Lightning

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The first Tag 60 ever built is innovative in almost every way. Designed by New Zealander Greg Young and built by Tag Yachts of South Africa, (www.tagyachts.com) this catamaran is all carbon fiber, which makes it essential that she have the most advanced lightning protection system possible. Insurance statistics show that a cruising catamaran is twice as likely to be struck by lightning as a monohull sailboat and 45 times more likely than a motoryacht. Claims due to a strike are also higher, reflecting greater damage.

Ewen Thomson, one of America’s leading experts on lightning and boats, says it’s all about footprint. Multihulls are wider so they enjoy less shielding from nearby boats when they are at a marina. Because of their beam, they are also more likely to be tied to a face dock, in which case they have no shielding at all on the open-water side. 

Even though motoryachts are far less likely to be struck, new technology works against owners of these boats as well. A lightning strike may disable the ECU of a modern electronically controlled diesel engine. Old-style mechanical diesels will continue to chug along even if disconnected from the ship’s batteries. This makes them less likely to be affected by a direct hit, which would shut down a new boat.

Pod-drives from Volvo Penta and Cummins are a hot commodity, but the threat of damage from lightning is twofold. Not only is thrust controlled electronically, but steering is also. “You can undoubtedly appreciate the vulnerabilities that arise when electric control lines converge from all over the boat onto the best immersed ground on the vessel,” Thomson says, referring to the pod-drives.

Given the reputation of the manufacturers, these electronic controls are probably about as robust as they can possibly be, but consider what might confront them on any given summer day. Though it lasts only a fraction of a second, a lightning strike can develop millions of volts, peak currents of tens of thousands of amps and temperatures of up to 50,000 degrees F.

The marine industry’s long-standing lightning protection language urges boatbuilders to put a one-square-foot grounding plate along the keel, connected to the mast, arch or other part high in the structure with heavy-gauge wire and to the ship’s bonded underwater metal fittings. Thomson says his research contradicts that wisdom.

During his tenure as a researcher and associate professor at the University of Florida in Gainesville, Thomson authored several influential papers on lightning physics, including lightning in a marine environment. He collaborated with other experts in writing standards for the American Boat and Yacht Council and National Fire Protection Association. In 2001, he left academia to found Marine Lightning Protection Inc. His company developed a system — and patented some of its unique equipment — that Thomson and a growing number of marine industry people believe can save lives and make marine electronics less likely to be ruined by a strike.