LIGHTNING STRIKE

Dick Lowery

(Dick and Erica Lowery sail Shikara, their Southern Cross 35, from Annapolis, Maryland.)

On our way to the June 1995 Chesapeake Bay regional OCC rendezvous we had a new and involuntary experience which we would not like to repeat.

The good news is -- we were struck by lighting and lived to tell about it. The bad news is -- just about everything else. If you are on speaking terms with your great Benefactor in the sky, pray that He not let it happen to you.

Even though most of this experience is on the down side, I am writing about it because we learned new details about what frequently happens. I hope other members will find this at least interesting and possibly helpful for the future.

While cruising aboard Shikara in early June, we were rafted with another boat in a protected anchorage in the Corrotoman River off the Rappahannock just above the Tides Inn. We were having dinner aboard their boat during a severe thunderstorm that was heavy on the electrical side. We were close to a line of trees, all of which were taller than our masts. Fortunately for Shikara, our friends' mast was about 6ft taller than ours.

Sometimes boat masts are struck by lightning and people on board do not know it until they try to operate destroyed electronics. There was no question in our case. We heard the familiar ear-splitting `CRACK' and out of every port and hatch saw a shower of sparks, accompanied by black smoke coming out of the back of the boat's power panel. No one on board was hurt. Our experience from reading and talking to others, is that lightning strikes are seldom threatening to sailboat occupants because of the lightning rod characteristics of the mast.

We first checked that no water was coming into the boat. Sometimes a boat's hull integrity is damaged when the lightning strike goes out through the bottom into the water. Sometimes a through-hull* can be damaged, and we have heard of cases where a hole has been blown directly through the hull. This did not happen to us -- but nearly so.

Immediate inspection revealed that the lightning had struck the masthead VHF whip antenna*, which no longer existed. It had apparently become the shower of sparks we had seen. More thorough inspection the next morning revealed that it had actually been turned into hundreds of little meteors which had melted their way through our friends' new canvas dodger* and bimini top. Furthermore, all electronic instrumentation was destroyed, and running lights, anchor light, steaming light, deck light etc were all burned out. Subsequent inspection revealed melted wiring inside the mast. Damage also included the hi-fi, VCR*, tape recorder console etc.

We next checked the engine. It started and appeared to work normally, but both the tachometer and alternator were burned out. Detailed inspection of Shikara revealed no damage whatsoever, although a metal part from our neighbour's VHF antenna base was laying on our deck. Our two onboard kittens were fine and seemed nonplused.

But this does not end the story. On subsequent discussion with their insurance company (fortunately our friends were insured against lightning strike), the company called for the boat to be hauled and for a survey. I understand this is not uncommon because of latent damage which can result in sinking. The survey revealed that although the boat systems were well grounded in various ways -- rigging to through-hulls, engine etc and to a groundplate -- the majority of the lightning's power had exited via the depth-sounder transducer, which it pulverized without causing it to leak, and through the engine via the shaft and propeller. In the process it ruined one blade of the two-bladed propeller, not by disintegrating it but by severely degrading the integrity of the metal. Sometimes, their insurance agent told them, such a power path can also ruin bearings inside an engine or transmission. My friends still have to determine whether they have any of the latter damage.

In a case we heard of on another boat, a small transistor radio lying in the middle of a sleeping berth was destroyed during a lightning strike along with all their other electronics. Obviously, all electronics are at great risk because of the sympathetic surges which are set up in the internal circuitry. They were offshore when struck and their main compass had a 30error, which did not result from damage but because the lightning surge turned the little compass compensation magnets from their initial settings. They did not discover this error until they came ashore at a fifty mile divergence from where they thought they were by dead reckoning.

Some members in the US may have read the recent excellent article in the BOAT/US Seaworthy publication about lightning inhibitors just coming onto the market for sailboats. In the US they are available from West Marine and a few other places. The jury still seems to be out regarding their effectiveness, but they certainly sound good in concept. They are grounded brass wire brush attachments you install on the top of the mast, which are supposed to pull ions out of the air in your vicinity, so reducing the likelihood of a lightning strike. Others think they may act as a lightning rod and may attract a lightning strike.

That same article says that cruisers have a 1:1000 chance of being struck by lightning. The insurance agent in this case said he has handled two or three lightning strike claims in three years for the boats he insures (I do not know how many that is). My experience, though, makes me think the odds are higher than 1:1000 for people who use their boats a lot, because so many of our friends have had lightning strikes. We also know some boats that have been struck more than once, one to the extent that the owner will only connect his VHF antenna when he wants to transmit. We have found him hard to raise on the radio, but then maybe he doesn't want to hear from us either. There could be other factors at work to figure into the odds.

So, what is the bottom line? I am seriously considering buying a lightning strike inhibitor for my mast. Some have compared the lightning inhibitor to a device which will scare away elephants -- but then, if I can keep both lightning strikes and elephants away from my mast, I think it will be worth it!

US/UK synonyms: through-hull = skin fitting; antenna = aerial; dodger = sprayhood; VCR = video