Breaking Docking Lines

[David M]

3-strand nylon, rubber shock absorbers and hose used as chafing gear at the chocks works much better. Not forever, but better.

[zeehag]

i donot t ie my boat tight to a dock. i have yet to break a line. i HAVE popped cleats of f the dock in 215 steady and 150+ gusts , named opatricia, but never popped a line. not ever snapped a mooring line, either. but i was taught longer is better , no tugging no jerking movements at rest. makes a difference.,
those around me who tie tight to a floating dock pop lines each time 45 plus kts breeze arises. oopsy.
i use no snubbers nor chafe gear when i am in a marina--not even during patricia. no i donot have any chafe except on the line i used on the piling. that has outer casing cleanly removed on one side.. not an issue. i am still using my patricia lines to tie to dock in mazatlan.
the chafed line was a mooring pennant in san diego, now is my main piling tie line. still in use. i use outer casing as chafe gear hahahahaha
i make sure my boat can move naturally in its slip so i donot break lines for no reason.. yes i have survived pnw storms in san diego, i have endured winter el nino storms in lost angeles...all using same exact tie off techniques and never knock wood sprung or popped or snapped a dockline or mooring line ever. been at this since 1955.
i cannot see breaking a dock line as good for the boat... for each action there is an equal and opposite re-action. make sure that re-action does not harm your equipment.

[Dockhead]

Originally Posted by Terra Nova

Nylon 3-strand dock lines outlast polyester braid at about 10:1.

Got a link to a test, for that?

That contradicts my experience.

Also, 3 strand is also nasty for docklines -- hard to flake and store, and doesn't stretch evenly like octo does, tends to twist and unlay itself. Especially in bigger sizes (over 20mm). Octo is nicer in every way except only that it is a little harder to splice. I do keep nylon octo lines on board for different special purposes, including for snubbers.

[Dockhead]

Originally Posted by jckb

+1

Rubber snubbers are a triumph of marketing hype over logic.

A spiralled line, wrapped around a rubber shaft, when straightened will increase it's reach by about 15% of the snubber's length - cos 30. For 18inch snubber, that's not more than 3 inches.

Dock lines will usually be at least half your LOA. Otherwise, up/down snatching becomes too violent. Let's say 21ft free play.

Nylon, depending on the lay, stretches up to 10% before deforming or weakening. That's 2ft of the free play. Polyester, about 3% - say 7.5 inches

Nylon = 24 inches of spring. Polyester + snubber = 10 inches of spring.

A triumph of marketing hype over logic.

JimB

But what you're missing here is that the rubber buffer can absorb a huge amount of energy in those 3 inches (or whatever) or travel. You have to use them right -- at straighter angles to the dock, then you have your normal docklines without buffers. Rubber buffers are a unique way to add springiness to a short line, to a line which can't be long enough to get compliance from the rope itself. That's their purpose.

Nylon is certainly springier than poly -- no question. But nylon can be eaten through by chafe in hours -- and chafe can occur against something which you just didn't see before the storm. Of course you can mitigate this with really good chafe gear, but why go to all that trouble when poly is far more resistant?

My boat spends winters in Cowes Yacht Haven -- notoriously bouncy in Nor'easters, and we get hurricane force winds at least once a year. A lot of broken dock lines every year, almost all of them nylon.

I think what Dashew wrote here about nylon anchor rode applies equally to dock lines:

dashew-right-rode-2.pdf

[greybeardloon]

How do you guys feel about the metal spring snubbers used a lot in the Med for docking lines?

[Terra Nova]

Originally Posted by Dockhead

Got a link to a test, for that?

That contradicts my experience...

Just a lifetime of owning boats.

[Dockhead]

Originally Posted by greybeardloon

How do you guys feel about the metal spring snubbers used a lot in the Med for docking lines?

They are used in the Med a lot because Med mooring requires at least two lines which are too short to give good stretch.

They are also used a lot around here, and seem to work very well. They are more robust than rubber ones, but will give you a hard snatch when you get to the end of their energy absorbing ability. They also creak, which is not so good if you're sleeping on board. That's why I prefer the rubber ones.

[JPA Cate]

Fwiw, we have never had nylon 3 strand dock line or anchor rode unlay itself. I was astonished to read that had happened to Dockhead! Chafe, yes, it will, and chafeguards help.


Assuming the OP is side tied, I would suggest adding fore and aft spring lines that run at least the length of the boat, in addition to the other dock lines. If at all possible, one more from the other side of the cat, amidships, or stern, to the dock forward, sharing the cleat with the off side bow line--this one will help keep it from leaning so hard against the dock when the wind is from the direction that makes it do it.

Ann

[jckb]

Originally Posted by Dockhead

But what you're missing here is that the rubber buffer can absorb a huge amount of energy in those 3 inches (or whatever) or travel

Energy = mv(squared). Arresting a boat from a given speed will always transfer the same energy. It goes to dock motion, wave reaction, or heat in the rope.

