I expect snorts of derision but does............

Modulation

Modulation

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..........anybody know of a way to fix on a shaft anode without taking the boat out of the water? Or achieving the same effect? I think the current one has fallen off and the boat isn't coming out until May. Would it be effective in the meantime to attach a removable anode to a copper cable, attach the other end to th prop shaft in the boat and drop /forums/images/graemlins/shocked.gifthe anode over the side? Bit like the racing people do?
 
Hanging an anode should work fine. Just make sure it hangs in roughly the right position. It needs to be line of sight and as close as possible to what it is meant to protect, in order to be most effective
 
Diver; otherwise the dangler ought to work, but bear in mind only the shaft/prop will be protected, as with all shaft anodes. To protect the P bracket/rudder stock they need to be wired in too.
 
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Hanging an anode should work fine. Just make sure it hangs in roughly the right position. It needs to be line of sight and as close as possible to what it is meant to protect, in order to be most effective

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It does not need to be line of sight at all, it is making an electrical circuit through the water line of sight has nothing to do with it, salt water has very low resistance so even the distance is not that critical either unless of course you are placing it 10's of meters away from the shaft.
 
Are you sure about that?

I often heard the line of sight argument and on my boat it seems to be true, but I just don't know. It may be an old wives story so it would be interesting to find out the definitive answer.

Do you have more information?
 
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Are you sure about that?

I often heard the line of sight argument and on my boat it seems to be true, but I just don't know. It may be an old wives story so it would be interesting to find out the definitive answer.

Do you have more information?

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Yes, I'm absolutely positive.

If it required line of site for CP to work, how would pipelines be protected, the anodes can not see the pipe they are normally buried some distance away, the two important factors are 1) your anode is bonded to your shaft, and 2) the electrolyte (the sea) is conductive, the higher the electrolytes resistivity the more anode you will need. obviously if you have a large steel hull in the way then it will have an effect, but a wooden or grp hull would have very little effect on the flow of current.
 
being able to "see" the parts to be protected does not mean line of site, they mean electrically see not physicaly.
 
you'll be aware of International Corrosion Society notes then.

http://www.nace.org/nace/content/technical/ctw2k3minutes/stg05/tg284minutes.htm

"If compartments are present then anodes need to be in each compartment to provide line of sight coverage. Perhaps a cautionary note is appropriate."

I'm willing to be convinced, but the experts who sell anodes to commercial and non commercial boat operators seem to think it's a good idea.
 
The document in question relates to CP in steel water storage tanks which although the principles are the same, the application in this instance is entirely different, in the case of a storage tank all the corosion current is contained in the sealed vessel, so introducing baffle plates will have a big effect on the flow of electrons, it is not the same as attaching an anode to the exterior of a wooden or grp boat to protect your propellor/shaft, if your hull is metal than it will have some shielding effect, but the amount of shielding will be determined by the size of the anode and how good your hull coating is.
 
Puzzling, they use "compartments" as well as "baffles", so maybe compartments divides the tank more completely than mere baffles and hence need anodes everywhere. Not sure a paper that loads of experts were debating the wording of is best evidence of though.

Also puzzling why Duffs used ´"see"´ rather than just "see", if you see what I mean....

/forums/images/graemlins/confused.gif all round really...!
 
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Also puzzling why Duffs used ´"see"´ rather than just "see", if you see what I mean....

/forums/images/graemlins/confused.gif all round really...!

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That is because it is an implied "see" rather than a literal see
 
you can do a fairly simple experiment to prove it if you want, all you need is a steel nail, a piece of aluminium foil, a block of wood ,a bucket of salt water and a good multimeter,

stick the nail on one side of the piece of wood, and put a piece of aluminium foild on the opposite face of the block, probably a couple of inches square, and place it so that its top edge is level with the top edge of the nail, now stand the block of wood in a bowl or bucket and fill it with salty water so that most of the nail and aluminium is submerged, now using your multimeter check the current between the nail and the aluminium, you should get a small current flow proving that they do not need to "see" each other.
 
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