Installing In Hull Transducer

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Triton106
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Installing In Hull Transducer

Post by Triton106 »

My WC Triton came with two transducers (depth), one thru-hull and another in-hull. When I tossed out the PO's antique depth sounder that is about the size of small toaster and weighs a ton I replaced it with a Norcross Hawkeye depth sounder mounted on the bulkhead. I conneted it with the thru-hull t-ducer. It has worked very well but everytime I haul the boat out I cringe at the sight of the poor installation and hate the way it sticks out 3~4 inches from the hull. I have always wanted to replace it with the in-hull t-ducer. Well, I finally got around to it recently. However, when I connected up the t-ducer with the sounder it could not read. I double checked and made sure that wiring is correct. I toss the t-ducer in the water and, voila, it reads just fine, exactly the same reading as the thru-hull t-ducer.

Not able to decipher what is the cause I ripped the t-ducer out. It came out easily. Judging by the way it came out I would say the PO used silicon to glue it to the hull. I thought maybe it was partially delaminated. So I cleaned it up and applied new silicon and tested the sounder again. Again, it did not read.

After logging on to the Airmar website I realized that silicon does not work well for in-hull t-ducer. They recommend using epoxy instead of silicon. I will try that next weekend. But before doing that I have a few questions that I hope you can help me with:

1. Do I need to make sure that the t-ducer is perpendicular to water surface? In other words, face straight down? One boatyard person told me that it does not matter since most of the time the boat is heeled over anyway. The t-ducer will still read correctly. I don't know about that since Airmar and Raymarine website both seem to indicate that the t-ducer should face straight down.

2. I hate the thought of having to install "oil bath" for the t-ducer. Too complicated and the t-ducer is not round but rather rectangular shape and is not condusive to sitting in the "oil bath". Any other methods?

Beyond these questions I would appreciate if you can share your experience with in-hull sounders. Do you like them, do they perform well compared with thru-hull t-ducers?

Thanks and regards,
Ray D. Chang
Triton 106 in Berkeley, CA
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Rachel
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Re: Installing In Hull Transducer

Post by Rachel »

If you want to test out other, potentially better locations for the transducer, one way is to put it in a Zip-Loc bag full of water, then move it around and test how it works.

As far as I know, bedding it in epoxy should work fine as long as you've got a good location to begin with (you don't want any air entrainment, which is why they don't recommend silicone as mounting goop).

I know on some boats you do have to hunt and peck a bit to find the best spot.

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Re: Installing In Hull Transducer

Post by Henk »

I also used the zip-lock bag trick, but it didn't work until I made the outside of the bag wet as well. One little air bubble will prevent the transducer from working. After finding a good and reasonably flat and 'level' spot where the sounder showed good readings, (underneath quarter berth) I used a lot of silicone to install the transducer and it works fine. Made sure there were no air bubbles in the silicone and taped it to the hull until the silicone was dry. The only time it doesn't work is when the engine is in reverse. It's the prop cavitation so do not install the transducer aft of the propeller.
I use a Horizon (oops, Humminbird not Horizon) 150 fish finder. It gives me readings to about 600 feet but we use it mainly for anchoring. There is a 12 foot tidal range around here (BC West coast) so we do need it. I checked it's accuracy in shallow water and it's dead on.

By the way, as I installed it, the sounder was on and 'pinging'. That way I knew it was working and no bubbles in the silicone. I also figured that if I did manage to screw-up removing it and trying again would be a lot easier than if I used epoxy.
Last edited by Henk on Sun Nov 22, 2009 10:44 pm, edited 1 time in total.
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Re: Installing In Hull Transducer

Post by David VanDenburgh »

Triton106 wrote: 1. Do I need to make sure that the t-ducer is perpendicular to water surface? In other words, face straight down? One boatyard person told me that it does not matter since most of the time the boat is heeled over anyway. The t-ducer will still read correctly. I don't know about that since Airmar and Raymarine website both seem to indicate that the t-ducer should face straight down.
I can't help you with your other questions, but I would be inclined to mount it straight down since the boat is rarely heeling when you're entering an inlet or poking about in an anchorage. It's times like that when I'm most interested in depth sounder accuracy.
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Re: Installing In Hull Transducer

Post by Quetzalsailor »

Straight down is better. Draw the picture and you can see right away what's happening. The depthfinder is not smart enough to use the trigonometry necessary to correct for the angle; it is smart enough to be corrected for depth of transducer. Requiring yourself to know, remember, and use the multiplier necessary to correct the depth is, for me for sure, way too much like work! Of course, a few degrees of deadrise, you probably would not care. I just did a quick sketch for about 15 degrees; 5 1/2" became 5 7/8", or 5'-6 became 5'-10". Since most folks would wish their transducer to be as far forward as convenient, the deadrise is likely to be greater.

