Perspective on Chain Length Vs. Sailing Performance

[Atcowboy]

Originally Posted by rgleason

It also keeps the nylon out of the water which causes a 15% reduction in strength.

Is your Samson post under water?

- AT

[rgleason]

Originally Posted by Atcowboy

Is your Samson post under water?

- AT

No Samson post here.

[Atcowboy]

Originally Posted by rgleason

No Samson post here.

Is your attachment point for your nylon line, be it bridal or snubber or rode any name/system you use or call it, under water?

- AT

[MathiasW]

Originally Posted by Atcowboy

Is your attachment point for your nylon line, be it bridal or snubber or rode any name/system you use or call it, under water?

- AT

For any decent length of snubber / bridle, that point will be under water unless it blows really hard.

After all, the snubber needs to stretch by 1-2 metres to be able to reduce the shock loads effectively. And it can do this only when it is sufficiently long to begin with. Given that the stretch should not exceed about 20%, a 1.5 metres stretch means the snubber needs to be 7.5 metres long. Unless much of this is running on the deck, this will mean part of the snubber will be in the water most of the time, unfortunately.

Cheers, Mathias

Anchor Chain Calculator

[Atcowboy]

Originally Posted by MathiasW

For any decent length of snubber / bridle, that point will be under water unless it blows really hard.

After all, the snubber needs to stretch by 1-2 metres to be able to reduce the shock loads effectively. And it can do this only when it is sufficiently long to begin with. Given that the stretch should not exceed about 20%, a 1.5 metres stretch means the snubber needs to be 7.5 metres long. Unless much of this is running on the deck, this will mean part of the snubber will be in the water most of the time, unfortunately.

Cheers, Mathias

Anchor Chain Calculator

Mathias,
I don't think anyone is arguing against that. Why I'm pressing rgleason is his slightly-fear-mongering comment about the breaking strength of rope changing wet vs. dry. I would hate for someone to read that and think it's bad practice to have the stretch happen above the water if that's what they need to stay safe. After all, unless your cleats are under water some part of the line is dry. Being wet can help keep the core temperature of the rope down also to prevent heat fatigue. But some of it is going to get hot if really pressed hard. I just think it's a good thing for sailors to have different strategies that they've at least read about so they can maybe try them if the need arises, and trying to undermine good strategies can rob learning sailors of them.

I don't think anyone would try to argue that you should have cleats under water so you can dock with purely wet lines.

- AT

[MathiasW]

Originally Posted by Atcowboy

Mathias,
I don't think anyone is arguing against that. Why I'm pressing rgleason is his slightly-fear-mongering comment about the breaking strength of rope changing wet vs. dry. I would hate for someone to read that and think it's bad practice to have the stretch happen above the water if that's what they need to stay safe. After all, unless your cleats are under water some part of the line is dry. Being wet can help keep the core temperature of the rope down also to prevent heat fatigue. But some of it is going to get hot if really pressed hard. I just think it's a good thing for sailors to have different strategies that they've at least read about so they can maybe try them if the need arises, and trying to undermine good strategies can rob learning sailors of them.

I don't think anyone would try to argue that you should have cleats under water so you can dock with purely wet lines.

- AT

Oh, I see! Got your point now!

If I understood rgleason's comment correctly, the point was made that wet nylon loses some of its strength.

In any case, though, a 15% reduction of strength is likely to be smaller than the fatigue caused by age, but I have to admit that I am not an expert here.

[Atcowboy]

Originally Posted by MathiasW

Oh, I see! Got your point now!

If I understood rgleason's comment correctly, the point was made that wet nylon loses some of its strength.

In any case, though, a 15% reduction of strength is likely to be smaller than the fatigue caused by age, but I have to admit that I am not an expert here.

The way I read the comment was that dry nylon had a 15% reduction in strength. Assuming this number (15%) is true I would take it to mean that wet nylon has a 15% *increase* in strength because I'm pretty sure ultimate breaking strength is measured with dry rope. I also think either way is kind of moot.

