'Anode'

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Ardenfour

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My recently purchased boat came with this attached to it's bottom. It's a flat bar around 350mm in length. I removed it with the intention of replacing it prior to launch but time ran out (and I balked at the £115 price I was quoted for a new one at a famous Glasgow swindlers)
I have no idea how long it has taken to reach this sorry state, but clearly it has been working. I did manage to fit a new anode to the propshaft, that one was in similar condition.
The boat has now been afloat for 2 months sans big anode. How worried should I be? I have a 3kg pear shaped one, would it be worth it hanging it over the side on a length of rigging attached to the engine?
 
Ardenfour said:
My recently purchased boat came with this attached to it's bottom. It's a flat bar around 350mm in length. I removed it with the intention of replacing it prior to launch but time ran out (and I balked at the £115 price I was quoted for a new one at a famous Glasgow swindlers)
I have no idea how long it has taken to reach this sorry state, but clearly it has been working. I did manage to fit a new anode to the propshaft, that one was in similar condition.
The boat has now been afloat for 2 months sans big anode. How worried should I be? I have a 3kg pear shaped one, would it be worth it hanging it over the side on a length of rigging attached to the engine?
Click to expand...

what is the big anode intended to protect ? What is it bonded to?


Just bonded to the engine block to provide back up to the shaft anode? If so don't worry about it unless you find the shaft anode is consumed at an inconveniently rapid rate.
 
Well, checked the anode wiring today and it's only connected to a bolt on the engine crankcase, so am I correct in thinking it's supplementing the engine internal anodes? I didn't check for continuity between the shaft and engine, but I don't see a flexi coupling so shaft anode would be part of the same circuit?
 
Ardenfour said:
Well, checked the anode wiring today and it's only connected to a bolt on the engine crankcase, so am I correct in thinking it's supplementing the engine internal anodes? I didn't check for continuity between the shaft and engine, but I don't see a flexi coupling so shaft anode would be part of the same circuit?
Click to expand...

No an anode on the outside of the hull is doing nothing in the way of protecting the engine internals or supplementing the engine anodes.

It sounds as though its just giving back up to the shaft anode. Presumably located reasonably near the prop. If/when you decide to refit it check the continuity from it to the prop and shaft
 
Ok, that's interesting. I think I need to read up on some 'principles of anode protection', can't quite get my head round this. If several anodes are connected together electrically, do they not all perform the same function irrespective of their physical location (all in water, obviously) ?
The anode I removed is very close to the prop, mounted on the small section of keel where the shaft exits the hull.
 
Ardenfour said:
Why would it matter whether the anode was close to the prop?
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To be effective an anode must be reasonably close to and have "line of sight" of what it is intended to protect.

An anode at one end of the boat will not be effective in protecting something at the other end nor will it be effective in protecting something shielded from it, by being on the other side of a keel for example.

There must also, of course, be a good electrical connection.
 
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Ardenfour said:
My recently purchased boat came with this attached to it's bottom. It's a flat bar around 350mm in length. I removed it with the intention of replacing it prior to launch but time ran out (and I balked at the £115 price I was quoted for a new one at a famous Glasgow swindlers)
I have no idea how long it has taken to reach this sorry state, but clearly it has been working. I did manage to fit a new anode to the propshaft, that one was in similar condition.
The boat has now been afloat for 2 months sans big anode. How worried should I be? I have a 3kg pear shaped one, would it be worth it hanging it over the side on a length of rigging attached to the engine?
Click to expand...

This is a common anode on Nicholson yachts. My view is that if it has wasted away it is doing some good. The price for MG Duff part is eye watering however there are cheap ones on the Internet. If you want to go even cheaper you can buy the anode bar in a 6 ft length and then cut and drill to length, worth doing of there are a few Nic owners willing to get together and you can get the drilling done.

Yoda
 
yoda said:
This is a common anode on Nicholson yachts. My view is that if it has wasted away it is doing some good. The price for MG Duff part is eye watering however there are cheap ones on the Internet. If you want to go even cheaper you can buy the anode bar in a 6 ft length and then cut and drill to length, worth doing of there are a few Nic owners willing to get together and you can get the drilling done.

Yoda
Click to expand...

IT does not necessarily follow that wasting away of an anode shows that it is doing any good. Plenty are fitted where they they are probably not necessary but they still waste away. OTOH if an anode is not wasting away it is certainly not doing any good!

Zinc anodes should be made of a grade of zinc conforming to MIL-A-18001K

Cadmium . . . . 0.025% - 0.07%
Copper . . . . . . .0.005% Max.
Iron . . . . . . . . . 0.005% Max.
Lead . . . . . . . . .0.006% Max.
Aluminium . . . . 0.1% - 0.5%

Ensure cheap internet purchases conform to this


Note in particular the very low iron content and the cadmium content.

The correct grade zinc bar is available.
 
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