I had a new mooring laid around 6 months ago (see drawing and photo below), the bottom is hard sand (not mud) and the block just sits on the hard sand. This is causing a problem whereby the lighter D link chain finds its way underneath the concrete block. This shortens the whole scope of mooring by about 4-5 metres. It will sometimes free itself but I am wondering if I could deploy a mooring bouy somewhere along the mooring, either at junction between the two chains or between the lighter chain and poly rope? Hopefully this would lift the lighter chain off the bottom and prevent it from getting stuck under the block.
The other question is how do I stop the poly rope from chaffing on the bottom at the swivel, you can see in photo.
Thanks

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keensailor said..
I had a new mooring laid around 6 months ago (see drawing and photo below), the bottom is hard sand (not mud) and the block just sits on the hard sand. This is causing a problem whereby the lighter D link chain finds its way underneath the concrete block. This shortens the whole scope of mooring by about 4-5 metres. It will sometimes free itself but I am wondering if I could deploy a mooring bouy somewhere along the mooring, either at junction between the two chains or between the lighter chain and poly rope? Hopefully this would lift the lighter chain off the bottom and prevent it from getting stuck under the block.
The other question is how do I stop the poly rope from chaffing on the bottom at the swivel, you can see in photo.
Thanks

The rope and swivel should be just clear of the bottom at low tide. This may improve the other problem as well.

Perhaps start with a chat to the contractor and the other owners in your mooring ground? If you've paid a contractor, you shouldn't need to muck around with it. Not to mention giving him an excuse to waive any warranty.

I'm no expert but that D-link and swivel look a bit light to me unless your boat is pretty small. The swivel and secondary chain for my 3.5 tonne/28 foot Compass are far heavier. The issue is not so much absolute tensile strength, it's having enough metal to cope with material loss through corrosion or erosion. And hard sand = steady erosion.

Cheers, Graeme

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wongaga said..
Perhaps start with a chat to the contractor and the other owners in your mooring ground? If you've paid a contractor, you shouldn't need to muck around with it. Not to mention giving him an excuse to waive any warranty.

I'm no expert but that D-link and swivel look a bit light to me unless your boat is pretty small. The swivel and secondary chain for my 3.5 tonne/28 foot Compass are far heavier. The issue is not so much absolute tensile strength, it's having enough metal to cope with material loss through corrosion or erosion. And hard sand = steady erosion.

Cheers, Graeme

yeah, I spoke with contractor, he seemed disinterested and suggested I maybe try this or that. It took him 3 months to get around to the job in the first place so I'm not holding my breath.

Keensailor,
May be best to just get a diver with a water pump [firefighting?] and get him to sink the block into the sand.

Problem solved!

I did mine by just waving the sand away until it had sunk in, should take no more than a 1/2 hour to do.

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nswsailor said..
Keensailor,
May be best to just get a diver with a water pump [firefighting?] and get him to sink the block into the sand.

Problem solved!

I did mine by just waving the sand away until it had sunk in, should take no more than a 1/2 hour to do.

Yes, someone mentioned something like that except it was with a yabby pump. I think that would be a good option. Also reducing length of poly rope might help with scuffing of poly around swivel.

Where is your mooring nswsailor?

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nswsailor said..
Keensailor,
May be best to just get a diver with a water pump [firefighting?] and get him to sink the block into the sand.

Problem solved!

I did mine by just waving the sand away until it had sunk in, should take no more than a 1/2 hour to do.

What a top idea !

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keensailor said..

wongaga said..
Perhaps start with a chat to the contractor and the other owners in your mooring ground? If you've paid a contractor, you shouldn't need to muck around with it. Not to mention giving him an excuse to waive any warranty.

I'm no expert but that D-link and swivel look a bit light to me unless your boat is pretty small. The swivel and secondary chain for my 3.5 tonne/28 foot Compass are far heavier. The issue is not so much absolute tensile strength, it's having enough metal to cope with material loss through corrosion or erosion. And hard sand = steady erosion.

Cheers, Graeme

yeah, I spoke with contractor, he seemed disinterested and suggested I maybe try this or that. It took him 3 months to get around to the job in the first place so I'm not holding my breath.

Ramonas your man!

