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Richard Casady

On Wed, 20 Aug 2008 19:27:06 -0400, wrote:

On Wed, 20 Aug 2008 15:01:04 -0700 (PDT),
wrote:

In another thread some mentioned lightning protection. There seem to
b e several schools of thought on the topic ranging from preventing a
strike to dissipating it when it happens. I really do not think there
is much you can do to prevent a strike on a sailboat except to be in
proximity to other tall objects. When you consider the voltages
involved, everything becomes a conductor which is why a tall tree gets
hit as often as a tower of the same height. I also do not think that
lightning dissipators work. In fact, they may make you more
susceptible to a strike by increasing the E field in its vicinity.
Given that the water is so murky on the subject of protection,, I
favor getting rid of it after a strike and attaching a small conductor
to your hull isnt the best way. You may end up with a hole in your
hull. Instead, I have a 2'X2' copper plate soldered and bolted to 00
gage tinned battery cable 20' long with an eyelet on the other end.
When in a storm, I throw the plate over the side and attach the eyelet
to the mast up high so as to minimize bends in the cable. I want to
have the current go through the cable while having the shrouds help
protect us inside them.
I once did a calculation on the probability of a lone sailboat getting
hit if out in a storm and came up with a number that seemed too high
yet when compared with insurance statistics turned out to be
reasonable. Basically, you should avoid being the only tall thing
under such a storm. Being one of many tall things is ok

I am always curious about how a boat takes a hit but I do have some
experience with a lightning rod. I put a 3' copper rod over my weather
station with a pointy stainless steel tip, connected to 2ga copper
wire and terminated in a ground rod (connected to my extensive house
grounding system)
It has been hit twice that I know of and I was about 30' away during
one of them. A mexican laborer was pretty much under it, plastered
against my garage door. Other than the poop reflex we were totally
unaffected.. The steel garage door he was plastered to is bonded to
the same grounding system as the lightning rod as is the wet concrete
driveway I was standing on.
We were fine. The weather station ... not so much ... either time.

000 wire and a ten foot long grounding rod, is the customary practice
with lightning rods.

Casady

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