The best advice on this thread seems to be coming from Maine Sail, based on my experience and technical background. I've had 2 strikes on my boat: an indirect strike while on the hard and a direct strike 10 years later while in the water. No one was aboard, but both were witnessed.
I lost all of my electronics in each case. The indirect strike took out a wheel pilot control module that was on a shelf and not electrically connected to anything. The direct strike took out my battery bank (3 month old AGMs) in addition to just about anything with semiconductors. After the first strike I conferred with a couple of lighting experts, including Dr. Ewen Thomson, in an attempt to better understand what happened and what to do in the future.
My boat has the mast and chainplates grounded through the hull to a dynaplate in close proximity to the mast step. My boat also has a counterpoise system (for the SSB radio that was taken out in the first strike) that connects to 2 sizable sintered bronze grounding plates. I believe my grounding system protected my hull from being damaged.
That said, my lightning protection plan has 2 parts:
1. place any removable electronics (handheld GPS and VHF, rangefinder, camera, phone, etc.) in a faraday cage. Aluminum foil is better than nothing and is readily available on board. Better yet, place it all in the oven.
2. maintain a proper yacht policy that provides for full replacement of electronics--less the basic policy deductible, of course. Last time I checked, the BoatUS policy premium was $200 less than my yacht policy, but did not offer this kind of coverage.
I could go further, perhaps by fully subscribing to Dr. Thomson's approach (check out Articles
), but I'm willing to live with my current configuration and trust that the probability of a future strike is rather small.