Forums, Electrical Systems, Navigation and Safety equipment, bonding sys / shaft brush

Tazling at 22/08/2013 01:49:31
My JJT CO32 came with 2 zincs attached one on either side of the keel, with bolts through into the sump walls, and “mystery wires” leading off into the snakes’ nest of hoses and wires heading aft. I have a feeling that they are attached, eventually, to a shaft brush that rides on the very small exposed section of drive shaft between stuffing box and gearbox.

Question: if I have (and I have!) attached a sturdy prop zinc externally, do I still need the shaft brush? I have a long-standing distrust of bonding systems :-) If my prop zinc is beefy and well attached, can I dispense with the keel zincs? They don’t seem to have been doing all that much for the prop anyway - the bronze shows telltale pinkish freckles and mottling.

inquiring minds…

BTW, my CO32 squeaked past an Alberg 35 on Monday in an informal local race. The air was light and fluky (going to weather, thank goodness for small mercies) and it was tetchy, gritted-teeth helming but eventually, slowly, despite getting a late start and having a quarter mile or so to catch up, I was ahead of my esteemed rival round the first mark. That was a good day :) The A35 had a taller rig, more waterline, deep local knowledge, and better sails… so I am not sure what got me into the lead - dumb luck in the lulls and puffs, or (I would like to think) better strategy, rigorously attentive steering, and a fine boat :) Hooray Contessa!

George Isted at 04/09/2013 12:21:17
Depending on how much metal there is in the water (marina mooring piles), some areas seem to need more anode protection than others. To me it seems a bit of a black art and relates to shore power being earthed to the anodes also.

Most of the racing boats do away with the hull anode but hang one over the side when moored up, I presume this is bonded to the underwater metal fittings.

I myself only have a prop anode that lasts around 18 months and no hull anode but the boat is not left connected to shore power. The blakes seacocks that have been removed for inspection all seem to be in excellent condition so not been eaten away yet.

Conte at 11/09/2013 20:49:35
Hi all,
Seacocks (mine are all in Marelon) and the engine apart, there is something else that needs to be connected to the anode?

Piero

samourai at 18/03/2019 18:58:11
Hi everyone,
I am at the moment fitting a new shaft and fixed 3 blade prop (14×8″) on our CO32 and I realised there is no space to fit a shaft anode. Obviously this is because of the rudder which is behind. So the question is how am I suppose to protect the stern gear from electrolysis ? Apparently there is no external anode but I really think I should better fit one. Does anybody could give an advise on how to connect the shaft+prop on an external anode ? Is there any other part of the boat which should also be connected to this anode ? CO32 “Samourai”

Keny at 21/03/2019 16:18:35
It depends on your coupling. If it’s an R&D one it will have a carbon brush which connects the shaft to the gearbox and ultimately the sacrificial anode which you should sensibly have.
If it is one of the rubber couplings you can bridge it with a flexible s/s wire or some sort of brush box which can be connected straight to the conductor.
The anode will also be connected to the engine/gearbox to protect aluminium castings etc.
The Blakes sea cocks don’t need to be connected since they are made of a single metal.
Ken

samourai at 21/03/2019 20:46:04
Hi Ken,
Thanks a lot for your explanation. It makes things a bit more clear on this subject. As George said in his post: “its a bit of a black art”… On my CO32, the shaft is directly connected from the coupler to the gear box, there is no “flexible coupling”. As I understand, I will have to fit a carbon brush device & an external anode to be on the safe side.
If anybody has a photo of this “carbon brush” arrangement in the engine room, that will be very welcome !

Keny at 22/03/2019 09:09:55
Sounds like a flexible coupling wouldn’t go amiss as well. The current trend seems to be the rubber sort.
However if your shaft is directly connected to the gearbox and you fit a sacrificial anode, that is all that’s required.