During the decades I was in a boatbuilding project
(3 separate ones), I read hundreds of books
, thousands of monthlys, and even paid for research
papers on a wide variety of subjects boat related... including this one. The jury was in 25+ years ago on this, and therefore, it seldom gets discussed except by the "gravity doesn't really exist" group.
Lightning is the #1 killer of all natural disasters on the planet. It is the fact that it is SO common, and kills one at the time, that has it off of the national news. This is as true on boats.
Thousands of boats get hit yearly, often with catastrophic results. I have known over 25 people who had their boats hit, (many within sight), but only a few were hit when they were on the boat. I have, however read of hundreds more! The important thing is that like wearing seatbelts, there is a way to improve your odds of survival X100...
Its not controversial, its common sense!
As far as lightning protection... Well it is a fickle thing, but we CAN drastically improve our odds against a total melt down, or driving the mast
through the bottom of the boat!
Seatbelts don't prevent car wrecks, nor does a "Lightning Protection" System protect you from lightning. Never claimed to. Both, however, improves our odds of survival X100 or more!
If you are hit, lightning WILL then go to ground, either through the hull
, catastrophically through the metal drivetrain and through hulls, or "hopefully", along the path that WE provide. This is the only given. IF YOU ARE HIT, IT WILL THEN GO TO GROUND!!! Only an idiot thinks that after hitting the mast head
, the bolt would get to the mast base, and just stop there...
Statistical evidence from a very small sample, (like ourselves and the folks we know personally), is meaningless! To be valid... It has to be the scientifically accumulated evidence, compiled by thousands of the world's marine
meteorologist, using tens of thousands of reports as a sample, over 20+ years... The jury has been in on this for decades!
Here's how to improve your odds exponentially:
can be done "just a bit", by unplugging things, or taken to extremes, put spare hand held GPS
type devices in a "Faraday cage", but this gets really iffy and of diminishing returns. I do carry a spare hand held GPS
or two, away from metal, but if you take a BIG one, it is quite possible that ALL electronics
will be fried. Lightning varies 1000%, and there are NO guarantees, EXCEPT that: "IF it hits your mast, it WILL then go to ground".
Setting as a goal, a lesser more reasonable level of protection... #1 You need a pointed lightning rod on the mast.
Then, GROUND THE MAST IN A DIRECT ROUTE
WITH COPPER. Copper is MANY times better at conducting electricity, where as SS is quite poor. AVOID SHARP BENDS!
Searunners, like mine, are quite good in this respect. Look at my huge "00" grounding wire coming out of the mast. Being copper, its conductivity is roughly equivalent to the entire aluminum
mast! Its through bolted, and just like other important connections, including batteries, I CRIMP, then "SOLDER" the crimp, for a perfect connection, and then I HEAT SHRINK the lug to wire interface. Even if the solder is melted by a direct hit, it remains crimped, and until then, the solder keeps the finely stranded tinned copper wire's end, 100% sealed!
This cable is bolted to the mast, with minimal bends, and I use "Jet Lube" copper loaded conductive grease in the interface. (NOT to be confused with "dielectric" grease, which is NON conductive). After cleaning
up the squeezed out grease with mineral spirits, dry and apply 5 coats of "Liquid Lectric Tape" vinyl dip. It is now totally conductive and will stay that way (100%) for 40 years!
This huge wire goes straight through the sub floor, (through a through hull
packed with silicone caulk, or a wire gland). From inside, under the cockpit
, it goes through the next floor down too.
Now you are to the inside of the hull bottom. I have my 2 sq ft (min) copper plate on the side of the mini keel
, and it has a curved copper piece that connects through the hull bottom with a 5/8" silicon bronze carriage bolt. On the inside "wire to bolt connection", do as on the mast connection. Same on the outside bolt pass through, except seal the hull's hole, and bed
the plate, in 5200.
With grounding plates of the same sq inches, the longer narrower one is best, as linear inches of exposed EDGE is more important than size alone. It dissipates the charge better. This shape I used was a good compromise over a 1" X 288" strap down the hull! Sometimes practicality wins out over theory.
This alone is the most important part, and if you go no further, do this!!! It allows the hit to pas through the hull to "ground" along YOUR route
, rather than the lightning's! Dangling a chain in the water
, and such as that, is just wishful thinking!
AVOID Dyna Plates. They are not meant for dissipating lightning, and it's just possible that they'd explode. Even as a radio ground... unless you remove it at EACH haul out
, and soak it in acid, the pores fill with growth. SO, it is no more surface area than it appears.
For the next level:
After this level of protection, I ran a #6 wire from ALL of the interior
chainplate bolts, (except the synthetic runners'), to the copper junction plate over the main pass through bolt. This helps prevent side flashes within the boat. ABYC recommends connecting in the engine
& stove too, for the same reason, but I didn't. Due to previous galvanic "issues", I isolated the grounding plate from the boat's AC AND DC systems. This solved
the problems. This "isolation", btw, requires that you rubber mount your VHF antenna
, as the bracket is DC -. This is very easy to do.
radio ground is connected with diodes that pass RF energy, but not DC current
, but that's a different subject.
MY mast head
lightning rod has the "thousand spikes" in a spiral around it, to "THEORETICALLY" bleed off ions and actually lessen the odds of a strike. Hmmm? It is solid science, used on cell phone
towers all over the world, but on boats, Who knows? Since it doesn't "take the place" of the lightning rod, it IS one, and there has NEVER been evidence of it making things worse, I gave it a try. May be coincidence, but a boat RIGHT next to me has been hit, rather than me, on THREE occasions. The water
or ground within 150' of us, has been hit on 5 or 6 more! Being hundreds of miles out at sea, was not as scary to us as the Chesapeake or ICW
, in summer, due to the powerful thunder storms!
I can't really endorse the "fuzzy thing" that I used, may just be BS, but at least ground your mast! Remember, just like gravity: "its the law"!
"IF it hits your mast, it WILL then go to ground"...