Permanent mooring anchors... ballpark figures needed

Kelpie

Kelpie

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As a bit of a thought exercise, I'm pricing up ground tackle for a permanent mooring. I like the idea of using anchors rather than deadweights. I'm looking at various Danforth copies of 20-30kg which are pretty cheap. In a soft bottom you'd think this would give plenty of holding power (for a 2.5t, 27ft yacht) but I know some people rely on hundreds of kilos of concrete and/or iron which makes a couple of 30kg anchors seem a bit puny...
So, for a moderately exposed mooring, soft bottom, what sort of holding power would I need? A pair of 20kg? Four at 30kg? etc.

Cheers

Rob
 
Having had a little experience in laying moorings. I wouldn't think you need a proprietary anchor, we use custom made jobs, rigid construction basically stock, spade and bar. Since they are only positioned once they can be pretty simple and weighty.
 
Twister_Ken said:
Why not use for-purpose mooring anchors. Cheaper too.
Click to expand...

Well, about the same price as an eBay danforth type, thanks for the link, maybe a better choice?
Question remains, how many of these things would I be looking at? I know it's a bit of a 'how long is a piece of string' but given the local conditions, size of boat etc, do I need hundreds of kilos of anchor or just a couple of 30kg ones?
Is it, in general, better to lay a four-point system with, say, 20kg anchors, or a two-point with 40kg ones? It seems you tend to pay per kilo for anchors.
 
Several years ago I helped to construct some sinkers for a mooring that were moulded concrete blocks in a butlers' sink,with a 1" chain link as the tackle fixing, protruding from the top. The underside of the block was formed as a dome ,for suction purposes in the softish mud. I reckon the blocks must have weighed about100lbs,they weighed the dinghy down for sure each time. The sink was well greased beforehand to enable it to be tipped out as a mould. I haven't seen the friend for years but the mooring site is still in use and easily inspected for wear at low water springs.

ianat182
 
Thanks Ken, that is a really excellent booklet. The appendix seems to answer my question: two anchors of 15-21kg depending on type (can't find out what a 'Bradney Pattern' is) plus ground chain of 12.5mm.
I had actually envisaged using either four 20kg or two 30kg Danforths, plus at least 16mm ground chain, so looks like I have been rather cautious. Which is a good thing.
 
UThanks, just spotted it! Mooring anchors seem to follow the same sort of pattern, however they only tend to be available in larger sizes, from about £100/anchor upwards. Whereas the Danforth copies are available from about half that price. Hmmm.
 
Those "mooring anchors" look a bit flimsy to me. I had a local blacksmith make up 2 Rond (not sure of spelling) anchors. These were made up with 2inch x 4ft mild steel bar bent over 225 degrees with the end flattened slightly to allow a single triangular 1/2" plate (fluke) to be welded on. The flukes were equilateral triangles about 10" sides. The other end of the shank was also flattened to about 1" and a hole drilled for the shackle. They were then hot dip galvanised. The two anchors were laid about 50ft apart in sand with up/downstream orientation and connected by heavy galvanised chain. A similar heavy chain riser was taken from the centre point of the chain up to the buoy. A stainless swivel was connected to the top of the chain then onto a permanently rigged pick up strop with its own small buoy. The heavy anchors progressively sank into the sand and the mooring proved to be rock solid. On one occasion holding in 100mph winds when the shore was littered with yachts that had come adrift. I forget the cost but I do remember it was a fraction of the cost of ready made gear and was a lot more robust.
 
All sounds very light to me. My mooring on Menai Strait, fairly exposed to SW and NE, tides up to about 4 knots, had as follows: Two Admiralty pattern anchors about 100 lbs, one laid upstream, one downstream. 3/4 inch ground chain between them, don't remember the length but maybe 30 metres. 3/4 inch riser chain to the buoy, 1/2 inch pickup chain. I originally had a 27 ft boat on it, then 29, then 34 ft. Looking at mooring gear stored over winter by local contractors shows mine to be fairly typical, although plenty heavier. Not much lighter.

12.5 mm ground chain and riser might give you one season in Menai Strait conditions. 20 kg anchors - I wouldn't like to trust any as light as this. Mud anchors I have seen for quite small craft were plate type, made in about 1/2 inch steel and probably 3 ft square. Considerably heavier than 20 kg.
 
A friend in our club has had a lot of trouble with mooring anchors. It's harder than you would think to get them laid properly on an all tide mooring. If the boat is allowed to pull across a chain between two anchors, it will pull the chain sideways until there is a lot of slack in the ground chain. Then everything starts stirring around and wearing.
Ideally you get 3 anchors at 120degrees each or four at 90 degrees and get all the ground chains tight, so the riser and boat swivels around a fixed point.
If the anchors dig in they are hard to inspect or lift.
It depends on whether you expect to inspect and maintain by diver or barge, and on the nature of the bottom.
If you have access to a man with a suitable barge, laying a very heavy block is very cheap in terms of man hours, whereas paying someone to fine tune 4 anchors racks up.
However if there is no barge, anchors can be done DIY.

Different moorings work in different places!
 
Gael force are not too far away, and make a big range of mooring anchors for boats or fish farms. Worth looking at their website/catalogue.
 
Rob- the best advise, which covers any mooring area in the UK, is to ask the local yacht owners what they use. Being generally tight, they will know how little you will get away with respect to the ground conditions and exposure where you intend to moor, and how long it will last before needing renewal.
 
fisherman type are the best. I have laid many mooring, using lots of different types of sinkers, these are the best, in my view.

I also know where you can get them cheap too. 30kg for about £70 each.

Good value, I think.

let me know if you want the details, via private message.
 
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