Lightning Protection questions
 

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:

The ABYS standards of 1 sq. foot of ground area and 8 GA conductors are
marginal and highly suspect.

Probably nothing feasible is going to protect a plastic boat in fresh water.
Although I'm generally in salt, I'd like to be ready to go up some rivers.

Conductors should have a minimum 8" radius bend.

I've got a metal mast support strut that has sufficient through bolts to the
mast deck step to make it electrically continuous. This lands on a wide,
internal ballast keel. I plan to run flat copper straps about 1/16" x 1/2"
(approximate cross section of 4 ga wire) from this up each side to 6" x 24"
bronze ground plates on each side of the hull. These will be about 1/16"
thick and through bolted to the hull at each corner. Inside, there will be
straps under the bolt heads in an "X" pattern with the strap from the mast
strut lead to the center. There will also be a 4 Ga wire or strap from the
engine block to one of these plates to help protect the engine bearings.

Comments welcome on this conceptual plan which will also include other
secondary bonding additions as recommended by ABYC.

Here's my main question for someone who understands high voltage better than
I do:

I only have 6" under the cabin sole. How critical is the 8" bend? Can I
compensate for the tighter radius by increasing the conductor cross section?
How much? The turn is more than 90 degrees because the straps have to run
back up the hull deadrise about two feet to where I can locate the plates
and through bolts. I don't think putting the plates on the keel sides is
feasible.

Another question:

Is the standard metal rod VHF antenna at the top of the mast with the
typical metal can on a bracket riveted to the mast a sufficient air terminal
or should I add a dedicated rod?

I have no illusions about having any electronics working after a strike on a
32 foot boat but replacement of my minimalist outfit wouldn't break me
financially. I'd just like to be alive with a working engine and watertight
boat.

--
Roger Long

Lightning Protection questions
 

On Sat, 8 Nov 2008 12:40:47 -0500, "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:

The ABYS standards of 1 sq. foot of ground area and 8 GA conductors are
marginal and highly suspect.

Probably nothing feasible is going to protect a plastic boat in fresh water.
Although I'm generally in salt, I'd like to be ready to go up some rivers.

Conductors should have a minimum 8" radius bend.

I've got a metal mast support strut that has sufficient through bolts to the
mast deck step to make it electrically continuous. This lands on a wide,
internal ballast keel. I plan to run flat copper straps about 1/16" x 1/2"
(approximate cross section of 4 ga wire) from this up each side to 6" x 24"
bronze ground plates on each side of the hull. These will be about 1/16"
thick and through bolted to the hull at each corner. Inside, there will be
straps under the bolt heads in an "X" pattern with the strap from the mast
strut lead to the center. There will also be a 4 Ga wire or strap from the
engine block to one of these plates to help protect the engine bearings.

Comments welcome on this conceptual plan which will also include other
secondary bonding additions as recommended by ABYC.

Here's my main question for someone who understands high voltage better than
I do:

I only have 6" under the cabin sole. How critical is the 8" bend? Can I
compensate for the tighter radius by increasing the conductor cross section?
How much? The turn is more than 90 degrees because the straps have to run
back up the hull deadrise about two feet to where I can locate the plates
and through bolts. I don't think putting the plates on the keel sides is
feasible.

Another question:

Is the standard metal rod VHF antenna at the top of the mast with the
typical metal can on a bracket riveted to the mast a sufficient air terminal
or should I add a dedicated rod?

I have no illusions about having any electronics working after a strike on a
32 foot boat but replacement of my minimalist outfit wouldn't break me
financially. I'd just like to be alive with a working engine and watertight
boat.

I know of at least half a dozen sailboats that have been hit, one of
them twice on the same day. Only one sank and that was because the
lightning decided to exit through a plastic knot meter impeller
leaving a 1 inch hole in the bottom. It could have been plugged if
there had been anyone on board at the time.

What you are planning sounds like overkill to me, especially for
Maine. Where we live now there are thunderstorms almost everyday
throughout the summer but you don't hear about that many hits on
boats. Golfers seem to be the target of choice and they usually
fare poorly.

Lightning Protection questions
 

"Wayne.B" wrote

What you are planning sounds like overkill to me, especially for Maine.

