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Old 31 July 2006, 16:59   #1
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Lightning at Sea!

I had my first experience of lightning at sea yesterday just East of Jura.

Blue skies quickly became black followed by hailstones, the wind got up and the wave height increased significantly then had a number of lighting strikes at the sea under a mile away from the boat!

I was somewhat concerned and tried to get out from under it as quick as I could.

I was conscious that when standing I was the highest point on the boat (had a low a-frame to fit in the garage and use a short vhf antenna) so despite the heavy sea's I tried to stay as low as I could. Should I have unplugged the electronics?

I do not intend to go out in lightning again, though if I am unlucky enough to be caught, just wondered what is best precautions to take - apart from the obvious: do not go out in lightning.
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Old 31 July 2006, 18:28   #2
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Anchor chain tied round the a-frame and dangle the anchor in the water - oh and electrics off.
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Old 31 July 2006, 23:39   #3
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Electrics on or off, they'll be fried if you're struck. Many boats have been struck in local harbors recently, many thousands of $$ in damage to electronics. Witinessed a boat struck maybe 300 meters away just Friday evening... massive shower of sparks, incredible crack of thunder. Closest I've ever been to a strike, frightening... Toasted electronics are not the big concern if YOU'RE on the boat at the time!

Best bet is to keep a weather eye, and head away from the storm cell, you should be able to navigate around them, I have in the past, in a 5 knot sailboat, a 35+ knot RIB should make it a bit easier.
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Old 01 August 2006, 04:25   #4
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The engine is grounded into the sea so the charge should find its way to earth through this, likely taking out the electrics also.

The fire service attended a "small" fire at our place recently and showed us a sample of phone cable that had been struck - There was no conductor left inside the insulation and the insulation had ruptured every 25-50mm (1" to 2") presumably to let the copper/ali vapour out.
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Old 01 August 2006, 06:10   #5
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Originally Posted by Simon B
The engine is grounded into the sea so the charge should find its way to earth through this, likely taking out the electrics also.
I am under the impression the current runs from earth up to the clouds.

Electricity likes sharp edges and points.
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Old 01 August 2006, 12:59   #6
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Originally Posted by jwalker
I am under the impression the current runs from earth up to the clouds.

Electricity likes sharp edges and points.
Usually but you can get + or - charges with lightning. Even worse you can get ligtning that switches between + and - so you don't know where the hell you are with it.

Used to be a bit of a passion of mine messing around with Tesla coils etc - with my new den I may just start experimenting again!!!
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Old 01 August 2006, 13:24   #7
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St Elmo

If you have ever experienced St. Elmo's fire in an electrical storm storm you will REALLY know how wierd storms can be. I did, only once, right in the middle of the Bermuda Triangle and it was accompanied by 270 degree sheet lighting going from cloud base to sea surface. Pucker cord got really tight. Flashes and blue streaks in the air inside the cabin of the boat and at the the same time trying to get and RDF heading on St. George, Bermuda. Will try not to do that again.
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Old 01 August 2006, 18:45   #8
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Originally Posted by dctucker
Electrics on or off, they'll be fried if you're struck.
Agreed.

I don't think people appreciate the shere amount of power in a lightning bolt.

The break/gap produced by a battery isolator or switch, will be little defence againt the might of a lightning bolt.

If it's managed to jump from clouds at ??? feet altitude to ground, what possible difference will a 5mm gap in a contactor make??
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Old 01 August 2006, 20:40   #9
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Quote:
Originally Posted by Jonny Fuller
Agreed.

I don't think people appreciate the shere amount of power in a lightning bolt.

The break/gap produced by a battery isolator or switch, will be little defence againt the might of a lightning bolt.

If it's managed to jump from clouds at ??? feet altitude to ground, what possible difference will a 5mm gap in a contactor make??
Yep. One of my previous work's vans was struck in France in May. I wish I'd taken a photo of the electrics when it came back-they were exactly as described earlier.

Surprisingly, the guy managed to drive it back though he did have to get a bumpstart off the ferry. Diesels do have their advantages...
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Old 02 August 2006, 14:01   #10
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Quote:
Originally Posted by Jonny Fuller
Agreed.

I don't think people appreciate the shere amount of power in a lightning bolt.
great scott!! 1.21 gW (name that film??)

jon is entirely right, switches do not stand a hope in hell. Once had the joy of trying to repair a stereo struck by lightning! Not a sausage left and non of the switches did a dicky bird!
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