Refurbishing my mooring.

[Quandary]

OK I know some of you will tell me to do a back search for answers but I like to share and discuss my problems so I will try asking anyway. I 'came by' a mooring in front of my home in Loch Gilp. Formerly used by a 12m sea angling boat it was reputed to be in good order but I had no idea what was down there but with the help of a workboat and a diver it has all been brought ashore and now having separated it all, my driveway looks like preparations for the launch of the Titanic.
What I want; A reliable summer swinging mooring laid in about 3m. LWS. well out in Loch Gilp for mainly spring and autumn use for our 33' 5 tonne disp. yacht. As it is the first one most visitors come to it will be subject to a occasional overnight use by bigger boats in summer. Loch Gilp faces south in to Loch Fyne, there is shelter from a reef and a pier but in strong South Easterlies a big rolly swell comes in and the boats pitch heavily. I can mark it 5 ton but that will not discourage some of the big ketches which come here.
What I have recovered - two about 40kg. Bosun (heavy cast fisherman type) anchors in good condition, a third fisherman anchor, about 20kg. some corrosion.
6m. of heavy 30mm. stud link chain in good order. three 15m. lengths of 1/2" plain long link chain, all with some wear, perhaps only 25-30m. usable. 15m. of 10mm. long link chain, (riser) swivel still in quite good order. A rope strop and a 8mm. galv, chain strop. About 10 big (16-19mm.)shackles half of them usable. I also have about 10m. of 12 mm. long link in the garage in good condition.
What I propose to do; Throw or give away the light fisherman. Join the 6m. of 30mm. studlink to the 10m of 12mm. as ground chain and put a Bosun on each end. Shackle on about 10m. of 1/2" long link riser to a 600mm. OD netbuoy and make up a new rope strop.
Comments - I am advised that about 2 boat lengths of ground chain is enough,subject to weight? that the riser should not be longer than half the ground chain so that it can not drag over the top of the anchor? Since I have so much 1/2" long link is it daft to consider doubling it up between the stud link and the second anchor? I presume the riser should be joined to the ground chain in the middle rather than at the centre of gravity (the 30mm. studlink is massively heavy but sells for £40 a metre, so I am reluctant to invest in more if I can avoid it). Would the heavy chain be better at the middle rather than at the windward end?
Alternative solution, take all the chain down to the slipway at low tide, together with the Belle mixer, a load of ballast and half a dozen bags of cement. Make a pyramid shutter about 1.5m sq. by about 1/2m. deep from old kitchen worktops. Make a concave base with some sand under polythene (worth doing this?) mix concrete add in all the chain except the 30mm. stud link which will be cast in at the top ? Shackle on 12mm x 10m riser, Float out at high tide using raft and sink never to be raised again.
Some of the shackles had grease on the threads which were still sharp and in good condition, (good or bad idea?) others dry had only half the depth of thread left, all were well secured with intact cable ties. The tight fitting shackles on the top of the Bosun anchors are welded and show no wear.
Long time since I owned a swinging mooring so all constructive help or comment very welcome, (I intend to look for local advice too).

 

[dutyhog]

What I want; A reliable summer swinging mooring laid in about 3m. LWS. well out in Loch Gilp for mainly spring and autumn use for our 33' 5 tonne disp. yacht. As it is the first one most visitors come to it will be subject to a occasional overnight use by bigger boats in summer.

Our "summer" mooring at the bottom end of Loch Sween is for a slightly heavier boat and similar seas. It was supplied by FF Hendersons. But the bottom here is hard sand, and yours is probably softer stuff. Two 100kg Samson Mk3 HHP anchors are joined by 14m (1.4x boat length) of 28mm ground chain, with from the centre 3m of 28mm surge chain then 5m of 18mm riser chain to a swivel, then 3m of 24mm nylon rope strop. Most of the BS3032 shackles are welded on. At low tide the riser can't foul the anchors. We drop it for 7 months each year, taking home the swivel etc. I think (ie hope) it's still OK after 8 years. The sea is so clear here that sunlight penetrates easily and things rust quickly.

