I am building a wood 40' sailing catamaran. The mechanical propulsion
will be an outboard. I have read a lot about boat wiring and they all
talk about having a ground connection on the engine block thereby
making a connection to ground through the propeller shaft etc. With an
outboard I will not have a permanant connection to the water ground so
do I need a separate ground connection to somekind of conductive
wetted surface? I have been designing the boat to not have any
underwater metal pieces, do I need one? ABYC and USCG regs talk about
ungrounded systems but not the pros and cons or implications.

fritz

Even if you have a wooden mast, it will have antennas, stay metal
cables, electrical lighting wires and other things up the mast that
attract Mother Nature's St Elmo's Fire.

If you take a lightning hit, lightning WILL go right through your
hull, no matter what it's made of, to get to the ocean ground. The
only way to keep it from blasting a hole in the hull is a proper
grounding system on all conductive standing rigging with proper
grounding straps and underwater grounding blocks to bypass you and
your boat. If you have a lead keel, there's the best underwater
grounding block you'll get. If not, buy those metal grounding blocks
and bolt them through the wooden hull as the instructions show. The
bigger the ground straps, the better. Make all turns in the straps
SMOOTH NOT NEAT! Lightning doesn't turn corners well. Those
super-neat folds and sharp corners render any grounding for the huge
EMP pulses nearly worthless. It'll jump right out into the boat where
the 90 degree corner is placed, tearing it all to hell. The longer
the curve to turn the strap, the better.



On 11 Mar 2004 01:09:00 -0800, (gaffcat) wrote:

I am building a wood 40' sailing catamaran. The mechanical propulsion
will be an outboard. I have read a lot about boat wiring and they all
talk about having a ground connection on the engine block thereby
making a connection to ground through the propeller shaft etc. With an
outboard I will not have a permanant connection to the water ground so
do I need a separate ground connection to somekind of conductive
wetted surface? I have been designing the boat to not have any
underwater metal pieces, do I need one? ABYC and USCG regs talk about
ungrounded systems but not the pros and cons or implications.

fritz


Larry W4CSC
POWER is our friend!

(Larry W4CSC) wrote in message ...
Even if you have a wooden mast, it will have antennas, stay metal
cables, electrical lighting wires and other things up the mast that
attract Mother Nature's St Elmo's Fire.

If you take a lightning hit, lightning WILL go right through your
hull, no matter what it's made of, to get to the ocean ground. The
only way to keep it from blasting a hole in the hull is a proper
grounding system on all conductive standing rigging with proper
grounding straps and underwater grounding blocks to bypass you and
your boat. If you have a lead keel, there's the best underwater
grounding block you'll get. If not, buy those metal grounding blocks
and bolt them through the wooden hull as the instructions show. The
bigger the ground straps, the better. Make all turns in the straps
SMOOTH NOT NEAT! Lightning doesn't turn corners well. Those
super-neat folds and sharp corners render any grounding for the huge
EMP pulses nearly worthless. It'll jump right out into the boat where
the 90 degree corner is placed, tearing it all to hell. The longer
the curve to turn the strap, the better.



On 11 Mar 2004 01:09:00 -0800, (gaffcat) wrote:

I am building a wood 40' sailing catamaran. The mechanical propulsion
will be an outboard. I have read a lot about boat wiring and they all
talk about having a ground connection on the engine block thereby
making a connection to ground through the propeller shaft etc. With an
outboard I will not have a permanant connection to the water ground so
do I need a separate ground connection to somekind of conductive
wetted surface? I have been designing the boat to not have any
underwater metal pieces, do I need one? ABYC and USCG regs talk about
ungrounded systems but not the pros and cons or implications.

fritz


Larry W4CSC
POWER is our friend!

Recently I read a good article on how (not) to prevent lightning. You
can find it he http://www.panbo.com/yae/archives/000344.html

A quote from the article:
"You may, at this point, be interested in a Lightning Protection
System (LPS). But it's a misnomer, as there is no proven way to
actually protect a boat from lightning, only a technique for limiting
damage when it strikes. Actually, there is a widely held myth,
particularly among sailors, that an LPS—which is primarily a straight,
highly conductive path from mast to water—causes more harm by
attracting lightning than it does good."

Yme
http://www.panbo.com/

Lightning protection systems and marine SSB radio systems need a direct
connection to the sea water. DC electrical power systems do not need a
connection to the water. Just use a common grounding point for the negative
side of the battery (or batteries) and the negative leads from your
electrical loads. Blue Sea makes some nice ones with large bolts for the
battery leads and smaller screws for the various loads. You could also creat
your own from a strip of copper plate and either use bolts and nuts or
threaded holes for the connections. Some MaryKate Tek Gel assembly lube will
help protect against corrosion.

By the way, plastic thru-hulls fittings are not recommended for wood hulls.
The expansion and contraction can crack them. You really should use bronze.
That advice also applies to thru-hulls for speed and depth transducers.

