Olive oil bath for a transducer

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CalicoJack

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When we used our boat last week, I noticed that the display on the echosounder, actually its a fish finder, was very grainy, to the point that it was difficult to make out the numbers. I thought that this was a sign that the instrument was on its way out, it is quite old after all. Consequently I have ordered a new one, however, I’m now wondering whether all that’s happened is that the olive oil in the bath has solidified and that is causing the problem. As you will have worked out the transducer is not mounted outside the hull, but instead transmits through the hull, using olive oil as a medium.

Any thoughts?
 
CalicoJack said:
When we used our boat last week, I noticed that the display on the echosounder, actually its a fish finder, was very grainy, to the point that it was difficult to make out the numbers. I thought that this was a sign that the instrument was on its way out, it is quite old after all. Consequently I have ordered a new one, however, I’m now wondering whether all that’s happened is that the olive oil in the bath has solidified and that is causing the problem. As you will have worked out the transducer is not mounted outside the hull, but instead transmits through the hull, using olive oil as a medium.

Any thoughts?
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The medium through which the signal passes will not affect the quality of the display, just the depth reading. A liquid or solid medium will give a reading, an air medium will give no reading. If you want to satisfy yourself, put the transducer in a jug of water then see how the display registers when you take it out of the water.

Www.solocoastalsailing.co.uk
 
CalicoJack said:
When we used our boat last week, I noticed that the display on the echosounder, actually its a fish finder, was very grainy, to the point that it was difficult to make out the numbers. I thought that this was a sign that the instrument was on its way out, it is quite old after all. Consequently I have ordered a new one, however, I’m now wondering whether all that’s happened is that the olive oil in the bath has solidified and that is causing the problem. As you will have worked out the transducer is not mounted outside the hull, but instead transmits through the hull, using olive oil as a medium.

Any thoughts?
Click to expand...

Twisterowner said:
My only thought is that I seem to remember reading that castor oil is used.
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I think olive oil, and other vegetable cooking oils may go off / rancid / claggy

Castor oil does not ... at least mine has not in 40 years. It is what was specified by Seafarer all those years ago.
 
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On my NASA one I used cooking oil which was readily available and cheap. It didn't seem to go off. My Raymarine one didn't have an oil bath.
I don't think the medium will affect the display except whether it's on or off.
 
crocks said:
Blob of silicone
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Silicone and such like are expressly advised against by Airmar, who make most of the transducers. It absorbs some of the energy from the signal and gives inaccurate readings.

Airmar used to include instructions for fixing to the hull without using a batch. They were, make a dam with plasticine or similar, pour slow drying epoxy into the dam until it is level This counter acts the hull deadrise. When it's dry, add a small layer of epoxy and push the transducer into the epoxy with a twisting motion, to expel any air.
 
CalicoJack said:
When we used our boat last week, I noticed that the display on the echosounder, actually its a fish finder, was very grainy, to the point that it was difficult to make out the numbers. I thought that this was a sign that the instrument was on its way out, it is quite old after all. Consequently I have ordered a new one, however, I’m now wondering whether all that’s happened is that the olive oil in the bath has solidified and that is causing the problem. As you will have worked out the transducer is not mounted outside the hull, but instead transmits through the hull, using olive oil as a medium.

Any thoughts?
Click to expand...

Olive Oil does harden after a while it goes to a granular sort of mush it also smells very sour, as someone else said perhaps castor or silicone
 
I tried to obtain castor oil a few years ago, but it is difficult to buy as it causes abortion in pregnant females... I used veg oil, that's 8 years ago and it's still fine
 
A chemists view:

One of the problems with vegetable oils is that - especially nowadays - they are often high in "polyunsaturates". Whilst this is no doubt good for eating, the polyunsaturates do readily oxidise in air to form gums. Olive oil is not high in polyunsaturates, so you might get away with it, especially if it is (ironically) a cheaper brand.

Worst of all would be a drying oil like linseed oil, or Danish Oil, as they oxidise readily in contact with air, forming a film.

Caster oil is not a "drying oil" as it does not contain these polyunsaturates, and so will stay liquid in contact with air. However, I think a mineral oil would be better, such as liquid paraffin or even "baby oil", which is the same stuff with a bit of perfume added.

i think that there might be issues with silicone oil, with some transducers - not because of the transmission of ultrasound, but on its effect on some plastics, which it can soften.
 
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