Gary Schafer wrote:

Well for a start, I would not stand next to a copper flag pole or a
tree in a thunder storm. Side arcs can come just as easily from one as
the other.

Nor would I. My fault for not putting in a smiley face. But it is true that it
would be safer to be nearer a grounded pole than a tree, owing to the reduced
"surface effect" of the better conductor. That is to say: If one were somehow
standing half way between a copper flagpole and a tree, it would be advisable to
edge nearer the flag pole. That does not mean one should lean on it, though.
There will be surface effect around even the best conductor.

Lightning strikes can not be prevented. You can not "make anything
disappear from the competition for lightning".

Agree - not 'disappear', but unquestionably a proper air terminal and its corona
discharge will reduce build-up of positive charge. If there is something in the
area which is not so good at getting rid of charge, it will more likely be hit.
See below:

There is no such thing as bleeding of the charge. The earth can supply
charge much faster than it is possible to bleed it off.

"SUBSTANTIATION: In the years since Franklin Invented the sharp lightning rod,
many physicists have shown that, under strong electric fields, the air around
sharp rods becomes Ionized, creating space charges that act to weaken the
fields. It has also been discovered that the strengths of the strong fields
around the tips or sharp rods decrease so rapidly with distance that they become
weaker than the fields over blunter rods at distances greater than about 1/4 in.
.... From laboratory and field experiments, we have established that the critical
field strengths for lightning Interception develop sooner around blunt lightning
rods than around sharp ones around which the field strengths are limited by
their charge emissions. In effect. sharp rods tend to protect themselves, by
their charge emissions, against participating in lightning strikes."
Charles B. Moore, Langmuir Laboratory, New Mexico Tech
------------------

A blunt air terminal is preferred over a sharp pointed one. A sharp
point will encourage streamers to form sooner. They can actually
attract a strike. This includes the toilet brushes mounted on the
mast.

Here is a quote from a study by scientists who were *trying* to attract
lightning strikes:
------------
In strike-reception competitions over the past six years between sharp
Franklin rods, sharp-tipped "ESE" air terminals, and blunt rods with
hemispherical tips, all mounted on 6-mater high masts and separated
horizontally by about 6 meters, none of the sharp-tipped air terminals has
been "struck" by lightning but 12 of the blunt rods have taken strikes.
-------------------------
SUMMARY (Dinner is on the table):

You seem to have quite a bit of insight into lightning, but your message jumps
around a bit, and this is all I have time for. My purpose was not a detailed
rebuttal but to demonstrate that your original cryptic remark "...advice is
bogus" was not in the best spirit or interst of reasoned dialog, nor was it
true. From your follow-up message it appears you are more ready to bring more
light than heat. Good. Grownups can disagree and discuss those points of
contention without resorting to name-calling and invective.

I have one of those whisker brushes mounted on the top of my mast and
I have an oversized DynaPlate on my hull with heavy wire leading to
it. I've never been struck or had any lightning damage though my boat
has spent a lot of time in Florida and is in Florida as I write..
I've always believed that if my bvoat should be struck k lighting
would travel to the Dyna Plate and blow a hole of about the same size
right through my hull.

I regard those whisker brushes on my mast as snake oil. I just keep
my fingers crossed and hope that God doesn't get ****ed off at me. I
remember researching this subject 10 years ago when I was
commissioning my boat and I sort of remember concluding at the time
that no one (I repeat--no one) has an answer though there is no
shortage of people who pretend to have the answer. They are usually
recognizable because they speak in scientific (pseudo?) jargon and
sound quite impressive.

Hell, maybe the whiskers are working after all. Maybe the DynaPlate
has disappated (sp) several strikes that I'm not even aware of. I
guess in the end I would have to say that one can ever be too
cautious--or can one? Anxiety over an event seems to create a
peculiar magnetism that attracts that event. Ever tried not thinking
about it?

Joe

On 27 Jan 2004 08:02:49 -0800, (Parallax)
wrote:

We often see some discussions about lightning protection but here in
FL, it is really a major problem, especially for myself since I seem
to have a peculiar affinity for it.

I have seen it do the following:

While sitting on the toilet, it jumped from the faucet to drain
melting the fixture (literally scared the crap outa me)

After a thunderstorm while riding my bicycle, it struck the road in
front of me leaving a dry spot 30' in diameter.

Struck my phone lines and melted my telephone.

