On Sun, 13 Jun 2004 02:26:00 -0000, Larry W4CSC
wrote:

"Jack Painter" wrote in
news:16syc.157$Jk5.41@lakeread02:

outer docks. In the aftermath, we heard there was a lot more damage
from collisions than from lightning, and that is amazing considering
how many yachts I saw get struck that night.

I've read the webpage from FL. Very interesting research. The mast looks
tall when you're standing at the bottom of it looking up, but in the
overall height of a thunderstorm FIVE MILES HIGH, our masts are like a
dimple on the dining room table, and not much of a "target".

I was at the transmitter shack of WRJA-TV, the PBS station in Sumter, SC,
visiting an old friend who was chief engineer, Bill Jones, one night. We
were building the first weather radio repeater after Bill had applied for,
and gotten, an FCC license for that band to simply repeat the signal from
Columbia, SC's weather station to the local Sumter area which had trouble
hearing it. We made it out of kit ham radio repeater boards from VHF
Engineering in Binghamton, NY, as we had a local repeater.

A huge thunderstorm cell moved across Sumter and actually went THROUGH the
1800' WRJA-TV tower while we watched out the back door as lightning went
SIDEWAYS 10 miles in the cloud just to hit that big 1800' ground rod
sticking up out of the table-flat terrain of eastern Sumter County. I'm
standing there watching the light show and suddenly Bill taps me on the
shoulder and hands me a big yellow rain coat, saying, "Come on. I wanna
show you something neat." We followed the huge hardline coaxial cables
from the 35KW TV transmitter out to the base of the antenna and Bill says,
"You're standing in the safest place in Sumter County. There is a cone of
protection against being hit by lightning provided by my tower and you're
now standing in the middle of it. Hang onto the tower leg and feel the
current going through it." I burned my hand a couple of times as the huge
BOOMs went off over my head a thousand feet up. The huge bridge cables
JUMPED from the surge of electrical EMP hit them, many times. The lights
went out and we had to go back in the building to reset the transmitters
when the power came back on.

Though the "tower" on the sailboat is very short, in comparison, I like to
think that if you have a proper grounding system, like the professor
describes on his webpages, you are also in a tiny cone where the blast will
mostly be shunted AROUND you, which is why your car is so safe in a
thunderstorm. The current surge that kills goes AROUND the the steel body
of the car....Steel ships and boats do that....Plastic, not so good.

Larry


Larry, I really don't believe you are that dumb to hold on to a tower
in the middle of a lightning storm. I do see that you are a great
story teller though. However please remember that there are a lot of
folks that read this group that may not be too technically savvy and
may not be able to tell the difference.

Regards
Gary

Gary Schafer wrote in
:


Larry, I really don't believe you are that dumb to hold on to a tower
in the middle of a lightning storm. I do see that you are a great
story teller though. However please remember that there are a lot of
folks that read this group that may not be too technically savvy and
may not be able to tell the difference.

Regards
Gary


Not dumb at all. Under my feet were 36 pile-driven ground rods connected
with bridge cables to the tower in a ring about 100' in diameter, "driven
to refusal", in other words, bed rock.

The several megohms of body resistance is no path at all when in parallel
with a few MICROOHMS to such a ground system. With currents high enough to
heat the tower beyond what my hand could tolerate, there is no shock, at
all.

It was a most amazing afternoon.....(c;

Larry

On Sun, 13 Jun 2004 13:57:17 -0000, Larry W4CSC
wrote:

Gary Schafer wrote in
:


Larry, I really don't believe you are that dumb to hold on to a tower
in the middle of a lightning storm. I do see that you are a great
story teller though. However please remember that there are a lot of
folks that read this group that may not be too technically savvy and
may not be able to tell the difference.

Regards
Gary


Not dumb at all. Under my feet were 36 pile-driven ground rods connected
with bridge cables to the tower in a ring about 100' in diameter, "driven
to refusal", in other words, bed rock.

The several megohms of body resistance is no path at all when in parallel
with a few MICROOHMS to such a ground system. With currents high enough to
heat the tower beyond what my hand could tolerate, there is no shock, at
all.

