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.

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

Roger,

If lightning hits your mast, your battery cables
and chains are not going to help much, although
they probably won't hurt either. I've got the
electrical engineering degree with a bunch of
experience to back it up, but lightning protection
is a specialized black art--even in my field.

There are some pretty good explanations on the web
by PHd's who have made lightning protection their
whole career. Search them out and give them a
read. It's an interesting subject.

Good luck,

Don W -- who is still scratching his head about
what to do about lightning protection for his
Irwin 38.

Roger Long wrote:


I'm not talking about doing it right here or protecting the boat. The only
aim is to increase the chances of remaining alive on a possibly wrecked boat
to deal with the aftermath. I'm just looking for a quick stop gap to at
least do something until I can put in a proper system. It's tough on a boat
with ballast encapsulated inside a fiberglass keel.

You've just figured out another important design
criterion for a sailboat--proper grounding for
lightning protection. It needs to be done as part
of the design, instead of as an afterthought.

Regarding your aim of increasing your chances of
remaining alive, I'm not sure if you are talking
about surviving the strike itself, or possibly a
sinking caused by the strike.

Don W.

Charlie Morgan wrote:

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!

A keel stepped mast with large solid aluminum bar
ties to the non-encapsulated lead keel is about as
good as it gets. It's also supposedly a good idea
to ground your chainplates with large wire down to
the keel.

What is controversial is whether the good
grounding scheme actually increases your chances
of taking a strike.

The ABYC has standards for lightning protection
for sailboats IIRC.


The only thing that MAY help you is to always anchor with boats that have much
taller masts than yours.

This is controversial also, as its not always the
tallest point that gets struck.

Don W.

Wayne.B wrote:

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


That's about as good as it gets, better to use heavy copper braid
however. That also makes an excellent ground for your SSB radio.

You do not want your boat ground or RF ground
connected to your lightning ground unless you wish
to replace all of your electronics in the event of
a strike. The reason is that when the strike
hits, the ground will temporarily pulse to a much
higher voltage than the battery output, reversing
the power inputs and blowing your electronic
equipment.

That is not to say that your electronic equipment
will survive if the grounds are not connected, but
you'll certainly stand a better chance.

Don W.

On Thu, 15 Mar 2007 23:22:43 -0500, Don W
wrote:

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

Roger,

If lightning hits your mast, your battery cables
and chains are not going to help much, although
they probably won't hurt either. I've got the
electrical engineering degree with a bunch of
experience to back it up, but lightning protection
is a specialized black art--even in my field.

There are some pretty good explanations on the web
by PHd's who have made lightning protection their
whole career. Search them out and give them a
read. It's an interesting subject.

Good luck,

Don W -- who is still scratching his head about
what to do about lightning protection for his
Irwin 38.

FWIW,
I took a hit from lightning whilast at anchor in Langkawi, Malaysia.
My 42 footer is strip planked and sheathed with GRP.
The path of the lightning which melted the VHF atnenna and tricolour
at the masthead was down the twin backstays. Both the large ceramic
insulators on the one used as an aerial blew to pieces. Later, we
recorded a smell of antifouling. It appears that one backstay (not the
aerial one) internal chainplate bolt was touching a large tin of
antifouling as well as one of the bolts for the drop down ss ladder
which was in the water. A small hole was blown in the side of the can.

Every connected electronic item and all instruments were blown. The
computers were fine.

Now I am deminically paranoid about lightning. I race around and pull
out all plugs, wires, aerials and power cables. It was a real pain
with the 13 to the Raytheon autopilot but I fed all to a single plug
which goes back like a breeze. Yes, I've heard of electromagnetic
induction. I throw everything that fits into my stainless oven.

It feels good to be sailing along with just the compass but have
learned to take note of the heading first.

Did secure a large cable and chain to one capshroud but the bumping
along the hull was too annoying. I like the idea of traing one from a
backstay however.

Seem to recall hearing somewhere that chain is not good as a
conductor. - any ideas please. It is rather scary being the tallest
thing for miles of ocean when you see lightning ahead. This thread is
of intense interest.

cheers
Peter Hendra

It sounds like I was on the right track,

How important is a really low resistance connection? I have a spinnaker
track and fitting at about the right height. Is a special fitting really
necessary at these high voltages or would a large snap shackle in the ring
do with the cable passed around the mast a couple times first? (Insulation
removed over the last couple feet).

