[Rhodes22-list] sailing and lightning

[Ronald Lipton]

It's really hard to do controlled experiments with sailboats and 
lightning.
We can try to make some estimates, but the hough currents and low
probabilities keep this stuff in the realm of folk wisdom for the most 
part.
It seems very unlikely that the "static dissipators" on the market have 
anything
but a marginal effect in preventing strikes.  You can use the "circle 
of protection"
to calculate the increased probability of a strike for a given mast 
height.
For a mast 25' high, given a 60 degree "circle" the area attracted by 
the mast
is Area = pi * (Mast height *  tan(60))^2 = 5890 sq ft, about a factor 
of
30 larger than the boat area.  This may or may not be a worry depending
on what you think the probability is of being struck by lightning.

The grounding recommended should work - but you need a SERIOUS amount
of conductor to avoid being vaporized by the thousands of amps you are 
trying
to conduct.  Fresh water is at least a factor of 10 less conductive 
than salt water,
so you need a much bigger plate to make decent contact.  In addition it 
is difficult
to make reliable electrical contact with aluminum due to the oxide that 
builds up
on the surface.  Any contact to the mast should be large area and 
preferably
also penetrate the surface oxide.

Personally, it seems to be the best policy to stay in out of the rain.

Ron

> From: "Tootle" <ekroposki at charter.net>
>>
>> Where did it go?
>>
>> Where is that question I posted?
>>
>> Here is what started the question:
>>
>> http://www.cdc.gov/nasd/docs/d000001-d000100/d000007/d000007.html
>>
>> It say you should ground your mast.  But it does tell me how to 
>> ground the
>> mast that I can figure out. So how do you ground a sail boat??
>>
>> Bill Effros, you are the expert on this subject, aren't you?
>>
>> So how do you ground a sail boat?
>>
>> John Lock, you are the current research expert.  What is the correct 
>> answer?
>>
>> Ed K
>> Greenville, SC, USA
>> -- 
>> View this message in context: 
>> http://www.nabble.com/Gone-sailing.-tf2016691.html#a5549206
>> Sent from the Rhodes22 forum at Nabble.com.
>>
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