Pontoon chains - lifespan?

[Alan ashore]

(moved here from scuttlebut)

I'd particularly like to hear from people in the Hamble, but reports from elsewhere will also be helpful.
If you have a pontoon secured between piles by chains, how often do you replace (or expect to have to replace) those chains? It would be good to know what gauge of chain you have, and any other info which you might think relevant to the life of the chain.

For those in the Hamble, cognisant of the perception that there may be some galvanic "hotspots" along the river, whereabouts are you?
Grateful for any and all contributions,
A.

 

[npf1]

I was on L for 11 years. Chains replaced 3 times in that period. The first time changed was with heavy gauge galvanised chain - lasted about 5 or 6 years IIRC. The second time was same heavy guage, but not galvanised - lasted 3 or 4. The last lot was much a lighter gauge and, when I left the mooring last year, the chain was less than 12 months old and clearly wasn't going to make 3 years. Each lot was fitted by a local contractor but I didn't specify what type of chain to use - just asked them to 'do the chains please'.

As per usual in such an environment, going with cheaper raw materials looks to be a false economy for the customer, and a job creation scheme for the contractor (and if I was the contractor, I'd do exactly the same!).

 

[Derm]

I suggest you contact Tucker and Munday or Mike Lindell at the Hamble Warsash Ferry, The Ferry Hard by Hamble River Sailing Club. They are two of the mooring contractors on the river and will no doubt have the answers. I think that chains need replacing when they are half worn through. As for 'hot spots', I have no idea about this but it may prove useful if we can get some information.

 

[Alan ashore]

Thanks very much for those answers. I was anxious to get some data based on members experience, before talking to contractors.

I've recently taken over a pontoon mooring near Mercury, and it's clear that regular chain replacement will be a significant cost.

I part own a pontoon elsewhere which has rigid guides around the piles, and which has required no maintenance whatsoever in over 30 years.

Can't help wondering what, if anything, is good about the chains solution!

 

[William_H]

I imagine the chains you ask about are a similar problem to a swing mooring. The chains wear where one link rubs on the next. The normally protective rust gets worn away quickly so they wear quickly.
If the cost of installation of high compared to the cost of the chain you might consider stainless steel chain.
If the cost of the chain itself is the major cost then consider old chain. Essentially it is the amount of meat in the chain (that is left) ie cross section of link at the wear point, that determines the life. So a heavy half worn chain will last as long as lighter new chain. I don't believe galvanising makes any difference as it wears away pdq. good luck olewill

 

[Alan ashore]

Olewill, Stainless is specifically outlawed here, but it does seem to me that rusting plain and simple is at least as big a factor as wear. Either way, it does seem surprising that the accepted (indeed mandated) method of securing these pontoons is so sacrificial.

Is this something which has in fact been optimised over the years? Or are there much better methods and or materials which could be used?

 

[rob2]

Quite right, the Harbour Master prohibits the use of stainless on any part of the mooring and it makes sense as it would do terrible things to the risers on the piles and accelerate corrosion and loss of galvanising within line of sight. Chances are if your chains are wearing, then so will the eyebolt on the pontoon. During a brief sojourn on such a mooring I noticed that the corrosion and wear was at its worst by far in the last few links of the chaim by the said eyebolt, which I attributed to the aerated surface layer of the water and the splash zone. Any mettalurgists who would like to comment on the likely longevity of different grades of chain? I suspect the contractors just use the cheapest they can get which could well be Chinese grade 30 - OK for occasional anchoring, but not so hot for continuous duty holding a pontoon in position! As already suggested it may prove cost effective to use a larger size, but maybe a higher grade would also offer improvements?

Of course, if you came up with a better material you'd have to get it approved by the Harbour Master and your insurers!

Rob.

 

[savageseadog]

Olewill, Stainless is specifically outlawed here, but it does seem to me that rusting plain and simple is at least as big a factor as wear. Either way, it does seem surprising that the accepted (indeed mandated) method of securing these pontoons is so sacrificial.

Is this something which has in fact been optimised over the years? Or are there much better methods and or materials which could be used?

I've seen rope used for mooring marina pontoons, not 12mm polyester of course but something like 50mm(?) with eye splices. There's no rust or wear and there's a useful amount of elesticity.

 

[Neeves]

Galvanising is more wear resistant than the steel. Once you get through the outer and shiny zinc layer the Fe/Zn alloys are harder. Unfortunately they are not very thick - so their hardness is a bit academic. But even when worn through the adjacent and remain gal will protect the steel nearby. A G40 chain should last longer than a G30, the higher the number the harder and more abrasion resistant. But you cannot beat more steel - so go for bigger links.

'Second hand' chain is a good idea. Mooring chains wear where one link rubs another, some mining chain wears where it is dragged along the ground - so the 2 applications have a different wear pattern. I confess I have no idea how you source second hand chain that will be of any value (Here its easy - lots of mines).

You might consider - have new chain attached, as good as you can get, but then double up with heavy duty cordage, such that the cordage takes the load. You then minimise wear on the chains but have the chain to meet whatever local requirements are in place.

Jonathan

 

[GrahamM376]

I've seen rope used for mooring marina pontoons, not 12mm polyester of course but something like 50mm(?) with eye splices. There's no rust or wear and there's a useful amount of elesticity.

Our local small boat marina has found that polysteel rope outlasts chain on the pontoons and it's replaced chain risers on most moorings. Far cheaper as well.

 

[Alan ashore]

Our local small boat marina has found that polysteel rope outlasts chain on the pontoons and it's replaced chain risers on most moorings. Far cheaper as well.

That is interesting,
I imagine someone has probably been around the loop of discussing alternatives with the HM, and it may be that there are very good reasons why steel chain is presently the only approach allowed. But it must be worth the discussion.
GrahamM376 are you able to post a link please to any further details on the material your marina has used?

 

[GrahamM376]

That is interesting,
I imagine someone has probably been around the loop of discussing alternatives with the HM, and it may be that there are very good reasons why steel chain is presently the only approach allowed. But it must be worth the discussion.
GrahamM376 are you able to post a link please to any further details on the material your marina has used?

I'm at home at the moment and won't be back in Faro until early January so can't speak to staff there at the moment. My information came from the guy I bought my mooring from some years ago who is also involved with marina maintenance, when I queried the use of a polyprop riser and strops. He said it had proved longer lasting and less failures than chain and that they had replaced some of the chains in the marina with rope.

I replaced my riser when approximately 10 years old through nervousness rather than seeing any wear problems and replaced with 36mm octoplait polysteel. Way over strength spec (21000kgs) for my boat but allows for many years of wear. Shackles of course still need replacing but in theory may last longer as not so much weight hanging on them. Whether the pontoons move more without the catenary weight of chain, I don't know.

 

[rob2]

I suspect that the main reason Hamble HM insists on chain is that your annual condition report , giving the actual remaining diameter of key points is a meaningful exercise and limits may be set. A condition report on rope is so much more subjective and his staff would have to do the inspection to prevent "optimistic" assessments. How often have we watched a rope break as the owner tells us it has years of life left in it? In a marina, serviced by its own staff the responsibility lies with them and they will replace suspect lines to avoid liability for breakages.

Rob.