Polysteel vs Nylon mooring lines

sarabande

sarabande

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for a standard fore and aft mooring, or single buoy mooring it seems that some of the newer polysteel ropes are finding favour.

Polysteel has many advantages:

greater strength for the same diameter
floats
lighter weight
UV resistance

and some disadvantages:

longer splices needed
lower melting point under load
less elongation under snatch loads.


It's the last item under present consideration.

Typically, for a boat moored to a single buoy (assume a distance of 5m between the buoy and the cleat on board, for braidline nylon rope, a load of 50% of WLL results in a 20% elastic/visco-elastic extension; thus giving an extension of 1m. (Load figures are for steadily applied load BTW, not for snatch loads experienced under strong tidal and wind conditions).

For polysteel rope, typical figures for the same load (WLL) are IRO 2 to 5% extension. However, for the same load as the braidline, the extension will be <2%, so around 0.1m

I'm trying to exclude from the assessment such prudency factors as securely fixed cleats and and a true running fairlead between the cleat and buoy (often a source of heat degradation, apparently).

Two questions:

1 Given that the buoy (or buoys for F&A mooring) provide a certain, generally unquantifiable, amount of movement under shock load, how important is is that a mooring line should have a large extension factor ?

2 Are you happy to have a polysteel mooring line of considerably thinner diameter (say, 14mm) against a nylon line of 20mm, for a similar breaking strain ?
 
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sarabande said:
2 Are you happy to have a polysteel mooring line of considerably thinner diameter (say, 14mm) against a nylon line of 20mm, for a similar breaking strain ?
Click to expand...

What's the advantage of a thinner line? I'd always rather have the thickest one that will properly fit the fairleads and cleats, because why not? We're only talking a few metres, so cost won't make much difference.

Pete
 
I'm not sure that polysteel is being pushed as a replacement material for mooring strops. For a start it is not really very nice to handle, fairly hard and stiff. Where it does have advantages is in replacing the all chain riser. I replaced my fore and aft risers with 32mm polysteel risers a couple of years ago. Splices can replace shackles and a much smaller mooring buoy can be used because it's not trying to hold up a massive weight of chain.
I still use nylon octoplait strops because they are much nicer to handle. Shock loadings are much reduced by having a much smaller mooring buoy.
 
The buoyancy of the buoy, if it is of 'adequate' size, will serve as a shock absorber as it is dragged under when there is a pull on the painter... rather like the function of an angel on the anchor rode in reverse. The only time that the elasticity of Nylon comes into play is when the pull of the boat is such that the painter and the riser become one straight line; when that happens it is time for more scope. Regarding the solidity of the cleats, it is always more prudent to take the mooring line beyond the cleats and to make it fast to something that is really solid, like the mast. This is especially important if the boat is wooden.
 
For the past year or so I've been using a 32mm 8-strand seasteel strop. Size based on what would fit in the roller. Splices were very easy to do. I drop the soft eye over the windlass as it seems just as well bolted down as the cleats, in fact moreso because the load is spreader over a greater area. The pickup line is looped round a cleat as well for tidiness. I have noticed a bit of wear where the piece of flexible hose, that I use for chafe protection, had slipped once.

I believe that you don't really want lots of stretch as that causes movement in the roller and therefore chafe.
 
I can't see where stretch between bow and buoy is relevant, at least not with a swinging mooring. Many people use chain between bow and buoy. Any surging will be taken by the riser, and in extremis by lifting the start of the ground chain.
 
My riser and twin strops are polysteel. Strops are 4 strand + centre core 24mm and outlast same size nylon by several years. No UV degradation and no burning with stretch over the rollers. Although fairly stiff when new, softens up after a few weeks.
 
I don't know others feel, but I have never been a fan of 3 strand nylon.

It goes very hard after being in contact with salt water. The lay tends to distort, particularly with
swinging moorings . Not nice to handle too after being in a damp anchor locker.

I tend to blow the bank with either polyester or, better still, multiplait although I can't splice the stuff.
 
In reply to your two questions:

1. Stretch in the strop attaching the boat to the mooring buoy is a really bad thing as it engenders movement and thus chafe. The buoy will move enough due to the chain and the buoyancy of the buoy to provide adequate 'give' (as said before, many use chain to attach to the buoy: no stretch there).
2. Use as thick a rope as you can get through the fair-lead and around the cleat. Strength is irrelevant: 12mm polyester will take 2.6 tonnes: more than enough for a 42' boat in a hurricane, but who'd ever use a single strand of 12mm rope for a permanent mooring? It's all about chafe.
 
sarabande said:
Polysteel / disadvantages: less elongation under snatch loads.

Typically, for a boat moored to a single buoy (assume a distance of 5m between the buoy and the cleat on board, for braidline nylon rope, a load of 50% of WLL results in a 20% elastic/visco-elastic extension; thus giving an extension of 1m. (Load figures are for steadily applied load BTW, not for snatch loads experienced under strong tidal and wind conditions).

For polysteel rope, typical figures for the same load (WLL) are IRO 2 to 5% extension. However, for the same load as the braidline, the extension will be <2%, so around 0.1m
Click to expand...
I was looking into floating mooring lines and came across Polysteel with no info on stretch. This old thread has cleared that up, basically no stretch probably other than what any 3 strand braided rope would have due to the braid regardless of material. Would be a shame to discount it as there isn't really any decent floating line with stretch that knots better than polypropylene. Does this Polysteel at least knot well?

