[Alberg30] Lightning Protection

[George Dinwiddie]

> Bob Chambers said:
> 
> I completely agree with George, it is difficult if not impossible to really
> protect the boat.  I do think that installing one of the rods with a brush
> of wires at the top of the mast is an excellent idea.  The theory is that it
> will 'bleed off the charge around the boat' making it less likely that you
> will be hit.  I have seen the "St Elmo's Fire" eminating from one of these
> indicating that they are working.

According to http://www.thomson.ece.ufl.edu/lightning/AirTerminals.html#DAS

   Lightning dissipators  The idea that a device might be able to
   prevent a lightning strike is very appealing to the average
   sailor.  Devices that attempt to eliminate or reduce the incidence
   of lightning strikes generally have a bristly appearance caused
   by multiple conducting points.  Under the influence of an electric
   field under a thunderstorm, it is undisputed that these multiple
   points release charge into the air in a similar manner to the
   phenomenon of St. Elmo's fire.  How effective these charge flows
   are at eliminating or reducing lightning has been the subject
   of  investigations by  NASA, FAA, the Departments of Army and
   Air Force, NFPA, and FDOT.  None of these agencies consequently
   supported their use.  Scientific papers by scientists in reputable
   journals have also been negative.  In 1994 Donald Zipse, IEEE
   Fellow, compared the conventional Franklin air terminal with,
   amongst other systems,  multipoint discharge systems and concluded
   "The claims of being able to dissipate any and all lightning
   strokes have been shown to be untrue."  In a subsequent study
   that considered only lightning elimination devices employing
   the point discharge phenomenon, (that is, lightning dissipators)
   Abdul Mousa, also an IEEE Fellow, documents many instances when
   lightning struck towers at Kennedy Space Center and Eglin AirForce
   Base, and one case of a strike to an FAA control tower in Tampa.
   In his paper Dr. Mousa concludes that "Natural downward lightning
   flashes cannot be prevented."  His comments on the subject are
   much more candid in a subsequent posting to the LightningSafety
   listserve.  His phraseology "natural downward lightning" is
   carefully chosen, but does cover the case of a sailboat mast.

-- 
 ----------------------------------------------------------------------
  George Dinwiddie                             gdinwiddie at alberg30.org
  The gods do not deduct from man's allotted span those hours spent in
  sailing.                                    http://www.Alberg30.org/
 ----------------------------------------------------------------------


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