Lightning Protection questions
 

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.

Lightning Protection questions
 

"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.

The integrity of the lightening ground system should be checked regularly.
Inspect all wire and terminal connections at the mast step, all chainplates
and the keep for tightness and signs of corrosion.

Lightening strikes are unpredictable, so due caution during a storm is
advised.

Allow no one in the water during an electrical storm. Remain inside the
boat and avoid making contact with any large metal objects such as the mast,
shrouds, stanchions, bow pulpit, stern rail or any of the items connects to
the lightening grounding system, especially in such a way as to bridge
between any of these items.

If a boat is struck by lightening, there is likely to be damage to delicate
electronic instruments due to a high voltage-low ampere surge of electricity
through the boat. If a boat is struck by lightening, compasses and
electrical gear must be checked for damage and/or change in calibration.

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

23:03 BONDING AND LIGHTENING GROUND SYSTEM: Check the entire bonding
and lightening ground systems to assure that they are intact and functioning
properly. The purpose of the bonding systems is to protect the underwater
hardware from corrosion by providing a low resistance path to ground for any
stray electrical currents which may develop on the boat. All underwater
hardware is tied together with a wiring system which terminates at one or
two common ground terminals on a keel bolt in the bilge. The integrity and
operation of the bonding system can be checked by using an ohmmeter to
assure that each underwater fitting is bonded to the keel. The ohmmeter
must register "0" resistance for each fitting. The "Lightening Protection
and Bonding System" diagram will help in locating all fittings and hardware
connected to the bonding system. If little or no contact is found between a
fitting and the keel, connections at each end of the wire must be checked
and the wire replaced if necessary. Particular attention should be paid to
the engine to keel bonding conductor. Our experience indicates that a poor
ground connection here can often allow a stray current to leave the boat by
way of the propeller shaft.


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

Lightning Protection questions
 

Last month one of the boats on the hard at the local yacht club got hit
- hard.

It looked like the bolt hit near the _bottom_ of the mast.
(and yes, the mast was up)

So were the masts of thirty other boats around it.

All on trailers, too.

But this one was the one.

Insurance had lapsed the month before.

The resulting fire was so hot that the boat beside this one melted.

I'm guessing that if you took a hit like this, you'd never know it.

--

Richard

(remove the X to email)

Lightning Protection questions
 

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

Lightning Protection questions
 

Roger Long wrote:

Thanks, this is very helpful. I'd planned on the flanges being
arranged so that the nut of the through bolt is sort of in the end of a
box. By extending the flange against the hull and making the top and
bottom edge flanges triangular, I could get in two or more bolts.
OK, Keep the box section but widen it vertically against the hull to
allow for two bolts. Add a rib down to the flange between the bolts.
After a trial fit has been done and all fixing bolts tightened to
conform it to the hull, take it out and braze or silver solder any joints.


My problem is that this all has to be done from one side so I can't put
bolts forward of the mast strut or main vertical plate.

Difficult. I presume there is a bulkhead in the way.
Can you get a strap round the front of the mast bolted to the copper
bracket either side sufficiently far out that it doesn't have sharp
bends in it? It wont have as good contact to the support post but should
help prevent flashover at the angle from the post to the bracket for
relatively little cost and difficulty of installation.

If I keep extending the bolt flange along the hull back to add
additional bolts, do I run into a situation of diminishing returns?
Yes. Two bolts a side is practical, three would be possible, more would
be of little benefit. Also the bolts should be as close as possible to
the main body of the flange and the same distance from it or the closest
will hog the current and the others be less effective.


It would be nice to simply duplicate the arrangement on the other side
but I have wires and plumbing running through that side of the bilge.
There is no reason why the other copper bracket cant have some big holes
in it for plumbing and other services, Just bolt braze or rivet a strap
of cross sectional area equivalent to the thickness times hole diameter
to both the top and bottom edges of the bracket.


I know I'll still have a lot of damage in event of a major strike but
I'd like to be figuring out my next move sitting aboard the boat than
swimming or sitting in a dinghy waiting for the next bolt. Most boats
that I have heard of being struck in this part of the world had only
electronics damage. even without good protection, so something like this
should heavily weight the odds in my favor.

Is there any advantage or downside to making this conductor out of
multiple laminations of 1/16" copper sheet?

Corrosion and getting even current sharing between the layers are
against you. Better to go thicker rather than thinner.

Dont loose sight of the fact that you *KNOW* you dont want any current
flowing down through the blocks of ballast in the keel and exploding the
possibly somewhat damp resin between them and blowing chunks of the skin
off. It also seems advisable to review your chain stowage. If its too
close to the foot of the support post, you will get side flashes out
through the hull via the chain.

I've looked over http://www.marinelightning.com/ and they dont seem to
say anything aboout the problem of a keel stepped mast (or a metal mast
support post) and the monohull installation link leads to a single
roughly annotated photo - not encouraging. Some good ideas and info
though especially for those of us with deck stepped masts without a
metal support post.