Hopefully the hypothetical sailor in this case has purchased rope based off of advertised ultimate breaking strength , divided by a reasonable safety factor, based on the intended use and how critical it is, which allows for some rope aging (loss of strength) from UV, cycling (core heating), a little chafing, etc.

I think that your age concern is a much more valid one, also. I think of my short snubber as sacrificial and replace the line often and don't really worry about chafe on it. In "bad" conditions I like to use my spring dock lines (50' three strand rope) as snubbers so they get cycle loaded instead of the rope anchor rode, again with the thought that they're more easily replaced.

- AT

[MathiasW]

Originally Posted by Atcowboy

The way I read the comment was that dry nylon had a 15% reduction in strength. Assuming this number (15%) is true I would take it to mean that wet nylon has a 15% *increase* in strength because I'm pretty sure ultimate breaking strength is measured with dry rope. I also think either way is kind of moot.

Hopefully the hypothetical sailor in this case has purchased rope based off of advertised ultimate breaking strength , divided by a reasonable safety factor, based on the intended use and how critical it is, which allows for some rope aging (loss of strength) from UV, cycling (core heating), a little chafing, etc.

I think that your age concern is a much more valid one, also. I think of my short snubber as sacrificial and replace the line often and don't really worry about chafe on it. In "bad" conditions I like to use my spring dock lines (50' three strand rope) as snubbers so they get cycle loaded instead of the rope anchor rode, again with the thought that they're more easily replaced.

- AT

I was reading it the opposite way - that wet nylon had a 15% reduction in strength, but let's wait for rgleason...

Cheers, Mathias

[rgleason]

The reason I mentioned this is Nylon actually looses 15% of its breaking strength when it is wet. This factor is apparently not well known, and I saw the deck mounting as an advantage, particularly when a snubber line might be sized a little smaller than the main line to provide "excellent stretch".

I don't know that much about this, but I've studied it using MathiasW's great tool and Bjarne's website and I've read some technical specs for various ropes. I still don't have a good intuitive sense of what is elastic enough for various conditions, but using these tools and making comparisons in different assumed conditions is very helpful.


..still trying to learn.

[Rumrace]

I walked into the chandelier ask for anchor rode. The fella pointed at a roll off 200’ 3/4” said “ reverse it when it gets dirty. It’s sure not three strand nylon or any floating rope.
We avoid nylon in scuba safety lines cause they are not safe. We only ever use it to find a body under ice. Nylon is really a poor plastic with a 15 year life span in the sun Max. It’s being replaced with two stronger plastics and it seems only rope folks don’t have the memo

[rslifkin]

Originally Posted by Rumrace

I walked into the chandelier ask for anchor rode. The fella pointed at a roll off 200’ 3/4” said “ reverse it when it gets dirty. It’s sure not three strand nylon or any floating rope.
We avoid nylon in scuba safety lines cause they are not safe. We only ever use it to find a body under ice. Nylon is really a poor plastic with a 15 year life span in the sun Max. It’s being replaced with two stronger plastics and it seems only rope folks don’t have the memo

There are plenty of non-nylon rope options out there (polyester as well as many newer developments). However, most are less stretchy than nylon. So for situations where stretchy line is needed, nylon is still common despite the issues with loss of strength when wet, poor chafe resistance, etc. That's why dock lines are typically nylon even on expensive sailboats using the highest tech fibers they can find for all of the running rigging.

[rgleason]

Approximately 15% loss of strength for wet Nylon Rope

https://www.qualitynylonrope.com/blo...ng-nylon-rope/
https://www.climbing.com/skills/wet-...yths-debunked/
https://www.usnetting.com/rope/selection-guide/
https://www.bairstow.com/v/vspfiles/...fety/N7806.pdf

Polyester rope has about 40% less stretch than nylon, and no loss of strength when wet. If you want a good elastic snubber it will need about 2x the length for equivalent elasticity.

