Bonding system (task)

Task Specification

New Primary Bonding Conductor Needed

The primary bonding conductor is a copper wire that runs from the stern to the bow along the bottom of the boat. This wire is badly corroded in some parts and should be replaced anyway by a much bigger wire. Ideally, it should be able to carry as much current as the starter motor cables.

Lightning Protection

All stanchions, shrouds, stays, pulpits, and the mast should be directly connected to the primary bonding conductor, preferably by very big wires. There should be a metal ground plate on the exterior of bottom of the boat that is also connected to the primary bonding conductor. Ideally, the electrical path between the mast and the ground plate should be short, through very heavy gauge wire, and should have no turns.

Galvanic Protection

In addition, to prevent galvanic corrosion the following items should be connected to the primary bonding conductor:

• Engine
• Fuel tanks
• Rudder (because of its connection to the autonav system)
• Bilge pump metal housing
• Metal chassis of other equipment

All bonding conductors should be either bare wire, or colored green.

The following things should all be connected together at one point only, referred to as the engine negative terminal:

• the primary bonding conductor
• the engine block
• the negative terminals of all batteries

Shore Power Grounding

Please note that the grounding conductor of the 110v shore power system MUST NOT be connected to the bonding system unless a galvanic isolator or isolation transformer is in place.

Status June 7, 2008

A 50-foot-long #4 AWG solid copper wire has been run the length of the ship. It has been primed and painted green to help prevent against corrosion. This new primary bonding conductor has been bolted to the ship's stem fitting which connects to the forestay.

It has been decided that the prop strut will make an effective ground plate for galvanic protection.

Primary galvanic protection is via the propeller shaft and the propeller. There are two sacrificial zinc balls bolted to the propeller shaft.

A heavy gauge wire will connect directly between the mast and the nearest keel terminal bolt. This wire is, in turn, connected to the copper wire that runs the length of the boat. The keel itself will act as a ground for lightning protection.

We might want separate DC and RF grounds. No plan yet as to how to accomplish this. Perhaps a large piece of copper foil glued to the hull beneath the aft cockpit seat (aft of the nav berth)? That would provide capacitive coupling with the seawater without corrosion or cross-coupling the DC ground.

the following test is from: http://www.sgcworld.com/sailboatgroundtechnote.html

A useful test of the quality of your ground is to lay out several long wires on deck connected to the RF ground connection on your Smartuner. You might also throw a wire over the side to connect to seawater as well. When you remove these temporary wires, reconnect to your boat’s grounding system. The signal should get better. If it gets worse, your RF grounding system needs work.

see also this article: http://edis.ifas.ufl.edu/SG071

To Do

• Mount the new primary bonding conductor to the underside of the floorboards (keep it out of the bilge) (DONE mwall ted)
• Trim the the primary bonding conductor to the correct length and attach it to the backstay. (DONE mwall)
• Connect the engine negative terminal to the primary bonding conductor (DONE mwall)
• Connect the prop strut bolts to the primary bonding conductor (NOT DONE: Matt believes this is not a good solution)
• Connect the Mast to the nearest keel terminal bolt
• Connect both keel terminal bolts to the primary bonding conductor (DONE mwall)
• Connect the shroud chainplates to the to the primary bonding conductor (DONE? mwall)
• Connect the electric bilge pump chassis to the primary bonding conductor
• Connect the rudder/autonav system to the primary bonding conductor
• Connect the fuel tank to the primary bonding conductor (DONE (it is connected to the engine negative terminal)
• Connect the water heater to the primary bonding conductor
• Diagnose shore power connection to make sure ground is isolated