Once known as Hartley18
Join Date: Aug 2007
Location: Melbourne, Australia
Thanked 85 Times in 85 Posts
Rep Power: 11
Why would your rigging be part of the electrical ground? I don't think it should be, mine isn't, and I don't think I have seen one that is.
Did hear once of an older boat where the mast was used as the negative ground for the mast lighting though - only positive wires needed that way.
Some boats have the chainplates connected to keel bolts which forms an indirect path to ground. I didn't say anything about the brightness of the test bulb - which is irrelevant here - only that some voltage will generally exist between the rigging and battery positive. Exactly how much will depend on the construction of the boat.
In my example, it doesn't have to be the rigging - perhaps the VHF antenna shield would have been a better choice.
A bad day on a boat beats a good day in the office