That said this description is promising "LIROS Lirolen", have there been advances in polypropylene rope lately? "LIROS 3 Strand Polypropylene Article 01120 - Pliable, floating alternative with a finish/feel very similar to 3 strand nylon and polyester" LIROS 12mm 3 Strand Polypropylene Mooring Warps

Anyone tried this Liros rope? Does it knot ok?
 
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For the mooring strops on our moorings I supply 25mm 8 strand multiplait. Most use 2 strops. One through the fairlead & one slightly longer hanging loose as a spare in case the first breaks. From the shore one can see the loose one hanging down slightly & know all is Ok.
On my yacht I tend never to use the fairleads as these cause rapid wear. I prefer to go from the cleat ( which is mounted on the rail) straight to the buoy or to the pontoon ( I do not to put my cruiser on a mooring very often).
Some use a chain for the principle strop. I did this on my squib mooring but I found that it damaged the gunmetal fairlead, so I went back to 2 No 19mm octoplait strops.
I splice a nylon thimble for the buoy shackle & a large loose loop for the cleat with a 6mm line ( whipped on permanently so it is always to hand) to secure the loop to the cleat to stop it jumping off.
 
I think stretch in a mooring strop is a very bad thing, and indeed chain - which does not stretch - is often used as a mooring strop so stretch is hardly a requirement . Polysteel is an excellent choice if you want a floating line as the strop. On my mooring in Scotland I use 32 mm did 8-plait polysteel (in a natty black and yellow venomous snake effect). But on my mooring in Cornwall I use polyester. Why the difference?

The answer is to do with the design of the buoy and riser. The buoy on the Scottish mooring is a Norfloat one where the riser chain passes through the buoy, and the strop is attached to the top of it, That way a floating strop is ideal as (i) it doesn't need a pick-up buoy (which is always a pita to feed through the pulpit) and (ii) it doesn't get tangled with the riser when one is not on the mooring. Conversely in Cornwall the mooring buoy is just a support and the attachment between riser and strop is under the buoy. In this case (i) a floating rope is no help stopping the strop getting wound around the riser when away from the mooring, so a sinking one which moves around less is better, and (ii) the sinking strop with small pick-up buoy makes it lie closer to the mooring buoy and so less likely to entangle passing boats; in Cornwall there are many more yachts passing than where I have my mooring in Scotland.

In both cases I always splice, never knot the mooring strop as the knots have to be so big they don't get over the bow roller easily and can jam when being picked up in a hurry / high wind. Knots are perfectly acceptable for rope risers 'tho, and many prefer them to splices, but they are big things with locking turns and whippings extending some feet along the standing part.
 
This chart is from the Liros catalogue. Seems like Dyneema will float as well? And their polypropylene if i read this right will knot almost as well as the nylon and has fairly similar stretch before breaking. I'll order some and see how it is.
2021-04-01_232930.jpg
 
jdc said:
On my mooring in Scotland I use 32 mm did 8-plait polysteel. But on my mooring in Cornwall I use polyester. Why the difference?
Click to expand...
I thought you were going to say no UV to worry about in Scotland

The original thread was about buoying but I'm only looking for painters/docklines really so stretch and floating are nice to haves if its not at the expensive of usability. Seems like modern polypropylene rope might be better than it used to be so I'll get some to try
 
I've just made twin polysteel strops to go on my mooring. I used 20mm, so each could pick my boat up as a safe working load. Two strops provides insurance against failure, and will allow me to have one through each fairlead, allowing the anchor to stay on the roller.

Stretch is irrelevant. I had chain before and that was never an issue, so I'm really not bothered. The only concern is chafe, but protection and regular inspection will take care of that. Chafe is one reason I went oversize. I considered hard eyes to the riser, but eventually knotted the rope tightly to a shackle so it'll be the shackle to riser join that moves, rather than the hard eye to shackle. The only problem with splicing is that I don't do it often enough, so I have to learn afresh each time. It is important to keep the strands tightly taped up or sealed, though, as it does seem to be keener on unravelling at the wrong time than polyester or nylon. You need a minimum of seven tucks

The fact that it floats will make picking up the mooring easier - a buoy is an awkward thing to pick up with a boathook, a floating line much less so. It's also WAY cheaper than chain, so even if it only lasts a year or two before I have to replace it, it'll be cheaper in the long run.
 
Something that I do when splicing multi-plait to pull the strands up tight to a thimble is to start all the strands off 2 or 3 plaits each to ensure I have the weave correct. Then I grip each strand in turn with a pair of long nosed pliers & rotate the pliers. This has the effect of "winching" the strand up tight to the thimble , or whatever I am splicing to. With multi-plait I normally go 6 weaves & then finish off with this & it pulls the whole splice up nice & tight before I trim the ends.
Not what professionals might do but works for me & I do sell quite a few.
With polysteel, this may help pull the splice in a little tighter. We tend not to use it as we had a boat go adrift when we used 38mm for a mooring riser & it broke free within the week. A very bad choice for that use.
 
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