On Sat, 08 Nov 2008 16:33:21 -0500, Marty wrote:

Roger Long wrote:
This winter's major project is to add some serious lightning protection
to "Strider". What I have now is probably sufficient to increase the
odds of being alive to climb into the dinghy and watch the boat sink but
I'd prefer to sail home. It's not a subject that comes up often for a
designer of metal vessels so I've been look around the web and learned:

Do it like is done for tall buildings, strap a copper ribbon, 8" x 1/4"
up the length of your mast, one on each side. bond these at the base of
the mast to copper bus, 8" x 1/2", this bus is then bonded to a braided
copper cable approximately 6" in diameter and led to copper grid.
The grid should consist of an array of 1/2" diameter rod laid out to
form a square of no less 100' on each side, or any configuration giving
you an area of 10,000 sq. ft. The rods should be configured to form
squares of about one foot on each side, each junction should be bonded.
The main cable should be laid across at least 3/4 of the grid, or the
braid unraveled and broken into many smaller strands, each strand to be
bonded to the grid at intervals of two to five feet.

This will probably, but is not guaranteed to, protect your boat,
remember a lighting strike may exceed a million amperes, for a brief
time, but it does have a tendency of vaporizing anything smaller than I
have described.

Sounds like BS. My house barn and corn crib all had half inch or so
braided copper cable connecting 1/2 inch pointed rods. The ground rods
are presumed to be the standard ones the electrical places all sell.
They were struck hundreds of times, they were on top of a hill.

I heard it was 20 000 amps, at a million volts.

Casady

Richard Casady wrote:


Sounds like BS. My house barn and corn crib all had half inch or so
braided copper cable connecting 1/2 inch pointed rods. The ground rods
are presumed to be the standard ones the electrical places all sell.
They were struck hundreds of times, they were on top of a hill.

I heard it was 20 000 amps, at a million volts.


Guess I should have included a tongue and a cheek,,,

However my point was rather that lightening is inherently unpredictable.
Our barn is "protected" the same as yours, still has the cool glass
globes at the base of the pointed rods, what the hell they are supposed
to do I don't know. As far as I know it's never been hit. I've seen a
neighbor's lightening system vaporized, fortunately it was raining hard
enough, and his roof was leaky enough that damage was limited to a some
singed hay and a couple of scorched boards.

I've been involved with ground protection systems for airports,
(counterpoises in the trade) and seen some absolutely whacky things,
like edge lighting halogen bulbs blown up, even though the feeder was
buried three feet below a 4 gauge bare copper ground wire just a few
inches below ground..... I've seen constant current power supplies that
feed the lighting fried but the lighting fixtures and transformers
remain unharmed.... lighting is funny stuff..

Cheers
Martin

On Sat, 08 Nov 2008 23:35:13 -0500, Marty wrote:

Richard Casady wrote:


Sounds like BS. My house barn and corn crib all had half inch or so
braided copper cable connecting 1/2 inch pointed rods. The ground rods
are presumed to be the standard ones the electrical places all sell.
They were struck hundreds of times, they were on top of a hill.

I heard it was 20 000 amps, at a million volts.


Guess I should have included a tongue and a cheek,,,

However my point was rather that lightening is inherently unpredictable.
Our barn is "protected" the same as yours, still has the cool glass
globes at the base of the pointed rods, what the hell they are supposed
to do I don't know. As far as I know it's never been hit. I've seen a
neighbor's lightening system vaporized, fortunately it was raining hard
enough, and his roof was leaky enough that damage was limited to a some
singed hay and a couple of scorched boards.

I've been involved with ground protection systems for airports,
(counterpoises in the trade) and seen some absolutely whacky things,
like edge lighting halogen bulbs blown up, even though the feeder was
buried three feet below a 4 gauge bare copper ground wire just a few
inches below ground..... I've seen constant current power supplies that
feed the lighting fried but the lighting fixtures and transformers
remain unharmed.... lighting is funny stuff..

