# Thunderstorm



## maldo105 (Dec 2, 2018)

Hello sailors. I still don't have a sailboat but working on it. I was wandering what happens to a sailboat if stroke by lighting? How the boat dissipate electricity from lighting if the mast got hit by one?


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## Arcb (Aug 13, 2016)

Think it can vary considerably. Was hit by lightning in 2013. I was ashore but my wife was on board at dock. She called me at work and said she thought we were hit by lightning but all was well. Woke up in the morning to find molten aluminum droplets on the deck. The mast head VHF antenna was gone and some melting/scorching to the mast head cap. We never did find any other damage. Boat was a 74 with a gas inboard. I understand damage can be minimal to serious.


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## Jeff_H (Feb 26, 2000)

It depends on how the boat is constructed. Synergy was struck by lightning when she was out of the water. Like ArcB, there were bits of metal scattered about. The windex, anchor light and VHF antennae was blown apart.

But on Synergy we think that the electricity came down the mast, through the aluminum mast step, through the stainless steel beam that supports the mast step, through the keel bolts that pass through the stainless steel beam, through the lead keel, and out the bottom where it blew a small crater in the asphalt paving. 

The damage was odd. Some breakers were fried. The bilge pump switch was blown to pieces across the cabin. All the electronics were fried, as were the batteries. Some wiring was fried, but most was okay. 

But surprisingly a detailed survey turned up nothing other than fried electrical items. I replaced my standing rigging as a precaution out of my pocket. 

On the other hand when I lived in Georgia I saw a boat that was sunk from a lightning strike. The lightning strike blew apart the king post under the mast, blew a single large hole in the bottom of the boat. Blew a slew of small holes in the bottom, blew apart some of the seacocks, the shrapnel from which punctured and was embedded in the bulkheads. Even the head was melted and shattered.

Part of the theory of why there was so much damage was that there was a discontinuous path from the mast to the water, and so the bonding network allowed the current to move all over the boat. In that regard, beyond the semi-direct route, Synergy is not bonded which may have also limited the damage. 

Jeff


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## paulk (Jun 2, 2000)

So far no one has mentioned wooden masts, which can be exciting. Moisture trapped inside wooden masts can be superheated by a lightning strike, instantly turning to steam. Steam expands to 1700 times the volume of the water it originates from - even more when superheated. Wooden masts hit by lightning can therefore explode if there is moisture that fastenings like sail track screws, spreader fittings or lifting varnish have have allowed to soak into the wood. This is in addition to anything that might happen from current running down the metal rigging.


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## midwesterner (Dec 14, 2015)

Nothing happens. It's better to not think about it. It's more likely to have a 747 engine fall on your house.

(These are the things I tell myself).

And do not click on the link below.


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## JimsCAL (May 23, 2007)

Many years ago, friends were sitting below at the dock with their new boat when it was hit. It blew out the speed sensor and the boat started taking on water. They named the boat Zapped.


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## VIEXILE (Jan 10, 2001)

Dynamite lighting strikes yesterday - wife showed me on Facebook. Rodney Querrard, the retired Chief of Police caught the strikes in Hull Bay area on video. See "What's Happening St. Thomas" on FB.


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## Greenwave (Jan 12, 2020)

paulk said:


> So far no one has mentioned wooden masts, which can be exciting. Moisture trapped inside wooden masts can be superheated by a lightning strike, instantly turning to steam. Steam expands to 1700 times the volume of the water it originates from - even more when superheated. Wooden masts hit by lightning can therefore explode if there is moisture that fastenings like sail track screws, spreader fittings or lifting varnish have have allowed to soak into the wood. This is in addition to anything that might happen from current running down the metal rigging.


Just like a tree... I have seen them blown to bits or slivered surgically.


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## paulk (Jun 2, 2000)

The likelihood of a 747 engine coming off (above), reminds me of the story some time ago from the Japanese Coast Guard, which rescued fishermen from the water who said their boat had been hit and sunk by a falling cow. They thought the fishermen were delirious from having drunk too much seawater. Until the Russian Air Force admitted to having jettisoned a cow that had gone berserk on a flight over the Pacific. "Bullseye!" is not quite the right term, but it comes close.


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## midwesterner (Dec 14, 2015)

paulk said:


> The likelihood of a 747 engine coming off (above), reminds me of the story some time ago from the Japanese Coast Guard, which rescued fishermen from the water who said their boat had been hit and sunk by a falling cow. They thought the fishermen were delirious from having drunk too much seawater. Until the Russian Air Force admitted to having jettisoned a cow that had gone berserk on a flight over the Pacific. "Bullseye!" is not quite the right term, but it comes close.