[Atcowboy]

Originally Posted by rgleason

The reason I mentioned this is Nylon actually looses 15% of its breaking strength when it is wet. This factor is apparently not well known, and I saw the deck mounting as an advantage, particularly when a snubber line might be sized a little smaller than the main line to provide "excellent stretch".

I don't know that much about this, but I've studied it using MathiasW's great tool and Bjarne's website and I've read some technical specs for various ropes. I still don't have a good intuitive sense of what is elastic enough for various conditions, but using these tools and making comparisons in different assumed conditions is very helpful.


..still trying to learn.

How fantastic to read about! Especially since I have been considering making my general use snubber out of thinner stuff so I can get more stretch, mainly when using it to pull the rode tight when the anchor is stowed in the roller. Right now it is half inch, and I just cannot sweat it enough to get it REALLY tight. 3/8" I'm sure would do that.

since we have so thoroughly hijacked the thread.... I wonder if the OP noticed any difference with his new rode?


- AT

[Dockhead]

Originally Posted by rgleason

Approximately 15% loss of strength for wet Nylon Rope

https://www.qualitynylonrope.com/blo...ng-nylon-rope/
https://www.climbing.com/skills/wet-...yths-debunked/
https://www.usnetting.com/rope/selection-guide/
https://www.bairstow.com/v/vspfiles/...fety/N7806.pdf

Polyester rope has about 40% less stretch than nylon, and no loss of strength when wet. If you want a good elastic snubber it will need about 2x the length for equivalent elasticity.

This actually understates the risks associated with nylon.

Dashew, "The Right Rode", https://www.petersmith.net.nz/boat-a...right-rode.pdf tells more.

Nylon is highly susceptible to chafe, and is susceptible to sudden unexpected failure if highly loaded. Snubbers should always be thick enough and long enough not to get anywhere near their maximum stretch.

And what's really important, is NEVER rely on a nylon snubber as the only connection between the anchor chain and your boat. You should always use a chain lock or a strop which is as strong as the chain, in addition to the snubber.

[rgleason]

Originally Posted by Dockhead

This actually understates the risks associated with nylon.

Dashew, "The Right Rode", https://www.petersmith.net.nz/boat-a...right-rode.pdf tells more.

Nylon is highly susceptible to chafe, and is susceptible to sudden unexpected failure if highly loaded. Snubbers should always be thick enough and long enough not to get anywhere near their maximum stretch.

And what's really important, is NEVER rely on a nylon snubber as the only connection between the anchor chain and your boat. You should always use a chain lock or a strop which is as strong as the chain, in addition to the snubber.

I had not read this, thank you for linking it. I normally read Steve Dashew with some filters due to grandstanding, but find this part useful

"Further investigation with rope manufacturers revealed several startling facts. First, the rated strength of nylon drops by 15 to 20% when it is wet, as compared to the catalog breaking strengths (which are dry rated). Second, when nylon is repeatedly cycled at a high percentage of its breaking strength, typically above 50%, it generates substantial amounts of internal heat. This internal heat degrades the structural performance of the nylon,

I considered getting 8-strand polyester, in fact Novabraid kindly offered to make some for me as a test, because they noticed European Rope Manufacturers were doing this for anchor lines.

Inherent in what Dashew and you write is the assumption that there is an all-chain rode on the boat.

I have determined that for my current use, and after 32 years of sailing, there is no need to carry around hundreds of pounds of chain. Instead I slightly upsized to 5/8" 8-plait to reduce stretch a little and and reduce %breaking strength to below 20% at 50knts, finding about 200' of Bucanneer remnant at Defender for $75 and adding 30' of chain. I am going to provide better chafe protection for the line at the thimble splice (5') which should be sufficient for my cruising grounds. However, some day I may change to 8-braid polyester.

Sure for you, a world wide cruiser, you need to carry around 200 lbs of chain, and haul and deploy it with your electric windlass. Use cases are different.