Lightning Protection questions
 

Good point. If I could replace my metal compression post with wood, I could
skip the step ground plate and focus on the stays. It would be easier to
install the ground plate than to do that though.

I'm beginning to get the picture. Lightning will go everywhere and the
charge can't be led. It's more a matter of creating shadows, gaps, and
regions of reduced current at critical points like people and watertight
boundaries.

--
Roger Long

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:

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, I believe your question is:

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.

The bend is pretty critical. By making a turn you create part of a
transformer otherwise known as impedance or the resistance to an
alternating voltage. The tighter the bend the higher the impedance.
Also the higher the frequency the higher the impedance. Since a
lighting strike typically has very high energy, high impedance
components you are well advised to make the radius as smooth as possible.

Paralleling the run may help or may not. Without doing much more
research I can't tell. The problem would be if the two runs create a
field that would counteract the flow in the opposing wire thus again
increasing the impedance.

Larger wire helps but maybe not as much as you would think. At high
frequencies the current only runs on the outside of the wire in
something known as "skin effect." That is why they recommend braided
wire, much more surface area. BTW skin effect is caused by the parallel
paths in a wire from one side to the other, so you see that it can occur
in even small wires.

At radar frequencies they use hollow wires known as waveguide. I have
seen waveguide melted because of resistance heating due to a small dent
that caused some local impedance.

Probably not the answer you were hoping for. Sorry.

Lightning Protection questions
 

IanM wrote:

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?

I can't get to the front of the bracket without major surgery that would
compromise the boat's structural integrity as well as appearance.

I'm beginning to realize that this subject is so complex that only tests in
a high voltage chamber (which would cost enough to simply buy a high end
boat with protection already built in) will really answer the question but,
do you think this is worth putting in?

http://home.maine.rr.com/rlma/Ground.jpg

This is the earlier drawing with a top view added. The horizontal brackets
would be top and bottom. I recognize that the long tail is probably useless
for the primary current flow but will assist in attaching the copper outside
the hull and give me a point to lead bonds from the toe rail and other items
to.

I may be cooked anyway. The mast post ends in a plate lagged into the top
of the fiberglass ballast encapsulation so four sharp pointed lag screws
lead right down close to the encapsulated lead. I'm can't imagine now that
there won't be enough current flow left over, regardless of what I do, to
prevent something gross happening down in the keel area.

--
Roger Long

Lightning Protection questions
 

Roger Long schrieb:

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.

Hello,

the problem with the bends of the conductors is when the bend is to
tight, the lightning current will not follow the bend, it will leave the
conductor an flash thru the air in a direct line to the next best earth
point. Increasing the cross section does not help, you only can connect
more of these bends in parallel.

Bye

Lightning Protection questions
 

On Sun, 09 Nov 2008 20:31:02 -0500, someone posting as Marty purportedly
wrote:

#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.

So I'm guessing based on what I've read here in this thread, that hanging
a length of chain off the bottom of one of the upper shrouds into the
water -as suggested in a book I have called the "Emergency Reference
Manual"- would be one of those suggestions that would give a sailor some
sense of protection, without actually providing any.


--
150 days till re-launch (shut up Larry).

Lightning Protection questions
 

Wayne.B wrote in
:

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.



You should be able to put a large loopstick up on deck tuned to either
station, put it to a rectifier and recharge the boat...(c;

I know a ham who lives off the end of the old WKBW 1520Khz 3-tower
directional array in Hamburg, NY. There's a big open loopstick tuned
circuit in his attic that has powered the yard lights, his garage lights
and a couple of incandescents in the hallway for years. They all run
24/7 because if you turn one of them off, the impedance of the load
changes and blows all the other bulbs in the array....If one bulb blows,
they all blow....too funny.

If you have tooth fillings made with metal amalgams, you get to listen
to WWKB talk radio, these days, 24/7 with no radio at all..

And they told me RF radiation was dangerous to my health. My ham buddy
is 82 this year. He glows a little green in a darkened room, but other
than that he's fine....(c;]

PS - You adjust the loopstick's parallel tuning capacitor in and out of
partial resonance like a light dimmer to get the brightness you want.
Free power, just like Nikola Tesla envisioned.

Lightning Protection questions
 

"Roger Long" wrote in
:

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:)


My Sea Ray jetboat was made to ABYC standards, too. It said so right there
on the little sticker. That's why the goddamned fuel tank inlet and vent
fittings were way up under the cockpit decking so you couldn't even see
them, much less change them or check them for tightness before the boat
exploded. To get to them, you simply disassembled the entire boat and took
the whole top off.....or you could take a rip saw and open a hole in the
deck but you'd have to be careful not to go 1/2" too deep or you'd be
cutting into the cheap milk bottle polyethelene plastic tank with 25
gallons of explosives inside held in with two tiny plastic angle brackets
eating into the soft plastic's aft end.

ABYC should be very proud.....

The stereo fuse holder was on the forward bulkhead of the engine
compartment held in with one screw.

Everyone should own one Sea Ray in their life......just one.

It's made by Bayliner....er, ah.....Brunswick....you know.

Lightning Protection questions
 

wordsmith wrote in news:ur6dnXDWjvz3
:

(shut up Larry).


Who? Me?

I'm not sleeping in it....(c;]

Lightning Protection questions
 

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

"Marty" wrote in message
om...
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?


Bzzzt... sorry. LOL

No idea... good question though.


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

Lightning Protection questions
 

On Mon, 10 Nov 2008 04:12:36 +0000, Larry wrote:

(Richard Casady) wrote in
:

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



I thought they called that a "metal hull"....

Closed. A sub qualifies.

Casady