(JAXAshby) wrote in message ...
pair of lox, a 5% chance of getting hit = a 95% of NOT getting hit.

A 5% chance of getting hit = .95 times .95 = a 90% of NOT getting hit even
once EITHER time in two tries.

a 5% chance of gettting hit = .95 times .95 times .95 times .95 = 81% of NOT
getting hit even once in FOUR tries.

by 8 tries the chance of NOT getting hit is only about 2 out of 3, by 14 tries
there is a better than even chance of being hit **AT LEAST ONCE**. by 30
tries, the chances of being hit at least once are 4 out of 5. by 50 tries,
chances of being hit at least once are greater than 15 out of 16. by 70 tries,
32 out of 33. by 90 tries, greater than 99 out of a 100.

that oak tree standing on the hill would be toothpicks by the end of the second
season.

Understand that in central Florida they receive more than 100 electrical storms
each year. a 5% chance of getting struck would mean central Florida has never
had trees.



How do you define "effective" area?
Your equation assumes that any lightning within the effective area of your
boat will strike your boat. If that were the case I'd be very afraid.

"Parallax" wrote in message
om...
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.

...

I found a web site that gave a strike rate of about .5 strikes/km^2/yr
but they did not say where they measured this. However, this means
that a lone sailboat with a mast 17 m tall would have a .35% chance
each yr of getting struck. This is an ideal situation though and may
not address the situation of a sailboat under a thunderstorm where the
strike rate/km^2 is hundreds of times higher. Because I know that the
strike rate in Fl is much higher than average, I'd want to double the
strike rate they give to be about 1/km^2/yr. This gives about a .7%
chance each yr of getting hit. Again, this does NOT address the
situation where you know the strike rate is much higer than average
(sitting under a storm). Based on math and observed strike rate, I
still think my estimate is good.








For further local perspective on the strike rate, consider that in my
own back yard of 1 acre, while I have lived here (15 yrs) three trees
have been hit with two being killed. My well enclosed in a shed was
struck. My neighbors well has been struck three times although it is
below ground. JAX, you just dont know lightning.

BE CAREFUL, PAIR OF LOX!!! YOU ARE GOING TO DIE A CRISPY CRITTER!!!!!!!

For further local perspective on the strike rate, consider that in my
own back yard of 1 acre, while I have lived here (15 yrs) three trees
have been hit with two being killed. My well enclosed in a shed was
struck. My neighbors well has been struck three times although it is
below ground. JAX, you just dont know lightning.

(JAXAshby) wrote in message ...
pair of lox, a 5% chance of getting hit = a 95% of NOT getting hit.

A 5% chance of getting hit = .95 times .95 = a 90% of NOT getting hit even
once EITHER time in two tries.

a 5% chance of gettting hit = .95 times .95 times .95 times .95 = 81% of NOT
getting hit even once in FOUR tries.

by 8 tries the chance of NOT getting hit is only about 2 out of 3, by 14 tries
there is a better than even chance of being hit **AT LEAST ONCE**. by 30
tries, the chances of being hit at least once are 4 out of 5. by 50 tries,
chances of being hit at least once are greater than 15 out of 16. by 70 tries,
32 out of 33. by 90 tries, greater than 99 out of a 100.

that oak tree standing on the hill would be toothpicks by the end of the second
season.

Understand that in central Florida they receive more than 100 electrical storms
each year. a 5% chance of getting struck would mean central Florida has never
had trees.



How do you define "effective" area?
Your equation assumes that any lightning within the effective area of your
boat will strike your boat. If that were the case I'd be very afraid.

"Parallax" wrote in message
om...
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.

...

I found a web site that gave a strike rate of about .5 strikes/km^2/yr
but they did not say where they measured this. However, this means
that a lone sailboat with a mast 17 m tall would have a .35% chance
each yr of getting struck. This is an ideal situation though and may
not address the situation of a sailboat under a thunderstorm where the
strike rate/km^2 is hundreds of times higher. Because I know that the
strike rate in Fl is much higher than average, I'd want to double the
strike rate they give to be about 1/km^2/yr. This gives about a .7%
chance each yr of getting hit. Again, this does NOT address the
situation where you know the strike rate is much higer than average
(sitting under a storm). Based on math and observed strike rate, I
still think my estimate is good.








