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Old 05-16-2013, 10:29 AM   #1
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polyester vs nylon anchor line

Talking about 3 strand anchor line here...

Back in my rock climbing days the rope came with a fall rating, meaning that after the rated number of hard falls the rope was retired. This is because after being subjected to severe loading, nylon begins to lose strength.

In an anchoring context, how would one know when to retire a nylon anchor line? Stretch is one of the selling points of nylon, but it also contributes to it's losing strength over time...

Wouldn't polyester anchor line be better as it is more resistant to chafing, doesn't lose strength when it gets wet, and doesn't lose strength from shock loading to the same degree as nylon? (You'd have to account for the lack of elasticity with an anchor snubber.)

What do you think?
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Old 05-16-2013, 03:29 PM   #2
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Polyester, at least the kind I'm familiar with (I use it for winch line on the capstan winch on my Land Rover, and we also use it as a stern-tie line on the GB) is very susceptible to UV deterioration. Not that an anchor line lives in the light all that much, but nevertheless it's a consideration.

And there is real value in having the entire anchor rode (except for the chain at the end) as a shock absorber when the wind kicks up. A snubber with all-chain rode is just a way to provide a degree of shock absorbing which is better than nothing but is not nearly as effective as having a whole rode made of a line with good elasticity.

Also, while there are knots that enable this, fastening a snubber line to a rope rode is not as secure (I don't think) as putting a hook on a chain. So I don't know how well a snubber tied to a line would stay put in a really strong pull.

While this is an easy but unsubstantial answer, I expect that if polyester represented a superior or at least equal performer in an anchor rode than nylon you would see a lot of people using it. It is certainly cheaper. But nobody does, at least nobody with boats like the ones most of us have, or sailboats.
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Old 05-16-2013, 06:05 PM   #3
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We're on our third chunk of 1/2" nylon for this boat - 26 feet, 11,000 lb, with a 10kg Rocna anchor, 46 feet of 1/4" HT chain, and a horizontal-axis windlass. The first two lasted 7 summers each, until they were visibly losing it somewhat from abrasion and general wear and tear. I'd guess we anchored in BC or SE Alaska 300+ times with each.

With 3-strand I'd say frequent visual inspection works pretty well. We also wash vigorously with Tide and rinse thoroughly, to get as much grit out as possible, then reverse and re-splice to the chain, at the end of every summer.
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Old 05-16-2013, 09:15 PM   #4
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Generally, polyester has very little stretch as compared to nylon which has quite a bit. The nylon stretch acts as a shock absorber which reduces stress on your fittings and your comfort. For this reason, polyester is not recommended for anchor or dock lines.
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Old 05-16-2013, 11:37 PM   #5
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Murray,

I think you are spot on.

3 strand nylon sucks. It stretches and unwinds, and will twist into a big knot. It's hard on your hands too. It loses strength when wet, and some can get hard in the sun. If you have a really long rode (which you will) it has too much stretch as you can even bounce around in wind gusts like a bungee cord and chafe on the anchor roller when it does. I have some MIT study kicking around showing that rode failure during storms is due to heat generated from the stretching as much as it is from chafe. But hey, 3 strand nylon is cheap and it's traditional, so it'll be around for a while. Well, maybe one more generation of boaters

A multiplait rode if preferable (even if it is nylon).

Polyester would make a great anchor rode, if it is a multiplait. It is more abrasion resistant. It is not as strong, but doesn't lose strength when wet. Just because we can't get it easily in NA doesn't it make it less better. Polyester is expensive.

Check out Liros Octoplait.
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Old 05-17-2013, 01:19 AM   #6
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Quote:
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Check out Liros Octoplait.
This Yale 8 strand brait is what I was looking for initially...

Nylon Brait / Eight - Strand Plaited Nylon Rope | Yale Cordage

...but the shopping isn't so good where I live. All that's available is 3 strand polyester and 3 strand nylon (both of which I felt confident in being able to splice to chain) and nylon double braid (which I had no confidence in splicing to chain at all).

Ended up getting a great deal on some 3 strand nylon. That will do for a couple years while I try and talk myself into an all chain rode and a fancy new windlass

Thanks for the tips.
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Old 05-17-2013, 01:45 AM   #7
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I use whole chain rode, and in view of some of the issues raised, glad I can and do, but to answer one of the questions re polyester. If I think back to my yachting days when I did have a mixed rode, from memory one other dissadvantage to polyester was it floats, whereas nylon does not. ( I think - have not had time to gargle this), and I remember folk felt a floating anchor line was too likely to get into places it shouldn't, if you get my drift..?
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Old 05-17-2013, 02:21 AM   #8
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An all-chain rode with a nylon snubber is my preference. But for smaller, lighter boats a rode consisting of about the boat's length of chain and the remainder nylon braid is advantageous.
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Old 05-17-2013, 06:36 AM   #9
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Polly usually floats , so when someone motors or sails in front of your boat chances are chop chop on your rode .

