Manoeuvring large tankers in the approach channels to Europort

'

flHMS VRT

Labomum vo

Mekelweg 2,2623 CD De!ft ToL O15m6a7. Bibliotheek van de

Onderafdeling der Scheepsbouwkunde Technische Hogeschool, Deift

DOCUMENTATIE _(:

/íi'.

₃

DATUM: _{15 PIMRI 1973}

THE JOURNAL OF THE

_INSTITUTE

OF NAVIGATION

VOL. 24 . NO 3 _{JULY 1971.}

Manuvrinp

_o

Laro-e Tankers in the

_b

Approach Channels

_{to Europoort}

L. A. Koelé and C. Don

(Netherlands illirJstyof_{Transport, I Vater Control and Public Works)}

The authors who are officials of the Rijkswaterstat, Department of Harbour Entrances, describe tue ncwly dredged approach channels_{to Europoort at the Hook or io1ind.}

They discuss the handling of large vessels and the rta-igation aids provided for the purpose, emphasizing the value of simulator studies both in the design phase and for

'crew training.

J. INTRODUCTION. in discussing certain aspects of the manoeuvring of large tankers it is necessary to consider the navigational circumstances, and especially the hydrographic and meteorological conditions that ob-tain in the Europoort-area which can be divided into three zones (Fig. i):

the approach route through the English Channel_{and the southern} part of the North Sea to the outer approach channel;

the approach channelsc-the outer channel (bearing Sa° 30') and inner channel (bearing z 12 )to the harbour mouthnear the Hook of Holland;

(iii) from the harbour moles through the temporary mouth to the

Europoort basin, ending in the berthing_{manoeuvres alongside the}

jetty.

The rnanuvring and navigational problems differ greatly for each of these zones. In this paper special attention will be paid _{to the manoeuvring o} very large crude carriers, VLCC's up to 2 ço,000 tons dead weight, in the approach chanpels to the harbour mouth. Since

_{December 969 tankers}

with draughts up to 62 feet have been received_{by the port of} Rotterdam-Europoort.

For problems relating to the design and construction of the channels

reference is made to the proceedings of the

_{Internaticnal Navigation}

Conferences of 196g and 1969.1 It will be suflicient to remark that the siting and dimensions of the approach channels, considering the local h)-drographical circumstances, have been suited as well as possible to the characteristics of these large vessels, by observing

_{thcir behaviour in}

practice and with the aid of theoretical and model studies coordinated by the Departmcnt of Harbour Entrances olthe Dutch Ministry of Transport, \Vater Control and Public \Vorks. A detailed studi' of these investigations, carried out by a team of nautical, hydraulic ad hydrographical specialists, is in preparation and to- he published by the _{Rijks'.vaterstaat in 1970.} The present contribution by two members of this team can necessarily be no more than a general survey.

300

NO; 3 _{MANUVRING IN THE CHANNELS, TO EUROPOORT 301}

H - nc. z. General view of the navigational_area

2. CHARACTERIZATION OF THE NAVIGATIONAL_{AREA. The outer part of}

the approach channel, bearing 82 _{30' with a length of approximately}

30 kilometres and a provisional width of 2200 metres, passes through an area with great differences in bottom configuration. _{Sand waves occur} and the tops of the ridges have been dredged away wherever necessary in order to obtain a safe depth for the loaded tankers. At present the mini-mum permitted keel clearance in this channel _{is 20 per cent of the ship's} draught. Tidal currents occuring_{in this area are probably closely related} to the bottom conflguration and differ from place to place in direction and velocity (Fig. 2). The inner_{part of the channel, with a length of}

1.1.

kilo-metres and a width decreasing gradually from _{600 to 400 metres, has} a relatively flat, dredged bottom. The minimum permitted keel clearance is 15 per cent of the draught. At high-water_{cross currents attain velocities} from I to 2- knots.

Generally speaking manuvring is, among other factors, dependenton meteorological conditions such as visibility and wind force and direction. As it takes about _{3 hours to sail from the channel entrance to the} Euro-poort harbour entrance, tidal and meteorological_{conditions mar change} considerably during the passage, which is a serious matter as VLCC's are

not in principle allowed to stop in the outer channel even under

ex-tremely bad conditions. An emergency anchorage has, however, been

provided (Fig. i). In the second

_{part of the channel special attention}

must be given to the very dense traffic, _{approximately 200 ship} move-ments per day apart from dredgcs &c. (Fig. 2). At present the movement -of deep draught ships is limitedto a one-way traffic.

