[TowerTalk] Lightning Hitting Chimney
Thomas Giella
kn4lf@webtv.net
Tue, 17 Aug 1999 17:38:44 -0400 (EDT)
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My formal education is in meteorology with 25 years of weather
forecasting experience and 33 years of studying lightning and
thunderstorms here in Florida and currently own Lightning Fast Weather
Services.
First of all just like it is a fallacy that lightning never strikes the
same place twice, it is also fallacy that lightning always strikes the
highest object.
Normally the earth's surface has a negative charge but when a
thunderstorm is overhead the polarity changes to positive.
All ungrounded objects whether metallic or non metallic can build up an
excess charge during an overhead thunderstorm. Eventually this charge
sends a near invisible leader charge skyward, meeting the downward
moving leader charge, they meet and BANG a return lightning stroke
skyward.
A higher metallic object if properly grounded and topped off with
porcupines, which are a type of lightning rod, will drain off the excess
electric charge buildup, no leader will develop and no lightning strike
will occur. On the other hand, old fashioned lightning rods actually
attract lightning but if properly grounded will harmlessly carry the
charge to ground.
The above lightning rod information has been gleaned from NASA and The
University Of Florida Lightning Research Center.
In July 1997, Lightning ignored my 50 foot grounded tower with porcupine
installed and opted for my homebrew lightning detection system mounted
on a 20 foot high PVC pipe support mast, destroying it!!!
On July 4, 1999 I was injured by lightning as it struck an 8 foot high
chain link fence which was ungrounded. Lightning hit the fence directly,
approximately 20 yards away from where I was walking, of which I was
approximately 3 feet from. The lightning bypassed numerous 30 foot
grounded steel light poles.
And by the way lightning struck the 64 foot vertical section of my 1/2
wave inverted L two days ago but bypassed the 75 foot pine tree the the
antenna is attached to. The vertical section is approximately 4 feet
from the tree trunk. Fortunately my grounding system took the charge to
ground without any equpment damage and saved the tree. 73, Thom KN4LF.
http://members.tripod.com/~kn4lf/index.html
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Message-ID: <000d01bee8ee$ea637680$2aab82d1@GregGobleman>
From: "Greg Gobleman" <k9zm@frontiernet.net>
To: <towertalk@contesting.com>
Subject: [TowerTalk] Lightning Hitting Chimney
Date: Tue, 17 Aug 1999 15:27:16 -0500
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I just had the most amazing conversation with my contractor. I had called
him to check a roof leak next to a chimney in our bedroom. He had put the
roof on last year and we had just had a series of storms with 6" rain and
high winds overnight a few days ago. He could find nothing wrong with the
flashing, the chimney however has a bunch of bricks which appear to have
blown out in pieces and a new big crack that you could stick a pencil in.
The contractor says it was hit by lighting and the heavy rain and high wind
forced it in the crack to run out lower in the chimney, finally ending up on
our bedroom ceiling.
Now I'm no dummy, and I know that lighting will do what it wants to do. But
I looked at him, then the chimney, then at my 60' Rohn 25G tower 40 feet
away, with a 6el Telrex tri-bander, rotatable dipole for 40m and a 2meter
vertical on top, for about 75' in total height. Then I looked at the
nearest anchor point about 8' away with 2 steel guys going to the tower.
Further noting in my own mind that I had found no damage to anything related
to the radio or any electronic device in our home, and asked, " Don't you
think it would have hit the tower first or instead of the chimney." He said
"Maybe it's grounded better."
I can't wait for the insurance adjuster to see this. Has anybody ever
experienced anything like this? Just curious.
73
Greg K9ZM
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