Dyneema rig goes slack in the cold??? Not for me!!

[Jeff on Aurora]

Well, my investigation into Dyneema rigging as an alternative to stainless steel didn't last very long. This video of a cruising boat in 30 degree temperatures shows how their rigging went so slack that the boat can't be sailed until the temperatures warm up. Whiskey tango foxtrot!

https://www.youtube.com/watch?v=-Uye1oWpZOw

Apparently, Dyneema actually EXPANDS when cold, unlike just about any other material I've ever encountered.

Has anyone with synthetic shrouds come up with a work-around for this?

I'm heavily inclined to stay with trusty SS.


Thanks!

[rslifkin]

I doubt the rigging is expanding. The mast will shrink in the cold and if the rigging doesn't also shrink enough, then it'll become slack.

[Jeff on Aurora]

Originally Posted by rslifkin

I doubt the rigging is expanding. The mast will shrink in the cold and if the rigging doesn't also shrink enough, then it'll become slack.

From what I'm reading, it actually IS the Dyneema expanding, weird, huh? From another post by the "Rigging Doctor"

"Dyneema experiences a negative linear thermal expansion coefficient in the direction of the fiber. What this means is that it stretches as it cools. Minor differences in temperature will not create an appreciable difference in length, leading to loss of tension, but more drastic differences will.
What this means is that your rigging will go slack during the winter which is of little consequence since the sailing season ends before it gets cold enough to notice the difference. I tensioned my rigging when it was between 60F and 80F. Now that the temperature has dropped down to below 20F, we are seeing an appreciable slackness in the standing rigging. "

Check out the linked video from my first post - you won't believe how much slack and wobble there is in the rig. Start watching at 6:00 into the vid. Completely unusable for sailing.

J.

[Benz]

I tune my synthetic rig when it's cold out, then in the summer it gets a tiny bit tighter. As has been mentioned, it may be the aluminum mast shrinking with cold.
Either way, unless you're cruising in places with huge-HUGE-temperature fluctuations, it's hardly the end of the world to give a quick tune when the weather gets cold, if you're hardy enough to sail in sub-freezing temps.
Which I'm not.

[Popeye.Tom]

I know of a small handful of materials with negative thermal expansion coefficients. The two that come to mind are water and natural rubber. (I made a rubber band motor (ring rim and offset center axis) with a heat source when I was in jr. high. Scientific American experiment.)


I was looking into Dyneema for the standing rig on my Pearson 365 ketch. I am in S. Oregon. I have enough delta T that this makes synthetic a non-starter for me.


I do see large enough seasonal swings that I'd have to possibly tighten in late fall and loosen in late spring or risk too loose/over tensioned. In the summer, we can have a 40* delta from overnight low to the day's high.



I need to get the actual coefficient and calculate the tension changes for a cycle. Maybe not so bad. But if he tensioned the rig at 60F and it went that slack at 20F, that is a 40* delta!


RE: Aluminum mast length change... I can calculate the growth or shrink for a 50' stick and post it, if anyone is really curious. BUT, look at how slack their lifeline went in the cold. I don't think the mast extrusion getting shorter had impact on the lifeline! :-P


Cheers,
Tom

[nightowle]

thanks for the info, or should I say - warning? Now I know to steer clear of this for these purposes. I'm in an area that sees enough temperature shifts to warrant concern.

[seandepagnier]

i use dyneema rigging and he is not correct to say you cant sail with it slack.

You can sail just fine with it slack unlike stainless which will work harded from repeated shock loading and requires higher tension to avoid destroying the wire.


Further, if you do adjust it, maybe once or twice a year you can maintain good tension year round. Finally, stainless is a foolish material to use for rigging in most cases. You are better served with galvanized wire if you do not like the downsides of dyneema (cost and vulnerability to chafe or cutting) which is stronger, much cheaper, and lasts longer.

dyneema is just fine with hank on sails, and will last 10 years or much longer without issue. The boat is more stable with less weight aloft and sailing performance is better. The rig is much stronger, and stainless often unpredictibly fails. Anyone seriously considering stainless should use 2205 duplex stainless or some other types of alloy. Using 304 is dangerous, and 316 is still in question however probably reliable if you use the very expensive sta-lok fittings however the cost makes it not really reasonable compared to the superior properties of galvanized which is a fraction of the cost (15 cents vs $2 per ft) and no need for special terminals.

