killick
New member
Advice to a recent tread indicated that only dissimilar metals should be connected to an anode.
The shaft anode makes sense but what is the hull anode doing?
The shaft anode makes sense but what is the hull anode doing?
what is the hull anode doing?
Being connected, via an internal wire, to the shaft. Usually via a bolt on the gearbox, assuming there's no rubber components in the drivetrain which would insulate it.
If there's no such wire, then the anode isn't doing anything
Pete
VicS, you seem to know about these things, in a non-metal boat would it not be best simply to have one anode attached to the prop and shaft, like a cone.
VicS, you seem to know about these things, in a non-metal boat would it not be best simply to have one anode attached to the prop and shaft, like a cone. Assuming a standard drive train (no funny saildrives etc) with perhaps a 'rubber' isolator somewhere up the line for vibration control (?an aquadrive). Why do we tend to have them sitting at the side of the hull somewhere attached by a wire? I have heard pros and cons to bonding through-hulls etc. Sometimes I think I understand it and then I glaze over again and magical galvanic currents confuse my brain.
A number of boats in our yard have exactly that. A shaft anode or two and nothing on the hull.
We have a saildrive, which has one anode on the leg to protect it and another on the prop to protect that (the two are electrically isolated as a side-effect of some rubber shock-absorbing arrangements). No hull anode needed or fitted.
Pete
If it's a Yanmar saildrive you probably also have a third anode on the raw water inlet near the sea cock.
A number of boats in our yard have exactly that. A shaft anode or two and nothing on the hull.
We have a saildrive, which has one anode on the leg to protect it and another on the prop to protect that (the two are electrically isolated as a side-effect of some rubber shock-absorbing arrangements). No hull anode needed or fitted.
Pete
VicS, you seem to know about these things, in a non-metal boat would it not be best simply to have one anode attached to the prop and shaft, like a cone. Assuming a standard drive train (no funny saildrives etc) with perhaps a 'rubber' isolator somewhere up the line for vibration control (?an aquadrive). Why do we tend to have them sitting at the side of the hull somewhere attached by a wire? I have heard pros and cons to bonding through-hulls etc. Sometimes I think I understand it and then I glaze over again and magical galvanic currents confuse my brain.
I was wanting to make my own bronze fittings just for fun. I have a lot of copper as I am removing my central heating system due to installing insulation.
It's the tin that is the expensive component, even with today's inflated copper prices. Casting bronze is quite tricky because the tin oxidises and forms a skin against the air. Phosphorus and/or zinc are added to the mix to take out some of the oxygen. When casting bronze the molten metal is poured without moving the ladle, which allows it to pour through the oxide 'tube'. You will need a pretty good heat source as copper melts at almost 1100 C.
Advice to a recent tread indicated that only dissimilar metals should be connected to an anode.
VicS, you seem to know about these things,
So, essentially the only thing we are concerned about is the propshaft and prop. The through-hulls can take care of themselves as long as they are made from a suitable material. Then comes the other magic of the galvanic isolators. If your through-hulls are not bonded, your anode is on the prop shaft and the prop shaft is isolated from the engine, do you need one?
Is there a way you can detect if one is necessary? Can you pick up the galvanic differences with a multimeter? If you were starting from scratch is there some way you could avoid the need for an anode at all, such as the bronze prop shaft Tranona mentions. I was wanting to make my own bronze fittings just for fun. I have a lot of copper as I am removing my central heating system due to installing insulation.
Unless your boat is made of Zinc, wouldn't all other metals be dissimilar?
I looked up the Galvatest idea. It looks interesting but I would not really use a bit of kit that required set-up each time. It could be an interesting project to work out how a sensor could be permanently mounted to monitor things. There is the potential for some kind of alarm or disconnection device if there was a significant galvanic current or if the anodes were no longer working. Just an idea and probably more geeky than practical.