Energy = force x distance. If stopping the boat over 3 inches (snubber), instead of 21 inches , you'll need x 7 the force to stop the boat. 7 times more likely to reach failure . . .

You have to use them right -- at straighter angles to the dock, <snip>
Rubber buffers are a unique way to add springiness to a short line, to a line which can't be long enough to get compliance from the rope itself. That's their purpose.

Hmm. Better; never use short lines. Always work at an angle Even 15ft polyester stretch improves on snubbers . . .

Nylon is certainly springier than poly -- no question.

x 3. And the data I was using was working load data, about 1/3 the "30% stretch to breaking" criterion

But nylon can be eaten through by chafe in hours -- and chafe can occur against something which you just didn't see before the storm. Of course you can mitigate this with really good chafe gear, but why go to all that trouble when poly is far more resistant?

There is marginal chafe difference between poly and nylon of similar weave. Far more important is the differences between surfaces. Braid sheathing gives excellent protection compared with stranded rope.

My boat spends winters in Cowes Yacht Haven -- notoriously bouncy in Nor'easters, and we get hurricane force winds at least once a year. A lot of broken dock lines every year, almost all of them nylon.

Break the habit of using short, straight lines with snubbers to try to hold the boat rigidly in it's berth.

Rope specifications and science is part of " 'elf 'n safety". Well documented. Google "rope specifications".

[jckb]

Originally Posted by greybeardloon

How do you guys feel about the metal spring snubbers used a lot in the Med for docking lines?

Just like snubbers, but about x 2 the travel, x 2 the price, much noisier, and must be used with a safety chain link for the day it breaks when you're not there.

Another triumph of marketing hype

JimB

[jckb]

Originally Posted by Dockhead

They are used in the Med a lot because Med mooring requires at least two lines which are too short to give good stretch.

??? Splay the lines.

[Dockhead]

Originally Posted by jckb

Energy = mv(squared). Arresting a boat from a given speed will always transfer the same energy. It goes to dock motion, wave reaction, or heat in the rope.

Energy = force x distance. If stopping the boat over 3 inches (snubber), instead of 21 inches , you'll need x 7 the force to stop the boat. 7 times more likely to reach failure . . .
Hmm. Better; never use short lines. Always work at an angle Even 15ft polyester stretch improves on snubbers . . .

x 3. And the data I was using was working load data, about 1/3 the "30% stretch to breaking" criterion
There is marginal chafe difference between poly and nylon of similar weave. Far more important is the differences between surfaces. Braid sheathing gives excellent protection compared with stranded rope.

Break the habit of using short, straight lines with snubbers to try to hold the boat rigidly in it's berth.

Rope specifications and science is part of " 'elf 'n safety". Well documented. Google "rope specifications".

"7 times more likely to reach failure . . ." Only if the strength is the same.

In general I agree with you about always having an angle on the dock lines -- that's key, and un-buffered short straight lines are, of course, the ones which people break.

But the other thing you don't mention is snatch loads. To remove snatch loads as much as possible, you need to immobilize the boat from as many different angles as possible. Here a couple of short lines really helps a lot. It also seems to dampen resonance. That's what I use the rubber buffers for. Besides that, use a lot of lines. Someone above suggested rigging proper bow and stern lines led far aft and far ahead -- that's really good advice. I have 8 cleats on my boat, so two sets of midship cleats. I use these to the max to create a web of spring lines -- when I'm leaving the boat in a difficult place like Cowes, for longer periods which might include storms.

Concerning the "marginal difference" in vulnerability to chafe between nylon and polyester -- I beg to disagree. As does Yale Ropes:

"Dick Hildebrand, Vice President at Yale Ropes indicates that in some conditions 'polyester line is as much as ten times better than nylon in dealing with chafe.'"

Quoted in Dashew's "The Right Rode", here: dashew-right-rode-2.pdf where you will read a pretty serious condemnation of nylon for such uses.

[Dockhead]

Originally Posted by jckb

??? Splay the lines.

Not always practically possible!

Hence the common use of buffers.

[zeehag]

theory vs experience and practicality and reason.
some folks never learn./ some know from very young ages what to do and not do.
crunch your numbers all you want, but the reality is a lil different from the theory.
sensibility and practicality win every time.

[jckb]

Originally Posted by zeehag

theory vs experience and practicality and reason.

Not theory vs experience. They inform each other. Experience shows the need. Solutions evolve over time - Darwinian stuff. Physics and dynamics give insghts for disruptive ideas, to be tested.

My 60 years include hemp and 75 ton old gaffers, dyneema and RORC circuits, 15 years of laying up charter fleets, at anchor, on moorings, on marina pontoons and concrete quays. That's lots of testing time.

Theory came from 20 years modelling dynamic behaviour as a career. 'til I took to the sea full time . . .

I've still got L plates . . . . never stopped learning.

For anyone who wishes to understand rope performance, I'd strongly recommend downloading www.samsonrope.com/Documents/Rope_Users_Manual_WEB.pdf

JimB