Our previous boat had a lidded tub of water sealed to the inside of the hull, up in the bow. Worked fine as long as there was water in the tub (had to be refilled annually, and required a smidge of bleach to keep the slime and smell away. Current boat has a throughhull in the bottom, aft of the mast, and the transducer sits at the 15ish deg angle of deadrise there.

As for silicone or epoxy, follow the instructions for your transducer.
Triton106
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Re: Installing In Hull Transducer

Post by Triton106 »

Thanks everyone for your help!

It's comforting to know that I have to hunt around for a good spot. I thought the problem maybe because my t-ducer is not designed for in-hull use. Ziplock bag is a great trick. But I am still puzzled that even if there are tiny bubbles in the silicon I used why would it not read anything at all?

As for leveling it I agree with the argument that most of the time when we need depth sounder is when we are anchoring or gunkholing so the boat is level. But if I install it with a approximately 15~20 degree deadrise (the original location is under the port settee right aft of the head) and the resulting delta is only a few inches I am tempted to just leave that along. As I said, I am not too crazy about the idea of installing a "oil bath" or "water bath".

Thanks again.
Ray D. Chang
Triton 106 in Berkeley, CA
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Re: Installing In Hull Transducer

Post by Robert The Gray »

I epoxied the transducer for my fish finder directly to the floor of the fore peak. right in the middle. I am going to continue my thoughts on fish finders vs. depth sounders in another thread.
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Re: Installing In Hull Transducer

Post by ddsailor25 »

What if the hull is cored? Does that change the type of transducer needed?

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Re: Installing In Hull Transducer

Post by Ryan »

Typically, if you have a cored hull, you either have to remove the core at the install spot and replace with solid glass, or install a good old fashioned thru hull xducer.
Triton106
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Re: Installing In Hull Transducer

Post by Triton106 »

Just want to update with the progress on the project.

I went back to the boat today and after anticipating all week to find out if the t-duce works in-hull or not I went right to working on finding a spot. But first I sanded and cleaned out two potential spots under the port ans starboard settes close to the bulkhead separating saloon from the head. I then found a ziplock bag and filled it with water and dumped the t-ducer in it. After turning on the power I still could not get a reading on the port side but I was able to get a good consistent reading from the starboard side. I was thrilled to say the least. But the spot is not horizontal but rather has a incline of 25 to 30 degrees to horizon. That means the depth reading is not exact (as Quetzalsailor pointed out early in this thread). I remembered my high school math and calculated the adjustement I need to make to correct for the angle. To get the exact depth I need to multiply the depth sounder reading by cosine of the angle (which is approximately 25 to 30 degrees). From my high school math book I know

Cosine (25 deg) = .901
Cosine (30 deg) = .866

For my purpose I think just taking 90% of the depth sounder reading is close enough. It's a lot easier than installing oil bath or water bath to get the perfect level reading. I know my Triton draft is approximately 4 feet. So any reading approaching 5 feet means trouble ahead.

Next week I will epoxy it down on the hull. Thanks everyone for your help. This forum is just full of knowledge and experience.
Ray D. Chang
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Rachel
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Re: Installing In Hull Transducer

Post by Rachel »

Glad you found a good spot. And I always enjoy reading a follow-up post - thanks!

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Re: Installing In Hull Transducer

Post by Shoalcove »

I installed my transducer temporarily(ha!) 4 years ago by sticking a short piece of PVC pipe to the inside of the hull in a thick bed of 4200. After it cured I pored in some mineral oil, dropped the transducer in and pushed some sponge around it to keep the oil there. It works great and I haven't added any oil since. Not what you'll read in Nigel Calder's books but hey, it worked!
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Re: Installing In Hull Transducer

Post by Henk »

When I installed the transducer, I installed it in a BIG goop of silicone. Then I leveled it out while looking at the screen to make sure it was still receiving. I then taped it to the hull so the silicone could dry and it wouldn't 'sink' into the silicone and slide down the hull as it cured. This way I overcame the hull angle problem and it shoots (almost) straight down.
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Re: Installing In Hull Transducer

Post by texaspsdx »

On another forum I read, the poster said he had mounted his transducer using toliet bowl wax. He stated he had done several using this method with great results. I'm thinking about trying it.
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Re: Installing In Hull Transducer

Post by Triton106 »

What is the advantage of using wax vs. epoxy? It seems that wax is not going to hold the t-ducer in place.
Ray D. Chang
Triton 106 in Berkeley, CA
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