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I pass along the following comments from Telltales Magazine August 1999
page 22. The article entitled Lightening was written by Larry Crouch who
is currently the repair yard superintendent at Seabrook Shipyard.
The American Boat and Yacht Council (ABYC) suggest that a "zone of
protection" may be formed around a boat by providing a direct path to
ground form a lightening rod attached to the vessel's highest point.
ABYC defines a "zone of protection" as "an essentially cone-shaped space
below a grounded air terminal, mast or overhead ground wire, wherein the
risk of a direct lightening strike is substantially reduced."
Theoretically, the "zone of protection" provides security for an area in
diameter equal to the height of the lightening rod. This means that most
sailboats with aluminum masts )when properly grounded) should provide
some measure of safety for their passengers. Powerboats, however, need
to be fitted with a lightening rod above the flybridge seating area.
The ABYC states that a minimum system consists of a lightening rod and an
external grounding plate. The plate should be at least 1 square foot in
surface area for saltwater applications. The bonding wire between the
lightening rod and the grounding plate ,must have a minimum conductivity
of a #4 wire. The lightening rod ,must be located so that its end
terminates no less than 6 inches above the highest point of the mast. An
aluminum mast may act as a conductor, but wooden masts must have a
minimum of a #8 copper wire as a conduit from the rod to the bonding wire
connected to the ground plate. Sailboats with split rigs should have a
lightening rod on each mast.
Experts agree that the bonding wire from the mast to the grounding plate
must be as direct as possible, sharp bends or loops may cause the strike
to "jump" to a different conductor. These "side flashes" are the cause
of most major damage. The ABYC suggests that :no bend of a conductor
shall form an included angle of less than 90 degrees, no shall have a
radius of bend less that 8 inches.
This is only part of the article. I have no first had knowledge on the
subject but I thought what he said made sense. Hope it helps you in your
research.
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