[fxykty]

How much temperature difference and how much length change are we talking about?

We have two 20m x 18mm DUX cap shrouds on our cat supporting an aluminium mast. So far we’ve only gotten 15*C hotter than when last tensioned and we’ve not noticed rig tension getting ridiculously high.

So how much does the temperature need to drop before the rig starts to go slack? And will a few turns of the turnbuckles take care of it? If so, not an issue.

[markxengineerin]

i use dyneema rigging and he is not correct to say you cant sail with it slack.

You can sail just fine with it slack unlike stainless which will work harded from repeated shock loading and requires higher tension to avoid destroying the wire.

Sean, I love what you do with your boats, but have to disagree with a couple things here. You "can" sail a boat with a slack rig, but by doing so, you're increasing the loads on everything else in the system, and not keeping the mast where it would be with a better rig, which will affect performance. You "can" sail a boat with loose string holding the mast up, but that doesn't make it a good idea for most people. The reason for tension in rigs is not only to avoid destroying the wire. There's a good explanation here (from the great book, Illustrated Sail & Rig Tuning by Ivar Dedekam, which another forum member recommended to me when I had questions on this topic)

When rigging material is switched from stainless to dyneema, tension should be set the same as originally designed for, to maintain the intended sailing performance.

I created this spreadsheet to study the effect of temperature on my synthetic rig / aluminum mast combo.

The results are shocking to me, and I think the flexibility of the fiberglass hull probably prevents such extreme sensitivity. If anyone would like a copy, PM me, I would like to get more sets of eyes on it in case of any errors.

I have been studying the actual tension (measured) vs. time and temperature on my boat for about 1 year now, but it's too early for conclusions. I found a LOT of creep initially, but now it has stopped creeping, making a study of temperature vs. tension much more possible.

[Tortuga's Lie]

Thanks for this thread, I find it very interesting.......learning something new here about synthetic rigging.

[GordMay]

Originally Posted by Popeye.Tom

I know of a small handful of materials with negative thermal expansion coefficients...

... I need to get the actual coefficient and calculate the tension changes for a cycle. Maybe not so bad. But if he tensioned the rig at 60F and it went that slack at 20F, that is a 40* delta! ...

Cheers,
Tom

Dyneema [UHMWPE] fiber has a [Negative*] coefficient of linear thermal expansion of
-12 x 10^-6 per Kelvin per [°C]
➥ https://pelicanrope.com/content/PDFs...eet-UHMWPE.pdf

* Unlike most materials, Dyneema contracts as it heats up, and expands as it cools.

“Dyneema and its Coefficient of Thermal Expansion” ~ by Herb Benavent

”... Dyneema has a [Negative] Coefficient of Thermal Expansion of -12 x 10^-6 m / K [0°C].
This means that for every change temperature equivalent to 1 Kelvin (also equivalent to 1 degree Celsius) a meter of Dyneema will change its length by 0.000012 m, or 12 μm.

A little more clearly, for every degree change in Celsius, Dyneema will expand or contract by 12μm for every meter of length of the line...”

Here ➥ https://www.riggingdoctor.com/life-a...rmal-expansion ..."[/quote]

Aluminum, has a coefficient of 23.1 x 10^-6 per 0°C
Stainless Steel has a coefficient of 16.5 x 10^-6. [Grades 304 & 316]

[JBP]

I believe I watched that video a long time ago and as I recall it wasn't that he couldn't adjust the tension, but he didn't want to. I've forgotten why, maybe it was going to warm up the next day?

But yeah, dyneema rigs have a lot of advantages but also some disadvantages. One of the disadvantages is you have to adjust it for large swings in temperature.

