Being hit by lightning is actually quite
possible, over say 40 years of cruising in areas fraught with thunderstorms. Your chances are at least 1 in 3 of being hit, in the above category. (This is based on extensive studies, not just my opinion). I have dozens of friends or acquaintances who have been hit, and a boat right next to me has been hit on three occasions. This is just the strikes that I know of!
done by the University of Florida
about 20 years ago, on a Federal grant, was the most complete I've read. Basically, ground the mast
well with like... double ought wire, as straight down as possible to a 2 sq' (min) copper ground plate, and attach in as many of your shrouds / stays as possible, with #6 wire. Ground the engine
and large metal as well. (Cuts down on side flashes).
They found that linear edge of ground was more important than just area, so a plate 1' X 2' was not nearly as effective a ground as the exact same "area" in the shape of a 1" wide narrow strip going down the length of the hull
. But this is VERY impractical for most boats... so, we just ground them any way we can. Just, NOT with a "Dyna plate". They are useless as a lightning ground, and have been known to explode from a strike!
Lightning rods & Bottle brushes
... The rod is an essential part of the system. The "brush concept" has been proven statistically to work
on cell towers, and this is why every cell tower in the world has one. Weather
or not this principal carries over to boats is unknown, however there is "0" evidence to indicate that they make your odds worse.
I didn't mind a couple hundred more $ to "possibly" improve my odds, even if only slightly... so, I have one. (we have over 50,000 hours of labor in our boat!)
Remember, anyone who talks in absolutes about lightning, is full of it. The idea is to "improve your odds", that's all we can do. The basic ground system mentioned should go a LONG way in preventing the mast from being driven through the hull
, there are extreme measures like a "Faraday cage" but who goes that far? We have wrapped up a portable GPS
in a roll of foil, It just might help with inductance. Then, there is unplugging antennaes... I used to do it, but it just became too much effort.
In a real hit, you may well loose ALL of your electronics
, even if properly grounded. The grounding system is mainly in hopes that the strike doesn't put a LARGE
hole in your boat.
As for people... Obviously stay away from metal. This may not be easy. I have been at the wheel
, 3' from our mast, on the ICW
... with NO place to pull over, and repeated strikes within 100' all around! (This is in white out rain, and 45 knots of wind). I put on rubber gloves and boots, crouched down, and stood on the balls of my feet! I had read of this being useful... This MAY have improved my chances .5%, I don't know. I was so scared I would have whistled Dixie if I thought it would help!
I agree 100% with PBLAIS, inductance will get you under a "close strike" situation. I have had the boat's mast 200' away take a direct hit, and MY battery charger
was FRIED! It smoked up the cabin
. (Altogether, I've been through 5 battery
chargers from spikes down the line during a storm, or inductance).
One thing I do take the trouble to do, is unplug from the dock
in a storm, (not just trip the breaker)! Otherwise, if it hits the transformer 1,000' away, it can ruin lots of your electronics.
Just like life in general, I do what I can, about what I can, and hope I'm lucky about surviving the rest.
With lightning, doing nothing makes no sense at all! At least a basic ground system is called for, as it is cheep and easy insurance
. Not that you will not be hit, but that you might survive. It vastly improves your odds.