Weird Effects of Lightning Strike

[scherzoja]

While reading the recent thread about Lightning Prevention Systems (
https://www.cruisersforum.com/forums...em-263247.html), I recalled a strike a few years ago that had one very strange effect.

Short version:
Struck by lightning at the dock and lightning strike opened the galley sink drain seacock ball valve about a quarter of a turn?


Long version:
My sailboat in brackish water with 50' mast tied to a dock with an aluminum corrugated roof with height of about 35'. Aluminum boathouse roof was about 8' away from the spreaders, which are about 25' above water. This was at a private dock, no marina dock pedestal. Dock's ground wire was part of the hot/neutral cable going to the house, about 300' away. The breaker on the house that feeds the dock was also tripped.

Shore power cord was connected to boat. The aluminum mast was not electrically connected to DC or AC systems and AC was not connected to DC.

Not sure if lightning hit the dock or boat, but either way, it traveled through the shore power cord.

I was in middle of refit and most of the interior was gutted. Only DC system was the Solar panel --> Controller --> Batteries. Only AC system was loosely hung romex feeding two AC outlets and three AC lights. I was not on the boat, but was in the house and the strike was very close because the noise was deafening and there was no noticeable time delay between lightning and thunder.


Shore power connected the 30 amp outlet on dock with the boat's 30amp input plug in cockpit. Romex traveled about 10' from boat inlet to a temp 4-gang box that has two duplex receptacles. A run of romex went forward to feed an AC light and AC duplex receptacle in the vberth. Another romex ran aft and round to port side to feed an AC light.

I had a depth sounder's through-the-hull transducer forward on centerline.
Aluminum mast sat in an aluminum step that was lagged into the encapsulated lead keel (fiberglass boat).

Standing rigging was stainless steel, no bonding wires connecting chain plates.

That's the rough, simple electrical system.

• Solar controller was not affected.
• There was no AC battery charger.
• Shore power cord at boat end was charred.
• GFCI breaker in Dock's service panel was fried. Dock has a subpanel with this GFCI breaker, which feeds a 30 amp outlet near the boat. That 30 amp outlet on dock was not damaged, but the inlet on the boat was charged. If I recall, only one of the three pins was burned (don't remember if it was hot, neutral, or ground).
• I had an i-Socket Workshop Automated Vacuum Switch that also got fried. I was plugged into one of the AC outlets.
• The cable running from the transducer had several spots where the energy blew off the sheathing and severed some or all of the conductors at each of the points. This cable ran aft to galley area, where it was coiled, but not connected to the display (remember, this was during a refit and not much was in the boat).

Here is the really weird effect. . .
The galley had been gutted and the sink drain seacock (Groco flange adapter with 1.5" Groco bronze ball valve) had partially opened up. A partially full metal can of paint thinner had landed sideways under the handle of that ball valve. I don't know where the can was, but it was probably some where near by and it just slid down the curvature of the hull and landed under the handle.

Yes, there was a noticeable amount of smoke down below.

How in the world did the lightning strike open the ball valve about a quarter of a turn?

No rubber drain hose, no sink, I had removed all of it. Just the seacock, which is about 10" from the V drive.

[Pandor]

A partially full metal can of paint thinner had landed sideways under the handle of that ball valve. I don't know where the can was, but it was probably some where near by and it just slid down the curvature of the hull and landed under the handle.

Don’t you believe the can was the more likely culprit over electricity?

[team karst]

and odd one for sure. Note that the thinner can was steel, correct? There is a very large magnetic field associated with strikes. That mag field pulled the can under the handle and partially activated it?

[scherzoja]

Yes, the can was steel and the ball valve is slightly magnetic. Although stainless, it must be low quality 316 or 304. I guess that if there is a large enough magnetic field, a slightly magnetic object can become much more magnetic and maybe the handle and can had opposite poles, which caused an opposing force to open the valve. Perhaps the v drive became highly magnetic and that caused the handle to open. The thinner can might have just fallen into place had had nothing to do with hit.

What was also interesting is that there was current in the transducer wire, which was only connected at the transducer.

I forgot one important detail. The VHF antenna at the masthead was vaporized, so I guess my mast got hit, then the force traveled everywhere, interestingly, although with no physical connection between the mast and the AC wiring or the transducer wiring, the AC-connected devices (i-Socket vacuum switch and shore power inlet) were damaged. If that is the case, the energy jumped from the mast into the AC wiring, then to the shore power cord, and blew the breakers. Also, the not-connected-to-anything-but-the-transducer wire was severely damaged.

Regarding the shore power inlet, the hot and neutral pins on the female end of the cord were melted, ground pin undamaged.

Correction to DC system description: DC system includes solar panel and its charger, flooded lead acid batteries, and two bilge pumps with their separate switches/wires. The DC system seems to have been unharmed because bilge pumps still worked.

I guess it just demonstrates the capricious nature of a lightning strike or how variable the damage can be when there is no easy route for the lightning to travel. I did not have any kind of dissipation system in place: no masthead rod, not bonding wires, no immersed grounding plate, nothing.

[tkeithlu]

You're talking about 300 million Volts and about 30,000 Amps. That's well outside our comprehension. That charge will take all the available paths to ground. That's usually multiple paths, there not being many conductors that will handle the load by themselves. So, bits of it went everywhere in your boat. Tossing a paint can is child's play. Producing great volumes of pressurized steam wherever it hits water is easy.

Add to that your not having perfect knowledge of conditions just before and just after the strike. Are you absolutely sure that that valve moved during the strike? Maybe, but there will still be mysteries as to what that strike did.

