We have heard that because our boat is only timber and admiralty bronze rudder and prop we don't need typical anodes as there the is no steel in the water.





Ou

r steering column to the rudder is stano but that's it.

Advise?

So your boat has no fasteners then?

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lydia said..
So your boat has no fasteners then?

Zephry asked a simple question!!

Just maybe you could have answered his question with a straight forward answer instead of your smart arsed comment!!

Years ago I saw an oregan planked yacht sink at It's mooring because a bronze thru hull literally fell out of the rotted planks which became affected by electrolysis. Find a shipwright, even by phone most will give you 5 minutes for free, ask a shipwright the question. Fit anodes....unless you timber is fully encapsulated, i.e. saturated, in epoxy, in which case the boat effectively becomes fibreglass. THEN, you wouldn't need anodes providing the were no dissimilar metals under the water.
The sea is a gigantic electroplating bath and sacrificial anodes should be fitted to timber boats. It's not like they cost much money.
You choose.

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brianlara3 said..
Years ago I saw an oregan planked yacht sink at It's mooring because a bronze thru hull literally fell out of the rotted planks which became affected by electrolysis. Find a shipwright, even by phone most will give you 5 minutes for free, ask a shipwright the question. Fit anodes....unless you timber is fully encapsulated, i.e. saturated, in epoxy, in which case the boat effectively becomes fibreglass. THEN, you wouldn't need anodes providing the were no dissimilar metals under the water.
The sea is a gigantic electroplating bath and sacrificial anodes should be fitted to timber boats. It's not like they cost much money.
You choose.

Never had anodes on "Nacooma" a river red gum planked sloop and there were no problems at 40 years old when I sold her. In fact, without anodes plating the antifouling with zinc I got great life out of the paint on the prop. There was an anode in the frig condenser but it never needed replacing. Had some pit corrosion in the shaft after 30 years.

Maybe I was lucky.

Cathodic protection can also be important dependent on where you keep your boat. Old harbours with a lot of metal on the bottom, marinas with earth leakage, a steel trawler in the berth next to you etc etc.

I always think some protection is important and you also can have too much. Nevertheless copper and bronze is lower on the electrolytic scale than many metals so it's wise to examine the issue.

My opinion is yes.
Remember you have a prop shaft as well - probably stainless steel of some sort. So you already have, in the water, two or three different types of metal. The prop shaft and the propeller and the rudder shaft and the rudder are in physical contact with each other and are different metals and have an electrolyte (sea water) surrounding them. That means a potential for corrosion.
I have a similar situation on the timber yacht I built so at anchor I always connect an anode to the prop shaft and hang the anode in the water.
All is well so far after 5 years - that is no corrosion anywhere that I can see.

YES, YES, YES!!

You have everything mentioned above plus a steel shoe running along the keel.

We have a very similar boat and we have shaft anode, two on the shoe aft and two on the shoe fwd. And all of them are about half gone every year and are replaced accordingly

Yes that boat needs a couple of teardrops just ahead of the propeller. Bronze straps joining the tear drops to the shoe and the rudder flange at the top. The rudder could probably do with one bolted through as well. the rudder has some pink spots already. There is a hole there where there was probably an anode previously. Just don't mount too many.

have had my boat 20 years no anode it is a yacht no steel shoe fastenings don't matter they are copper or bronze 40 foot steel shoe 4 anodes on shoe 180 mm teardrop with strap weld bolts to shoe if these are not wearing after 12 months (next slipping ) remove 1 at a time until wearing
TO MANY ANODES AS BAD AS NOT ENOUGH

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Lazzarae said..

lydia said..
So your boat has no fasteners then?

Zephry asked a simple question!!

Just maybe you could have answered his question with a straight forward answer instead of your smart arsed comment!!

I thought it was a pertinent question, and if the answer was so simple why didn't you answer it, and I agree anodes really should be fitted even if they only stop minor corrosion on the shaft, rudder and prop, it's cheaper to replace anodes than it is to replace the other parts.

Is it true that if there are no anodes a bronze prop will 'dezincify', if that's a word ???.

Anodes? Yes or you can hang them over the side by clipping to a metallic part of the boat.

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samsturdy said..

Is it true that if there are no anodes a bronze prop will 'dezincify', if that's a word ???.

