[Rhodes22-list] Lighting Rod

[Ron Lipton]

I got interested in this because I know that lightning will punch through fiberglass hulls. The dielectric strength (breakdown voltage) of dry air is about 3000 V/mm. The dielectric strength that I could find for fiberglass is about 20000 V/mm.  So fiberglass (at least the stuff used in PC boards) is only about a factor six or seven better than air.  Humidity actually appears to increase the breakdown voltage a bit. As a rough estimate I would guess that a 10 meter mast "shorts out" the equivalent of 1 meter of fiberglass, much thicker than the hull (the number seems too large to me-I will check some more). So if given the choice the lightning will proceed through the mast and fiberglass rather than the air. That explains why lightning will often punch a hole in the fiberglass on the bottom of a boat, sinking it, rather than find a path outside. 

I am pretty sure fields generated by the motor have no effect. 

Ron

> On Mar 10, 2014, at 21:42, "James Nichols" <jfn302 at yahoo.com> wrote:
> 
> Typically Lightning will not strike anything that does not give it a clear
> path to ground, so running a wire from the mast to the water is only
> inviting lightning to strike the boat more often.  Lightning, like water,
> always looks for the easiest path to ground.  Fiberglass is an awesome
> insulator,  so the mast doesn't typically attract lightning.  Also, while
> lake and sea water conduct electricity (sea water is a much better conductor
> because of the salt) Lightning on a lake setting will more likely hit a tree
> on the shoreline because the path through the tree into the earth is much
> easier than the path through the boat, through the water, then into the
> ground.  Also, while most lightning happens during a storm, so the
> fiberglass on the boat will be wet, the amount of water clinging to the deck
> doesn't usually offer enough of an electrical pathway from the mast to the
> main body of water  that the lightning would choose to strike the boat over
> striking the water directly.
> 
> All these statements aside though, as Ron said, stay away from large metal
> objects on the boat during a storm, and you should be fine.
> 
> As a side note about the quote about deaths of boaters but not sailboats.
> The boats that have deaths are because they are running motorboats that have
> large engines that create large electro-magnetic fields to drive the motor,
> and they tend to run them all out, so the electro-magnetic field is as large
> as it can get, and as they are screaming across the water, what they don't
> realize is they are screaming, "STRIKE ME!!"  And nature says, "Ok."
> 
> -----Original Message-----
> From: rhodes22-list-bounces at rhodes22.org
> [mailto:rhodes22-list-bounces at rhodes22.org] On Behalf Of Ron Lipton
> Sent: Monday, March 10, 2014 7:47 PM
> To: The Rhodes 22 Email List
> Subject: Re: [Rhodes22-list] Lighting Rod
> 
> The Rhodes is a lightning rod - there is no need to install another. The
> real issue is diverting the current into the water rather then through you
> or your electronics.  Such a system would include heavy gauge wire
> connecting the mast to a large area conductor in the water.  Pretty
> cumbersome.  The main thing is to stay away from metal during a storm. A
> good reference is:
> 
> http://edis.ifas.ufl.edu/sg071
> 
> " Every year there are multiple deaths of boaters in open boats caused by
> lightning strikes, but very few reports of sailors in sailboats killed by
> lightning"
> 
> Ron
> 
>> On Mar 10, 2014, at 19:15, <chcarreon at cox.net> wrote:
>> 
>> All,
>> Has anyone installed a lighting rod on a R22?  If so, how did you do it? 
>> 
>> Thanks much,
>> Chuy
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