Nylon stretches (if its not to large) and that is WHY it is used as anchor rode, the stretch keeps the shock loads on the anchor far lower than any line or cable or chain that does not stretch.
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Old 05-17-2013, 07:41 AM   #10
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Polypropylene floats, polyester sinks.
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Old 05-17-2013, 08:53 AM   #11
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Some previous posters noted that nylon "looses strength when wet." Personally I doubt that, but would be interested to learn if it is true. Would those who have mentioned this (Northern Spy, MurryM) be kind enough to quote their source of information? I would like to research it. Thanks.
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Old 05-17-2013, 09:39 AM   #12
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Quote:
Originally Posted by Captain K View Post
Some previous posters noted that nylon "looses strength when wet." Personally I doubt that, but would be interested to learn if it is true. Would those who have mentioned this (Northern Spy, MurryM) be kind enough to quote their source of information? I would like to research it. Thanks.
This is from the abstract for a paper presented to a Civil Engineering conference;

Fiber Ropes For Ocean Engineering in the 21st Century | TTI Papers

"Nylon, also known by its chemical name polyamide, has been widely used in marine mooring and towing lines since the 1950s. It has the lowest stiffness mod ulus, and thus it is favored where high extension is very important. It is the strongest of the common fibers when dry. However, wet nylon fiber loses about 10% of its strength, and wet nylon ropes can lose up to 20% of their strength. Wet nylon ropes also suffer strength loss due to creep and internal abrasion during tension cyclic loading.(Flory, 1982) The resulting short service life of large nylon ropes generally makes them unsuitable for permanent deep water moorings.

Polyester ropes are very durable in cyclic tensile fatigue loading.(Parsey, 1982, 1985) Very strong polyester rope with relatively high modulus can be made with the newer high-quality polyester fibers now available. They can be as strong as nylon when dry. Polyester ropes do not lose strength when wet and are generally stronger than nylon in wet condition. Thus polyester ropes are now supplanting nylon in many critical conventional marine applications and are good candidates for deep water mooring systems."


Me-thinks nylon is so widely used today because it was the first synthetic out of the gate and has become the norm, not because it is necessarily the best product for the job. We'll use nylon for now, but I'll trust it a little less after every storm...
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Old 05-17-2013, 09:58 AM   #13
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Murray,
I use the Brait. It's a tad over sized for our boat (5/8) and a bit expensive. I think it was $1.60 ft 8 years ago. I don't like anchor line inside the boat .... it stinks ... so I put it in a box on the foredeck. Three strand wouldn't even come close to fitting in the box and the box is already visually too big. I've intended on getting a classier looking box but haven't. The 325' of Brait comes out and goes back in the box w/o any troubles whatsoever. I've got it home w me now. It gets rinsed w fresh water but I've never even thought of washing it w soap. It's made as an anchor line and I don't know any downside except it's more money.
Sorry to post this picture again but it does show the Brait.
This is funny. I don't know how I did it but the 1st picture went away when I posted the 2nd ... the one you see now is a cropped version of the original. You can see the Brait fairly well and how it lays in the box. When I put the line in the box I leave the end out and attached to the port mooring cleat when I'm ready to deploy the rode.
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Old 05-17-2013, 09:59 AM   #14
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Thank you MurryM. You have opened my eyes. I read the paper from start to finish and learned not only was I wrong about nylon loosing strength when wet, but my conceptions about "poly" line were also mistaken. Notably, I learned there is a significant difference in polyester and polypropylene line: Polyester does not loose strength in water, it is not degraded by UV, and it does not float. Polypropylene line is degraded by UV, is subject to degradation caused by excessive heating when under cyclic load, and, because it is lighter than water, it floats. My conclusion from the paper you kindly referenced is that polyester is the preferred fiber above both nylon and polypropylene for mooring. I wonder whether many of our colleagues, or for that matter, those who sell line in marine stores, understand the rather significant difference between polyester and polypropylene fibers?
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Old 05-17-2013, 12:13 PM   #15
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Thank you MurryM. You have opened my eyes. I read the paper from start to finish and learned not only was I wrong about nylon loosing strength when wet, but my conceptions about "poly" line were also mistaken.
Me too!
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Old 05-17-2013, 01:26 PM   #16
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Many folks with too heavy line or chain use light (frequently 3/8) shock absorbing line about 20 ft long.

Has ANYONE EVER had one finally come apart from fatigue?.

Chafe if not installed properly , but fatigue?
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Old 05-17-2013, 10:36 PM   #17
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MIT mooring study.
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Old 10-25-2015, 06:45 PM   #18
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Bump!

Link gone, but found again;

https://pdos.csail.mit.edu/~decouto/...s/seagrant.pdf

*It bears repeating that polyester is nothing like polypropylene!
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Old 10-25-2015, 07:49 PM   #19
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By MurrayM
"Back in my rock climbing days the rope came with a fall rating, meaning that after the rated number of hard falls the rope was retired. This is because after being subjected to severe loading, nylon begins to lose strength."

My rock climbing "fall rating" would be ONE!
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Old 10-26-2015, 06:47 AM   #20
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A lot going on here ? Makes me reconsider my system.

We have 100 metres ( 328 feet ) of 13 mm short link chain spliced to 50 metres of 20 mm nylon on the main. On the other side of the locker and other gypsy we have 100 metres of 13 mm short link as a back up or if we need to deploy a 2 nd anchor .

In our case the nylon would only be deployed in an extreme weather condition or if the anchorage was in extremely deep water say 100 feet , so I think I will stick with it , as it spends all its time in the locker. But I have to say you learn and are exposed to a lot of different information on this forum, which is great and gets you thinking about what you have in place.

Keep it comin I say.

Cheers Chris D Liberty
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