Lightning Protection questions
 

"Marty" wrote in message
...
Capt. JG wrote:
"IanM" wrote in message
...
Roger Long wrote:

I don't know why my first Google search missed this site:

http://www.marinelightning.com/

but it calls into question the whole idea of the central main
conductor.

I'm fortunate in having one of those aluminum toe rails that go bow to
stern on each side. It seems that I might be better off running the
heaviest wire I can between the port and starboard toe rails inside at
bow and stern and then bonding each chainplate to the toe rail and
running 4 ga conductors to each piece of underwater metal I can. I
have a number of unused through hulls that are capped. The
chainplates on my boat all end very close to the toe rail so charge
coming down the stays would likely jump that way even without bonding.

As I said earlier, If you let the lighting get below deck, you are
screwed and if down to bilge level ****ed unless its got somewhere to
go. For a powerboat or a sailboat with a non-conductive mast support
post, its probably practical to *NOT* have a central lightning
conductor, but where do you think the bulk of the lightning current is
going to go? Down a nice thick piece of low resistance aluminium bolted
inline to a heavy fairly low resistance steel pipe leading to the bilge
or down fairly high resistance shrouds and stays with rather dodgy
electrical contact at the top and bottom ends?

There is going to be *some* current down the stays so it would appear
prudent to bond the toerail to the shrouds, stays and mast foot, and
cross bond bow and stern, but then the problem is where do you encourage
the inevitable flashover from the toerail to the water surface to go? A
strap down the stem and each transom corner would be a good start but
few owners are going to tolerate external straps down from the
chainplates. I suppose you could trail a chain from each shroud while
berthed and if caught out in a thunderstorm.


From my manual:
22:00 LIGHTENING PROTECTION AND BONDING SYSTEMS

All Sabre yachts are equipped with a heavy duty lightening ground and
bonding system connecting all essential equipment to the keel using #8
gauge stranded copper wire.

22:01 BONDING SYSTEM: The bonding system provides low resistance to
electrical connections of all underwater fittings, fuel fill, fuel tank
and engine to the keel. This keeps all fittings at the same electrical
potential to minimize the effects of any galvanic or electrical corrosion
which may occur.

Any additional underwater hardware installed on the boat must be tied in
to the bonding system to maintain proper operation and protection from
corrosion.

The integrity and operation of the system should be checked each year at
launching and hauling times.

Refer to the lightening protection and bonding system diagrams in the
back of the Owners Manual for the wiring details of your boat.

22:02 LIGHTENING PROTECTION SYSTEM: The lightening protection system
provides a "cone" of protection around the boat in the even of a
lightening storm. Grounding wires of #8 gauge copper connect all chain
plates and the mast step to the keel.


#8? Ha, Jon, I've seen the inside of an underground vault with the walls
spattered with copper after a 75KA short vaporized copper bus bars 1/2'"
thick by 4" wide. That's one hell of lot of #8 wires in parallel. Imagine
what happens with surge that may exceed 200KA?

I go along with others that have suggested that lightning protection for a
plastic boat is probably an exercise in futility.

Cheers
Martin


No doubt. Sabre seems to think it'd be acceptable protection. I think I
don't want to find out.


--
"j" ganz @@
www.sailnow.com

Lightning Protection questions
 

IanM wrote:
Marty wrote:

Capt. JG wrote:

22:02 LIGHTENING PROTECTION SYSTEM: The lightening protection
system provides a "cone" of protection around the boat in the even of
a lightening storm. Grounding wires of #8 gauge copper connect all
chain plates and the mast step to the keel.



#8? Ha, Jon, I've seen the inside of an underground vault with the
walls spattered with copper after a 75KA short vaporized copper bus
bars 1/2'" thick by 4" wide. That's one hell of lot of #8 wires in
parallel. Imagine what happens with surge that may exceed 200KA?

I go along with others that have suggested that lightning protection
for a plastic boat is probably an exercise in futility.

Cheers
Martin

#8 is obsolete. #4 grounding wires are now called for. Also I'd lay
odds that the 75KA short lasted for several cycles of your 60Hz mains
before the breakers cleared it. It almost certainly had more than 1000
times the energy that a 100KA 1us lightning strike would dissipate in a
single #8 cable.

