An alternative method for tensioning dyneema rigging

[GILow]

Following.

Aside from the cost, I am interested in these from a weight perspective. With discontinuous rigging on a 44 footer, the turnbuckles represent a significant weight aloft.

[peb]

Originally Posted by GILow

Following.

Aside from the cost, I am interested in these from a weight perspective. With discontinuous rigging on a 44 footer, the turnbuckles represent a significant weight aloft.

I am very busy right now, but in the back of my mind, I have been thinking about how one of these could be designed. It's not as straightforward has first appears. I will try to summarize my thoughts in a few days. Who knows, maybe together we can come up with an idea that could be relatively easy to fabricate.

[sailingharry]

Appreciate your efforts on this. While I do not have plans, at least in the near term, to go to synthetic rigging I have been following the concept with interest.
Looking at samples of these online, they look pretty robust. Were yours cast aluminum? Breaking them certainly seems unexpected.
One potential upside to using these is that if the ends of the lashing are terminated on parts of the rigging, a failure of the tensioning device is perhaps not catastrophic (depending upon just how many turns are on it). Suddenly gaining 2 in the length of your shroud is much better than suddenly losing all of the shroud.
Would it be worth doing one more test setting it up in line as designed rather than discontinuous lines as you did it? Or was the failure unrelated to that?

[PippaB]

The design becomes somewhat simpler if you look at a terminal fence tensioner rather than a midline tensioner. For a lashing use case, do we really need a slot that weakens everything but allows the tensioner to be applied after the fact? If you have an axle with a hole, through which the lashing is passed before you tie it off then you can have a solid axle. Also much easier to chamfer the lead-in, lead-out from the hole to avoid sharp bends without serious impact to strength.

I think the tricky part is the system used to lock the rotation, as that will bear on the lashing line, so needs to be smooth and of decent radius as well, unless you go with a style that has a pawl.

Maybe a mashup of the original, with the axle style of below (I would not copy the below where the lines get terminated on the device, then you are relying on the strength of the device - but these are US$5-6 each in base metal, so...). You can use these midline by passing the wire (lashing) through both the axle and the terminal end, and not crimping the terminal. That gives the lever arm to prevent rotation.

[catsketcher]

Thanks for the testing. I saw one of the alloy tensioners on a fence just after the thread started.
I was just looking at a 20 year old performance cruiser trimaran with Dux rigging. It didn't use any special frapping knot. What is the reason for them?

[catsketcher]

Here's a picture

[s/v Jedi]

Originally Posted by Franziska

Fair enough.

Don't get me wrong in the following I appreciate your testing and thoughts.

Just hope someone else does it instead of a company slapping an expensive "marine" price tag on it and then trying to get it patented.

If the original is really 5$ I would not think 100$ is a reasonable price tag even if it's from another material and someone ran a few calcs on it.

Originally Posted by peb

Yea, I get that $100 is expensive, I was just imaging what colligo would likely charge. OTOH, in a case such as this, I can kinda see why it would be that price. Takes a fair bit of engineering work and tooling to put into production even simple parts, then one has to test the prototypes and deal with liability insurance. All this for a pretty small market base. Also seeing as the main competitor are turnbuckles, and those things are not cheap.

But yea, I would love to go buy 9 of them for $10 a piece. I would likely be willing to pay more if they really worked and one did not have to deal those frapping knots (or whatevery they are called).

Of course community efforts is more than others doing it

Depending on design, you can now do so much yourself with a computer then let a company like https://sendcutsend.com/ make it out of the material of your choice.

I did a similar thing with the switch panels I designed.

[peb]

Originally Posted by s/v Jedi

Of course community efforts is more than others doing it

Depending on design, you can now do so much yourself with a computer then let a company like https://sendcutsend.com/ make it out of the material of your choice.

I did a similar thing with the switch panels I designed.

Well, as other posts have shown, yes community effort is often better.

Will check out sencutsend, thanks for the suggestion.

[peb]

Originally Posted by sailingharry

Appreciate your efforts on this. While I do not have plans, at least in the near term, to go to synthetic rigging I have been following the concept with interest.
Looking at samples of these online, they look pretty robust. Were yours cast aluminum? Breaking them certainly seems unexpected.
One potential upside to using these is that if the ends of the lashing are terminated on parts of the rigging, a failure of the tensioning device is perhaps not catastrophic (depending upon just how many turns are on it). Suddenly gaining 2 in the length of your shroud is much better than suddenly losing all of the shroud.
Would it be worth doing one more test setting it up in line as designed rather than discontinuous lines as you did it? Or was the failure unrelated to that?

I suppose my failure may have been due to not using it as designed. I had planned on doing two different tests, but ran out of time and the first one failed. The reason I terminated the lashing on the device was because all I did not have any proper deadeyes to use and was just using some sailmakers thimbles for both the deadeye end and as the shroud terminator, and didn't want any knots on the thimbles to interfere with the tensioning. Thought it might tighten better that way.

My other problem is that I likely bought the wrong tensioners. I ordered a bag off of Amazon, they were aluminum, but I think they were knock-offs of the actual Gallagher ones. Don't know if any difference in quality, but its worth investigating. And you are certainly correct that it provides a little of a failsafe.