[jfranta]

Originally Posted by JBP

I believe I watched that video a long time ago and as I recall it wasn't that he couldn't adjust the tension, but he didn't want to. I've forgotten why, maybe it was going to warm up the next day?

But yeah, dyneema rigs have a lot of advantages but also some disadvantages. One of the disadvantages is you have to adjust it for large swings in temperature.

Guys, At Colligo Marine, we have rigged over 2500 boats now around the world with Dyneema Standing Rigging, Dynice Dux and our hardware. Mostly with turnbuckles, post processed the way we make it. Tension the rig in the coldest you will sail and you will not see an issue with over tensioning. If you rig in hot weather just know that you will need to re-tension the rig at some point if it gets colder. If you use lashings you will not get enough pretension on most boat rigs to even sail efficiently, gaff rigs on smaller boats are usually ok with lashings

No Disrespect, but the rigging doctor apparently got his degree in a landlocked country, lots of misinformation on his site about Dyneema for standing rigging. Do not underestimate the need for pretension in standing rigging. We would never put lashings on his boat. Turnbuckles are very good at what they do.

Last year we had a 50 foot adventure monohull boat with our rigging go from New England to ANTARTICA, can you say temperature swings? His biggest issue was the constant 50 knot winds and harmonics in the Dyneema, which most people will not have.

Transpac boats with our rigging have left cold San Franciso and arrived in Hawaii and never had to touch their rigging.

Check out syntheticstandingrigging.com for more information on what we have learned over 15 years of using Dyneema for standing rigging.

We have never had a creep issue in any of our boats as we design for creep. You just need to size the line correctly for the tension it will see and we have creep equations for that. Most of the time the elongation you see is constructional as the strands try to align themselves with the load path in the line, unless you size the line incorrectly, (too small) then you could get creep. We post process the line so we do not have this issue.

John Franta- Colligo Marine.

[jfranta]

Originally Posted by markxengineerin

Sean, I love what you do with your boats, but have to disagree with a couple things here. You "can" sail a boat with a slack rig, but by doing so, you're increasing the loads on everything else in the system, and not keeping the mast where it would be with a better rig, which will affect performance. You "can" sail a boat with loose string holding the mast up, but that doesn't make it a good idea for most people. The reason for tension in rigs is not only to avoid destroying the wire. There's a good explanation here (from the great book, Illustrated Sail & Rig Tuning by Ivar Dedekam, which another forum member recommended to me when I had questions on this topic)

When rigging material is switched from stainless to dyneema, tension should be set the same as originally designed for, to maintain the intended sailing performance.

I created this spreadsheet to study the effect of temperature on my synthetic rig / aluminum mast combo.

The results are shocking to me, and I think the flexibility of the fiberglass hull probably prevents such extreme sensitivity. If anyone would like a copy, PM me, I would like to get more sets of eyes on it in case of any errors.

I have been studying the actual tension (measured) vs. time and temperature on my boat for about 1 year now, but it's too early for conclusions. I found a LOT of creep initially, but now it has stopped creeping, making a study of temperature vs. tension much more possible.

I would luv to get a co[py of your spreadsheet so I can look at formulas. These numbers are way too high and not seen in real world usage. Can you forward to jfranta@colligomarine.com. Can you forward to jfranta@colligomarine.com?

[Lee Jerry]

Originally Posted by jfranta

I would luv to get a co[py of your spreadsheet so I can look at formulas. These numbers are way too high and not seen in real world usage. Can you forward to jfranta@colligomarine.com. Can you forward to jfranta@colligomarine.com?

Here's my take on why the numbers seem high to both of you and don't (seem to) reflect real life.

The reason is that the analysis assumes everything is in column and stays in column, but in reality the mast bends, and that isn't accounted for in the calculations. So instead of the shrouds stretching ~5 mm (and the associated increase in tension), the shrouds only stretch a couple mm (and the corresponding less increase in tension) and the mast bends some. The more initial prebend then the easier and more it will bend, but even an initially "straight" mast will bend some.