Similar question about chain which would be much easier to stow than a big
sheet of copper. Lots of surface area and, with salt water helping to carry
current from link to link is seems like it would work. Wouldn't the solder
on the copper sheet vaporize in the first milisecond?

It sounds like nothing is going to do anything but tip the odds slightly in
your favor. I don't have a big investment in electronices. My only aim is
to be alive in something floating after a strike, even with major damage.

--
Roger Long

On Fri, 16 Mar 2007 23:06:00 -0400, Wayne.B
wrote:

On Fri, 16 Mar 2007 22:22:25 +1100, Peter Hendra
wrote:

It is rather scary being the tallest
thing for miles of ocean when you see lightning ahead.

You bet. Lightning is fickle however. We were halfway to Bermuda
once, over 300 miles offshore when we got hit with a ferocious thunder
squall. The boat was a perfect target, all aluminum hull with an 85
ft mast. Lightning chose to hit a wavetop about 100 yards away
instead of us. We still lost all of the electronics except my pocket
GPS, just from induced currents. The pocket GPS was an early model
and hasn't worked in years now, but I still keep it around for
sentimental reasons. :-)

As it is so fickle, I've often thought of sacrificing a chicken to
Poseidon. Once, not having a real live chicken, I threw a tin of
chicken spam overboard. It was rusty and looked unsafe for us to eat
but the God didn't appear to notice it as the lightning didn't touch
us. Anyone know what Poseidon prefers?

Don W wrote:



Roger Long wrote:


I'm not talking about doing it right here or protecting the boat. The
only aim is to increase the chances of remaining alive on a possibly
wrecked boat to deal with the aftermath. I'm just looking for a quick
stop gap to at least do something until I can put in a proper system.
It's tough on a boat with ballast encapsulated inside a fiberglass keel.


You've just figured out another important design criterion for a
sailboat--proper grounding for lightning protection. It needs to be
done as part of the design, instead of as an afterthought.

Regarding your aim of increasing your chances of remaining alive, I'm
not sure if you are talking about surviving the strike itself, or
possibly a sinking caused by the strike.

Don W.

Well, if he don't survive the strike, he probably won't survive the
sinking, either.

DT

On Mar 16, 9:58 am, dt wrote:
Don W wrote:

Roger Long wrote:

I'm not talking about doing it right here or protecting the boat. The
only aim is to increase the chances of remaining alive on a possibly
wrecked boat to deal with the aftermath. I'm just looking for a quick
stop gap to at least do something until I can put in a proper system.
It's tough on a boat with ballast encapsulated inside a fiberglass keel.

You've just figured out another important design criterion for a
sailboat--proper grounding for lightning protection. It needs to be
done as part of the design, instead of as an afterthought.

Regarding your aim of increasing your chances of remaining alive, I'm
not sure if you are talking about surviving the strike itself, or
possibly a sinking caused by the strike.

Don W.

Well, if he don't survive the strike, he probably won't survive the
sinking, either.

DT


A millisecond is a long time for lightning so the solder will probably
melt but will last long enough to conduct the pulse. The connection
is also crimped.
Many boats do get hit and survive and I'd go so far at to say that
most survive. You have to remember that at 10,000,000 volts, almost
everything looks like a conductor but some are better than others.
This means that a wet hull and deck look like perfectly good
conductors to the lightning. I have considered connecting the chain
plates together and then to the bolts at the mast step (deck stepped
mast) to try to make current that goes into the shrouds go back into
the grounded cable connected to the mast but this would make a huge
loop so am hesitant to do it.
I went so far as to use my dremel tool to round all edges on the chain
plates to suppress corona discharge from the edges.
You want to get that current to ground and do it with a large surface
area conductor which is why I use the many stranded wire. The
grounded plate has a lot of surface area too.
I think that the reason most struck boats survive is that the current
travels over the wet deck and hull surface which has huge surface
area. I have read that discharge pattersn are common on the outside
of struck boats , like Lichtenberg figures. My strategy is to
minimize this damage.