Topband: Portable 160M Antenna Options

[WA7VNI]

Hi All,

I've been playing around with the idea of trying the next
160 M contest from a portable location. Here's the deal. Any
thoughts on the installation described below will be
appreciated.

I can setup on my sailboat (37 ft trimaran) docked in the
saltwater of Puget Sound. The boat is located near the far
end of a dock about 250 ft. from shore. The boat has a mast
that will allow a support point 50+ ft. above the water.

The antenna would be an Inverted L. The vertical portion
would be rigged so as to be supported well away from the
aluminum mast on my end and as indicated above would be
around 50 ft. high. The far end will be supported from a
mast of nearly the same height on another boat that is
located 175 ft. away. There are no other boats in the path
between the two masts nor can there be unless someone makes
a very serious navigational error. The horizontal section of
wire would simple run over a long section of low wooden dock
between the two boats.

For grounding (at a minimum) I will use the existing ground
system on my sailboat. The system consists of a 2 1/2 ft X 5
ft section of bronze plate installed in the centerboard
trunk and fully immersed in the water as well as all of the
underwater metallic hardware that is bonded together. The
existing ground system on the boat is quite effective when
used against the insulated backstay underway on the high
bands. My question is the best way to improve on that for
160.

I am planning on adding one or two 1/4 wave radials (#12
insulated wire) lying on the wooden dock (about 18" above
the water). I can install the radials on the dock easily by
temporarily fastening them to the dock edge so they don't
present a trip hazard. I can't "elevate" them further. They
would run 180 degrees from each other. I can't install any
on the dock in any other direction. I could however add one
or two actually in the water. They would have to drop down
off the deck and onto the sea bottom so they would not be
fully extended out from the base of the antenna. 

* Any advantage to adding one or two radials in the water
given the limitations?
* Any other suggestions on improving the ground system?

I've already checked out the electrical noise on receive and
its not bad. Not many folks hanging around and running stuff
this time of year. The way the boat is situated I'm pretty
much out in the open near the far end of the dock not stuck
in a forest of aluminum masts. It seems to me that this
might be a very effective antenna. Any other comments on how
to best setup this antenna? 

Thanks in advance.
 
Patrick 
WA7VNI