I've heard a couple of accounts of people who had large poop and peesicles that froze to the side of airlines, when they had leaks in their toilet holding tank, and dropped off as they began thawing, as the plane descends to lower altitudes. Someone in the flight landing path of the St. Louis airport had one about the size of two basketballs, break through the roof of their house.


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## Arcb (Aug 13, 2016)

midwesterner said:


> I've heard a couple of accounts of people who had large poop and peesicles that froze to the side of airlines, when they had leaks in their toilet holding tank, and dropped off as they began thawing, as the plane descends to lower altitudes. Someone in the flight landing path of the St. Louis airport had one about the size of two basketballs, break through the roof of their house.


Happened near here few years back. https://www.cbc.ca/news/canada/ottawa/blue-ice-passing-plane-hole-roof-nepean-1.3500832


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## capta (Jun 27, 2011)

I've been on a number of boats that have been hit. One time it hit the boat across the dock in the Keys and came up the neutral leg from the power pedestal and fried only the 110 gear that *wasn't *operating?
Another time I was operating a rich guy's yacht going north offshore around the Fla/Ga border and all the 12 volt electronics shut down after we were struck. As we were headed for Nova Scotia on a schedule we just continued on w/o GPS, radar or radios and strangely, every bit of the electronics came back to life on their own, over the next few days.
Between Fiji and NZ we were struck on my old gaffer (wooden spars) and I happened to be looking at the masthead and it appeared to go up, not down and we had no problems. I was however, blind for a couple of hours and my wife at the time had to take over my watch.
I've seen a hole blown in the bottom of a boat, which immediately sank at the dock, chain plates severed from the hull and the glass around there fried and shrouds completely fried.
So, I guess it's back to the black box theory. "Feeling lucky, punk?"


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## CaptFarmer (Sep 27, 2020)

maldo105 said:


> Hello sailors. I still don't have a sailboat but working on it. I was wandering what happens to a sailboat if stroke by lighting? How the boat dissipate electricity from lighting if the mast got hit by one?


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## CaptFarmer (Sep 27, 2020)

My wife and I were at our dock when a storm came up so we got back in the truck to wait it out. There was a blinding flash, immediate boom and the strong smell of Ozone! After the storm passed we walked the dock. We found a sailboat with charring on the hull and spalled off fiberglass and gelcoat both near the chain-plates. The owner admitted that he did not have a lightning bonding system, like we did, two slips away and it fried all of his electronics. I lost track of the boat after that but I think he sold it and got a bigger boat.


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## Barquito (Dec 5, 2007)

So, I would assume a lightning strike is fairly unlikely and highly variable in the damage it will cause. I would suggest the next question has been talked about a lot on this forum: 'What the heck do I do to keep from being hit?'


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## CaptFarmer (Sep 27, 2020)

Barquito said:


> So, I would assume a lightning strike is fairly unlikely and highly variable in the damage it will cause. I would suggest the next question has been talked about a lot on this forum: 'What the heck do I do to keep from being hit?'


See ABYC TE-4


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## CaptFarmer (Sep 27, 2020)

See ABYC TE-4 in Lightening Protection and if you can find it 
"This article was published in the October 2007 edition of Exchange.
*A New Concept for Lightning Protection of Boats
Protect a Boat like a Building*
Ewen M. Thomson, Ph.D."​


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## capta (Jun 27, 2011)

CaptFarmer said:


> See ABYC TE-4 in Lightening Protection and if you can find it
> "This article was published in the October 2007 edition of Exchange.
> *A New Concept for Lightning Protection of Boats
> Protect a Boat like a Building*
> Ewen M. Thomson, Ph.D."​


That might be the system they installed on a top flight sport fishing boat to test it. Sort of like a Faraday cage, it did indeed protect the boat from the lightning strikes, but it was hit several times in as many months and the owner had it removed. In his many years owning the boat, it had never been struck until this system was installed. I've heard nothing about it since I read that article.


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## Challenger007 (Nov 6, 2020)

Barquito said:


> So, I would assume a lightning strike is fairly unlikely and highly variable in the damage it will cause. I would suggest the next question has been talked about a lot on this forum: 'What the heck do I do to keep from being hit?'


I think you better not use metal, especially at the top of the masts. They can be a kind of lightning bait. Also, try not to swim in a violent storm. Because if lightning strikes the boat while you're on the shore, that's one thing. And when you're on a wet deck, it can be dangerous. Although it still depends on the design of the vessel. Everything is individual and requires a reasonable approach.


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