After a storm, ball lightning appeared about 30' up, slowly moved
along the shore while I tried to figure what to do. It hit a nearby
pine tree which exploded showering me with debris.

In deep woods during a storm, I sat under a picnic shelter on top of a
dry picnic table on top of dry concrete. It jumped out of a nearby
conduit and to the DRY concrete floor in front of me.


I sometimes think God is ****ed at me for some reason but can't figger
out why. This has affected my career (graduate work was "Free
Electron Charging of Fine Aerosol Particles) and made me VERY paranoid
about sailing during thunderstorms. My normal lightning protection
method is to try to get it to ground as quickly as possible. I have a
2'X2' copper sheet with a very large tinned copper braid soldered and
crimped to it that I drop overboard. The otehr end of the braid has
two welding clips that I attach to the upper and lower shrouds near
the deck. I turn off and unplug all electronics and stay away from
all metal fittings. I have even considered a retractable Faraday cage
attached to the mast head consisting of small wires to protect the
boat inside it. Am I too paranoid?

However, I am curious about lightning protection for less afflicted
ppl. I have seen these ground plates consisting of sintered bronze
powder that are fairly small but have high surface area due to the
many sintered particles (Dyna-Plate). I can believe these may work
for low E fields and low current but I do not believe they work for
high fields and high currents (like lightning). I think the small
passages act like tiny Faraday cups allowing no field inside and the
effective surface area is not much larger than the external area.
What do others think?

I have one of those whisker brushes mounted on the top of my mast and
I have an oversized DynaPlate on my hull with heavy wire leading to
it. I've never been struck or had any lightning damage though my boat
has spent a lot of time in Florida and is in Florida as I write..
I've always believed that if my bvoat should be struck k lighting
would travel to the Dyna Plate and blow a hole of about the same size
right through my hull.

I regard those whisker brushes on my mast as snake oil. I just keep
my fingers crossed and hope that God doesn't get ****ed off at me. I
remember researching this subject 10 years ago when I was
commissioning my boat and I sort of remember concluding at the time
that no one (I repeat--no one) has an answer though there is no
shortage of people who pretend to have the answer. They are usually
recognizable because they speak in scientific (pseudo?) jargon and
sound quite impressive.

Hell, maybe the whiskers are working after all. Maybe the DynaPlate
has disappated (sp) several strikes that I'm not even aware of. I
guess in the end I would have to say that one can ever be too
cautious--or can one? Anxiety over an event seems to create a
peculiar magnetism that attracts that event. Ever tried not thinking
about it?

Joe

On 27 Jan 2004 08:02:49 -0800, (Parallax)
wrote:

We often see some discussions about lightning protection but here in
FL, it is really a major problem, especially for myself since I seem
to have a peculiar affinity for it.

I have seen it do the following:

While sitting on the toilet, it jumped from the faucet to drain
melting the fixture (literally scared the crap outa me)

After a thunderstorm while riding my bicycle, it struck the road in
front of me leaving a dry spot 30' in diameter.

Struck my phone lines and melted my telephone.

After a storm, ball lightning appeared about 30' up, slowly moved
along the shore while I tried to figure what to do. It hit a nearby
pine tree which exploded showering me with debris.

In deep woods during a storm, I sat under a picnic shelter on top of a
dry picnic table on top of dry concrete. It jumped out of a nearby
conduit and to the DRY concrete floor in front of me.


I sometimes think God is ****ed at me for some reason but can't figger
out why. This has affected my career (graduate work was "Free
Electron Charging of Fine Aerosol Particles) and made me VERY paranoid
about sailing during thunderstorms. My normal lightning protection
method is to try to get it to ground as quickly as possible. I have a
2'X2' copper sheet with a very large tinned copper braid soldered and
crimped to it that I drop overboard. The otehr end of the braid has
two welding clips that I attach to the upper and lower shrouds near
the deck. I turn off and unplug all electronics and stay away from
all metal fittings. I have even considered a retractable Faraday cage
attached to the mast head consisting of small wires to protect the
boat inside it. Am I too paranoid?

