Laying a mooring

Allan

Allan

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I may have the chance to lay a mooring for my W33, Chausey and wonder if anyone has any experience of DIY moorings. I plan to use a combination of concrete and ground chain to make up the weight. The moorings are tidal but have little tidal flow, they can suffer from some swell. The main question is how much weight do I need to use? The boat weighs between 7 and 8 tons.
Allan
 
We did one (fore and aft) a few years back, 45 gallon oil drum cut in half, filled with concrete and a very large length of 1 inch chain with the last link sticking out.

Buried them into the mud at low tide, workrd well, no tide but a lot of windage (Catalac 9m)
 
We used van tyres filled with concrete with a heavy chain embedded plus a heavy iron bar runnng acroos the tyre, through the concrete and last links
Two blocks, laid across the channel, connected by heavy chain (1" I think) and then a 1/2" riser from the centre.

However check your insurance - ours specifies that the mooring must be professionally laid and maintained.
 
You don't mention what sort of sea bed you have where you plan to put your mooring.
Have in the past laid several moorings into mud. and never had much luck with concrete as a weight. The concrete in drums has a tendency due to the shape of getting scoured out and then going for a trip round, once pulled 2 forty gallon drums of concrete out with a 25ft boat and a 40hp inboard engine.
Much prefer anchors or heavy lumps of scrap iron ie old engines. One point to remember is to some how mark where you set or bury your anchors. Looking for a buried anchor when the mooring needs maintenance is not much fun.
 
The bottom is mud. I plan to have one weight with a one and a half inch ground chain. I then plan a chain riser. The mooring will be dived on once a year to make sure it is in good condition. What I am really after is an idea of how much weight I need to use?
Allan
 
At our club we now tend to use old scrap railway wheels which could be obtained from a merchant i Glasgow. This was preferable to concrete because of the density being greater, they sank into the mud faster and stayed there. As the OP seems to be in South Wales do they still have the old railway scrapyard in Barry, should be a source for some decent size wheels.
 
I will look into using scrap metal, what I need to know is how much to use? The weights will be lifted with airbags so I may need to have a number of smaller weights linked together.
Allan
 
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http://www.divingbelle.co.uk/

This contractor in Plymouth has some spec's on his site which might be useful guidance for weight. You need to allow for the buoyancy of the concrete i.e. effective weight is reduced by about 40% for concrete.
Some say it's not the weight of the block, it's the weight of the suction/mud that matters, hence disc shaped or flattish sinkers are preferred.
Drum shaped can sometimes roll around on the bottom, even if buried in mud.
HTH?
 
I am moored in the Medway (Mudway). I have two anchors, one each end of a chunky ground chain. the riser is shackled to the ground chain on top of which is the bouy. I dont have any problems with dragging. The flukes of the anchor can dig in very well into the mud.

If all that makes any sense. My boat is a 28' wooden sloop displacing 5 tons.
 
Laying a Mooring

My Admiralty Manual of Seamanship (1937) describes a mooring as two anchors laid opposing oneanother in line with the direction of the prevailing wind with a swivel midway between them connected to a riser to which the pickup buoy is attached.

Not knowing any different my mooring is 2 big Danforth anchors, well dug in. My mooring buoy has its own swivel so I didn't bother with the swivel at the bottom of the riser. It seems to have worked very well for many years.

Judging by the way I sometimes get brought up all standing when I am a bit late for the tide, others use loco wheels but I like to think mine is the better system.
 
go to a place that sells mooring stuff (eg fpm henderson, glasgow as above) and speak to them. yellow pages etc. somewhere more local to bristol will know your intended mooring spot.

for mud admiralty suggest 2 mushrooms with a riser between, thats what we use.

we leave boat in for winter, so not keen on concrete block.

in water steel weighs 0.9 X weight, concrete 0.7 X weight, so "lose" a fair bit with concrete.

train wheels have no stock so can also move in a gale. you used to be able to get them with axles, not seen any for a while, even at above mooring place.
 
