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LIGHTNING PART II connection to the engine is standards suggest that the not putting it in harm’s way conductor be sized at least 4 as a main conductor of lightAWG. Wood and carbon fiber ing’s deadly current. This masts need such a conductor type of connection simply from the air terminal to serves to equalize imbalanced ground plate/strip. Any potentials, helping to keep other conductive, potential the engine from being on the paths for lightning, such as receiving end of a side flash, metal rigging, should also be which is an unwanted blast of tied into the system with a lightning’s deadly current. minimum of 6 AWG cable. The vertical grounding system Vessels with metal hulls don’t contends with the actual force require a grounding plate as of lightning’s current while the hull itself can be incorpohorizontal bonds to nearby rated into the protection sysmetal objects, including metal tem. Other hull materials like through-hulls, equalize the wood or fiberglass need an potential to help prevent lightunderwater metal surface to ning from jumping into these help safely conduct lightobjects and severely damaging ning’s high current discharge. them. A side flash into an This metal is typically a copunbonded metal through-hull per or bronze plate, or by can heat the surrounding ABYC standards, a lengthy Once shiny and like new, these marine components were all fiberglass enough to blow a strip with sharp edges to help blown apart by lightning. hole in the boat. dissipate the high potentials Because of the overwhelming electrical field involved, involved. The ground plate/strip should have a surface area efforts to protect sensitive electronics are less certain. Not of no less than one square foot for saltwater vessels. ISO easy to find for DC equipment, transient voltage surge supstandards recommend a minimum of two and a half square pressors can protect a device by diverting a sudden increase feet. Freshwater boats need no less than about 10 square feet in voltage to ground. Conversely, surge suppressors for AC since fresh water is less conductive. equipment can be easily found at your local hardware dealThe sintered bronze plates made for grounding radios er. Mariners also can successfully protect sensitive electronare not ideal for use as a lightning conductor. The plate’s ic devices by storing them in metal boxes or wrapping them actual effective surface area where such high current is in aluminum foil where practical. involved is questionable, and the idea that they can explode (from trapped water rapidly converting to steam) is freNew and revised protection system methods. A wellquently raised. When a direct strike hit my Bayfield 31, respected researcher, instructor and lightning expert, Ewen Angel, most of the current was safely routed through her Thomson, Ph.D., has contributed much to the safety of crew sintered bronze plate, without it exploding. However, the and vessels. He refines the grounding system approach, and plate lacked the surface area to discourage the lightning instead of a single set-up and ground plate, Thomson’s sysfrom seeking an alternate path, and the strike also used the tem involves multiple air terminals connected to multiple depth sounder transducer as a ground (and ruined the conductors. Each of these leads to a number of grounding instrument). terminals along the hull’s exterior waterline. To learn more The grounding plate or strip must be connected to the of these new concepts, visit www.marinelightning.com. conductor with type 2 strand 4 AWG copper cable or flatLearning about Thomson’s invaluable work will help in the tened copper tube. Ideally, the cable connecting a ground customization of your own lightning protection system. plate to the main conductor should be straight. If space doesn’t allow, a curve with a minimum radius of 8 inches is What to look for after a strike. If a vessel is struck, there are suggested. Note that sharp turns or corners may encourage important things one must look for. Most immediately, any side flashes. All connections must be sturdy, mechanically through-hull fittings and the underwater hull’s integrity fastened and corrosion protected. To help minimize potenshould be checked. Damage from heat, especially around tially lethal side flashes, ABYC standard prefers that sizable electrical connections, is possible, along with physical dammetal objects within 6 feet of any lightning conductor be ages. I’ve seen components literally thrown across a cabin, connected to the lightning ground system with a minimum plastic cases shattered and wire terminal ends yanked from of 6 AWG cable. Bonding metal objects into the system this their connections after lightning’s passage. Compass deviaway helps balance the dangerous disparity in the surroundtion should be checked. If the engine, alternator and battery ing electrical potential. Unconnected metal objects, in the bank appear unharmed, it’s wise to check the alternator’s intense electrical field of lightning’s proximity, develop regulator as its sensitive diodes most likely may be blown extreme voltages that encourage side flashes and can elec(allowing unregulated voltage into the battery bank— a trically “shock” crewmembers. It is also suggested that ruinous situation). Solar panel charge controllers and a solar engine blocks be connected to the grounding plate (but not panel’s diodes are also likely victims. Magnetic media, such to the main lightning conductor) to reduce the likely chance as a laptop’s hard drive, may be affected. of a side flash through the engine. This horizontal bonding 40

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