Simrad 38-9 - INSTALLATION REV A, 38-9 Installation Manual

Installation manual

Simrad 38-9

38 kHz Single beam transducer

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

www.SIMRAD.com

Simrad 38-9

Installation manual

This document provides a general description of how
to install the Simrad 38-9 Single beam transducer. The
information must be regarded as general guidelines and
recommendations only. The installation shipyard must
design and manufacture installation hardware to fit the 38-9
transducer on each individual vessel.

305265/A

August 2006

Document history

Document number: 305265 / ISBN-10: 82-8066-074-7 / ISBN-13: 978-82-8066-074-9
Rev.A August 2006

Original issue.

Copyright

©2006SimradHortenAS

Disclaimer

The information contained in this document remains the sole property of Simrad Horten AS. No part of th is
document may be copied or reproducedin any form or by any means, and the information contained within
it is not to be com municated to a third party, without the prior written consent of Simrad Horte

nAS.
Simrad Horten AS endeavours to ensure that all information in this d ocument is correct and fairly stated,
but does not accept liability for any errors or omissions.

Warning

The equipment to which this manual applies must only be u sed for the purpose for which it was
designed. Improper use or maintenance may cause damage to the equipment and/or injury to personnel.
The user must be familiar with the contents of the appropriate manu als b e fore a

ttempting to operate
or work on the equipment.
Simrad disclaims any responsibility for dam ag e or injury caused by improper installation, use or
maintenance of the equipment.

Support

If you requ ire maintenance on your Simrad equipment, contact your local dealer. You can also contact
Simrad using the following e-mail address:
e-mail: [e-mail]

Strandpromenaden 50
P. O. Bo x 1 11
N-3191 Horten,
Norway

Simrad Horten AS

Telephone:[phone]
Telefax:[phone]

[e-mail]

www.simrad.com

Installation manual

Table of contents

INTRODUCTION ................................................................ 5

TRANSDUCER L OCATION . ..... ............................................ 6

Go deep.....................................................................................................................6

Vessel heave .............................................................................................................6

Noise from protruding objects on the hull................................................................6

Boundary water layer ...............................................................................................7

Propeller noise..........................................................................................................7

Inclination of the transducer face .............................................................................8

Summary and general recommendation...................................................................8

WAYS OF MOUNTIN G THE TRANSDUCER ......................... 10

Transducer blister ...................................................................................................11

Box keel..................................................................................................................17

Flush mounting in a steel tank................................................................................19

Acoustic window....................................................................................................21

Inside the hull .........................................................................................................23

Drop keel ................................................................................................................25

Retractable transducer ............................................................................................26

CABLE G LANDS ............................................................... 27

Order numbers........................................................................................................ 27

Cable gland for steel hulls......................................................................................28

Cable gland for wood or GRP hulls .......................................................................29

Cable glands for small hulls ...................................................................................30

Cable splicing.........................................................................................................31

STEEL CONDUIT.............................................................. 32

HANDLING AND MAINT ENANCE ...................................... 33

Approved anti-fouling paints..................................................................................34

DRAWING FILE ............................................................... 35

Single frequency, single beam, low power transducer connection.........................36

Outline dimensions.................................................................................................37

Mounting arrangement ...........................................................................................38

Mounting ring.........................................................................................................40

Blister assembly .....................................................................................................42

Blister design..........................................................................................................44

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Simrad 38-9

4

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Introduction

INTRODUCTION

The purpose of this manual is the provide the basic information
required to install the 38-9 Single beam 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 number: KSV- 203635.
A cable gland kit for steel hull is included with the delivery.

Other cable glands must be ordered separately.

Transducer installation

The next chapter in this manual provides general guidelines
for transducer installation. The drawings specific for the 38-9
transducer are located in the Drawing file.

Technical specifications

Refer to the 38-9 Product specification.

Additional parts

The following items can be supplied by Simrad to facilitate
installation:

• Mounting rin g: Order number 499–203336

• Transducercable (for extension): Order number 642–016604

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Simrad 38-9

TRANSDUCER LOCATION

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 w ater 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.

WARNING
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.

Noise 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 flow 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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Transducer location

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.

(CD17004P)

BAC

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.

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

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Simrad 38-9

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.

