Airmar P79S - Testing and Selecting the Mounting Location; Establishing a Performance Baseline; Testing the Location Inside the Hull

Testing the Selected Mounting Location
Establishing a Performance Baseline
The results of this test are used as a basis of comparison to
determine the best in-hull location for the transducer.
1. Take the boat to the maximum depth in which you will be
operating the echosounder. If deep water is not available, find a
location with at least 30m (100').
2. Connect the transducer to the echosounder.
3. Tape the transducer to a pole with the cable side up. Hold it
over the side of the boat with the active face fully submerged
and parallel to the water surface (Figure 2).
4. Observe the echosounder’s performance and the depth reading.
Testing the Location
While the boat is at the same site (depth of water), test the
transducer inside the hull at the mounting location. Use one of the
methods below:
A.For a location near the stern and a minimal deadrise angle—
Clean away any build-up of dirt and/or grease using detergent
or a weak solvent such as alcohol. Place the transducer against
the hull and allow bilge water to cover the surface where they
touch (Figure 3-A).
B.For a moderate deadrise angle—If the hull surface is not
smooth, grind it with a disc sander. Place the transducer inside a
thin plastic bag. Partially fill the bag with water and close it tightly
with a cable tie. Wet the surface of the hull and press the active
face of the transducer against it through the bag (Figure 3-B).
C.For any location—If the hull surface is not smooth, grind it with a
disc sander. Coat the active face of the transducer with a water-
based lubricant (such as K-Y
®
jelly). With a twisting motion, press
the face firmly against the hull (Figure 3-C). After testing, wipe all
traces of the lubricant from the transducer’s face.
Observe the echosounder’s performance, and compare it to the
baseline. Look for a stable depth reading that is similar to the
baseline. Compare the thickness and intensity of the bottom trace.
If the performance is close to the baseline, this is a good mounting
location. Remember, some energy is lost transmitting through the
hull. If the test reading differs markedly from the baseline, you will
need to find another location to install the transducer.
NOTE: Fiberglass hull—If there is no reading or it is erratic, the
transducer may be positioned over coring which is absorbing the
acoustic energy. Choose another location. If no other location is
available, check with the boat manufacturer to be certain coring is
present before proceeding with the instructions for “Installation in
a Cored Fiberglass Hull” (page 4).
2
inboard
Figure 1.
pressure waves
1/3
full keel sailboat
displacement hull
(6-12")
fin keel sailboat
150-300mm
LWL
Best location for the transducer
(Load Waterline Length)
stepped hull
planing hulls
Boat Types (Figure 1)
• Displacement hull powerboat—Locate 1/3 of the way back
along the LWL and 150–300mm (6–12") off the centerline. The
side of the hull where the propeller blades are moving
downward is preferred.
• Planing hull powerboat—Mount well aft, on or near the
centerline, and well inboard of the first set of lifting strakes to
ensure that the transducer is in contact with the water at high
speeds. The side of the hull where the propeller blades are
moving downward is preferred.
Outboard and I/O—Mount just forward of the engine(s).
Inboard—Mount well ahead of the propeller(s) and shaft(s).
Stepped hull—Mount just ahead of the first step.
• Fin keel sailboat—Mount to the side of the centerline and
forward of the fin keel 300–600mm (1–2').
• Full keel sailboat—Locate amidships and away from the keel
at the point of minimum deadrise angle.
Figure 2. Establishing a performance baseline
Figure 3. Testing the transducer at the selected location
AB C
active face
Copyright © 2005 - 2016 Airmar Technology Corp.
Copyright © 2005 Airmar Technology Corp. Copyright © 2005 Airmar Technology Corp.
outboard and /IO