Its Anodes again - but slightly different

[Plan_B]

When in Lymington the anode was less than 50% wasted in a year, but I changed it every year - as one does. Now the vessel is in Torbay I note that the anode is about 90% wasted in the year. Some of my boaty neighbours suggest hanging a secondary anode over the stern whilst in port - and others have, they say this helps to reduce the wasting.

I have seen this done before elsewhere but I'm not sure of the reasoning behind it and I don't ow if it needs to be connected to anything.

What does the Team think, please?

Dave D

 

[pvb]

Do you leave shorepower connected? (nm)

.

 

[Plan_B]

Re: Yes but isolated at the RCD (nm)

.

 

[VicS]

Re: Yes but isolated at the RCD (nm)

But that means the earth is still connected.
Do you have a galvanic isolator?

 

[Plan_B]

Re: Galvanic isolator

If I have, I've never found it !

 

[alan]

I hang an anode over the stern at about the level of the fixed anode and in line with the propellor (where the fixed anode is mounted). This second anode is connected by a heavy (i.e. thick) piece of wire to the boats ground (engine and battery negative); you neeed a pretty thick earth wire as the currents involved are very small and you need a minimum resistance in the wire to do any good. I have noticed a big improvement in the primary anode consumption to previously when I did not use a second anode. I have also fitted a galvanic isolator for protecting from stray currents caused by the AC power ground potential differences between my boat and others. You should find the galvanic isolator (if you have one) in the the shore power earth wire between where it is connected to the boats earth; usually near the AC circuit breaker box.
I have connected the hanging anode by using a threaded rod stud and wing nut which protrudes through the deck coaming at an unintrusive place; there is then a wire from the stud to the boat's ground inside the boat, and another wire to the second anode hanging over the side; this makes it easy to remove when one goes sailing ..................... however on a couple of occasions I have forgotten to remove it !!

 

[pvb]

Re: Galvanic isolator

It's likely that you're getting increased electrolytic action through leaving the shorepower cable connected. Suggest you either unplug the cable whenever you leave the boat, or fit a galvanic isolator.

 

[VicS]

Re: Galvanic isolator

Thats just what I was going to say next.

 

[richardabeattie]

Ah knowed that.

 

[Piers]

There is a specific problem with Lymington. A considerable quantity of rain water drains from the New Forest into the Lymington river. Given this is fresh water and therefore less dense than sea water, it can sit on the surface to a depth of up to 18".

Hence, when this layer exists, the sea water anodes are ineffective. A test you can do is see if they have a white deposit on them. If so, you know it's a fresh water problem.

When I was berthed in Lymington this is exactly what happened to me, with the white depsoits etc. Moving to the Hamble, white deposits have gone and the anodes disappear much faster.

MG Duff (anode manufacturer) suggested to me that with the boat in Lymington, it might be worth using fresh water anodes since this is where the boat was spending more than 50% of its time.

However, now I'm in the Hamble, no problems. Just a faster replacement policy!

 

[Plan_B]

Re: Useful information - thanks guys

Thanks for that. There are a few things I can try now.

Dave D