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Old 25-05-2023, 22:36   #1
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Dyneema Thermal Expansion - Enough to Break Things?

I am considering re-rigging with Dyneema, but have a question about thermal expansion properties of Dyneema.

How much of an issue is thermal expansion with Dyneema standing rigging? I sail in an area where we get large temperature variations during the winter. As a cold front approaches, temps often rise to the mid 70s, then drop overnight into the low 40s / upper 30s when the front passes. Over the subsequent 3 or 4 days, the temp rises back to the 70s. Sometimes we'll get get a week or two of 40s at night / 60s in day. Then back to the 3 - 4 day freeze/thaw cycle.

This is a typical temperature cycle in the 2 or 3 winter months. During this type of temperature change, will Dyneema expand enough during the cold periods to cause too much slack in the rigging to cause issues with the tuning of the mast?

Fall/Spring temps are fairly stable and from June to about November, the temps rarely go below 80 degrees (90s in day, 80s at night). If I re-rig with Dyneema, will I have to retune the rig twice a year (summer vs winder temp ranges) or more?

Is there a temperature range within which the cold-expansion is not noticeable. Is the expansion linear across a temperature range or does it expand more at colder temps (< 40 degrees)?

I found this factor for cold-stretch: For every change of one degree Kelvin, one meter of Dyneema expands 0.000012 meters.

If my temp ranges from 70 degrees to 40 degrees (294.3K to 277.6K), that is a temperature change of 22.2K
With an upper shroud of 15 meters long, that means it will expand almost 3/16" (~4mm)

(22.2 K temp change * 0.000012 meters)*15 meters = .00405 meters, or 4.05 mm or .1597 inches


Is this calculation correct? How does the line diameter factor into thermal expansion?

Does "heat set" dymeema follow this thermal expansion formula?

If the rigging is tuned for 40 degrees and each week the temp rises to 70 degrees, then falls back to 40 or below, will this cycling cause enough fatigue in the metal parts connected to the standing rigging to be an issue? The metal parts are the chain plates, toggles, turnbuckles, mast tangs, mast tang fasteners (#10 machine screws in aluminum mast as well as 1/2" through bolt through mast)?

Another way to look at this with the temp change over a 24 hour period. Regardless of the absolute temp or time of year, the typical temperature change from day to night is between 20 and 30 degrees (higher range in low humidity condition). Late summer, this range shrinks to 10 or 15 degrees (humidity is very high during August and September).

With a 30 degree change, a 50' shroud will expand/contract by 4.05mm (almost 3/16")
With a 20 degree change, a 50' shroud will expand/contract by 3.05mm (almost 1/8")

How fast does the cold-expansion occur. For example, in the summer, a squall line will pass through and drop the temp by 20 degrees over a 30 minute period while we get 25 or 45 knots. Winds will get light again and temp will rise 10 or 15 degrees for the rest of the day. Twenty degrees is about 1/8" elongation, but how long will it take to shrink that much? 15 minutes, 10 hours, days?

How much of a difference in sailing performance will 1/8" make to sail shape and/or rig stability?
I don't race, I used to. Now I just sail, but I don't like scallops or incorrectly trimmed sails.



Thanks
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Old 26-05-2023, 00:37   #2
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Re: Dyneema Thermal Expansion - Enough to Break Things?

I believe you will have trouble. Iirc you can eliminate the problem with a carbon mast

https://www.riggingdoctor.com/life-a...inters-stretch
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Old 26-05-2023, 05:46   #3
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Re: Dyneema Thermal Expansion - Enough to Break Things?

I discovered a mistake in my calculations; The temperature change from 70 to 40 is not 22.2, but only 16.67. This makes the elongation only 3mm in 15 meters instead of 4mm.

I also realized that the Kelvin and Celcius are the same, excpet for a 273 difference, so this makes for fewer potential coversion errors and I can just use Celcius.

Recalculating:
Winter frontal scenario: 20C --> 4C = 16 degree difference, so 2.92 mm
Typical, low humidity 24 hour change: 29C to 17C = 12 degree difference, so 2.3 mm
Typical high humidity 24 hour change: 33C to 25C = 8 degree difference, so 1.5 mm

That still seems like a lot. Today, we are in the "low humidity" scenario and it's great weather for sailing.
The boats not ready because the mast is on saw horses, but if I were to sail today, would that 2.3mm elongation occur overnight?
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Old 26-05-2023, 05:50   #4
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Re: Dyneema Thermal Expansion - Enough to Break Things?

