Swivel for mooring buoy

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Conrad

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I need to get hold of a shackle and swivel for mooring my boat to a buoy in a tidal estuary, my boat is a 27ft long keel, any thoughts on what tonnage rating I should be using and where to get hold of one.
Just spent half an hour yesterday untangling wond up lines so definately needed.
 
The swivel you want will be the one the shackle pin can go through without too much slack or bind. If you are using something like 3/4 ground and 3/8 riser ... you will have more than enough margin in a swivel for connection to 3/4, as the 3/8 size will not allow a decent shackle pin for 3/4 side.

One tip - do not use bow shackles, only correct size D shackles. Over size shackles can in fact be bad idea, proper size to match chain / swivel.
 
I found it best to use a swivel between the boat and the buoy, that way the swivel coud be kept out of the water, greased and inspected. Nothing else seemed to work very well as my boat always rotated the same way, once per tide.
I used a stainless one, but it was electrically isolated from the mooring, and out of the water except when the boat was off the mooring. Hence no galvanic/electrolysis issues. The swivel on the bottom of the buoy was always in good order but never seemed to prevent the strop winding up on its own.
Hope that helps?
 
I would advise strongly against stainless anywhere in a mooring. Stainless gives no warning of failure.

Best materials are all of one type : galvanized or black iron - but not mixed.

You can see the corrosion and wasting of the metal giving you excellent visual signs of time to change.

Black iron in fact will often coat and survive longer in mud moorings than other.

Well that's my experience anyway. Plus HM's where I moored all specified mooring material, sizes, lengths etc. to be used. - Langstone, Chichester, Havant, ......
 
I think Chichester now use stainless shackles (and swivel?) above the buoy. I think they got fed up with the rubbish they were getting as galvanised. Not studied them carefully mind as my mooring is a yard one. We dont have swivels and seem to get away without, awful lot of twists in the chain sometimes though.
 
maybe ... 2 yrs since last moored their. I have the old LH / CH HM mooring specs, but admittedly may be out of date.

To anyone about to set a mooring - I always advise - talk to HM first as he will usually have a minimum spec you must meet. It's usually him who has to 'pick up the pieces' of what we term "Bike Chain" moorings where people think they can get away with ....

I've also been involved in Ins. claims ref. break-aways. All bar 1 was due to boat owner failing to observe good practice.
 
I agree stainless should not be used.
Stainless is too brittle and can fracture under snatch load.
cold winter water, Sharp chop and it will fail.

I thought galvanised steel was specified by most harbour authorities, I would be surprised to find Chichester using stainless and i expect issues sooner or later with them.

This was a boat in Langston (adjoins Chichester) last year stainless was used against HMs recommendation, the boat broke free , was dragged under a bridge and got washed ashore.
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It is not necessary to have a galvanised swivel or shackle on moorings, plain mild steel is fine but stainless steel is a definite no no. The weak point on swivels is the bearing pin part and that could be at risk from crevice corrosion if made from stainless.

Every mooring MUST have a swivel or the chain can become twisted enough to even hold down the bow of the boat. However some moorings are laid with a swivel at the join with the ground chain(s) so would be unseen. I was involved for many years in laying club moorings either single boat ones in deep water or long trot moorings for up to 6 boats in a row, we always put the swivel at the top end of the riser chain, with the lower end of the riser double shackled to the ground chain. The swivel should be much larger than the riser chain not the same diameter - big is good! The swivel is better at the top of the riser because it helps keep it out of the sand/mud on the bottom which is abrasive, however it should not be above the water either as that encourages corrosion. The 'riser' is heavy chain up from even heavier ground chain between two or more anchors or sinkers and the chain strop from it to on board the boat should also be about one size up from the normal anchor chain. So in this case the swivel is between the riser and the chain strop, the strop being long enough not to raise the swivel above the water under load. A support buoy if used should be shackled to the swivel and I prefer a plain one so that the strop comes off the swivel not from a ring on the support buoy.

I always greased the shackles on my own personal mooring from riser upwards so as to aid maintenance but I always made sure they were double moused with hefty fence wire, I never had one loosen in 25 years. In our case the boat owners were responsible for the strops above the swivel and the club for everything up to and including the swivel. On the lower ends and ground chains shackles were not greased and if possible even had an extra (slack) chain doubling over the join using old but serviceable riser chain cut up for the job. We never had a mooring fail due to the club parts.
 
As Nosey said, big is good, the swivel is there to prevent the riser twisting, which could result in the riser locking up into a rigid column with the leverage of the boat being sufficient to snap it as it twists about in the wind and tide, ie a 30 or 40 foot lever!!! Can't see the point of a swivel in the mooring strop from buoy to boat whether stainless or otherwise.
 
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Can't see the point of a swivel in the mooring strop from buoy to boat whether stainless or otherwise.

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my mooring was a rod buoy, chain on bottom to seabed, very short strop so that buoy is hauled up under boat, so swivel is not far off vertical, as is the buoy. The boat pivots on the swivel, even if the buoy dos not rotate.
Even with longer strops on our mooring, you see doubled up strops tightly wound up or a single rope strop unlaying itself, so the twisting does translate into the strop.
I appreciate all moorings vary, it's always worth looking for local knowledge as it may be the most relevant.
Be aware that its a single point failure waiting to happen so it must be up to the task and inspected often enough.
Most moorings are not so horribly prone to winding up as ours, and if you leave the boat there for 3 weeks in the winter that's 40 turns.
hope that helps clarify a bit. Not saying its the only way but its what I settled on after about 3 years of hassle, then got 4 years of much improved action from it.
I guess if you don't see the point, it may well be you don't get the strop winding up, so for you there is no point?
Cheers.
 
