Metal grounding plate for steel hull

Originally Posted by michael pierzga

So unpredictable that when sailing, I'm careful to use the radar to spot "cells" at 24 or more mile distance, simply so that I may alter course early and stand clear of any potential thunderstorm trouble. .

So you have a Doppler Radar on board hmm? Or even a polarimetric?

[michael pierzga]

And Ike...have a read and ponder lightning....unpredictable !!!!

http://www.dailymail.co.uk/news/arti...ours-boat.html

[Ike]

Actually sometimes I think I must be a lightning rod. I have been in near misses at least five times mostly in Utah.

1. 1979, driving through Utah on rt 191/6 about where Helper is. Totally flat except a small hill only 50 or so feet high next to an abandoned gas station. Storm came out of the west with lightning all around so I pulled into the old gas station because it had a covered area where the pumps used to be. Lightning struck the hill not more then 75 or so feet away. You could feel the static jump off the metal surfaces in the car. It scared my kids so much they were screaming.

2. 1980, Utah. Big storm. Lightning struck the tree behind my house not 10 feet away. It knocked me and my family down and I couldn't hear a thing for at least 15 or 20 minutes after. The tree exploded. It split down the middle. It was a very big Oak.

3. 1981 Utah again. My son and I sailing on a reservoir surrounded by mountains. A big storm came over the mountains with lots of wind, rain and lightning, so we immediatley headed for shore, We were just about there and could see lightning, multiple strikes hitting the lake. One hit about 1/4 mile away. My son had his hand on the metal shroud (This is otherwise a totally wood boat) and got one hell of a shock.

4. 1981 Leaving Utah (Utah doesn't like me) from Salt lake west on I-80 the storm raged all the way from Salt Lake City to State Line NV. Lightning struck all around us, so many times I lost count. it all stopped when we crossed the Nevada border. Is that freaky or what!

5. Maryland 1986: lightning struck the house next door which was unoccupied. But it fried my television. Fortunately my computer was unplugged at the time, but that TV was smoking.

from 1991 to 2004 I lived in Virginia in what is called thunderstorm alley. Fortunately no near misses, although it did fry the substation about 1/2 mile away.

Since then nothing that close. But now I stay away from areas with lots of thunderstorms

As you said, unpredictable!

Frankly, I'll take a good earthquake or hurrican over lightning

[michael pierzga]

Me too !!!!!!!!!!!!!!!!!!! particularly at sea when you realize that you are the tallest and only object around. Interesting that there seems to be few tragic lighting strikes on yachts. Seems to only advice is to follow industry standard and make sure any blast can escape from the yacht fast. The superyacht which burnt up in Antigua a couple years ago, at the dock, was quite sophisticated and surely must have had preventive details fitted. She was destroyed.
Also good to be lucky !

[CDK]

It is a general misconception that lighting always comes from the sky and hits tall objects on the surface. If that were the case, TV and cell phone antennas would be destroyed after every thunderstorm.

It has been established by ultrafast photography that most discharges start at the surface. Most have multiple cores of ionized air (dark blue), as soon as the conductivity is sufficient, one of these cores carries the full discharge current. Only that one ( bright white) we recognize as lighting. The blue plasma cores can occur quite near a tall object that comes out unscathed.

That is why a tall sailing yacht can miraculously escape while a nearby fishing boat is blown to pieces.

[gunship]

I am no electric engineer, but if i'm not misminded electricity travels from - to +, strange enough...

[michael pierzga]

Sounds logical to me CDK. One year , on a black lightning charged night, we were sailing close to the active volcano Strombloi, just north of the Messina Straits. Lighting appeared to be originating from its volcanic cloud and flashing against the low cloud cover. .Very dramatic...Dantes Inferno

Originally Posted by michael pierzga

The superyacht which burnt up in Antigua a couple years ago, at the dock, was quite sophisticated and surely must have had preventive details fitted. She was destroyed. !

The Keturah, you refer to, was a carbon fibre boat of 94ft LOA.!

What eventually burned her up was never finally found during investigations. She burned for over 30 hrs.

[CDK]

Originally Posted by gunship

I am no electric engineer, but if i'm not misminded electricity travels from - to +, strange enough...

Fully correct Gunship, the negative side is where the most electrons are.

[singleprop]

If the recommendations from Marinelightning.com is to be followed some metal strips should be welded onto the hull side (under water). What material woud be best suited for this: 316L, Monel etc.....