I haven't seen any of these innumerable notes of which you write...

But thanks...sounds like a good idea. I can build a little
holder for the trandsducer that will have it set still in the hull.
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If you want to shoot through the hull you
need to fill the air gap between the
transducer and the hull with something
like mineral oil. the way it's normally
described is to build a little oil tight box
inside the hull, fill it with the oil, and mount
the transducer so it's face is even with
the surface of the water inside the oil
cavity.

You need this 'impedance match' to get
the sound through the hull. I know this
works well in a 'glass hull, but you
can try some of the other suggestions
in earlier appends.

Frank