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.