Dragging Mooring

[awol]

Though most Clyde sailors prefer Sir Boyd's delicacies despite his views on independence.

 

[Daydream believer]

@Neeves
My mooring consists of a single railway wagon wheel, circa 200kg I believe, with a length of heavy stud-link chain threaded through it; not sure how long that is. I think that would be what you refer to as the ‘sweeper’. The stud-link chain is shackled to another length of chain, somewhat greater than the max tidal range, followed by a rope riser to the buoy. This ensures there is no chance of the rope abrading on the sea floor.
The bottom is a layer of shell and stone on hard grey clay. When I’ve watched my mooring being lifted it’s always been clean, so I don’t think it sinks into the clay much, if at all.
Next year there will be TWO waggon wheels.

If I am not mistaken ( I may well be) Your 200Kg wagon wheel only weighs 174Kg when in water. That is ridiculously small for such a boat , unless it was well embedded in mud- Which you say is not the case. One cannot really rely on the weight of chain as that just helps to reduce "snatch" due to the catinery effect. But, perhaps, then only if the rode is long enough to allow it to form a sufficient catinery.

You need to decide how the wheels will be placed. Side by side with a link chain ( to get better suction) or one on top of the other with the chain through the middle. One assumes it does not go round the bottom & back outside the wheel but is fixed at the centre. If the chain went round it would want to lift one edge which would break it free easily.

In our moorings I use concrete blocks of circa .75 tonnes for that size boat & .5 tonnes for boats of 20ft. But most of ours are in thick mud so we let them settle for 14 days prior to placing a boat on them. The rode is then calculated a depth at springs, + 1 M for surge, & multiplied * 1.5.
Our largest boat, 45 ft, has a 2.5 Tonne sinker & that is in thick mud.

 

[Porthandbuoy]

If I am not mistaken ( I may well be) Your 200Kg wagon wheel only weighs 174Kg when in water. That is ridiculously small for such a boat , unless it was well embedded in mud- Which you say is not the case. One cannot really rely on the weight of chain as that just helps to reduce "snatch" due to the catinery effect. But, perhaps, then only if the mooring is long enough to allow it to form a sufficient catinery.

You are correct. Weigh too small (sic)

 

[awol]

I would be having words with your mooring contractor - I assume the mooring was specified for your yacht. My 5 tonne vessel has 2 rail wagon wheels (I don't know the size) which have held it through much worse gales than Friday's.

 

[Neeves]

If I am not mistaken ( I may well be) Your 200Kg wagon wheel only weighs 174Kg when in water. That is ridiculously small for such a boat , unless it was well embedded in mud- Which you say is not the case. One cannot really rely on the weight of chain as that just helps to reduce "snatch" due to the catinery effect. But, perhaps, then only if the rode is long enough to allow it to form a sufficient catinery.

You need to decide how the wheels will be placed. Side by side with a link chain ( to get better suction) or one on top of the other with the chain through the middle. One assumes it does not go round the bottom & back outside the wheel but is fixed at the centre. If the chain went round it would want to lift one edge which would break it free easily.

In our moorings I use concrete blocks of circa .75 tonnes for that size boat & .5 tonnes for boats of 20ft. But most of ours are in thick mud so we let them settle for 14 days prior to placing a boat on them. The rode is then calculated a depth at springs, + 1 M for surge, & multiplied * 1.5.
Our largest boat, 45 ft, has a 2.5 Tonne sinker & that is in thick mud.

Useful reply, thanks.

Good to get some numbers.

Jonathan