lightning at anchor

C

Coach T

New member
Long story short. Over the weekend my wife and I had a lightning storm come through around 2 am. Normally I would seek shelter but this was the first time we encountered a storm while sleeping. We were in a protected cove (from waves and wind) but obviously not lightning
Any suggestions on safety on a cdory? Best practices?
Thank you in advance.
 
Far more experience with lightning than you want to know about--including strikes to my person (minor lobe), and boats.

Basically in C Dory: All antennas down. All electronics unplugged from power, ground, transducers. Stay away from any metal object in the boat (including steering gear). I would want engine out of water in trimmed up position.

If underway, probably best to anchor in protected area. If there are tall trees nearby, probably best, but no guarantee.

Remember that lightning may travel thru the water, as well as the air.

Stay below. In the bunk is probably the best place in the boat. Stay away from any of the electrical wiring.

If you need examples,--I am happy to provide. When in lightning areas, we generally have a steel ammo box with a hand held GPS and hand held radio. The ammo box acts as a Faraday Cage. We had a large freighter contact us on a hand held radio about 80 miles off Charleston, asking for a position. All electronics, radios etc were out, as well as navigation gear (before GPS, but we had both Loran C, Omega, and Sat Nav, so could give him a position within a few hundred yards) He had the hand held radio in a steel locker and it survived the strike.
 
What a resource we have in Dr. Bob!
Thank you so much, Bob, for sharing your vast experience in such a clear and concise manner. I have learned so much from your postings, as have we all.
Thanks,
Carpy
 
Just find a taller, preferably all aluminum boat and anchor near that. If you're out hiking, hike near Dr. Bob. He's quite tall and looks like a good conductor to me (although he may get suspicious when you start rubbing the conductive jelly on his hat).

But seriously, it's great to have Bob on the site. I too have learned a lot from him.
 
Lightning is a bit unnerving I think we all have a story to tell. Base purely on speculation reducing your profile seems like a good idea but I'm not so certain anymore. We had a lighting strike to house that skipped the power poles and lines but instead zeroed in on the gas meter on the side of the house. That in turn burned off the power lines causing a added degree of difficulty to the fire that extended into the attic. Now nobody was injured that was inside the house so one could argue that shelter or pilot house in our case is a good idea.

Scary as its impossible predict its behavior.
 
Scary as its impossible predict its behavior.
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Absolutely. One incident, my Cal 46 (57 foot Aluminum mast will full lightning protection had just been sold, but still at our dock. I was in S. Florida shopping for a trawler) A lightning bolt, hit the power boat about 60 feet away, traveled thru its VHF antenna, and did moderate damage to that 44 foot trawler. A "lobe" came thru the water, and the only damage was to the diodes on the regulator of the engine alternator. (This caused the battery charger to be pouring 50 amps DC into the ground system of the boat, and destroyed most of the bonded thru hulls, the rudder post, prop, and shaft, in about 2 weeks). That lightning did not hit the 57 foot aluminum mast, my ham antenna, was about 70 feet from the boat, and was about 18 feet higher than the sailboat mast--and fully grounded. So, no protection from the high ham antenna, no "bleeding off" of the charge by the dissipator, on the top of the sailboat mast, (properly grounded to a several sq foot piece of copper on the keel of the boat.) but hit a small VHF antenna, and then traveled thru the water to cause damage!

Another incident--I was with a friend on a 38 foot trawler, a storm came up. He poo pooed my suggestion we get below and anchor. His "solution" was to get about 10 feet behind a sailboat under way, thinking that the sailboat mast would protect him…..well, the sailboat took a direct hit, with serious damage, and a lobe jumped to the boat I was on's Bimini frame, and then arced to my shoulder about 6" away.

We were in a harbor in the old Yugoslavia. We had the tallest mast--about 20 other boats anchored there. I had chains into the water from each chain plate, and the bob stay fitting had part of the SS weldment in the water. We had "Saint Elmo's Fire in the rigging", but no direct strike. Only damage was a couple of diodes in the wind instruments. Several other boats in the harbor had direct strikes. There were over 100 strikes in an hour within a mile or so radius.

This is why I strongly agree with Chris!
 
