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Old 30-01-2011, 10:58   #1
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Nylon vs Polyester

does anyone know why nylon is preffered over polyester when it comes to a anchor rode. it would be used after the initial 175' of 3/8" G40 chain the polyester is stronger than the nylon 3/4" mega braid nylon only has a breaking strenght of 15,000 where as the chain is 16200 so it would make nylon the weak point. 3/4" polyester 12 strand has a breaking strenght of 22,700. thoughts?
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Old 30-01-2011, 11:03   #2
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My understanding is that nylon is more UV resistant, abrasion resistant, and most importantly, has more stretch.

If you need more strength from the nylon line, you just go up a size.
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Old 30-01-2011, 11:05   #3
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the windlass cant handle any rope larger than 3/4"
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Old 30-01-2011, 11:08   #4
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I think you'll find that the anchor will pull out of the bottom long before you reach the breaking strength of most sized lines.

If you really need more strength than that (what size boat do you have?) then you probably need a bigger windlass
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Old 30-01-2011, 11:12   #5
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it is a 49' cat fully loaded displacment of 18,000lbs.
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Old 30-01-2011, 11:18   #6
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I suppose you could use poly line and just use a nylon snubber to give it some stretch, the same way you would with an all chain rode. From what I understand it's the stretchyness that is most important, which is the main reason why nylon is preferred.

But, I think the weakest link is typically the anchor's holding power.

I'm sure somebody else will come up with a more scientific answer soon enough
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Old 30-01-2011, 12:38   #7
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I believe its the stretch factor nylon offers. Nylon is susceptible the sun's rays more so than polyester. Polyester is the same material used for dodgers and so called canvas. Polyester thread is recommended to stitch those fabrics to avoid deterioration caused by exposure to the sun.

Poly also benefits by having less heat develop when a line is put in tension. Nylon is known to fail during storms/high winds because of internal heating. The failure can be anyplace in the line but worse in bends such as found in a chock.

Another reason why nylon is selected over poly is that it costs less.

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Old 30-01-2011, 12:43   #8
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Many folks now are switching to NER Polyester three strand, because of superior UV and chafe resistance. Also, Nylon gets weaker the moment it hits the water, polyester does not, and since it works less, and has more chafe resistance against itself internally, it should hold up better in a gale situation.

IMO, the "less stretch" issue is moot, if the line is over 50' and of three strand construction. If a nylon section of rode , only 50' long, stretched 10', and the same size polyester only stretched 5', that 5' is still PLENTY to absorb the shock. It doesn't need to be like a rubber band!

I have switched to smaller 1/2" polyester three strand for my 40' long springs, but if the dock situation called for a 15' section of spring line, I would drag out my old nylon.

For my main rope / chain combination rode, I have switched to NER Mega Braid, for its superior handling. If it comes out in polyester, I'd switch in a heartbeat!

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Old 30-01-2011, 13:22   #9
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You simply did not have poly ropes easily available in US back then (when most the guru books on cruising were written). Here in Europe we always used Poly.

Both are good choices but I would use Poly for any boat spending much time anchored in the sun. Poly has way better UV resistance.

Alas, Nylo seems the way to go if what you are looking for is a snubber - it is way more stretch than Poly.

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Old 30-01-2011, 13:37   #10
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wonder why you went with 3/8" chain on a Catamaran. For your displacement and windage, 5/16" G40 would have more than enough strength. It seems it would make more sense in a weight sensitive like a cat to go with a lighter chain and/or more of it.

The problem with line as an anchor rode is chafe. A boat dancing around in high winds has very high chaff at chocks etc that chafe gear is only marginally able to handle. I'd worry more about having any line in my anchor rode than whether it's polyester or nylon. I've had the displeasure of being anchored in 30 gusting to 50 wind conditions for several weeks. Keeping the snubber from chafing through was a 24/7 problem that I had to deal with.
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Old 30-01-2011, 14:29   #11
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i decided to go wtih the 3/8" G40 because of the added strenght...better to have to much than too little....it is about 90lbs heavier than 5/16th for the lenght i want.
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Old 30-01-2011, 14:30   #12
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Foggysail: Most sail covers and dodgers are made from Sunbrella (or similar) which is an acrylic, not poly.

