On Wed, 20 Aug 2008 19:38:50 -0400, "Eisboch"
wrote:


wrote in message
.. .


I am always curious about how a boat takes a hit but I do have some
experience with a lightning rod. I put a 3' copper rod over my weather
station with a pointy stainless steel tip, connected to 2ga copper
wire and terminated in a ground rod (connected to my extensive house
grounding system)
It has been hit twice that I know of and I was about 30' away during
one of them. A mexican laborer was pretty much under it, plastered
against my garage door. Other than the poop reflex we were totally
unaffected.. The steel garage door he was plastered to is bonded to
the same grounding system as the lightning rod as is the wet concrete
driveway I was standing on.
We were fine. The weather station ... not so much ... either time.


Our house has a copper clad cupula, grounded to two metal rods located near
the house power panels.
It's been hit at least three times. Once, the driveway (near the metal
rods) snapped, crackled and popped for about 5 seconds following the hit as
the energy was absorbed by the ground plane. Originally, it also had a big,
copper weather vane. That has long since been vaporized.

Fine for a house .... not so fine for a boat.

Did the cupola have a 000 wire and a ten foot long grounding rod, the
practice with lightning rods?

Casady

wrote in message
...
On Aug 21, 9:01 am, "Eisboch" wrote:
wrote in message


We need to make a sputter system to deposit thin multilayers on small
diameter parabolic mandrels. The mandrels are highly polished and we
need coatings with surface and interfacial roughness of less than 10
angstroms. These are for x-ray mirrors. See our web site at
www.parallax-x-ray.com


Your process requirements are a bit out of my league, (primary concern is
surface roughness 10 angstroms). I have access to a small sputter
deposition system that was originally built for MEMs type research and small
scale production. It is basically new, very little use and would probably
be cheaper than designing and building your own system, assuming the
configuration, instrumentation and metrology is suitable for your purposes.

http://www.vptec.com/New_Pages/VPT_Products.htm

The system I am referring to is similar to the "SP-2000" Click on "Sputter
Systems", then SP-2000.

My company was recently sold, however this piece of equipment was not part
of the sale. I was going to hold on to it for my own purposes, or find
someone that can use it.

If you are interested, I can get the details of the configuration, power
supplies, cathodes, instrumentation, etc. and forward them to your
company's address.

Eisboch

On Wed, 20 Aug 2008 19:27:06 -0400, wrote:

On Wed, 20 Aug 2008 15:01:04 -0700 (PDT),
wrote:

In another thread some mentioned lightning protection. There seem to
b e several schools of thought on the topic ranging from preventing a
strike to dissipating it when it happens. I really do not think there
is much you can do to prevent a strike on a sailboat except to be in
proximity to other tall objects. When you consider the voltages
involved, everything becomes a conductor which is why a tall tree gets
hit as often as a tower of the same height. I also do not think that
lightning dissipators work. In fact, they may make you more
susceptible to a strike by increasing the E field in its vicinity.
Given that the water is so murky on the subject of protection,, I
favor getting rid of it after a strike and attaching a small conductor
to your hull isnt the best way. You may end up with a hole in your
hull. Instead, I have a 2'X2' copper plate soldered and bolted to 00
gage tinned battery cable 20' long with an eyelet on the other end.
When in a storm, I throw the plate over the side and attach the eyelet
to the mast up high so as to minimize bends in the cable. I want to
have the current go through the cable while having the shrouds help
protect us inside them.
I once did a calculation on the probability of a lone sailboat getting
hit if out in a storm and came up with a number that seemed too high
yet when compared with insurance statistics turned out to be
reasonable. Basically, you should avoid being the only tall thing
under such a storm. Being one of many tall things is ok

I am always curious about how a boat takes a hit but I do have some
experience with a lightning rod. I put a 3' copper rod over my weather
station with a pointy stainless steel tip, connected to 2ga copper
wire and terminated in a ground rod (connected to my extensive house
grounding system)
It has been hit twice that I know of and I was about 30' away during
one of them. A mexican laborer was pretty much under it, plastered
against my garage door. Other than the poop reflex we were totally
unaffected.. The steel garage door he was plastered to is bonded to
the same grounding system as the lightning rod as is the wet concrete
driveway I was standing on.
We were fine. The weather station ... not so much ... either time.

000 wire and a ten foot long grounding rod, is the customary practice
with lightning rods.

Casady

"Richard Casady" wrote in message
...


You evidently think a lightning rod will somehow increase the danger,
but such has been proven by long experience not to be the case. BS in
other words. The lightning rod doesn't know or care what is under it.
It prevents strikes in a 90 degree cone under it. Works equally well
for buildings, boats, and powerlines.

Casady


I think we are talking two different concepts here.

