Dyneema Standing Rigging a 50' Sloop, Questions for those who have made the swap

[Snowpetrel]

Originally Posted by Panope

Is there concern that synthetic rigging may burn or melt in the event of lightning strike? (sorry if it has already been discussed)

Steve

Good question.

I am thinking it shouldn't be a problem with Dyneema rigging unless there was no better path to earth at all. AFAIK The stuff doesn't conduct electricity easily. Maybe if its had a copper wire inside it for an antenna and a wooden mast?

Carbon rigging and carbon masts are a different matter altogether, carbon being a half decent conductor. Easy enough to protect it, at least I hope so since most modern airliners have lots of carbon laminate keeping me in the air...

[mitiempo]

Originally Posted by CareKnot

Btw, just a heads up; the product table in your link is for determining splicing strength, not breaking strength.

As Samson does for all ropes. A proper splice in Dyneema (Amsteel and its variants) gives 90 to 100% of the rope's strength.

Samson's 2 1/2" has a minimum strength of 411,000 lbs.

The rope you found, if the size is correct at over 4" diameter, is one of the weakest synthetics around if your numbers are to be believed.

Samson's AS-78 in 4 1/2" size, has a minimum strength of over 2,000,000 lbs.

Product

There is something very wrong with your numbers.

[CareKnot]

Hi mitiempo,

Yes I made an error. If you read the thread, you would know that I already admitted to my error, but alas, I have no way to edit it.

But thanks for pointing it out.

Again.

Oh! Thanks for the heads up about Samson ropes. As other posters here and elsewhere have already pointed out, different suppliers use different strength numbers for different reasons. Some even do it for marketing purposes. Can you imagine?

Nice taking to you. Feel free to hound me about my imperfections anytime.

Originally Posted by mitiempo

As Samson does for all ropes. A proper splice in Dyneema (Amsteel and its variants) gives 90 to 100% of the rope's strength.

Samson's 2 1/2" has a minimum strength of 411,000 lbs.

The rope you found, if the size is correct at over 4" diameter, is one of the weakest synthetics around if your numbers are to be believed.

Samson's AS-78 in 4 1/2" size, has a minimum strength of over 2,000,000 lbs.

Product

There is something very wrong with your numbers.

[Stumble]

Careknot,

Reputable suppliers do not just make up their strength numbers, they use third partytesting to determine them, and make those tests available to purchasers who request them. You can do what you want, but the strength numbers from this supplier are substantially weaker than for sk-75 lines such as amsteel, and not even close to the strength of sk-78.

10mm Sk-78 has an expected mbl in the 12,000 KG range along with lower stretch and creep. The company you posted claims a mbl of 9450kg. But their strengthis all over the place. In some cases it is higher for the same mbl as Amsteel, in other places it is far lower. So either their testing is poor, their product repeatability is poor, or they use different designs for different size line.

My guess is if they are a licensed supplier (and I would check) they are using sk-75 and have a piss poor marketing department. But this product is not a replacement for standing rigging, though it may be one for Amsteel.

Why a range? Because different suppliers use different throat angle on the weave.

[robwilk37]

again, at this price its worth investing in your own testing and cert... couple hundred bucks at a reputable lab. you could cut your own lengths out of the spool and test a dozen samples throughout the run to check consistency. im a big fan of buying from the source but you have to absorb a little risk and do your own homework as a byproduct of the savings. no reason you couldnt up the diameter a mil or two either.

worst case it fails miserably and you sell it off to others who have a less critical application, and likely at least break even.

[packeteer]

It's very common with Chinese companies to have poor English docs. Either way, "buyer beware" has never been more appropriate

[CareKnot]

Stumble,

I never said that anyone made up strength numbers. You may wish to read my post again.

On the other hand, I did make an obvious error on the strength number for the 120mm SK78. It was a HUGE MISTAKE. I typed an obvious error. Get it? The error was mine, not theirs.

Shame I can't edit that post. Because now I have to listen to the same crap ad nauseum, from every person too lazy to read my repeated protestations that it is my error. It's really stupid that several people want to blame the supplier for my error and not me!

Moving on, I think you misjudge this company. You seem to attribute the inconsistencies in their literature to quality control and technical issues. Personally, I think they just need a native English speaker on staff. After all, they partner with DSM, the patent holder for Dyneema and have gross sales in the 50 to 100 million dollar per annum range since the company was founded in 2013 (if memory serves). Not exactly a fly-by-night lightweight. But what do I know?

You also seem to think that SK78 is stronger than SK75. The difference between SK75 and SK78 is based on creep, not strength. In strength they are identical.