However, I am curious about lightning protection for less afflicted
ppl. I have seen these ground plates consisting of sintered bronze
powder that are fairly small but have high surface area due to the
many sintered particles (Dyna-Plate). I can believe these may work
for low E fields and low current but I do not believe they work for
high fields and high currents (like lightning). I think the small
passages act like tiny Faraday cups allowing no field inside and the
effective surface area is not much larger than the external area.
What do others think?

toilet brushes at the top of a mast are a classic example in physics as how to
*increase* the chances of a static electricity discharge. The reason you see
all that psuedo-scientific jargon on the subject is that people are trying to
sell you something to make your fears of dying a crispy critter death go away.

I have one of those whisker brushes mounted on the top of my mast and
I have an oversized DynaPlate on my hull with heavy wire leading to
it. I've never been struck or had any lightning damage though my boat
has spent a lot of time in Florida and is in Florida as I write..
I've always believed that if my bvoat should be struck k lighting
would travel to the Dyna Plate and blow a hole of about the same size
right through my hull.

I regard those whisker brushes on my mast as snake oil. I just keep
my fingers crossed and hope that God doesn't get ****ed off at me. I
remember researching this subject 10 years ago when I was
commissioning my boat and I sort of remember concluding at the time
that no one (I repeat--no one) has an answer though there is no
shortage of people who pretend to have the answer. They are usually
recognizable because they speak in scientific (pseudo?) jargon and
sound quite impressive.

Hell, maybe the whiskers are working after all. Maybe the DynaPlate
has disappated (sp) several strikes that I'm not even aware of. I
guess in the end I would have to say that one can ever be too
cautious--or can one? Anxiety over an event seems to create a
peculiar magnetism that attracts that event. Ever tried not thinking
about it?

Joe

On 27 Jan 2004 08:02:49 -0800, (Parallax)
wrote:

We often see some discussions about lightning protection but here in
FL, it is really a major problem, especially for myself since I seem
to have a peculiar affinity for it.

I have seen it do the following:

While sitting on the toilet, it jumped from the faucet to drain
melting the fixture (literally scared the crap outa me)

After a thunderstorm while riding my bicycle, it struck the road in
front of me leaving a dry spot 30' in diameter.

Struck my phone lines and melted my telephone.

After a storm, ball lightning appeared about 30' up, slowly moved
along the shore while I tried to figure what to do. It hit a nearby
pine tree which exploded showering me with debris.

In deep woods during a storm, I sat under a picnic shelter on top of a
dry picnic table on top of dry concrete. It jumped out of a nearby
conduit and to the DRY concrete floor in front of me.


I sometimes think God is ****ed at me for some reason but can't figger
out why. This has affected my career (graduate work was "Free
Electron Charging of Fine Aerosol Particles) and made me VERY paranoid
about sailing during thunderstorms. My normal lightning protection
method is to try to get it to ground as quickly as possible. I have a
2'X2' copper sheet with a very large tinned copper braid soldered and
crimped to it that I drop overboard. The otehr end of the braid has
two welding clips that I attach to the upper and lower shrouds near
the deck. I turn off and unplug all electronics and stay away from
all metal fittings. I have even considered a retractable Faraday cage
attached to the mast head consisting of small wires to protect the
boat inside it. Am I too paranoid?

However, I am curious about lightning protection for less afflicted
ppl. I have seen these ground plates consisting of sintered bronze
powder that are fairly small but have high surface area due to the
many sintered particles (Dyna-Plate). I can believe these may work
for low E fields and low current but I do not believe they work for
high fields and high currents (like lightning). I think the small
passages act like tiny Faraday cups allowing no field inside and the
effective surface area is not much larger than the external area.
What do others think?

toilet brushes at the top of a mast are a classic example in physics as how to
*increase* the chances of a static electricity discharge. The reason you see
all that psuedo-scientific jargon on the subject is that people are trying to
sell you something to make your fears of dying a crispy critter death go away.

I have one of those whisker brushes mounted on the top of my mast and
I have an oversized DynaPlate on my hull with heavy wire leading to
it. I've never been struck or had any lightning damage though my boat
has spent a lot of time in Florida and is in Florida as I write..
I've always believed that if my bvoat should be struck k lighting
would travel to the Dyna Plate and blow a hole of about the same size
right through my hull.

I regard those whisker brushes on my mast as snake oil. I just keep
my fingers crossed and hope that God doesn't get ****ed off at me. I
remember researching this subject 10 years ago when I was
commissioning my boat and I sort of remember concluding at the time
that no one (I repeat--no one) has an answer though there is no
shortage of people who pretend to have the answer. They are usually
recognizable because they speak in scientific (pseudo?) jargon and
sound quite impressive.