A lightning rod is designed to be "the" point of strike, should one occur
and equipped with sufficiently sized conductors to discharge the strike to
ground.
..
I am talking about making the building, boat, or whatever less favorable to
the strike.

It has to do with the positive column .... based on the static charge that
builds on the ground point.

Eisboch

On Aug 21, 10:09 am, "Eisboch" wrote:
"Richard Casady" wrote in message

...



You evidently think a lightning rod will somehow increase the danger,
but such has been proven by long experience not to be the case. BS in
other words. The lightning rod doesn't know or care what is under it.
It prevents strikes in a 90 degree cone under it. Works equally well
for buildings, boats, and powerlines.

Casady

I think we are talking two different concepts here.

A lightning rod is designed to be "the" point of strike, should one occur
and equipped with sufficiently sized conductors to discharge the strike to
ground.
.
I am talking about making the building, boat, or whatever less favorable to
the strike.

It has to do with the positive column .... based on the static charge that
builds on the ground point.

Eisboch

Wiki has a good discussion of Lightning rods and basically the theory
of preventing a strike by dissipating charge from the ground is very
controversial. Like Eisboch, I have some familiarity with HV and
large electrical sparks, My graduate work was on electrical particle
charging by very high electric fields to improve electrostatic
precipitators. My experience with this is that things like so-called
lightning dissipators tend to increase the likelyhood of attracting a
spark. I am not certain this experience can be generalized to
lightning but such dissipators do not seem to work well in practice
any better than conventional lightning rods.
The safe approach would seem to be to have a very good conducting path
with few bends going to a large grounded conductor.
I do not think that those sintered metal plates used to ground radios
will work to replace a large area conductor for lightning. The
electric fields inside the pores of those plates will essentially be
zero so that the actual area for the purpose of dissipating a
lightning strike will basicall be the outside surface area that is
fairly small.

On Aug 21, 10:30 am, wrote:
On Aug 21, 10:09 am, "Eisboch" wrote:



"Richard Casady" wrote in message

.. .

You evidently think a lightning rod will somehow increase the danger,
but such has been proven by long experience not to be the case. BS in
other words. The lightning rod doesn't know or care what is under it.
It prevents strikes in a 90 degree cone under it. Works equally well
for buildings, boats, and powerlines.

Casady

I think we are talking two different concepts here.

A lightning rod is designed to be "the" point of strike, should one occur
and equipped with sufficiently sized conductors to discharge the strike to
ground.
.
I am talking about making the building, boat, or whatever less favorable to
the strike.

It has to do with the positive column .... based on the static charge that
builds on the ground point.

Eisboch

Wiki has a good discussion of Lightning rods and basically the theory
of preventing a strike by dissipating charge from the ground is very
controversial. Like Eisboch, I have some familiarity with HV and
large electrical sparks, My graduate work was on electrical particle
charging by very high electric fields to improve electrostatic
precipitators. My experience with this is that things like so-called
lightning dissipators tend to increase the likelyhood of attracting a
spark. I am not certain this experience can be generalized to
lightning but such dissipators do not seem to work well in practice
any better than conventional lightning rods.
The safe approach would seem to be to have a very good conducting path
with few bends going to a large grounded conductor.
I do not think that those sintered metal plates used to ground radios
will work to replace a large area conductor for lightning. The
electric fields inside the pores of those plates will essentially be
zero so that the actual area for the purpose of dissipating a
lightning strike will basicall be the outside surface area that is
fairly small.

My reasoning on why the so-called dissipators do not work (these
things often look like a brush atop a mast) is that the actual static
charge that would need to be dissipated is enormous. Basically, you
are trying to dissipate a charge from many meters around your boat (or
other object) and in these kinds of E fields, everything conducts.
So, if you do end up dissipating this charge, you ionize the air above
the dissipator causing a strike. In general, these systems are well
grounded so they then act like a conventional lightning rod.

On Thu, 21 Aug 2008 10:09:55 -0400, "Eisboch" wrote:

I think we are talking two different concepts here.

A lightning rod is designed to be "the" point of strike, should one occur
and equipped with sufficiently sized conductors to discharge the strike to
ground.
.
I am talking about making the building, boat, or whatever less favorable to
the strike.

It has to do with the positive column .... based on the static charge that
builds on the ground point.

I am not sure what you have in mind, but lightning rods work, and are
about as complicated as a pool ball, hence reliable. However, the 000
wire is not cheap. Every powerline has lightning protection, a
grounded wire above the power conductors. What does every electric
utility know? None the less lightning does hit powerlines. A long wire
lacks sharp points, if that makes a lot of difference.

Casady

wrote in message
...
On Aug 21, 10:30 am, wrote:
On Aug 21, 10:09 am, "Eisboch" wrote:



"Richard Casady" wrote in message

.. .

