Lift mooring chain

Rhylsailer99

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My mooring ring is buried and I was thinking to attach a big buoy low down to lift the chain. Would this lift the mooring ring and expose the ground chains as I really do not want to dig them out.
 

shanemax

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Is there no small floating barge with a winch on it to lift the ground tackle. Most clubs, marinas and boat yards have one for laying and inspecting the moorings, You normally see them moored up, usually rusty, and needing a tin of white paint thrown over them as they are a hazard at night.
 

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My mooring ring is buried and I was thinking to attach a big buoy low down to lift the chain. Would this lift the mooring ring and expose the ground chains as I really do not want to dig them out.
Depends on a few factors:-
Weight to be lifted
How much slack you can get out of the chain to start with
Rise of tide
Size of buoy
Only you can answer that & the best way to do that is try it. We are not clairvoyant.
 

pete

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If it's tidal and you own a boat wait until low water, rig a strong rope from the ring to your boat, remove the slack but make sure you can pay it off if your boat doesn't start to lift when the tide rises.
I did this on my mooring with a Leisure 23, trying to lift the ground chain (not a riser), it didn't work but it provided entertainment to boats leaving the near by dock :)
 

Minerva

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If it's tidal and you own a boat wait until low water, rig a strong rope from the ring to your boat, remove the slack but make sure you can pay it off if your boat doesn't start to lift when the tide rises.
I did this on my mooring with a Leisure 23, trying to lift the ground chain (not a riser), it didn't work but it provided entertainment to boats leaving the near by dock :)
Did your boat start to do a headstand? A fine party trick!
 

Refueler

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My Sunrider 25 ... I've lifted chains with concrete sinkers ... I've laid same ...

Laying ... placed boat over on slipway and let boat settle with low tide .. make fast with double strops either side of foredeck ... let tide lift boat and sinker ... motor to position ... when letting sinker go - make sure EVERYONE is holding on !!

Lifting from mooring position .. boat used to get alarming bow down angle - then WHAM - sinker would lift and again - make sure everyone is holding on !! Its best to dig round the sinker before doing the lift to at least help break suction.

If as OP wants to do - lift only the chain ... any reasonable boat could do that .. in the distant past - we used to use two dinghys with wood 2 beams across - creating a catamaran with open area between .....

What people tend to forget is that the chain and sinkers 'weigh less' in the water ...
 

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The trouble with raising is that one has to be able to manually lift all the riser chain soit is tight between sinker & vessel. That can be very heavy & there could be a lot of slack, so one does not get a full lift with the tide.
As well as that we have max 5 M of tide rise. However, if the sinker is in 6 M of water we end up only raising it about 3M. That means that the sinker hits the bottom at the 3 metre contour.A typical yacht would struggle to carry it towards the shore. So we use an air bag & my launch. Then when it gets to the contour line & the tide goes out one finds that one has to repeat the process again to get it past the low water line where it can be recovered with a tractor. To get the riser as tight to the airbag as possible I have designed a latching mechanism that we drop down the riser. We pull a cord which locks it to the chain. Then we pull that up to the underside of the airbag with a lot of heaving, which in turn pulls up the riser so it is tighter to the sinker.
We used to have a launch with a winch on the bow to pull the riser up & wait for the tide. The club decided that it was too dangerous with 4 people in the stern balancing it & one in the bow winching. All the people involved were over 60 (called Dad's Army) & it was a recipe for disaster if the boat capsized if the mooring slipped slightly to one side of the bow & slewed it round
But it is such a faff we do not do it very often; relying on a tug with winch & hiab to lift our sinkers, weighing over 1 tonne. To make that economical we do it every 3 years & raise all the moorings in one go.
 
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oldharry

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50 years ago an old ships anchor was causing something of a hazard in Aberdovey Estuary after it became partially exposed. They tied it to a 30ft ships lifeboat at LW after digging out round it as much as possible. Then everyone went off to await the rise of the tide.

Unfortunately, the lifeboat didnt have sufficient buoyancy to defeat the suction and was pulled under by the rising tide....

Moral of this story, if you are going to use a boat to lift anything out of the mud/sand, a) make sure you have some quick release mechanism. b) dont head for the pub while you wait for the tide to come up!

Many fishing boats have winches big enough to lift the average sinker. Worth asking around? Some of our local fishing fleet would do it quite happily for a suitable 'donation'.
 

