Stresses on Mooring Lines

[Neeves]

I have 2 or 3 similar pictures - but no background.

I think elasticity in mooring lines, whether a rubber dog bone thing, or fancy stainless steel spring or some form of nylon mooring line, all with chafe protection, would be advantageous. Leaving your yacht with minimalist mooring lines is asking for trouble.

Jonathan

 

[Stemar]

I crawled along the club pontoon one very stormy day to try and re tie the many boats that had snapped mooring lines.
3 boats had those rubber snubbers in their lines and all 3 had no snapped lines. The other 7 boats with no snubbers all had snapped lines.

You're a braver man than me. I spent the night on my boat in a bad storm so I could tend the lines and keep an eye on the other boats, but when it was bad enough to be worth going down the pontoon to check, I took one look at the way everything was leaping around and chickened out.

I had a rubber bone on my anchor snubber, but never on the mooring lines. I prefer to arrange them so the lines themselves provide elasticity.

 

[Spirit (of Glenans)]

Throughout my twenty-odd years of boat ownership I have relied on the guidance published on the website of Jimmy Green Marine, and have always been a satisfied customer.
Mooring Information | Guides and Charts

 

[LONG_KEELER]

I remember a chandlery that didn't sell 3 strand nylon rope unless to order. Like many, it's gone now.

I'm starting to recall the reasons why the chandler did not stock 3 strand nylon rope.

It was something to do with the lay becoming distorted over a period of time as each swing to the tide on swinging moorings. Perhaps this happens when the rope goes hard.

 

[fredrussell]

View attachment 132534

I reckon those rubber doo-dads don’t like being left in the sun too much - rubber will harden and lose its stretch.

 

[NormanS]

I am very seldom tied alongside anything, but on one occasion a few years ago, with an engine problem, I had to remain alongside the pontoons at Tobermory. The wind was fresh out of the NE, the worst direction for Tobermory. I went to the garage and borrowed a couple of old car tyres, and used them as snubbers on the most appropriate lines. They made a huge difference. I have since made up a couple of lines with the "dog bone" things, and would use them when needed.

 

[lustyd]

I certainly use doubled up ropes in winter,

I assume you mean two separate tied lines rather than a doubled line (RYA parlance for looping around a cleat and back to boat). A loop of line will be more elastic but will chafe through in short order once the weather gets up due to movement.

I had a rubber bone on my anchor snubber, but never on the mooring lines. I prefer to arrange them so the lines themselves provide elasticity.

It's not actually possible to achieve the same effect with ropes. I used to think the same until I moved to a more rambunctious marina. To achieve the same stretch and damping with ropes alone they'd need to be much more than a boat length. Even then they would not provide the damping effect. The difference is night and day when they are needed, although my default position would still be to not fit them unless you're in a place that needs them.

 

[lustyd]

I reckon those rubber doo-dads don’t like being left in the sun too much - rubber will harden and lose its stretch.

They don't wear in the sun at all, they use EDPM the same as modern flat roofs. The wear comes from repeated stretching while protecting the boat, and as the Jimmy Green website says this is a consumable well worth paying for compared to boat damage.

 

[lustyd]

Yes, I thought that - I remember reading a comparison of synthetic ropes (I’ll see if I can find it and link to it), which said that polyester had higher uv resistance than nylon, but that didn’t matter for climbers as they didn’t leave their ropes out for days on end.

Edit: nope, can’t find it, and it seems polyester and nylon have similar uv resistance.

Sorry, I was thinking of polyprop, ignore that comment

 

[johnalison]

I reckon those rubber doo-dads don’t like being left in the sun too much - rubber will harden and lose its stretch.

You can always tell how quiet a harbour is by the proportion of local boats using spring snubbers. My marina is too sheltered to make a snubber necessary, but if I did need one on my permanent mooring one I would only consider the spring type. I carry rubber snubbers for use away from home but generally don't deploy them as the weight makes the lines clumsy. Although long lines are ideal, the geometry of berths often means that short lines are necessary and a snubber can make the difference between sleeping or not sleeping, which is enough for me.

 

[Refueler]

I do not use Nylon ... I use Polyprop ....