Hell, maybe the whiskers are working after all. Maybe the DynaPlate
has disappated (sp) several strikes that I'm not even aware of. I
guess in the end I would have to say that one can ever be too
cautious--or can one? Anxiety over an event seems to create a
peculiar magnetism that attracts that event. Ever tried not thinking
about it?

Joe

On 27 Jan 2004 08:02:49 -0800, (Parallax)
wrote:

We often see some discussions about lightning protection but here in
FL, it is really a major problem, especially for myself since I seem
to have a peculiar affinity for it.

I have seen it do the following:

While sitting on the toilet, it jumped from the faucet to drain
melting the fixture (literally scared the crap outa me)

After a thunderstorm while riding my bicycle, it struck the road in
front of me leaving a dry spot 30' in diameter.

Struck my phone lines and melted my telephone.

After a storm, ball lightning appeared about 30' up, slowly moved
along the shore while I tried to figure what to do. It hit a nearby
pine tree which exploded showering me with debris.

In deep woods during a storm, I sat under a picnic shelter on top of a
dry picnic table on top of dry concrete. It jumped out of a nearby
conduit and to the DRY concrete floor in front of me.


I sometimes think God is ****ed at me for some reason but can't figger
out why. This has affected my career (graduate work was "Free
Electron Charging of Fine Aerosol Particles) and made me VERY paranoid
about sailing during thunderstorms. My normal lightning protection
method is to try to get it to ground as quickly as possible. I have a
2'X2' copper sheet with a very large tinned copper braid soldered and
crimped to it that I drop overboard. The otehr end of the braid has
two welding clips that I attach to the upper and lower shrouds near
the deck. I turn off and unplug all electronics and stay away from
all metal fittings. I have even considered a retractable Faraday cage
attached to the mast head consisting of small wires to protect the
boat inside it. Am I too paranoid?

However, I am curious about lightning protection for less afflicted
ppl. I have seen these ground plates consisting of sintered bronze
powder that are fairly small but have high surface area due to the
many sintered particles (Dyna-Plate). I can believe these may work
for low E fields and low current but I do not believe they work for
high fields and high currents (like lightning). I think the small
passages act like tiny Faraday cups allowing no field inside and the
effective surface area is not much larger than the external area.
What do others think?

nospam wrote in message . ..
I have one of those whisker brushes mounted on the top of my mast and
I have an oversized DynaPlate on my hull with heavy wire leading to
it. I've never been struck or had any lightning damage though my boat
has spent a lot of time in Florida and is in Florida as I write..
I've always believed that if my bvoat should be struck k lighting
would travel to the Dyna Plate and blow a hole of about the same size
right through my hull.

I regard those whisker brushes on my mast as snake oil. I just keep
my fingers crossed and hope that God doesn't get ****ed off at me. I
remember researching this subject 10 years ago when I was
commissioning my boat and I sort of remember concluding at the time
that no one (I repeat--no one) has an answer though there is no
shortage of people who pretend to have the answer. They are usually
recognizable because they speak in scientific (pseudo?) jargon and
sound quite impressive.

Hell, maybe the whiskers are working after all. Maybe the DynaPlate
has disappated (sp) several strikes that I'm not even aware of. I
guess in the end I would have to say that one can ever be too
cautious--or can one? Anxiety over an event seems to create a
peculiar magnetism that attracts that event. Ever tried not thinking
about it?

Joe

On 27 Jan 2004 08:02:49 -0800, (Parallax)
wrote:

We often see some discussions about lightning protection but here in
FL, it is really a major problem, especially for myself since I seem
to have a peculiar affinity for it.

I have seen it do the following:

While sitting on the toilet, it jumped from the faucet to drain
melting the fixture (literally scared the crap outa me)

After a thunderstorm while riding my bicycle, it struck the road in
front of me leaving a dry spot 30' in diameter.

Struck my phone lines and melted my telephone.

After a storm, ball lightning appeared about 30' up, slowly moved
along the shore while I tried to figure what to do. It hit a nearby
pine tree which exploded showering me with debris.

In deep woods during a storm, I sat under a picnic shelter on top of a
dry picnic table on top of dry concrete. It jumped out of a nearby
conduit and to the DRY concrete floor in front of me.