You evidently think a lightning rod will somehow increase the danger,
but such has been proven by long experience not to be the case. BS in
other words. The lightning rod doesn't know or care what is under it.
It prevents strikes in a 90 degree cone under it. Works equally well
for buildings, boats, and powerlines.

Casady

I think we are talking two different concepts here.

A lightning rod is designed to be "the" point of strike, should one
occur
and equipped with sufficiently sized conductors to discharge the strike
to
ground.
.
I am talking about making the building, boat, or whatever less
favorable to
the strike.

It has to do with the positive column .... based on the static charge
that
builds on the ground point.

Eisboch

Wiki has a good discussion of Lightning rods and basically the theory
of preventing a strike by dissipating charge from the ground is very
controversial. Like Eisboch, I have some familiarity with HV and
large electrical sparks, My graduate work was on electrical particle
charging by very high electric fields to improve electrostatic
precipitators. My experience with this is that things like so-called
lightning dissipators tend to increase the likelyhood of attracting a
spark. I am not certain this experience can be generalized to
lightning but such dissipators do not seem to work well in practice
any better than conventional lightning rods.
The safe approach would seem to be to have a very good conducting path
with few bends going to a large grounded conductor.
I do not think that those sintered metal plates used to ground radios
will work to replace a large area conductor for lightning. The
electric fields inside the pores of those plates will essentially be
zero so that the actual area for the purpose of dissipating a
lightning strike will basicall be the outside surface area that is
fairly small.

My reasoning on why the so-called dissipators do not work (these
things often look like a brush atop a mast) is that the actual static
charge that would need to be dissipated is enormous. Basically, you
are trying to dissipate a charge from many meters around your boat (or
other object) and in these kinds of E fields, everything conducts.
So, if you do end up dissipating this charge, you ionize the air above
the dissipator causing a strike. In general, these systems are well
grounded so they then act like a conventional lightning rod.

Indeed, they are controversial, but the theory is supported by many in the
"field" so to speak.
My understanding is that they act in a similar manner to a dark space shield
around the back side and edges of a sputtering target. When the target or
cathode is energize with enough voltage to ionize the partial pressure
within the vacuum chamber, the small space (1/4 inch or so, depending on
pressure and voltage) between the cathode and the grounded dark space shield
does not have sufficient ions to sustain current flow, so there is no
plasma. Move the dark space shield *away* from the cathode (increasing
the space) and a discharge current will start. I am sure you are familiar
with the Faraday Column and the voltage division nature of a plasma (or
lightning) discharge.

One explanation of the workings of the static charge dissipaters is similar.
There simply are not enough ions around each of the thousands of points so
sustain current flow.

In the case of my boat that has one .... I figure it can't do any harm, even
if the theory is wrong.

Eisboch

"Richard Casady" wrote in message
...
On Thu, 21 Aug 2008 10:09:55 -0400, "Eisboch" wrote:

I think we are talking two different concepts here.

A lightning rod is designed to be "the" point of strike, should one occur
and equipped with sufficiently sized conductors to discharge the strike to
ground.
.
I am talking about making the building, boat, or whatever less favorable
to
the strike.

It has to do with the positive column .... based on the static charge that
builds on the ground point.

I am not sure what you have in mind, but lightning rods work, and are
about as complicated as a pool ball, hence reliable. However, the 000
wire is not cheap. Every powerline has lightning protection, a
grounded wire above the power conductors. What does every electric
utility know? None the less lightning does hit powerlines. A long wire
lacks sharp points, if that makes a lot of difference.

Casady

We still aren't connecting here, Richard. I agree with everything you are
saying, if you *want* to design something that is more likely to take the
strike instead of another nearby object or surface.

I am talking about trying to make the strike less likely in that area. I
sorta agree with the point ohara made .... they are probably too small to
have a significant affect.

But .... here's one type that is marketed:

http://www.lpsnet.com/ALS.asp

Ok .... we've beat it to death.

Eisboch

Slightly OT, slightly...

http://www.youtube.com/watch?v=HcalasGr_uk

Video: "Bird on a wire" Faraday cage footage...

I know it's been posted before, but it is still cool..



On Thu, 21 Aug 2008 10:09:55 -0400, "Eisboch" wrote:


"Richard Casady" wrote in message
.. .


You evidently think a lightning rod will somehow increase the danger,
but such has been proven by long experience not to be the case. BS in
other words. The lightning rod doesn't know or care what is under it.
It prevents strikes in a 90 degree cone under it. Works equally well
for buildings, boats, and powerlines.

Casady


I think we are talking two different concepts here.

A lightning rod is designed to be "the" point of strike, should one occur
and equipped with sufficiently sized conductors to discharge the strike to
ground.
.
I am talking about making the building, boat, or whatever less favorable to
the strike.

It has to do with the positive column .... based on the static charge that
builds on the ground point.

Eisboch