This paper not to be cjted wjthout prior reeerence
oe
the aUlhor.
I TERNATIONAL COUNCIL FOR
THE EXPLORATION OF THE SEA
C.M. 1988/B:15
Fish Capture Committee
WHY FEW DUTCH BEAM TRAWLERS USE
A CO TROLLABLE PITCH PROPELLER
by
W.C. BIom
Netherlands Institute for Fishery Investigations
P.O. Box 68, 1970 AB IJmuiden
The Netherlands
•
,,
L
- - - - - ---
This paper not to be cited without prior reference
10
the author
-
-
-- --- --- ---------------.;"1
•
INTERNATIONAL COUNCIL FOR
THE EXPLORATION OF THE SEA
•
C.M. 1988/B:15
Fish Capture Committee
WHY FEW nUTCH TRAWLERS USE A
CONTROLLABLE PITCH PROPELLER
by
Ing. W.C. BIom
NetherLands Institute for Fishery Inverstigations
P.O. Box 68, 1970 AB Umuiden
The NetherLands
•
'.
.
.
"
INTRODUCTION
Before dlscussing the direct facts, first some ba.ckgrounds: .
.
For those who aren't familiar with the Dutch beamer see figure 1 (vessel) arid figure 2
(fishing method).
,
..
.
About 70 % of the Dutch see-going fleet (500 vessels, shellfish excluded) uses the
beamtrawls for flatfish several months a year and about 40 % even uses nothing else but
the beamtrawl. So you rriay say there is a lot of experience especially since the mid
sixties, when the beamtrawl came extensivelyup for flatfish-fishing. Before these years
the Dutch fishermen only knew the beamtrawl for shrimp fishing in the estüaries and
along the coast.
•
The flatfish beamtrnwl speed is 4 mHes for the smaIler vessels, up to 7 inÜes for the
vessels of 1800 k\V (2500 hp) and more. To get the flatfish, especially the commercial
attractive sole, you need a speed of over four miles with ä big pull:. the greater the speed
(with heavy beamtrawls)the higher the percentage in sole catch. So what the skippers
always require is: an optimal pull-propeller at a weekly fishing/steaming partition of 80/20
percent. Generally speaking for the Dutch beamtrawl fisheries only two types of
propellers are interesting, namely: , .
- a ducted fixed pitch propeller (F.P.P.) (figure 3), or
- a ducted controllable pitch propeller(C.P.P.) (figure 4). .
.,
Because propellers without a duct (or so-called nozzle) have on forehand a lower pull (ca.
15 %) at the fishing speed than the ducted propellers (figure 5). That means less catch
capacity imd besides a vulnerable constritction with regard 10 the gear handling. . '
Conceming ducted or open propellers for fishing cmft an interesting article haS recently
been published in Fishing News International, here given as enclosure 1.
A comparison of twotypes shows:
. ,.
".'
,
,.'
'.
,
Firstly the fIXed bladed propeller with the controllable pitch propeller, both designCd for
max. pull for fishing at 4 knots.
•
As you can see in figure 6, for the C.P.P. the fuH main engine performance can bC used
also at free-running speed, where at F.P.P. only can take about 85 % of the engine
power...
'.
'
Especially for those beamers with distance offshore fishing grounds this is an advantage
resulting in a higher steariUng speed of about 0,5 mots. However, the c.P.P. efficiency
at fishing speed is about 3 - 4 % less owing to the big boss for the controll-gear (figure 4)
and to the greater clearance betweeri the nozzle and propeller bhides necessary for turning
of the blades.
At steaming the C.P.P. has an extra power of 15 to 20 %'.,
,
With the. brief coinpanson above, the vital pulling force (dis)advantilges have been giveri.
Before conclusions can be drawn, two design aspects must be considered yet, namely:
- the propulsion plant layout (power takes off or not),
- the cost-effects.
Layout CPPIFPP installation:
, , . ' '.. '
.
.
" ..., .
