Advice please best solution for a mooring chain

HG02,

What you need is a mooring snubber.

You will need about 3 m plus of 16 mm [min] 3 strand nylon anchor line. Bigger boat more length and diameter.
That size is what I use on my Top Hat of 3,000kg.

On one end splice a Stainless steel chain grab hook [whitworths page 99, item 43887 etc]

Anchor and securely tie off your chain in your normal manner.

Secure the bitter end of your anchor snubber and then pull in some chain, of more length than your snubber.
Attach the chain hook and let the snubber out [over the bow cleat] drape the anchor over all that and secure at the cleat so it will not jump out.
You should end up with the chain having a small loop after the bow cleat to the chain grab hook.

Just one caution, if you spend some days on a snubber with a big blow you will have to replace the snubber rope as it will have lost all its elasticity.

Enjoy

Not sure if NSW got the gist of what you want. If it's for your permanent mooring, you need to get something a little more substantial than a snubber.....

A standard permanent mooring set up would be a bit like this.
Attached to your block, you should have 35mm+ stud link ground chain, with about a 20mm swivel, then enough mild steel 16mm chain to reach the surface, followed by 24mm silver rope protected over the bow roller by heavy duty anti-chaff plastic sleeve, then your bouy and hook up line.

Based on your description, you're missing the 24mm silver rope and sleeve.

You are right Michael,

Miss read that as normal ANCHOR chain.

But you will still need the snubber HG02 when you eventually start to move around.

Silver rope is not terribly high quality line. Silver line of 24 mm diameter, I am told at out local chandlers, has a minimum breaking load of 4.1 tonne.

On the other hand, Superdan rope/line of 20 mm diameter has a minimum breaking load of 6.9 tonne. Nearly twice and it is economical to buy the 125 m coil for $294 and have 75 m left over for other uses as opposed to buying silver line cut off the coil at $4.70/metre.

http://www.nobles.com.au/Products/Fibre-Rope/Superdan-Rope

The experience of Midtown Marinas in Bundaberg with their moorings was that they were lucky to get three years out of chain on their moorings. This is partly due to current flow in the river which induces electrolysis and erosion of the metal. They then went to using 32 or 35 mm silver rope (that weight of line because they are commercial) and had excellent results until the floods swept everything away.

The river was flowing at 80 kmh on the surface and estimated to be flowing at 120 kmh in the depths. The only things that survived in the Burnett River were things that had been there for 100 years.

The set up with the mooring lines was that they were 1.5 metres longer than the maximum tidal depth with an eye spliced into each end with plastic tube slid over the line before splicing.

Then the eye was passed through the metal eye of the block and the top end of the line passed through the eye at the bottom and pulled up tight. The top end of the mooring line was then shackled to the mooring buoy which was a double cone buoy with a s/steel rod through the middle with an eye top and bottom.

The advantages of this system are multiple, assuming the mooring block is of sufficient weight and holding power. Steel and or iron are far superior to concrete as concrete has about 50% buoyancy and steel or iron will self bury in the bottom much quicker.

Advantages:-

No electrolysis or chafe of mooring tackle if subject to tidal or current flows.

Easy replacement of mooring tackle. All the diver has to take down is the new line and a knife to cut the old one away.

In choppy conditions the rope tackle will not jerk like chain and there are less wear points.

With the buoy set up as described all one has to do is approach the mooring, grab it's grab line (short and not dangling in the water, therefore no grunge), slip a line through the eye atop the buoy and secure both ends to the vessel. No need to bring any marine growth on deck.

The mooring I am in the process of building for Second Wind in the Distillery Reach of the Burnett River has to be a fore and aft mooring. The upstream weight will be two truck brake drums filled with other weights and joined with steel bars around which will go the mooring tackle.

The downstream weight will be a single truck brake drum also weight filled with a steel eye in the middle.

For my 4 tonne yacht the upstream weight will be around 250 kg or a quarter of a tonne and half that for the downstream.

This is my first permanent mooring so if anybody with mooring experience sees glaring holes in my logic, please let me know. I only want to do this once.

Don't use silver rope. Seagreen is what the local contractors use. Its basically the same as what Cisco mentioned but 3 strand instead of plait. Floats, UV resistant but because you need a reasonable shock resistance in your mooring ends up thicker than what you would use in Nylon. This is fairly important in rivers and estuaries where the current can be strong. I will be switching to nylon when I get around to it. For abrasion where the riser comes over the bow roller use half a metre of that flat polyprop blue fire hose wrapped around the riser and fixed with cable ties. Do not use clear or reinforced plastic hose! This hardens in sunlight and the ends become sharp enough to cut through risers. This has sent several boats on to the beach here.
There are web sites that have trials that the US coast guard did on the best mooring practices where they compared the best materials for moorings. Its worth chasing up and having a look. Basically the safest moorings they recommend are chain, nylon risers and poly prop fire hose anti chaff.