So my question is, with this never ending amount of boating knowledge and experience (which is much appreciated), when did Dr. Bob have time to be a doctor??? :)
 
My experience. I had an F-31 trimaran, 40 ft mast, previous boat to my CD-25. I trailered it to the Bahamas with a group of 5, same boat. Before we left home, we all discussed the possibility of a lightening strike and what gear/mods we should do to our "plastic" boats for safety. Decided to do nothing (always easiest plan...), but we did read up about disconnecting all electronics and metal contacts with the water (outboard motor, etc). We had a tropical depression come through at 4am while anchored in a cut in one of the smaller cays (pronounced "keys"). So here we are, 5 trimarans with 40ft, ungrounded aluminum masts, along with maybe 5 or more other boats, sail and power. We said a lot of prayers that morning, and also for the unknown direction of wind and waves, etc. There was one boat, a twin masted schooner, perhaps 50-75ft long about 200 ft away, fully grounded with copper plates into the water. Yep, it got hit hard, blew off the top of the primary mast with antenna and other electronics, quite a 4th of July show. No other boat was hit, it was a quick lightening event.

Lightening seeks the lowest resistance path to ground. But...it doesn't always follow the rules in the vicinity, probably due to air currents and other factors where it doesn't exactly find the "best" and easiest path to ground. Dr. Bob's recommendations are spot on, should print them and place in a safe place in your boat.
 
Fiberglass ladders are suppose to be safe around electric services,and when I worked a few years in line work I believe we used fiberglass strain insulators to keep electric from traveling to ground and other areas. So why then are fiberglass boats not safe ,since fiberglass is more of an insulator than a conductor? If in saltwater hull covered in salt then it makes sense,just wondering why its so dangerous in boat which I believe that it is? Just wondering your safe in a car but not in a boat. Aluminum boats would seem bad but why is fiberglass? Glad for suggestions of taking down antennas and trimming motor up. This will be our first trips overnighting out in conditions at anchor ,so I am listening to this post for tips. Last week we saw on wundermap a big storm coming on I-Pad. It was coming from our marina area we outran it by going up the lake . Major rainfall occurred as we could see giant puddles in parking lot when we got back. It was fun dodging the storm.
 
Yes, fiberglass is a good insulator, but if you ever see the damage from a direct hit, you would understand that as the lightning:

An average bolt of negative lightning carries an electric current of 30 kiloamperes (kA), and transfers a charge of five coulombs and 500 MJ of energy. Large bolts of lightning can carry up to 120 kA and 350 coulombs. The voltage is proportional to the length of the bolt.

An average bolt of positive lightning carries an electric current of 300 kA or about 10 times that of negative lightning.
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Fresh water in some ways is worse than salt water--so don't count on being "safe" just because you are in fresh water!

Air is a great insulator--and it beaks down as this huge amount of energy travels to the earth. So does the fiberglass, if there is a direct hit. It can the railings on the top of the cabin, the radar arch, or any antenna--as per my example above. As the lightning energy gets into the boat, it travels in the paths of least resistance--other railings, wiring (12 volt, 110 volt, wiring of the electronics including transducers, Radar cables, etc) As Chris and Dora Jean points out, the objects in its path basically vaporize. I have seen fiberglass boats which have had significant damage from the lightning. Generally the damage is close to metal fittings, but the energy goes thru the glass, breaking it down--just as art is formed in the sand, when steel rods are driven into it.--by the energy melting the sand, and glass/resin. Below is damage from an anchor well drainage above water, which was hit by lightning.

lightning.03.jpg


Worse with polyester, it burns well, even when cured:

Cape-Boat-Fire-938x535.jpg
 
I used to have a Corinthian Sailstar (which I miss). I kept an automobile jumper cable in the boat, and when anchored, clipped one end to a metal shroud, and tossed the other end in the water. I never got struck by lightning, but I'll never know whether it was the jumper cable that saved me. I've never done anything on my C-Dory except lower the VHF antenna. I do toss a sacrificial zinc over the side with an alligator clip to the metal on the engines when I'm in a marina, but that's for electrolysis, not lightning protection.
 
localboy":2i4ga5qp said:
So what would happen if the hand held were NOT in a steel ammo box? Say, just lying on a shelf on the boat or in the V-berth?
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It depends on how close of a strike you get. Even if you don't take a direct hit, lightning can damage electronics through an electromagnetic pulse (EMP) effect. So... if your equipment is not protected and lightning is nearby, there's always the potential for damage. A hand-held radio and hand-held GPS in a metal box is not a bad idea.
 
I like the idea of a handheld VHF and GPS in a metal box for lightening protection. I'm not sure I like the idea of a metal box on board. I really work at keeping magnetic or steel anything off the boat. Just trying to keep it away from the AP direction sensor and the KVH compass.

Harvey
SleepyC :moon

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