It's mainly heavier stuff than you've got hold of. I'd worry about the 12mm as ground chain, even if doubled.

We also have a massive concrete block mooring at the sheltered NE end of the loch, sunk well into mud, which we use more of the year, especially in NW gales. Even though it's very heavy chain again, it has got thinner over 5 years, so it's just as well that it can be lifted eventually to replace the riser.

I guess your plan B may be best, but only if you can arrange workboat/diver to have it looked at, and lifted when the riser chain gets thin.

Gordon

 

[alahol2]

My mooring, at the top of Portsmouth harbour so possibly more sheltered, has 2 x 50 Kg anchors at the windward end and 2 x 30-40 Kg anchors at the other with 15m of 1" studlink groundchain. 3/4" riser chain to LWS then 1/2" riser to the buoys (fore and aft mooring).
Your kit sounds too light to me.
One tip, if you can do it, cut the upper fluke off the fisherman type anchor and re-weld it alongside the other fluke. That way you have got more ground resistance and nothing for your riser to wrap around.

 

[William_H]

Swing mooring

I would say do not throw away the lighter anchor but set it at right angles to the other main 2 on a chain of about 1.5 or more boat lengths. Indeed if you have doubts about the holding power then add yet another anchor opposite the light one. This all will tend to accurately locate the centre of the mooring minimise the movement (wear) and add to the total weight at the centre. Kind of like an anchor angel.
While it is right to have the heavier chain between the primary anchors it is really the riser that has all the responsibility and the wear. So here you need as heavy a chain as possible. Limited by the weight the buoy will hold up. Don't forget a stout swivel shackle in the riser. Again it is the shackles in this part that really matters so mouse them strongly or weld them. The part of the mooring on the bottom will not get so much movement so not so much wear and a failure here will only allow the boat to move until the other anchors take up but a failure of the riser means boat gone.
No I would not go for a concrete block just too heavy and too much weight for not much holding power compared to the ease of managing anchors separately. I don't believer in lifting moorings just dive and inspect. Once down sometimes it is easier to double up doubtful parts than remove the old. But if you have it all out of the water then that is not applicable. good luck olewill

 

[Trop Cher]

I think your six metres of 30mm ground chain could be a bit on the short side.

I had a mooring sized by FPM Henderson (Glasgow) for a 12 metre boat, he wasn't interested in weight as he said it's length and windage that matters. He advised 2 x 60kg samson anchors, 18 metres of 30mm ground chain with another 5 metre of 30mm ground chain tail from the centre of the longer length of ground chain leading to 18mm riser chain.
The 30mm ground chain was quoted at £15 + vat per metre.

.

 

[Quandary]

I appreciate the advice but as often happens it is not really what I wanted to hear.
Sounds like I need to look for a scrap collector to take it all away. If I could find 30mm. studlink for anything like £15 a metre I would keep the anchors but I am not prepared to spend more than the cost of a years alongside berthing in the Crinan for a mooring I would probably use only half a dozen nights a year in summer perhaps for two or three seasons until the wife gets her way and we do our cruising in a camper van.
I am puzzled how I can get away with 8mm. chain and a 15kg. Manson when I go out to the islands but need more than half a ton of anchors and chain to hold the boat at home when it is laid by a work boat and buried by a diver. I suppose it is because the boat is not left unattended for more than a day, but then this mooring is right in front of our windows. (I always fancied the notion of having a home with a private mooring right outside, would it add value to the house in a year or two when we sell the boat and downsize?)
Obviously durability over time is an issue but does the ground tackle wear that much when it is not being used and it is well buried? The old riser was about three times longer than the depth and I suspected that the excessive travel contributed to wear. With only occasional use is the solution to put on a rope and small buoy drop it every time and just pull up when I want to use it? The diver charged £40 and the workboat with creel winch a similar amount so checking once a year is not that expensive.

