Electronics gurus: In-hull transducer?

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CenCal
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Electronics gurus: In-hull transducer?

Post by CenCal » Mon Jan 15, 2018 12:42 pm

Hey there, boat gurus. I was on here as LoHo, but could not log on or change my password from this computer for a couple months.

I was about to buy a new transducer to install inside the middle of the interior hull, when it occurred to me that the old exterior transducer, mounted in epoxy like a new one would be, might work just fine. Does anyone know why the old transom mount wouldn't properly installed inside the hull?

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LoHo
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Re: Electronics gurus: In-hull transducer?

Post by LoHo » Wed Jan 17, 2018 10:39 am

Good question! A bit of research reveals that several boaters have used the exterior transducer for interior installations, so give it a shot.

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RussMT
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Re: Electronics gurus: In-hull transducer?

Post by RussMT » Wed Jan 17, 2018 1:59 pm

I'm confused on the LoHo thing.

Anyway. You can mount most transducers in a bed of silicone inside the hull. Just avoid any water ballast spots (if applicable).

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topcat0399
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Re: Electronics gurus: In-hull transducer?

Post by topcat0399 » Wed Jan 17, 2018 3:10 pm

CenCal wrote:Hey there, boat gurus. I was on here as LoHo, but could not log on or change my password from this computer for a couple months.

I was about to buy a new transducer to install inside the middle of the interior hull, when it occurred to me that the old exterior transducer, mounted in epoxy like a new one would be, might work just fine. Does anyone know why the old transom mount wouldn't properly installed inside the hull?

I have an exterior transducer inside the hull on my V224.
I slapped it in a wad of firmly compacted plumbers putty
under the berth as close to the front of the keel trunk as I could get it
(essentially right up against the bulkhead).
Works just fine and no glue required.

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Re: Electronics gurus: In-hull transducer?

Post by LoHo » Wed Jan 17, 2018 5:21 pm

Russ, I answered my own post after more research.

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Re: Electronics gurus: In-hull transducer?

Post by BOAT » Wed Jan 17, 2018 5:34 pm

RussMT wrote:I'm confused on the LoHo thing.

Anyway. You can mount most transducers in a bed of silicone inside the hull. Just avoid any water ballast spots (if applicable).

yes

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Re: Electronics gurus: In-hull transducer?

Post by tlgeddes » Wed Jan 17, 2018 11:41 pm

RussMT wrote:I'm confused on the LoHo thing.

Anyway. You can mount most transducers in a bed of silicone inside the hull. Just avoid any water ballast spots (if applicable).
This is why I love this forum. I put a new Eagle-Eye depth sounder in and it is intermittent with it mostly not working. I had all but given up. I am pretty sure I mounted it right over the water ballast :o Thank you RussMT!

So does it matter which type of adhesive? The manufacturer recommended a slow cure epoxy which no one carried.
I will move it but if there is a commonly available product that info would be great.

Now off to find a drawing of where that ballast is glassed in.....

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Re: Electronics gurus: In-hull transducer?

Post by RussMT » Thu Jan 18, 2018 12:11 am

I've mounted many transducers in a large blob of silicone caulk. I cut the bottom out of a plastic bowl to keep the glob from oozing out, but you can get creative.

The reason I like this "adhesive" is that if it doesn't work, a sharp knife can cut it out. I used this to mount a wood plate to attach a washdown pump.

--Russ

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Re: Electronics gurus: In-hull transducer?

Post by BOAT » Thu Jan 18, 2018 9:43 am

"Slow Cure epoxy" in other words: JB WELD.

It's a VERY slow cure epoxy (over 24 hours) so you need to monitor it's flow if your using it to make a watertight seal. If your doing a standard in hull transducer reservoir (like I have) you need to lay the bead in a perfect circle on the hull and also another perfect bead on the reservoir. Then monitor it for flow as it cured - as the epoxy cures it can flow out of a crevice and create a leak (slow cure is a lot harder to work with than fast cure, but slow cure is much more secure and will not develop leaks over time like fast cure will) - also know that slow cure is permanent).