Quote:
Originally Posted by scherzoja View Post
I discovered a mistake in my calculations; The temperature change from 70 to 40 is not 22.2, but only 16.67. This makes the elongation only 3mm in 15 meters instead of 4mm.

I also realized that the Kelvin and Celcius are the same, excpet for a 273 difference, so this makes for fewer potential coversion errors and I can just use Celcius.

Recalculating:
Winter frontal scenario: 20C --> 4C = 16 degree difference, so 2.92 mm
Typical, low humidity 24 hour change: 29C to 17C = 12 degree difference, so 2.3 mm
Typical high humidity 24 hour change: 33C to 25C = 8 degree difference, so 1.5 mm

That still seems like a lot. Today, we are in the "low humidity" scenario and it's great weather for sailing.
The boats not ready because the mast is on saw horses, but if I were to sail today, would that 2.3mm elongation occur overnight?
No, it is much worse because the aluminum mast expansion is the other way around.
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Old 26-05-2023, 06:47   #5
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Re: Dyneema Thermal Expansion - Enough to Break Things?

Calculations aside, thermal expansion/contraction is a definite factor with heat set dyneema, especially if you are wanting a consistent tune on your rig. You will be adjusting often. From our often foggy mornings to warm ish afternoons here on the south coast of Oregon there can be a very noticeable change in rig tension.
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Old 26-05-2023, 06:58   #6
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Re: Dyneema Thermal Expansion - Enough to Break Things?

It's interesting fallible our minds are when in the shadow of ignorance and how perceptions change with the introduction of new data. The more I look into this the more I realize that my initial perceptions might have been wrong and that this issue has always been with me, but I never saw it (that could also be a new perception based on continued ignorance).

I looked up the Coefficients of thermal expansion for Aluminum, 316 SS, & 304 SS and compared with that of Dyneema.
These values are all for change / m / temp change (K or C)

6061 Aluminum: 0.000023
316 SS: 0.000016
304SS: 0.0000173
Dyneema: -0.000012

Sources:
https://www.engineeringtoolbox.com/t...als-d_859.html
http://dynamicarope.com/wp-content/u...eema-Fibre.pdf
https://www.riggingdoctor.com/life-a...2012%20%CE%BCm.


My initial (and apparently wrong) perception was that Dyneema elongated more than SS standing rigging and inversely to temperature.
My new understanding, based on these coefficients, is that 316 and Dyneema elongate about the same, but in opposite directions and that Aluminum elongates about twice as much as Dyneema. Because SS and AL elongate in the same direction, the only issue is the difference, which is .000007 m/C and that is a small difference over a 20 or 30 degree temp change. Not noticeable over stable daily temp ranges.

It is not the elongation of Dyneema that is the problem, but rather the fact that it is inverse to temperature and, with an aluminum mast, the change in lengths of these two materials (Dyneema and Aluminum) in opposite directions is what causes the issue.


Jedi, that explains (I think) your comment about carbon fiber mast (.0000015 m / K).

Did I finally get it and what am I still missing?

With this information, my bottom line of what I am trying to answer is how detrimental this change in length is to the stability/safety of the mast vs just sailing performance? If rigging is too tight, something is going to break.
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Old 26-05-2023, 07:46   #7
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Re: Dyneema Thermal Expansion - Enough to Break Things?

Quote:
Originally Posted by scherzoja View Post
It's interesting fallible our minds are when in the shadow of ignorance and how perceptions change with the introduction of new data. The more I look into this the more I realize that my initial perceptions might have been wrong and that this issue has always been with me, but I never saw it (that could also be a new perception based on continued ignorance).

I looked up the Coefficients of thermal expansion for Aluminum, 316 SS, & 304 SS and compared with that of Dyneema.
These values are all for change / m / temp change (K or C)

6061 Aluminum: 0.000023
316 SS: 0.000016
304SS: 0.0000173
Dyneema: -0.000012

Sources:
https://www.engineeringtoolbox.com/t...als-d_859.html
http://dynamicarope.com/wp-content/u...eema-Fibre.pdf
https://www.riggingdoctor.com/life-a...2012%20%CE%BCm.


