[Mike Dixon]

As many know, I’m in the process of restoring “Atalanta” – A1.  One of the many many issues I need to resolve is that of what I loosely call Cathodic Protection.  One of the major tasks has been to replace engine and stern gear – a major, but necessary, expense.  Not unsurprisingly, I’m keen to protect them.  It seems there are three options –

a) do nothing (which seems rather short-sighted),

b) fix an anode to the hull adjacent the propeller, or on the shaft (which is relatively easy and what I have done with two other boats from the  Atalanta family,

c) go the whole hog and install an anode and elecrically bond it to the stern tube and engine (which is entirely do-able, but will take precious time and some expense)

Just one other consideration – A1 will be berthed on a drying (to mud) berth, far away from stray electric currents from boats coupled up to shore power.  She will not have shore power.

 

Any thoughts gratefully received.  Thanks – Mike

Topic

[Nick Phillips]

Mike. I am glad you have asked this question as I am going through a similar thought process myself.  I believe that the recommendation for Atalantas is to bond all of the submarine metalwork – seacocks, keel steelwork, engine, shaft and prop -together with wires and connect to an anode. (Although I cannot at the moment find the article I think I have read that describes this – if anyone know will let me know I will improve the website indexing).

Helene, as I bought her, has a soft anode but no bonding between the various items.  And she chewed up the new shaft anode last year in less than a full season.  So I am looking at applying the internal bonding and perhaps adding a hull mounted anode in addition to the shaft anode.

One additional question.  The talk of stray currents from other boats on shore power.  I had previously thought this is only a problem if your boat is also connected to shore power, when you should fit a galvanic isolator. If you are ‘off-the-grid’ you should not be affected?  I wonder if my experience last year proves this assumption to be false. I spent about 6 weeks in a marina, not connected to shore power, but where there were rumours from other Atalanta owners that the pontoons I was on were known for electrolysis issues due to their proximity to a large steel lightship-clubhouse.

It would be great to hear others’ opinions on what bonding / protection should be applied to an Atalanta and also whether shore power connections impact the situation. Nick

 

[Mike Dixon]

Thanks Nick for your input.

The electrical bonding solution seems to me to be the way to go.  The three books on boat electrics all seem to advocate this approach as do a couple of magazine articles.  I must admit that I hadn’t come across the inclusion of sea cocks, but it does seem to make sense – but I wonder that if the sacrifical anode is at the after end close to the propeller, will that self same anode also protect the head’s sea cocks 20 or more feet away?

 

I look forward to getting further views.  Once I have made up my mind on what solution to adopt, I’ll let you know.  I must say though, that my knowledge of the physics involved just about copes with the elecrical bonding solution, but eyes start to glaze over when stray currents, lightships and galvanic isolators are introduced.

 

Mike

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