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Lightning Protection questions
Wayne.B wrote:
On Wed, 12 Nov 2008 17:20:21 -0800 (PST), wrote: The anecdotal evidence is flawed because its conclusoin is based on an observation without comprehensive study of what connected to that boat, the content of soil beneath that boat, where the boat was located in relation to earthed charges, etc. OK, let me ask you this: 300 miles offshore in more than 5,000 feet of salt water, lightning decides to strike a nearby wave top instead of the well grounded 80 ft mast of an all aluminum boat. Why? Butterflies Wings or in this case, probably dust particles or rain drops. The initial ionisation of the air immediatly below the leader of the stroke is dependent on field strength but field strength in most stuations falls off with the square of the distance so a rain drop of lets say 3 mm diameter a meter from the tip of the leader has more influence than that mast 100 metres away. Its only if you have sharp enough edges and enough field strength to get local ionisation on the rigging, St Elmo's fire being the extreme example, that the difference between an 80 ft mast and a 8 ft wave becomes significant. Waves dont have sharp edges . . . -- Ian Malcolm. London, ENGLAND. (NEWSGROUP REPLY PREFERRED) ianm[at]the[dash]malcolms[dot]freeserve[dot]co[dot]uk [at]=@, [dash]=- & [dot]=. *Warning* HTML & 32K emails -- NUL: 'Stingo' Albacore #1554 - 15' Early 60's, Uffa Fox designed, All varnished hot moulded wooden racing dinghy. |
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