When using power takes off (PTO) for boardnet generators the CPP-installation offers a
gr6at advimtage, because of constant revolutions of the propeller shaft, nevertheless the
load condition of the propulsion diesel engine. To this I like to refer to an interestirig
study (and trials) of our English SFIA colleagues: Power autit tnalsof Scottish seiner
"Acom" (figures 7::8), wherefrom an economical poirit ofview offuel usage it is hetter
to reduce the RPM at maximum pitcht
~..
.'
00. the other hand owing to the mOdem riücro-electronics, it is no technical and layout
problemanymore to use PTO's on a propeller shaft,with varying revolutions, the S.C.R.
(silicon controlled rectifier) system. This has already been instalied on some beamers
(very experisive), although the majority of theDutch beamer skippers prefer separate
boardriet generators l.Ü1d no PTO's (See RNO repoit TO 84-03 (in Dutch».
-2-
So the CPP advantage ofcoristaßt TeV'S isn't hefe decisi~e; up to now the only reasons
for application of this propeller are distint fishing grounds and ofcoui'sc the cost-effects
«30 % of the week steaming).
.'
. . . . . .'. ..' . ' ,
.
Cost-effects:
,
As you can see in figure 3 and figure 4. the CPP-installation is more complicated thari a
sturdy ducted ~PP propeller.
.'.
'
"
The extra components of a CPP-installation are amongst others:
- blades tuming in the boss, mostly controlled by a rod thfough thc hollow propeller
shaft; electronically steered servo purrip for serving ofthe rod; altogether about f
200.000,=($ 100.000) morethan a fixed propellerof 1500 kW (2040 hp) 3000 mm S1.
This means an extra investment of two percent of the new-building price (about f 5
million).
l
a
•
of
Besides special problem connected with .the appllcation of a CPP in a nozzle consists
dismorinting and dismantling of a damagoo propeller blade resulting in extra costs for
.
repair and extra delay in fishing tiine.
Altogether a costly and to the opinion of the Driteh skippers a vulnerable propulsion phint
with no clear improvement or even reduction of fishing efforts in beam trawling.
Nevertheless there
some beainers With CPP's.
are
Cpp outboard beamers: ,
.
Up to now we considered the Dutch beamers as fishing vessels on the same fishing
grounds. But the North Sea bottom shows differences. namely in the nofthem part we
have flat sandy arid/or muddy bottOIn sttuctures. while in the southem part (Channel area)
there are many sand ridges (or uriderwater duries). Here the use of a good adjustable pull
is profitable. one of the not yet mentioned CPP-advantages!
Besides the CPP beamers (2) which have been involved iii the heavy fleet trials/tests
(1980 - 1984) appeared 10 be very suitbale far this type ofinstallation.
Conclusion:
,
.,
In spite of the bCnefits of controllable piteh propellers; only 4 beamers of the 120
new build bearriers the last 6 years have a controllable pitch proPeller and weIl
'
only those for the Southem North Sea.
Costs are unfavourable in relation to the benefiiS. while the vulnerability arid repair
' . .. .
'
costs result in loss of fishing time.
fishing efforts on nem:- fishing grourids with a low flatfish population over wide
spread areas.
"
However. owing to the overcapacity problems in the Dutch beamtrawl fisheries
things are changing in beamer design arid distant water voyages. Maybe then the
CPP will become in favour.
m
•
Enc1oslires:
- Article of mr. WilliamS
- Conclusions of SFIA-report
Literature list:,
. ..
'''.,
' .' .
W.C. BIom - Auxiliaries on 1300 kW beamers (Duteh. 1984).
W.C. BIom - Measurerrients on power at the UK 173 (Dutch. 1986).
. .
'
S.F.I.A. Repon "Power autit trials on Scottish seiner "Acom".
G. de Wit - Study grading technical highschool over CPP at b6ainers (Dutch. 1987).
-3-
l
LO,A.
FIGt. 1
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oe
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-6
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LKrvOT-5 J --~e>~
14
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I
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MAX. ~PEED fPP
.
I
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4
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-8
"":>PEED [k:NOTS)
12
10
5i>"
14
FIG.6 A
-- -
CC>.)