302

/

(_--FIG.. 2. Currents in the chaxme area during high water. Arrows show velocity of

tidal stream: H. W. Rotterdam, _{20-metre depth contour is shown.} the sessel steady on

_{a straight track, the outer channel with}

_{a varying}

'depth and the inner channel with a fairly flat bottom, both channels

having ari-iblc tidal currents Meteorological conditions affect wind_and visibility andthere isa lot of traffic.

3 RESPONE OF THE SHIi' TO EXTERNAL CODONS In order _{to keep} a ship on a straight track the amount of rudder action required depends on bc-ti conditions Factors w hich could be of Importance are anal) sed in

Fig. _3.

(» Manceuvring in non-restricted shallow

vaters (sittation

i)

without external disturbances

_{(indicáted by the parameter}

o.) In this theoretical case, the ship's track_{will always show} an oscillating character due to the sailing properties of the ship and the w iy in which she _{IS steered 2 The parameters (indicated} in Fig. 3) are:

i. the average values of rudder- and courseangles, respectively 8 and (referred to the centre-line).

2. the root-mean-square values of 6 and ,indicated by

c ()

_{/8 2}

and bycr4)=./2.

It is assumed that the values of 8 and _{& are continuously rccorc:led} over the distance oo.

Here a(6) is a measure of the amount of rudder action hich, with the combined steering ability of the helmsman and the steer-ing qualities of the ship1 is necessary to keep her on the course indicated by o(#).

(19 When there is a field of constant external forces along the track,

caused for instance by wmds

_{or cross currents, the aeragc}

value of the driftangle.at a given speed is determined by the rnagni-tude of these external forces. The fesultant_{of these forces has to} be compensated by a moment caused by the rudder,

so that the

average rudder angle will not be zero (Fig 3 2) To maintain

track in addition to course inolves larger _{rudder moveme'-it. than} 'when maintaining shortterm

_{course only, both to get the ship}

NO 3. MANOEUVRING IN THE CHANNELS TO EUROPOOItT 303

- Wo ezieniol disturbances _i O) theoretical siluotion

+ + + +

\Conitonl itrnal dtsturbnrces (Q a constant)

I. L coused by bind or cross currents

\

A Yawing angle r_{=4 36'45} Rudderang!c=j° S' 38 Yawing angle 5=40 2 Ç'48 Rudder angle ¡ 8 49' 46

.Et

Situation I (wtth ¿t = O) eacept e local disturbance 4t

s.

g 5%

0. ß s .' 'b

4

'

_{, ______}

4s

SItuai len 2 (wdh ¿t = constant) e!cept a local disturbance x

Yawingangle c()=20 _' Rudder angle c()=7° 52'8 Yawing angle o(r) = 20 000

Rudder angle a()= 40 4Ç'33

--HG. 3. Msnuvring aspects sailing on a straight track in nonrcstrictcd

shallow water

Track distance i km

Average heading and rudder motion \'ariation (r.rn.s. vahics) heading and rudder motion

back on to the desired course and to preclude a further drifting away from the straight track.

(iii) When with a large tanker a deviation from course occurs due to a sudden local external disturbance , due for example to

varia-tions in wind or current, because of her inertia it will take

a

considerable time to bring the ship back to her original course; a turn oUce started is bard to stop (Fig. 3.3). To get the ship back

3N.

'se/on

qs-/0'

45

6O

i'eo

°""C'

øCç.2)(i)

130

)3-0 C6).(i) O(I)i.(I) 64't2) y4C2) O C6)'(23 _O(ii)zC2)

Outer channel (length 30 km., bearing

820 jo')

Inner channcl (length

54

km., learing

5:1 2°)

* Notrecorckd duc to breakdown of echo sounder.

TADLEl. SMUNC DEIfAVIOUR CM' 1'ÓUR.TANKI%5 IN ThE.APrftOACII CHANNELS

o Tanker Wind direction Forca Beaufort Visibility Speed in knot$ Mir.linun% keel clearance. : o(S) i .. ssw -poor 516

*

o

o 39

o ,

436

o ..

3 34.

o i

! 07

li NNE 2 good xo6 H 13

! 24

3 41 1 26 0 22 Ill E poor 7.8 i..