You have a design problem, the hawser is a part of the riser.
So use the heavy chain for the first part of the riser.
and most of the time this will sit on the bottom, then use the light chain to a swivel which is about 500mm below the surface with light chain then to a larger buoy.
The hawser takes off the swivel and up to the boat. (you will need a small float on it.
The larger buoy stays in the water.
While the larger buoy will occasionally rub against the boat it is really the only way over sand.
As the pic shows most chain last barely a year over sand if there is much movement.
Move over to the mud if you can.

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lydia said..
You have a design problem, the hawser is a part of the riser.
So use the heavy chain for the first part of the riser.
and most of the time this will sit on the bottom, then use the light chain to a swivel which is about 500mm below the surface with light chain then to a larger buoy.
The hawser takes off the swivel and up to the boat. (you will need a small float on it.
The larger buoy stays in the water.
While the larger buoy will occasionally rub against the boat it is really the only way over sand.
As the pic shows most chain last barely a year over sand if there is much movement.
Move over to the mud if you can.

Ok, so does this look like the design?
If so I just need to get a fairly stout bouy, some light chain and suspend my swivel 500mm below surface. Sounds like this will lift the lighter chain off bottom enough to prevent it working its way under the block and save it from erosion. Cheers lydia.

Careful with that solution... I had a similar set up, and my 30mm poly rope got caught around the float chain and chafed through. Not fun. You could try and run the rope through a float and tie a knot in it so no chance of snagging chain and chafe?

Perfect!
Just get a bigger swivel.
The length of the light D link should be a bit over the depth of the water.
Sounds as though the heavy d link might not be heavy enough as well.

Just a thought, what they are doing a bit in Melbourne apparently is using a nylon mooring strop straight from the mooring block to the buoy, it doesn't touch the bottom.
This is similar to the the offshore mooring setup and fish farms.

Look here
www.glbvic.com.au/recovery-gear/blacksnake-mooring-strops/
and here

Keensailor,

I'm moored in the Camden Haven River at Laurieton NSW mid north coast.

I've got a slightly different set-up as our river is very much alive and we get a lot of fouling.

I have 2m of ships anchor chain [I could just lift it] with 25mm thick steel, I then go to a large swivel and then to the 1/2" 2m chain [which is suspended, to act as a spring, except at very low tides] and then to the rope. The reason for putting the swivel between the chains is that it is mainly in contact with the sand and this keeps it clean and working. I service a few moorings here and those that insist in putting the swivel between chain and rope are wasting their time as it usually gets so fouled up that it cannot work.

Different but it works here.

I would sink the weight down a bit first. The fire hose with a length of plastic pipe on the end of the hose will make quick work of the job. Visibility will be poor while it's in operation!
The rest of the mooring is going to depend on how deep the water is. From your diagram it seems like you have too much mooring. I presume the mooring is in Drummoyne where there is very little tide and fairly calm water and just average breezes.
What do the neighbours have?
My mooring is on hard sand but because it is a strong tidal area and is a tram wheel the weight is buried. Only 10-12 feet of water. I have about 3-4 metres of heavy chain and 7 metres of 25mm nylon riser. The nylon has flat fire hose over it in a soft splice at the bottom. The swivel is about a metre off the bottom soft splices and covered in flat fire hose. Swivel and shackles the same size as yours but with electrical ties. The whole idea is to keep the mix of metals to the minimum. Where you have shackles and swivels direct to chain try to use lower quality than the chain. Shackles and swivels are cheap and just replace them regularly.
I had a good look at the units rumblefish linked to above and would consider that type for your situation. My new set up uses the same principals but because I have strong currents and wind over tide the floating buoy does not suit..
For a temporary set up I would consider shortening your riser. Maybe attach a trawler float direct to the lighter chain with electrical ties to keep the swivel off the bottom or get rid of the light chain and replace with a floating rope. There is no reason not to have the swivel much higher off the bottom.
This is a short video of my old mooring and a shameless selfie!