FPP OpeV>
Cpp Open
(c)
R\='M
240
r
P~O~200
REV.
PER
MIt-.!.
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180
•
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./'1
600
I ~A-
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'<
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RESlS"lArJc..E!
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2
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PP?
12
14
Ir------- -FIG.6 ß
I
,
- - - FPP Ducteol (b'J
cpp Open
(e)
I
_- (CPp)
t
240 .-!,r.3l- - -
RPM
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R·I PM.
-
.
II 200
650
!
600
•
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l'
10
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i
I
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400
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350
RESt5TANLE/
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5
FORCE
HAi.-:>PEED
c.CP
MAX~?
F pp Dluc.tecf
2
4
~PEED
6'
8
(KNOTS")
10
12
tiä
14
-
r
FIG.a
FIG. t
60
60"
TOWING
FREE RUNNING
0::
::> 50
50
0
J:
er;
w
DIFFERENCE
0-
tfl
1.0
w
~.
1.0
«-,~~Cy..
~~~~ <?'
0::
t-
DIFFERENCE
~~~
:J
3= 30
30
9l.L.
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-1
w 20
::>
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1
2
3
5
KNOTS
~
6
7
8
9
10
0
1
2
KNOTS
RESULTS CONDENSED FROM ACTUAL SEA TRIALS
M.F.V. CONSTELLATION
3
4
\:.uu
THE wrlt~r graduat.ci
from Chalmers Univer·
.ltv .of Technology In
Gothenburg In 1959. He
joined SSPA In 1951.
For most of his time In
the companv he ha.
worked
with
large
Swedish and foreign
yards
and, .hipping
companies. Then. at the
end of 1984. he .tarted
his present work with
SSPA Skeppskonsult. a
special saction which
serves domestic ahipping. and fishing and
small
yards
within
Scandinavla.
SSPA Maritime Conaulting AB was formerlv
the Swedish State Shipbuilding
Experiment
Tank. Some yeara ago It
bacama a limited company with the Swedlah
j/ovarnment a. ~ share.
..uu
350
.
'000
2. eonv:~ ~
- prop.U..
;"
"~--.
.
~
500
300
. "er
. . . ,1.
250
,
200
~,~~'"
"
,
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I
or
lI't .. st
A..
;.
Fishing Ne~ Internat'ional
....
."
"....... ..
.....
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-
January 1988
v.lu •
./
'"'' 1'·
~.,
.~
~
/K
0
[ENCL. 1.1
Pud! Uon r o.
5SPA lshl nll
vel'. . . . 10
100
9.5
'0.5
'1
11
'0
1.. ,,11 n9
'SJ/50
5t .... i nll
only
Knots
"nly
F.g 3: SSPA 20 m ',sh,ng vessel. V•• ,ly .n.rgy eonsumpuon In MWh .t 2000 hou...t
••• a v.ar. Fig 4: A 2:t m trawl.r with conv.ntional prop.n.r. At trials. fraa runnlng.
FuUengin. power in kW.
..
.Propellers lör lislJilJg eralt
•
Ducte,d (Ir not?
DURING the PaSt two years, exteDsive systematic model
holder: Its
services
Include ahipping. naval.
offshora and general
hydrodynamics. It haa a
number of laboratorle••
Including a towlng tank.
weve baaln and cavltation tunnal.
600
.
500
tests for flShingvessels have been carried out by SSPA
Maritime Consulting Aß (formerly. the, Swedish State
Shipbuilding Experiment. Tank) in Gothenburg. The aim
of the tests is ·to gain knowledge about the importance of
huß forms and propeUers to the trawUng and free running
characteristics of flShing vessels.
Some of the tests hllVe t>een perfonned 'in order to compare
conven~onal with dueted propellers. The comparision has included
the free running! trawling and the beilud pull conditions.
! Lasl lune two similar trawleR were
I,
1.1 '" conv
pro olhr
300
,'' '
thc first with conventlonal propeller and thc
scc()ßd fiucd with ductcd propeller. Wilh
financial support from the Swcdish Board
of rlShery and thc Swcdish· Transport
Research Board. extensive and accurate
tests have bccn perfonned with Ihe two
vcsscls covering speed. power and bollard
.
