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Next: More bad news for The Chosen One?
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External
Since: Nov 23, 2007
Posts: 289
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(Msg. 1) Posted: Wed Aug 20, 2008 3:01 pm
Post subject: Lightning
Archived from groups: rec>boats (more info?)
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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 |
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External
Since: Nov 23, 2007
Posts: 289
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(Msg. 2) Posted: Wed Aug 20, 2008 7:11 pm
Post subject: Re: Lightning [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
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On Aug 20, 7:57 pm, Vic Smith <thismailautodele....DeleteThis@comcast.net> wrote:
> On Wed, 20 Aug 2008 19:38:50 -0400, "Eisboch" <noth....DeleteThis@nowhere.com>
> wrote:
>
>
>
>
>
> ><gfretw....DeleteThis@aol.com> wrote in message
> >news:hi9pa4127cu5k6aqkvdgun165nc1curh86@4ax.com...
>
> >> 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.
>
> >Eisboch
>
> This is the best thing I've seen on lightning, and think it pretty
> well hits the mark on what you can do on a boat.
> It's geared toward sailboats, but the principles are there.
> For electronics gear, I would do the same as I do at home with my
> computer and other electronic gear if I anticipate lightning:
> unplug it. An insulated non-conducting case might be appropriate
> for a radio when at sea.http://edis.ifas.ufl.edu/pdffiles/SG/SG07100.pdf
>
> --Vic
That is a good article.
Thanks |
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External
Since: Mar 11, 2005
Posts: 1241
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(Msg. 3) Posted: Wed Aug 20, 2008 7:27 pm
Post subject: Re: Lightning [Login to view extended thread Info.]
Imported from groups: per prev. post (more info?)
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External
Since: Aug 29, 2005
Posts: 678
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(Msg. 4) Posted: Wed Aug 20, 2008 7:38 pm
Post subject: Re: Lightning [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
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<gfretwell.RemoveThis@aol.com> wrote in message
news:hi9pa4127cu5k6aqkvdgun165nc1curh86@4ax.com...
>
> 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.
Eisboch >> Stay informed about: Lightning |
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External
Since: Oct 28, 2006
Posts: 1028
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(Msg. 5) Posted: Wed Aug 20, 2008 7:38 pm
Post subject: Re: Lightning [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
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On Wed, 20 Aug 2008 19:38:50 -0400, "Eisboch" <nothere RemoveThis @nowhere.com>
wrote:
>
><gfretwell RemoveThis @aol.com> wrote in message
>news:hi9pa4127cu5k6aqkvdgun165nc1curh86@4ax.com...
>
>>
>> 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.
>
>Eisboch
>
This is the best thing I've seen on lightning, and think it pretty
well hits the mark on what you can do on a boat.
It's geared toward sailboats, but the principles are there.
For electronics gear, I would do the same as I do at home with my
computer and other electronic gear if I anticipate lightning:
unplug it. An insulated non-conducting case might be appropriate
for a radio when at sea.
http://edis.ifas.ufl.edu/pdffiles/SG/SG07100.pdf
--Vic >> Stay informed about: Lightning |
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External
Since: Aug 29, 2005
Posts: 678
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(Msg. 6) Posted: Wed Aug 20, 2008 11:09 pm
Post subject: Re: Lightning [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
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<ohara5.0 DeleteThis @mindspring.com> wrote in message
news:006a82c8-45e8-467a-b447-055be0126f79@c58g2000hsc.googlegroups.com...
> On Aug 20, 7:57 pm, Vic Smith <thismailautodele... DeleteThis @comcast.net> wrote:
>>
>>
>> This is the best thing I've seen on lightning, and think it pretty
>> well hits the mark on what you can do on a boat.
>> It's geared toward sailboats, but the principles are there.
>> For electronics gear, I would do the same as I do at home with my
>> computer and other electronic gear if I anticipate lightning:
>> unplug it. An insulated non-conducting case might be appropriate
>> for a radio when at sea.http://edis.ifas.ufl.edu/pdffiles/SG/SG07100.pdf
>>
>> --Vic
>
> That is a good article.
>
> Thanks
It is a good article in terms of what happens when you get hit and how to
design for a hit.
The other school of thought is a design to minimize your chances of getting
hit in the first place.
Both approaches are not fool proof, as the effects of a hit are not 100%
predictable, nor is a system designed to minimize the chances of a hit 100%
effective.
Personally, having many years of experience in designing vacuum processing
equipment that contain controlled plasma discharges, (basically the same as
lightning, except it is a sustained and controlled electrical discharge
through ionized gas), I am more of a believer in the concept of minimizing
the conditions that would lead to a strike in the first place. Ironically,
the approach is almost the opposite of trying to design a system to capture
the energy of a strike and safely transfer it to ground.
Eisboch >> Stay informed about: Lightning |
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External
Since: Jul 11, 2007
Posts: 225
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(Msg. 7) Posted: Thu Aug 21, 2008 5:47 am
Post subject: Re: Lightning [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
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On Wed, 20 Aug 2008 23:09:52 -0400, "Eisboch" <nothere RemoveThis @nowhere.com>
wrote:
>
><ohara5.0 RemoveThis @mindspring.com> wrote in message
>news:006a82c8-45e8-467a-b447-055be0126f79@c58g2000hsc.googlegroups.com...