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Ramona said..
I would sink the weight down a bit first. The fire hose with a length of plastic pipe on the end of the hose will make quick work of the job. Visibility will be poor while it's in operation!
The rest of the mooring is going to depend on how deep the water is. From your diagram it seems like you have too much mooring. I presume the mooring is in Drummoyne where there is very little tide and fairly calm water and just average breezes.
What do the neighbours have?
My mooring is on hard sand but because it is a strong tidal area and is a tram wheel the weight is buried. Only 10-12 feet of water. I have about 3-4 metres of heavy chain and 7 metres of 25mm nylon riser. The nylon has flat fire hose over it in a soft splice at the bottom. The swivel is about a metre off the bottom soft splices and covered in flat fire hose. Swivel and shackles the same size as yours but with electrical ties. The whole idea is to keep the mix of metals to the minimum. Where you have shackles and swivels direct to chain try to use lower quality than the chain. Shackles and swivels are cheap and just replace them regularly.
I had a good look at the units rumblefish linked to above and would consider that type for your situation. My new set up uses the same principals but because I have strong currents and wind over tide the floating buoy does not suit..
For a temporary set up I would consider shortening your riser. Maybe attach a trawler float direct to the lighter chain with electrical ties to keep the swivel off the bottom or get rid of the light chain and replace with a floating rope. There is no reason not to have the swivel much higher off the bottom.
This is a short video of my old mooring and a shameless selfie!

Thanks Ramona
Yes, will try and shorten riser and employ a bouy.
Just FYI the mooring is at Callala Bay which has a hard sand bottom, little tide and highish winds.

I have not a mooring pic to post but the I have a loco wheel and two train wheels then very heavy link chain (can't lift it) which goes to a swivel then lighter chain to the buoy with hawser as discussed.
Most of the time the heavy chain holds the boat and with no load on the blocks (wheels).
This also cuts down movement of the chain on the bottom and hence wear.
I am in about 8 m of water over mud/sand with little tide flow but with what was very very heavy fouling conditions but that has improved.
The heavy chain gives good cantenary and I have never felt the boat pull hard against the blocks.
As you can see the mooring is quite open and isolated and is only 18 miles north of Mattsyker Island so it gets quite windy and the hills mean the boat gets quite buffeted and moves a lot around the mooring.

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keensailor said..

Ramona said..
I would sink the weight down a bit first. The fire hose with a length of plastic pipe on the end of the hose will make quick work of the job. Visibility will be poor while it's in operation!
The rest of the mooring is going to depend on how deep the water is. From your diagram it seems like you have too much mooring. I presume the mooring is in Drummoyne where there is very little tide and fairly calm water and just average breezes.
What do the neighbours have?
My mooring is on hard sand but because it is a strong tidal area and is a tram wheel the weight is buried. Only 10-12 feet of water. I have about 3-4 metres of heavy chain and 7 metres of 25mm nylon riser. The nylon has flat fire hose over it in a soft splice at the bottom. The swivel is about a metre off the bottom soft splices and covered in flat fire hose. Swivel and shackles the same size as yours but with electrical ties. The whole idea is to keep the mix of metals to the minimum. Where you have shackles and swivels direct to chain try to use lower quality than the chain. Shackles and swivels are cheap and just replace them regularly.
I had a good look at the units rumblefish linked to above and would consider that type for your situation. My new set up uses the same principals but because I have strong currents and wind over tide the floating buoy does not suit..
For a temporary set up I would consider shortening your riser. Maybe attach a trawler float direct to the lighter chain with electrical ties to keep the swivel off the bottom or get rid of the light chain and replace with a floating rope. There is no reason not to have the swivel much higher off the bottom.
This is a short video of my old mooring and a shameless selfie!

Thanks Ramona
Yes, will try and shorten riser and employ a bouy.
Just FYI the mooring is at Callala Bay which has a hard sand bottom, little tide and highish winds.

The plot thickens! Now I know who the mooring contractor probably is. The Westerly gales are nothing in Callala Bay compared to the Crookhaven river. Biggest problem you will face there is fresh Southerlies and SE with a heavy swell. The heavy swell is what sends all the yachts up on the beach. Several of the people there have moorings in the Crookhaven or Currimbene and if they are going to be away for awhile move their boats onto the safe moorings.

Select to expand quote

Ramona said..

keensailor said..