Rusty O

I am aware of the reccomendations for lightning and SSB grounding
systems but I believe those are separate from the DC system ground. In
books I have read about the DC electrical system ground at the engine
refered to as a polarizing ground. Exactly what a polarizing ground
does or why it is desireable, is not explained. This from the USCG
regs:

Sec. 120.378 Ungrounded systems.

Each ungrounded system must be provided with a suitably sensitive
ground detection system, located at the respective switchboard, that
provides continuous indication of circuit status to ground with a
provision to momentarily remove the indicating device from the
reference
ground.

So what is a "suitably sensitive ground detection system"?

I am also aware of the plastic thru-hull wood hull issue but that is
for another forum. A properly installed plastic thru-hull in certain
wood hulls is not a problem.

fritz



"Rusty O" wrote in message hlink.net...
Lightning protection systems and marine SSB radio systems need a direct
connection to the sea water. DC electrical power systems do not need a
connection to the water. Just use a common grounding point for the negative
side of the battery (or batteries) and the negative leads from your
electrical loads. Blue Sea makes some nice ones with large bolts for the
battery leads and smaller screws for the various loads. You could also creat
your own from a strip of copper plate and either use bolts and nuts or
threaded holes for the connections. Some MaryKate Tek Gel assembly lube will
help protect against corrosion.

By the way, plastic thru-hulls fittings are not recommended for wood hulls.
The expansion and contraction can crack them. You really should use bronze.
That advice also applies to thru-hulls for speed and depth transducers.

Rusty O

In article ,
(gaffcat) wrote:

I am aware of the reccomendations for lightning and SSB grounding
systems but I believe those are separate from the DC system ground.

For most, if not all, Marine SSB MF/HF Radio Systems, DC Ground and
RF Ground ARE the same thing. This is not to imply that they couldn't
be seperated, but as a practical matter it would require some
installation Engineering to do so.

Bruce in alaska
--
add a 2 before @

In article .net,
"Rusty O" wrote:

Lightning protection systems and marine SSB radio systems need a direct
connection to the sea water.

Bzzzzt, Wrong answer, but nice try. Would you like to try again for
what's behind Door No. 2?

Marine SSB Radio Systems do NOT need a direct connection to Sea Water
to operate. Not even to operate efficently. What the Antenna Systems
of a Marine MF/HF Radio need IS an efficent Coupling to the water.
There is a Giant Difference between "Connection" and "Couping".
On a metal hulled vessel the difference is moot, but on wood and
plastic hulled vessels, the difference is Extremely Significant.

Bruce in alaska
--
add a 2 before @

Calm down Bruce. His question was about DC power systems, not the fine
points of "grounding" HF antenna systems.

My point was the DC power system does not require a "connection" to the
water like lightning systems or HF radio systems normally do.

"Sec. 120.378 Ungrounded systems" is talking about isolated, from ground,
power systems on commercial vessels. I believe, from a quick search, that
section is referring to inspected small passenger vessels that carry more
than 150 passengers. In any case they are not talking about a DC power
system on an 'uninspected' non-commercial wood hulled 40 foot catamaran.

Besides, the connection point for the negative battery cables and the
negative leads from the lights, etc. IS the boats ground point. So the
system is 'grounded' even if there is nothing else, like an engine, to
connect to it.. If you added a second, completely separate, electrical
system, and didn't connect it to this 'ground' point, then that would be an
'ungrounded' system. However, I have no idea why you would want to do this
on your boat.

A "Ground Detection System" is used to monitor an isolated, non-grounded,
electrical system where there would be danger to people or other equipment
if a portion of the ungrounded system was accidentally grounded. Such as,
exposed current carrying conductors could then present a shock hazard. I
have seen systems like this for aluminum smelting pot lines and nuclear
waste vitrification furnaces. I don't think you need one on your catamaran.

"Polarizing ground" generally refers to the ground applied to one leg of the
secondary winding of an AC transformer. This is how a "Neutral" leg is
created for a 'separately derived' AC power system. Again, this doesn't
apply for a simple DC power system on a wood hulled 40 foot catamaran.

Rusty O

If the outboard has a starter or alternator or any other electronics, it
will probably be connected from DC ground to the water. Or if not, maybe
plan for it if you (or the next owner) ever change outboards to one with
wiring someday.

Dave


"gaffcat" wrote in message
m...
I am building a wood 40' sailing catamaran. The mechanical propulsion
will be an outboard. I have read a lot about boat wiring and they all
talk about having a ground connection on the engine block thereby
making a connection to ground through the propeller shaft etc. With an
outboard I will not have a permanant connection to the water ground so
do I need a separate ground connection to somekind of conductive
wetted surface? I have been designing the boat to not have any
underwater metal pieces, do I need one? ABYC and USCG regs talk about
ungrounded systems but not the pros and cons or implications.

fritz