Polyester over nylon rode?

[Unity]

I’ve been looking for a lower stretch rode for my backup rode (I’m all chain, but I want a backup in case I must release my primary). Done tons of reading and googling here and come to conclusion that I’d be better with less stretch than 100% nylon and 8-plait is preferred for ease of handling. In my case, I need 1” @ 400 feet, so this is not a trivial investment.


Rocna has a nice KB where they say:

Polyester:

When polyester line is loaded to 20% of its breaking strength, it stretches between 2.2% and 2.9% depending on construction. Double braid nylon, in same situation will stretch 5.3% and three strand nylon 10%.

For larger boats, or for very long lengths of rope, we recommended polyester over and above nylon, as it (at least partly) addresses many of the disadvantages of nylon.
Furthermore, with larger vessels, while some shock absorption is still required, a bungee cord is not, and too much stretch (particularly in gusty conditions) creates problems with the boat's behavior at anchor. Polyester offers more control of the degree of stretch a given length of rope will introduce to the rode. For more stretch, a longer length of polyester can be used. With nylon, a typical anchor rode is going to quickly introduce too much.

Multi-braid:

Square, 8, or 10 plait rope makes ideal anchor rode. It is easy to handle and stows in less space than 3-strand.

Source: Rope (Rocna Knowledge Base)

I’ve heard about Octoplait (I believe 100% polyester) but have not found a US source under that name. I can order from UK
but felt like I may be missing the mark on my searches. And I’m unable to find the polyester over nylon that Rocna recommends.

Any recommendations for a source/brand of lower stretch rode (but not Dyneema/etc as that is too little stretch for me)?

Thanks all!

Chris

[barnakiel]

I hate nylon on anchor. I always use polyester there. Just maybe if you have an anchor winch then there is no difference. (I anchor by hand)



b.

[Nicholson58]

Stretch can definitely be an issue. I presume for your boat size your primary is chain. We found that 1-1/4 three strand snubber had too much stretch and switched to 1” Dynema for the snubber. Prior to that, the snubber would chafe through in a night or two.

We haven’t had to use the secondary even to kedge for almost eight years.

[billknny]

Originally Posted by Nicholson58

Stretch can definitely be an issue. I presume for your boat size your primary is chain. We found that 1-1/4 three strand snubber had too much stretch and switched to 1” Dynema for the snubber. Prior to that, the snubber would chafe through in a night or two.

We haven’t had to use the secondary even to kedge for almost eight years.

Obviously, if your chafing through a snubber in a day(!!!!), the problem is in your setup, not the snubber. Nobody else has that problem. Our snubber lasts at least 6 months of anchoring almost every day.

Using 1" dyneema is not a "snubber." You might as well just wrap the chain on the cleat.

Stretch is important. It dramatically reduces the peak load on the anchor. While too much stretch can be an issue, really it a far less a problem for the cruisers we see who use a short little snubber.

Four or five feet of line does nothing to reduce shock loadings on the anchor. We use 30 feet of 3/4 inch nylon (52 foot, 18 ton) and that is a good balance. If we expect rough weather, we bump up to 50 feet of 1" nylon.

Several US vendors do make 8 and 12 plait polyester lines. The make great rodes, really flexible, and a good balance of stretch and strength. As a extra bonus, they are really easy to splice.

[Unity]

Originally Posted by barnakiel

I hate nylon on anchor. I always use polyester there.

What do you use? A double braid line such as for a halyard?

I’m hoping to source an 8-braid (plait) in polyester or to learn more about this mythical “polyester over nylon rode” that Rocna talks about!

[kmacdonald]

Originally Posted by Unity

What do you use? A double braid line such as for a halyard?

I’m hoping to source an 8-braid (plait) in polyester or to learn more about this mythical “polyester over nylon rode” that Rocna talks about!

It's called "Polydyne": Yale Cordage | Polydyne

[Nicholson58]

Originally Posted by billknny

Obviously, if your chafing through a snubber in a day(!!!!), the problem is in your setup, not the snubber. Nobody else has that problem. Our snubber lasts at least 6 months of anchoring almost every day.

Using 1" dyneema is not a "snubber." You might as well just wrap the chain on the cleat.

Stretch is important. It dramatically reduces the peak load on the anchor. While too much stretch can be an issue, really it a far less a problem for the cruisers we see who use a short little snubber.

Four or five feet of line does nothing to reduce shock loadings on the anchor. We use 30 feet of 3/4 inch nylon (52 foot, 18 ton) and that is a good balance. If we expect rough weather, we bump up to 50 feet of 1" nylon.