.'
pul!.
Tbc rcsults from the syslcmatical model
tests havc bccn fully confinncd by full-seale
tests wilh the two trawlers. Tbc use of a
dueted propeller means. a considerably
higher pull force trawling at Iow speed
while the vcssel wilh an open propeller
aUains a somcwhat higher. speed frccrunning at constant enginc power.
jV
1.9 '"' duct d
pro .U.r
taO
; dclivercd from Swedish fishing boat yards.
W
~~K
200
~ :JY
100
I
2 conv
pr p.Uer
Improved
0
.
Knot.
9
'0
Fig 1: SSPA 20 m.tr. tl.hlng v.... I.
Propallar powar In kW at .t.amlng. Fig Z:
SSPA 20 m flehlng v....l. Propall.r
powar In kW wha.!!-!tawling at 4,5 knou,
600
, .1
conv
prop 10r
500
"
1
400 t---t--...,..rl'T-i"----l
300
t---I---l~_-+--_I
200
1---+-4WY--4---l'--~
100
t--~'----t----l'--~
O'--_-L_ _-'-_--''-_~
o
25
50
75
100
Puil r~rca •. kll
As wilh merehant ships. IIshing veucls
have rcccntly bccn equippcd wilh larger and
slower running propellers. In this way their
propeller emdency has bccn improvcd and
thercforc fuel costs havc bccn reduccd:
However. as vcry few modcl tests are car·
ricd. out for IIshing vessels. the propellers
are usually dcsigncd wilhoul the aid of
model test rcsults by which comparison of
alternative propellers can be carried oul
rcgarding demand of engine power. pull
force at trawling. free running speed. elC.
Whcn high pull force at trawling is specially dcsirable. the solution will onen be a
dueted propeller instead of a large slow.
running propeller (which may inerease the
clraught of the' vcsscl beyond aettptable
figurcs). Dut evcn the choice of a ducled
propellcr sccms to be made without know.
ing the e/feet. for instancc. on fucl cconomy
at steaming. In gencral. the fIShing vcsscls
are built ~one and one" and. therefore. no
yard or privatc owner can arrord to carry
out comparativc teslS for oblaining evidence
of Ibe profit or Ioss wilh a ducled propeller.
Two convcntlonal and one dueted
propeller models have bccn tcsled on a hull
fonn from SSPA's IIshing vcssel serics._.
Tbc Iarger onc of the two·convenlional
propellcrs can bedesignatcd Mbrge and
s1ow-running··. 1I is bccoming more and
more usual to choose such a propeller for
bigher propeller elrlCiency. From Fig, I it
-================-I'
<_'r' .•'
PROPULSION & POWI
fro
9 • cluet.d
prope!hr
'50
,'-
I i\
1.7 • conv
prop.U.~/
10
~
By AKE WILLIAMS.
SSPA Maritime
~~nsulting ~B. Gothenburg'
can bC secn thäl this propeller demands th~
lowest engine power. 1I will also be noled
that, at nearly all ship speeds. the requircd
enginc power of the duetcd propeller is evcn
higher Ihan. for the ~smaII and fast.
running" propeller. But, tbc order of merit
for the dirrerent propellcn is valid only for
the frcc-running condilion of the sbip.
Ducted better
AI trawling at Iow ~peeds. the ducted
propeller is dellnilely better than the two
conventional propelleR (sec Fig. 2). Results
of the model tests indicate thaI the pull
force is incrcascd by about U per cent by
Ibc dueted propeller at an cnginc outpul of
SOG kW.
Also. bollard pull tests have bcCn carried
oul and they indicate a gain of nearly 30
per cent by usc of the duetcd propeller. Tbis
may be of small practical value for allshing
vcsscl but il is useful whcn n:calculating the
rcsulls from a bollard pull test to be valid
for trawling al. say 4 knolS.
.. ,
Starting from infonnation about running
lime at steaming and trawling, the ycarly
energ)' consumplion of flSbing vesscls wöth
dirrerent propelleR can now be shown (fig.