>
>> On Aug 20, 7:57 pm, Vic Smith <thismailautodele... RemoveThis @comcast.net> wrote:
>>>
>>>
>>> This is the best thing I've seen on lightning, and think it pretty
>>> well hits the mark on what you can do on a boat.
>>> It's geared toward sailboats, but the principles are there.
>>> For electronics gear, I would do the same as I do at home with my
>>> computer and other electronic gear if I anticipate lightning:
>>> unplug it. An insulated non-conducting case might be appropriate
>>> for a radio when at sea.http://edis.ifas.ufl.edu/pdffiles/SG/SG07100.pdf
>>>
>>> --Vic
>>
>> That is a good article.
>>
>> Thanks
>
>
>It is a good article in terms of what happens when you get hit and how to
>design for a hit.
>
>The other school of thought is a design to minimize your chances of getting
>hit in the first place.
>
>Both approaches are not fool proof, as the effects of a hit are not 100%
>predictable, nor is a system designed to minimize the chances of a hit 100%
>effective.
>
>Personally, having many years of experience in designing vacuum processing
>equipment that contain controlled plasma discharges, (basically the same as
>lightning, except it is a sustained and controlled electrical discharge
>through ionized gas), I am more of a believer in the concept of minimizing
>the conditions that would lead to a strike in the first place. Ironically,
>the approach is almost the opposite of trying to design a system to capture
>the energy of a strike and safely transfer it to ground.
>
Biggest trouble with avoidance is that any boat is the tallest thing
around, and will attract any lightning that would have struck anywhere
near there without it. You get a choice of the mast or the lightning
rod. No strikes on boats just isn't doable. They even put masts on
powerboats to get the radar and VHF antennae higher for more range.
The only counter measure that really works is radar and a very big
engine.
Hiding under a bridge works, if there is room. A powerboat in a marina
next to sailboats won't be hit. Someone checked statistics on one make
and model of powerboat and found that more than ten percent had been
hit in the last five years.
Casady >> Stay informed about: Lightning |
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External
Since: Nov 23, 2007
Posts: 289
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(Msg. 8) Posted: Thu Aug 21, 2008 5:51 am
Post subject: Re: Lightning [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
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On Aug 21, 1:47 am, richardcas....DeleteThis@earthlink.net (Richard Casady)
wrote:
> On Wed, 20 Aug 2008 23:09:52 -0400, "Eisboch" <noth....DeleteThis@nowhere.com>
> wrote:
>
>
>
>
>
> ><ohara....DeleteThis@mindspring.com> wrote in message
> >news:006a82c8-45e8-467a-b447-055be0126f79@c58g2000hsc.googlegroups.com...
>
> >> On Aug 20, 7:57 pm, Vic Smith <thismailautodele....DeleteThis@comcast.net> wrote:
>
> >>> This is the best thing I've seen on lightning, and think it pretty
> >>> well hits the mark on what you can do on a boat.
> >>> It's geared toward sailboats, but the principles are there.
> >>> For electronics gear, I would do the same as I do at home with my
> >>> computer and other electronic gear if I anticipate lightning:
> >>> unplug it. An insulated non-conducting case might be appropriate
> >>> for a radio when at sea.http://edis.ifas.ufl.edu/pdffiles/SG/SG07100.pdf
>
> >>> --Vic
>
> >> That is a good article.
>
> >> Thanks
>
> >It is a good article in terms of what happens when you get hit and how to
> >design for a hit.
>
> >The other school of thought is a design to minimize your chances of getting
> >hit in the first place.
>
> >Both approaches are not fool proof, as the effects of a hit are not 100%
> >predictable, nor is a system designed to minimize the chances of a hit 100%
> >effective.
>
> >Personally, having many years of experience in designing vacuum processing
> >equipment that contain controlled plasma discharges, (basically the same as
> >lightning, except it is a sustained and controlled electrical discharge
> >through ionized gas), I am more of a believer in the concept of minimizing
> >the conditions that would lead to a strike in the first place. Ironically,
> >the approach is almost the opposite of trying to design a system to capture
> >the energy of a strike and safely transfer it to ground.
>
> Biggest trouble with avoidance is that any boat is the tallest thing
> around, and will attract any lightning that would have struck anywhere
> near there without it. You get a choice of the mast or the lightning
> rod. No strikes on boats just isn't doable. They even put masts on
> powerboats to get the radar and VHF antennae higher for more range.
> The only counter measure that really works is radar and a very big
> engine.
> Hiding under a bridge works, if there is room. A powerboat in a marina
> next to sailboats won't be hit. Someone checked statistics on one make
> and model of powerboat and found that more than ten percent had been
> hit in the last five years.
>
> Casady
Eisboch:
C'mon down and you can help build a big sputtering system for us. >> Stay informed about: Lightning |
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External
Since: Nov 23, 2007
Posts: 289
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(Msg. 9) Posted: Thu Aug 21, 2008 6:32 am
Post subject: Re: Lightning [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
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On Aug 21, 9:01 am, "Eisboch" <r....DeleteThis@nowhere.com> wrote:
> <ohara....DeleteThis@mindspring.com> wrote in message
>
> news:0c3be1ba-dfad-401c-bb56-9b9438742d6f@y21g2000hsf.googlegroups.com...
