Mooring chain

[Avocet]

I just wondered if anyone out there had any advice on the size of mooring chain I need to secure a 3 ton, 27' yacht to a mooring. I have the main chain from the concrete blocks to the bouy and now I have to connect that lot to the boat. I've been told to secure a separate length of chain to the BOTTOM of the buoy and NOT to the ring at the top. I could then do with knowing what size of chain might be appropriate (and how to attach said chain to the buoy).

Any ideas, anyone?

Ta!

 

[longjohnsilver]

Presumably you're talking about the riding chain to your bow cleat, if so something around 3/8 would be about right, this will allow you to attach this by way of a reasonable sized shackle to the ring under the mooring buoy.

 

[VMALLOWS]

I'm in Chichester Hbr, Solent, so info may not be appropriate to Cumbria.

Buoys provided by the hbr conservancy here are generally equiped with 10mm (3/8) chain from a swivell on top of the bouy. (the riser passing through the bouy).

I add a secondary nylon line which takes the strain (to a different cleat) most of the time, and also acts as a snubber.

My boat is 29foot / 4 tons. My concern, in general terms, would be the security/ adequacy of the concrete block mooring..........we lost a lot of boats on those moorings down here during the big storms a few years back. Most are now on ground chains.

 

[Guest]

Check with Harbour Master.

The harbour Master will have recc'd sizes / req'ts for the harbour on request. It will detail the lengths etc. required to ride the tidal range etc. / prevailing weathers etc.

Generally you would be looking at heavy block, well dug in, 3/4 bottom chain at approx. mid tidal difference length, to a swivel, then a 3/8 riser chain same length again to the buoy - preferably passing through the buoy - then I advise NOT a single strop, but a multiple job ........ I used 3 10mm 3 strand rope strops secured to different points on the boat .... #1 to the mooring post / cleat, #2 to the anchor windlass, #3 to the mast base ..... this way you will always know the boat is secure ....
OR the riser chain can be longer by the freeboard and bow length of the boat, with short strops to each point again ... providing chafe resistance by having chain over the bow roller.

You can never be over moored !!! I used 1" bottom and 1/2" riser on my boats .... that was Langstone Hbr, but above 3/8 - 3/4 is good enough for most .....

Nigel ...
Bilge Keelers get up further ! I only came - cos they said there was FREE Guinness !

 

[vyv_cox]

In Menai Strait, strongly tidal and exposed to SW and NE, I always used 1/2 inch pick-up chain connected, as you say, to the riser chain attachment beneath the buoy. The type of buoy that has a rod passing through it can be somewhat unreliable. Attachment beneath the buoy allows for a known connection straight from the weight to the boat and it does give a little spring to the line-up.

For interest, all moorings to my knowledge in the Strait use two large Admiralty pattern anchors connected together with heavy ground chain. Mine was at least one inch but some 1 1/8 and 1 1/4. A swivel in the centre led the 3/4 inch riser chain to the buoy. Even so, the occasional dragging occurs.

All connecting links used by the moorings contractors were welded. Links were made up in mild steel in an overlapping configuration rather like a paperclip. This allows plenty of weld along parallel lengths and means there is no direct pull on the weld. I have seen it suggested that a shackle can be welded closed. You need to be a little careful welding galvanised components as the zinc will embrittle the weld.

My first boat was about the same size as yours and it used the dimensions above. In a more sheltered location I guess that 3/8 inch chain would be adequate.

 

[jleaworthy]

In the Western Isle where conditions can be difficult ALL the HIDB heavy visitors moorings use rope from the buoy to the yacht. After using chain for a number of years I have gone to this arrangement myself. A very suitable rope is Seasteel from Gaelforce (www.gaelforce.net) which is four strand hawser laid, very durable and chafe resistant. I use the largest size I can get through the fairlead. Advantages - kinder on the boat, easier to lift, some elasticity and probably outlasts chain in that difficult surface water environment. Certainly not regretted the change.

 

[Guest]

Correction !

Chain lengths are equal normally to the tide rise and fall ... that is for each section ... allowing sufficient slack to produce a catenary curve from the block to the buoy.
In ideal situation the bottom chain shouldn't lift from the sea-bed providing a snubbing effect on the mooring. In event of serious weather, then the added weight of the bottom chain lifting along with the riser chain helps the block hold ....

In Langstone we used concrete blocks approx. 3ft diameter and about 1ft depth with a 'dished hollow' base face - to promote suction when dug in to a depth of about 1ft into the mud.

Nigel ...
Bilge Keelers get up further ! I only came - cos they said there was FREE Guinness !

 

[Bodach na mara]

Where you are, whatever size of boat, I would not use chain of less than 1/2 inch for the riser, it will corrode within a couple of seasons otherwise. I used 5/8 which lasted for about 5 years, but the local mooring contractor replaced it with 3/4 last year. Rope from the under the buoy to the boat is kindest to the hull.

On the Clyde at Gourock, many of us now use only about 15 feet of chain at the botom of the riser to take the wear on the sea bed, and multiplait rope the rest of the way. This lasts for several years, a change from the days when we used wire rope and had to renew every year.

Ken Johnson

 

[Avocet]

Thanks all!

 

[vyv_cox]

Pick-up chain damage

I agree that the pick-up chain can cause quite a bit of damage to the hull when wind opposes tide. We used rejected fire hose from our local fire station to sheath the chain. There's something comforting about having all chain and welded links as compared with rope, knots and splices. May be illusory but good to know during a good blow.

 

[hylas]

Absolutely..

- The force exerted on a 27' boat is aproximately 635 daN for 45 knots of wind and 1275 daN for 60 knots.
- If for your mooring, you are using a block of concrete it must weight 1115 Kg or (0.446 cubic metre)
- You can attach the chain to the ring at the top of the Buoy IF this ring is "one piece" construction of steel through the buoy.
- For this size of boat, the recommended size of chain is: 8 mm and this size has a breaking strength of 3200 daN. It will be OK
- To attach it use a 10 mm shackle
Fair winds and peaceful anchorages
Alain D'Hylas

 

[Avocet]

OK OK Everyone!

Thanks, I've just realised that I didn't mention the boat was on Windermere at present, so I don't envisage 60 knot winds and there's no tide! I also don't get a choice on the concrete blocks. All the moorings are laid by one of about half a dozen contractors authorised by the lake wardens. All moorings use a concrete block and those for bigger boats use two blocks but I've never actually seen said blocks and have no idea how heavy they are. I asked the contractor to put the second block on mine just to be on the safe side. The only bit I get to choose is the short bit from the bouy to the boat. I put the boat on it yesterday so I'll see how I get on. I went for 3/8" chain and a 12mm shackle in the end and covered the chain with an old mountain bike inner tube.

Thanks again everyone.

 

[yoda]

Inner tube will be all right until it rubs on the hull and leave black marks. Clear plastic tube from B&Q does the trick for me and I suffer from wind over tide a lot. You shouldn't be nearly as bad without tide.

Yoda

 

[jointventureII]

not sure on size, but ours (a 1.25 tonne orkney) has links that are about 8 cm long.
there are some scarily thin looking chains on boats around ours, not because they are rusted but just plain small, i know i wouldnt trust that thickness for the size of boat.

JVII