Simrad 50-200 COMBI D Installation Manual

Installation manual

50/200 Combi D Echo sounder transducer

www.simrad.com

M A X I M I Z I N G Y O U R P E R F O R M A N C E A T S E A

851-165216 / Rev.A

Simrad 50/200 Combi D

Transducer

Installation manual

About this document

Rev Date Written by Checked by Approved by

Rev.A

19.05.05 RBr OBG OBG

Original issue.

copied without prior permission from Simrad AS. The information contained in this document is subject to change without prior notice.

Simrad AS shall not be liable for errors contained herein, or for incidental or consequential damages in connection with the furnishing, performance, or use of this document.

The equipment to which this manual applies must only be used for the purpose for which it was designed. Improper use or maintenance may cause damage to the equipment or injury to personnel. The user must be familiar with the contents of the appropriate manuals before attempting to operate or work on the equipment. Simrad AS disclaims any responsibility for damage or injury caused by improper installation, use or maintenance of the equipment.

If you require maintenance on your Simrad equipment, contact your local dealer. You can also contact Simrad using the following e-mail address: fish-support@simrad.com

INTRODUCTION

Purpose

The purpose of this installation manual is the provide the basic information required to install the 50/200 Combi D echo sounder transducer.

Note that although drawings are provided to explain the installation principles, the installation shipyard must provide the final drawings required to fit each individual vessel. Also, when applicable, the installation shipyard must have the drawings and installation approved by the proper authorities.

Transducer order no: KSV-203005 A cable gland kit for steel hulls is included with the delivery.

Other cable glands must be ordered separately.

Installation manual

Transducer installation

The next chapter in this manual provides generic guidelines for transducer installation. The drawings specific for the 50/200 Combi D transducer are located in the Drawing file.

Technical specifications

Refer to the 50/200 Combi D product specification, Simrad document number 855-164211.

851-165216 / Rev.A

Simrad 50/200 Combi D Transducer

INSTALLATION

This chapter provides general installation guidelines for transducer installation. The following topics are described:

• Transducer location

• Mounting (different methods are shown when applicable)

• Cable glands

• Steel conduit for transducer cable

• Handling and maintenance

• Approved anti-fouling paints

The information in this chapter must be regarded as general guidelines and recommendations only. The installation shipyard must design and manufacture installation hardware to fit each individual vessel.

Whenever required, the installation shipyard must also have the installation approved by the applicable maritime authorities.

851-165216 / Rev.A

Installation manual

Transducer location

General

A single answer to the question where to locate the transducer cannot be given. It depends very much on the vessel’s construction. However, there are some important guide lines.

Go deep

The upper water layers of the sea contain a myriad of small air bubbles created by the breaking waves. In heavy seas the uppermost 5 to 10 metres may be air-filled, with the highest concentrations near the surface. Air bubbles absorb and reflect the sound energy, and may in worst cases block the sound transmission totally. Therefore, mount the transducer at a deep position on the hull.

Consider the situation when the vessel is unloaded, and when it is pitching in heavy seas. The transducer must never be lifted free of the water surface. Not only will the sound transmission be blocked, but the transducer may be damaged by slamming against the sea surface.

Another reason to go deep is cavitation in front of high power transducers. Cavitation is the formation of small bubbles in the water due to the resulting local pressure becoming negative during parts of the acoustic pressure cycles. The cavitation threshold increases with the hydrostatic pressure.

Vessel heave

Heave is the up and down movement of the vessel. It disturbs the echo traces in the echogram, so that a flat bottom is displayed as a wave. A transducer location in the middle of the vessel minimises the influence of vessel roll and pitch.

Noises from protruding objects on the hull

Objects protruding from the hull, such as zinc anodes, sonar transducers or even the vessel’s keel, generate turbulence and flow noise. Also holes and pipe outlets are noise sources. They may act as resonant cavities amplifying the f low noise at certain frequencies. Do not place an echo sounder transducer in the vicinity of such objects, and especially not close behind them.

For the same reason, it is very important that the hull area around the transducer face is as smooth and level as possible. Even traces of sealing compound, sharp edges, protruding bolts or bolt holes without filling compound will create noise.

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Simrad 50/200 Combi D Transducer

Boundary water layer

When the vessel forces its way through the sea, the friction between the hull and the water creates a boundary layer. The thickness of the boundary layer depends upon vessel speed and the roughness of the hull. Objects protruding from the hull, and dents in the hull, disturb the flow and increase the thickness of the boundary layer. The flow in this boundary layer may be laminar or turbulent. A laminar flow is a nicely ordered, parallel movement of the water. A turbulent flow has a disorderly pattern, full of eddies. The boundary layer increases in thickness when the flow goes from laminar to turbulent. The figure below illustrates the boundary layer of a vessel moving through the water.

Boundary water layers: (A) = Turbulent flow (B) = Laminar flow (C) = Air bubbles in the water

Furthermore, air bubbles in the sea water are pressed down below the hull and mixed into the boundary layer. The boundary layer is thin underneath the forward part of the vessel, and increases in thickness as it moves towards aft. If the sides of the hull are steep, some of the air bubbles in the boundary layer may escape to the sea surface along the vessel sides. It is our experience that a wide and flat bottom, with a rising angle less than around 13 degrees, is prone to giving air problems for the transducer. In any case a transducer location in the forward part of the hull is preferred in order to minimise the influence of the boundary layer.

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Installation manual

Propeller noise

The propulsion propeller is the dominant noise source on most fishing vessels, research vessels, merchant vessels and pleasure crafts. The noise is transmitted through the sea water. For this reason, the transducer should be placed far away from the propeller, which means on the fore part of the hull. Positions outside the direct line of sight from the propeller are favourable. On small vessels with short distances it is advised to mount the transducer on that side of the keel where the propeller blades move upwards, because the propeller cavitation is strongest on the other side. The cavitation starts most easily when the water flows in the same direction as the propeller blade, and that is to some degree the case at that side of the keel where the propeller blades move downwards.

Bow thruster propellers are extremely noisy. When in operation, the noise and cavitation bubbles make the echo sounder useless, almost no matter where the transducer is installed. And when not in operation, the tunnel creates turbulence, and if the vessel is pitching, the tunnel may be filled with air or aerated water in the upper position and release this in the lower position. Therefore, an echo sounder transducer should be placed well away from the bow thruster.

851-165216 / Rev.A

Simrad 50/200 Combi D Transducer

Summary and general recommendation

Some of the above guide lines are conflicting, and each case has to be treated individually in order to find the best compromise. Generally the propeller noise is the dominant factor, and a recommended transducer location is in the fore part of the hull, with maximum distance from the bow equal to one third of the total length of the hull at the water line.

General recommendation for transducer location: (A) = Transducer (B) = Angle 1 - 2 degrees (L) = Hull length at water line (M) = Maximum 1/3 of the hull length at water line (L)

If the vessel hull has a bulbous bow, this may well be a good transducer location, but also here must be taken into consideration the flow pattern of the aerated water. Often the foremost part of the bulb is preferable.

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