Adding shock to mooring chain

[wcarpenter]

Hi all, this is my first post; seen so much good advice in past I hope I can get some. My new (to me) 33 ft fin keel boat will soon be going onto my own swinging mooring. The mooring is in a tidal channel quite close to a sand bank. In order to keep the boat away from the bank and aflot in particular wind conditions the mooring chain needs to be short. The problem with this is the stress imposed on the boat and chain.
I am considering the use of shock cord wound through the links of part of the chain. This I hope would absorb some of the shock load. Has anybody any opinions/experience of this please?

 

[npf1]

a rubber mooring compensator? BTW - I have a couple spare (new) if you decide to go that route.

 

[fiddle]

The very heaviest chain you can source / afford. Shock cord will wear, even if you can get sufficient strength, but heavy chain will be its own shock absorber. Also think very carefully about your ground tackle. A heavy sinker with some (more) heavy chain and two or three "anchoring devices" spread out to stop the sinker being pulled off station. I say "anchoring devices" because you dont need the stuff that you would carry on your forepeak. Have some made up from steel from your local scrap man.

 

[wcarpenter]

A length of very heavy chain that will mainly rest on bottom is the usual and best answer, but in anything over a force 6 from the north the extra length puts me on to the bank. This was not a problen for my last boat but I do not like the idea for my new one.

 

[fireball]

No chance of moving the sinker north a bit?

 

[Guest]

Sounds like you have the \"Booby prize\"

Many clubs have a mooring that is "iffy" and most members don't like to use it ...

Hill Head club had one on the edge of the channel next to the sluice gates ... if boat didn't settle right .. she laid over at alarming angle ....

Tudor Club had a couple that were on very hard ground and lads could walk out to the boats at will ...

The above are not the fault of the clubs - but natural occurrences. Most clubs have some like it ...

Sounds like you have one ... To be honest - IMHO if you are needing to add "safety" to the mooring to stop grounding / factors that should normally be avoided - you have the wrong mooring and should request a change. Often there are smaller more suitable boats in a club that are better suited in a change ... but of course you then get the others saying Why should I change etc.
I've seen instances of small Cuddy boats on deep-water mooring in same club as a 30ft fin keeler dancing with shallows ... swap em round and fin keeler is now safe and happy ... Cuddy guy still afloat and able to use boat ... but refuses.

Shock cord is a waste of time IMHO. I would think that increasing ground chain size and also increasing size of riser chain ... to gain more inertia in the system.
Maybe a request to club or HM (depends who controls your mooring) for a resiting of the sinker ?

Shortening chain is a disaster waiting to happen ... normally a ground chain should = tide rise and fall, then swivel joining an equal length of riser chain = tide rise and fall. This makes an average mooring rode of 2x tide rise and fall ... (that is normal spring tides .....) Less than that and you start to exert extra force on the system ... increasing as the rode is shortened. You also start to change the riding angle again increasing the force applied.
In normal circumstances a ground chain should not lift unless weather is increasing to bad conditions / tidal influences are strong.
My last swinging mooring carried my heavy 25ft Motor sailer on :

14ft of 1" ground connected to 3/4 ton concrete sinker. Ground chain to swivel and then 14ft of 1/2" riser ... then 3 10mm strops to different strong points on bow.
Harbour board rec'd mooring was :
12ft 3/4 ground, swivel, 12ft 3/8 riser with freeboard length suitable strop.

My boat stayed in place !! judging by the mud marks when tide was out - the ground chain rarely moved and I was in exposed Langstone Harbour.

 

[oldsaltoz]

You could add a car tyre as a shock absorber, wait for a low tide, add 2 lengths of chain to the mooring chain and run them around the tyre, leave a loop in the mooring chain (shortening the chain).

Doing it at low tide will avoid it marking your bow. as well as keeping it out of sight. not pretty but it works.

 

[Parashandy]

Stainless anti-snatch springs can be bought for about £10 - £15 (old money to you) each and are easily shackled to the riser. Try the large size and use two in parallel if you feel it necessary.

 

[Guest]

Add Stainless to a mooring chain ?????

Sorry but I have to comment that I think that not a good idea in Stainless Steel ........

Dissimilar metals

Stainless steel gives no indication of failure till it breaks.

Recc'd material for mooring chain and items is all galvanised or all black metal. If failing that - then straight mild steel. Reason is that all corrosion / weaknesses are plain and not hidden .... you see wastage of the metal etc.
You can "reset" mild by throwing it into the bonfire ... etc.

 

[John_Clarke]

Nylon rope shock absorber

In addition to the chain from the swivel on top of the Hippo buoy to the boat, I have a length of shock absorbing nylon rope which is attached to the chain near the swivel and the other end is attached just clear of the bow roller. The rope is 20% shorter than the chain so it takes the strain until fully stretched.

To reduce the amount the the chain twists (with the rope around it) I have fitted the chain inside a pvc tube which is held tight to the chain at each end with cable ties. In light wind over tide conditions when the buoy can pass close to the bow (and duck between the chain and the bow) this creates a twist in the chain. The tube reduces this and transfers enough torque to turn the swivel. Usually no more than one turn develops.

My first nylon shock absorbing line on our 33' yacht was an 8 mm climbing rope but this broke after about 4 seasons. It showed signs of hardening and the fibers were fused together in places. This season I will try 10 mm 3 strand nylon.

I don't know if the above is any help to you, but I agree with the others that a better solution, if possible, might be to get another mooring location. I sympathise, it is not a good feeling when your boat is too close to a sandbank!