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Author Topic:   Using In-Hull SONAR Transducers in Unibond Hulls
davidmassi posted 03-27-2008 06:39 PM ET (US)   Profile for davidmassi  
Has anybody ever successfully installed an in-hull transducer in a classic Nauset? I am NOT referring to a through-hull that has a hole drilled through the boat, but a transducer that mounts on the interior of the hull and transmits [and receives] through the boat. If so, what power transducer did you use and how well did it work?
dino54904 posted 04-01-2008 12:22 PM ET (US)     Profile for dino54904  Send Email to dino54904     

I had a Nauset that I tried to use a thru-hull transducer on. I stuck the face of the transducer to the hull under the console with a blob of marine seal. When the boat was stationary it recorded bottom contours and fish quite well but when the boat was underway I received no usable data on the screen. I tried the same technique in the area under the console where the wires and steering cable run through thinking that there is no foam there. I ended up putting a transom mount transducer on the boat.

jimh posted 04-02-2008 10:28 PM ET (US)     Profile for jimh  Send Email to jimh     
The ultrasonic sound waves needed for SONAR do not propagate well through a material with a high acoustic impedance. The air pockets of the interior foam of a Unibond hull have a high acoustic impedance. Attempts to transmit ultrasonic acoustic waves across the foam will not be very successful.

In most applications of an in-hull SONAR transducer the device is bonded directly to the hull bottom laminate. You could accomplish this on a Boston Whaler boat by drilling a large diameter hole into the hull from the deck, removing all of the foam, then installing the SONAR transducer directly to the upper side of the hull bottom laminate. It would probably be necessary to fill in the void created by the cavity you would have made in the foam, so your SONAR transducer would really be sealed in place.

I do not recall any reports of anyone attempting this approach.

roloaddict posted 04-02-2008 11:34 PM ET (US)     Profile for roloaddict  Send Email to roloaddict     
I am working toward this approach. I have removed the foam and bonded a 1 Kw transducer tank to the hull. The tank will be filled with RV antifreeze after the transducer is installed. This is located where the aft cable tunnel originally was located.

This area of the hull is about 1/4" thick and even at 200KHz should not degrade the signal too bad. I have gone with a high end transducer to compensate for the losses that will occur and give any sounder that I put in a superiority complex.

jimh posted 04-03-2008 07:27 PM ET (US)     Profile for jimh  Send Email to jimh     
That is an interesting approach. Let us know how it works.

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