Cannot get a Depth Reading on NASA Clipper!

AlanOB

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This has caused me so much hassle this summer. When my Navman packed in I replaced it with a NASA Clipper duet. The depth transducer is working fine when I hang it over the edge of the boat but I cant get a constant reading wyhen it is bonded to the hull. I have tried sika, silicone and now I have it in the fixing kit using the oil. I get a very high reading (30m or higher, and then it decays down gently to eventually give me an accurate reading (lets say 4m or 5m). Sometimes it goes back up to a high rwading before decaying to a propioer reading, other times it settles down after about half a minute and gives me a few seconds of a good reading. It is a GRP hull and I have used this type of transducer before. It seems unrelated to electrical interference as I have tested it in different locations and keeping the cable away from all other interference. Also, it is away from the keels, located in the same position as the last sounder. Is the sounder too weak to get a signal or is there something else wrong here? I read about anti-foul causing problems but i use Cruiser Uno single-season antifoul and it shouldnt cause this sort of problem...or should it? Anyone had this problem before? Im reluctant to get the thru-hull kit as it look all a bit messy.
 

yachtorion

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What sort of GRP hull? Is it cored? If so, what with?

Given it works fine over the side, unless you've had air bubbles under it each time you've mounted it you've basically ruled pretty much everything out part from hull interference...
 
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VicS

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This has caused me so much hassle this summer. When my Navman packed in I replaced it with a NASA Clipper duet. The depth transducer is working fine when I hang it over the edge of the boat but I cant get a constant reading wyhen it is bonded to the hull. I have tried sika, silicone and now I have it in the fixing kit using the oil. I get a very high reading (30m or higher, and then it decays down gently to eventually give me an accurate reading (lets say 4m or 5m). Sometimes it goes back up to a high rwading before decaying to a propioer reading, other times it settles down after about half a minute and gives me a few seconds of a good reading. It is a GRP hull and I have used this type of transducer before. It seems unrelated to electrical interference as I have tested it in different locations and keeping the cable away from all other interference. Also, it is away from the keels, located in the same position as the last sounder. Is the sounder too weak to get a signal or is there something else wrong here? I read about anti-foul causing problems but i use Cruiser Uno single-season antifoul and it shouldnt cause this sort of problem...or should it? Anyone had this problem before? Im reluctant to get the thru-hull kit as it look all a bit messy.

A good idea is to seek ot a suitable location by temporarily mounting it on a dollop of Blu Tack or chewing gum or even holding with a bag of water between it and the hull.

Important when mounting on an adhesive sealant such as Sikaflex that no air is trapped.

My Seafarer transducer in mounted in oil There is 30 years worth of antifouling on the outside of the hull causing no problems. Not that I often switch it on.
 
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ghostlymoron

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The NASA depth instrument is the least troublesome of their range and mine worked without problems mounted in a tube with cooking oil. With sika/epoxy there's always a chance of air under the transducer which I think is probably your problem. Also, you should try calling the NASA techies - I have found them very helpful and they know their products well.
 

Burnham Bob

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Had the same problem with the old boat with exactly the same echo sounder. Eventually made up a wooden support and positioned the transducer in the bilges where it was in contact with the hull and always in a bit of water. Worked fine. No idea why but you could try it
 
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