That's what I would have said (and did) earlier this year. However, I hear
of more strikes as I get around more. One was my slip neighbor before I was
docked there.

I'm also thinking of some fresh water tripsafter my recent Hudson experience
and would like to take the boat south for at least one winter. It's one of
those things where a little more isn't incrementally a lot of work once
you're set up to do the minimum. If I semi enjoy just one rip snorting
boomber instead of quaking in the forward V-berth, it will be worth it.

Besides, didn't we decide last year that "overkill" was my middle name? :)

--
Roger Long

Lightning Protection questions
 

Roger,

Talk to these people:
http://www.lightningtech.com/intro.html

They are the authority on this subject.

Joe

Lightning Protection questions
 

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.

Cheers
Martin

Lightning Protection questions
 

"Roger Long" wrote in message
...
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:

The ABYS standards of 1 sq. foot of ground area and 8 GA conductors are
marginal and highly suspect.

Probably nothing feasible is going to protect a plastic boat in fresh
water. Although I'm generally in salt, I'd like to be ready to go up some
rivers.

Conductors should have a minimum 8" radius bend.

I've got a metal mast support strut that has sufficient through bolts to
the mast deck step to make it electrically continuous. This lands on a
wide, internal ballast keel. I plan to run flat copper straps about 1/16"
x 1/2" (approximate cross section of 4 ga wire) from this up each side to
6" x 24" bronze ground plates on each side of the hull. These will be
about 1/16" thick and through bolted to the hull at each corner. Inside,
there will be straps under the bolt heads in an "X" pattern with the strap
from the mast strut lead to the center. There will also be a 4 Ga wire
or strap from the engine block to one of these plates to help protect the
engine bearings.

Comments welcome on this conceptual plan which will also include other
secondary bonding additions as recommended by ABYC.

Here's my main question for someone who understands high voltage better
than I do:

I only have 6" under the cabin sole. How critical is the 8" bend? Can I
compensate for the tighter radius by increasing the conductor cross
section? How much? The turn is more than 90 degrees because the straps
have to run back up the hull deadrise about two feet to where I can locate
the plates and through bolts. I don't think putting the plates on the
keel sides is feasible.

Another question:

Is the standard metal rod VHF antenna at the top of the mast with the
typical metal can on a bracket riveted to the mast a sufficient air
terminal or should I add a dedicated rod?

I have no illusions about having any electronics working after a strike on
a 32 foot boat but replacement of my minimalist outfit wouldn't break me
financially. I'd just like to be alive with a working engine and
watertight boat.


To understand lightning you've got to understand why it strikes. You need to
"see" the world how lightning sees the world.

You get an unbalanced electrical charge between the clouds and the water.
Like all current, lightning takes the path of least resistance. This may or
may not have anything to do with height of mast. Height of mast and material
of mast and grounding of mast all have little to do with how lightning
"sees" the best path to ground.

The purpose of all the bonding and grounding is to bleed off charge slowly
before it builds up to a great enough extent to arc from above the boat. A
properly grounded GRP sailboat will be seen by lightning potential directly
over it as sitting in a valley. One not grounded at all will be seen as
sitting atop a hill. Again, it's not distance I'm talking about but
resistance in the path to ground. An ungrounded boat does not bleed off
potential. It spikes it up.

The trouble with grounding your boat properly is the slow bleeding off of
the charge imbalance can actually, in some cases, prepare a lower resistance
path to ground as charge is already moving that way. While it may thwart
lightning strikes from directly above, should lightning strike at a 45
degree angle, for example, it may well strike a well-grounded boat and not
strike an ungrounded boat anchored several boat lengths away.

But, a properly grounded boat will suffer less damage as the voltage will
not build up as much because the current (amperage) will flow easier to
ground. An ungrounded boat, though less likely to be "seen" by lightning
will, if struck, suffer more damage because the voltage will build higher
and the resultant amperage will also be higher.

My boat is totally ungrounded and in over 25 years has been struck only
once. I was aboard and all kinds of bad stuff happened. There was a zzzzzzt
and a huge crash simultaneously. Then a series of gun shots as ball
lightning went arching and dancing around everywhere inside. I was forward
lying in the v-berth. One ear on the pillow and the other up. It was
temporarily deafened for a couple days in the upper ear and had extensive
ringing but the hearing came back. I think I was knocked unconscious for a
couple of minutes. My hair smelled burnt.