I also recycle halyards into mooring lines when I replace .... mainly as 'first ashore' long lines.

One practice that I wish people would learn not to do : Doubling lines is not just pass it round shore point and back to boat. That pass round shore point is now its weak point as it will chafe .... Doubled should have each individual line secured

I personally hate those 'snatch items' lines are wound round or to ... my preferred is to lead the line further to get stress spread over longer length.

I have had a mooring line part in Yarmouth Hbr (IoW) during a storm some years ago ... wife and I were on-board when it happened ... line was a 12mm Marlow Polyprop from midships cleat to forward on pontoon .. 25ft 4ton Motor Sailer ... line parted about 1/2 metre from shore point ... sound was like shotgun going off ... so chafe was not reason
Luckily - I had bow and stern lines / springs doubled ...

Same night - HM had to rescue two other boats that had parted moorings and were liable to damage others ...

 

[pessimist]

We have just spent the winter, including the named storms, on a mid river pontoon moored with 14mm nylon to 4 of these. Cat of similar displacement to the O.P. We use the largest size. Highly recommended and not too expensive. At a guess we could have saved a bob or two by using Polysteel. May experiment next year.

 

[thinwater]

Obviously, many things will work. In the US you would have trouble finding a polyester dock line; they are all nylon for shock absorption. Only boats over 60 feet use polyester (the math is different for truly heavy boats because they react to waves differently). I have used polyester several times, and compared to nylon, I can only say it is a rough ride and the forces will be several times higher. Your choice, but that is what the math says. As for chafe, only if they are not properly rigged and protected.

Polyester is used on mooring pendants, since the mooring chain and the float pulling underwater provide shock absorption and polyester is more chafe resistant.

As for UV, the lines are treated to be resistant, and really, they should be replaced every 5 years or so to maintain shock absorption, so UV is never actually an issue, until the line is laughably old.

 

[Refueler]

P

You can always tell how quiet a harbour is by the proportion of local boats using spring snubbers. My marina is too sheltered to make a snubber necessary, but if I did need one on my permanent mooring one I would only consider the spring type. I carry rubber snubbers for use away from home but generally don't deploy them as the weight makes the lines clumsy. Although long lines are ideal, the geometry of berths often means that short lines are necessary and a snubber can make the difference between sleeping or not sleeping, which is enough for me.

Pal of mine with his B31 - Ventspils Yacht Harbour .... two bow lines to pontoon - each with spring snubbers .... stern line to buoy ...

He got call from YH ... one spring snubber had failed - leaving him hanging on ONE bow line.

I don't like mooring snubbers and those spring ones I like the least ... at least with the rubber dog-bone - if it fails - the line is still secure !!

 

[pessimist]

P


Pal of mine with his B31 - Ventspils Yacht Harbour .... two bow lines to pontoon - each with spring snubbers .... stern line to buoy ...

He got call from YH ... one spring snubber had failed - leaving him hanging on ONE bow line.

I don't like mooring snubbers and those spring ones I like the least ... at least with the rubber dog-bone - if it fails - the line is still secure !!

We used a safety line across the springs in cae of such eventuality. Fortunately wasn't needed.

 

[Refueler]

We used a safety line across the springs in cae of such eventuality. Fortunately wasn't needed.

Guess what he has now !!! I told him to ditch them and be a proper sailor !!

 

[fredrussell]

…I don't like mooring snubbers and those spring ones I like the least ... at least with the rubber dog-bone - if it fails - the line is still secure !!

You tie those spring snubbers with one continuous line knotted at two points, one to each end of spring, with a short length of line (enough to allow expansion of spring) between knots.

 

[Neeves]

View attachment 132534

I have 2 or 3 similar pictures - but no background.

I think elasticity in mooring lines, whether a rubber dog bone thing, or fancy stainless steel spring or some form of nylon mooring line, all with chafe protection, would be advantageous. Leaving your yacht with minimalist mooring lines is asking for trouble.

Jonathan

I think the reason for failure may be in the picture. I don't recall installation instructions but its something like 3 or 4 wraps of the rope round the 'long bit' of the device. 3 or 4 wraps means the wraps limit the stretch of the dog bone thing and the rope itself increasingly takes the stress. Looking at the space between the 2 ends of the device there seems to be room for far too many wraps of the rope. Consequently the dog bone thing would have been over stretched - and failed.

