practical
Echo sounder and speed log transducers
E
cho sounder transducers can be fitted in different ways. Best performance is
with through-hull mounting but this obviously involves drilling a hole in the
hull. With a speed log impeller you’ve no option but to do this.
Another sounder choice is to glue in a plastic tube which is filled with castor oil and
the transducer fitted with its face in the oil. There’s no hull hole and the transducer
is easily removed, but oil can seep through an imperfect bond and there’s a loss of
signal strength through the fabric of the hull (though for most this is rarely an issue).
The most common method nowadays is to stick the transducer directly to the
inside of the hull using car body filler. Again, there’s no hole in the hull but there
is the same loss of performance and it is difficult to remove the transducer.3
The transducer and bracket was
then offered up and the bracket’s
position marked on the adjacent stringer.6
Body filler can start to harden fairly
quickly, so without hanging about
the bracket (previously coated with wood
sealer) was screwed into place.9
Having double-checked the position
of the speed log paddle wheel
transducer, a pilot hole could be drilled.12
A similarly generous bead was also
run into the groove of the interior
securing nut.4
Fixing holes were drilled into the
stringer so the bracket could be
screwed into place accurately when ready.1
Find a
suitably clear
area under the
hull and measure
its position inside.
Abrade the area
with glass paper
and wash with
acetone to ensure
a good bond.7
The transducer was slipped into the
bracket and the face properly
immersed into the filler with a twisting
motion to help expel air bubbles.10
Having
checked
under the hull that
the pilot hole was
indeed in the right
place, a hole saw
of appropriate
diameter was used.
Dust was then
vacuumed out and
the area cleaned
with acetone.13
The fitting is placed through the hull
from the outside, the nut is run down
the thread and then gently tightened.2
I don’t like to rely just on body filler
to secure the transducer so I made a
simple ply bracket to hold the top end.5
The body
filler was
mixed up
according to
the maker’s
instructions
and a large
dollop was
trowelled onto
the abraded
and cleaned
spot in the
bilge.8
As the filler began to cure I tidied it
up using a spatula to scrape off the
excess. I then left it alone to fully cure.11
A generous bead of silicone sealer
was applied around the flange of the
exterior fitting.