Several US vendors do make 8 and 12 plait polyester lines. The make great rodes, really flexible, and a good balance of stretch and strength. As a extra bonus, they are really easy to splice.

The boat weighs 40tons. There is only six inches from the deck cleats to the hawse pipes. 1-1/4 nylon stretches enough to visually see it sawing over the edge of the hawse. We use Kevlar fire hose as chafe cover. Even so, the three strand nylon is gone in hours. I get all the bounce we need from the catenary sag in the heavy chain. Note that heavy commercial and private vessels do not use stretchy snubber. Most do not use snubber at all. We use the dynema to take the anchor load off of the bow rollers and windlass. We have not failed a snubber since we switched to dynema.

[thinwater]

I believe the obvious answer to the dilemma is that there is an optimum amount of stretch. 50-100 feet of nylon may be optimum in average conditions, depending on exposure.


Anchor on all-polyester in relatively shallow water and you will be hating life. I've done it in testing, and the impact loads were monstrous, exceeding ABYC recommendations. Bad.

• Add some chain (50-100 feet) and the chain catenary will absorb some.
• A multihull can use a nylon bridle. Not as good as chain plus a nylon bridle, but acceptable, if there is also some chain. I have used and tested this combination with some chain.
• Polyester can work if the length is LONG. It is not non-stretch, just less than nylon. Once you get to about 250 feet it is similar to a nylon snubber.

Obvious?

But often it is just as simple to reduce the stretch of nylon. For example...

• The chain in the rode is non-stretch. Use a good length of chain. Maybe a short length of Dyneema or polyester.
• A non-stretch snubber can be used. I'm currently using nylon rode with a Dyneema bridle. I like it a lot. The length of the snubber is logically subtracted.
• Oversized nylon will stretch less. Under 30-feet this is a good answer. I have often used 1/2-inch when only 3/8-inch was really called for. Easy to haul and wears like iron.

There are also ropes with intermediate properties (polyester-nylon blends).

The point is to look at the elasticity of the entire rode system, including chain catenary, rope material and size, and bridles. It's kind of like matching lures and line to the stiffness of a fishing pole. You can use Spectra fishing line for specific things, but you need to adjust the pole and the drag to match.

[thinwater]

Originally Posted by Unity

... or to learn more about this mythical “polyester over nylon rode” that Rocna talks about!

Google arborist rope sites. The have specific ropes that are used for dropping wood. Not rare, just not marketed as marine. Also rather stiff because of the tight weave. Polydyne is one of these.


I suspect it is mythical because he never actually sourced the rope. He may not have even tried it. There is other material on the site that is mythical too, IMO. Try the tandem anchoring methods on a beach, including a little wind shift, and you will see what I mean.

[Uncle Bob]

Originally Posted by Unity

I’ve been looking for a lower stretch rode for my backup rode (I’m all chain, but I want a backup in case I must release my primary). Done tons of reading and googling here and come to conclusion that I’d be better with less stretch than 100% nylon and 8-plait is preferred for ease of handling. In my case, I need 1” @ 400 feet, so this is not a trivial investment.


Rocna has a nice KB where they say:



Source: Rope (Rocna Knowledge Base)

I’ve heard about Octoplait (I believe 100% polyester) but have not found a US source under that name. I can order from UK
but felt like I may be missing the mark on my searches. And I’m unable to find the polyester over nylon that Rocna recommends.

Any recommendations for a source/brand of lower stretch rode (but not Dyneema/etc as that is too little stretch for me)?

Thanks all!

Chris

Could it be that the Rocna website is recommending the use of polyester over and above the use of nylon, as in polyester is in their opinion a superior choice to nylon?

[StuM]

Originally Posted by Uncle Bob

Could it be that the Rocna website is recommending the use of polyester over and above the use of nylon, as in polyester is in their opinion a superior choice to nylon?

Bingo! We have a winner!


The actual wording is:


For larger boats, or for very long lengths of rope, we recommended polyester over and above nylon, as it (at least partly) addresses many of the disadvantages of nylon.
Furthermore, with larger vessels, while some shock absorption is still required, a bungee cord is not, and too much stretch (particularly in gusty conditions) creates problems with the boat's behavior at anchor. Polyester offers more control of the degree of stretch a given length of rope will introduce to the rode. For more stretch, a longer length of polyester can be used. With nylon, a typical anchor rode is going to quickly introduce too much.

