Airmar P52 with Plastic Release Bracket 20-039 - Manual (Page 4)

4
Setting the Bracket Release Point
CAUTION: Never compress the top of the spring below the tab,
because the bracket will be locked in place and will not release.
When the spring is even with the tab, the release force is
maximum at about 100lb. (450N).
CAUTION: Do not set the bracket to withstand more force than
the minimum required to hold the sensor in the "down" (operating)
position, since this increases the chance that the bracket will not
release when the sensor is struck.
There is considerable force on the bracket during normal operation. The
amount of force is proportional to the drag which is created by the:
• Sensor—shape, size, weight, and amount of projection below the
transom.
• Speed—the square of the speed of the boat.
A larger and heavier sensor creates more drag as does a higher boat
speed. For example, the drag at 40kn (46MPH) is four times that at 20kn
(23MPH). The correct bracket release setting has been found when the
sensor remains in the “down” (operating) position under normal operating
conditions.
The factory setting is 40lb. (180N). The adjustment screw may need
tightening if the top speed of the boat is more than 30kn (34MPH).
Gradually increase the boat speed and observe the echosounder. When
the bracket releases, there will be an instantaneous loss of echo. If the
bracket releases before reaching top boat speed, reset the bracket in the
“down” (operating) position and turn the adjustment screw clockwise one
or two full turns (see Figure 9). Repeat the test until the desired result is
obtained.
NOTE: One turn equals 10lb. (45N).
Testing on the Water
1. Become familiar with your echosounder’s performance at a speed of 4kn
(5MPH).
2. Gradually increase the boat speed and observe the gradual decline in
performance due to turbulent water flowing over the transducer’s active
surface.
3. If the decline in performance is sudden (not gradual), identify the boat
speed at which the onset occurred. Return the boat to this speed, then
gradually increase speed while making moderate turns in both directions.
4. If the performance improves while turning to the side on which the
sensor is installed, the transducer’s position probably needs
adjustment. It is probably in aerated water.
To improve performance, try the following one at a time in the order
given.
a. Increase the sensor’s angle in the water.
b. Move the sensor deeper into the water in increments of 3mm (1/8").
c. Move the sensor closer to the centerline of the boat.
Fill unused screw holes with marine sealant.
NOTE: High-speed operation [above 35kn (40MPH)] may require less
projection in the water to improve performance and reduce the chance
that water pressure will cause the bracket to release.
Maintenance, Repair, & Replacement
Speed Sensor
Remove the paddlewheel assembly before beaching, trailering, or hauling
the boat, since these are the main causes of speed sensor breakage.
Cleaning
Clean the transducer’s surface with a Scotch-Brite® scour pad and mild
household detergent taking care to avoid making scratches. If the fouling
is severe, lightly wet sand with fine grade wet/dry paper.
If the paddlewheel becomes fouled or inoperable, unsnap the paddlewheel
assembly from the main housing for cleaning. Severe cases may require
removal of the paddlewheel. Using a small screwdriver, remove the
paddlewheel shaft retainers. (If a retainer is lost, a dab of RTV caulk on the
end of the shaft will secure it.) If necessary, use a stiff brush or putty knife to
remove the growth being careful to avoid scratching the transducer’s face.
Wet sanding is permissible with fine grade wet/dry paper.
Sensor Replacement & Parts
The information needed to order a replacement sensor is printed on the
cable tag. Do not remove this tag. When ordering, specify the part
number, date, and frequency in kHz.
Replace broken or worn parts immediately. The speed sensor shear pins
are designed to fracture upon impact. The water-lubricated paddlewheel
bearings have a life of up to 5 years on low-speed boats [less than 10kn
(11MPH)] and 2 years on high-speed vessels. Some depth/temperature
units can be upgraded by adding a speed sensor.
For a replacement paddlewheel carrier without a cable, order the Snap-In
Paddlewheel Carrier 33-105 (see Figure 11); for an assembly with a
cable, order Transom Paddlewheel Kit 33-110 (see Figure 12) from your
marine dealer or echosounder manufacturer.
Airmar offers a stainless steel Kick-Up Bracket 20-035-2 which rotates the
sensor up when excessive force is applied. This bracket allows the user to
manually release the sensor to protect it when trailering, beaching, or
hauling the boat. Both brackets use the same mounting holes.
Obtain parts from your instrument manufacturer or marine dealer.
Gemeco Tel: 803-693-0777
(USA) Fax: 803-693-0477
email: [email protected]
Airmar EMEA Tel: +33.(0)2.23.52.06.48
(Europe, Middle East, Africa) Fax: +33.(0)2.23.52.06.49
email: [email protected]
tab
Do not compress
adjustment
spring
top of spring
screw
Figure 9. Bracket
shear
Figure 10. 33-105
shear pins (4)
Figure 11. 33-110
pins (4)
release adjustment beyond tab
Copyright © 2000 ­ 2011 Airmar Technology Corp. All rights reserved.
AIRMAR
®
TECHNOLOGY CORPORATION
35 Meadowbrook Drive, Milford, New Hampshire 03055-4613, USA
www.airmar.com