, as when the eye is reinforced, the weak point may well revert to the stopper long before the load is 400% of line strength, the maximum theoretical system strength.

[Seaworthy Lass]

This was the latest reinforced soft shackle made.

The reinforced portion was added purely for handling, as I find 3 mm too thin for good handling, even with my thin fingers. The eye is is harder to open and the use of a finger nail to do this damages the fibres over time. Reinforcement fixes this issue.

Also, the shackle is much easier to operate single handed if the eye is reinforced. The eye conveniently then stays open when let go to reach for the stopper. I only have one hand to operate a soft shackle when raising our swim platform, so reinforcement has been particularly valuable in this instance.

For lots of “lightweight” use on board 3 mm is way more than strong enough (eg the one below is one of a pair used on my hammock) so I have found it very useful being able to improve the handling.

Specifications:
3 mm Stealth-Super 12 line
2 mm Dyneema reinforcement inserted at the eye (200 cm long, 120 mm central portion, 40 mm taper each end)
“High strength” design using a Brion Toss Button stopper.
A crossover of the legs added about 100 mm from the eye simply so that the legs did not flop around as much.

SWL

[Breaking Waves]

Originally Posted by Seaworthy Lass

Just tossing around ideas.

all good. You may well be right. I am just leaning toward prudence for this application.

The use of the insert for strop hitch reinforcement is mechanically different than its use in soft shackles or the taper in bury loops.

In the soft shackle, the insert is mechanically captured in the cross-over. In the end loop, the taper is only one-sided and all the strands are mechanically connected to the main line on the other side. So in both these cases, we are not entirely depending on the Chinese finger squeeze to transfer load to the insert.

In the strop hitch case, we are depending entirely on the squeeze to transfer load. And in the series drogue/bridle specific case, it struck me that longish loops would cause no problem. So, I thought it prudent to suggest a conservative approach.

I do agree with your thought that it may well be longer than the minimum necessary to get the strop hitch up to 100% system strength. The soft shackle testing does suggest that potential.

We did enough testing to know the inserts 'work' . . but we did not do enough testing to know what is the exact way to optimize them. 20x is a fid length, and that is generally not an uncommon length for tapers. So I don't feel like in this application it is necessarily overkill.

--------------------------------------------------------------
related, but also sort of an aside . . . . one thing I have learned and repeatedly been hammered in the head from test results is . . . .dyneema (and high mod textiles in general) like and reward simple and straightforward design. Adding clever features so often also adds the potential to distort weave or create uneven length legs/segments and can end up in practice actually significantly decreasing strength rather than adding the theoretically expected gain. It is always prudent to be a bit dubious of clever features.

In the case of the strop hitch, if there is any question/concern about strength, I still think, if it is possible/practical, the preferred answer is to upsize/up-spec the line. I do think we have enough testing to be confident that the insert 'works' in actual practice (in the soft shackle application) and not just in theory. All of the samples we tested with inserts were significantly stronger than the samples without.

In the soft shackle insert case, they have an effect in addition to the strength increases. They make the look stiffer to work. Some people like that and some people don't. Might be beneficial in some particular applications and less so in others. I personally generally don't particularly like it, but could imagine an application situation where I might want it. I'm also in the 'camp' that generally feels the 'stronger' designs (with appropriate line size) are 'more than strong enough for 99.9% of yachting applications. And the insert does increase the loop size so that it does not slip thru chain links as easily as the base design.

[Seaworthy Lass]

Originally Posted by Breaking Waves

all good. You may well be right. I am just leaning toward prudence for this application.

The use of the insert for strop hitch reinforcement is mechanically different than its use in soft shackles or the taper in bury loops.

In the soft shackle, the insert is mechanically captured in the cross-over. In the end loop, the taper is only one-sided and all the strands are mechanically connected to the main line on the other side. So in both these cases, we are not entirely depending on the Chinese finger squeeze to transfer load to the insert.

In the strop hitch case, we are depending entirely on the squeeze to transfer load. And in the series drogue/bridle specific case, it struck me that longish loops would cause no problem. So, I thought it prudent to suggest a conservative approach.

I do agree with your thought that it may well be longer than the minimum necessary to get the strop hitch up to 100% system strength. The soft shackle testing does suggest that potential.

We did enough testing to know the inserts 'work' . . but we did not do enough testing to know what is the exact way to optimize them. 20x is a fid length, and that is generally not an uncommon length for tapers. So I don't feel like in this application it is necessarily overkill.

Lots to think about. Thanks.

Adding some extra length to the insert and carefully tapering is certainly a safe thing to do if maximum strength is needed, but I am curious about the minimum limits .

As far as I can see, the case of reinforcing the eye in a strop hitch is similar to reinforcing the eye of a soft shackle. I think the entrapment at the crossover point in the soft shackle has a negligible effect. I tend to think the main difference between the two is in the location of the compression points (and of course that in a soft shackle the reinforcement’s taper experiences only a quarter of the total load and in an eye spice it is half).

I think that the total length of the insert is the critical bit, not the taper. From memory if a bury is not just left un-tapered, but eye wateringly actually sticks out of the line, then the strength only drops to 80% of line strength. The load in the portion where the insert taper occurs in a reinforced eye splice is only 50% of the load on the rest of the line. Why will tapering make any difference at all?

I will not stop tapering with care (nor am I going to take apart the splices at our drogue’s bridle junction, as the line strength I used was not on the marginal size) but subject still interests me .

SWL

[Seaworthy Lass]

Originally Posted by Breaking Waves

--------------------------------------------------------------
related, but also sort of an aside . . . . one thing I have learned and repeatedly been hammered in the head from test results is . . . .dyneema (and high mod textiles in general) like and reward simple and straightforward design. Adding clever features so often also adds the potential to distort weave or create uneven length legs/segments and can end up in practice actually significantly decreasing strength rather than adding the theoretically expected gain. It is always prudent to be a bit dubious of clever features.

In the case of the strop hitch, if there is any question/concern about strength, I still think, if it is possible/practical, the preferred answer is to upsize/up-spec the line. I do think we have enough testing to be confident that the insert 'works' in actual practice (in the soft shackle application) and not just in theory. All of the samples we tested with inserts were significantly stronger than the samples without.

I missed this bit.

Yes, I agree entirely. Complicating the design only has the potential for leading to more errors, particularly in inexperienced hands.

For anyone making very few soft shackles, ease of making and simplicity are the most important considerations when selecting a design.

For anyone starting off, my advice would be to make the first dozen or so using a diamond stopper and a Kohlhoff style and if extra strength is needed, then simply bump up line size.

Originally Posted by Breaking Waves

In the soft shackle insert case, they have an effect in addition to the strength increases. They make the look stiffer to work. Some people like that and some people don't. Might be beneficial in some particular applications and less so in others. I personally generally don't particularly like it, but could imagine an application situation where I might want it.

I have found it significantly better for 3 mm soft shackles. It diminishes after that and at some point (possibly around 6-8 mm line size) it starts to become worse.

Originally Posted by Breaking Waves

I'm also in the 'camp' that generally feels the 'stronger' designs (with appropriate line size) are 'more than strong enough for 99.9% of yachting applications. And the insert does increase the loop size so that it does not slip thru chain links as easily as the base design.

Agreed .
But isn’t it nice to experiment and improve .

SWL