Lightning protection
Most sailors worry about lightning to some extent. Afterall, going around with a tall metal pole on a flat sea when storm clouds threaten doesn’t seem like the best idea to most of us. In reality, thunder storms need plenty of energy, driven by the sun, and are much less frequent in northern Europe than in the tropics.
However, high currents passing through resistive conductors generate heat. Small diameter conductors melt; wooden masts explode; and air gaps that are bridged by an arc start fires. On boats, radio antennas may be vaporised, and metal thru-hulls blown out of the hull, or the surrounding fiberglass melted, with areas of gelcoat blown off.
Wherever you sail, lightning needs to be taken seriously. Understanding how lightning works, will help you evaluate the risks and make an informed decision about the level of protection you want on your boat and what precautions to take.
Most lightning is what’s called negative lightning, between the lower levels of clouds and the earth. Intermittent pre-discharges occur, ionising the air. Whereas air is normally a poor electrical conductor, process continues until an attachment spark connects with a stepped leader, creating a lightning channel of ionised air molecules from the cloud to ground. The main discharge, typically a series of discharges, now takes place through the lightning channel.