I was taught that nylon was used for its stretch. Some stretch is desirable but there is more than one way to skin a cat... (apologies to cat lovers)

In addition to choice of material, one can choose various constructions. Three-lay is the stretchiest but has the disadvantage of twisting. Next is 8-plait construction, common in Europe, which I think is a good compromise. Least stretchy is double braid. Without looking up the specs I would guess that NER's 16-plait Mega-Braid is between 8-plait and double braid.

The concern about having stretch is important for reducing impact loads in extreme conditions, which is just one anchoring situation. If anchored Med-moor to a quay or bow-to a rocky shore stretch is a very undesirable characteristic for an anchor rode. I Med-moor bow in as a consequence of my particular boat; my stern anchor rode is double braid polyester so the boat doesn't surge into the quay (an all too common experience). I also use a Danforth Hi-Tensile which I consider ideal for the soft mud bottoms typical of old harbors. I would not use either rode nor anchor on the bow: different problem.
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Old 30-01-2011, 14:44   #13
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Quote:
Originally Posted by foggysail View Post
I believe its the stretch factor nylon offers. Nylon is susceptible the sun's rays more so than polyester. Polyester is the same material used for dodgers and so called canvas. Polyester thread is recommended to stitch those fabrics to avoid deterioration caused by exposure to the sun.

Poly also benefits by having less heat develop when a line is put in tension. Nylon is known to fail during storms/high winds because of internal heating. The failure can be anyplace in the line but worse in bends such as found in a chock.

Another reason why nylon is selected over poly is that it costs less.

Foggy
You are right that polyester is more UV-resistant than nylon.

Actually most "canvas" used for dodgers is Acrylic, not Polyester. The polyester thread used to stitch it has a life of about 8 years in the mid latitudes (less in the tropics), because the UV weakens it.
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Old 30-01-2011, 15:23   #14
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A robust rode in heavy swells

All Chain will not give your boat a good "ride" anchored in a heavy swell. A robust answer is to use double braid polyester with an eye splice in the last link of the chain. Use the largest diameter of polyester that will fit through the link, 5/8" for 3/8" BBB chain, for example.

Splice an eye on the bitter end of the polyester sufficiently large so as to acommodate an eye of nylon to pass through. Use 8 strand or 12 strand Brait nylon for large swells. You can stow 500-600 ft of 9/16" brait in a convenient-to-carry Rubber Maid laundry basket with handles. The nylon eye needs to be large enough to pass over the entire laudry basket and left on top. When stowed in the basket the line will run fast from it without snagging or hockling. When you need to add the nylon to your polyester pass the nylon eye through the eye of the polyester, pass it around the basket an snug up what will look like a square knot formed by the two eyes. This method is quick and easy to attach or remove. The two eyes will never break because there is double line of each at that junction.

At the boat make up a polyester line with eyes in each end so that one attaches to the horn of a cleat, around the cleat and sufficiently long to pass just outboard of the boat past a fairlead. Attach a nylon snubber having an eye in the end to the polyester eye outboard of the boat. Attach the bitter end of the snubber either to the chain or polyester double-braid or nylon rode using a Prussic hitch, which can be easilly attached or removed at will. The hitch will not slip if you tighten it sufficiently and if the snubber diameter equals or is less than the rode diameter.

This configuration will not break with chafe at at the cleat or fairlead. The rode does not have any weak-link shackles and can be maneuvered over a gypsy or wildcat during deployment or retreival.
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Old 30-01-2011, 15:25   #15
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I think you will find that the chain and swivels etc. are the weak points in strength, 3/8" cgain is only 5400 lb. working load, swivels and shackles about the same.
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