Moody 38 (2000s) Electrical Bonding System

[Jeffrey Cohen]

I have a 2001 Moody 38 center cockpit I want to buy. Prior to closing, I am going over all systems on the boat. I am curious about the electrical bonding system. Do any of you readers know how extensive the bonding system was when it came from the factory? I have discovered that there are not many bonding wire connections going to a bus or directly to the zincs on the outside of the hull. I want to make sure the bonding system is extensive enough for me to install a lightning protection system without acute cable bends in a boat that is bonded well enough to minimize side flashes if there is a lightning strike. Thanks for your replies.

 

[Peter Wright]

Hi,

Firstly, I don't believe the Moody cathodic protection system was ever designed to serve as a lightening conductor. If you wish to fit an effective lightening conductor, I would recommend installing a complete separate system ending in a copper electrode below the waterline. I would want a higher cross section for a lightning conductor than you normally find to carry the low currents in cathodic protection systems.

The black art of cathodic protection has moved on significantly since the 1970s. Back then, it was common to find every metal part in contact with the sea bonded back to a zinc anode. Nowadays, it's rare to find bronze sea cocks connected to an anode. It has also also proved futile to expect a connection from your engine to your prop shaft through the gearbox, even with connection straps fitted across any flexible coupling. A properly lubricated bearing has proved to have enough resistance to render the connection from gearbox casing to shaft useless for cathodic protection. Expensive folding propellers generally come with their own custom made zincs and wise folk fit one or two shaft anodes whether or not the prop has a special of its own. Your fuel tank and any metal part in your fuel filler are normally bonded together to prevent any static charge building up between the two components when filling up - this is sometimes done by adding them into the cathodic protection bonding system. I would not want a lightning protection system combined with anything connected to my fuel tank.

I haven't got figures but I would view a lightning strike on the mast far more likely to attract a strike than the side of the hull.

Peter.

 

[Jeffrey Cohen]

Hi,

Firstly, I don't believe the Moody cathodic protection system was ever designed to serve as a lightening conductor. If you wish to fit an effective lightening conductor, I would recommend installing a complete separate system ending in a copper electrode below the waterline. I would want a higher cross section for a lightning conductor than you normally find to carry the low currents in cathodic protection systems.

The black art of cathodic protection has moved on significantly since the 1970s. Back then, it was common to find every metal part in contact with the sea bonded back to a zinc anode. Nowadays, it's rare to find bronze sea cocks connected to an anode. It has also also proved futile to expect a connection from your engine to your prop shaft through the gearbox, even with connection straps fitted across any flexible coupling. A properly lubricated bearing has proved to have enough resistance to render the connection from gearbox casing to shaft useless for cathodic protection. Expensive folding propellers generally come with their own custom made zincs and wise folk fit one or two shaft anodes whether or not the prop has a special of its own. Your fuel tank and any metal part in your fuel filler are normally bonded together to prevent any static charge building up between the two components when filling up - this is sometimes done by adding them into the cathodic protection bonding system. I would not want a lightning protection system combined with anything connected to my fuel tank.

I haven't got figures but I would view a lightning strike on the mast far more likely to attract a strike than the side of the hull.

Peter.

Peter, I agree with you entirely in what you wrote. However I am still curious as to why there are so few bonding connections in the boat. I intend to separate the lightning protection system from the bonding system. At the same time, I want to make sure the bonding system is robust enough to diminish the side flash possibility. And yes, I do not intend to bond the skin fittings or as I call them through-hull fittings. Nevertheless, I would like to have all other metal objects aboard connected to the bonding system. Thanks for your excellent reply. Jeffrey

 

[Peter Wright]

There is purpose in bonding metal components which spend a significant amount of time in the sea, particularly if there are any electrical systems associated with them whether 12V, DC or 230V / 110 V. AC. For electgrical safety, the earth (ground) part of the AC system and the negative of the DC system should both be connected to the bonding arrangements. Because of the risk of issues ashore taking the earth system away from Earth potential, many yachts have a Galvanic isolator to disconnect the yachts AC earth from the shoreside AC earth.

Once you have ruled out skin fittings, there are very few metal components below the waterline requiring connection to the zinc, A water cooled refrgeration codenser would be one. Some folk slap a big zinc on their iron keel, but it never seems to help a case of rusting keel once it has started and the salt has got into the pores of the cast iron. I have never seen metal components above the waterline connected to zincs - who tries putting cathodic protection on their winches? What components are you expecting to find wired to the zinc?

Peter.