I sometimes think God is ****ed at me for some reason but can't figger
out why. This has affected my career (graduate work was "Free
Electron Charging of Fine Aerosol Particles) and made me VERY paranoid
about sailing during thunderstorms. My normal lightning protection
method is to try to get it to ground as quickly as possible. I have a
2'X2' copper sheet with a very large tinned copper braid soldered and
crimped to it that I drop overboard. The otehr end of the braid has
two welding clips that I attach to the upper and lower shrouds near
the deck. I turn off and unplug all electronics and stay away from
all metal fittings. I have even considered a retractable Faraday cage
attached to the mast head consisting of small wires to protect the
boat inside it. Am I too paranoid?

However, I am curious about lightning protection for less afflicted
ppl. I have seen these ground plates consisting of sintered bronze
powder that are fairly small but have high surface area due to the
many sintered particles (Dyna-Plate). I can believe these may work
for low E fields and low current but I do not believe they work for
high fields and high currents (like lightning). I think the small
passages act like tiny Faraday cups allowing no field inside and the
effective surface area is not much larger than the external area.
What do others think?


I've tried drinking but that interferes with my sailing. Thunder
storms are sorta hard to ignore here. I see them as a kind of natural
selection thing for yankee golfers.

nospam wrote in message . ..
I have one of those whisker brushes mounted on the top of my mast and
I have an oversized DynaPlate on my hull with heavy wire leading to
it. I've never been struck or had any lightning damage though my boat
has spent a lot of time in Florida and is in Florida as I write..
I've always believed that if my bvoat should be struck k lighting
would travel to the Dyna Plate and blow a hole of about the same size
right through my hull.

I regard those whisker brushes on my mast as snake oil. I just keep
my fingers crossed and hope that God doesn't get ****ed off at me. I
remember researching this subject 10 years ago when I was
commissioning my boat and I sort of remember concluding at the time
that no one (I repeat--no one) has an answer though there is no
shortage of people who pretend to have the answer. They are usually
recognizable because they speak in scientific (pseudo?) jargon and
sound quite impressive.

Hell, maybe the whiskers are working after all. Maybe the DynaPlate
has disappated (sp) several strikes that I'm not even aware of. I
guess in the end I would have to say that one can ever be too
cautious--or can one? Anxiety over an event seems to create a
peculiar magnetism that attracts that event. Ever tried not thinking
about it?

Joe

On 27 Jan 2004 08:02:49 -0800, (Parallax)
wrote:

We often see some discussions about lightning protection but here in
FL, it is really a major problem, especially for myself since I seem
to have a peculiar affinity for it.

I have seen it do the following:

While sitting on the toilet, it jumped from the faucet to drain
melting the fixture (literally scared the crap outa me)

After a thunderstorm while riding my bicycle, it struck the road in
front of me leaving a dry spot 30' in diameter.

Struck my phone lines and melted my telephone.

After a storm, ball lightning appeared about 30' up, slowly moved
along the shore while I tried to figure what to do. It hit a nearby
pine tree which exploded showering me with debris.

In deep woods during a storm, I sat under a picnic shelter on top of a
dry picnic table on top of dry concrete. It jumped out of a nearby
conduit and to the DRY concrete floor in front of me.


I sometimes think God is ****ed at me for some reason but can't figger
out why. This has affected my career (graduate work was "Free
Electron Charging of Fine Aerosol Particles) and made me VERY paranoid
about sailing during thunderstorms. My normal lightning protection
method is to try to get it to ground as quickly as possible. I have a
2'X2' copper sheet with a very large tinned copper braid soldered and
crimped to it that I drop overboard. The otehr end of the braid has
two welding clips that I attach to the upper and lower shrouds near
the deck. I turn off and unplug all electronics and stay away from
all metal fittings. I have even considered a retractable Faraday cage
attached to the mast head consisting of small wires to protect the
boat inside it. Am I too paranoid?

However, I am curious about lightning protection for less afflicted
ppl. I have seen these ground plates consisting of sintered bronze
powder that are fairly small but have high surface area due to the
many sintered particles (Dyna-Plate). I can believe these may work
for low E fields and low current but I do not believe they work for
high fields and high currents (like lightning). I think the small
passages act like tiny Faraday cups allowing no field inside and the
effective surface area is not much larger than the external area.
What do others think?


I've tried drinking but that interferes with my sailing. Thunder
storms are sorta hard to ignore here. I see them as a kind of natural
selection thing for yankee golfers.

