On Jul 2, 10:40*am, Richard Casady
wrote:
On Wed, 1 Jul 2009 12:09:37 -0700 (PDT), Frogwatch

wrote:
HK: *I had forgotten what happens to carbon fiber masts when struck by
lightning. *Maybe Boron fiber..........

*Wood can explode from lightning due to steam explosions. What happens
with carbon? It should be dry but maybe just traces are too much.

Casady

Here is why I think many sailboats are made with carbon fiber masts.
1. Most are sailed in areas without the number of lightning strikes
of Florida.
2. When kept in a marina, the likelyhood of a single specific mast
being hit is low.

Thus, the only time a carbon fiber mast is a danger is when the boat
is the lone boat under a thunderstorm.
It is not the moisture that makes CF masts explode into fibers, it is
the resistance of the tiny gaps between ends of fibers that are filled
with resin. This resistance is sufficient to cause rapid heating.
By comparison, wood masts are poor conductors, even when they have
some moisture in them thus power is dissipated over the entire volume
instead of just at the pointy fiber ends where electric fields tend to
concentrate.
At least, this is my theory and I'll admit it is a stretch.