Ramona said..
I would sink the weight down a bit first. The fire hose with a length of plastic pipe on the end of the hose will make quick work of the job. Visibility will be poor while it's in operation!
The rest of the mooring is going to depend on how deep the water is. From your diagram it seems like you have too much mooring. I presume the mooring is in Drummoyne where there is very little tide and fairly calm water and just average breezes.
What do the neighbours have?
My mooring is on hard sand but because it is a strong tidal area and is a tram wheel the weight is buried. Only 10-12 feet of water. I have about 3-4 metres of heavy chain and 7 metres of 25mm nylon riser. The nylon has flat fire hose over it in a soft splice at the bottom. The swivel is about a metre off the bottom soft splices and covered in flat fire hose. Swivel and shackles the same size as yours but with electrical ties. The whole idea is to keep the mix of metals to the minimum. Where you have shackles and swivels direct to chain try to use lower quality than the chain. Shackles and swivels are cheap and just replace them regularly.
I had a good look at the units rumblefish linked to above and would consider that type for your situation. My new set up uses the same principals but because I have strong currents and wind over tide the floating buoy does not suit..
For a temporary set up I would consider shortening your riser. Maybe attach a trawler float direct to the lighter chain with electrical ties to keep the swivel off the bottom or get rid of the light chain and replace with a floating rope. There is no reason not to have the swivel much higher off the bottom.
This is a short video of my old mooring and a shameless selfie!

Thanks Ramona
Yes, will try and shorten riser and employ a bouy.
Just FYI the mooring is at Callala Bay which has a hard sand bottom, little tide and highish winds.

The plot thickens! Now I know who the mooring contractor probably is. The Westerly gales are nothing in Callala Bay compared to the Crookhaven river. Biggest problem you will face there is fresh Southerlies and SE with a heavy swell. The heavy swell is what sends all the yachts up on the beach. Several of the people there have moorings in the Crookhaven or Currimbene and if they are going to be away for awhile move their boats onto the safe moorings.

It's not a local contractor, they are from Batemans bay.
I like the sound of that nylon strop and bouy arrangement mentioned by rumblefish. Might have to consult local maritime officer ?

Select to expand quote

keensailor said..

Ramona said..

keensailor said..

Ramona said..
I would sink the weight down a bit first. The fire hose with a length of plastic pipe on the end of the hose will make quick work of the job. Visibility will be poor while it's in operation!
The rest of the mooring is going to depend on how deep the water is. From your diagram it seems like you have too much mooring. I presume the mooring is in Drummoyne where there is very little tide and fairly calm water and just average breezes.
What do the neighbours have?
My mooring is on hard sand but because it is a strong tidal area and is a tram wheel the weight is buried. Only 10-12 feet of water. I have about 3-4 metres of heavy chain and 7 metres of 25mm nylon riser. The nylon has flat fire hose over it in a soft splice at the bottom. The swivel is about a metre off the bottom soft splices and covered in flat fire hose. Swivel and shackles the same size as yours but with electrical ties. The whole idea is to keep the mix of metals to the minimum. Where you have shackles and swivels direct to chain try to use lower quality than the chain. Shackles and swivels are cheap and just replace them regularly.
I had a good look at the units rumblefish linked to above and would consider that type for your situation. My new set up uses the same principals but because I have strong currents and wind over tide the floating buoy does not suit..
For a temporary set up I would consider shortening your riser. Maybe attach a trawler float direct to the lighter chain with electrical ties to keep the swivel off the bottom or get rid of the light chain and replace with a floating rope. There is no reason not to have the swivel much higher off the bottom.
This is a short video of my old mooring and a shameless selfie!

Thanks Ramona
Yes, will try and shorten riser and employ a bouy.
Just FYI the mooring is at Callala Bay which has a hard sand bottom, little tide and highish winds.

The plot thickens! Now I know who the mooring contractor probably is. The Westerly gales are nothing in Callala Bay compared to the Crookhaven river. Biggest problem you will face there is fresh Southerlies and SE with a heavy swell. The heavy swell is what sends all the yachts up on the beach. Several of the people there have moorings in the Crookhaven or Currimbene and if they are going to be away for awhile move their boats onto the safe moorings.

It's not a local contractor, they are from Batemans bay.
I like the sound of that nylon strop and bouy arrangement mentioned by rumblefish. Might have to consult local maritime officer ?

I think you should employ ramonas services for your mooring keen! he knows what to do and is only 20 min away :)

Select to expand quote

lydia said..
I have not a mooring pic to post but the I have a loco wheel and two train wheels then very heavy link chain (can't lift it) which goes to a swivel then lighter chain to the buoy with hawser as discussed.
Most of the time the heavy chain holds the boat and with no load on the blocks (wheels).
This also cuts down movement of the chain on the bottom and hence wear.
I am in about 8 m of water over mud/sand with little tide flow but with what was very very heavy fouling conditions but that has improved.
The heavy chain gives good cantenary and I have never felt the boat pull hard against the blocks.
As you can see the mooring is quite open and isolated and is only 18 miles north of Mattsyker Island so it gets quite windy and the hills mean the boat gets quite buffeted and moves a lot around the mooring.

wheres your mast?

