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