On Mar 15, 2:34 pm, "Roger Long" wrote:
Like the vast majority of fiberglass boat owners, I'm sailing around in a
boat with next to no lightning protection. I have run a heavy copper
grounding wire from a chain plate to a couple of through hulls directly
below. That will help bleed off some charge and slightly reduce the chance
of being struck. If I am hit however, I imagine it will make the results
worse.

This is on my "someday" list and would be on the "already done" list if I
sailed more to the south. I nearly 40 years of sailing in this part of the
world, I've only once been in a situation that I was huddled below trying to
figure out the best place to be when the bolt hit. That was long ago enough
that I haven't gotten as worked up about the issues as I should.

I don't know as much about the subject as I should since I've spent my
professional life working with boats that have metal masts welded on top of
metal superstructures welded to metal hulls. So, I throw out this idea for
comment as a suggestion for either an interim solution or for cruising
grounds where energetic storms are too infrequent to justify a major
retrofit.

How about a couple of plastic coated battery cables with a snap shackle on
one end and a length of chain on the other. If it looks like you are going
to get caught right in the path of an energetic storm, the kind where you'll
want to either anchor or drift while you seek the safest place in the boat,
just clip them to the shrouds and drop over the side. Nearly straight run
down from the stays (at least if chain plates are not too far inboard), lots
of surface area in the chain, plastic coated wire to protect the topsides.
You wouldn't want to cruise around with this rig but it seems like it might
at least keep a strike from sinking the boat by blowing a hole in it.

--

Roger Long

Most lightning protection systems are designed to ground your mast (or
lightning rod, on houses) to earth with a minimum resistance. The
theory is that by "equalizing" the potential of the mast with the sea
(or ground for houses) the lightning won't "see" the mast (or lighting
rod) as the lowest potential path to ground.

Sounds like black magic, and they always use heavy cables to ground
the lightning rods, so if you should get struck, it won't vaporize.
Sometimes the lightning strike has multiple paths to ground, so you
don't always get the full effect. Sometimes, you only get struck a
little bit (a near miss) so the total power through your ground path
is relatively small.