On Mar 15, 6:58 pm, RW Salnick wrote:
Stephen Trapani inscribed in red ink for all to know:



Charlie Morgan wrote:

On Thu, 15 Mar 2007 15:34:33 -0400, "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.

Honestly? There is absolutely nothing you can do to a 30 or 40 foot
boat to
protect it in the slightest. It may make you feel better, but there's
truly no
way you are going to harness and direct a lightning strike that hits
your mast.
Lightning will vaporize (literally) your battery cables. POOF!
The only thing that MAY help you is to always anchor with boats that
have much
taller masts than yours.

How about a heavy wire connecting keel bolts to mast bolts, less than a
foot apart in my bilge?

Stephen

The problem is that a lightening strike is a pulse - it is not DC.
Corners in the wire path look like inductors at high frequencies, and
may force the lightening to leave the conductor and take a straighter
path (at least in its mind) to earth, avoiding the conductor altogether.
All wiring paths should be very heavy gauge, and as straight as
possible.

It might work.

It might not, but one always takes the precautions, right?

bob
s/v Eolian
Seattle, where a lightening bolt becomes the first item on the evening
news...

Having worked with seriously high voltage discharges, I am a little
familiar with this topic and even more fearful of lightning than the
average sailor. So, I have a 15' length of #00 guage insulated TINNED
battery cable of MANY strands (not the normal heavy strands but many
smaller strands) to give max surface area. Water end is soldered to a
heavy lug on a thin 2.5'X2.5' piece of copper sheet. Other end is
bared and soldered to avoid corrosion on the copper. On the mast I
have a heavy clamp type lug bolted to the mast (mast is deck stepped)
about 4' above deck to minimize the bend in going over the side. The
bare soldered end is placed into the clamp connector and it is clamped
down and the copper sheet is thrown over the side.
If struck, most of the discharge will go through the most direct path,
down the mast and into the cable. I expect to get some arcing off the
shrouds at the bottom but I think they will survive.
I think this is the best I can do. Having been very close to being
struck several times even though I was taking precautions, I am very
afraid of lightning.
A couple years ago, I did a calculation of the probability of a
Florida sailor getting his boat hit if he routinely stayed out in
thunderstorms and was amazed at how high it was. This was based on the
projected area of the mast, number of strikes/yr/km2, etc. I argued
back and forth over this with someone from up north on here and
eventually found insurance company stats that agreed with mine.