2.23

6 55

I 27

j 20

IV NNW good 82

52 22

9 II

5 27

3

36 i o , o , .o . i 8G Il 2 12

9 39

4 .30. Il . 8.i

ii

o

sG

418

454

242

III .. : 14

5 57

9 29

8 3

4 03

IV I . io si

oç

6 ,6

p37

040

NO.3 MANUVRING IN THE

_{CHANNELS TO EtIROPOORT 30Ç}

on. the centre-line the amount ofi-udder action which is necessary may be considerably greater and the deviation_{from track, i.e. the} amplitude ofthe oscillations, _{ca be relatively large.}

When a tani er is sailing_{rn a nrros channel a iurrher source of} disturbance will _{occur in front of the ship due to the influence of} the channel houndar]es From model experJmeits ¡t 'ppears that the amount of rudder

_{action and course dejation ma Increase}

In the case of rclatie1y large _{constant cross motions (Fig 3 4)}

Actual 'alues of the abo'e prametcrs, from measurements on

board VLCC's in the Europoort channels are given in Table J. 4. RESPONSE TO RUDDER ACTION. Information

_{on the response of a}

ship to rudder action is usually determined by means of turning circle, spiral, zig-zag and line curve tests, but this information vi1l be

_ogreater

valtic for rnanuvring in harbour or for programming n automatic pilot

than for rnanuTing problems

_{in a channel under changing external}

con-ditions For the Europoort channels _{ith their chmging local conditions,} speed and keel clearance are important factors influèncthg the response.

As long as she has steerage _{-ay a ship may navigate the channels in} various ways, but for constant _{ropeIler revOlutions there are limits to} the admissible speed. The limit, here defined as a critical speed, is when the chip in the g1en circt n-stances can be kept on coutse ithout crossing the ch-umel boundaries, b rudder action oni> From model tests in NctnerJand, Ship Model Basin it sas SOOTI found that fo'- gnen cternaL conditions there seems to be both a maximum and a minimum critical speed, _{1'a and r1, influenced kv such factors as the mcthd of steering,} andfor big.ships also b' the capabilities of the human operator.

In a narrow channel a decrease in under-keel clearance, for instance

from 20 to i o

_{per cent of the ship's draught, remarkably narrOws the}

range bet eers and _{Full-scale in%estlgations confirm that for} the aCtual keel clearance hi the Europoort channels the range of speed lies roughly between _{ç and i 2 knots. If the speed is lower than r,} how-cver, it is still possible to make effective course correction by a sudden increase in propeller revolutions. This is illustrated in Fig. 4 which shows the results oía model test In unfaourable_{conditions a change ol} helms-man may improve the situation, sometimes with remarkable effect as has been found in practice;

. _{THE RESPONSE OF HUMAN OPERATORS TO TRACK DEVIATIONS. The}

pilot boards the ship before the outer-channel is entered, so that during the passage_{mancuvres are executed jointly by the pilot, who gives the} course and speed orders, and the helmsman, who has _{to keep the ship on} the ordered_{course. The w-av in which this is carried out and the resulting} track of the ship clearly depend on huihan factors, the most important being quick reaction, an ability to anticipate and the seamanship of both pilot and helmsman. These factors differ great Iv between individuals and parthel-ships see also sectiOn

_i).

track of the stern

test I with constant number _{test 1/} of prooeller revolutions

₇

Ns49/min.

-

/

test 2 N5 49?3-49/min. over

Lese 2 250 sec. citer t0

/

test 3 _{Nt4992.49/m,n. ,f} over 253 sec

/

alter t0

/

_{test 3}

I,

3OM

-. j_

position stern 400 icc. alter t0

1-s,

L! O

/

/

,

f-250 Sec. alter to _{rudder deflection from 635°sb.} to 50

£00 sec.

600 sec.

306 _{L. A. 3OEL AND}

C. DON

at to _{rudder deflection from 60 to &=35°z.b.} f.

sMp 200.000 tdw., _{draught 62, depth 1.1 s draught} speed S knots

rudder angle 6=0

O 200M

LtG. _{. Effect of a sudden increase of propeller}

revolutions during rudder

deflection

This subject has been studied both practically and theoretically _and numerous data have been

acce.únujated The influence of human factors can be illustrated by an .exampk (Fig. g) obtained

from observations made on board two tankers of similar_{size (2Oo,o}

NO. 3 MANOEUVjN _{IN THE CHANÑELS TO EUItOPOORT}

307

speed io knots) in the

outer channel under almost identical external conditions (north-sesterJ _{inds, force 6 Beaulort)}

-md the same tidal-phase, but _{ith different}

combinations of pilot 'nd helmsman Dorrnga

passage of 12 kilometres the _{imount ol rudder action}

c7(&)

_{necessar) br}

tanker A was only ball that needed by tanker _{B. lt pìay be noted that the} a'erage salues of rudckr and

_{course angle for the to tankers}

ere equal

and that the

_{'ariations in course angle 84e.) did not greath diflLr}

lt is

reman able that tanker B made use ob maximuni starboarci rudder de-flectioris on several Occasjóns.

