Eco mooring buoys

paul.norton said:
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The EFM concept of keeping chain off the sea-bed sounds ok in theory but what of situations where the tidal range is much more than the 2 meters at Studland?

Paul
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It is kind of the reverse logic of "weighted anchor warp" - I have a great one for my kedge, that has small weights manufactured into the rope so sinking it. I suppose we could put floats on the chain every metre, so as long as the min depth > 1/2m the chain never touches the bottom, but does sink as tension is applied. Does the concept work that way round? Anyone want to give us the Physics of the scenario?
 
Genoa said:
It is kind of the reverse logic of "weighted anchor warp" - I have a great one for my kedge, that has small weights manufactured into the rope so sinking it. I suppose we could put floats on the chain every metre, so as long as the min depth > 1/2m the chain never touches the bottom, but does sink as tension is applied. Does the concept work that way round? Anyone want to give us the Physics of the scenario?
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2 Things - you would need a huge chain locker to store all those floats. 2 The chain running on the seabed forms part of the holding power of the anchor. Any mooring contractor will tell you that normally a chain wears most at the top where there is the most movement, and in the middle sections where it drags across the seabed. Normally very little wear takes place near the sinker, as the load only comes on it in bad weather.

I say normally, because there are situations where the wear patterns are very different.
 
Paul,

I can't imagine why the mooring line should sink when it normally floats if it's under tension ?

Traditional chain moorings tend to corrode at the surface end first as that is exposed to oxygen, as well as having more constant movement.

As an aside, on chain moorings the swivel is almost always the weakest link, so should be checked regularly for wear and ensuring it hasn't seized up.
 
For many years I had a mooring that consisted of a heavy ground chain between two mooring anchors. The riser was (something like) 50mm octoplait type rope up to the swivel and buoy then smaller octoplait ropes as strops.
I could well imagine that putting small floats up the riser would successfully keep the riser off the ground. I've still got the riser which is still in excellent condition and will, one day, put it onto my current (fore and aft) mooring.
 
With a heavy sinker or ground chain, the riser is only connecting the mooring to the sinker chain. It doesn't need to be that long - just long enough to minimise snatching in waves at HW, say 2x depth. If one has a buoy always below the surface with just enough buoyancy to support a chain riser off the sea bed, then the rest of the riser can be a non-floating rope (or elastic band) to the mooring buoy. Oh, that's probably an ECO mooring anyway, isn't it? ;)

No scouring, no risk of entanglement, snatching minimise by elasticity of the rope section & movement of the submerged float.
 
I had a deep water mooring with a 14mm nylon strop protected by plastic food grade hose pipe; I had to replace it every 3 months as the strop wrapped under the buoy at wind over tide, cutting it on the razor sharp barnacles on the underside of the buoy.

Several boats at my club have been set adrift by rope strops chafing through and separating, one E-Boat was destroyed by this.

As well as avoiding chafe, chain strops can be padlocked to prevent yobs casting boats adrift !
 
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