>
>
>
> > Eisboch:
>
> > C'mon down and you can help build a big sputtering system for us.
>
> It's funny. The bulk of the systems we designed and built were conventional
> batch type box coaters for optics, utilizing thermal and electron beam
> evaporation, often with an ion source for controlling the packing density.
> Mostly for high energy laser stuff, but we also built several systems over
> the years for ophthalmic coatings. "Neutral Green" 
>
> We also built many sputter deposition systems for everything from optics,
> diamond-like coatings, to razor blades.
> Plasma processing systems was my personal favorite and interest. It
> combines so many technical disciplines that it was never boring.
>
> Eisboch
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 >> Stay informed about: Lightning |
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External
Since: Nov 23, 2007
Posts: 289
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(Msg. 10) Posted: Thu Aug 21, 2008 7:30 am
Post subject: Re: Lightning [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
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On Aug 21, 10:09 am, "Eisboch" <r....RemoveThis@nowhere.com> wrote:
> "Richard Casady" <richardcas....RemoveThis@earthlink.net> wrote in message
>
> news:48bf6d66.415281265@news.east.earthlink.net...
>
>
>
> > 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. >> Stay informed about: Lightning |
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External
Since: Nov 23, 2007
Posts: 289
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(Msg. 11) Posted: Thu Aug 21, 2008 7:36 am
Post subject: Re: Lightning [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
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On Aug 21, 10:30 am, ohara... RemoveThis @mindspring.com wrote:
> On Aug 21, 10:09 am, "Eisboch" <r... RemoveThis @nowhere.com> wrote:
>
>
>
> > "Richard Casady" <richardcas... RemoveThis @earthlink.net> wrote in message
>
> >news:48bf6d66.415281265@news.east.earthlink.net...
>
> > > 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. >> Stay informed about: Lightning |
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External
Since: Jan 24, 2006
Posts: 2759
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(Msg. 12) Posted: Thu Aug 21, 2008 9:01 am
Post subject: Re: Lightning [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
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<ohara5.0 RemoveThis @mindspring.com> wrote in message
news:0c3be1ba-dfad-401c-bb56-9b9438742d6f@y21g2000hsf.googlegroups.com...
>
> Eisboch:
>
> C'mon down and you can help build a big sputtering system for us.
It's funny. The bulk of the systems we designed and built were conventional
batch type box coaters for optics, utilizing thermal and electron beam
evaporation, often with an ion source for controlling the packing density.
Mostly for high energy laser stuff, but we also built several systems over
the years for ophthalmic coatings. "Neutral Green"
We also built many sputter deposition systems for everything from optics,
diamond-like coatings, to razor blades.
Plasma processing systems was my personal favorite and interest. It
combines so many technical disciplines that it was never boring.
Eisboch >> Stay informed about: Lightning |
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| Back to top |
|
| |
External
Since: Jan 24, 2006
Posts: 2759
|
(Msg. 13) Posted: Thu Aug 21, 2008 9:58 am
Post subject: Re: Lightning [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
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<ohara5.0 DeleteThis @mindspring.com> wrote in message
news:e75e76a6-fca2-4586-9853-9cc565740ee7@d77g2000hsb.googlegroups.com...
> On Aug 21, 9:01 am, "Eisboch" <r... DeleteThis @nowhere.com> wrote:
>> <ohara... DeleteThis @mindspring.com> 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 >> Stay informed about: Lightning |
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External
Since: Jan 24, 2006
Posts: 2759
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(Msg. 14) Posted: Thu Aug 21, 2008 11:47 am
Post subject: Re: Lightning [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
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<ohara5.0 DeleteThis @mindspring.com> wrote in message
news:9270eeba-1e94-4786-ae76-ff806d9d4881@j22g2000hsf.googlegroups.com...
> On Aug 21, 10:30 am, ohara... DeleteThis @mindspring.com wrote:
>> On Aug 21, 10:09 am, "Eisboch" <r... DeleteThis @nowhere.com> wrote:
>>
>>
>>
>> > "Richard Casady" <richardcas... DeleteThis @earthlink.net> wrote in message
>>
>> >news:48bf6d66.415281265@news.east.earthlink.net...
>>
>> > > 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 >> Stay informed about: Lightning |
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External
Since: Jul 11, 2007
Posts: 225
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(Msg. 15) Posted: Thu Aug 21, 2008 1:42 pm
Post subject: Re: Lightning [Login to view extended thread Info.]
Archived from groups: per prev. post (more info?)
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On Wed, 20 Aug 2008 19:38:50 -0400, "Eisboch" <nothere.DeleteThis@nowhere.com>
wrote:
>
><gfretwell.DeleteThis@aol.com> wrote in message
>news:hi9pa4127cu5k6aqkvdgun165nc1curh86@4ax.com...
>
>>
>> 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.
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 >> Stay informed about: Lightning |
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