concrete anchor

[markpsymons]

I have read that it is possible to make your own concrete mooring anchor for a permanent mooring.I believe that a weight of about 50lbs for each Ton of boat will do the trick.Also the weight needs to have a concave base.Apparently this gives better grip on the bottom.I am looking at mooring in Southampton Water near the Royal Victoria Country Park which is a lee shore,so what ever I do it had better be strong!

 

[hlb]

I think some one said. That concrete did not weigh very much under water. cos of air bubbles I suspect. Better with something like a big old engine or machine.

<font color=blue> Haydn

 

[Reap]

Found this:

Another advantage is that you can design the concrete block to be whatever size (and weight) you desire. We found that concrete weights approximately 150 lbs per cubic foot while water weighs 62.4 lbs. The difference is 87 lbs. (The difference is important because the concrete block displaces more water thus requiring more weight. The difference shows us how much we are gaining after you take into consideration the loss of further displacement). By designing a block of a predetermined cubic size, we can closely predict how much it will weigh and how big it needs to be

 

[Trevethan]

seen permanent moorings made of a number of tractor tyres (5 I think) , filled with concrete, placed in a ring with chains linked to a single riser. Seemed very effective, especially in mud where they bury themselves so in addition to mass of concrete you have the added effect of lots of muck sticking them down

She had a deep, throaty, genuine laugh, like the sound a dog makes just before it throws up

 

[graham]

It all depends on the bottom .If its soft mud You can reduce the weight compared with a hard bottom .Also depends how exposed it is.

Lots of people use concrete filled tyres.Or oil drums cut in half lengthways.

Complete oil drums not so good due to the round shape making them slide up out of the mud under extreme load.

Presuming there are other moorings nearby ask what everyone else uses.If no other moorings you have to wonder why not?

 

[steveh]

I made one once from a large tractor tyre. Filled it with a broken cast iron bath, laid a very large riser chain in it and then filled with concrete. Made it at low water and then floated it into place!

 

[gjeffery]

Concrete mooring clumps are traditional. I have collected a number of old sailing books, many from the 20's, 30's and 40's. One book - can't remember which offhand - shows the DIY construction of mooring clumps. Through ring bolt is made by blacksmith and set in a wooden shutter that is filled with concrete. The clump has a rectangular base and the cross sections are also rectangular. The leading edge is cut down, from the middle of the top of the clump, so that the clump is wedge shaped; presumably to help it dig in.

The clumps are cast on the hard at low water, and are floated into posiution slung between two boats.

If anyone is at all interested I will try to find the reference.

 

[bigmart]

Very often the Harbour Master will have a specification for moorings that are laid in areas under his juristiction. He doesn't want boats drifting all over his patch every time the wind gets up a little does he.

I laid my own block in Langstone a few years ago. From memory it was about 4 ft in diameter & around 15 inches deep. I cast some lengths of concrete reinforcing rod, which were passed through, the biggest shackle I could find for the attachment loop.

The weight was cast at home in former made of hardboard where it was left for a week to harden. I cast it in a trailer, which I then towed down to the shore, shoved the weight out the back of the trailer, then attached it between 2 dinghys, which were lashed together to form a rigid catamaran, at low water. as the tide came in the boats complete with weight floated, were rowed out to the desired site & the lashing cut. It is of course important to make sure that you have a suitable chain attached at this point, or all your work will be to no avail.

I would confess to being quite frightened of the whole operation, which actually turned out to be, much easier than anticipated. As with all these things its all in the planning.

This all held a 24ft boat through some horrendous blows which saw many other boats resting high on the shore.

Good Luck

Martin

 

[Opinionated]

Well, pity Nige not posting here so much these days, as he would explain to you that you do not need anything other than chain. No mooring, no anchor. (Noises of laughter off-stage....).

(I don't have to agree with YOUR opinions, but I'll defend your right to express them).

 

[dickh]

Here at Felixstowe Ferry, the boatyard casts concrete blocks about 4' 6" square and 1' thick with a large loop in the middle. very few boats go adrift.

dickh
I'd rather be sailing... /forums/images/icons/smile.gif

 

[markpsymons]

Re: concrete anchor (thanks)

Well thankyou for your replies.I was struggling how to get the damn great lump from home to the club.Well stap me! All I have to do is build it at the club!!Thanks again.
Mark

 

[mtb]

Ask about other local moorings and how they coped in the last storm, then I'd add a third more in volume than you think will do and dig it in if possible .

Cheers
Mick



smile you'l be on your boat soon ;-)
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