Slightly off topic, but has anyone got any experience with seagrass-friendly moorings?

www.seagrassmooring.com.au

Man I like the idea of using the Nylon strop mentioned by Rumblefish. Nothing to rust - every 2/3 years my mooring guy pulls up his oxy torch to replace swivels and lengths of heavy or light chain.
With the nylon strop, no need for that, just good inspection.
Now if you could eliminate the galvanised thimble on the strop as well, with a thick soft shackle or even a pair, it would be totally rust free.
Who's our soft shackle man on this board (thought he makes and sells them) - can he chip in and explain why they should or should not be used on a mooring?

Best mooring I have seen was a cast concrete in a skip bin, with a lot of scrap iron encapsulated in the block. At the top it it had a 2 ft eye of steel reo, again encapsulated in concrete.

Through the eye was very heavy nylon rope in a loop to the buoy. To check the mooring all you had to do was haul the rope through the eye to check for wear....if it needed replacement - just attach new rope to old, and haul through and join.

Never had to leave the boat to check to mooring.

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scruzin said..
Slightly off topic, but has anyone got any experience with seagrass-friendly moorings?

www.seagrassmooring.com.au

No experience with them but these are the moorings that keensailor is supposed to have in Jervis Bay. Jervis Bay is a national park and the idea was that boats were to be allowed to stay in the bay only if they had screw in seagrass friendly moorings. Screw in moorings cost twice the price of conventional moorings because it takes two divers to do the job. Most people opt for the conventional mooring and everybody seems to ignore the original rule. I believe the courtesy moorings on the Eastern side are seagrass friendly.

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Sectorsteve said..

keensailor said..

Ramona said..

keensailor said..

Ramona said..
I would sink the weight down a bit first. The fire hose with a length of plastic pipe on the end of the hose will make quick work of the job. Visibility will be poor while it's in operation!
The rest of the mooring is going to depend on how deep the water is. From your diagram it seems like you have too much mooring. I presume the mooring is in Drummoyne where there is very little tide and fairly calm water and just average breezes.
What do the neighbours have?
My mooring is on hard sand but because it is a strong tidal area and is a tram wheel the weight is buried. Only 10-12 feet of water. I have about 3-4 metres of heavy chain and 7 metres of 25mm nylon riser. The nylon has flat fire hose over it in a soft splice at the bottom. The swivel is about a metre off the bottom soft splices and covered in flat fire hose. Swivel and shackles the same size as yours but with electrical ties. The whole idea is to keep the mix of metals to the minimum. Where you have shackles and swivels direct to chain try to use lower quality than the chain. Shackles and swivels are cheap and just replace them regularly.
I had a good look at the units rumblefish linked to above and would consider that type for your situation. My new set up uses the same principals but because I have strong currents and wind over tide the floating buoy does not suit..
For a temporary set up I would consider shortening your riser. Maybe attach a trawler float direct to the lighter chain with electrical ties to keep the swivel off the bottom or get rid of the light chain and replace with a floating rope. There is no reason not to have the swivel much higher off the bottom.
This is a short video of my old mooring and a shameless selfie!

Thanks Ramona
Yes, will try and shorten riser and employ a bouy.
Just FYI the mooring is at Callala Bay which has a hard sand bottom, little tide and highish winds.

The plot thickens! Now I know who the mooring contractor probably is. The Westerly gales are nothing in Callala Bay compared to the Crookhaven river. Biggest problem you will face there is fresh Southerlies and SE with a heavy swell. The heavy swell is what sends all the yachts up on the beach. Several of the people there have moorings in the Crookhaven or Currimbene and if they are going to be away for awhile move their boats onto the safe moorings.

It's not a local contractor, they are from Batemans bay.
I like the sound of that nylon strop and bouy arrangement mentioned by rumblefish. Might have to consult local maritime officer ?

I think you should employ ramonas services for your mooring keen! he knows what to do and is only 20 min away :)

I'm not a mooring contractor. Unfortunately our main mooring contractor died recently. Blood clot to the brain as he was climbing aboard his plane! The government contract for all the buoys has been taken up by a company from Batemans Bay. That local fiasco you witnessed was from another contractor.
I do my own mooring maintenance and quite a few others do the same. I have been trying to talk my mate into taking it on professionally but he is reluctant to work! It's a young mans job.