After about 10 hours if it looks like there has been a lot of flow add more epoxy around the outer and inner bead. Once it's water tight it'a water tight forever. You fill the reservoir with glycol so if there is a leak glycol is going to find it.

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Re: Electronics gurus: In-hull transducer?

Post by tlgeddes » Thu Jan 18, 2018 10:52 am

Thankyou BOAT and RussMT. I used a medium cure epoxy from True Value. I hope I will be able to get it off. This is an inside-hull mount so I will try silicone first to verify I have a location that works.

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Re: Electronics gurus: In-hull transducer?

Post by AndyVS » Thu Jan 18, 2018 11:55 am

I used a small piece of wax from a toilet ring and it works fine. The wax holds it's shape even when it's hot. I've bumped it loose a couple of times when putting stuff in the laz and I just press it back in place.

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Re: Electronics gurus: In-hull transducer?

Post by BOAT » Thu Jan 18, 2018 12:14 pm

AndyVS wrote:I used a small piece of wax from a toilet ring and it works fine. The wax holds it's shape even when it's hot. I've bumped it loose a couple of times when putting stuff in the laz and I just press it back in place.

Yes, all great ideas guys - another one is to simply put a plastic bag full of water under the transducer - let me explain:

The best way i can illustrate how the transducer works is to make you remember what sounds you hear when you swim underwater. Have you ever noticed how your ears need to come in contact with the water for you to hear well underwater? It's like that - your ear (transducer) must be in contact with the water to get a good sound.

The very best sound will come from having the transducer right in the water under the boat (a Thru Hull transducer) and you drill a hole in the boat to do that or drag a transducer behind the boat. Dragging a transducer behind the boat works well but can be effected by cavitation and turbulence behind the transom (noise) - the best transducers (side scan CHIRP units) are dragged behind the boat at depth so they are free of surface noise. The second best way to do it is to have a water pool right in contact with a part of the the hull that is in contact with the water below (an In Hull reservoir transducer) and that is what I have on 'boat'. If the reservoir goes dry - the sonar works badly.

The same principle as a reservoir in hull transducer is what your doing when you pack the unit in paste or gel or glue.

But again, consider the "ear" illustration above: How well would your "ear" hear things if they were packed with silicon? Or wax? That's why the manufactures of in hull transducers state in their manuals to use a bag of water to test the transducer - because it makes a much better sound. You might want to reconsider using any material that will insulate the sound from the unit by adding air like foam or glue or wax can.

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Re: Electronics gurus: In-hull transducer?

Post by tlgeddes » Thu Jan 18, 2018 2:03 pm

Yes that matches what I read about slow cure epoxy. Because it cures slowly it allows the little air bubbles to escape leaving a pure solution. Now with BOAT’s explanation I understand why you don’t want air in there.

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Re: Electronics gurus: In-hull transducer?

Post by sailboatmike » Thu Jan 18, 2018 3:44 pm

What about some Butyl tape, it never goes off so the transducer can be removed if required, its sticky enough to hold the unit securely and being tape you dont have the same air bubble issue as with silicon or other semi liquid fixing methods

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Re: Electronics gurus: In-hull transducer?

Post by RussMT » Thu Jan 18, 2018 5:25 pm

sailboatmike wrote:What about some Butyl tape, it never goes off so the transducer can be removed if required, its sticky enough to hold the unit securely and being tape you dont have the same air bubble issue as with silicon or other semi liquid fixing methods
I've never tried it but I bet it would work.

The key seems to be allowing ultrasonic sound waves to "transduce" through the hull. Air bubbles and voids act as an insulator.

I'm all about being able to remove it if it doesn't work or I change my mind about location. That's why I'm not keen on things that are permanent. The transducer isn't carrying any load, just needs to be in solid contact with the hull.

--Russ

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