There seems to be a slight term difference here ...

On Langstone mooring specs for drying tidal swinging when I was there :

large concrete or similar sinker. Galvanized bar keeper to galvanized ground chain of 3/4 and approx. 13ft long. Then galvanized swivel joining the ground chain to 13ft of 3/8 galvanized riser chain. At top of riser was the main buoy and rope strops = to freeboard + enough to moor on suitable hard point on boat.

Here the riser is clearly the final chain with no other after it. In your description I get idea you have a third chain ?

Using Langstones spec's - the length of each section is equal to spring tide rise. Such that riser would be lifted and ground chain normally stays down apart from any catenary effect. This allows a very good cushioning of any snatch loads.

As a surveyor and ex shipping deck-officer - it was always impressed on me from days of cadet and on - that correct size for the job. No oversizing or undersizing.

FWIW ... my Langstone morring was 1" ground onto sinker, with 1/2" riser and 3 strops to separate mooring points. That mooring was taken up by another after I left and was in use for years after. All galvanized. Was a right b*****d to lift to make fast - but boat never went walking !
 
It has been 14 years now since I worked on moorings so my memory may let me down!

However we never used sinkers in Poole but heavy (120lb I think) Danforth style anchors that initially we had made for us but later were made by a club member on site. For a single mooring we laid heavy ground chain between two such anchors and this chain was really heavy, either ex Sandbanks Ferry stuff or retired mining chain bought secondhand, link thickness an inch diameter or more. This chain was laid taught between the two anchors up/down tide by pulling them in using a mooring barge with a heavy windlass towed by a diesel launch. The length between the anchors depended on depth and to be honest I forget now. The riser chain was shackled to the centre of the ground chain and usually we then shackled a doubler chain also between the ground chain and riser as a backup. The riser was long enough to give about 3:1 scope and was 5/8" chain I think and a heavy swivel maybe 3/4" attached to the upper end. From there it was the owners responsibility to attach his/her own strop(s) or chain to on board the boat and if necessary a buoy to support the weight of the ground chain. On shallow moorings most just used a small pickup buoy and no big buoy because the support wasn't required, on deeper ones the owner added a big buoy as well. In my case I used the big pink fender or lobster pot marker buoys as a support shackled above the swivel with chain strops coming from there too (below the buoy, not one of those through buoy things).

We also had 'trot'moorings, especially for the drying moorings, which used similar ground chain between end anchors but much longer for up to 6 risers, but in this case there were also additional side chains each out to another anchor, maybe 3 such side chains each side of the ground chain.

All moorings were lifted, inspected on the barge and relaid annually by 'mooring parties' of members who were required to do one weekend on the barge every winter, in teams of 6 including the team leader of which I was one of several. Because we were working on our own or friends moorings we were probably doubly conscientous workers and applied the 'if in doubt throw it out' principle very vigorously!

You will appreciate these were heavy duty moorings exposed to the prevailing winds and with open fetch across the widest part of Poole Harbour. We used a very substantial club made mooring barge with a very heavy cast iron double handled windlass which nowadays has been replaced by a diesel engined one - wimps! The barge was towed by a diesel open launch with a prop sized for maximum grunt to pull in and straighten heavy chain and set anchors. Fortunately my days of doing it were back pre HSE because on a cold January weekend with a numb brain the barge could be a dodgy place, I have no idea how they get round it these days.
 
With the demise of the mining industry, it may not be relevent now, but I would be very wary about using "retired mining chain, bought secondhand". This stuff tended to be high tensile chain with a high carbon content, and who knows what other alloys combined. I know from bitter personal experience that it has a tendency to fail in salt water. It may look perfect on the outside, but inside it goes like a Crunchie Bar, and has just as much strength. Use only mild steel chain, either galvanised, or black.
 
You might be right about the mine chain composition but I may be remembering the source wrongly anyway as I wasn't involved in buying it, but I do know a lot of chain was from the Sandbanks chain ferry. Most of what we used was really heavy stuff, often with a bar across each link as well as being an inch or more thick. It seemed to survive corrosion free for many years having spent it's life buried in the black mud of Poole but this is the ground chain I'm referring to and not the riser chain which was always brand new stuff bought for the job.
 
[ QUOTE ]
With the demise of the mining industry, it may not be relevent now, but I would be very wary about using "retired mining chain, bought secondhand". This stuff tended to be high tensile chain with a high carbon content, and who knows what other alloys combined. I know from bitter personal experience that it has a tendency to fail in salt water. It may look perfect on the outside, but inside it goes like a Crunchie Bar, and has just as much strength. Use only mild steel chain, either galvanised, or black.

[/ QUOTE ]

For ground chain we had 2 excellent sources Chichester and Langstone - Kemps Quay Dredger base - they rotated chain of the dredgers and you could buy any length you wanted. Second for smaller sizes was Belsize Marine Scrap Yard ... sadly closed ...

So all was marine professional stuff.
 
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