Depth Transducer Mounting Without a Through-Hull

Has anyone mounted a depth transducer inside a solid fiberglass hull without using a through-hull?

It is my understanding that the fiberglass is transparent to a transducer so long as the mounting does not cause an air gap in the transducer's sensing path. The recommendations that I have seen suggest mounting the transducer in a tube affixed to the inside surface of the hull and immersing the transducer in either water or mineral oil.

I'd be very interested in anyone's real-world experience with this, namely (i) does it work?, (ii) any hands-on problems discovered with the mounting issues, including things like the mineral oil dissolving or saturating certain materials or sealing compounds.

Thanks in advance for any input/thoughts.

JPC

 

ALL new fibreglass boats with factory mounted transducers are in side the hull. Cheaper and better. No bubbles in the Silicone Rubber blob or the Epoxy blob. Push the transducer down to the deck. Done. Silicone Rubber is much easier to pull up. Wipe up any excess!

 

a good way to find a good place to build a box to mount a transducer in your hull is to fill a ziplock bag with water, make sure there is no air in it. then you can wet the inside of the hull where you think you might like to mount the transducer, lay the bag of water in that spot then place the transducer ontop the bag. take the boat for a spin and see what its like. you can find the perfect spot without interfeering bubbles or prop noise with next to no effort. takes 2 people, one to drive one to hold the bag and transducer. dont however put your hand on the transducers face with it running!

 

I hate it when I get stuck holding the bag

 

Interesting...Does hull thickness and laminate composition make a difference? As far as transducer manufacturers go, does make/model have an effect?

We're working with an Airmar P66 as part of our Furuno package...

 

Another way I've seen it done is to cut a short piece of ABS pipe with the end angled to mach the hull deadrise in that area. Silicone it to the hull. Set the transducer inside. Fill with mineral oil. Cap off.

That ensures no bubbles like in silicone.

The main problem I've seen is trying to find a section of the hull with no voids - can be a problem with cheaper chopper-hulls.

Also keep in mind, it probably won't work with a foam cored hull.

 

As suggested by everybody, it has to be immersed in mineral oil. the oil seems to work better than water as a medium to pass the frequency. without the medium or if there are voids or bubbles in the medium, the reading is erroneos or none at all. Air is a poor conductor.

I also find that i get more accurate reading if the transducer point straight down rather than following the deadrise of the boat. If it is pointed other than vertical, the signal that is bounced back might not reflect back to the transducer. No reading.

 

Mentioned so far are glass hulls, any expirience with oak stems and mahagony planks. epoxy coated. We own a 1924 R-sloop.