Survey Echo Sounder Transducers

Certain cleaners, gasoline, paint, sealants and other products may contain strong solvents, such as acetone, which can attack many plastics dramatically reducing their strength. Clean surface of transducer with a mild detergent only.

Threaded Stem Stuffing Tube        Stainless Steel Stuffing Tube

The transducer must be fully immersed in water and not subjected to air bubbles,
or turbulent water flowing across the radiating face.

Acoustic noise is always present and these sound waves can interfere with the operation of the transducer. While background noise cannot be controlled, carefully selecting the transducer mounting location can minimize the effect of vessel generated noise. The lower the noise level, the higher the echo-sounder gain setting that can be used.

· Background noise sources:

• Waves and air bubbles
• Fish and mammals
• Rain and hail
• Other vessels and shore

· Vessel generated noise sources;

• Propeller(s)
• Propeller shaft vibration
• Aerated and turbulent water flowing across the hull
• Machinery such as: engine, generator. gears and pumps
• Interference from other echo-sounders

On Displacement Hulls:

Carefully study the shape of the hull to determine the best transducer mounting location where;

• The transducer is away from the propeller and other sources of vessel generated noise.
• The water is smoothest with a minimum of turbulence and bubbles.

1. Locate the transducer about 1/3 aft LWL. Generally, this provides the best compromise between obtaining aeration-free water away from the bow and minimizing propeller noise.

Figure 1    <click to enlarge>

Figure 2        <click to enlarge>

2. Water near the keel can be quite aerated. Mounting it away from the keel can minimize interference with the transducer. Also, the deeper the transducer protrudes into the water, the less aeration.

• Near water intake or discharge openings.
• Behind strakes, fittings or hull irregularities.
• Near the keel
• Behind eroding paint (an indication of turbulence)

A fairing provides a level-mounting surface. Nearly all vessels have some deadrise angle at the transducer's mounting location. If the transducer is mounted directly to the hull, the sound beam would be tilted off the vertical at the same angle as the deadrise. If the deadrise angle at the mounting location exceeds 10° a fairing is strongly recommended (see above figures ).

• Vertically orients the sound beam by mounting the transducer parallel to the water.
• Inclines the transducer so the acoustic window is shaded from propeller noise. Generally a 3° incline angle is recommended (see Figure 1).
• Minimizes aerated water flowing over the transducer's face by mounting it deeper in the water (see Figure 2).
• Reduces drag by directing the water around the transducer.

Figure 3         <click to enlarge>

A backing block is mounted inside the hull to provide a level surface for tightening the threaded rods that hold the transducer in place. It is fabricated with the interior deadrise angle (see Figures 3 and 5). After cutting  the fairing the remaining section can be used as the backing block (see Figure 4).

1. Measure the deadrise angle of the hull at the selected location using a digital level, or bubble level and protractor (see Figure 2).

2. Tilt the band saw table to the measured angle and secure the cutting fence (see Figure 4).

Figure 4       <click to enlarge>

3. Place the fairing on the table so the cutting guide (if any) rests against the fence and the arrow will be pointing forward toward the bow when the fairing is installed.

Note: The blunt end always points forward toward the bow.

Warning.- Always wear safety goggles and a dust mask.

4. Recheck steps 1 through 3; then cut the fairing.

5. Shape the fairing to the hull as precisely as possible with a rasp or power tool.

Installation of the transducer requires a stuffing tube. Stuffing tubes are typically of two types; a threaded stem design which passes through the hull and is secured with a large nut and marine sealant, and tubes which are welded to the hull. Additionally, stuffing tubes must be compatible with the hull material.

Special care must be taken to insure these tubes will form a tight seal with the cable of your transducer. A stuffing tube for an aluminum hull must be fabricated from an aluminum alloy, electrolytically compatible with the hull plate.

Threaded Stem Stuffing Tube Installation

Figure 5a        <click to enlarge>

Figure 5b        <click to enlarge>

Threaded Rod Placement Dimensions

Figure 6        <click to enlarge>

1. Position the  fairing at the selected location being sure that the blunt end points forward toward the bow.  The distance between the two threaded rod holes for this sytle transducer equals 305mm (12.0") (see Figure 6).

The stuffing tube is located about half way between the threaded rods. Inspect the hull interior to ensure that there is clearance for the stuffing tube and that no cables, ribs or struts will interfere. Mark the site for the threaded rods and stuffing tube.

2. From inside the hull, drill a 3mm (1/8") diameter pilot hole for the stuffing tube. However, if there is a hull irregularity near the selected mounting location, drill from the outside. If the pilot hole is drilled in the wrong location, drill a second hole in a better location. In a fiberglass hull apply masking tape on the outside of the hull over the incorrect hole and fill it with epoxy. For wooden hulls fill the incorrect hole with marine sealant; in metal weld the hole closed.

3. At the pilot hole, drill a 28mm (1-1/8") diameter hole (for a 1" tube) from the outside perpendicular to the hull surface for the stuffing tube. Remove all burrs and clean the area around the hole, inside and outside, to ensure that the marine sealant will adhere properly. A backing block may be required under the flanged nut to ensure that it can be tightened against a flat surface.

4. Drill two l0mm (1-3/32") diameter holes through the hull and backing block for the threaded rods. Care must be taken to ensure that the two rods are parallel to the keel to reduce drag.

5. Install the stuffing tube first. Remove the nuts, washers and bushing from the stuffing tube. Select a marine grade sealant and follow the directions for its use. Apply a 3mm (1/8") thick layer of marine sealant to the stuffing tube from the flange that makes contact with the outside of the hull to where the flanged nut will be tightened inside the hull. This will seal the hull and hold the nut securely in place (see Figure 7).

