Weight Savings of Synthetic over Wire on the Warn M12000

[pugslyyy]

Thanks for the feedback! Have you ever experienced or heard of any issues with synthetic lines getting worn out or degrading from exposure to road salt, or prolonged exposure to moisture (think rainfall or melting snow)? Are there any maintenance requirements to dry out the synthetic line periodically?

The origin of synthetic lines was the commercial fishing industry. If it was moisture or salt sensitive we would have heard about it.

 

[Ducky's Dad]

When I looked into synthetic a few years ago, the biggest downside I could find was the degradation from sun , UV, and ozone exposure, plus the fact that it loses strength as the temperature increases. Since most of my offroad driving is in the deserts of So Cal and AZ, I decided to stick with steel until I have to replace my cable, which may be never.

 

[I Leak Oil]

Both will last a long time if taken care of. Yes, cable typically will need some care if used here in the Northeast as well.
Instead of taking lots of opinions on the environments affects on rope from discussions on the web, try going to the material manufacturers and getting info there. As pointed out, rope is used in the fishing/boating industry so the notion that salt or UV significantly degrades them is web lore, not fact. You will also find temperature related affects as well.

Towing/recovery businesses use cable because it makes more financial sense (cable is less expensive) and is able to handle being dragged over rock, trees, sharp guard rails and sharp edges of rolled vehicles better. Not every tow job is a simple broken down vehicle on the side of the road. If you can relate to these condition while doing recreational self recovery then cable may be a better choice.

As far as the weight goes, look at it this way. It may only be an additional 35 lbs, but when you add up ALL the additional "only" lbs. you put on the vehicle it does have an affect.

 

[Ducky's Dad]

the notion that salt or UV significantly degrades them is web lore, not fact. You will also find temperature related affects as well.

Not web lore. I found the industry lab reports and read a bunch of them before I decided to stay with cable for now.

 

[pugslyyy]

Not web lore. I found the industry lab reports and read a bunch of them before I decided to stay with cable for now.

I'd be interested in seeing the citations for those. I have never seen anything that says that synthetic rope is sensitive to salt, and while UV sensitivity was certainly an issue in the past I thought that the UV stabilizers that they were using were pretty darn effective now.

 

[Ducky's Dad]

I have never been concerned about salt degradation because we barely get rain here, let alone snow. And they never salt the roads here. My issue was/is mostly the UV degradation and the empirical reduction in tensile strength of the synthetic as operating temps increase. Not just a theoretical issue for me because of where I take the truck. In AZ last August we measured 128F ambient in the middle of the afternoon, and that is before you take into consideration the heat coming off the engine and radiator, plus the heat generated by the winch pull. Would I break a good quality synthetic cable? Probably not, but my steel cable is in good shape and there seems to be no compelling reason for me to switch to synthetic at this point. I'll try to find some of the stuff I located on synthetic and sun/heat.

 

[Ducky's Dad]

Found this from one of my old posts on another forum. Samson link no longer works, though. Still looking.

Samson Rope has a Tech Bulletin on their website about Amsteel Blue in cold environments. According to them, Amsteel Blue gets stronger as temperatures drop. The converse would be that its strength decreases as temps rise. They reference a couple of bulletins on high temp and UV radiation as it relates to Amsteel Blue and its component fibers, but those bulletins don't seem to be posted on the website. Coincidence? I dunno. Here's the cold weather bulletin:

http://www.samsonrope.com/site_files...Can_You_Go.pdf

There is a graph under the Strength paragraph that shows tensile strength falling off rapidly as temps rise. At 150C (302F), the stuff has lost about 50% of its strength (informal extrapolation of the graph line). At 100C (212F), it has lost about 20+% of its tensile strength. That 20% reduction might be offset by the additional strength of using 1/2" syn in place of our 7/16" steel, but you won't have as many feet spooled on your winch, so you'll be forced to carry an extension on the truck. At $400 for a 100' length of the 1/2" syn, that gets expensive, fast. Amsteel sells bulk rope on 600' spools, but it's north of $1500 for a spool.

 

[Ducky's Dad]

Here is more:

From the tech paper on syn rope in hot environments:

Syn is a size-for-size replacement for wire rope, but weighs 1/7 of equivalent wire rope.

