[MHml] lightning

[Ted Warren]

Ben Franklin understood the issues with lighning. Dave Culp
is the modern Franklin,  experimenting with flying a kite to capture
electricity. ;^)

OK, seriously the idea behind the mast head frizzy devices is to
disipate the local charge about the top of the mast. Sharp conductors
result in field line concentrations that facilitate reduction of the
local
charge in the air. The idea is to prevent the lightning strike. A sharp
spike
of your own design will probably work about as well.

Can you avoid a lightning strike? Probably not. Can you safely conduct
a direct strike into the water withought any damage. Probably not. After

all, it's jumped through thousands of feet of air, ionizing it as it
goes.
Recorded images show an array of discharges near the strike area.
It seems to have a mind of it's own.

My tri suffered a direct hit on it's mooring about 6 years ago. It was
during a
nasty thunderstorm in Salem Harbor. Six boats and two houses were hit.
I reported it to the Harbormaster and he stated that the results were
similar.
The lightning travels down the mast and the standing rigging. Blows a
hole
in
the hull on a direct line with the forestay. The lightning came down the

mast and jumped
to the daggerboard. I had a pair of holes at deck level, port and
starboard,
in
the daggerboard, and another pair of holes at waterlevel out of the
board.
The capshroud chainplates were discolored. The lighning jumped to the
steering
wires (nowhere near the mast), and put pinholes in the akas where they
passed over.
There were tufts of absolutely epoxyless carbon protruding out of the
holes.

The carbon in the daggerboard was also free of epoxy and I could peel it
off

of the board. The mast was a carbon reinforced plywood wingmast and was
toast. It was still standing, but only by a shard.

There are some in the multihull community who ground their masts and
believe

that they have not been struck because of it. We have only anecdotal
evidence
to confirm this. There is also the theory that boats underway will not
be
struck,
because they will not build up a stable charge at the masthead.

Regards,
Ted