Thunderstorms every day and my fear of lightning (totally justified)
have caused me to once again scheme up a way to protect my sailboat.
For protection while anchored, I have a 2'X2' copper sheet with very
thick stranded tinned cable with a clamp for attachment to the mast.
I have considered using this while underway but it would cause too
much drag and would probably foul the prop.

So........another useless idea. How could you tow a lightning ground?
Such a ground doesnt have to be a sheet. it just has to have large
surface area. Could attach it to the bottom of the dinghy and tow it
with proper cable going to the mast but I try not to tow my dinghy.
OK, why not something like a boogie board (foam) covered with Cu foil.
No matter which side it had in the water, it would have lots of area
submerged. It would produce minimal drag. Any thoughts?

Don't waste your time. You do not "cable" lightning. It goes where it
wants. (I can refer you to long technical discussions as to why this is
true but having asked the question you will not understand them). If you
help it go where it wants it will cooperate. It first wants to go to your
mast because that is the closest thing. Give it a lightning rod above your
antenna to hit. It then wants to go to the water. Couple the mast straight
down to a conductive area on your hull. Big thick number 1 cable is good.
Best thing on the hull is a long relatively narrow conductor with lots of
sharp edge. maybe 8 or 10 feet by 2 inches. Copper ground strap will work.
Use other heavy conductors to connect any other big metal objects to it.
Then sweat no more.

Any attempt to guide lightning someplace else will almost certainly fail.
It jumps to other things and refuses to turn corners. It will never agree
to go to your dinghy or boogey board. It just does not like you enough to
be that cooperative. Such strategies by the way likely make lightning
damage worse. Gets it all over the boat instead of drilling straight to the
water.

Jim Donohue

"Parallax" wrote in message
om...
Thunderstorms every day and my fear of lightning (totally justified)
have caused me to once again scheme up a way to protect my sailboat.
For protection while anchored, I have a 2'X2' copper sheet with very
thick stranded tinned cable with a clamp for attachment to the mast.
I have considered using this while underway but it would cause too
much drag and would probably foul the prop.

So........another useless idea. How could you tow a lightning ground?
Such a ground doesnt have to be a sheet. it just has to have large
surface area. Could attach it to the bottom of the dinghy and tow it
with proper cable going to the mast but I try not to tow my dinghy.
OK, why not something like a boogie board (foam) covered with Cu foil.
No matter which side it had in the water, it would have lots of area
submerged. It would produce minimal drag. Any thoughts?

Surface area doesn't really matter for a lightning ground, edge length does.
The charge will dissipate along the edges, so a long piece of copper foil
would do much better, maybe 2" wide standard stuff. Like Jim said, nothing
is foolproof, but you can always help your friend the lightning bolt out to
find his way to a home in the water! Bigger is better for cable, try to keep
any turns to a 12" or so radius, and you can probably do better than no
protection at all.

I have a similar system... lightning rod to cable that goes overboard at the
dock to a copper plate with lots of cuts in it (for more edge area) that
sits on the bottom. I can't prove that it ever worked, but one time I pulled
it up and the plate was gone. The cable looked like it had been cut clean
off and was dark. I know it didn't pull out of the connector since there was
no exposed wire. Either it did it's job while I was gone, or somebody on my
dock needed a crappy looking piece of copper sheet!

--


Keith
__
"Tom."
-Tom Nissalke, New coach of the NBA's Houston Rockets, when
asked how he pronounced his name, 1966.
"Parallax" wrote in message
om...
Thunderstorms every day and my fear of lightning (totally justified)
have caused me to once again scheme up a way to protect my sailboat.
For protection while anchored, I have a 2'X2' copper sheet with very
thick stranded tinned cable with a clamp for attachment to the mast.
I have considered using this while underway but it would cause too
much drag and would probably foul the prop.

So........another useless idea. How could you tow a lightning ground?
Such a ground doesnt have to be a sheet. it just has to have large
surface area. Could attach it to the bottom of the dinghy and tow it
with proper cable going to the mast but I try not to tow my dinghy.
OK, why not something like a boogie board (foam) covered with Cu foil.
No matter which side it had in the water, it would have lots of area
submerged. It would produce minimal drag. Any thoughts?

