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A properly designed lightning grounding system will have a lightning rod at the top of the mast, a heavy conductor connecting the base of the mast to a heavy copper plate on the outside of the hull, using as straight a path as possible, to help reduce the chance of side flashes. If the mast is not aluminum, then a heavy copper wire should be used to connect the lightning rod to the copper plate in the hull. Wooden masts and carbon fiber masts do not conduct electricity well enough to be used. Carbon fiber masts also have the problem of internal delamination in the case of a lightning strike, caused by the heat generated as the electrical charge passes through the laminate's graphite components.
A 2" wide copper or bronze strip 2-4' long embedded in the hull of the boat is an excellent lightning grounding strip. If it has threaded studs that pass through the hull, it would work quite well, and have points to attach the grounding cables to. A minimum of four linear feet of exposed plate edge is generally thought to be the safe minimum for a lightning ground plate. IIRC, a brozne Dynaplate, often used as a radio ground which is sintered bronze, is not a safe lightning grounding plate, as the water that is trapped within the plate can vaporize during a lightning strike and cause the plate to "explode".
Ideally, the shrouds, stays, chainplates and stanchions should also be attached to the ground plate. This will effectively form a "Faraday Cage" that will help protect the boat's occupants. The "cone of protection" from such a system usually covers a 45˚ cone with the lightning rod's tip at its apex.
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You know what the first rule of sailing is? ...Love. You can learn all the math in the 'verse, but you take
a boat to the sea you don't love, she'll shake you off just as sure as the turning of the worlds. Love keeps
her going when she oughta fall down, tells you she's hurting 'fore she keens. Makes her a home.
—Cpt. Mal Reynolds, Serenity (edited)
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Last edited by sailingdog; 08-20-2007 at 12:13 PM.