Originally Posted by Stumble

Careknot,

Reputable suppliers do not just make up their strength numbers, they use third partytesting to determine them, and make those tests available to purchasers who request them. You can do what you want, but the strength numbers from this supplier are substantially weaker than for sk-75 lines such as amsteel, and not even close to the strength of sk-78.

10mm Sk-78 has an expected mbl in the 12,000 KG range along with lower stretch and creep. The company you posted claims a mbl of 9450kg. But their strengthis all over the place. In some cases it is higher for the same mbl as Amsteel, in other places it is far lower. So either their testing is poor, their product repeatability is poor, or they use different designs for different size line.

My guess is if they are a licensed supplier (and I would check) they are using sk-75 and have a piss poor marketing department. But this product is not a replacement for standing rigging, though it may be one for Amsteel.

Why a range? Because different suppliers use different throat angle on the weave.

[Stumble]

Careknot,

I was not using your numbers I was pulling directly from theirs. The strength numbers they posted do not conform to a standard spread for sk-75. Some of their strength numbers are exactly in the range of whatyou would expect for sk-75, some are substantially weaker. Thus my concern about their manufacturing process or testing process. I am pulling directly from their brag sheet about their products here https://www.alibaba.com/product-deta...56548.html?s=p

Looking at these numbers and comparing them to Amsteel Blue Sk-75 which is the industry standard...

Line........Size......MBL (kg)...weight(kg/100m)
Amstel....1/4"......3,500.......2.4
Chinese...1/4".....3,800........2.6

So these two ropes that are nominally the same size are within the same range of strength, but the Chinese supplier's line is really about 20% bigger as evidenced by the difference in weight per foot. Some amount of difference here is typical because on is probably building to a metric size the other to a standard size, but that difference in nominal strength is pretty large.

So let's look at a different supplier who only builds in metric sizes (which is what I am guessing the Chinese are using but this time using Marlow Excel D12 (sk-75).

Line........Size......MBL (kg)...weight(kg/100m)
Marlow....6mm.....3,487.......1.77
Chinese...6mm.....3,250.......2.14

Here it's even more pronounced, the metric size is heavier and weaker indicating either a poorly formed rope or a substandard fiber.


The factremains the Chinese manufacturers brag sheet simply does not indicate a line that is as strong as mainline European or US manufacturers. I don't know what's going on with them, but the more I think about it, I am pretty sure there was a product sk-68(?) that has generally been discontinued that is pretty close to what they are displaying. So it may be thatthey are still selling this older line chemistry (which is dyneema) but is substantially weaker than the current chemistry.


Finally SK-78 is more creep resistant than sk-75, but it is also substantially stronger at the same size. Part of the heat treatment process alignes the chemical bond to make a stronger line. The creep and stretch resistance are also part of this process. Sk-78 is heat treated and annealed sk-75, and has substantially different material properties. It's stronger, stretches less, and creeps less. They are not at all the same when compared side by side. You can actually feel the difference, the sk-78 is much, much stiffer, it actually feels a big like wire and can self support itself.

[kmacdonald]

With synthetics you design for stretch and creep to equal that of stainless steel. The strength of synthetic will be much more than that of the stainless steel.

You can use either SK-75 or SK-78 but the SK-75 will need to be a larger diameter to meet the same stretch and creep criteria as SK-78.

[CareKnot]

Thanks Greg for the update. While I agree in principle with most of what you said, I still think that there is more to this than meets the eye.

It seems the discrepancies in strength ratings are based on our perception of the product, not the fiber. It is a given that the fiber, in order to meet manufacturing contract specs, should be consistent across the board. These folks expressly stated in their company literature that they are authorized to offer DSM warranty for Dyneema products. That speaks volumes.

Perhaps the thing to do is write both this company and DSM directly and ask about the perceived differences in the product specs.

I know. That's just crazy talk.

As for me, I think I'll bow out. This is much more exercise than I ever wanted over just offering a suggestion to save the community a little money. When I'm ready to make an order, I think I'll just go solo.

Peace out...

[robwilk37]

care knot...
i thank you for the heads up. one of my winter projects is to spec out the rig and source the materials and you may well have saved me some time. im ready to pull the trigger on a spool and do my own testing, i think at that price its worth the extra leg work. will let you know what i find...

[CareKnot]

Hi Rob,

CareKnot will be my new boat's name. You can call me Phillip.

Rob, I am a dedicated proponent of creative laziness. Tom Sawyer is my hero. Why paint the fence myself, when you can have other people pay me for the privilege, right? So I have no intention, "...to spec out the rig and source the materials." Why not have someone else do it for you?

Since my shopping involves production boats suited to cruising, I'm thinking of contacting this Chinese company, requesting their proposals for racing and cruising standing rigging refit 'kit' solutions as a marketing research project. I will be asking them, given a certain context, what they can provide. Understand?