Syn reaches temperature equilibrium in 30 minutes or less. Meaning that if the air temp around your winch rises from 100F to 200F, your syn rope is at 200F internal temp within 30 minutes. Time-to-temp depends on rope diameter and single strand vs multi-strand. Smaller diameters reach equilibrium faster than larger diameters.

At 120F ambient, the rope will stabilize after about 20 hours and will lose 8% of its tensile strength. Last September 3 in Yuma, the lunch time ambient was 118F, in the shade. Hotter in the sun, hotter around the winch with the engine running, hotter still if you are doing a pull. The loss of tensile strength accelerates rapidly as ambient temps increase. AT 170F for 20 hours, the rope has lost about 25% of its strength, but after 40 hours at that temp, it has lost about 40% of its strength, and the loss of strength continues at that temp until it reaches about a 45% reduction at about 75 hours. At 212F, syn has lost about 75% of its tensile strength after 30 hours.

With conducted heat (as in heat conducted from the winch drum) the internal temp if the syn rope will stabilize after about 100 minutes, but will never reach the temp of the surface that it is in contact with. As an example, a 1-5/8" rope on a 70C hotplate stabilizes at about 40C after 100 minutes. Rope diameter is a factor, so expect that 7/16" syn will reach internal temp much faster, and heat is the rope's enemy. Sheathing or covering does make some difference, so a protective cover on the first wind of the syn rope seems to be a good idea.

As I understand the concept of Creep Lifetime (continual time at temp and load), the syn ropes will exhibit some initial fiber elongation (stretch), then move to some permanent fiber elongation, then move to rapid elongation and fiber rupture, but the progression of this sequence depends on a combination of both temp and load. My layman's conclusion is that our ropes are under load for such relatively brief periods of time during a pull, that creep elongation is not much of a factor. Could also be that I just don't fully understand creep lifetime, which is the time/temp/load combination that leads to fiber rupture and rope breakage.

Here is the link to this paper. I'm still looking for material on UV resistance, but the authors of this paper claim good resistance to UV, but without any supporting data.

http://www.samsonrope.com/site_files...t_Climates.pdf

That Samson link also appears to be dead. Don't know why. I first found it in February of 2011.

 

[Ducky's Dad]

More on UV degradation:

Here is a graph presenting Strength Retention of syn ropes after prolonged exposure to UV. Look at the red line for Dyneema (the trade name for the fiber used in Amsteel Blue). After two years exposure to UV, the rope is down to about 63% of its initial strength. That, to me, is a HUGE decrease in strength. You may think it's not a problem because most of your rope is not exposed, but the rope is only as strong as its weakest section, so the first foot or two that is hanging out of the fairlead with the rope hook attached to your tow hook will quickly become the weak link, unless it is sheathed.

This graph came from page 10 of this paper:

http://www.samsonrope.com/site_files...tic_Ropest.pdf

Page 8 shows a graph of strength-vs-diameter for Dyneema (Amsteel Blue)compared to wire rope, but they do not specify the wire rope used for the comparison. I have not found the data table to support that graph. Everything in this paper is based upon tow ropes used in the shipping industry (mostly tug boats), and it covers a lot of issues related to the use of syn rope. There can be significant strength reduction caused by compression on the drum, twisting of the rope, cyclic fatigue, repetitive shock loading, etc. About the only factor we don't need to worry about is shark bites.
Attached Thumbnails
Click image for larger version

Name: Dyneema Yarn UV Resistance.jpg
Views: 2
Size: 321.1 KB
ID: 317510

Another dead link. I'll try to post the graph that was embedded.

Here is the graph from the above link:

 

[I Leak Oil]

http://www.marlowropes.com/dyneema.html
This is just one of many sites that come up when you search for dyneema properties. There is a ton of info out there on it. Not sure where Sampson generates it's data from but seems most everyone else says UV is a negligable factor. I don't think fisherman or tug operators want to replace VERY expensive large diameter rope every year...
Another thing to think about is since equivalent diameter rope is much stronger, it can lose X % of strengh due to temperature and still be as strong or still stronger than wire. I think the concerns about rope used in self recovery is WAY overblown. Same way the dangers of wire rope are.