Silver rope and plastic anti chaff.
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hi guys i am not an expert by any means but have recently put a mooring in for my jarkan 6.5 tons
i used a concrete block 1200x1200x 300mm filled it with as much cast iron scraps i could fit in had a stainless eye cast into the top then added a aprox 900mm diametre loco train wheel to the top.
the depth is 8m at high tide so i put 6m of 38mm stud link chain on the block and wheel then 4 metres of 25mm chain this will enable me to pull the end of the chain clear of the water for maintenance then spliced 12m of that green 3 strand rope to the chain with a metal thimble in the splice both ends the other end going up to a swivel below the inflatable buoy a shackle here moused with cable ties to a spliced 3 strand rope with thimble and connect this to a cleat on the bow not the anchor winch as these are not designed to hook mooring lines to
she holds well but this winter will test it out iam sure.
i think i have around 900 kg of weight in the bottom tackle

Mooring weight is a major factor. The left over concrete thing is done in most concrete depots and is cheap. The expensive part is getting it to where you want it.

Your 450 kg concrete block becomes 225 kg when submerged. Steel and iron only lose the weight of their volume of water, ie the water they displace.

Example:- My weight is 130 kg and it's volume is 30 litres, therefore when submerged it's effective weight should be 100 kg
This is my down stream/stern mooring weight which only has to hold against the incoming tide.

My upstream/bow mooring weight is twice the weight and volume and has to hold against river current and ebbing tide.

The spacing of the weights has to be 20 metres and the yacht is only 10 metres long so therefore I can put some scope into the bow mooring line say 2:1. The scope is the hypotenuse of the triangle with the depth being the perpendicular height and the horizontal distance of the bow from the weight being the base of the triangle.

My reasoning is that the boat is securely anchored with a 13.6 kg (30 lb) anchor with say another 16.4 kg of chain holding her giving an all up weight of 30 kg on between a 3:1 to 5:1 scope.

Therefore with a seven fold increase in weight and a reduced scope, the holding should be at least as good if not better.

This is just a mental estimation with no specific formula applied. I did do some Googleing of the subject though and came up with these articles.

www3.telus.net/sail/sj23/b_hull_tips/b27.html

The table in this next one indicates in a protected area a 225 kg weight is suitable for a 30 foot yacht.

www.jamestowndistributors.com/userportal/document.do?docId=1107

www.captfklanier.com/articles/art30.html

Further comments from anybody are welcomed.

cisco it reads in the second link you have given us quote shortened scope means a more effective anchor is required. Therefore, a permanent mooring anchor must be significantly heavier than your everyday use anchor. Mooring scope from anchor to end of pennant should be at minimum 3 times the depth of water at highest tides.
i think you need to beef it up significantly also what is the bottom like as some bottoms will not cover your tackle it will just sit there and if it is not big enough when the boat pulls and fetches on it it moves my ten cents worth

Few months ago an nice composite 31 footer came off a mooring here. I pulled the mooring back up onto the foredeck and laid the bottom end out to take a photo. The owner was away in Tasmania at the time and the boat was for sale so I could not post photos then. Mate and I put out the anchor into deep water to float her off. I'm always interested on what fails with moorings. In this case it was the bottom chain where the links simply wore away do to abrasion with sand. Mooring is in a particularly strong current area. Note the electrolysis on the shackle where the SS mousing has reacted against the mild steel. There is some electrolysis on some links and the swivel pin. The bottom shackle is shiny were it rubs over the sand bottom at every tide change, the swivel must have been clear.
Bottom chain generally lasts about 3 years where this mooring was. Shackles and swivels moused with SS about 12 months. The problems I see generally are from a miss match in quality of materials. I would suggest top quality chain and use Chinese swivels and shackles [cable tie mousing] and change the swivel and shackles annually. This way the chain which is fairly expensive should have a long life at the expense of the cheap hardware.
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There appears to be a lot of electrolysis happening on the shackle pin itself. It looks to be a lesser diameter than the chain link through which its passing.

That photo and the article LooseChange posted has convinced me that having rope mooring tackle only is the way to go.

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LooseChange said...


There appears to be a lot of electrolysis happening on the shackle pin itself. It looks to be a lesser diameter than the chain link through which its passing.

This was an unusual case where the pin had actually been worn away from the sand and electrolysis. The pin was still secure. Usually the thread disappears fairly quickly with SS mousing and the pin freely rotates and can slip out if the mousing is not done up in the figure 8 method. This is probably the most common mooring failure. The pin in this case originally was 12mm.

Jervis Bay is a national park and new moorings are supposed to be of the new enviromental type in the report you provided the link for. Basically its a big screw that's wound down into the seabed. On top of this is a SS shock absorber that's free to rotate but not touch the bottom, then a rope riser to the boat. Not sure of the current price but last year it was $3000, twice what a conventional mooring is. They still lay conventional as well. The extra cost is of course the labour costs for the divers to insert the screw. Use Google pictures to see plenty of examples of the screws.

On the subject of scope. The limitation is how many moorings are in your area. With swing moorings and a mixture of yachts, motor vessels and particularly catamarans the scope has to be fairly short to allow them to rotate without kissing the neighbouring boat. Catamarans will be effected more by wind than tide and need more free space. In a tidal estuary vessels don't all swing the same way when there is no wind and a tide change.
Couple of years ago I was chatting to the local MSB bloke about moving my mooring. As we were talking the tide changed and the neighbouring concrete footpath parked herself neatly alongside my tender. This convinced the MSB bloke.
During the week the new MSB bloke [ex navy] was on one of the yachts when my mate paddled out to his. He went over to investigate and had a chat for awhile. He was repainting the numbers on the buoys! Now that is service.

I service my own mooring and have found that the cheaper [read Chinese] shackles NEED to be replaced every YEAR.

Lots of good info in this thread.

By the looks of the articles posted there will be some new mooring regulations coming out soon.