Pretty much my take based on fairly extensive reading.
Think I came to the conclusion that:
Bonding can pretty much provide a safe area so long as you keep you
hands off metal.
An electrical disconnect that won't likely be jumped might be worth
exploring to cut down the expense of damaged electronics.
Basically like pulling the plugs in the house, which I usually do
during electrical storms.
Keep some portable radio/gps gear in an insulated container.
Since you might get holed, have a good collection of damage control
plugs.
Dry weather lightning can still catch you off-guard.

--Vic

On Sat, 08 Nov 2008 22:49:50 -0600, Vic Smith
wrote:

Keep some portable radio/gps gear in an insulated container.

What you want is a completely closed metal container. The charge will
stay in the walls of the container. They call this a Faraday Cage.

Casady

On Sun, 09 Nov 2008 00:37:38 GMT, (Richard
Casady) wrote:

On Sat, 08 Nov 2008 16:33:21 -0500, Marty wrote:

Roger Long wrote:
This winter's major project is to add some serious lightning protection
to "Strider". What I have now is probably sufficient to increase the
odds of being alive to climb into the dinghy and watch the boat sink but
I'd prefer to sail home. It's not a subject that comes up often for a
designer of metal vessels so I've been look around the web and learned:

Do it like is done for tall buildings, strap a copper ribbon, 8" x 1/4"
up the length of your mast, one on each side. bond these at the base of
the mast to copper bus, 8" x 1/2", this bus is then bonded to a braided
copper cable approximately 6" in diameter and led to copper grid.
The grid should consist of an array of 1/2" diameter rod laid out to
form a square of no less 100' on each side, or any configuration giving
you an area of 10,000 sq. ft. The rods should be configured to form
squares of about one foot on each side, each junction should be bonded.
The main cable should be laid across at least 3/4 of the grid, or the
braid unraveled and broken into many smaller strands, each strand to be
bonded to the grid at intervals of two to five feet.

This will probably, but is not guaranteed to, protect your boat,
remember a lighting strike may exceed a million amperes, for a brief
time, but it does have a tendency of vaporizing anything smaller than I
have described.

Sounds like BS. My house barn and corn crib all had half inch or so
braided copper cable connecting 1/2 inch pointed rods. The ground rods
are presumed to be the standard ones the electrical places all sell.
They were struck hundreds of times, they were on top of a hill.

I heard it was 20 000 amps, at a million volts.

Casady

Does your barn have a 60 foot metal mast sticking up, supported by
multiple metal cables running down to various attachment points? Is it
floating on water, with no other tall objects around? How bi, and what
is the mass of the "earth" to which it is bonded?

The two situations are really not comparable.

Protecting a sailboat from lightning strikes is pretty much a fools
errand. Unless you have witnessed lightning strikes up close and
personal, you have no idea of the forces involved. It beats any
"fantasy explosions" or other special effects mayhem you have ever
seen in the movies.

A 1/2 inch copper wire would vaporize before it could carry the strike
anywhere. You aren't going to steer a lightning bolt, either. It has
no brains and will often jump a long distance, even if already
following what seems to be a path.

The best thing you can do for lightning protection on a sailboat is
anchor near other boats with taller masts than yours, and THAT is also
foolishness and completely useless. It's only benefit is a little
humor.

wrote in message
...
Protecting a sailboat from lightning strikes is pretty much a fools
errand. Unless you have witnessed lightning strikes up close and
personal, you have no idea of the forces involved. It beats any
"fantasy explosions" or other special effects mayhem you have ever
seen in the movies.

A 1/2 inch copper wire would vaporize before it could carry the strike
anywhere. You aren't going to steer a lightning bolt, either. It has
no brains and will often jump a long distance, even if already
following what seems to be a path.

The best thing you can do for lightning protection on a sailboat is
anchor near other boats with taller masts than yours, and THAT is also
foolishness and completely useless. It's only benefit is a little
humor.

