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(JAXAshby) wrote in message ...
they don't begin to get struck 1 time in 20 storms. not even close.

Out of curiosity, I did a quick back of the envelope estimate of the
probability of a lone sailboat getting hit by lightning in a
thunderstorm.

Assume LONE sailboat, Flat conducting ocean, assume the mast is well
grounded, assume lightning equally distributed over the thunderstorm
area.

Now, I have forgotten how to do this calculation (this used to be my
speciality) but I vaguely remember that a spike type conductor above a
grounded plane produces minimal effects more than 3X its length away.
This means that a mast produces an EFFECTIVE AREA (a) of pi*9*l^2
where l = mast length.

BTW, I work in meters.

I assume a thunderstorm diameter of 4 km based on driving through one
two days ago for a total storm area of 12X10^6 m^2. I assume the
lightning strike rate is about 3/minute and the storm lasts for 40
minutes for a total number of strikes/storm (n) to be 120.

SO...the probability of getting hit is: P=n*a/A *L (L is your "luck
factor", 0L1 means you are either optimistic or lucky, L=1 means you
do not believe in Luck, L1 means you are pessimistic or unlucky, L=0
means you dont really sail). Top of my mast is 17 m above water for
an effective area of 7803 m^2.

So, P= 120*7803/16X10^6 *(L) = 585225X10^-6 * (L)= .058 * (L) or 5.8%
* (L).

Based on limited experience with games of chance, I estimate my L = 3
so my strike probability is 17.4%.

Seriously, the 5.8% chance shows why sailboats do not get struck more
often although they are the tallest things around.

you need to pay attention to the assumptions I made. I assume a LONE
sailboat underneath a thunderstorm. This happens fairly rarely for
most of us, even those of us who live in the lightning capital of the
world. If there are other objects within the effective area of a
sailboat, then the probability of being struck is divided between
them. Furthermore, most of us avoid being directly under a well
developed thunderstorm or we minimize our time under such a storm.
Next, the cloud to ground strike rate may be less for some storms.
The thunderstorms I have seen up north are not REAL thunderstorms by
my perspective but are often fairly wimpy compared to those driven by
very warm water or very warm plains. If you ever get in such a REAL
thunderstorm, you will see why some of us make such extreme efforts to
avoid them.

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