[Public-list] depth sounder puzzle

[Meinhold, Michael J.]

Maybe you should have tossed a hook in - it might be a school of fish! 
Really though, anything that would give you a 2 foot reading you would
also notice by other senses. 3 foot weeds would have slowed you down.


I suspect some other kind of interference. I presume your transducer is
about 2 feet underwater? So these readings are zero at the transducer?
Bubbles are a possiblity if you can explain why the transducer would be
in bubbles right there. It's possbile that a certain maneuver would
entrain air and bring it down the transducer to give a zero, displayed
as 2 feet. 

You could do some experimentation and report back - I would be
interested at least!

Mike
Rinn Duin #272


-----Original Message-----
From: public-list-bounces at lists.alberg30.org
[mailto:public-list-bounces at lists.alberg30.org] On Behalf Of Gordon
White
Sent: Monday, June 25, 2007 5:48 PM
To: public-list at lists.alberg30.org
Subject: Re: [Public-list] depth sounder puzzle

I was out this weekend for the first time this season and everything
seemed to work o.k - depth sounder, speed meter, auto pilot, etc. The
depth sounder has always been a foot on the conservative side - reads
six feet where there are actually seven from the surface. I checked this
in the slip with a pvc pole with a small plate on the end so it does not
go down in the mud and mislead me - Everything was fine.

    The depth readings just outside the slip were fine - 4.5 to 6 feet
(actual depths 5.6-7) but about 150 yards down the creek the depth
sounder began reading 1.5, 2. 1.5 feet. etc. Obviously it's not that
shallow or I'd have been pretty hard aground. The actual dept in that
stretch are 5.5 - 8 feet at that state of the tide.

    The shallow readings continued for 3/8 of a mile, then went back to
what they should be and remained o.k. all day until I rerturned and in
the same stretch of my creek (Moore's Creek off the Piakatank Rover)  I
got extremely shallow readings in the same stretch. It read accurately
when I got back in my slip.

Anyone have any suggestions? At first I thought it was a glitch in the
instrument, but now I doubt that.

- Gordon White
Brigadoon II
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