[Briney Bug]

Our thoughts are that polyester is a good choice for a rode-more chafe resistant than is nylon. However, as with any low stretch rode, you should use a nylon snubber. Even with nylon rodes we recommend using a snubber-better the snubber chafe, than the rode.
The harsher the weather, the bigger diameter and longer the snubber should be. Both the rode and the snubber should have a tensile strength that is at least 8x the highest load. For gale force conditions be at least 30' long, and for storm force conditions be at least 40' long; longer is even better. In chafe prone spots, other anti-chafe techniques must also be employed.
Rudy Sechez

[Gaia]

Excellent post and great replies. Even after anchoring thousands of times in all types of conditions and locales around the world over more years than I care to mention it is still easy to learn more. Tx to all.

Jim

[Unity]

Thank you everyone for some great feedback and advice. I went ahead and dove much deeper into this and thought I would share my analysis.

First, the critical question about the rode starts with determining the appropriate working load. ABYC has a nice chart that describes a simple set of rules for this (the actual calculations for true load, based on windage, waves and current are too complex but if somebody has a simple formula I'd be very interested).



Some say this chart is too conservative, resulting in too large a system. However, in my case my boat is 52 feet and as for "Violent Storm" I'd want around 6700 lbs working load. To help confirm this, my anchor chain is 7/16 grade 43 (G4) high test, sized for my windlass, which has a working load of 7200. So this number of around 6700-7200 makes sense to keep the chain and rope in consistent holding power.

The next thing I did was to locate a variety of rode types and looked up their specifications (it is disappointing how many vendors have poor specifications online, with Yale Cordage being a notable exception). I sized the rodes to come close to the correct working load, so there is a variety of diameters based on the rode type. I also applied the typical 5:1 (20%) tensile strength to working load factor (except 17% for nylon, as it loses 15% strength in water).

I built a chart then of elongation to understand how much the line will stretch when using 150' of rode (even though I will have 300' or more, 150' is a decent number to use for typical scope / depth).



For grins, I included polyproplyene even though I'd never use it for this application (and worth noting, I did not find one big enough for the working load). For Dyneema, I used one that has an outer shield of polyester so it can be easier to handle and tie down.

My take away from this analysis is that Dyneema has too little stretch and will be unacceptable without a bridal of something like nylon (only 1 foot of stretch at working load!) But more importantly, nylon stretches a lot and if in a serious storm with waves (hitting as much as 50% breaking strength) the elongation is substantial at around 30 feet. And if putting out the full scope (300 feet, which you would do in a serious blow) the elongation is more than a boat length. While the shock absorption is fantastic, it would mean a lot of sailing on the anchor as gusts stretch out the line and then pulling you back forward again.

100% double braid polyester is better at storm strengths, but ends up being pretty tight when used for typical weather anchoring (only 3.3 feet of shock absorption at normal working load). A nice mix does come from the polyester over nylon, where normal weather would see 7.8 feet of elongation, and serious weather (50% breaking strength) would be at 15 feet.

From this, it seems that polyester over nylon for a primary anchor makes sense. Worth noting, I do not take into account any length of chain, which of course changes the numbers and makes nylon a better choice especially at shorter scopes (less elongation at short scopes, but minimal change in elongation at full deployment).

For grins, I also took at look at weight, where 3 strand nylon is quite heavy (200 lbs for my application at 300 feet) and 8-strand brait or polyester over nylon are almost half that.



Now weight isn't that big of a deal overall, except for kedging. On my boat, I can't use a standard anchor for kedging - it's just too heavy (100 lbs for my Spade) or too massive (FX-85 for my Fortress). To handle on the dinghy, I'm using an FX-37 (21 lbs), which has a holding strength of 3,600 in soft mud. Using nylon 3-strand, the appropriate diameter is 7/8 line which is 45 lbs at 150 feet (sorry, this isn't in the spreadsheet, but the links to the web site data are there to look up different diameters). That's a total of 66 lbs. Workable for sure, but I dislike the stretch on nylon when using it to kedge. Switching to the polyester over nylon I could use a 5/8 line (easier to handle) which would weight 27 lbs for a total of 48 lbs, and would have a more acceptable stretch for this application.

I have put all this in a public shared spreadsheet on Google Sheets for anyone that wants to look at the analysis:

https://docs.google.com/spreadsheets...it?usp=sharing

As usual, I'd love critique on this analysis. I know there are tons of stories about "how my boat holds great", but I thought I'd try to take a more factual / technical view on this decision.

Chris

[roland stockham]

The simple answer is a length of chain through the rollers then attach the rode to that. Far more effective than chafe protector. I would only ever use nylon octiplait fo anchor rodes theselect the size to give the right amount of stretch. If it behaving like a bungy cord it is simply to small.