I am going to ask them to quote for me, proposed standing rigging solutions from alternative Dyneema products for a few popular, high production run cruising sailboats according to their standard rigging and furling alternatives. I want to know the cost if they do the eyelet splices and supply the appropriate hardware. I will ask what my choices are. I'll have their engineers spec all the rigging choices for me, before I buy a thing.

Best of luck to you!

Originally Posted by robwilk37

care knot...
i thank you for the heads up. one of my winter projects is to spec out the rig and source the materials and you may well have saved me some time. im ready to pull the trigger on a spool and do my own testing, i think at that price its worth the extra leg work. will let you know what i find...

[Sysunday]

Btw: dynaOneMax is one manufacturers name of dyneema using the dyneema DM20 fiber.
I bought the stuf here: http://shop.seileundmeer.de/XTReme/D...ro-Static.html

[Sysunday]

Dynex dux is finished as a brand name, Hampidjan now calls it "Dynice Dux". Hampidjan is not the manufacturer nor the inventor if the fiber; that is DSM in the Netherlands.
During the last two years I did an extensive orientation on the different dyneema variants for the use of shrouds. For that I visited DSM and got a lot of information and help from them with my project.
I ended up with using DSM's DM20. This is a quite recently introduced dyneema fiber. Specifically made with the lowest creep, with accepting a (somewhat) smaller breaking strength.
The dynice Dux ropes are nothing more toen SK75 which is heat-annealed an compressed in its diameter. You can check this: 6mm "normal" dyneema weights some 23 gram per meter, the Dux some 32grams per meter: you simply get some more weight in the same diameter.
Dyneema has three sorts of stretch: 1. "construction", 2. "Normal", and 3 " creep". Construction stretch is simply caused by the way the rope is constructed, the "weave" of the rope: if the rope consisted of all and only parallel fibers there would be none of this. Normal stretch is the (very low) elastic like stretch of the fiber. Creep is not real stretch but a slow elongation of the fibers on a molecular level and ONLY occuring with tension above around 30% of the breaking strength.
These three sorts of stretch have to be taken into account when deciding for the use of shrouds: breaking strength is in fact no issue, not even if you swap same diameter steel cable for dyneema. Key is to size for creep.
In that the New dyneema fiber DM20 excels: by far the lowest creep of all variants of dyneema.
Herewith some pictures of my project which I finished last March. I used 7mm dyneema DM20 for all my shrouds, fore and back stay. Forestry got a cover of dyneema for protection, as did the shrouds at the spreader ends.
I used tackles for adjusting for construction and "normal" stretch, and turnbuckles for finetuning. After some adjustment during the first days of sailing the first summer I did not need to make more adjustments which might have been caused by creep.
My forestay (lower end of protection not net finished):


All soft hanks, i made some 40 of them:
In use:

[Sysunday]

Dynex dux is finished as a brand name, Hampidjan now calls it "Dynice Dux". Hampidjan is not the manufacturer nor the inventor if the fiber; that is DSM in the Netherlands.
During the last two years I did an extensive orientation on the different dyneema variants for the use of shrouds. For that I visited DSM and got a lot of information and help with my project.
I ended up with using DSM's DM20. This is a quite recently introduced dyneema fiber. Specifically made with the lowest creep, with accepting a (somewhat) smaller breaking strength.
The dynice Dux ropes are nothing more toen SK75 which is heat-annealed an compressed in its diameter. You can check this: 6mm "normal" dyneema weights some 23 gram per meter, the Dux some 32grams per meter: you simply get some more weight in the same diameter.
Dyneema has three sorts of stretch: 1. "construction", 2. "Normal", and 3 " creep". Construction stretch is simply caused by the way the rope is constructed, the "weave" of the rope: if the rope consisted of all and only parallel fibers there would be none of this. Normal stretch is the (very low) elastic like stretch of the fiber. Creep is not real stretch but a slow elongation of the fibers on a molecular level and ONLY occuring with tension above around 30% of the breaking strength.
These three sorts of stretch have to be taken into account when deciding for the use of shrouds: breaking strength is in fact no issue, not even if you swap same diameter steel cable for dyneema. Key is to size for creep.
In that the New dyneema fiber DM20 excels: by far the lowest creep of all variants of dyneema.
Herewith some pictures of my project which I finished last March. I used 7mm dyneema DM20 for all my shrouds, fore and back stay. Forestry got a cover of dyneema for protection, as did the shrouds at the spreader ends.
I used tackles for adjusting for construction and "normal" stretch, and turnbuckles for finetuning. After some adjustment during the first days of sailing the first summer I did not need to make more adjustments which might have been caused by creep.
My forestay (lower end of protection not yet finished):


All soft hanks, i made some 40 of them:
In use: