Aborted launch - new depth sounder not working

[eddystone]

Not a good morning! Fitted a new Raymarine i50 to replace old spinning diode, with Airmar P79 transducer, the in - hull type (I.e. fixed to inside of hull. All I have is three hyphens and no depth reading at all so now back on dry land.
Spent a lot of time filling and sanding to get a dead rise angle within limits although using the adjustments got top of transducer within a few degrees of level although not forward/aft where it’s 8 or 9 degrees. The display unit doesn’t have its own 12v supply as I’ve used the spur cable from the i50 log alongside.
So, trying to diagnose the problem:
1. The i50 log is providing power to the identical depth.
2. I can hear the transducer ticking so it must be receiving signal/power from the instrument
3. The angle in the fore/aft plane may be outside limits but that shouldn’t prevent getting some sort of reading
4. Although it’s not on a sea talk backbone i. e the i50 it’s daisy chained off has a single 12v connection would that block the transducer signal?
5. Obviously I’ve added a bit of thickness to the hull to reduce the dead rise but that should weaken not block the signal
Any thoughts?

 

[yotter]

What is the hull contruction solid GRP, foam cored GRP, wood, other? If you can hear it clicking inside, can you hear it on the outside of the hull. What I am getting at is that is may be an impedence issue. The bonding to the inside of the hull is also important. I recall doing this many years ago and I bonded in a cup which I filled with liquid and this worked well, that was a Stowe Dataline transducer.

 

[eddystone]

Hull is solid GRP added a bit of (solid) filler to reduce deadrise angle - hadn’t thought of checking for click outside. Generally I assumed thickness of hull would weaken signal rather than block it provided there are no voids

 

[yotter]

Feel the outside of the hull, or put your ear close to it (if safe to do so), although the frequency is outside the human hearing range (>100kHz) you should still hear licks.

 

[yotter]

clicks!

 

[Daydream believer]

How is the transducer fitted? Mastic or in an oil bath? What do Raymarine recommend?
Why add to the thickness of hull by extra fairing? most through hull transducers come out the hull at an angle to the vertical & operate with the hull heeled . So, surely, it stands to reason it is not necessary to fair it in internally.
Are you happy that the transducer is receiving sufficient voltage to operate correctly? Just ticking may not mean that a signal is being properly transmitted- or does it?
Is the receiving monitor properly installed?

 

[Bodach na mara]

I fitted a Garmin one last year, probably Airmar in fact. Following the instructions, I first located a suitable place in the hull by using a poly bag of water and placing the transducer on it against different parts of the hull until I got a good signal. Obviously the boat was afloat. Next I chose one of the five mounting tanks supplied to suit the deadrise at the chosen location. The tank is mounted so that the top is near horizontal in both axes thus lateral and longitudinal slope are compensated. You rotate the tank to achieve this. I then marked both hull and tank to ensure correct positioning. The hull inside surface was then prepared and the tank mounted using some sealant or adhesive , I forget which one. After a while to allow setting, the tank was filled with some kind of oil, the transducer inserted and fixed down with the supplied screws. There was no filler or anything used to level the hull.

On a previous boat i was fixing a transom-mount transducer inside. The process I used was simpler. I used wallpaper paste as the conductive material to find a good location, cleaned it off and stuck it down with a wodge of silicon. No pissing about with deadrise at all I just was lucky in finding a spot just forward of the keel that was near level. I think transducers are quite tolerant. After all a sailing boat spends a lot of time heeled.

 

[Bran]

Is your display just a depth display or is it a tridata? I ask because there is a requirement that the system can record the water temperature, the speed sensors incorporate a thermistor to do this. If no temperature sensor is fitted it needs a 10 k ohm resistor fitting across two of the connectors on the back of the display. I fitted this on a bidata i40. Not certain that it is relevant with a depth only display.

 

[dankilb]

Can’t you use a length of plastic (plumbing) pipe with the end sealed for a simulated test of transducers? Never had cause to try it - but sure I read somewhere, it even gives the depth (of the pipe). No good if the transducer won’t work in water itself, though, I guess?

 

[peteK]

Can you hang the transducer over the side to test it?

 

[eddystone]

Some useful points here - BTW this is an Airmar P79 in hull transducer, i.e. the transducer is attached to the inside of the hull and signal passes through GRP hull.

1. The Airmar P79 is Raymarine recommended transducer; it's directly connected to the instrument with the supplied 14 metre lead so I can't see how the voltage to the transducer is an issue.
2. There is a tank/ body/locking ring; the idea is to align the markings on the tank that accord with the deadrise angle and then transducer body should be at correct angle. The instructions say maximum deadrise angle is 22 degrees whereas the actual where I was locating the tank was more like 28-30 degrees so the use of filler was to flatten the angle to be within specified limits. The top of the transducer body is meant to be dead level. Tank is fixed to hull with silicone sealant and filled with recommended poly glycol.
3. The Airmar is huge in diameter compared to the old one (Seafarer?) and there is actually only one place it can go - if you know Sadler 32 you will appreciate this.
4. I think my actual angles are about 3 degrees from level port-starboard axis and maybe 8 degrees off dead level fore-aft. Not perfect but as was mentioned sailing boats heel.
4. Did an experiment putting transducer into a bucket of water with boatyard manager monitoring instrument; it came to life and got a reading down to 0.5/0.6 metre ( less than 0.2 metre in bucket) when I held it as level as I could but tilting it slightly reading went up to 3/4 metres; the reading was however intermittent - gave a continuous reading for a bit and then would stop.

Possible explanations:

1) Transducer fault
2.) somewhere in the sandwich of hull lay up/previous layer of epoxy used to seal leaky tank not fully sanded off/new filler used to achieve minimum 22 degrees, there is a a barrier to transmission. Next step is to find some way of attaching a body of water to the outside of the hull underneath the tank location.

 

[Bodach na mara]

I read once that if the boat is out of the water over a hard surface, the sounder should still give a reading. As sound travels at a different speed in air as compared to water the reading will not be the distance between the hull and the hard. I hope that someone will soon tell us the correction factor. The point to take from this is that you can test the installation while the boat is ashore .

 

[Rappey]

Mine just flashes 0.0 when it's on a concrete scrubbing grid and the tide has gone out.
It is one meter from the ground.
150khz transducer.

 

[Bodach na mara]

Bang goes another theory.

 

[Rappey]

Bang goes another theory.

Mine is a very old but very good seafarer voyager which uses the same transducer as a nasa.
I can't speak for the much higher frequency units.

 

[MikeCC]

Doesn't the Sadler 32 have a foam core hull? No transducer will work through that - you need to cut through inner skin or go through-hull.

How was the old transducer mounted?

 

[Caraway]

Doesn't the Sadler 32 have a foam core hull? No transducer will work through that - you need to cut through inner skin or go through-hull.

How was the old transducer mounted?

Shame the OP didn't include all the information at the beginning.

 

[James_Calvert]

Doesn't the Sadler 32 have a foam core hull? No transducer will work through that - you need to cut through inner skin or go through-hull.

How was the old transducer mounted?

No.

The foam between the liner and the hull wasn't introduced until the 29. Then the 26 and 34. Never the 25 or the 32.

 

[James_Calvert]

If it's like mine, it will have had an internally mounted one, set in a moulded in tube.

 

[eddystone]

If it's like mine, it will have had an internally mounted one, set in a moulded in tube.

Yes I removed that as not compatible with new Raymarine instrument, but the diameter of new Airmar tank is about double that so had to move mounting point; also old one was directly over keel whereas Airmar recommendation is to mount to one side.