"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