William_H

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Posters seem to assume that moorings etc should be lifted from the bow. What is far better is to lift from the middle of the boat by a bridle under the hull. On a yacht often the sheet winches are in just the right place or on a mobo a rope right around the hull over the open area. Of course with a fin keel boat you lose a lot of lifting space. Here the situation does not arise so much with minimum tides SCUBA diving tot he mooring and replace chain as necessary. Chains are not dropped for winter.
ol'will
 

Refueler

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Posters seem to assume that moorings etc should be lifted from the bow. What is far better is to lift from the middle of the boat by a bridle under the hull. On a yacht often the sheet winches are in just the right place or on a mobo a rope right around the hull over the open area. Of course with a fin keel boat you lose a lot of lifting space. Here the situation does not arise so much with minimum tides SCUBA diving tot he mooring and replace chain as necessary. Chains are not dropped for winter.
ol'will

With a Bilge Keeler - you can straddle the sinker as I used to do .... but often I was limited in time etc and then had to use forepart of boat .... not just the stemhead fitting - but both fairleads either side as well to spread the load.
 

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I find that with my mooring at Bangor that half way through the season that the natural movement of the boat clears the mud.
 

MontyMariner

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I was thinking to attach a big buoy low down to lift the chain
"To lift a mass of 1kg underwater the airbag needs to displace 1kg of water."
What's the weight of the chain and the size of the buoy? You will also have to factor in the force required to break the chain out from the sea bed, another factor is that if the buoy submerges, its lifting ability will diminish with depth.

I'm assuming that this is a drying mooring so you can get your hands to the chain, if that's so, then you would be better threading a rope through an eye attached to the chain, bring both rope ends up to either side of the bow of your boat and secure them under tension to cleats. Then as the tide rises you boat will act as the lifting bag and if there are any waves they will help break the chain out.

I've used this method, not on a drying mooring but by diving on the mooring to attach the rope, it worked well.
 
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oldharry

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All very well, but a properly designed mooring sinker may well have a concave surface underneath to provide greater suction. By no means all do, but those that do can require a great deal more lift to break the suction, possibly in order of tons more than the actual weight of the gear.
 

jdc

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All very well, but a properly designed mooring sinker may well have a concave surface underneath to provide greater suction. By no means all do, but those that do can require a great deal more lift to break the suction, possibly in order of tons more than the actual weight of the gear.

A very good point. Let's do some back-of-fag-packet calculations:

What is the area of the sinker touching the sea bed? Say 1m x 1m.
What is the depth? Say 6m at HW, less as the tide goes out (It's a drying mooring I believe).

The max suction force is the max pressure difference possible between the top and bottom of the sinker x the area of the sinker.

The pressure difference between a vacuum and the absolute pressure in the water, so 1 atmosphere + 6m head of water (which is ~0.6 atmospheres) totalling about 1.6 x 105 Pascals.

The area is 1 m2, so the force is 1.6 x 105 Newtons = 16 tonnes! Not to be taken lightly - if you'll forgive the pun.
 

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A very good point. Let's do some back-of-fag-packet calculations:

The max suction force is the max pressure difference possible between the top and bottom of the sinker x the area of the sinker.
There is your first mistake. If the sinker was made of styrofoam & 3 M tall Your pressure difference would be based on 3 Metres
If it was lead & 300mm tall your pressure difference between top & bottom of the sinker would be minimal
But the weight of the second sinker would be significantly greater & more likely to have greater holding power
Where do your figures allow for that?
 

jdc

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There is your first mistake. If the sinker was made of styrofoam & 3 M tall Your pressure difference would be based on 3 Metres
If it was lead & 300mm tall your pressure difference between top & bottom of the sinker would be minimal
But the weight of the second sinker would be significantly greater & more likely to have greater holding power
Where do your figures allow for that?

Keep up at the back! The calculation was for the effect of suction - I made no attempt to calculate the total holding power, which of course does depend on the weight.

But the pressure difference is between atmospheric pressure, about 105 Pascals, and a vacuum. the water depth adds a surprisingly small amount unless the water is deep; it only doubles the suction force at 10m.
 

Daydream believer

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Keep up at the back! The calculation was for the effect of suction - I made no attempt to calculate the total holding power, which of course does depend on the weight.

But the pressure difference is between atmospheric pressure, about 105 Pascals, and a vacuum. the water depth adds a surprisingly small amount unless the water is deep; it only doubles the suction force at 10m.
If you read the post i was demonstrating that the height of the sinker was irrelevant. It could be very tall or very shallow. as in one made of polystyrene or lead. But the combined weights are actually what forces the sinker downwards. you are not making allowances for these points
 

Rhylsailer99

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I tied 2 big buoys to the lowest part of the chain exposed.I then managed to sail from Bangor to my mooring in Red Wharf Bay in the same tide :) 1st time ever. The 2 big buoys was enough to to expose the ring so all good now thanks. The hardest part was stopping the boat landing right on top of the mooring as the tide was dropping due to wind against tide.
 
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