In article t,
"Doug" wrote:

AirMar through the hulls will work with some metal hulls. They gave
presentations at Furuno, Raymarine and Northstar service seminars. What was
interesting was that in some cases thicker aluminum hull material was better
than thinner metal. I suggest you check AirMar literature regarding what
metals work and recommended thickness for through the hull ducers.
Doug K7ABX

When I worked at Northern Radio in Seattle, (30 years ago) I worked on a
DE in Todd Shipyard that used a Hydrolic Ram to shock the Hull and make
it ring at the designed frequency of the sonar. Totally Mechanical Sonar
Transmitter and very sensitive Receiving Transducers. They figured that
the transmit power was in the hundreds of KWs and you really couldn't
sleep when it was active, because the whole hull was vibrating at the
resonate frequency.

Bruce in alaska
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