 

[ffiill]

Concrete blocks-I have made them using shuttering made of sheets of chip board reinforced with 2x2 framing.
Cast it on a trailer if you have one to take the load and cast a piece of heavy chain in middle for eye or buy a forged steel towing eye often used on farm and lorry trailers-just weld on a long bar and some cross bars and cast into concrete block.
If you need a raft consider three upside down "play" rubber dingys suitably secured in a frame-at about £25 each three mid size ones should carry about two tons if turned upside down to take advantage of the buoyancy in the central area.
My block awaits a space at Plockton but my riser is 28mm multiplait Seasteel on which you can hang about twelve tons.
Arisaig Marine uses similar sized nylon risers and concrete blocks for all their moorings.
If you use this no need for a swivel as the multiplait will stand being twisted and turned.
Also worth noting that Crown Estates now insist on annual diver survey for any mooring so like it or not your mooring will get checked annually.
As for corrosion on chain-after I believe about 5 years my 20mm riser is now down to 10 mm in places-ground chain and anchors still in very good condition. Good when you consider that the visitors moorings at Broadford had to be replaced after only one season so I am told.
In Earl Hinz book Anchoring and Mooring there is a load of useful info. on mooring plus data on snatch loads etc.
For example an 8 ton boat like mine in 15 foot plus waves and hurricane force winds can generate a bit over a one ton snatch load-ie the sudden pull caused by a rising wave plus 100 mph plus winds.Therefore 8mm chain stand alone will probably break in these conditions with a breaking strain of a bit under a ton.
As for the weight of concrete blocks The NZ government has some quite strict rules about moorings and you can find useful info. info on how big everything should be-actually less than the above example as I recall.

 

[Quandary]

Thanks ffiill.
I am very interested in the idea of the Seasteel rope riser which is new to me, it would seem to overcome a lot of the wear and corrosion problems and should require a relatively small buoy. It would seem possible even to bring the eye right to the deck cleat with no joins at all, Gaelforce say it is very abrasion resistant and if it is used on trawls tugs and fish farms it must need to be, I will enquire if they would make up a riser as in their catalogue it is offered by the 220m. coil.. Can you splice an eye and cast the bottom end right in to the block or would it be better to cast in an eye of a separate bit of heavier stuff. I presume it would need a tight fitting sleeve at the point it emerges to counter abrasion? Any idea of the expected life span in this use?
Many of the boats here are on concrete blocks and there is a raft of plastic drums for floating them out, they are usually just cast on the slipway with a vee of 30 to 40mm bar cast in to the top to take chain, I presume you need to wait for a couple of days before moving them and I have some old worktops for an easily assembled /dismantled shutter though I think the boatyard has a plywood one somewhere. I have an 8'x4' four wheel 'builders' trailer but that might limit the size and weight but would allow me to cast it all at home and take it down to the slip without causing a temporary obstruction.Putting all the chain into the mix should increase the density considerably. Does forming the bottom with a concave profile over sand or earth make any real difference to the stability?

 

[ffiill]

They will sell the big multiplait by the meter-thats where I got mine-basic polysteel which has a lower breaking strain than Seasteel but what fishfarms usually use..Yes fish farms use it to moor to the big Samson type anchors.I had one as a riser on my mooring on Loch Duich before it dropped a shackle pin.I have the rope which has suffered no more than light abrasion to its bottom end over two years when the boat was permanently on the mooring.
Only one thing-I was not impressed by the cast steel eyes used by Gaelforce to splice the rope around-a bit too cheap and Chinese for me-corroded quite quickly and therefore a weak spot in the system.Drop forged eyes used by the likes of Scottish and Southern for power lines are much sturdier better galvanised if more expensive.

 

[dutyhog]

Also worth noting that Crown Estates now insist on annual diver survey for any mooring so like it or not your mooring will get checked annually.

Can you give us the source of this information? I didn't think they cared. They don't ever tell me anything when I renew the £ 80 fee each year - all I get is the bill. Gordon