It was a most amazing afternoon.....(c;

Larry


With the high current traveling through the tower and the relatively
high impedance that the tower and ground leads present, it is possible
to have thousands of volts differential in only a few feet length. The
larger the tower the less impedance of course. But the ground system
is never 100% and it has it's own impedance problems.

All conductors have impedance and a high current applied to that
impedance will produce a large voltage drop across it. Even the tower
itself.

Ground rods driven past 8 to 10 feet do little good for lightning.
Even if they are into the water table past that depth. The impedance
of that long of a rod gets to high to be of much value. (I know, lots
of people have long deep rods or pipes in their installations and
think they have the best ground in the world)

If you really want to know why go look at the polyphaser site. They
even tell you how to calculate what the voltage drop in a few feet of
tower length will be with a typical lightning strike.

You are right about the tower providing a "cone of protection" but
that cone only means that the lightning will probably strike the tower
before it strikes you directly. It does not tell you anything about
how effective the tower / ground system is at getting the lightning
current dissipated safely to ground.

Don't be grabbing on to those towers during a storm Larry. We will
miss you here.

Regards
Gary

"Larry W4CSC" wrote

"Jack Painter" wrote

outer docks. In the aftermath, we heard there was a lot more damage
from collisions than from lightning, and that is amazing considering
how many yachts I saw get struck that night.

I've read the webpage from FL. Very interesting research. The mast looks
tall when you're standing at the bottom of it looking up, but in the
overall height of a thunderstorm FIVE MILES HIGH, our masts are like a
dimple on the dining room table, and not much of a "target".

"You're standing in the safest place in Sumter County. There is a cone of
protection against being hit by lightning provided by my tower and you're
now standing in the middle of it. Hang onto the tower leg and feel the
current going through it." I burned my hand a couple of times as the huge
BOOMs went off over my head a thousand feet up. The huge bridge cables
JUMPED from the surge of electrical EMP hit them, many times.

Though the "tower" on the sailboat is very short, in comparison, I like to
think that if you have a proper grounding system, like the professor
describes on his webpages, you are also in a tiny cone where the blast
will
mostly be shunted AROUND you, which is why your car is so safe in a
thunderstorm. The current surge that kills goes AROUND the the steel body
of the car....Steel ships and boats do that....Plastic, not so good.

Indeed. That Florida study explains that there are very few examples of
sailors (on sailboats) being hurt or killed by lightning. That is due to the
cone of protection as you said, but it does not normally extend to anyone
touching those shrouds or mast! To some extent you are bonded to the system
when standing on deck and could be in a very high voltage condition without
feeling much current due to the bonding. While HV lineman aloft use that
principle safely every day, boaters are advised to remain below deck and NOT
touch anything conductive during a lightning storm.

Similarly, while "under" the cone of protection of that high transmitter
mast, you were indeed safe. But on your way over to it and back from it, you
are both lucky you lived to tell the story. The voltage gradient between
your two feet on the walk nearby could be thousands of volts during a
discharge let alone a strike.

Best regards,

Jack

On Fri, 11 Jun 2004 20:27:40 -0400, "Jack Painter"
wrote:

I remember a night of terrible line squalls that wrecked several yachts in
Block Island Salt Harbor.

======================================

Would that have been in the summer of '74 by any chance? I was
halfway between Mystic, CT and BI that year when we got hit by the
mother of all line squalls just after dark.

"Wayne.B" wrote

On Fri, 11 Jun 2004 20:27:40 -0400, "Jack Painter"
wrote:

I remember a night of terrible line squalls that wrecked several yachts
in
Block Island Salt Harbor.

======================================

Would that have been in the summer of '74 by any chance? I was
halfway between Mystic, CT and BI that year when we got hit by the
mother of all line squalls just after dark.

It was the summer of '85. I lived in Mystic from '84 to '87 right at the
drawbridge, in what turned out to be the only building on the water that did
not burn from Gravel Street to the drawbridge, a few years back.

Best regards,

Jack

On Sun, 13 Jun 2004 22:01:32 -0400, "Jack Painter"
wrote:
It was the summer of '85. I lived in Mystic from '84 to '87 right at the
drawbridge, in what turned out to be the only building on the water that did
not burn from Gravel Street to the drawbridge, a few years back.

===========================================

I guess that's one storm I missed. Mystic is still a great little
town and docking overnight at the museum is one of my favorite stop
overs.