On Wed, 28 Jan 2004 00:07:58 GMT, Chuck Bollinger wrote:

Parallax wrote:

In deep woods during a storm, I sat under a picnic shelter on top of a
dry picnic table on top of dry concrete. It jumped out of a nearby
conduit and to the DRY concrete floor in front of me.

Don't do that again - seriously. Here's the thing: Whether lightning strikes
something isn't related to the item's conductivity but to the amount of charge
it has built up. The arc will go between the highest charge in the cloud/air
and the highest opposite charge on the land. Wet or dry doesn't matter much.
You know this from rubbing a dry glass rod in dry wool or your dry feet across a
dry rug. It's worse the drier things are.

After the strike happens it is no longer a matter of charge, but power. The
amount of damage will depend upon whether there is a good path to earth. That's
where conductivity comes in. If there is no path the amount of 'surface effect'
increases, endangering people and things in the area.

Therefore it would be safer to stand next to a heavy copper flagpole embedded in
the earth than under a tree or in a 'dry' picnic shelter. Me, I'll stay here in
the Pacific NW and take my chances with tsunamis.

method is to try to get it to ground as quickly as possible. I have a
2'X2' copper sheet with a very large tinned copper braid soldered and
crimped to it that I drop overboard. The otehr end of the braid has
two welding clips that I attach to the upper and lower shrouds near
the deck. I turn off and unplug all electronics and stay away from
all metal fittings. I have even considered a retractable Faraday cage
attached to the mast head consisting of small wires to protect the
boat inside it. Am I too paranoid?

Dissipitation is by edge effect, IE 1 square foot of copper shaped into a long
strip is far more effective than a square. All connections should be
mechanically fastened as the heat of conducting the strike can melt solder. The
water in the gaps in a Dynaplate in event of a strike has been reported to turn
to steam thus blowing it apart.

Ground your mast, shrouds, and stays with heavy copper cable like tinned battery
cables to an EXTERNAL metal keel (best) or bronze/copper ground plate with only
gentle bends not to exceed a 6" radius. The straighter the better to prevent
side flashes. There are fittings (called air terminals) for the mast, and
special clamps (for the cable connections) designed for lightning grounds with
recommendations by universities out on the web. The brush devices have not been
proven to reduce the chances of a strike, seems the earth carries a LOT of
charge, and any dissipitated by one of these devices is instantly replenished by
the earth. They do have the effect of reducing the boaters bank account as the
are priced far out of proportion to how they are made.

JJ



No, careful and sensible. The only quarrel I'd have is with braided conductor
to your plate rather than a copper band. Harder to handle, but better capable
of handling the juice. As you live in Florida you might consider having your
plate attached to the hull - tightly with no intervening water - and permanent
connection to your shrouds. The 'air terminal' can be anything - a pointy rod,
those little brush things... etc. I am not familiar with a Faraday cage, but it
sounds knobby. For your purpose you want something sharp, which should have the
effect of allowing static charge to bleed harmlessly off. Then you want a heavy
bonding strap running the length of the boat. Anything important is bonded to
it, at right angles preferably, and the bonding strap is attached to the
underwater ground plate as well.

Essentially with this bypass ground, you are making your boat disappear from the
competition for the lightning.

If lightning does strike then your installation can carry off the charge, but
the whole idea is to avoid static buildup.

However, I am curious about lightning protection for less afflicted
ppl. I have seen these ground plates consisting of sintered bronze
powder that are fairly small but have high surface area due to the
many sintered particles (Dyna-Plate). I can believe these may work
for low E fields and low current but I do not believe they work for
high fields and high currents (like lightning). I think the small
passages act like tiny Faraday cups allowing no field inside and the
effective surface area is not much larger than the external area.
What do others think?

Well, the minimum grounding plate is 1 foot square. Dyna Plates seem to be used
to ground single sideband transmitters. Stick with a copper plate. Two square
feet is overkill but does no harm and perhaps adds a comfort level.

Check into your local Power Squadron. Their educational offerings include
Marine Electronics which covers this subject, including the 'zone of protection'.

http://www.usps.org




James Johnson
remove the "dot" from after sail in email address to reply

On Wed, 28 Jan 2004 00:07:58 GMT, Chuck Bollinger wrote:

Parallax wrote:

In deep woods during a storm, I sat under a picnic shelter on top of a
dry picnic table on top of dry concrete. It jumped out of a nearby
conduit and to the DRY concrete floor in front of me.