Doubtless you are correct, was probably 3 cycles; it's a suprisingly
common problem, circuit was a 600 amp 4.4Kv service, breakers that were
supposed to protect it were rated to break 10,000 amps. Problem was that
the supply was able to feed 75,000 amps, so the primary breakers tried
to trip but fried in the closed position, two cycles later the breakers
on the main feeder tripped. There are other problem with the lightening
strike, to start with duration is likely more than 1us, probably also
more than one stroke, usual pattern is several cycles, further 100KA is
likely a low estimate, some run higher than 500KA. Then just to
compound things, we're are talking voltages into the hundreds of
millions, and then we are generating plasmas, there are strange
electromagnetic effects, none of which are well understood or tractable
to simple modeling. Energy would be from 10 to 100 billion joules!
Your #4 is going to be toast. You need a cable thick as your arm to
guarantee that the cable wont fry, but with the other weird effects,
there is little guarantee that all of the energy will remain confined to
the path you are providing.

Cheers
Martin

If the protection system can prevent serious structural damage from 9
strikes out of 10 its obviously worth doing. If it reduces damage 50%
of the time so you dont have to abandon ship in the middle of a storm
its still worth doing if the cost is comparable to that of a liferaft.

Lightning Protection questions
 

On Mon, 10 Nov 2008 04:03:50 +0000, Larry wrote:

Let's look at the feedpoint of WFAN/WCBS AM stations whos twin 50,000
watt transmitters across the river from NYC share one tower. (The RF
comes out of the building on that copper tubing with the rain loop in
it.)

The WCBS/WFAN transmitters and tower are actually in New York City,
albeit the far north eastern corner, just south of mainland Bronx and
right on the edge of Western Long Island Sound. We moored our first
keel boat a few hundred yards from there after we bought it in 1971.

http://www.hawkins.pair.com/wcbs_wfan.html

Lat 40-51.589 Lon 73-47.126

You can see the tower and guy wires if you zoom way in with Google
Earth. Zoom back out and you can see the small bridge connecting High
Island with the north end of City Island.

Lightning Protection questions
 

Capt. JG wrote:



No doubt. Sabre seems to think it'd be acceptable protection. I think I
don't want to find out.

Sound thinking!

Cheers
Martin

Lightning Protection questions
 

Larry wrote:



I've been involved in tower grounding (just a mast 1200' high with no
sails, if we can help it) for decades in broadcasting. The AM towers
are series fed, meaning they are insulated from ground but have two
trailer hitch balls a few inches apart (far enough so the 5, 10, 25 or
50KW transmitters don't make them arc in the downpouring rainstorms.)
Looking around Jim Hawkins' broadcast transmitter website, you can learn
a lot about lightning grounding from the professionals:
http://www.hawkins.pair.com/radio.html

Thanks for the cool links Larry. The most dangerous job in America is
that held by the tower jockeys.

The impedance thing is the biggest factor, you ever think to calculate
the slew rate of a lightening pulse? Something like 50MV/uSec!

"Resistance is futile, but impedance is rather complex"

Cheers
Martin

Lightning Protection questions
 

Larry wrote:
Wayne.B wrote in
:

On Sat, 8 Nov 2008 14:48:10 -0500, "Roger Long"
wrote:

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.
There are almost no thunderstorms in south Florida from November
through May. We call it the dry season here for good reason.



Yeah, but Florida makes up for it in spades between June and
September....bigtime!

Indeed, there is a reason that one of the world's most prestigious
lightning research facilities is located there! The institution I work
for was thinking of renting some time there to research lightning and
it's effects on various airport grounding schemes, but being Canadian,
we didn't like the idea of summer in Florida....

Cheers
Martin

Lightning Protection questions
 

"Marty" wrote in message
...
Capt. JG wrote:



No doubt. Sabre seems to think it'd be acceptable protection. I think I
don't want to find out.

Sound thinking!