Designing a Lightning protection scheme without a proper study
you are likely to attract all the sky sparks right to your boat, while
the other guy a 100 yards away will get nothing.
If you do it, do it the classic way: Thick rod, thick cable, very good
ground (into the sea) no turns, no tricks, no shortcuts, no revolutionary
ideas. Otherwise don't.
That's what an aerospace engineer told me.
Given in good faith and without guarantee!!!
Good luck




"Keith" wrote in message
...
Surface area doesn't really matter for a lightning ground, edge length
does.
The charge will dissipate along the edges, so a long piece of copper foil
would do much better, maybe 2" wide standard stuff. Like Jim said, nothing
is foolproof, but you can always help your friend the lightning bolt out
to
find his way to a home in the water! Bigger is better for cable, try to
keep
any turns to a 12" or so radius, and you can probably do better than no
protection at all.

I have a similar system... lightning rod to cable that goes overboard at
the
dock to a copper plate with lots of cuts in it (for more edge area) that
sits on the bottom. I can't prove that it ever worked, but one time I
pulled
it up and the plate was gone. The cable looked like it had been cut clean
off and was dark. I know it didn't pull out of the connector since there
was
no exposed wire. Either it did it's job while I was gone, or somebody on
my
dock needed a crappy looking piece of copper sheet!

--


Keith
__
"Tom."
-Tom Nissalke, New coach of the NBA's Houston Rockets, when
asked how he pronounced his name, 1966.
"Parallax" wrote in message
om...
Thunderstorms every day and my fear of lightning (totally justified)
have caused me to once again scheme up a way to protect my sailboat.
For protection while anchored, I have a 2'X2' copper sheet with very
thick stranded tinned cable with a clamp for attachment to the mast.
I have considered using this while underway but it would cause too
much drag and would probably foul the prop.

So........another useless idea. How could you tow a lightning ground?
Such a ground doesnt have to be a sheet. it just has to have large
surface area. Could attach it to the bottom of the dinghy and tow it
with proper cable going to the mast but I try not to tow my dinghy.
OK, why not something like a boogie board (foam) covered with Cu foil.
No matter which side it had in the water, it would have lots of area
submerged. It would produce minimal drag. Any thoughts?

"Jim Donohue" wrote in message news:VDqGc.52473$Yu.1882@fed1read04...
Don't waste your time. You do not "cable" lightning. It goes where it
wants. (I can refer you to long technical discussions as to why this is
true but having asked the question you will not understand them). If you
help it go where it wants it will cooperate. It first wants to go to your
mast because that is the closest thing. Give it a lightning rod above your
antenna to hit. It then wants to go to the water. Couple the mast straight
down to a conductive area on your hull. Big thick number 1 cable is good.
Best thing on the hull is a long relatively narrow conductor with lots of
sharp edge. maybe 8 or 10 feet by 2 inches. Copper ground strap will work.
Use other heavy conductors to connect any other big metal objects to it.
Then sweat no more.

Any attempt to guide lightning someplace else will almost certainly fail.
It jumps to other things and refuses to turn corners. It will never agree
to go to your dinghy or boogey board. It just does not like you enough to
be that cooperative. Such strategies by the way likely make lightning
damage worse. Gets it all over the boat instead of drilling straight to the
water.

Jim Donohue

"Parallax" wrote in message
om...
Thunderstorms every day and my fear of lightning (totally justified)
have caused me to once again scheme up a way to protect my sailboat.
For protection while anchored, I have a 2'X2' copper sheet with very
thick stranded tinned cable with a clamp for attachment to the mast.
I have considered using this while underway but it would cause too
much drag and would probably foul the prop.

So........another useless idea. How could you tow a lightning ground?
Such a ground doesnt have to be a sheet. it just has to have large
surface area. Could attach it to the bottom of the dinghy and tow it
with proper cable going to the mast but I try not to tow my dinghy.
OK, why not something like a boogie board (foam) covered with Cu foil.
No matter which side it had in the water, it would have lots of area
submerged. It would produce minimal drag. Any thoughts?