I will likely order a bag of 5 of the Gallagher tensioners and try those the proper way. But I am not for sure when I will have time to do so, you guys may need to be patient Its certainly worth the $30/bucks and another try. If nothing else to learn a little more.

[peb]

Originally Posted by PippaB

The design becomes somewhat simpler if you look at a terminal fence tensioner rather than a midline tensioner. For a lashing use case, do we really need a slot that weakens everything but allows the tensioner to be applied after the fact? If you have an axle with a hole, through which the lashing is passed before you tie it off then you can have a solid axle. Also much easier to chamfer the lead-in, lead-out from the hole to avoid sharp bends without serious impact to strength.

I think the tricky part is the system used to lock the rotation, as that will bear on the lashing line, so needs to be smooth and of decent radius as well, unless you go with a style that has a pawl.

Maybe a mashup of the original, with the axle style of below (I would not copy the below where the lines get terminated on the device, then you are relying on the strength of the device - but these are US$5-6 each in base metal, so...). You can use these midline by passing the wire (lashing) through both the axle and the terminal end, and not crimping the terminal. That gives the lever arm to prevent rotation.

Worth thinking about. Certainly the hole through the axle as opposed to the slot (which weakens both the axle and the disk on the same side) is valid.

[AKA-None]

Originally Posted by PippaB

The design becomes somewhat simpler if you look at a terminal fence tensioner rather than a midline tensioner. For a lashing use case, do we really need a slot that weakens everything but allows the tensioner to be applied after the fact? If you have an axle with a hole, through which the lashing is passed before you tie it off then you can have a solid axle. Also much easier to chamfer the lead-in, lead-out from the hole to avoid sharp bends without serious impact to strength.

I think the tricky part is the system used to lock the rotation, as that will bear on the lashing line, so needs to be smooth and of decent radius as well, unless you go with a style that has a pawl.

Maybe a mashup of the original, with the axle style of below (I would not copy the below where the lines get terminated on the device, then you are relying on the strength of the device - but these are US$5-6 each in base metal, so...). You can use these midline by passing the wire (lashing) through both the axle and the terminal end, and not crimping the terminal. That gives the lever arm to prevent rotation.

This is what I was envisioning as I had no end of trouble with the plastic mid wire tightening
Plastic parts failed too easily

[Benz]

Originally Posted by catsketcher

Thanks for the testing. I saw one of the alloy tensioners on a fence just after the thread started.
I was just looking at a 20 year old performance cruiser trimaran with Dux rigging. It didn't use any special frapping knot. What is the reason for them?

The "Special frapping knot" is really just a round seizing done in thin twine (looks like Samson Lash-it in most vids). It prevents the legs of the lanyard from slipping back once you take the fall off the winch/tackle/come-along to which it's been led until you can hitch it off securely.
Another quicker method to prevent leg slippage is to double a loop of line around the legs of the lanyard and twist it like a Spanish windlass with a belying pin or screwdriver handle until it won't go any more. When it's tight enough, the lanyard legs won't slip and you can hitch off the tail of the lanyard.

[peb]

Originally Posted by Benz

The "Special frapping knot" is really just a round seizing done in thin twine (looks like Samson Lash-it in most vids). It prevents the legs of the lanyard from slipping back once you take the fall off the winch/tackle/come-along to which it's been led until you can hitch it off securely.
Another quicker method to prevent leg slippage is to double a loop of line around the legs of the lanyard and twist it like a Spanish windlass with a belying pin or screwdriver handle until it won't go any more. When it's tight enough, the lanyard legs won't slip and you can hitch off the tail of the lanyard.

D you have a picture of the second method? I don't quite understand (I am rather slow at my age).

[s/v Jedi]

Originally Posted by Benz

The "Special frapping knot" is really just a round seizing done in thin twine (looks like Samson Lash-it in most vids). It prevents the legs of the lanyard from slipping back once you take the fall off the winch/tackle/come-along to which it's been led until you can hitch it off securely.
Another quicker method to prevent leg slippage is to double a loop of line around the legs of the lanyard and twist it like a Spanish windlass with a belying pin or screwdriver handle until it won't go any more. When it's tight enough, the lanyard legs won't slip and you can hitch off the tail of the lanyard.

No, that is only part of the function and your alternative does not replace the frapping knot.

When a strand in a lashing breaks due to damage or a manufacturing fault, the frapping knot will prevent the whole lashing undoing itself and keeps the lashing intact with the strands that didn’t break and should still have more than enough strength to carry the load.

Also, after you hitch off the tail of the lashing, you take the Spanish windlass off, which transfers the load to the tail of the lashing which gets pulled tight and thus gives a little (or more) and now the tension is off.

For all but the smallest cruisers, a turnbuckle makes much more sense. Today the rigger posted about new fittings that look like Stalok fittings except are for Dyneema, making things very easy as they provide the same attachments as stainless steel rigging.

[Sos]

Was it an aluminium or plastic one you tested?

If the ali ones are strong enough it would be easy to buy them as supplied and then get them polyester powder coated. Would last ages then.