There may not be much a boater can do to prevent lightning from striking their vessel, but there is an important step to take immediately after a jolt hits, according to the July 2005 issue of Seaworthy magazine, the quarterly BoatU.S. Marine Insurance and damage avoidance report. In "Lightning! Flash, BANG! Your Boat's Been Hit- Now What?", Associate Editor Chuck Fort reviewed five years of lightning strike claims data from the BoatU.S. Marine Insurance claims files. What he found might surprise or confirm your suspicions about lightning strikes.
The feature reports that in any one year the odds of your boat being struck by lightning is about 1.2 in 1,000, with 33% of all lightning claims coming from the sunshine state, Florida. The second most struck area in the country was the Chesapeake Bay region (29%), while on the opposite side, 13 states had no lightning-related claims, including states such as Idaho and Nebraska.
The rate of lightning strikes for sailboats was about four boats per 1,000, while motorboats averaged 0.5 per 1,000. A surprise finding was that multi-hulled sailboats were struck more than twice as often as monohulls.
Interestingly, the files also showed that many boats equipped with lightning dissipaters were also hit, questioning their effectiveness. Most electronics aboard a boat were found not damaged by a direct hit but rather from surging electrical current created in the wiring by the strike.
While the story explains that some vessels can have little or no damage after a strike, an immediate short-haul is a must. The reason is that when lightning exits your boat, it can go through the hull itself or via a through-hull fitting. This may cause a gradual leak that could go unnoticed.
Oftentimes boaters don't know their unattended vessel has been struck or suffered collateral damage as the result of a nearby strike. The article reviews a claim in which lightning damage was found only after an amber LED light lit up on a battery charger - a light the owner had never seen before - and his depth sounder quit. Sometimes a damaged or missing VHF antenna is the only clue that an unattended boat has been struck. Fort also mentions that most vessels are not electrically bonded according to American Boat & Yacht Council lightning protection standards. Boats built to these construction standards offer a more direct pathway for lightning to exit a vessel.
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