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Lightning.....wow!

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glivs
Admiral

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USA
822 Posts

Initially Posted - 09/18/2021 : 17:25:26

Stopped by my winter storage yard yesterday and in talking with their fiberglass repair tech he relayed the following. In mid-August a late evening T-storm passed through and within minutes three boats 30-34' in length were struck by lightning and totaled. Based on footage from a cam camera at the marina it appears one lightning strike hit two boats in succession, striking the mast of the first and then traveling horizontally about 200-300 yards to the mast of the second boat. The third boat was about a 1/4 mile away in the opposite direction and thus not in the camera's view. The timing of the call reporting the strike, however, suggests it was struck very soon after the first two boats.

The commonalities....no one was aboard or injured, all were totaled; all were moored; the first two boats were adjacent but on the edges of their respective mooring fields with a wide entrance channel between them, the third was an isolated mooring; all were bonded and the worst damage realized was where the bonding cables made a sharp turn (even a kink in the wire) or terminated; all electronics on each boat were destroyed.

The first boat was owned by the marina tech and suffered considerable damage with several "quarter-sized" or larger holes along the length of the bonding cable but especially near the rudder post where the bulk of the charge appeared to exit. The boat almost certainly would have sunk but marina personnel were called and responded quickly to move the boat to their travel lift.

The second boat suffered a large "spider-web" array of seemingly countless tiny holes in the hull below the water line although the largest holes were near each of the through hulls. Water intrusion was slow but again the boat was pulled as soon as was possible. The tech noted he had repaired a boat with much less damage a few years ago and discovered that although the holes on both the inner and outer surfaces may appear small, the damage to the fiberglass sandwiched between can be quite extensive.

Less was known about the third boat other than again the damage appeared to be a scattering of tiny holes throughout the bottom of the hull.

Wow....what a way to end a day. Reinforces my take to not be on the boat in a T-storm if at all possible.

Gerry & Leslie; Malletts Bay, VT
"Great Escape" 1989 C-25 SR/WK #5972

Steve Milby
Past Commodore

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USA
5851 Posts

Response Posted - 09/18/2021 : 18:23:21

Interesting. It suggests that grounding everything on the boat is of dubious value, and that doing so might actually increase the likelihood of a strike. Certainly doing a bad job of grounding is worse than not doing it at all. Most strikes seem to happen when the boat is stationary. Makes you wonder if a moving sailboat somehow reduces the likelihood of a strike, perhaps by continuously discharging static electricity, or on the contrary, by creating an opposite charge that tends to repel lightning strikes.

Steve Milby J/24 "Captiva Wind"
previously C&C 35, Cal 25, C25 TR/FK, C22
Past Commodore

Edited by - Steve Milby on 09/18/2021 18:24:20

Voyager
Master Marine Consultant

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USA
5231 Posts

Response Posted - 09/18/2021 : 18:36:47

I used to think, �Ha! You can outsmart lightning. All you need is some honkin� #4AWG wire bonded to a 2SQFT hull plate. No problem.
Then I watched lightning striking all around the harbor one day. We had one of those storms where it�s almost continuous lightning and thunder. Raining horizontally. Terrifying! In that case, it doesn�t matter what you do in the situation, you�d just better bend wa-a-a-ay over and kiss your boat goodbye. Literally Russian Roulette.
Nature Rules!!!

Bruce Ross
Passage ~ SR-FK ~ C25 #5032

Port Captain � Milford, CT

Steve Milby
Past Commodore

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USA
5851 Posts

Response Posted - 09/18/2021 : 20:12:33

Sailing through lightning used to scare the crap out of me and it still does, but, when you're cruising 30 miles from your marina, you can find a cove to anchor in during a thunderstorm, but you'll still be on the boat. Realistically, you can't get away from it, so you just keep on sailing and trust it won't strike you, because there's no alternative. I slept on my boat through countless thunderstorms in my marina for many summers and was never struck, although it struck frighteningly nearby, but what's the alternative? Get up at 3 am every time there's a storm, get off the boat barefoot and in your skivvies and run to your car in a driving rain? Not very realistic. So, you put it out of your thoughts, roll over and go back to sleep.

Steve Milby J/24 "Captiva Wind"
previously C&C 35, Cal 25, C25 TR/FK, C22
Past Commodore

glivs
Admiral

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USA
822 Posts

Response Posted - 09/19/2021 : 04:28:04

Sample size of three, but I was struck by the fact that each boat was on the edge of their mooring field or isolated. Of the 100+ boats immediately nearby, none in the centers of their mooring fields or in their marina slips were hit. I wonder if the grouping somehow effects the local charge field.

Gerry & Leslie; Malletts Bay, VT
"Great Escape" 1989 C-25 SR/WK #5972

Voyager
Master Marine Consultant

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USA
5231 Posts

Response Posted - 09/19/2021 : 21:10:30

Kinda like the school of bait fish. The few outside fish get eaten by the predator fish and all the rest have a really n ice day.
Steve, for liveaboards in Florida and the tropics where it might thunder and lightning every day during monsoon season, you just deal with it. Probably nothing else you can do.

Bruce Ross
Passage ~ SR-FK ~ C25 #5032

Port Captain � Milford, CT

Stinkpotter
Master Marine Consultant

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Djibouti
9013 Posts

Response Posted - 09/20/2021 : 21:52:15

Friends who moored their C-30 in a Bridgeport, CT harbor found all of their electronics fried, and the boat otherwise unharmed... Somebody at the club reported a strike hit the water less than 100' from the boat. The C-30 was not grounded other than by the inboard prop-shaft, with no bonding system. The electronics damage was apparently caused by the magnetic pulse surrounding the strike.

I've never been convinced of bonding, grounding, etc... It seems almost any system (other than the kind installed on the Empire State Building) is likely to be overwhelmed by the instantaneous 30,000 amps in a typical strike. Apparently the turning radius of the electrons under 3 million volts is too great for the bends in typical grounding system cables--the electrons just fly off the bends and crash through the hull. I figured the deck-stepped mast and wood compression post on my C-25 created a dry insulating space between the mast and the water, which seemed like an advantage... Why connect them??

Dave Bristle
Association "Port Captain" for Mystic/Stonington CT
PO of 1985 C-25 SR/FK #5032 Passage, USCG "sixpack" (expired),
Now on Eastern 27 $+!nkp*+ Sarge

Edited by - Stinkpotter on 09/20/2021 22:01:02

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