The Florida Sea Grant Programs paper "Lightning and Sailboats"
estimates that between 4% and 20% of sailboats moored in FL get struck
each yr. Mooring is very close to the case of being a LONE sailbaot I
describe. This is well in accord with my estimates.

Various web sites show the FL strike desnity being 10-30 strikes/km^2.

A LONE tall tree with 5%/yr chance of being struck could live at least
15 yrs having less than 50% chance of being hit. Note that in Central
Florida, there are few tall hills and fewer with lone tall trees.

My analysis appears to be correct.

pair a lox, wanna tell us again about your EE degree in physics? your estimate
does not match up with the math you use to portray your estimate. fine EE you
are, and in physics yet.

btw, if 4% to 20% of all sailboats mooring in the State of Florida get struck
by lightning each year, no insurance company on the planet would insure any
boat in the State of Florida without a HUGE increase in premium as compared to
the State of Georgia or the State of Alabama or the State of Texas of the State
of ...


The Florida Sea Grant Programs paper "Lightning and Sailboats"
estimates that between 4% and 20% of sailboats moored in FL get struck
each yr. Mooring is very close to the case of being a LONE sailbaot I
describe. This is well in accord with my estimates.

Various web sites show the FL strike desnity being 10-30 strikes/km^2.

A LONE tall tree with 5%/yr chance of being struck could live at least
15 yrs having less than 50% chance of being hit. Note that in Central
Florida, there are few tall hills and fewer with lone tall trees.

My analysis appears to be correct.

(Parallax) wrote in message . com...
(JAXAshby) wrote in message ...
pair of lox, a 5% chance of getting hit = a 95% of NOT getting hit.

A 5% chance of getting hit = .95 times .95 = a 90% of NOT getting hit even
once EITHER time in two tries.

a 5% chance of gettting hit = .95 times .95 times .95 times .95 = 81% of NOT
getting hit even once in FOUR tries.

by 8 tries the chance of NOT getting hit is only about 2 out of 3, by 14 tries
there is a better than even chance of being hit **AT LEAST ONCE**. by 30
tries, the chances of being hit at least once are 4 out of 5. by 50 tries,
chances of being hit at least once are greater than 15 out of 16. by 70 tries,
32 out of 33. by 90 tries, greater than 99 out of a 100.

that oak tree standing on the hill would be toothpicks by the end of the second
season.

Understand that in central Florida they receive more than 100 electrical storms
each year. a 5% chance of getting struck would mean central Florida has never
had trees.



How do you define "effective" area?
Your equation assumes that any lightning within the effective area of your
boat will strike your boat. If that were the case I'd be very afraid.

"Parallax" wrote in message
om...
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.

...

I found a web site that gave a strike rate of about .5 strikes/km^2/yr
but they did not say where they measured this. However, this means
that a lone sailboat with a mast 17 m tall would have a .35% chance
each yr of getting struck. This is an ideal situation though and may
not address the situation of a sailboat under a thunderstorm where the
strike rate/km^2 is hundreds of times higher. Because I know that the
strike rate in Fl is much higher than average, I'd want to double the
strike rate they give to be about 1/km^2/yr. This gives about a .7%
chance each yr of getting hit. Again, this does NOT address the
situation where you know the strike rate is much higer than average
(sitting under a storm). Based on math and observed strike rate, I
still think my estimate is good.








The Florida Sea Grant Programs paper "Lightning and Sailboats"
estimates that between 4% and 20% of sailboats moored in FL get struck
each yr. Mooring is very close to the case of being a LONE sailbaot I
describe. This is well in accord with my estimates.

Various web sites show the FL strike desnity being 10-30 strikes/km^2.

A LONE tall tree with 5%/yr chance of being struck could live at least
15 yrs having less than 50% chance of being hit. Note that in Central
Florida, there are few tall hills and fewer with lone tall trees.

My analysis appears to be correct.

