Anodes on GH hull

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grjack
Posts: 12
Joined: Mon August 16th, 2010, 3:32 pm

Anodes on GH hull

Postby grjack » Mon August 16th, 2010, 3:52 pm

I am new to this, and I apologise in advance if I am at the wrong place or am using the incorrect etiquette.

I have just purchased a Golden Hind and the previous owner has installed 2 fish anodes on the hull underneath the cockpit on each side of the keel, securing them using drilled holes right through the hull with nuts and bolts. There are two flat thickend wooden soles on the hull that seem to suggest that the anodes belong there, but I am quite concerned that holes right through the hull are meant to be drilled here. I worry that the water may get between the wood and the cascover and its downhill from there ?

Thanks
gary

Athaena
Posts: 63
Joined: Wed July 22nd, 2009, 12:36 pm

Re: Anodes on GH hull

Postby Athaena » Mon August 16th, 2010, 6:41 pm

Hi Gary,

I think you've posted in exactly the right place :D

I'm no expert either but having the anodes fastened through a wooden hull definitely sounds wrong to me. Are there any connections from the anodes to metal parts of the boat? I would expect the anodes to either be bolted to the metal parts likely to corrode or to be electrically connected to exposed metal parts by a connecting wire.

On Athaena (very similar to a GH) I have a couple of anodes, one disc anode through bolted to my metal rudder and a small shaft anode around the prop shaft. These are my only metal components in saltwater.

I'd be tempted to remove the anodes you have and fill the holes with plugs stuck in with thickened epoxy and then cover both sides with a layer of glass cloth and epoxy. If you're not familiar with using epoxy resins have a look here. I'd then gather some opinions and fit some new anodes based on the consensus. I would expect either to have an anode on each isolated metal structure in contact with seawater, or to have a single anode electrically connected to each metal structure in contact with seawater.

Hope that helps, I've found the best approach is to ask as many people as I can and from the various answers I get I'm usually able to put together a solution I'm happy is probably right. :D

Chris

grjack
Posts: 12
Joined: Mon August 16th, 2010, 3:32 pm

Re: Anodes on GH hull

Postby grjack » Mon August 16th, 2010, 7:23 pm

Hi Chris,

Thanks for the prompt reply.

I am now concerned. I did ask the last owner about this and he said that the anodes had been attached in this way when he got the boat, he just redrilled the holes. I do have another anode on the prop shaft. All the electrics(motor etc) on the boat are earthed to the metal bilge keels and to those two fish anodes. The boat did take water when it went back into the water, and that is the only place that I could think of that shipped the water( the sea toilet cocks were checked and that was OK).

PS : speaking of NOT drilling holes in a hull, where did you mount your transducer ? I saw a thread where you discussed this but could not find the actual reference to that positioning.

Many thanks.

It is good to know that I am not alone in these matters :)

Gary

chris s
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Joined: Sun March 5th, 2006, 6:55 pm
Location: Netherlands

Re: Anodes on GH hull

Postby chris s » Tue August 17th, 2010, 8:52 am

Personally I would fit an anode to each of the metal bilge keels (as well as the prop & rudder) you may then be able to earth everything to the bilge keels,
& then fill the original holes as suggested by Chris. :D

grjack
Posts: 12
Joined: Mon August 16th, 2010, 3:32 pm

Re: Anodes on GH hull

Postby grjack » Tue August 17th, 2010, 11:53 am

Hi chris s

I will plug those holes. I suppose I will have to get it back on land and let it dry out first.

thanks
Gary

Athaena
Posts: 63
Joined: Wed July 22nd, 2009, 12:36 pm

Re: Anodes on GH hull

Postby Athaena » Wed August 18th, 2010, 6:09 pm

Ahh if things are 'earthed' to the anodes you may well be OK (I presume you mean there are earthing wires going to the anodes?), you just need to ensure that the connections and wires are sound and that everything that needs to be connected is.

I wouldn't worry too much about the boat taking on water, as long as it's not too much. There is always going to be some seepage through joints etc especially if she's been out of the water a while.

I'm afraid my transducer involved cutting a whacking great 52mm hole through the hull just aft of the front of the keel on the starboard side. I used a fairing block on the outside (my transducer needs one) and a large backing block on the inside.

Chris

grjack
Posts: 12
Joined: Mon August 16th, 2010, 3:32 pm

Re: Anodes on GH hull

Postby grjack » Wed August 18th, 2010, 10:05 pm

The boat had been out of the water for over two years, so that could explain it shipping some water. I may just monitor it and see if it settles before I think of hauling it out again. Thanks again for the answers.

The transducer problem is one of the few downers about wood in my eyes. With GRP I believe that you can just attached it to the inside of the hull, no problem.


gary

chris s
Posts: 135
Joined: Sun March 5th, 2006, 6:55 pm
Location: Netherlands

Re: Anodes on GH hull

Postby chris s » Thu August 19th, 2010, 12:34 pm

I think if you earth all the keelbolts together or fit a seperate dedicated earth bolt to each keel

(to both bilge keels and the ballast keel if it is not encapsulated and is exposed to sea water )

Then with an earthing strap you can lead out to anything else that needs connecting, such as the motor, gearbox, propshaft, rudder etc,

You can either weld or bolt the anodes onto the metal bilge keels,

Please dont forget to check the continuity from anode to earthing strap with a multimeter or similar

grjack
Posts: 12
Joined: Mon August 16th, 2010, 3:32 pm

Re: Anodes on GH hull

Postby grjack » Fri August 20th, 2010, 1:49 pm

Good info.

Thanks once again.

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Fiddler's Green
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Re: Anodes on GH hull

Postby Fiddler's Green » Wed December 8th, 2010, 12:35 pm

I have had an anode under my wooden hull, a pear shaped one, for the last 20 years. it is through bolted with galvanised bolts and sealed with sikaflex. I have replaced the anodes about every 5 years when they are about half eroded.

I have the bolts on the inside of this anode connected to the engine earth from one bolt and to the prop shaft with a metal strap resting on the shaft to ensure connectivity. These protect the prop. You could fit an anode to the prop shaft, but most MG designs do not have room for that. Some do connect the main keel too but often the keel bolts do not electrically connect due to the sealants used to protect them.

I have a pair of anodes on the bilge keels too, these last about 5 years too.

Contact MG Duff they have a website and give lots of examples.

correctly fitted through the hull with a good sealant and you ashould never have a problem.

Hope this helps
John
Proud owner and builder of 'Fiddler's Green'


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