Every wired electronic device but one GPS was cooked. Solar panels were
fried from the inside out. The wiring harness was cooked. All the lights
burned out. A charred hole the size of a walnut was blasted out of the GRP
ceiling where the cabin light wires were encapsulated. The backstay where it
split was burned in two on the port side where current arched from it to the
outboard motor the foot of which was in the water acting as a ground. The
current jumped from the backstay to the tiller handle and cooked the wiring
and throttle cable - burned them to a crisp. The plastic fuel tank had black
marks on it but wasn't burned through. The ignition was not ruined, however,
probably because most of it is under the metal flywheel. The base-loaded VHF
antenna at the mast head was an empty shell. The mast wiring inside was all
cooked. The depth sounder transponder was fried. Bottom paint was blasted
off the outside of two of the bronze thru hulls. The keel bolts above the
GRP floors were blackened. The boat was full of smoke. A bottle of brandy in
the undersink galley locker had burst and was burning in the bilge. The
Adler Barbour fried. The secretary at a nearby marina saw the strike. She
said is was very large and lasted seconds hitting again and again.

It cost over 4,000 dollars not counting my labor time to repair it all.
However the good news is the cast iron keel took the brunt of it with paint
and epoxy coating blasted off in several fist-sized places. The hull at the
water line took no damage. No leaks as a result. No hull damage. There was
some deck damage at the foot of the mast were the current actually passed
through to get to the wood enclosed steel post that supports the deck
stepped mast foot and then to the keel bolts.

The choices as I see them are these:

a) Bond and ground your boat well and be prepared to be hit more often but
with less damage.

b) Don't bond and ground and your boat will be struck less often but with
more damage.


b) has been and will continue to be my choice as proper grounding and
bonding can only really be done during the construction process. Once a boat
is built too much stuff has to be torn out to do the job right.


Wilbur Hubbard

Lightning Protection questions
 

On Sat, 8 Nov 2008 12:40:47 -0500, "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:

The ABYS standards of 1 sq. foot of ground area and 8 GA conductors are
marginal and highly suspect.

Probably nothing feasible is going to protect a plastic boat in fresh water.
Although I'm generally in salt, I'd like to be ready to go up some rivers.

Conductors should have a minimum 8" radius bend.

I've got a metal mast support strut that has sufficient through bolts to the
mast deck step to make it electrically continuous. This lands on a wide,
internal ballast keel. I plan to run flat copper straps about 1/16" x 1/2"
(approximate cross section of 4 ga wire) from this up each side to 6" x 24"
bronze ground plates on each side of the hull. These will be about 1/16"
thick and through bolted to the hull at each corner. Inside, there will be
straps under the bolt heads in an "X" pattern with the strap from the mast
strut lead to the center. There will also be a 4 Ga wire or strap from the
engine block to one of these plates to help protect the engine bearings.

Comments welcome on this conceptual plan which will also include other
secondary bonding additions as recommended by ABYC.

Here's my main question for someone who understands high voltage better than
I do:

I only have 6" under the cabin sole. How critical is the 8" bend? Can I
compensate for the tighter radius by increasing the conductor cross section?
How much? The turn is more than 90 degrees because the straps have to run
back up the hull deadrise about two feet to where I can locate the plates
and through bolts. I don't think putting the plates on the keel sides is
feasible.

Another question:

Is the standard metal rod VHF antenna at the top of the mast with the
typical metal can on a bracket riveted to the mast a sufficient air terminal
or should I add a dedicated rod?

I have no illusions about having any electronics working after a strike on a
32 foot boat but replacement of my minimalist outfit wouldn't break me
financially. I'd just like to be alive with a working engine and watertight
boat.

Wear a tin-foil hat if it stops you worrying..
http://www.google.co.uk/search?sourc...ng+cosmic+rays

Lightning Protection questions
 

On Sat, 8 Nov 2008 12:40:47 -0500, "Roger Long"
wrote:

I'd just like to be alive with a working engine and watertight
boat.

The wise Craptain Neal filled his boat with empty bottles and
inflatable dolls so that it was unsinkable.(like the Titanic)

Lightning Protection questions
 

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

Lightning Protection questions
 

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