So, test everything. Repair as needed. Marvel at the mysteries. Marvel at the awesome power of a hit. Create your happy hour stories to tell. Go sailing.

[team karst]

Originally Posted by scherzoja

…..



I guess it just demonstrates the capricious nature of a lightning strike or how variable the damage can be when there is no easy route for the lightning to travel. I did not have any kind of dissipation system in place: no masthead rod, not bonding wires, no immersed grounding plate, nothing.

Ur description of the mast to keel is popular. Great conduction right up-to, but not thru, the keel. Have u inspected the keel yet? Folks have seen hundreds of small holes after these events. But sometimes big holes too.
Popular theory suggests that lightning is more attracted to the surface of water (and land), rather than deep within.

[billgewater]

Consult Maxwell's four equations. Then seek out the appropriate Greek God.
Considering the minimal damage done, I would also consider purchasing a few lottery tickets as well.

[Emmalina]

Got a direct hit once melted everything Batteries and isolater switch were globs of plastic on the floor Only thing that survived was the led anchor light ??? and my inverter All the instruments exploded as did the autopilot.

[RiverRat37]

My experience (reading - both anecdotal and professional - and chatting but no first-hand experience) is that it's a fool's errand to try and determine exactly where and how the lightning travelled. It most definitely has a mind of its own and does whatever it pleases. It would actually appear (at times) to violate our laws of physics. The stories of "the impossible" are rampant.

One thing that appears fairly often is that it will ignore sharp turns and just 'shoot out' and go straight (more or less) until it finds a new route that attracts it. Nothing, absolutely nothing, is guaranteed to happen or not happen. It has a mind of its own.

I'm betting that in some cases (many?) victims of a 'hit' have figured out what happened and have it all wrong. Give it it's due.

[Bowdrie]

Originally Posted by RiverRat37

One thing that appears fairly often is that it will ignore sharp turns and just 'shoot out' and go straight (more or less) until it finds a new route that attracts it. Nothing, absolutely nothing, is guaranteed to happen or not happen. It has a mind of its own.

Yeah, in another thread I was relating a story/article from years ago of a boat in which the strike vaporized the mast wiring, blew out all the electronics, and exploded the batteries.
The icing on the cake: The charge went thru the engine and fused the main bearings on its path to the water via the prop shaft.

As an aside, in the early 1900s, (IIRC,) electrical service was first run to the town of Bodie Ca., (gold rush town, now a visitable ghost town,)
When the wires were strung, they put the poles in gentle curves, they were afraid that under high current demand the electrons would jump off the wires at a tight corner.

[garyfdl]

Originally Posted by RiverRat37

One thing that appears fairly often is that it will ignore sharp turns and just 'shoot out' and go straight (more or less) until it finds a new route that attracts it.

From what I've read, this is accurate. In looking at information on how to run ground wires from lightning rods etc. it is advised they be straight a possible, and if bends are necessary? They should not be less than 8" radius (IIRC).

[garyfdl]

A few years ago, a 27' Erickson in our harbor got hit. Blew all the through-hulls out! Our harbor is shallow so the boat didn't sink... completely. It settled about 8" and sat on the bottom. Owner lives out of town, and nobody noticed the boat sitting low in the water for a couple days (why are the dock lines so tight... HEY! where's the boot stripe???). Good new was, while the interior was flooded, the water level wasn't high enough to cause major damage/it did not flood the engine.

[bdgWesternMass]

Originally Posted by garyfdl

From what I've read, this is accurate. In looking at information on how to run ground wires from lightning rods etc. it is advised they be straight a possible, and if bends are necessary? They should not be less than 8" radius (IIRC).

My believe another interesting thing about the travel of the strike is that the leaders of the strike starts from the ground and goes to the sky.

it could be the charge started with the metal building and arc’ed its way to the clouds through the mast….

[garyfdl]

Originally Posted by bdgWesternMass

My believe another interesting thing about the travel of the strike is that the leaders of the strike starts from the ground and goes to the sky.

I think you're right and I'll go one step further... you can hear it! It sounds like a compressed air leak.

I've been (almost too) close to two strikes. First was back in the '70's working on a buddy's boat. T-storm was moving in, but it hadn't started raining, so we kept on working. Suddenly there was a loud 'HISS!', and then... FLASH/BANG! Lightning struck a nearby power pole. At that point we decided to retire to the yacht club and have a drink.

Second occasion was the one I mentioned (in another thread) where lightning hit my chimney. I was standing outside on a covered porch, watching to see if lightning would hit the church steeple across the street. There was the loud 'HISS!' I thought Oh CR[FLASH/BANG!]AP!

Now, when there's a T-storm I go inside, to the middle of the house... and sit in a Faraday cage.

[bdgWesternMass]

Originally Posted by garyfdl

I think you're right and I'll go one step further... you can hear it! It sounds like a compressed air leak.

I've been (almost too) close to two strikes. First was back in the '70's working on a buddy's boat. T-storm was moving in, but it hadn't started raining, so we kept on working. Suddenly there was a loud 'HISS!', and then... FLASH/BANG! Lightning struck a nearby power pole. At that point we decided to retire to the yacht club and have a drink.

Second occasion was the one I mentioned (in another thread) where lightning hit my chimney. I was standing outside on a covered porch, watching to see if lightning would hit the church steeple across the street. There was the loud 'HISS!' I thought Oh CR[FLASH/BANG!]AP!

Now, when there's a T-storm I go inside, to the middle of the house... and sit in a Faraday cage.

I wonder if that hiss is steam... I also wonder if the through-hull was opened by steam pressure build up.