Some years ago I was caught in a lightning storm while well offshore. My
boat had a metal mast with a pointy VHF aerial on top.
The mast was keel stepped, but the step seemed to be just glassed into the
hull and I could see no sign that it was bonded to the lead keel.
Lightning bolts were hitting the water so close to us that I could
distinctly hear the sizzling noise of water boiling and this happened
several times.
Despite the fact that my mast was the only thing sticking up above sea level
in the vicinity we were not struck although it was a very frightening
experience.
I am afraid that this does not assist in deciding whether earthing the mast
is a good idea or not..

wrote:

Protecting a sailboat from lightning strikes is pretty much a fools
errand.

This document, which Larry provided the link to, contriticts you with actual
facts by researchers.

http://www.thomson.ece.ufl.edu/lightning/

See damage distribution graphs. There will usually be some damage and some
strikes will overwhelm any system. However, saying protection is pointless
is like saying it's a fools errand to wear seatbelts because some car
crashes will be fatal anyway.

Everything on the water is about odds. Stack the deck in your favor when
you can.

--
Roger Long

On Sun, 9 Nov 2008 08:48:03 -0500, "Roger Long"
wrote:

wrote:

Protecting a sailboat from lightning strikes is pretty much a fools
errand.

This document, which Larry provided the link to, contriticts you with actual
facts by researchers.

http://www.thomson.ece.ufl.edu/lightning/

See damage distribution graphs. There will usually be some damage and some
strikes will overwhelm any system. However, saying protection is pointless
is like saying it's a fools errand to wear seatbelts because some car
crashes will be fatal anyway.

Everything on the water is about odds. Stack the deck in your favor when
you can.

You seem hell-bent on installing a protection system, and I understand
the feeling. "Because I can." "Reach for the stars." "Dream the
impossible dream." (-:
Go for it.
Whenever the discussion comes up, I'm hoping for new data.
The Thomson stuff is old, and I don't see where he had convincing
data to come to a conclusion. I wish the boat insurance industry
would do some work on their data.
Are there insurance premium discounts for lightning protection systems
on boats?
I found the Sea Grant pamphlet link provided on the above the most
useful piece on lightning and boats that I've seen.
The algebra-laced IEEE paper sorely tests my attention span, but Larry
probably eats it up.

--Vic

On Sun, 9 Nov 2008 08:48:03 -0500, "Roger Long"
wrote:

wrote:

Protecting a sailboat from lightning strikes is pretty much a fools
errand.

This document, which Larry provided the link to, contriticts you with actual
facts by researchers.

http://www.thomson.ece.ufl.edu/lightning/

See damage distribution graphs. There will usually be some damage and some
strikes will overwhelm any system. However, saying protection is pointless
is like saying it's a fools errand to wear seatbelts because some car
crashes will be fatal anyway.

Everything on the water is about odds. Stack the deck in your favor when
you can.

Do you wear a nomex suit and crash helmet when driving a car. Does
your car have a fire suppression system? Those would be a LOT more
important to your safety than anything you can do to protect a
sailboat from lightning.

By the time you equipped your boat with what would be needed to
protect you in SOME lightning hits, it would no longer be useable as a
sailboat. Those huge copper fields you would have to drag around would
really slow you down...

Getting hit in the head by the boom is a much greater threat, anyway,
if you want to go by statistics.

Simply falling overboard has a very high mortality rate.

Lightning protection on a sailboat is a fools errand.

On Sun, 09 Nov 2008 07:58:04 -0500, wrote:

The best thing you can do for lightning protection on a sailboat is
anchor near other boats with taller masts than yours, and THAT is also
foolishness and completely useless. It's only benefit is a little
humor.

Depends on the size of the boat, but hiding under a steel bridge might
work. I once hid my truck from golf ball size hail, under a bridge.
Talk about a piece of luck. I had stopped because the rain was too
heavy to see the road

The best thing for lightning is probably a metal mast bonded to a
metal hull. Guys used to go out in wood boats with wood oars for
power, and the target of choice would be a head. Smart targets would
lie down.

Casady