It's a topic I have been asked about a number of times, especially as lighting strikes on yachts here in the tropics are quite common, and often quite devastating to a yacht's electrical systems. Further the lightning strike can leave the yacht owner uncertain as to what extent structural damage may have been done to the mast, rigging and other structural components in the boat and is not obvious to a visual inspection.
Boats with carbon rigs appear to be more vulnerable to damage than boats with alloy masts and inexplicably catamarans seem to be struck far more frequently than monohulls, at least in this part of the world. In one particular case the owner of one of our designs who had suffered a strike found a series of holes in the laminate running from the deck to the waterline in exactly the postion where the chainplate laminates were embedded with the hull laminate. Had this caused a structural issue for the integrity of the rig? I had to confess I wasn't able to provide any informed advice on this issue.
There are methods recommended for minimising lightning damage, such as feeding conductive material into the water from the base of the mast (galvanised chain or copper braid for example), and there is a number of commercially available systems that you you can find with a quick web search. These usually combine technologies such as mast base electrode clusters, surge suppressors, immersed ground studs in the hulls aft, and loop conductors with bow and stern electrodes.
Are these systems effective? It's a difficult thing to quantify. If you have a protection system installed and you suffer a bit of damage after being hit; does that mean the damage would have been worse if you didn't have the protection, or does it mean the protection didn't work?
I was interested to learn that according to the FAA, on average commercial aircraft get hit by lightning once a year and surfacing films are routinely deployed to minimise damage to the aircraft. The aircraft is divided up into lightning strike zones and surfacing films that incorporate copper mesh and paper in a resin matrix are deployed to provide a certain level of protection. This information was gleaned from a press release by Henkel Adhesives
Surface films, apart from potentially minimizing lightning strike damage, also have application for surface appearance and processing. Should we be paying more attention to surfacing films in the build process or is it just another cost we would prefer to avoid?
For further reading on lightning strike protection for aircraft see this article in Composites World: www.compositesworld.com/articles/lightning-strike-protection-strategies-for-composite-aircraft
Further to the article above I came across this post while browsing the news pages of the MIT on an unrelated topic.
For me this article raises some intersting
questions. Could we minimise lightning damage in yachts by inducing an electric charge in the mast and/or the rigging? And is there something in this research that helps to explain why catamarans
(and possibly trimarans) are more likely to be struck than a monohull?