01-26-2008
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Join Date: Jan 2008
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OK, I bailed out at Page 3 and jumped to the last page, so I apologize if I'm restating someone else's point, but here's the bottom line. If you play golf, you know that every golf course has resident trees - made of wood - willing to testify that lightening is not respectful of dielectric properties of its victims. Yes, lightening is compelled to follow the laws of physics and must follow a conductive path, but here's a flash (no pun intended) - Lightening is usually accompanied by rain! Rain is conductive and makes the surface of anything it coats conductive! Aluminum, stainless, wood, fiberglass, are all potential paths for conducting current from a million volts when coated with rain. "Coaxing" the current to follow more conductive paths that present less risk of damage from the arcing (metal becomes molten at arc points - hence, arc welding - so robust connections are much more effective than clamps), and less risk from the high temperatures generated for an instant during the discharge, do help mitigate the risk of fire and blowing a hole in a stricken hull as lightening seeks its own path.
Now, what wipes out the electronics? Rarely, is it the current flow from the strike. It's generally the electromagnetic field generated by the current flow of the lightening as it seeks its path to the water and then to ground. Whether that path is actually metal or the watery skin of a wooden spar, it will generate a powerful electro-magnetic field. The field will realign those miniscule magnetic storage places known as software or firmware and will induce side currents in any wiring path that completes a circuit. It is these properties that are injurious to the electronics.
So, what's the prescription? To make it risk free, stay off the water (and the golf course). OK, you've already declined that option, so you've decided to accept some risk. Good for you – you’re a sailor! A robust grounding path from the mast to the water will greatly help (but not guarantee to) avoid burn damage from the strike and keep you floating. Not having this will decrease the risk of being struck but increase the risk of catastrophic damage if hit. I like staying afloat and not burning, so I generally go with grounding when lightening is likely to think I’m the most attractive thing around. In anchorages, I play the probability side and go for less attractive. Disconnecting all cables from electronics definitely does help to protect them and is highly recommended. Keep this in mind when installing new electronics, so that it’s not an ordeal. Putting anything storing data or programs - chips, discs, hard drives, etc. - in a metal box tucked away from where you anticipate lightening paths is also a good practice, but understand even this may not save them.
Or you can follow a friend's prescription. He anchors near large cats with their taller masts and larger acreage touching the water. Two months ago, anchored in the San Blas Islands, it paid off when the cat anchored 50 yards behind was hit. But the electromagnetic field still wiped out his laptop and induced a fatal current in his stereo system!
Good luck!
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If any of the methods mentioned/marketed had any empirical data to support their effectiveness in a true scientific method, they would have cornered the market on said devices and insurance companies would give us a break for installing them. The safety recommendations given by knowledgable sailors are still valid if caught in those situations, but some of these antics are as effective as trailing a dead cat over the side.
