515
1 INTRODUCTION
The ferry “Polonia” shown on Fig. 1 is one of the
biggestshipsenteringtheYstadharbour.
It should be noted that “Ystadmax” ship is
determinedas150meterslengthwhenM/F“Polonia”
hastheOALengthof169,9meters.Theverylimited
spaceofharbourbasin,the
largewindageareaofover
3506 square meters, and for the most part bad
weather conditions in Ystad, makes the manoeuvres
extremelydifficult.
Figure1.M/F“Polonia”[ferry‐site.dk]
Four modern engines, through two transmission
gears, are driving two inside turning propellers,
makingpowerof7920KWpereachoneshaft.Three
thrustersarelocatedinbow,oneisplacedinaftpart
oftheferry.Tworudderswithbrakingbla des(rudder
back) can be used separately
or coupled, giving the
rudderangleof45Deg.
Themainshipparticularsarelistedbelow:
GrossCapacity 32000RT
Displacement 6950T
LengthOverall 169,9m
Breadth 28,0m
High 42,3m
Draught 6,1m
Propulsion: Twin controllable pitch propeller
propulsionplant.
Main engines: 4 x STORK‐WARTSILA
,3.960 kW
eachat600rpm,total15.840kW.
Manoeuvring machinery: Rudders‐2x
BARKEMEYERflaptype.Synchronousorindividual
Analysis and Evaluation of Manoeuvrability
Characteristics of Polish Ferries m/f „Polonia” and
m/f „Gryf”
M.Szymoński
NavalAcademyofGdynia,Poland
ABSTRACT:ThepaperdescribessomespecificmannerofM/F“Polonia” manoeuvringattheYstadharbour
wheresheisregardedtobe“overmaximalship”andalsoM/F“Gryf”manoeuvringatTrelleborg,takingpart
intoconsiderationtheeffectofwindpressureintotheship’ssuperstructuresandhouses.
http://www.transnav.eu
the International Journal
on Marine Navigation
and Safety of Sea Transportation
Volume 7
Number 4
December 2013
DOI:10.12716/1001.07.04.06
516
operation.Ruddersurfacearea14,49m2perrudder.
Ruddermax.angle2x44degrees;forspeedabove17
knotsrudderanglelimitedto35degrees.
Sidethrusters(BRUNVOLL typeSPA/VP,
electrically driven): 3 bow thrusters 1600 kW each;1
sternthruster1600kW.
The both pla ns of Ystad Harbour and Trelleborg
are
presentedinFig.2.Theberthingplaceoftheferry
“Polonia“islocatedatthe170moflengthquayJӓ
rnvӓ gsfӓ rja. All dimensions of the inner harbor
basin are comparable with the ferry size which is
beyondthe“Ystadmax”.
Due to the wide windage area of the
vessel, the
critical for the ferry are the entry manoeuvres,
specifically during the winds beyond 19 meters per
second ( 8° B ), as it was described in subsequent
chapters.
Figure2a.Ystadharbour
Figure2b.Trelleborgharbour.
Theferry“Gryf”isshowninFig.3.Sheisentering
the Trelleborgharbourin widespectrumof weather
conditions,whenthebasinareasareverylimited,too.
Thespaceof170metersonly,availableforrotating
theshipofLOA=158mandthewindageareaof2600
square meters into
the harbour, makes serious
difficultiesinthe portmanoeuvres.Dueto the wide
windageareaofthevessel,thecriticalfortheferryare
the entry manoeuvers, specifically during the winds
beyond 14 meters per second ( 6° B), as it was
describedinsubsequentchapters.
ThemainM/F“Gryf”
particularsarelistedbelow:
GrossCapacity 18653RT
Displacement 13692T
LengthOverall 158,0m
Breadth 24,0m
High 45,0m
Draught 5,90m
Twin controllable Propulsion :ULSTEIN pitch
propellerpropulsionplant.
Main engines: 2x WARTSILA‐SULZER 6ZA40S,
3960kWeachat510rpm.
Manoeuvring machinery: Rudders‐2x
OFF
BECKER withflaps.Synchronousoperation. Rudder
max.angle2x45degrees.
Sidethrusters(BRUNVOLL,electricallydriven):2
bowthrusters1x760kW+1x800kW.
Figure3.M/F„Gryf”.[JakubBogucki2005r.]
2 MANOEUVRINGSUNDERTHEWIND
PRESSURE
Whenthewindblowsagainstthesideoftheship,the
bowtendstoturnslowlydownthewind.Bothferries
“Polonia” and “Gryf” have less lateral resistance
under water in bow than in stern such they when
blown sideways, the bow and stern respond
differently. The bow and stern thrusters are
designated for pushing the ship against the wind
pressure.
We can compare the moments due to wind
pressure both ferries “Polonia” and “Gryf”. Suitable
dataarepresentedinTables1and2.Theabovesaid
moments can be useful for calculation of heeling
leversduetowindpressure,butforanalysethewind
influenceformanoeuvrescharacteristics,too.
Thebasic modelforcalculationsthewindpressure
isshowninFig.4.