Our mooring (for a 35' yacht) simply has two 40 lb anchors on the bottom - they have been there for the past 11 years, and they work very well.
Ideally it would be better if they were bigger, but that was all that was available at the time.....
If you are thinking about using weights from a cost point of view instead of anchors, you might find that the overall cost of acquiring and laying a pair of (say) 80 lb anchors might still be less than the all inclusive cost of using a mooring barge to lay a couple of (say) half tonne blocks - and in terms of holding power an 80 lb anchor will generally have far more holding power than a big lump of steel or concrete.
 
lw395 said:
Please elaborate. Why is concrete no good in winter?
Cheers!
Click to expand...

cos a 1 ton block is only "worth" 600-700kg underwater, our boat is 3 tons, and some others have moved in the bay on concrete blocks... tayvallich, sheltered for all except easterly gale, when waves do come in. but for the 30 years or so we been there, concrete would be ok for the summer.

as per above also, probably cheaper getting two anchors of your choice and laying them, and far easier to handle from your own boat.

we also have doubled the riser, so we can rotate it, cos almost all of the corrosion is in the top few feet, so easy to change riser. but not all anchorages will be like this.
 
My Moody 33 has two concrete blocks, from memory about 4' square x 12" thick with a heavy ship size mooring chain concreted into the centre, joined with similar size chain with a chain riser to a mooring buoy and then 1" strop on top. Supplied and laid and maintained by my local boatyard.
 
The density of concrete ~2500kg / m3. Density of steel ~7500kg / m3.
Density of water ~1000kg / m3

The density gradient between steel and water is 3 times that of concrete:water. As concrete has almost the same density as mud, this difference increases dramatically when the sinker is buried. Shape and surface area play a big role but a steel sinker is much better, other things being equal.
 
Lay the biggest gear yiou can lay your hands on or afford. That way you will sleep well when there is a gale.

My 40' lugger, weighing about 17 tons has TWO 1 ton Admiralty stockless anchors, joined by 65' of 2" chain, with a 3/4" riser. All chain is stud link. In soft mud.

I sleep VERY well !
 
Laying mooring

As suggested a suitable weight of concrete can be expensive to get to the site and into location. Further if it is a drying mooring there is the risk of your boat sitting on the concrete so holing the boat.
Anchors obviously have a great holding power for their weight. A form of one fluke fishermans anchor (admiralty pattern) can be made out of scrap steel. These are fitted at each end of the joining chain.
If in doubt add more joining chain and more anchors at right angles to the primary joining chain. If it is drying the mooring mass or anchors need to be far enough away from where the boat can settle.

All metal, especially chain should be as heavy as you can find as more metal equals longer life as it rusts.
Ultimately much depends on what you can find s/h in junk yards. The ideal gear would be far too expensive to buy new especially chain.

It is the usual habit to service moorings around here by diver rather than raise the lot for inspection. So this in itself means mooring barges for lift are not available. You need to consider maintenance in the long term.
good lcuk olewill
 
Laying or Digging?

Down on the Thames Estuary where most of the moorings are drying half-tide ones, they have to be dug in; ie you walk out with a spade, fork and bucket and physically sink your root into the self-dug hole. You really wouldn't want your loved one clouting a concrete block as it swings at low water. If it's deep enough (at least 3 feet) you can get away with a hard wood cross 3ft x 3ft with the ground chain shackled round the middle. You need friends to help dig, insert and fill in between tides! Once filled in, the Essex mud preserves chain, wood and shackle. On my mooring, the ground chain is unworn, only the riser (13metres long) of 1/2" chain is showing signs of wear and as stated above, only near the top end. Length will obviously depend on tidal range.
The only local moorings that are laid are the deep water ones in the Ray Gut off Southend that never dry and they use old anchors and very heavy chain. They have to be inspected by divers.
Whatever you decide, go for the biggest chain you can afford. The weight of the riding chain will help to stop the snatching you get in rough weather and give less vertical pull on the root and ground chain.
If you do decide to dig a mooring, you will find out who your true friends are!

Alan
 
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