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Old 09 March 2002, 22:56   #21
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Nick,

I will be interested to know what info you get back from Airmar.


Dave,

Thanks for the info - all is now clear and explains why the FF goes doolally when going astern.
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Old 10 March 2002, 08:36   #22
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Sorry for not explaining Araldite! Basically by using this 'epoxy resin', you are bonding the transducer to the hull, so that it all becomes ‘one’. You don’t need to drill any holes but it does need to be down to the inside of the solid bottom of the hull, (hence in the sump). As has been said, provided there is no air, bubbles or otherwise, then the ultra sound signal from the transducers will penetrate the 'glue' and hull without hindrance and return with its echo. I had so many air bubbles form at the transom when on the plane that when I had it mounted there, it lost its signal all together. Now, with the thru the hull placing, I do sometimes still loose the pretty little picture of the sea-bed and the little fish shapes, but it does continue to return a depth. If it's bonded like that, then I don't see why any water is needed in the sump as it won’t even get to go between transducer and hull. Other than perhaps to keep the transducer cool?

Interesting that you used silicon sealant, Dave. As you say, the instructions say it’s a no-no. Any 'glue' you use should be solid and rigid to allow the signal to pass. The wobbliness of silicon sealant should attenuate the signal. Having said that, if your only using a thin sliver between transducer and hull, (i.e. push hard) and then pack around the side and top for the 'glue it not to move' factor, then that may well work fine. (Well obviously it does cos you've done it!) I wish now I hadn't read the instructions and done that myself. Much easier to remove!

Anyway, if 'jelly-like' substances don't let ultrasound through, how come they stick it on pregnant women’s stomachs in the maternity ward? Perhaps our resident baby expert, John Kennet would like to comment on that one?

(PS. Dave, Thanks for all the private info on your boats)
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Old 10 March 2002, 14:12   #23
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The Airmar link I posted, is the What's New page for Airmar. The unit of interest to me is the "new adjustable in hull transducer" which bonds to the inside of the hull and rotates to the particular deadrise angle. The transducer is instantly removable from the rotating housing which is handy for storage. I think this leaves one with more options than a permanently bonded transducer. In fact this unit would not need to be in the aft sump where it could be impacted by other equipment or someone's foot. It could be hidden anywhere in the aft portion of the boat.

Again, the link is:
http://www.airmar.com/whatsnew/f_whatsnew.htm


NR
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