My mooring may have moved.

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pandos

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Following recent storms It seems that my boat is closer to its neighbour, and to an empty mooring than I think it used to be.

I am moored in a tidal river, reasonably sheltered but am exposed mainly to SW gales, with about eight feet of water at low tide with a range of 4m approx. I have had a boat on this mooring through many storms in the past but the mooring was not used for the last 5 years. The block is 2.5 tons, attached to this is eight to ten feet of ships anchor chain, with a rope riser. It is in place about 8 years so I would have thought it was well bedded in, although it may have been lifted a few years ago when my neighbour drifted up and became entangled in my, then empty mooring.

I do not want to pay a diver or a contractor to do anything.

Two questions.

1. Is this madness.? My thoughts: drop two anchors one upstream and one downstream of my correct position. Pass a lifting sling over my deck, using a stout plank as a spreader and plenty of padding just forward of the keel and fix this to the ground chain at the bottom of the tide. When the tide rises the block will lift and I could haul myself 20m or so up river and wait till the tide drops again and then release the block.

2. How can I augment the mooring block, without getting into the water?

Thanks in advance.

Tony.
 
One point, putting your repositioning aside for a moment; you have a rope all the way from the very heavy chain on the seabed ? Doesn't sound like any set-up I've come across, I'd have expected a lighter chain the boat can lift, with a swivel in there somewhere hopefully off the seabed and within reach to change every so often.

As for the lifting, what sort of / how big is your boat ?
 
You need to be a bit careful here: if the sinker is properly designed there should be considerable suction to break before it lifts. Some time ago an old ships anchor was found i the sand at Aberdovey. They tried to dig it out, then tied a large ships lifeboat to it to lift it on the rising tide. They all then went home to wait for the tide. Unfortunately in spite of the massive buoyancy of the lifeboat, the anchor did not budge and pulled it under. They di retrieve it eventually, and it is to be seen to this day on the quay there.
 
Seajet said:
One point, putting your repositioning aside for a moment; you have a rope all the way from the very heavy chain on the seabed ? Doesn't sound like any set-up I've come across, I'd have expected a lighter chain the boat can lift, with a swivel in there somewhere hopefully off the seabed and within reach to change every so often.

As for the lifting, what sort of / how big is your boat ?
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You are correct there is a rope all the way from the heavy ground chain to a swivel just under the buoy, This is the custom in the area and seems to work fine. My previous boat broke loose a few years ago due to the rope wearing through a few feet from the bottom, it was replaced with a new rope of the same length and over 6 months this showed signs of wear, I had a new shorter one put in place and this has shown no sign of wear whatsoever, after use for two years with frequent checking.

I had the entire mooring line in the dingy today and it seems to be perfect, I am going to replace the lot with stronger rope shackles and swivel etc but am sticking to the same system. ( i am a bit suspicious due to there being no wear anywhere on the system after being in the water untouched by me for at least 8 years. ( it is possible that the entire system was lifted and replaced from the ground chain up a few years ago)

The boat is a 35 footer so unlikely to be pulled under, particularly if the sinker has in fact moved in the last few weeks, either way I would be staying on board and would cut the rope should I begin to submerge.

The weight is a concrete block approx 4 feet square by 20 inches high. it had a dimple in the underside.
 
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Yes it's going to uner huge strain, the dimple on the underside of the sinker is presumably to promote suction.

Obviously you wouldn't want to cut a lifting sling but there needs to be a rope link somewhere for you to cut if things get hairy.

It would need quite a few turns of line to take this load I'd think - must be kept even sided at all costs - and presumably you or someone in a dinghy with an old breadknife, hopefully with a lanyard on it and a spare knife.

Personally if there's a boatyard workboat or similar handy I'd happily pay them, having just seen you have a HR to mess up ?!

If you do move it, it can be disorienting trying to position sinkers, if the depth isn't too great two pairs of bamboo canes or similar poles, in line as transits longitudinally and laterally ( so at 90 degrees to each other ) can be a help.
 
So you have a load of 2.5 tonnes, minus buoyancy of concrete, plus considerable mud suction, probably working out to substantially more than 2.5 tonnes. And you're going to put this onto a plank across your coachroof?

Pete
 
Each spring I have my mooring lifted onto the deck of a barge and inspected. It costs me <£200. In your situation, in would advise you find a similar set up & it would be money well spent.

You are proposing to precariously deal with a lot of force. Where a lot could go expensively wrong...
 
Actual weight of block is only around 800 kgs,

Weight of concrete is 2400kg per m3.

1.2 * 1.2 * .4 = .576 * 2.4 =1.38 -.576 quals approx 800kgs. ( hardly heavier then the capacity of fuel and water on the boat. (650kg)

Suction and the weight of the ground chain is the real issue...

Weight would be taken on the top of the hull.
 
If the block is going to be that hard to lift how likely is it to have dragged? Could it be that the chain is the only bit that has moved?
 
Lets say that you need to lift 3000 Kg, it will need 3 cubic metres displacement of fresh water to displace it and a wee bit more to lift it, so if your boat displacement is up to the job you will certainly lift it.
The issue will be the lifting beam strength and the crushing force across the deck.
 
Why is anyone debating this? Mooring need checking professionally with the proper gear. I don't trust diver surveys as they do not "test" the installation. My insurers require an annual service as a matter of course and I do not have a problem with this.
 
sailorman said:
My insurers do not
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Since when did you have a mooring? Especially as you used mine at least once last year? And if you do and they don't and you don't get it checked annually, good luck to you! I had new gear laid in 2010 expecting 5 years, on the last inspection, 2013 the riser link was worn 50% and was replaced. How would you know otherwise? Let me know the number of your mooring and I'll avoid it. :) :encouragement:
 
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Force Majeur?

By "force majeur" I mean a risk beyond reasonable control. I would not contemplate the mooring moving scheme even for a nanosecond - you must be well brave Tony.
So no advice to you on that point Sir. But are you certain that the mooring has moved?
By way of an example - consider the idyllic mooring here -View attachment 38588
I was onboard overnight during recent storm force winds and big tides. Wakened by irregular roll of the boat - we were entangled by both the doubled up and shortened dingy warps and the Hydrovane rudder with the neighbouring mooring buoy. Had to cut the warps and was lucky not to lose the dingy. I am certain that the moorings have not moved - the combination of violent wind and torrent like ebb had brought the boat up against the empty buoy, an occurrence which ordinarily one would have discounted - but clearly tide going one way and wind the other can close gaps!
Good luck if you do the move!
Robin
Pleiades of Birdham
MXWQ5
 
I would encourage the OP to consider the effects on stability if anything goes wrong or not quite to plan.....

BIG mooring anchors were moved around our harbours in the days of working sail by means of two 'ships boats' with a couple of hefty spars lashed athwartships to make a form of catamaran. Tidal rise was used to raise the hook between them, as the OP is considering, then the load was rowed or towed into position, whence the heavy 'ook was slipped.

This was a standard technique for laying out another 'best bower' ahead of a coming storm, or for setting an 'eavy 'ook several cables out from the loading quay. The ship would then be warped out, then the process repeated, until she was secured out in the roadstead and/or/until ready to make sail and depart.
 
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