517
Figure4.Thebasicmodelforcalculationofwindpressure.
[M.Szymoński]
Table1.MomentduetowindpressureofM/F“Polonia”
_______________________________________________
Draught:5,00m
_______________________________________________
Item AreaWindpr. W.force VCG* V.moment
m² N/m² Tonnes m Tonn.M
_______________________________________________
Windage
area 3700,40 120,00 45,27 14,44 653,84
_______________________________________________
Displacementatdraught5,00m 13667,00
_______________________________________________
Draught:6,20m
_______________________________________________
Item AreaWindpr. W.force VCG* V.moment
m² N/m² Tonnes m Tonn.M
_______________________________________________
Windage
area 3505,90 120,00 42.89 14,47 620,73
_______________________________________________
Displacementatdraught6,20m 18107,00
_______________________________________________
[M.Szymoński]
Table2.MomentduetowindpressureofM/F“GRYF”
_______________________________________________
Draught:5,00m
_______________________________________________
Item AreaWindpr. W.force VCG* V.moment
m² N/m² Tonnes m Tonn.M
_______________________________________________
Windage
area 2449.5 120,00 29.96  12,00 359.56
_______________________________________________
Displacementatdraught5,00m 10910,00
_______________________________________________
Draught:5,90m
_______________________________________________
Item AreaWindpr. W.force VCG* V.moment
m² N/m² Tonnes m Tonn.M
_______________________________________________
Windage
area 2323.5 120,00 28,42  12.45 353.85
_______________________________________________
Displacementatdraught5,90m 13692,00
_______________________________________________
[M.Szymoński]
The above results are made for ships in ballast
conditions (maximum windage area for T= 5.00 m)
andfully loaded(T= 6.20m andT=5.90‐“Polonia”
and“Gryf”,respectively).
To compare the analysed manoeuvring
characteristics of both ferries the following data,
showninTable3,shouldbetakeninto
consideration.
For maximum draught of ferry “Polonia”, equal
6.20m,thewindpressureof120N/m²(6ºB)which
createstheforceof42,89Tonnesisbeingdefeatedby
near twice greater side thrusters force of 84,84
Tonnes.
Atthesame time, for maximumdraughtof ferry
“Gryf”,equal5.90
m,thewindpressureof120N/m²
is only balanced out by side thrusters with towing
forceof27,57Tonnes.
Table3.Thecomparisionofdata.
_______________________________________________
FerryWindforceforThrusterstowing
pressure120N/m² force
[tonnes][tonnes]
_______________________________________________
POLONIA
T=6.20m 42,8984,84
GRYF
T=5.90m 28.4227,57
_______________________________________________
[M.Szymoński]
3 CONCLUSIONS
Presented results and analyse of wind moments for
both of ferries are made for static wind influence
blowingatrightangleagainstthewindageareaofthe
ship.
The relationship between wind force‐in meters
persecondandwindpressureonthewindagearea–
inN/m²,areshown
inFig.5.
Figure5.Therelationshipbetweenthewindforceandwind
pressure.[M.Szymoński]
Fig. 6 and Fig. 7 are showing the relationship
between the wind pressure on the windage area of
ferries: “Polonia” and “Gryf”, respectively‐and the
windforcepushingtheship. Thesefigurescanalsobe
used for determination of safe range of static wind
effect against the side thrusters. For M/F
“Polonia”
thesaferangeofthewindeffectisdeterminedas19
m/sor8°B.Intheabovesaidrangeofthewindthe
safemanoeuvringoperationscanbeexpected.
Figure6. The relationship between wind presure and
wind/thrusters towing force for M/F “Polonia”.
[M.Szymoński]
518
Figure7. The relationship between wind presure and
wind/thrusters towing force for M/F “Gryf”. [M.
Szymoński]
ForM/F“Gryf”thesaferangeofthewindeffectis
determinedas14m/sor6°B.Intheabovesaidrange
ofthewind thesafe manoeuvringoperationscan be
expected.
Inrealconditionsofportmanoeuvringsnotstatic
but dynamic wind effect has to be considered. It
means
that in case of dynamic effect, the temporary
wind force can be much stronger than its static
equivalent.Itshouldbeaddedthatinrealconditions
the angle of wind pressure differs from the right
angle,whichcausesthatthedynamicwindforcecan
bealsomuchstrongerthan
itsstaticequivalent.
During the port manoeuvrings not only bow
thrusters are being used, but also the main engines,
rudder blades and stern thrusters, if available. It is
important that not only analysed bow thrusters, but
alsotheabovesaidmanoeuvringmachineryarebeing
usedtodrivetheferryagainstwind
pressure.
Havingtheexperienceinexploitationoftheabove
ferries in dynamic conditions and recapitulate the
presented analyse, it should be concluded that the
safeportmanoeuvringscanbedonewhenthewindis
blowing with temporary force around 40% stronger
than it was calculated for static coditions. It means
thattherightvaluesareasfollows: 19m/sincaseof
M/F“Gryf”and27m/sincaseofM/F“Polonia”.
BIBLIOGRAPHY
Unpublished documents and technical reports regarding
theanalysedferries.