Lightning Protection questions
 

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.

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
 

"Roger Long" wrote in
:

The mast stanchion is essentially equal to a keel stepped mast. Since
my boat was originally a keel / centerboarder, the keel is large
volume and I doubt that Endeavour spent the money for a keel casting.
I'm quite sure the ballast is just stacked lead pigs in resin.
Lighting current going through that stuff would be like a bomb and the
high resistance at the bottom of the main conductor would create
extensive side flashing.

For reasons not evident on the crude drawing, any grounding plates
have to be outboard of the cabin sole. The Thomson paper says not to
let grounding conductors contact the hull but I have no choice if I am
to maintain the maximum radius recommended by other sources. The
reason for overkill on conductor and ground plate size is to
compensate for the tight conductor radius and need to run the
conductors close to the hull skin.

--
Roger Long




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

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 900', i think, tower sits on a large brown ceramic insulator. The
ring around the outside of the insulator has a lightning gap to that
metal ball hooked to the ground plate on top of the concrete base.
radiating out from the base are large copper ground straps that hook to
another ring, to distribute the hundreds of thousand of amps of current
from the stroke, and there is a ring of ground rods driven to bed rock
with a pile driver around that ring, the ring attached to the top of
them.

The key to these grounding systems is their SHORT, STRAIGHT AS POSSIBLE,
LOW IMPEDANCE path. Lightning is not considered DC in these designs.
It is a PULSE of power with an amazing bandwidth in frequencies. The
length of the conductors increases INDUCTANCE, which raises the
impedance to the very quick pulse. Impedance is our enemy. As it
rises, so does the voltage drop across it, raising the voltage on the
upper end of it. Any sharp corners MUST be avoided as that makes a
little 1 turn COIL raising impedance to the pulse. Ground strap must
CURVE around a large radius, as discussed in the article, to reduce
impedance and pulse voltage drop.

By the way, most big AM stations use the Harris DX-50 solid state 50KW
transmitters now. They use 55KW of power from the power company to put
out 50KW of RF to the antenna...This is one of the 230 switching modules
that actually provide the RF power:
http://www.hawkins.pair.com/wabcnow/wabcn14.jpg
All the cooling it needs is a few big muffin fans through those little
heat sinks to put out a blowtorch of AM radio power! Amazing
technology.

If you wanna see more, look he
http://www.hawkins.pair.com/wcbs_wfan.html
Most people have no idea where the signal comes from. They think it
comes from the studio where the stupid talking heads live.

http://www.hawkins.pair.com/wado/wadotowrleg.jpg
Here's a similar base at WADO, formerly WNEW. It has two lightning
balls across the massive insulator. The odd looking intertwined rings
are called Austin transformers. The RF won't flow between the rings
because they are far apart and provide fairly good isolation. What DOES
go across between these coils is 60 cycle AC power, magnetically
coupled, that light the tower lights you see day and night for those
folks riding to their deaths in airliners.

See all the direct, large ground straps heliarc welded to the ground
system under the tower? Low impedance...low voltage....only a few
hundred volts of pulse in a stroke to this huge tower.

http://www.hawkins.pair.com/wor/wor_tower08.jpg
This picture of the base of WOR's towers shows "Johnny Bells" and the
lightning balls to ground. Lightning flows out to the edge of the bells
then jumps the gap to the balls.

================================================== =================

Your only hope is to BYPASS the lightning's current AROUND the
passengers and hull so it doesn't HAVE to jump THRU it, punching holes
in the expensive plastique. There are many "paths" to get the lightning
off the mast. The base of the mast must be connected to the sea as
short and direct as possible. From the above pictures, you can see how
big the conductor SHOULD be, but that's not very practical in most
boats. Keel stepped masts are easy. Copper straps to the inside of the
hull clamped between large stainless washers and 2 nuts where the
grounding block mounting bolts come through the hull. Coat it all in
your favorite sealant, but make sure you leave it where the sealant can
be shed so the grounding blocks can be replaced as they eventually will
be eaten.

I guess it's too ugly to expect painted straps down the OUTSIDE of the
hull to the same bolts UNDER the grounding blocks from the lower end of
the shrouds, another great path from mast to sea around the people, hull
and expensive electronics.

Backstay and Forestay ends also need grounding blocks underwater to
bleed off the charge around the ends of it.

Just dreaming....I've been knocked flat being between the backstay and
steering wheel in the way of lightning arcing between them. You'll
never forget it......so close.

Lightning Protection questions
 

"Roger Long" wrote in news:gf6rq3$mk0$1
@registered.motzarella.org:

Sounds like I'd better stay north of Cape Cod:)



I doubt 1 in 100 boats in Charleston Harbor have any ground systems at all.
They all survive the summer storms just fine.

We do NOT have those blinding thunderstorms of the Northeast US or western
Florida, though. Ours are caused by localized thunderstorms that rise up
in huge thermals over the swamps just inland and the wind blows them over
us.

Lightning Protection questions
 

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!

Lightning Protection questions