T&T: SSB/Ham ground plane on a boat

[Dennis OConnor]

Well, ignoring the dust up over who is qualified, etc... 
Yes, your copper tube will approximate the surface area of the foil that is
commonly used for a ground plane/counterpoise, and will work just fine..
However, it will be expensive and heavy and vast overkill (not necessarily
bad)...
 
The feed point is 'probably' immaterial for a non resonant counterpoise...
Unless the ground plane is resonant at the frequency(s) you use, this is not
likely to be an issue...  Really you want to put in as many feet of foil/pipe
as you can... 
 
Now, if possible, we like to get a quarter wave of wire/foil/etc. at the
lowest frequency in use, when we can...
For instance the ten meter band (28 mhz) would only need 8 feet to be an
efficient counterpoise...
The twenty meter band (14 mhz) will need 16 feet...
And the eighty meter band (3.5 mhz) will need 64 feet...
For SSB marine frequencies near 5 mhz (60 meter band) 45 feet would be
ideal..
Given the reality of installing this in a boat, most counterpoise
installations will not have runs approximating 45 feet, but you do the best
you can...
 
In a boat, you can also think of running a foil around the periphery of the
hull, making a boat shaped elipse, leaving the two far ends about 2 or 3 feet
apart and unjoined (i.e. not a loop)  Feeding this somewhere near the center
will work...
Joining the counterpoise to other metal runs is a good idea (usually  - but
the devil is in the details)...  It is best if you do the join from near the
transmitter feed point so that large metal objects are close to the same level
of RF potential as the transmitter...
 
For instance , taking a quarter wave of wire and running it 16 feet from the
transmitter and having the far end connect to some electrical device, like
your all electronic diesel engine, and then transmitting on 20 meters is a
particularly bad idea... The far end of a quarter wave of wire will be "hot"
with RF when transmitting (and the running engine will likely feed all kinds
of noise back into the receiver to get even)...
 
Basically, put on as much wire as you can, try to make it some kind of a "fan
out" from the feed point as opposed the the end of a long single wire/foil
looping through the boat, and be happy as it likely will work...

denny / k8do