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holy7cow 03-13-2003 04:39 PM

Lightning Anyone?
Anyone here ever been in a boat while it was struck by lightning? I plan to live a board next year and always wondered if this is something for me to worry about. All information is valuable.

pirateofcapeann 03-13-2003 06:44 PM

Lightning Anyone?
Holy Cow!

I lived aboard for what, something like 15 years and sailed through some nasty squalls. Getting struck by lightning was on the list of things I needed to worry about, but it was way the kryst down on that list! You''ll see what I mean.

GordMay 03-14-2003 12:35 AM

Lightning Anyone?
See "Lightning & Sailboats" by Ewen M. Thompson.
Sea Grant Project #R/MI-10
Lots of other good web sources are searchable.
Good Luck

GordMay 03-14-2003 01:12 AM

Lightning Anyone?
Correction: There is NO "p" in Thomson.
Dr. Thomson''s site @

fourknots 03-14-2003 02:51 AM

Lightning Anyone?
I can tell you from experience that bonding will not stop a strike and there is no proof that it mitigates the damage.

When a few million volts hits you, there''s not much you can do. Sometimes the damage is minor, sometimes it blows a thru-hull out.

Worrying about it is like worrying about a meteor striking you - there''s not much point.

holy7cow 03-14-2003 10:49 AM

Lightning Anyone?
I''d lived in CLearwater, FL for 20 years and seemed like lightning struck everything down there. Power transformers, homes, even Stop signs.. but I''d never heard anyone speak of it hitting a mast or whatever. I do know that some lightning bolts have enough energy to run the city of Chicago for 24 hours so it seems like if you do get hit, you''re out of luck. Anyone else?

tsenator 03-14-2003 01:12 PM

Lightning Anyone?
Fourknots, when he says bonding I think he means bonding the mast (and shrouds) to the keel if you have an external lead/iron keel and not necesarily the thru-hulls.

Seperately, the reason you might want to bond the thru-hulls is to prevent their deterioation due to electrolysis or galvanic corrosion, but like you said that has nothing to do with lightning strikes.

BUT, if you were on a boat and your boat got hit with lightning, you (or your loved ones) have a MUCH better chance of not getting hit by the lightning or side-flashes if your mast/shrouds are bonded/grounded.

If you are on a boat, especially a deck stepped one, and the lightning comes down the mast or shrouds and then has nowhere to go (since you didn''t bont it to the keel) then you are just as good a conduit of that electricity as the air is (maybe better!).

To me, that is the best reason to ground/bond the Mast/Shrouds to the keel. (I wouldn''t bond to the thru hulls).

I think the website/article he refernces alludes to that also. Its more for safety IF you do get hit.

maxcontax 03-17-2003 09:56 AM

Lightning Anyone?
Protection against lightning is basically to stay neutrally charged. If your mast is aluminum and highly conductive, not a problem as long as it does not emit a "leader" or positive electrostatic charge up into a negatively charged storm cloud. There are two things you do about this: firstly ground out your mast to something substantial and conductive in the water. If the keel is encased in an insulating (electrically speaking) material, grounding to it may not be the best. Note that a lightning strike with poor ground will overcharge all metal in contact and disperse everywhere: this is how the chainplate bolts get popped out of sidestays. The point of contact gets very hot very fast, something sacrificial above the masthead is advised, but not copper or aluminum, they melt easily: try painted ferrous iron. The second part of this is to arrange the boat to have as little static charge as possible: main offender here is going to be wind ripping past sailcloth just before the rains come, creating an ionic charge that is often stored in the mast and boom. Take down all sails when a lightning storm is apparent and check your electrial grounds. The boat should then be close to neutral as the surrounds--or at least as good as it gets. Unplug things electric and sit away from metallic objects. A strike will be proportionate to the attraction of the mast and the negativity of the stormcloud. The strike needs a route from the masthead to saltwater in the shortest path with the least resistance.

navtron 03-19-2003 03:07 AM

Lightning Anyone?
A point of information...Been sailing offshore many years....been in many lightning storms....some where the night becomes day as the lightning lights up everything like daytime seeing the ocean around you for miles...more severe is when the lightning gets closer (the front)& more intense....instead of just lighting up everything it intensifies so you get a white out...meaning the lightning at first lights up everything...seeing colors of your deck, winches, etc...and then grows in intensity til all color & images are washed out & everything is just super bright white no depth to anything...which at this point you involuntary close and cover your eyes. All of this happens in a matter of 1-3 seconds, which feels like a long time....On one trip from Bermuda to N. Carolina, we encounted a major lightning storm, lightning shooting down everywhere 2, 3, 4, 8 strikes to the water at once over a wide area could see the front (cloud line)on the horizon(north to south,as far as you could see) & coming toward''s amazing how fast it moves. I had a deck stepped mast and decided to disconnect the batteries at the terminals & disconnect all wiring going up the mast..I was thinking if I don''t make any electrical fields, I would not attract the lightning..I had no mast grounding the front got closer the nite turned into day as the lightning strikes lit up the ocean & sky. Again as we merged the white outs began. You could feel the pressure changes on your body as the strikes got closer..the thunder was deafening to a point where it seemed to hurt...the helmsman had rubber gloves on..but not touching the helm..only when needed.(no autopilot w/batteries disconnected)me at the winches port side with storm jib up...We had on our foul weather gear with only our faces times the wind & pressure came straight down on us..other times being sucked up violently around strike, to this day we don''t know how close...hit fast & hard..causing an immediate white out & the rain on our faces to get so warm we had to wipe the water off our face....As we went thru the front things eased off quickly where we could start breathing again...BUT NO STRIKE!!!....I feel because the mast was not ground the lightning would have to find the mast like in a fog....where a grounded one would have attracted possibly many strikes....Being 200 miles from any landfall I was just glad we didn''t get hit...

ford_s 03-20-2003 03:19 PM

Lightning Anyone?
Yes, Wiped out all the electronics but no structual damage. Not fun, I didn''t enjoy it.

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