Seaworthy Magazine: Thunderstorms - A Few Members' Accounts
In June, 1998, we were anchored at Duble Breasted Cays in the Abacos, Bahamas in my 38ft Morgan designed Heritage West Indies sloop with a 54 foot mast stepped on a steel keelson through bolted to an exposed lead keel. The best grounding system in the world! About 0830 as the four of us had coffee in the cockpit, a very fast moving tiny thunder squall headed our way. The lightning marched across the water towards us.
I went below to disconnect the GPS and VHF and was just reaching for the VHF antenna cable when lightning did a direct hit. Had I been touching it, I probably wouldn't be writing this piece. I saw a glowing fireball of water drip from a cracked hatch to the cabin sole five feet from me and go out with a splat when it landed.
The crew of a catamaran anchored about a quarter mile away dinghied over after the short storm thinking we must have been killed, but no one was injured. We just tingled for a few minutes. They buddy boated back with us the next day to West End because all of our electronics except for the autopilot, nearly all of our lighting circuits and, of course, the VHF antenna were blown out. Parts of it landed on deck, as did parts of the masthead tricolor and anchor light. Wires in the mast were melted. (Fortunately I had spare handheld VHF and GPS.) Even the Loran set was blown despite not having been connected to antenna or power at the time. Later we learned the battery charging circuit was blown out too as the house batteries went dead. Rusty parts of the steel mast step were blown off into the bilge.
After three days of futile waiting for a new battery combiner, I ran a light jumper wire from the positive terminal of the isolated engine start battery to the house batteries and got the charging back on line from the alternator even though I couldn't repair the shore power charger. I didn't realize you could do that without heavy jumper cables, but a boatyard owner told me you could and it worked fine. Then we were able to cross the Gulf Stream to home. The damage came to about $12,000, mostly insured.
Lightning struck the same boat at my dock this past spring when no one was aboard but it must have been a glancing blow because the damage only came to $2,900, $500 over my deductible. Again, the VHF antenna took the hit, but neither the radio nor the GPS were plugged in to power or antenna. The GPS suffered a corrupted circuit board and its antenna was blown. The VHF set itself was OK this time, as was the mast wiring and lighting circuits. But again the charging had to be jumped.
What I have learned is to have a solid grounding system that is not bonded to through hulls so you don't blow any of them out, and to have spare handheld vital electronics and jumper cables. I can't see any purpose in a lightning rod or whiskers; the VHF antenna does fine as a lightning rod. Lightning easily jumps from it to the aluminum mast, which must be heavily grounded at its base to an exposed metal keel or grounding plate. Keep your spare instruments well separated from other electrical equipment; even disconnected electronics nearby can be blown. It would be nice to have a spare VHF with an antenna that could be hoisted on a halyard. Don't touch metal, and don't be surprised if the same boat gets struck twice!
What I don't understand is why the Autohelm auto pilot survived both strikes. I wish other electronics manufacturers could build in similar protection. Certainly some protection should be built in to the shore power charger; it shouldn't have blown when we weren't connected to shore power.