Don't do that again - seriously. Here's the thing: Whether lightning strikes
something isn't related to the item's conductivity but to the amount of charge
it has built up. The arc will go between the highest charge in the cloud/air
and the highest opposite charge on the land. Wet or dry doesn't matter much.
You know this from rubbing a dry glass rod in dry wool or your dry feet across a
dry rug. It's worse the drier things are.

After the strike happens it is no longer a matter of charge, but power. The
amount of damage will depend upon whether there is a good path to earth. That's
where conductivity comes in. If there is no path the amount of 'surface effect'
increases, endangering people and things in the area.

Therefore it would be safer to stand next to a heavy copper flagpole embedded in
the earth than under a tree or in a 'dry' picnic shelter. Me, I'll stay here in
the Pacific NW and take my chances with tsunamis.

method is to try to get it to ground as quickly as possible. I have a
2'X2' copper sheet with a very large tinned copper braid soldered and
crimped to it that I drop overboard. The otehr end of the braid has
two welding clips that I attach to the upper and lower shrouds near
the deck. I turn off and unplug all electronics and stay away from
all metal fittings. I have even considered a retractable Faraday cage
attached to the mast head consisting of small wires to protect the
boat inside it. Am I too paranoid?

Dissipitation is by edge effect, IE 1 square foot of copper shaped into a long
strip is far more effective than a square. All connections should be
mechanically fastened as the heat of conducting the strike can melt solder. The
water in the gaps in a Dynaplate in event of a strike has been reported to turn
to steam thus blowing it apart.

Ground your mast, shrouds, and stays with heavy copper cable like tinned battery
cables to an EXTERNAL metal keel (best) or bronze/copper ground plate with only
gentle bends not to exceed a 6" radius. The straighter the better to prevent
side flashes. There are fittings (called air terminals) for the mast, and
special clamps (for the cable connections) designed for lightning grounds with
recommendations by universities out on the web. The brush devices have not been
proven to reduce the chances of a strike, seems the earth carries a LOT of
charge, and any dissipitated by one of these devices is instantly replenished by
the earth. They do have the effect of reducing the boaters bank account as the
are priced far out of proportion to how they are made.

JJ



No, careful and sensible. The only quarrel I'd have is with braided conductor
to your plate rather than a copper band. Harder to handle, but better capable
of handling the juice. As you live in Florida you might consider having your
plate attached to the hull - tightly with no intervening water - and permanent
connection to your shrouds. The 'air terminal' can be anything - a pointy rod,
those little brush things... etc. I am not familiar with a Faraday cage, but it
sounds knobby. For your purpose you want something sharp, which should have the
effect of allowing static charge to bleed harmlessly off. Then you want a heavy
bonding strap running the length of the boat. Anything important is bonded to
it, at right angles preferably, and the bonding strap is attached to the
underwater ground plate as well.

Essentially with this bypass ground, you are making your boat disappear from the
competition for the lightning.

If lightning does strike then your installation can carry off the charge, but
the whole idea is to avoid static buildup.

However, I am curious about lightning protection for less afflicted
ppl. I have seen these ground plates consisting of sintered bronze
powder that are fairly small but have high surface area due to the
many sintered particles (Dyna-Plate). I can believe these may work
for low E fields and low current but I do not believe they work for
high fields and high currents (like lightning). I think the small
passages act like tiny Faraday cups allowing no field inside and the
effective surface area is not much larger than the external area.
What do others think?

Well, the minimum grounding plate is 1 foot square. Dyna Plates seem to be used
to ground single sideband transmitters. Stick with a copper plate. Two square
feet is overkill but does no harm and perhaps adds a comfort level.

Check into your local Power Squadron. Their educational offerings include
Marine Electronics which covers this subject, including the 'zone of protection'.

http://www.usps.org




James Johnson
remove the "dot" from after sail in email address to reply

On Thu, 05 Feb 2004 00:52:00 GMT, James Johnson
wrote:
//

Ground your mast, shrouds, and stays with heavy copper cable like tinned battery
cables to an EXTERNAL metal keel (best) or bronze/copper ground plate with only
gentle bends not to exceed a 6" radius. ///
JJ

I know what James meant and you know what James meant, which was:
"Ground ...with heavy copper cable with only
gentle bends exceeding a 6" radius"