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Airmar M260 Question

Old 11-04-2004, 05:44 PM
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Default Airmar M260 Question

Is there any reason that I might want to take the transducer out of the boat for the winter? It gets very cold here and our boat it outside and exposed. I know the oil is not going to be a problem, or is it? Just for background, I've seen it stay below zero for a month here and 20~30 below is gonna happen three or four nights per winter.

Thom
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Old 11-04-2004, 06:36 PM
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Default RE: Airmar M260 Question

I don't think so but a couple items to ponder

1st how hard is it to remove??

2nd if it's in the Bilge would hanging a bare light bulb say 100 watt keep the bilge heated enough
to prevent freezing???

3rd would you sleep better???


answer yes to number 3 maybe to 1 and yes to 2 and we are right back at the starting point!!
if it's easy to pull... pull it !!!

John
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Old 11-04-2004, 07:30 PM
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Default RE: Airmar M260 Question

Just leave it. If you followed directions and mounted it in teh in-hull tank filled with mineral opil or orange anti-freeze, you are safe to well below 0.

Harry
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Old 11-04-2004, 09:07 PM
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Default RE: Airmar M260 Question

I personally can't think of a reason to take it out BUT do be sure the bilge is dry because water freezing could crush/damage the housing (I've seen it happen to the cheaper plastic P-79 transducers.)
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Old 11-04-2004, 09:38 PM
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Default RE: Airmar M260 Question

I have no idea as to your question, but I do feel sorry for you with that winter weather descripion. I used to live about 90 miles north of you. How did that great paint job hold up through the season?

Airslot
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Old 11-04-2004, 09:44 PM
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Default RE: Airmar M260 Question

Just thought of the solution to your problem. Take a small tupperware container of whatever fluid you have used (mineral oil?) and stick it in the deep freeze, if you have one, for a week and see if it froze. Regular freezer might work. At least you can find out before it happens outside.

Airslot
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Old 11-19-2004, 08:17 AM
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Default RE: Airmar M260 Question

An important consideration is the differences in thermal expansion coefficients (TEC) of the various components that make up the transducer. I do not know the numbers (without looking them up) but my gut tells me that there is a significant difference of TECs between the ceramic, urethane, and epoxy adhesives. These assorted items could de-bond at extreme temperatures. Also, if there is no mention of this issue in the transducer owners guide you could call (or email) the transducer manufacturer. E Fitz.
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Old 11-19-2004, 10:46 AM
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Default RE: Airmar M260 Question

That is a very interesting point. I suspect that the plastics in the system are pretty dimension stable with temperature compared to the few metal parts (the lid of the thank from which the transducer is suspended in the tank for instance), but delamination at the interface would certainly be a possiblilty with differential expansion, I would think.

My transuducer is easily accessed and shouldn't take more than 15 minutes to remove completely (the hardest part will be pulling out the cable and even that is pretty easy in my boat). I'm going to pull it. At the price one of these things its just not worth taking a chance, even though I never gave it a thought with any other tansducers over the years. Who knows?

Thom
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Old 11-19-2004, 12:20 PM
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Default RE: Airmar M260 Question

In constructing a low Q transducer design (like the 200kHz in M260) the common (economical) approach is to bond an acoustic matching layer of appropriate thickness directly to the silver electroded surface of the ceramic element. The bonding agent is often a very thin layer of epoxy and the adhesive is cured at some elevated temperature. Therefore, at "room temperature", there is already some residual stresses due to the differential TECs between the ceramic and bonding agent. At extremely low temperatures there would be even more stress, eventually something will give, but what? If the electrode is primed, failure can occur because the silver electrode pulls away from the ceramic, if un-primed you can get a "clean" break between the electrode and matching layer. I agree that in other "non-low Q" designs this is not the case because the urethane encapsulants are flexible enough stretch and compress at temperature extremes. And some "low Q" designs use exotic (expensive) ceramic that does not require the matching layer. E Fitz.
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Old 11-19-2004, 03:20 PM
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Default RE: Airmar M260 Question

Why take the chance, if it only takes 15 minutes a year to pull it.JMO
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