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Old 22-05-2018, 04:26   #31
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Join Date: May 2014
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Boat: 41' yawl
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What is this mystery electrical accessory?

[QUOTE=AlanR;2636754]
Quote:
Originally Posted by chris95040 View Post
Many sailboats are struck by lightning at the masthead as it seeks a path to ground. What percentage of them end up with a hole punched through the hull?[/QUOTE



I think many reports fail to differentiate between a lightning strike and "damage caused by lightning."



Have you seen the damage caused by a lightning strike on an unprotected chimney. It's like a bomb went off. I believe that many (most) reports are of lightning damage from induced current, and so current flows through equipment where these high voltages break down insulation, wrecking the equipment, and track to earth through through a metal hull or the sacrificial anode. Still very much less current than the original strike.



Induced current is the same effect that causes a transformer to work. The lightning's huge current creates a huge magnetic field, which induces currents in any conductor within that field. The crackles you can often hear in a medium wave broadcast band radio are from lightning strikes perhaps thousands of miles away. You can not see the flash or hear the thunder, only hear the electrical pulse, through your radio.



A real strike had a huge current, causes explosions, fires, splits trees and kills people standing nearby. That is, unless there is a proper lightning conductor, like the one on a church spire, or several lengths of anchor chain. Not the little wire in the unknown piece of equipment we are discussing. That would most certainly provide no protection against a direct strike.



73's


Great. But you said a significant copper conductor hooked up to a shroud would ‘instantly evaporate’ in a strike. Thats the subject I’m discussing.

As is *always* the case in these conversations, rather than directly answer my question about how that would happen, you’ve started talking about exploding chimneys. I know theres a lot of current flow in a strike. I’m quite familiar with maxwells equations and would certainly expect significant induced current damage. Chimneys and bricks have lots of trapped air that absolutely poses an explosion hazard. All true.

What I would not expect is for that copper conductor to ‘instantly evaporate’ from current supplied by a series connection to a rigging terminal.

Nor would I expect a hole to be blown through my hull in a strike. It certainly does happen, but it is not the most common result of a strike.
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