Cheers
Martin



Only after the fact. LOL

--
"j" ganz @@
www.sailnow.com

Lightning Protection questions
 

On Sun, 9 Nov 2008 20:17:04 -0800, "Capt. JG"
wrote:

"Marty" wrote in message
m...
Capt. JG wrote:
"IanM" wrote in message
...
Roger Long wrote:

I don't know why my first Google search missed this site:

http://www.marinelightning.com/

but it calls into question the whole idea of the central main
conductor.

I'm fortunate in having one of those aluminum toe rails that go bow to
stern on each side. It seems that I might be better off running the
heaviest wire I can between the port and starboard toe rails inside at
bow and stern and then bonding each chainplate to the toe rail and
running 4 ga conductors to each piece of underwater metal I can. I
have a number of unused through hulls that are capped. The
chainplates on my boat all end very close to the toe rail so charge
coming down the stays would likely jump that way even without bonding.

As I said earlier, If you let the lighting get below deck, you are
screwed and if down to bilge level ****ed unless its got somewhere to
go. For a powerboat or a sailboat with a non-conductive mast support
post, its probably practical to *NOT* have a central lightning
conductor, but where do you think the bulk of the lightning current is
going to go? Down a nice thick piece of low resistance aluminium bolted
inline to a heavy fairly low resistance steel pipe leading to the bilge
or down fairly high resistance shrouds and stays with rather dodgy
electrical contact at the top and bottom ends?

There is going to be *some* current down the stays so it would appear
prudent to bond the toerail to the shrouds, stays and mast foot, and
cross bond bow and stern, but then the problem is where do you encourage
the inevitable flashover from the toerail to the water surface to go? A
strap down the stem and each transom corner would be a good start but
few owners are going to tolerate external straps down from the
chainplates. I suppose you could trail a chain from each shroud while
berthed and if caught out in a thunderstorm.


From my manual:
22:00 LIGHTENING PROTECTION AND BONDING SYSTEMS

All Sabre yachts are equipped with a heavy duty lightening ground and
bonding system connecting all essential equipment to the keel using #8
gauge stranded copper wire.

22:01 BONDING SYSTEM: The bonding system provides low resistance to
electrical connections of all underwater fittings, fuel fill, fuel tank
and engine to the keel. This keeps all fittings at the same electrical
potential to minimize the effects of any galvanic or electrical corrosion
which may occur.

Any additional underwater hardware installed on the boat must be tied in
to the bonding system to maintain proper operation and protection from
corrosion.

The integrity and operation of the system should be checked each year at
launching and hauling times.

Refer to the lightening protection and bonding system diagrams in the
back of the Owners Manual for the wiring details of your boat.

22:02 LIGHTENING PROTECTION SYSTEM: The lightening protection system
provides a "cone" of protection around the boat in the even of a
lightening storm. Grounding wires of #8 gauge copper connect all chain
plates and the mast step to the keel.


#8? Ha, Jon, I've seen the inside of an underground vault with the walls
spattered with copper after a 75KA short vaporized copper bus bars 1/2'"
thick by 4" wide. That's one hell of lot of #8 wires in parallel. Imagine
what happens with surge that may exceed 200KA?

I go along with others that have suggested that lightning protection for a
plastic boat is probably an exercise in futility.

Cheers
Martin


No doubt. Sabre seems to think it'd be acceptable protection. I think I
don't want to find out.

Did Sabre consult directly with lightning to come to this conclusion?

How did they test the system?

Lightning Protection questions
 

Capt. JG wrote:

No doubt. Sabre seems to think it'd be acceptable protection. I think
I don't want to find out.

Sabre is, or was, simply following what the ABYC Standards said to do. It
was industry standard but now understood to be inadequate.

Don't find out:)

--
Roger Long

Lightning Protection questions
 

Wayne.B wrote:

That's a good point. I certainly wouldn't be in that part of the world any
other time.

However, we get some pretty good storms up here, complete with hail and
tornados. They usually weaken as they reach the coast but it only takes one
strike.

Exposure time is another issue. I plan to spend months at a time on this
boat which raises the risk far above daysailing and weekending when the boat
isn't occupied during severe weather and spends a lot of time in a marina or
mooring field where there are other targets nearby.

--
Roger Long