My initial (and apparently wrong) perception was that Dyneema elongated more than SS standing rigging and inversely to temperature.
My new understanding, based on these coefficients, is that 316 and Dyneema elongate about the same, but in opposite directions and that Aluminum elongates about twice as much as Dyneema. Because SS and AL elongate in the same direction, the only issue is the difference, which is .000007 m/C and that is a small difference over a 20 or 30 degree temp change. Not noticeable over stable daily temp ranges.

It is not the elongation of Dyneema that is the problem, but rather the fact that it is inverse to temperature and, with an aluminum mast, the change in lengths of these two materials (Dyneema and Aluminum) in opposite directions is what causes the issue.


Jedi, that explains (I think) your comment about carbon fiber mast (.0000015 m / K).

Did I finally get it and what am I still missing?

With this information, my bottom line of what I am trying to answer is how detrimental this change in length is to the stability/safety of the mast vs just sailing performance? If rigging is too tight, something is going to break.
Carbon fiber, like Dyneema, has a negative thermal expansion so it is a good match with Dyneema standing rigging.

For the temperature range you describe, you simply cant sail in the cold when you have an aluminum mast and Dyneema rigging. If you would make it tighter, then it may rip your chainplates out when it gets warmer.

The article I linked to above describes the whole thing plus a possible workaround with an additional lashing for cold weather sailing.
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Old 26-05-2023, 07:50   #8
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Re: Dyneema Thermal Expansion - Enough to Break Things?

I don't think anything is going to break by being too tight, I mean, it would have to reach an indecent level of tension to break something.

More worrisome is that it will loosen with temperature changes, a slack rigging suffers more than a tight one , turnbuckle , summer-winter marks, or if necessary tune the rig with temperature changes.
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Old 26-05-2023, 10:14   #9
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Re: Dyneema Thermal Expansion - Enough to Break Things?

Ironic that dyneemas UV resistance is at the cost of its static integrity. I would lean towards an aramid like my favorite “technora” for its strength and static load carry capability but for its UV degradation that most often only presents in catastrophic failure. I would imagine that expansion and contraction plays a part in fatigue, and to that point does the dyneema experience fatigue at the same rate as SS rod or cable?
I wonder how much expansion and contraction (fatigue) occurs in laminate sails, I know Dacron is stiffer (more brittle less stress resistant) in colder temperatures but the sail makers don’t like to talk up that point.

Very interesting points on these new engineered components, thank you for raising them
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Old 26-05-2023, 10:26   #10
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Re: Dyneema Thermal Expansion - Enough to Break Things?

Quote:
Originally Posted by neilpride View Post
I don't think anything is going to break by being too tight, I mean, it would have to reach an indecent level of tension to break something.

More worrisome is that it will loosen with temperature changes, a slack rigging suffers more than a tight one , turnbuckle , summer-winter marks, or if necessary tune the rig with temperature changes.
The problem is when its cold and you would tension the Dyneema more. With the aluminum mast shorter and the Dyneema longer, this is a substantial difference, which then has the potential to rip out chainplates when it warms up again where the mast will grow longer while the shrouds crimp.

I have seen plenty of chainplates being pulled up from deck where the bolts just cut through the bulkheads below with boltholes becomes slots of 2-3 inches before it gets noticed. And this is with mast and rigging that have equal thermal expansion!
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Old 26-05-2023, 13:00   #11
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Re: Dyneema Thermal Expansion - Enough to Break Things?

Jedi,

That's what I'm concerned about. Some forces are quite profound; water freezing in a rigid pipe, the capacity of warm air to suck water out of everything around it. I'd like to understand (and calculate) what is involved to see how big of damage risk exists in my specific case and if my goal of eliminating SS crevice corrosion is achievable without introducing another potentially disastrous factors.

Does anyone know if a formula exists that I can use to calculate the force exerted when dyneema shrinks? If we know the starting tension (1000 lbs) and dyneema shrinks 1/4" or 3/8", how many additional pounds are exerted on the end fittings? I suppose the same formula that calculates force when a turnbuckle is screwed down 1/4". I don't know that one either.

Thanks again y'all.
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Old 26-05-2023, 15:01   #12
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Re: Dyneema Thermal Expansion - Enough to Break Things?