Jim:

I'll reluctantly admit to some knowledge of Very High Voltage and have
worked with very high current particle accelerators and nuke weapon
simulators so I do know something about how to get such current pulses
to go places. Keeping radii of curvature of conductors low is well
known as is the sharp edge thing on the ground. I sorta thought that
I would use many creases (oriented for low drag)in the copper foil for
edges and I currently use cable thicker than #1 with more surface
area.

How about connecting a 20 ft piece of #1 cable to the backstay and
dragging that around.


On Tue, 6 Jul 2004 06:07:38 -0500, "Keith"
wrote:

Surface area doesn't really matter for a lightning ground, edge length does.
The charge will dissipate along the edges, so a long piece of copper foil
would do much better, maybe 2" wide standard stuff. Like Jim said, nothing
is foolproof, but you can always help your friend the lightning bolt out to
find his way to a home in the water! Bigger is better for cable, try to keep
any turns to a 12" or so radius, and you can probably do better than no
protection at all.

I have a similar system... lightning rod to cable that goes overboard at the
dock to a copper plate with lots of cuts in it (for more edge area) that
sits on the bottom. I can't prove that it ever worked, but one time I pulled
it up and the plate was gone. The cable looked like it had been cut clean
off and was dark. I know it didn't pull out of the connector since there was
no exposed wire. Either it did it's job while I was gone, or somebody on my
dock needed a crappy looking piece of copper sheet!

In article ,
(Parallax) wrote:

Thunderstorms every day and my fear of lightning (totally justified)
have caused me to once again scheme up a way to protect my sailboat.
For protection while anchored, I have a 2'X2' copper sheet with very
thick stranded tinned cable with a clamp for attachment to the mast.
I have considered using this while underway but it would cause too
much drag and would probably foul the prop.

So........another useless idea. How could you tow a lightning ground?
Such a ground doesnt have to be a sheet. it just has to have large
surface area. Could attach it to the bottom of the dinghy and tow it
with proper cable going to the mast but I try not to tow my dinghy.
OK, why not something like a boogie board (foam) covered with Cu foil.
No matter which side it had in the water, it would have lots of area
submerged. It would produce minimal drag. Any thoughts?

From my experience, when lightning is near, I have other things to worry
about, like wind and waves. When threatened, I park it fast and get
below.

If I were back in western FL, I'd have a cable bulldog-clamped to each
stay, probably with a zinc attached to give them double duty. A cable
from the mast takes too sharp a turn for my taste.

--
Jere Lull
Xan-a-Deux ('73 Tanzer 28 #4 out of Tolchester, MD)
Xan's Pages: http://members.dca.net/jerelull/X-Main.html
Our BVI FAQs (290+ pics) http://homepage.mac.com/jerelull/BVI/

The problem of course is L as in L di/dt. di/dt is a real big number. So
any significant L and you got real big V. Real big V causes breakdown and
more paths with real big di/dt....and so on.

Straight and big minimizes L. Anything else you do compromises the result.
How safe you want to be?

I am not a fan of grounding via the shrouds. problem is the mast then goes
blasting up and arcs to the shrounds. All sorts of things can get destroyed
in that process. I want mast to water and no where else.

Jim

"Parallax" wrote in message
om...
"Jim Donohue" wrote in message
news:VDqGc.52473$Yu.1882@fed1read04...
Don't waste your time. You do not "cable" lightning. It goes where it
wants. (I can refer you to long technical discussions as to why this is
true but having asked the question you will not understand them). If
you
help it go where it wants it will cooperate. It first wants to go to
your
mast because that is the closest thing. Give it a lightning rod above
your
antenna to hit. It then wants to go to the water. Couple the mast
straight
down to a conductive area on your hull. Big thick number 1 cable is
good.
Best thing on the hull is a long relatively narrow conductor with lots
of
sharp edge. maybe 8 or 10 feet by 2 inches. Copper ground strap will
work.
Use other heavy conductors to connect any other big metal objects to it.
Then sweat no more.