The late John Knox and I both tested these dog bone things for their elastic qualities and came to the same conclusion they are expensive for what they are in an anchoring situation (and heavy (as mentioned). I don't recall the detail but one dog bone thing had the equivalent elasticity of the appropriate sized 3 metre length of nylon. So a decent snubber of, say, 10m would be the equivalent of 3 dog bone things. Its a no brainer and I declined to recommend them. (and stainless springs) However in a mooring environment where mooring rope lengths are short the dog bone things come into their own.

Chop in a marina is also an environment where a dog bone thing (or spring - I have never tried one) would be useful as the movement is not large but sharp and long mooring lines are not, necessarily the answer. As mentioned if they fail the mooring line is still there - as is clearly illustrated in my photo.

As yacht movement at anchor also varies (the difference between the effects of chop and wind), in a similar way it varies in a marina, I added dog bone things to my 30m bridle - but have not yet reached a conclusion. I'm persuaded to try an elastic bridle and dog bone things as we use various mechanisms or devices on our cars to make the ride more smooth, shock absorbers, tyres, springs, foam in the upholstery etc and if varied devices work on a car - why not varied devices on a yacht?

However - I emphasise, I am not using the dog bone things as a replecament of a snubber, nor to allow reduced snubber length. The dog bone thing is specifically to better tame chop. If you want a longer snubber, or more elasticity - use a longer snubber. See the article in the July 2021 article in YM. To enjoy the benefit of elasticity nylon is ideal, or the best of a bad bunch, and nylon is much cheaper than a dog bone thing.

Jonathan

 

[jdc]

I'm always taking a contrarian view, but fwiw I hate the idea of using climbing rope aboard, especially for mooring lines.

1. Dynamic climbing rope doesn't stretch in the elastic sense, it permanently distorts and gets longer if it experiences force above a defined limit. Once the force has gone it doesn't return to it's original length but stays permanently stretched. So it's actually useless in this application because once stretched it loses its elasticity. Think about it: you really, really, don't want energy stored in the rope if you fall - that way you will hurt yourself by bouncing up again to smack the rock face. The rope has to absorb the energy so you just slow down and come to a blissful stop - hopefully before hitting the ground. That destroys the rope after a couple of falls. The exact opposite to what one needs or expects of a mooring.
2. There are two main types of climbing rope: dynamic and static. Static is what climbing walls use. That's because on climbing walls you have a top-rope and a person (or machine) belaying you so you won't fall far. It doesn't stretch and doesn't therefore distort, but it's just ordinary dyneema or polypropylene. It gets thrown out by climbing walls once it has got old so to buy it for elastic properties is dumb: it never had any!
3. I hate braided ropes anyway for mooring lines. You have absolutely no idea if it's still strong or about to part. You can't see the inner core. If spliced, it's even more of a pig in a poke ( I don't splice braided ropes but that's another debate).
4. That most people get away with this only goes to show how small the forces actually are on mooring lines, so why on earth go to all that trouble for something more expensive but actually inferior to simple 3-strand?

Just choose 3-strand polyester. It's safe, and cheap and works extremely well. You can see if it's getting abraded and past its best when you can simply bin it. Use 8-plait by all means if you want to swank (it's no better, but hey-ho, it looks like you spare no expense).

PS: I'm a climber, I use dynamic climbing rope for climbing and I throw out the rope if I have a real fall because it's now used up its stretch. If you're not a climber, I respectfully suggest that talking about using 'climbing rope' - like there's only one type - is the mantra of an ignoramus.

 

[Neeves]

I'm always taking a contrarian view, but fwiw I hate the idea of using climbing rope aboard, especially for mooring lines.