3)..
'.
Tbc rcsullS of the syst=atic model leSIS
are the basis of tbc curvcs of thc diagram
going from 100 per cent steaming to 100 per,
..
cenl trawling (on a timc basis). ' .
Fisbing vcsscls with mOSI of thcir time al
sea devoled to trawling will gct mosl advan.
uge of a ductcd propeller. Dul vcsscls with
long dislanccs to travcl to grounds and
which spend long periods scarcbing for IIsh.
will gain more from a \ar&C s1ow-running
propeller th,an from a duetcd propeller.
Consumption
Tbc ycarly e~~rgy eO;"~Ptio~ shoWQ in
Fig. 1 is bascd on 2000 houn a ycar al $Ca
and is cxprcsscd in the appropriate unit
MWh (mcgawat boun). Far those who
prcfer amount of foel as mcasure of cncrgy
consumption, 1000 MWh is approximalcly
cqual to 300 cubic metres of dicsd oil.
In order to hav<: tbc rcsults from the
systcmatic model lests conflrmcd. full-seale
tcsts were urricd out wilh two new lishing
vesscls.
,
Tbese vcsscls wcrc dcli\'Ucd and teslcd in
June 1987. Tbcir \englh is in the range
2o-2S melres, which is somcwhal \arger than
Ihc vcsscl in Ih~ model test scrics. Howcvcr.
EjJC L.
2.. 1
Sea Fish Industry Au~~ority
Industria1 Deve10pment unlt
Technica1 Report No. 249
August 1984
PO*:R AUDIT TRIALS 00 SCOT.rI.SH SEINER 1\lXRl
Scottish seining now accounts for 13% of the fishing vessels in
the Scottish fishing fleet.
OJer the last 18 years, since the SFIA last
investigated the performance of this dass of vessel, power- levels have
increased and there is now a wider use of hydrau1ic deck and auxiliary
•
machinery.
The report gives resu1ts of an instrumented trial carried out on
the modern Scottish 24m seiner ACORN of 575hp.
'Ihe trials were aimed at
quantifying
the different areas of
the proportions of power
used
in
coris!-ID1Ption (propulsion, winches, e1ectrical circuits, etc.) at all periods
of the operating cyc1e of the vesse1, both as an aid to identification of
possibi1ities in power consumption savings and also to identify the levels
of waste heat which might be usefu11y recovered.
Recommendations are made
for potential savings on this and similar vesse1s and comparisons are mace
with the OPPORrUNE Ir trial of 16 years ago.
In the event the trials showed the ACORN to be of extremely
efficient design in most of its specification and the consumption achieved
provides "yardstick" values against
whic~
other skippers might wish to
compare their own operations, or builders to coropare the specification for
a new vessel.
w.
Sid::Ue,
Principal Mechanical Engineer
~
l
,
i
!'.'
,I
I_..
9.
CCNCIlJSIONS
9.1
General
...
i.
r
i
The ACORN is a good example of a fuel efficient fishing vessel and
...:-
the results obtained on these trials can be used as a "yardstick" by which
i
other vessels may compare their performance.
~
~
I
.•
..
"""
~
There are three main reasons for this efficiency:
J
I,
i.
ii.
7r.
"-
~
11
t
~
J
l-
•
iii.
a fuel conscious skiwer.
of catching fish in terms of
Prosecuting a fuel-efficient method
i. e. Sa:>ttish seining (or
fuel per kg of fish captured,
Vessel management
py
flydragging) .
'Ibe main engine
is direct drive,
slow speed and has a level
specific fuel consumption throughout the operating range.
The prop..1lsion package thus takes advantage of the established
principle that for maximum propulsive efficiency systems, the propeller
should be as large a diameter as possible and cor.respondingly run as slow
as possible.
'-.,
f
Ii
J
There are two areas where significant fuel savings might be made
on ACORN.
'Ihese concern generating sets whereby better matching of rating
to demand could have been made and where installation of a heat recovery
system for
accorrmodation and domestic water heating could have reduced
overall dernend.
fe
...
..
'1
45