As an experiment to test whether JAX believes what he says, I propose:

JAX come sailing here in N. Florida in thunderstorms of MY choosing.
He will get a choice of various boats but we remove any grounding
system and replace them with a system where he completes the circuit
across his chest. Prior to sailing (while I remain on shore
videotaping for everyones amusement), he takes out a term life
insurance policy with me as beneficiary for gretaer than the value of
the boat plus $50,000 (I will pay for this policy).
After emerging unscathed from each storm, i will buy him dinner and
pay his hotel bill for the night (we have to have a thunderstorm each
day I pay). After only 11 storms, i will thank him, pay his plane
ticket cost plus $1000 and agree that he is a great sailor. He can
then go back and tell everyone what cowards those Florida rednecks are
and I will agree. Furhtermore, If JAX is worried about sailing in
thunderstorm wind (I am) then he can use a powerboat with a suitably
tall outrigger.

If JAX truly believes what he says, he should jump on this opportunity
to make a fast $1000, get at least 11 days paid for in FL and get to
go sailing for free.

This offer is only good till Sept 10 because then storms start to
taper off in intensity. He must agree to hold me and the boat owner
blameless for any harm that befalls him due to lightning.

So JAX, put up or shut up.

On 8 Jul 2004 11:10:43 -0700, (Parallax) wrote:
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.
===================================

Here are a few more observation points to ponder:

Back in the late 80s or early 90s, there was a major sailboat race
around Long Island that got hit by a severe thunderstorm. Out of
about 200 boats that were entered, three were hit, and one of the
three was hit twice. Empirically that equates to a 2% chance.

Here's another statistic published today by the Lee County weather
service in SW Florida: A typical thunderstorm here will have about
500 cloud-to-ground strikes. A major storm (like the one we had
yesterday) will have about 3500 CTG strikes. If you assume that a
major storm takes in a 10 x 10 mile area, that is a 100 sq miles, and
with 35 strikes per sq mile. Let's assume that the odds of a solitary
mast being hit are 50% within 100 yards of a strike. There are about
310 100 yard squares in a sq mile and the odds of any one square
taking a hit are 35/310 or about 11% in a major storm, between 1 and 2
percent in an ordinary storm. Going with 50% odds, your chances of a
direct hit would be 5% in a big storm and less than 1% otherwise.

Here's another data point. In 35 or 40 years of boating, much of it
under sail, I've been through about 10 really major thunder storms,
maybe 50 of the ordinary sort, and have been hit once. No damage to
people or boat but we lost all of the electronics onboard except for
my hand held GPS. We don't even know for sure if it was a direct hit
but it was WAY too close for comfort and we were 300 miles off shore.

Wayne.B wrote in message . ..
On 8 Jul 2004 11:10:43 -0700, (Parallax) wrote:
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.
===================================

Here are a few more observation points to ponder:

Back in the late 80s or early 90s, there was a major sailboat race
around Long Island that got hit by a severe thunderstorm. Out of
about 200 boats that were entered, three were hit, and one of the
three was hit twice. Empirically that equates to a 2% chance.

A small dataset but close enough to what I calculated.

Here's another statistic published today by the Lee County weather
service in SW Florida: A typical thunderstorm here will have about
500 cloud-to-ground strikes. A major storm (like the one we had
yesterday) will have about 3500 CTG strikes. If you assume that a
major storm takes in a 10 x 10 mile area, that is a 100 sq miles, and
with 35 strikes per sq mile. Let's assume that the odds of a solitary
mast being hit are 50% within 100 yards of a strike. There are about
310 100 yard squares in a sq mile and the odds of any one square
taking a hit are 35/310 or about 11% in a major storm, between 1 and 2
percent in an ordinary storm. Going with 50% odds, your chances of a
direct hit would be 5% in a big storm and less than 1% otherwise.

Once again, close to what I calculated (5%).

Here's another data point. In 35 or 40 years of boating, much of it
under sail, I've been through about 10 really major thunder storms,
maybe 50 of the ordinary sort, and have been hit once. No damage to
people or boat but we lost all of the electronics onboard except for
my hand held GPS. We don't even know for sure if it was a direct hit
but it was WAY too close for comfort and we were 300 miles off shore.