Electrical bonding of rudder.

[mobybill]

I recently replaced the rudder beatings and noticed a slight corrosion on the rudder stock near the hull bearing. I checked that there was no loose wiring touching the rudder system that could make a circuit. I also noticed that there has been corrosion on the p bracket resulting from no earthing due to corroded earth strap. I am in the process of repairing the earth strap and would like advice on whether the rudder stock requires earthing as well. Any advice on whether to install an earth strap to the rudder would be appreciated.

[rxc]

I think someone else has had problems with corrosion on the rudder stock that was caused by a short in the binacle. DOn't remember who, when or what, but there are a lot of energized wires running around there, and a little bit of chafe can make your entire steering system "hot".

[MalcolmP]

Jan 12, 2023 20:52:58 GMT rxc said:

I think someone else has had problems with corrosion on the rudder stock that was caused by a short in the binacle. DOn't remember who, when or what, but there are a lot of energized wires running around there, and a little bit of chafe can make your entire steering system "hot".

You are correct as always RXC, it was a Sun Odyssey 45 that lost its rudder due to the compass light in the binnacle grounding onto the rudder stock.

Full report is here: www.jeanneau-owners.com/hintsandtips/so45rudderloss.html

Malcolm

[rxc]

Malcolm,

Thanks for the confirmation. Both of the event and that I still have some functioning memory cells.

Had a nice cruise thus past week down to Palm Beach and back. Terribly cold at times - down all the way below 60F a few nights. But we are tough, and have 3 large cats aboard for warmth.

Ralph

[Trevor]

Hello Mobybill,

To bond or not to bond is a choice made by manufacturers based on what risk is preferred.

When metal sits isolated underwater it cannot create a “cell” with other dissimilar metals. It is doesn’t have a way for galvanic currents to flow to other metals. It does have the disadvantage that if any voltage is accidentally applied to that metal, electrolysis will destroy that part in double quick time.

If the metal is bonded, it requires an anode suitable to protect it and other metal it is connected to. We have now deliberately setup a low resistance path for current to flow and have set up a system to make sure a sacrificial anode is available to sacrifice itself as a part of the system. It does have the advantage that if any voltage is accidentally applied to that metal, the current that flows will hopefully blow the fuse on that circuit ensuring the fault is found and that leakage current eliminated.

Jeanneau choose to not bond through hulls and rudder and in most cases it works fine. The prop shaft, P bracket and prop are tied together and protected by the shaft anode ( for shaft drive sail boats).

It is a choice but from the factory it is not bonded.

I hope this helps make a decision.

Trevor

[dash34]

On all of my boats I make it a priority to check all of the through hulls. When suspect they are changed out with plastic/composite. My felling has been that if bonded, should one have an issue it may go unnoticed and all of them now have a problem. R

[mobybill]

Thanks to the responses and apologies for not getting back to you earlier. I have been away in Tasmania.
I haver not attempted to bond the rudder stock but will inspect next haul out.

[Trevor]

Hi mobybill,

If you do decide to bond the rudder, you may need to rethink the amount of sacrifical anode surface area required to protect it. Currently for a shaft drive yacht, Jeanneau have a prop shaft anode which protects the prop, the shaft and the "P" bracket. If you decide to bond the rudder shaft, the added mass to the other bonded components may require a more sizable anode. This can be measured using a Silver Chloride half cell. If you do decide to do that it would be interesting to hear the result.

Trevor