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Karsten said..
Man I like the idea of using the Nylon strop mentioned by Rumblefish. Nothing to rust - every 2/3 years my mooring guy pulls up his oxy torch to replace swivels and lengths of heavy or light chain.
With the nylon strop, no need for that, just good inspection.
Now if you could eliminate the galvanised thimble on the strop as well, with a thick soft shackle or even a pair, it would be totally rust free.
Who's our soft shackle man on this board (thought he makes and sells them) - can he chip in and explain why they should or should not be used on a mooring?

Yes, heavy-duty nylon mooring lines (like those Blacksnake strops) through a large eye on a heavy block sounds like a perfect setup, and seagrass friendly too. I'm guessing the block needs to be considerably heavier than usual to cope with greater vertical forces. What are the other pros and cons?

Select to expand quote

Karsten said..
Man I like the idea of using the Nylon strop mentioned by Rumblefish. Nothing to rust - every 2/3 years my mooring guy pulls up his oxy torch to replace swivels and lengths of heavy or light chain.
With the nylon strop, no need for that, just good inspection.
Now if you could eliminate the galvanised thimble on the strop as well, with a thick soft shackle or even a pair, it would be totally rust free.
Who's our soft shackle man on this board (thought he makes and sells them) - can he chip in and explain why they should or should not be used on a mooring?

I can get them made with solid nylon thimbles (of my own design, secret squirrel stuff!), no metal but unfortunately soft shackles or dyneema of any sort here would still need thimbles and shackles as it would wear on the connection point.

But.....a large (oversize) black shackle siezed with cable ties, will last 5 years in most environments, especially if off the bottom, plus you do still need a swivel between the shackle and weight

Oh, and i might be the 'soft shackle man' you refer to!!!

I guess the point is, with a big weight and an attachment in the midddle, it's pretty easy to dive and check yourself or get a diver to, and there is only 2 things to replace!!!

PM me if you want pricing on the Black Snake Mooring strops :)

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scruzin said..

Karsten said..
Man I like the idea of using the Nylon strop mentioned by Rumblefish. Nothing to rust - every 2/3 years my mooring guy pulls up his oxy torch to replace swivels and lengths of heavy or light chain.
With the nylon strop, no need for that, just good inspection.
Now if you could eliminate the galvanised thimble on the strop as well, with a thick soft shackle or even a pair, it would be totally rust free.
Who's our soft shackle man on this board (thought he makes and sells them) - can he chip in and explain why they should or should not be used on a mooring?

Yes, heavy-duty nylon mooring lines (like those Blacksnake strops) through a large eye on a heavy block sounds like a perfect setup, and seagrass friendly too. I'm guessing the block needs to be considerably heavier than usual to cope with greater vertical forces. What are the other pros and cons?

Out of interest they did pull testing with a 40ft fishing boat with 250hp (about) and they could only pull 1.4t max on the load cell.

You'd be surprised how little force a yacht actually put on the mooring, even in a swell and blowing a gale. If the mooring is in shallow water often there is far more force exerted from the actual swell on the bottom that the boat itself.

I supplied two moorings to the East Coast down here for a hard sand bottom, one in 4m and one in 8m. 12 months later they were both exposed to 30 knots and 2m swells. The 8m one had a 50ft yacht on it for the period of the storm and didn't move, the shallower one had no boat on it.
The shallower one moved and eventually wore the rope, the deeper one with the boat on it didn't move at all!!!

These are the mooring blocks and tackle my mate and I have.

No shackles or chain. The line is 20 mm Superdan rated at 6.7 tonne load.

Being in the river we are required to have up and downstream moorings.

The upstream blocks are the doubles which weigh 250 kg and the single downstream block came in at 197 kg.

I was advised that chain would last only 3 years due to constant tidal movement and the cocktail of chemicals in the water from various runoff sources upstream.

Steel and iron is better than concrete as it has only 10% buoyancy compared to around 50% for concrete. The footprint is smaller too and will have less of a tendency to slide over the bottom.

Do you know frank? With "bundeena" 52 foot yacht in callala?
If not and you want his number message me. We were talking about moorings in callala bay. He gets it done right. He has to.