Yes. That's the slightly pink bits on that rudder above. On a propeller it is more dangerous and you can have blades dropping off!

Hi l believed l had a basic understanding of electrolysis and anodes ,but there's been 3 comment's that make me think otherwise. how can to many anodes be detrimental ? wouldn't it mean that they just last last longer ? looking forward to learning more .

There a lot of variables with this debate.
for instance boty moors well up a creek pretty much by himself so fairly isolated electricially.
a near by marina was nicknamed the Lota creek electroplating works because of the huge amount of earth leakage from an old electrical installation.
Iron debris on the bottom can also change the equation.
also seemed to be less of a problem before everyone plugged into 240 volts for battery chargers and fridges.
Poor quality skin fittings dezinc more than others.
So depends on where your boat is and what the electrical set up is.
Every boat will have a different answer.

Actually take back what I said, it would be interesting to test where Boty moors as there is some industrial plant which would be huge user of electricity across the creek downstream.

It depends a lot on where you are operating and the type of water. Fresh water may require aluminium blocks. Salt water there are various grades of zinc and different additives with the zinc. I disagree with Lydia about the 240 volt leakage. 240v is fairly safe as far as electrolysis goes, the real danger is 12v leakage and I would always ensure the batteries are isolated when leaving a boat but would keep 415/240 volt shore power connected. Wooden boats in particular with bronze fasteners and a constant moisture content in the timber have to be guarded.
There are specialists that can carry out tests and advise how many and the type of anode to use but I think the best method is to watch what others do and monitor their boats over a few years. In Zephyr's case loiter about some slipways and see what the fishermen use on trawlers. Check on boats as they come out of the water and see if the anodes are depleted. If they look new then they are just a waste. Keep an eye out for people who paint over the anodes so they last longer! Ideally you are looking for about half the material remaining when you slip next.

Few weeks back when we sailed the mates 42 foot aluminum yachts down from Sydney she was on a swing mooring in Lane Cove with anodes hanging in the water on SS wire. The tear drops were covered in several years worth of marine growth but still as new! They were a few feet from anything and obviously not doing anything. There are books on the subject but I can assure you it's as boring as bat****.

I should add that with my own yacht I only have one anode. Prop shaft anode that looks after the propeller, bronze folding on a SS shaft. The only other bits to worry about like the skin fittings are covered in paint and isolated by rubber hoses.

most of our well maintained wooden yachts run no anode or a anode on the prop (i do and forgot to mention that ) over protection is the same as under protection you still have a current just in the opposite direction
mahogany yachts are often a worry as they seem to set up a current of there own (my guess is acids in the timber forming a battery with the metal) especially in the presence of iron luckily these aren't common boats in aus this is evidenced by wasting of the timber around the fastenings
steel shoes on trawlers and motor boats are a great source of electrolysis with the copper and steel forming a battery
the biggest problem is usually poor electrics batteries left on and if you are on a marina and someone else has bad electrics they are also your problem part of the joy of being up a creek no neighbors

Zephr bear with me ...... good grief theres a lot of old wives tales and waffle about this one.....

Imagine a 12V battery in the boat with a wire from its positive terminal hanging in the water at the stern and a wire hanging from its negative terminal hanging in the water off the bow.

A current will flow between the two through the salt water removing metal from one of them and adding it to the other (depending on which one is connected to negative and which one is connected to positive) commonly called corrosion. Its called electroplating if we want to do it.

The rate the metal is added/removed can be predicted by the "metal activity" of the material of the wires above (copper). Say for example we want to stop the wire at the stern being corroded (ie your prop). What we do is attach a piece of zinc to it. Because the zinc is more reactive than the copper the current preferentially passes through that ignoring the copper. Bingo we have made an anode!!! (Because it corrodes faster than the copper its called sacrificial).

Zephr in the case of your timber boat. For corrosion to occur a current has to flow out of some metal item passing out of your hull into the water and back into the boat through another. If you have only prop passing into the water and nothing else the stories are probably right (and confirmed in practice by Boty), you dont need an anode because there's no in and out.

But if under your waterline you have a radio earth plate, or metal fasteners + the inside of the hull/timber is damp there could be current flowing into the water via there and back out of the water via the prop. in which case you might need an anode on the prop/prop shaft.