 

[Ducky's Dad]

I Leak Oil, you are in Massachusetts. Not the same environment as southern Arizona. If you read up on marine synthetic rope use in Africa, you might change your opinion for those conditions.

From the Marlow link:

On a weight for weight basis, Dyneema® is 15 times stronger than steel wire

Marlow is a yachting site and weight is a bigger deal to a racing yacht than it is to us. And we are not talking about weight-to-weight comparisons for winching our trucks. What counts is how much length vs weight capacity you have on the drum. Warn recommends size-for-size replacement, i.e. if you are using 7/16" steel replace with 7/16" synthetic. I am quite comfortable with my choice for my use in my conditions.

 

[Dalko43]

Some very interesting points being brought up. What kind of "care" or maintenance does one need to factor in when talking about either cable or synthetic?

Both will last a long time if taken care of. Yes, cable typically will need some care if used here in the Northeast as well.
Instead of taking lots of opinions on the environments affects on rope from discussions on the web, try going to the material manufacturers and getting info there. As pointed out, rope is used in the fishing/boating industry so the notion that salt or UV significantly degrades them is web lore, not fact. You will also find temperature related affects as well.

Towing/recovery businesses use cable because it makes more financial sense (cable is less expensive) and is able to handle being dragged over rock, trees, sharp guard rails and sharp edges of rolled vehicles better. Not every tow job is a simple broken down vehicle on the side of the road. If you can relate to these condition while doing recreational self recovery then cable may be a better choice.

As far as the weight goes, look at it this way. It may only be an additional 35 lbs, but when you add up ALL the additional "only" lbs. you put on the vehicle it does have an affect.

I do plan on talking to some winch manufacturers to get their opinions...I don't see any problems with asking for feedback from winch owners to compliment my own research, though I do appreciate your suggestion.

Your explanation of why tow companies use cable does make sense. And I agree that the weight savings from using synthetic over cable could add up if I attempt to mitigate or keep weight to a minimum in other areas.

My main motive in asking this type of question is in fact to save weight. My 5th gen 4runner is certainly capable of taking some additional weight, but with an independent front suspension and an engine that is by no means sprightly, I do want to keep my added weight from mods as low as possible. Im thinking of getting a relatively light steel bumper (110lbs) with a synthetic 8000lb winch, I should be able to keep the added weight to the front end below 170lbs.

 

[Ducky's Dad]

Dalko43, if you are in upstate NY, heat is never likely to be an issue for your synthetic winch line. Cold temps actually seem to enhance the strength of synthetic line, supported by the research. UV is easily dealt with by ordering a sheath for the first wrap of your line.

 

[I Leak Oil]

I Leak Oil, you are in Massachusetts. Not the same environment as southern Arizona. If you read up on marine synthetic rope use in Africa, you might change your opinion for those conditions.

From the Marlow link:

Marlow is a yachting site and weight is a bigger deal to a racing yacht than it is to us. And we are not talking about weight-to-weight comparisons for winching our trucks. What counts is how much length vs weight capacity you have on the drum. Warn recommends size-for-size replacement, i.e. if you are using 7/16" steel replace with 7/16" synthetic. I am quite comfortable with my choice for my use in my conditions.

Size to size dyneema is substantially stronger. Weight to weight no comparison. I would never debate the comfort of your choice. There is nothing wrong with cable.

 

[Stumpalump]

On my heavy van I switched back to steel. You don't notice the 25lbs on a heavy rig. On the lite jeep I'll stick with synthetic. I don't like it but it's lite. It breaks, it cuts, it gets weak in the sun and heaven forbid it touches an exhaust pipe or it turns to liquid. The other problem is loading it too fast. The stretch and strain causes heat making it break easy. You need to load the line very slow to keep internal friction temps down. Good luck with that as you slide down the hill. Basically synthetic is too fragile for an off road environment but it's light and safer when it breaks. Plan on it breaking, keep it away from rocks, dirt, metal, heat and sun. Check it for nicks and replace it every year or two like the sail boat racer do if you actually use it. It's nice to carry and touch but it sucks.