Quote:
Originally Posted by scherzoja View Post
Jedi,

That's what I'm concerned about. Some forces are quite profound; water freezing in a rigid pipe, the capacity of warm air to suck water out of everything around it. I'd like to understand (and calculate) what is involved to see how big of damage risk exists in my specific case and if my goal of eliminating SS crevice corrosion is achievable without introducing another potentially disastrous factors.

Does anyone know if a formula exists that I can use to calculate the force exerted when dyneema shrinks? If we know the starting tension (1000 lbs) and dyneema shrinks 1/4" or 3/8", how many additional pounds are exerted on the end fittings? I suppose the same formula that calculates force when a turnbuckle is screwed down 1/4". I don't know that one either.

Thanks again y'all.
I believe the force is infinite, meaning that either the mast, the shroud or the chain plate will fail.
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Old 26-05-2023, 19:30   #13
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Re: Dyneema Thermal Expansion - Enough to Break Things?

You should talk to John at Colligo, he has done hundreds of boats and can answer your question with actual knowledge and cases. I've had dux dyneema for 13 years and love it
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Old 27-05-2023, 08:09   #14
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Re: Dyneema Thermal Expansion - Enough to Break Things?

Jharding,

I did speak with John yesterday and he conceded that the expansion is an issue with wide temp swings and his advice is, for each season, tune the rigging on the cold days, then when the temp warms up, the rig will tighten. Following this logic, I would tune in the spring around 75 or 80 degrees F, then retune in the fall, when temps stay below about 70 degrees. His answer to the amount of force applied when the line shrinks was that the force is not significant, in the area of an additional 10 pounds.

I'm still looking for the formula that shows how much additional force is exerted when the shroud is shortened by 1/4", which is John's estimate of the total length change of a 50' shroud on a 50' mast with 25 degree F temp change. Furthermore, his recommendation is to use turnbuckles, not lashings for my size boat (~37 feet).


I did review the pages and videos from Rigging Doctor, but those didn't answer the fundamental question of how much force is applied when the shroud is shortened. This answer might lie with SS rigging because I think that there should be not much of a difference between Dykneema shrinking 1/4" and a turnbuckle shortening a SS wire by 1/4".

I still have more digging to do to ascertain what force is really applied when the rigging shrinks and how that will affect the connection points.

Thanks again for y'all's help.
Have a good weekend.
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Old 27-05-2023, 08:20   #15
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Re: Dyneema Thermal Expansion - Enough to Break Things?

Quote:
Originally Posted by scherzoja View Post
Jharding,

I did speak with John yesterday and he conceded that the expansion is an issue with wide temp swings and his advice is, for each season, tune the rigging on the cold days, then when the temp warms up, the rig will tighten. Following this logic, I would tune in the spring around 75 or 80 degrees F, then retune in the fall, when temps stay below about 70 degrees. His answer to the amount of force applied when the line shrinks was that the force is not significant, in the area of an additional 10 pounds.

I'm still looking for the formula that shows how much additional force is exerted when the shroud is shortened by 1/4", which is John's estimate of the total length change of a 50' shroud on a 50' mast with 25 degree F temp change. Furthermore, his recommendation is to use turnbuckles, not lashings for my size boat (~37 feet).


I did review the pages and videos from Rigging Doctor, but those didn't answer the fundamental question of how much force is applied when the shroud is shortened. This answer might lie with SS rigging because I think that there should be not much of a difference between Dykneema shrinking 1/4" and a turnbuckle shortening a SS wire by 1/4".

I still have more digging to do to ascertain what force is really applied when the rigging shrinks and how that will affect the connection points.

Thanks again for y'all's help.
Have a good weekend.
When you consider aluminum not compressible and Dyneema not stretchable then the amount of force is infinite and something needs to break or bend. It is like trying to ram the square block through the round hole, it simply doesn’t fit.

When tightening the capshrouds more with aft swept spreaders, you bend the mast more and this is a possible way out for that type of rig.

In reality the aluminum will compress a bit and the Dyneema will stretch a bit more before breaking, but you want to keep that as a safety margin.

You can simply test this. Take a scale, a length of Dyneema, a strong enough board and a bottle jack. Measure length and pressure while changing length with the jack.

Edit: also, you talk about force when the Dyneema shrinks, but you omit the mast that expands. It expands more than the Dyneema shrinks and added up is much more than just the Dyneema.
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