Inclination of the transducer face

Ideally, the transducer face should be mounted in parallel with the
sea surface when the vessel is in normal trim, as this will provide
the most accurate echo information. However, it is also very
important that the w

ater flow over the transducer face is laminar.

In order to ensure laminar flow, the transducer face may be tilted
slightly upwards in relation to the water flow. This allows the
flowing water to meet the face directly, and assures laminar flow.
The inclination angle must however be determined carefully. The
angle must be small on transducers with narrow beam angles. As
a rule of thumb, mount transducers with beam angles smaller
than seven degrees with minimum inclination angle. The smaller
beam angle your transducer has, the smaller the inclination angle
can be.

Ensure that you do not mount the transducer with a negative
inclination angle. This may cause turbulence under the transducer
face, and reduced echo sounder performance.

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.

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Transducer location

(CD017004Q)

BA

L

M

General recommendation for transducer location:
(A) = Transducer
(B) = Inclination angle
(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.

(CD17004C)

A

B

Recommended location of the transducer on a bulbous hull:
(A) = Thruster
(B) = Transducer location

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Simrad 38-9

WAYS OF MOUNTING THE TRANSDUCER

There are many different ways to mount the transducer. These
are the recommended methods to mount a circular transducer.

Topics

Transducer blister on page 11
Box keel on page 17
Flush mounting in a steel tank on page 19
Acoustic window on page 21
Inside the hull on page 23
Drop keel on page 25
Retractable transducer on page 26

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Ways of mounting the transducer

Transducer blister

With a transducer with circular housing, one recommended
installation method is by using a blister. The transducer blister
must be designed and manufactured by the installation shipyard
to fit the vessel’s size and hull shape.

Mounting and clamping rings

Circular transducers may be provided with mounting and
clamping rings, or with drawings to allow f or local production
of these. The mounting r ing is welded to the hole in the
transducer blister, while the clamping ring fits around the edge
of the transducer body. Bolts through the clamping ring into the
mounting ring will then secure the transducer between them.
Note that several transducers use direction guides to allow correct
mounting.

Smooth surface

Mounting screws or bolts must not be extruding from the
transducer blister. Ensure that the surface of the transducer face,
the blister, the hull plating and putty around the transducer is as
even and smooth as possible. Obstructions on these surfaces will
create problems with turbulant flow.

Horizontal support bar

Large diameter transducers must be fitted with a horizontal
support bar. T his bar can be secured to the mounting ring using
threaded rods.

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Simrad 38-9

Example: Large transducer

The illustration below shows a typical transducer blister designed
for a large transducer. Note that due to the physical size of
the transducer, a U-shaped support bar (E) is used to support
the transducer. The purpose of this support is to prevent the
transducer from being pushed up into the blister in heavy seas.

(CD017010A)

H

E

E

K

G

B

D

A

C

F

J

I

(A) = Streamlined blister
(B) = Stiffening rib
(C) = Drainage holes
(D) = Inclination angle
(E) = U-shaped support bar
(F) = Forward

(G) = Cable service loop
(H) = Stuffing tube
(I) = Minimum 400 mm
(J) = Rounded corners
(K) = Air outlet

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Ways of mounting the transducer

Example: Small transducer

The illustration below shows a typical transducer blister designed
for a small transducer. The same blister design principles as for a
large transducer apply.

E

E

A

C

G

D

F

B

(CD017010B)

(A) = Streamlined blister
(B) = Mounting ring
(C) = Clamping ring
(D) = Guide

(E) = Air outlet
(F) = Forward
(G) = Transducer cable

Note that the transducer cable must be provided with a cable l oop
inside the blister. Observe the vertical forward edge of the blister.
This will guide the water to each side of the blister.

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Simrad 38-9

Example: Medium sized transducer without
clamping ring

The illustration below shows a transducer blister designed for a
medium sized transducers. The same blister design principles
apply. Note that the transducer is mounted without a clamping
ring, which makes it necessary to use a different mounting ring
design.

A

B

C

H

F

E

E

G

D

I

(CD017010E)

(A) = Streamlined blister
(B) = Mounting ring
(C) = Bolt
(D) = Self-locking threads

(E) = Air outlet
(F) = Forward
(G) = Transducer cable
(H) = Transducer

Note that the transducer cable must be provided with a cable l oop
inside the blister. Observe the vertical forward edge of the blister.
This will guide the water to each side of the blister.

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