1. Dynamic climbing rope doesn't stretch in the elastic sense, it permanently distorts and gets longer if it experiences force above a defined limit. Once the force has gone it doesn't return to it's original length but stays permanently stretched. So it's actually useless in this application because once stretched it loses its elasticity. Think about it: you really, really, don't want energy stored in the rope if you fall - that way you will hurt yourself by bouncing up again to smack the rock face. The rope has to absorb the energy so you just slow down and come to a blissful stop - hopefully before hitting the ground. That destroys the rope after a couple of falls. The exact opposite to what one needs or expects of a mooring.
2. There are two main types of climbing rope: dynamic and static. Static is what climbing walls use. That's because on climbing walls you have a top-rope and a person (or machine) belaying you so you won't fall far. It doesn't stretch and doesn't therefore distort, but it's just ordinary dyneema or polypropylene. It gets thrown out by climbing walls once it has got old so to buy it for elastic properties is dumb: it never had any!
3. I hate braided ropes anyway for mooring lines. You have absolutely no idea if it's still strong or about to part. You can't see the inner core. If spliced, it's even more of a pig in a poke ( I don't splice braided ropes but that's another debate).
4. That most people get away with this only goes to show how small the forces actually are on mooring lines, so why on earth go to all that trouble for something more expensive but actually inferior to simple 3-strand?

Just choose 3-strand polyester. It's safe, and cheap and works extremely well. You can see if it's getting abraded and past its best when you can simply bin it. Use 8-plait by all means if you want to swank (it's no better, but hey-ho, it looks like you spare no expense).

PS: I'm a climber, I use dynamic climbing rope for climbing and I throw out the rope if I have a real fall because it's now used up its stretch. If you're not a climber, I respectfully suggest that talking about using 'climbing rope' - like there's only one type - is the mantra of an ignoramus.

Contrarian views are hopefully welcomed.

12mm Dynamic climbing rope has been used for decades as a snubber for anchoring. Starzinger Evans Starzinger - Wikipedia was a strong proponent - and I think was one of the earliest users. Through this and other forum there are many examples of use of climbing rope as a snubber and a wealth of information. I think you will find a significant number of people on this forum alone who use retired climbing rope as a snubber. Climbing rope in an anchor situation is not used in isolation but with a chain rode and the combination of energy absorption of catenary and the elasticity of climbing rope seems to work in practice. I too was a rock climber, (I go back to the days when we used 3 ply Viking ropes) and whereas what you say is correct - as I say in practice, it works. There is a difference between a rock climber falling a considerable distance and using the rope to its maximum ability and stretching 30m of kermantle by 1m (say by 3%)

Nylon has the ability to stretch 40% at which point it will fail - I think if you have a 10m length of climbing rope as your mooring line you will be surprised if it stretches even 1m. I can stand on our bow and watch the snubber stretching, back and forth, elastically (on the assumption going back and forth is elastic). I actually have a mark on the deck coinciding with one on the climbing rope snubber, when at rest, so that I know how much stretch exists at any given time (and wind speed). The major disadvantage of climbing rope in a mooring application is the difficulty of how to secure it - the rope lacks tactility. For a snubber this does not matter - you (or a sail maker) can sew eyes.

You say climbing rope used in gyms does not stretch - they are made from nylon, nylon stretches upto 40% - precisely how do manufacturers of climbing rope stop nylon stretching?

As Thinwater mentions mooring lines will age and should be replaced. Its the same with a snubber in an anchoring environment, they are consumables and should be replaced (as you similarly replace your sails or your chain, when the gal wears off). We use 30m snubbers, 12mm dynamic climbing rope and carry spares. We have broken 2 snubbers, in 25 years - but before we started using climbing rope. All ropes age through cyclic loading, evident in both an anchoring or mooring environment - but the cycles are generally benign, the cycles are spread over number of warps or the chain and snubber. The anchor rode is not perfect as catenary has a finite ability to absorb snatch loads - there is a need for something that offers energy absorbing ability when the catenary has, largely, disappeared.

I think it would be invaluable if you took some climbing rope, dynamic 12mm kermantle and try it as a, long, snubber - and then report back. Your comments are correct but you are not applying what you know to an anchor situation, nor tied to a pontoon in a marina. Your comments are invaluable - so extend you experiences and knowledge and try using 'climbing rope' in an anchor rode or as mooring warps - and then report back. Maybe also read the background to Starzinger in the Wiki link.

Finally - retired climbing rope largely goes to land fill - and must last for centuries. Being able to recycle perfectly good rope seems an ideal objective.

Jonathan