Push the stem of the stuffing tube through the hull and fasten the flanged nut inside. On a fiberglass or metal hull, tighten this nut securely. On an aluminum hull use the spacers to isolate the stuffing tube from the hull, being sure to apply marine sealant to the spacers as well. If the hull is wood and has been out of the water for a prolonged period, it is suggested that the flanged nut be hand tightened only. Wood will swell after the boat is in the water and exert considerable pressure on the stuffing tube hardware. After the hull has expanded, tighten the nut securely.

          Figure 7    <click to enlarge>

Airmar steel stuffing tubes can be installed with or without welded conduit. Some approval authorities require that the transducer cable be encased in conduit. In such an installation, the conduit is welded to the steel stuffing tube (see Figure 8). In welded conduit installations the stuffing tube must have the compression nut tightened from outside the hull. Airmar stuffing tubes are reversible allowing the compression nut to be tightened from outside (see Figure 8) or inside the hull (see Figure 9).

1. Position the Airmar fairing at the selected location being sure that the blunt end points toward the bow. (the transducer used for this example is symmetrical.) The distance between the two threaded rod holes equals 305mm (12.0") (see Figure 6).

The stuffing tube is located about half way between the threaded rods. Inspect the hull interior to ensure that there is clearance for the stuffing tube and that no cables, ribs or struts will interfere. Mark the site for the threaded rods and stuffing tube on the outside of the hull.

2. Drill or cut (with a cutting torch) a 38mm (1-112") diameter hole (for this example) in the hull for installation of the stuffing tube. Grind the area around the hole, inside and outside, removing all burrs.

3. Drill two l0mm (13/32') diameter holes (for this example) through the hull and backing block for the threaded rods. Care must be taken to ensure that the two rods are parallel to the keel to reduce drag.

4. Install the stuffing tube first. Remove the compression nut, washers and compression bushing from the stuffing tube. Insert the tube into the hull and weld it in place
(see Figure 8 or 9).

Figure 8a <click to enlarge>

Figure 8b <click to enlarge>

Figure 9    <click to enlarge>

Exterior Mount

1. Screw a nut and slide a washer onto each threaded rod. Position the nuts 86mm (3.38") from the rod ends (see Figure 6). Following the sealant manufacturer's directions, apply marine sealant to the threaded rods where the nut will seat against the fairing. Slide the threaded rods through the fairing (see Figure 8). The rods will extend above and below the fairing.

2. Apply a 3mm (1/8') thick layer of marine sealant to the surface of the fairing that will make contact with the hull and the two threaded rods that will pass through the hull. Place the fairing against the hull, pushing the rods through the hull. With a person stationed inside the vessel position the backing blocks on the rods and secure them with a stainless steel washer and nut (see Figure 8). Tighten the nuts with a torque wrench using a force not exceeding 7 N-m (5 ft-lb). Remove excess sealant.

Note: If a wood fairing is used, hand tighten the nuts only Allow the fairing to swell and then tighten to 4 N-m (3 ft-lb).

Caution: Never pull, carry or hold the transducer by its cable as this may sever internal connections.

3. Thread the transducer cable through the stuffing tube to the inside of the hull. Allow a service loop in the cavity of the fairing so there is no tension applied to the cable (see Figure 5, 8 or 9).

4. Mount the transducer to the fairing by sliding a rubber washer and stainless steel washer onto each threaded rod and securing it with a nut (see Figure 8).Tighten the nuts with a torque wrench using a force not exceeding 4 N-m (3 ft-lb).The rods should extend a minimum of 3 threads beyond the nut when tightened. Apply marine sealant to the exposed threads.

5. Plug the mounting holes to minimize turbulence on the surface of the transducer using the white, foam, plug material. Cut the foam to length so that, when installed, each plug is recessed 5mm (3/16") below the surface of the housing. Push these foam plugs into the holes and use marine sealant to fill the holes even with the transducers surface. Remove excess sealant to ensure smooth water flow over the transducer.

6. Seal the cable by sliding the washer, rubber compression bushing, washer, and the compression nut down the transducer cable to the stuffing tube (see Figure 7). Make sure the rubber bushing fits securely into the machined lip of the tube. Tighten the compression nut. Remove all excess sealant inside the hull.

7. Route the cable to the echo-sounder being careful not to tear the cable jacket when passing it through the bulkhead and other parts of the boat. To reduce electrical interference separate the transducer cable from other electrical wiring and the engine. Coil any excess cable and secure it in place with zip-ties to prevent damage.

8.Wire the transducer to the Echosounder per diagram:  Bathy-500MF or   Bathy-1500.

Warning: Never install a transducer and leave the boat in the water unchecked for several days.

When the boat is placed in the water, immediately check around the bolts that fasten the transducer to the hull and the stuffing tube for leaks. Note that very small leaks may not be readily observed. It is best not to leave the boat in the water unattended for more than 3 hours before checking it again. If there is a small leak, there may be considerable bilge water accumulation after 24 hours (probably not enough to cause water damage). If a leak is observed, repeat the bedding and installation procedures immediately.

Surfaces exposed to salt water must be coated with antifouling paint.

Use water-based antifouling paint only. Never use ketone-based paints as it can attack many plastics damaging the transducer. Apply antifouling paint every six months, or at the beginning of each boating season.

Aquatic growth can accumulate rapidly on the transducer's surface reducing its performance in weeks. Clean the surface with a soft cloth and mild household detergent. If necessary, use a stiff brush or putty knife to remove the growth taking care to avoid making scratches. if fouling is severe , wet sand with #220 or finer grade wet/dry sandpaper.

Inspect the cable periodically for kinks, abrasions and cuts. Repair any damage using an approved waterproofing cable repair system. Inspect connections for indications of corrosion.

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