Any attempt to guide lightning someplace else will almost certainly
fail.
It jumps to other things and refuses to turn corners. It will never
agree
to go to your dinghy or boogey board. It just does not like you enough
to
be that cooperative. Such strategies by the way likely make lightning
damage worse. Gets it all over the boat instead of drilling straight to
the
water.

Jim Donohue

"Parallax" wrote in message
om...
Thunderstorms every day and my fear of lightning (totally justified)
have caused me to once again scheme up a way to protect my sailboat.
For protection while anchored, I have a 2'X2' copper sheet with very
thick stranded tinned cable with a clamp for attachment to the mast.
I have considered using this while underway but it would cause too
much drag and would probably foul the prop.

So........another useless idea. How could you tow a lightning ground?
Such a ground doesnt have to be a sheet. it just has to have large
surface area. Could attach it to the bottom of the dinghy and tow it
with proper cable going to the mast but I try not to tow my dinghy.
OK, why not something like a boogie board (foam) covered with Cu foil.
No matter which side it had in the water, it would have lots of area
submerged. It would produce minimal drag. Any thoughts?

Jim:

I'll reluctantly admit to some knowledge of Very High Voltage and have
worked with very high current particle accelerators and nuke weapon
simulators so I do know something about how to get such current pulses
to go places. Keeping radii of curvature of conductors low is well
known as is the sharp edge thing on the ground. I sorta thought that
I would use many creases (oriented for low drag)in the copper foil for
edges and I currently use cable thicker than #1 with more surface
area.

What would be wrong with a long, ....straight.... piece of aluminum rod
in contact with a location as desired/convenient near the mast top,
(running alongside a shroud) into the water ?

Courtney




Parallax wrote:

Thunderstorms every day and my fear of lightning (totally justified)
have caused me to once again scheme up a way to protect my sailboat.
For protection while anchored, I have a 2'X2' copper sheet with very
thick stranded tinned cable with a clamp for attachment to the mast.
I have considered using this while underway but it would cause too
much drag and would probably foul the prop.

So........another useless idea. How could you tow a lightning ground?
Such a ground doesnt have to be a sheet. it just has to have large
surface area. Could attach it to the bottom of the dinghy and tow it
with proper cable going to the mast but I try not to tow my dinghy.
OK, why not something like a boogie board (foam) covered with Cu foil.
No matter which side it had in the water, it would have lots of area
submerged. It would produce minimal drag. Any thoughts?



--
s/v Mutiny
Rhodes Bounty II
lying Oriental, NC
WDB5619

Lightning does what it wants..not what you want. The mast is a much larger
and somewhat shorter conductor than anything you could run along the
shrouds. So the stroke will divide and almost all of it will stick with the
mast. When the stroke reaches the bottom of the mast some of the energy
will return to the shroud ground via whatever path...destroying anything in
the way.

Straight to the water is best. If not then very gentle and heavy curve to
water. Shortest is best...if not shortest than as close as practical. All
deviations from straight and shortest increase the probability of damage.

Jim Donohue

"Courtney Thomas" wrote in message
...
What would be wrong with a long, ....straight.... piece of aluminum rod
in contact with a location as desired/convenient near the mast top,
(running alongside a shroud) into the water ?

Courtney




Parallax wrote:

Thunderstorms every day and my fear of lightning (totally justified)
have caused me to once again scheme up a way to protect my sailboat.
For protection while anchored, I have a 2'X2' copper sheet with very
thick stranded tinned cable with a clamp for attachment to the mast.
I have considered using this while underway but it would cause too
much drag and would probably foul the prop.

So........another useless idea. How could you tow a lightning ground?
Such a ground doesnt have to be a sheet. it just has to have large
surface area. Could attach it to the bottom of the dinghy and tow it
with proper cable going to the mast but I try not to tow my dinghy.
OK, why not something like a boogie board (foam) covered with Cu foil.
No matter which side it had in the water, it would have lots of area
submerged. It would produce minimal drag. Any thoughts?



--
s/v Mutiny
Rhodes Bounty II
lying Oriental, NC
WDB5619