Re: Lightning & Bathtubs

dnoyeB wrote:
On Sat, 07 Jun 2008 19:44:08 -0700, w_tom wrote:

On Jun 6, 10:47 pm, dnoyeB <as...@xxxxxxxx> wrote:
...
Thats incorrect. And blunt rods being better would be some remarkable
new science.
...
If you discharge the static electricity, then you can stop lightning. So the claim that discharging the clouds/ground will stop lightning is
100% scientific and correct. The flaw is that you can't guarantee that
you can discharge it fully, or continuously or fast enough.

We may share the same resonings because what I state is based on the
laws of physics. So my statements are true.

Your statements are based in popular myth - with no basis in laws of
physics. Is it knowledge because the urban myth is popular? That same
lesson (flawed but popular reasoning) also proved Saddam's mythical
WMDs. A fact does not exist due to popular belief.

No, my statements are based on scientific fact. The laws of physics. It is knowledge because I have a 4 year Electrical engineering degree. Not because I over heard some myth.

It is true that if you have a sharp point at high voltage, there is a high electric field around the point that can break down the air and ionize it. It does not follow that a sharp point will significantly dissipate/neutralize the charge creating lightning and prevent lightning strikes at a rod.

The concentrated charge primarily accumulates in the cloud. If you are discharging the "static electricity" you are neutralizing the charge in the cloud. You assume there will be enough current from the point to dissipate that charge. I have seen no reason to believe that is true. A paper at
http://www.lightningsafety.com/nlsi_lhm/magic.pdf
writes about the problems of emitting charge from a sharp points. Just one of the problems is that, for most lightning, you are creating positive ions which are not particularly mobile.

A paper at
http://www.lightningsafety.com/nlsi_lhm/charge_transfer.html
is about a scheme (CTS) emit charge from sharp points to protect an area from a lightning strike. A conclusion in the paper is "The undeniable facts are that 'dissipation' devices do not prevent the occurrence of cloud-to-ground lightning strikes..." The system may, or may not, reduce the probability of lightning striking a rod. That is not necessarily an advantage. There will be as much lightning, and it will strike something. The point (if you excuse the expression) of rods is to provide a relatively safe place for lightning to strike.

----------------------
"No sharp bends" is because of inductance, not "leaking off the static charge".

--
bud--




First, the myth is that sharp (pointed) rods are better. Science and
numbers say blunt rods make better lightning rods. From a 1999 paper in
Journal of Applied Meteorology by Moore, Rison, Mathis, and Aulich
(published May 2000):
Following tradition, however, sharp-tipped Franklin rods are widely
installed despite evidence that, on occasion, lightning strikes objects
in their vicinity. In recent tests of various tip configurations to
determine which were preferentially struck by lightning, several
hemispherically tipped, blunt rods were struck but none of the nearby,
sharper rods were "hit" by lightning.

I did not say sharp pointed rods are better. I said they would discharge static. And they do. Just a blunt rods let static build up. Which they do. In a contest of who gets the most lightning strikes a blunt rod naturally will. By definition. The point rod attempts to reduce the number of strikes anyway. The blunt would do just the opposite.


Second: myth that a lightning rod dissipates static charges also was
repeatedly criticized as junk science. From Wikipedia:
Lightning dissipators have been widely discredited and criticized by
lightning researchers over the last 30 years.

Sorry, it is fact that static will be released through a pointy rod more than it will through a blunt one. Its not myth. I can't say if this makes it better at reducing the number of strikes. I'm not making that claim.

Numerous peer reviewed papers also discredit that "discharge the
static electricity, then you can stop lightning" theory. Again, NFPA
was quite blunt about it. There exists zero supporting facts or
research for this "discharge the static electricity" myth. None. NFPA
said:
Accordingly, based on the Bryan Panel Report and the record before it,
the Council, in its most recent consideration of the question whether
to issue a standard for the ESE systems, concluded, as it had in the
past, that there was no basis for the Council to issue a standard for
ESE lightning protection systems, and that given the lack of validation
of the primary claims made for the ESE technology, renewed standards
development activities for ESE systems was not appropriate.

Thats fine since I don't claim rods stop lightining.


Even worse, that 'discharge the air' theory creates a human safety
risk. From Hartono and Robiah entitled "A Long Term Study on the
Performance of Early Streamer Emission ...":
The failure of the ESE air terminals to intercept nearby lightning
strikes posed an unacceptable risk to public safety.
Furthermore:
The case studied submitted to the NFPA provided indisputable evidence
that lightning do strike the buildings after they were installed with
the ESE air terminals. ... the presence of several ESE air terminals
... still resulted in lightning strikes on one or more of those
buildings. ... The case studies highlight the very close proximity of
some lightning strikes to the ESE air terminals, shoring that they are
unable to protect buildings as claimed by their manufacturers.

ESE system is different from pointy grounded rod.

If those ESE terminals discharged air, then why so many lightning
strikes even near the ESE air terminals? Because air terminals that
discharge static are based in junk science reasoning.

Not only was the NFPA roundly critical of that 'discharge the air'
myth. NFPA also cited numerous studies (ie Hartono and Robiah) that
showed "discharge the static electricity" devices provided NO
protection. Speculation that lightning rods protect by discharging the
air is only junk science and is not found in science. We learned this
same lesson from history: Saddam's WMDs. Popular belief does not create
fact. Facts come from learning the science. Static discharging does
not provide protection.

How many sources completely discredit this 'discharge the air'
myth? Science (laws of physics and experiments) says blunt rods are
superior. Discharging inches of air around a lightning rod neither
stops nor averts nor reduces lightning strike frequency. Lightning
strikes are made irrelevant by connecting / diverting / channeling /
conducting that inevitable lightning strike into earth. Protection is
about dissipating that energy harmlessly in earth. That energy must be
dissipated somewhere. Inside a building (destructively) or inside
earth? Discharging static charges is the same logic that also proved
"Saddam's WMDs" - junk science reasoning promoted by popularity. How
many science sources need be quoted?

No offence but you still show a lack of understanding of the fundamentals. This is not junk science. its sound theory. Even if its proven incorrect.

You are still conflating lightning attraction with static dissipation. pointy rods are better at dissipation. This is scientific fact. This is not myth. Round rods being better at protection I still will not agree with. Maybe they get more strikes, but they can artifically create additional strikes simply by being blunt. Any lighting creation device will be blunt.

.

Relevant Pages

  • Re: Lightning & Bathtubs
    ... science. ... If you discharge the static electricity, then you can stop lightning. ... the myth is that sharp rods are better. ...
    (alt.home.repair)
  • Re: Lightning & Bathtubs
    ... science. ... If you discharge the static electricity, then you can stop lightning. ... the myth is that sharp rods are better. ...
    (alt.home.repair)
  • Re: Lightning & Bathtubs
    ... new science. ... If you discharge the static electricity, then you can stop lightning. ... the myth is that sharp rods are better. ...
    (alt.home.repair)
  • Re: Lightning Damage
    ... Lightning is not DC where you worry about the resistance but a complex waveform that requires a low inductance and is treated as a R.F. problem. ... Some of the early work on lightning protection came from measuring the rise time on strikes to the Empire State Building with low bandwidth cathode ray tube oscilloscopes. ... In a metal building lightning rods may not offer additional protection as the building itself is the lowest impedance structure. ...
    (sci.astro.amateur)
  • Re: Weather Station and Lighting
    ... First, even demonstrated in professional papers, blunt rods ... direct lightning strikes are typically so trivial that even ... superior protection. ... Such Early Streamer Emission (ESE) devices were so ...
    (uk.sci.weather)