>> ...but grounding it also makes it attract lightning.   As there are now many 
>> grounded boats,  It's now likely that the safe boats are the ones not 
>> grounded.   <<

This statement differs from my understanding, granted I am no expert but I have 
read much on the topic and have sailed (mid-Pacific, Lake Ontario, and Puget 
Sound) with lightning striking the water within sight.

The theory I put the most stock in refers to the difference in potential 
between the boat and the static charge (lightning's energy).

For example; if the ocean around your boat all has a plus 2 charge (++) and 
your mast has a plus 4 charge (++++) then the mast looks better than the near 
by water.  When underway and faced with a lightning storm I would drag jumper 
cables, chain, large gauge wire etc over the side with the other end attached 
to Calypso's rod rigging.

My expectation is connecting or bonding the sea to the mast would equalize the 
potential between them reducing the attractiveness of the mast to the lighting 
energy.

I am most interested in any experiences that support or refute this strategy in 
advance of my next lighting storm sail.

Martin
Calypso
1971 C&C 43
Seattle

-----Original Message-----
From: [email protected] [mailto:[email protected]] On 
Behalf Of [email protected]
Sent: Wednesday, August 29, 2012 1:27 PM
To: [email protected]
Subject: Stus-List Isaac: Lightning on the hard

Hi,

On Saturday, the weather predictions had Isaac a cat 2 hurricane heading right 
for us.   The travel lift at my marina was working over time, and by afternoon 
the boat yard ran out of stands and were only hauling out those who had their 
own stands.   My boat remained at the slip, and I prepared for the storm.    
Fortunately for us, the path went more to the west, and we experienced tropical 
storm winds and a 5-6 foot surge.  

The only damage occurred to a sailboat which was hauled out.   It was struct by 
lightning which blew out two transducers in the hull and burned a line along 
the hull from the keel forward to a chain which cross-connected the forward 
metal stands( due to the full keel, the chain actually touched the bottom of 
the hull).   The keel was stepped on wooden blocks so it appears that the 
easiest electrical ground path was through the stands.    

In short time, this incidence inspired many to ground their boats.  One guy, 
actually has battery cables connecting his shrouds to a piece of rebar pounded 
into the ground.  I never though much about grounding (or bonding) a boat on 
the hard before, but I am not yet convinced that it is a good thing.  Yes, if 
my boat is hit by lightning, I would want it well grounded, but grounding it 
also makes it attract lightning.   As there are now many grounded boats,  It's 
now likely that the safe boats are the ones not grounded.   



-
Paul E.
s/v Johanna Rose
Carrabelle, FL


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