PIG' ç. Recordings on two tankers sailing the _{same track in the outer channel}

For manuvring

_{on a straight track, pro-iding the pilot with}

position-Information is _{import-nit in particular ship's distance to the centre line} This ' ill be discussed_{in the nevt section}

A summar) _{is gien in rable I of the sailing}

beha%iour of four 200,000

ton d;w.t. tankers in

_{the channels to the Hook of Holland. The}

para-meters described _{in section 3 aboie aie dttailed}

for to straight tracks

in the outer cham-el oser a distan _{of 20 kilometrLs and}

_{in the inner}

channel over io kilometres

6 _{NAVIG'tTIO\ 'tL '1DS FOR TH EUROPOORT}

'l'PRO CH Pros iding the pilot _{ith 'nformat,oxi ori the ship's dictarice fron-i the}

centre line is part of the general _{problem of navigational aids}

308 _{L. A. KOEL} AÑD C. DON}

VOL. 24.

entrance. It is beyond the scope of this paper to discu5 in detail _{the results} of several studies

on the subject, but from these studies a number of re-quirements have been formulated, four of which _{arc of particular in} -terest:

Information concerning the distance of the ship from _the centre-line of the fairway must be available on the bridge_{instantaneously} and continuously.

The ship's position in the channel must be known _Continuously and with minimum delay.

Additional position fixing systems must be available _{to preclude} the interruption of data_{supply to the ship.}

Large ships cannot in principle be permitted

_{to stop in the}

approach channel. It is clear that

a single system cannot fulfil all these requirements and the navigational equipment for the àpproach to Euz-opoort consists of a combination of systems, Decca, radar, buoyage and lights

_{(Fig. 6.}

----

-FIG. 6. Navigational aids for the approach of Europoort

The southern side of the outer channel is marked by

_conventional

light buoy's equipped wit-h radar reflectors, their _{relative distance being}

approximately 2 n.m. Manuvring

_{a deep draught vessel through the}

channel is a high-tide operation and consequently the_{ship will always} manuvre downstream of the buoys. The_{centre line of the inner channel} is indicated by_{a leading line of lights.}

To assist navigation _{in reduced visibility a shore based radar system} has been fl operation for several

_{years, the outer station of the radar}

chain along the Nieuwe Rotterdamse Waterweg being _{sited at the Hook} of Holland signal tower. The coverage of this station in the seaward direction did

_{not, however, meet the above}

mentioned requirements and for this and several other reasons a new radar system is being designed. Meanwhile the Hook of HollncI_{station, PILOT MAAS, has been}

equipped

with a new

_{antenna and multiplicative}

receiving system. A higher

resolution in bearinghas thus_{been obtained which extends the coverage} of the station_{to a point halfway along the}

infor-NO. 3 MANOEUVRING IN THE CHANNELS TO EUROPOORT ₃₀₉ mation is passed by a v.h.f.

communication link between pilot nd station.

\Vith the new system the pilot

_{takes a transponder on board which is}

hoisted on the mast. The ship is identified by secondary radar tcchniques. Position information provided by the shore based radar _{station is passed} via the radar-frequencies to the ship and presented _{numerically to the}

piIot.on a small box, in the

_{form oF cartesian}

coordinates representing distance from tue centre line of the channel and distance_{left to go to the} next change in direction of the channel centre-line.

Although all vital _{parts of the radar system are duplicated, including} an instantaneous change-over in case of breakc!own, it has been considered necessary to have an additional independent navigation System available to ensure optimum safety in respect to position information. After ex-tensive study it was decided to utilize a Decca Navigator Chain _planned for radio position fixing in _{the southern part of the}

North Sea. This serves also as an electronic navigational aid (Fig. j) as the siting of the trans-¡nitter stations was based on the requirements already mentioned.

lt is vell known that the_{combination of a Master and}

a Slave station in a hyperbolic electronic _{position fixing system radiates}

a pattern of hyper-bolic position lines, the perpendicular bisector of the base line connecting the Master and Slave stations being a straight line. _{In this case the} trans-mitter stations have been sited so that the perpendicular bisector of the red base line coincides with the centre-line of the outer channel, which is therefore marked by an electronic leading line. In a Decca system, since all

- JIG. j. The Europoort hyperbolic _{electronic position fixing} sstem

310 _{.. L. A. KOEL AND}

C. DON . _{VOL. 24}

Slave transmissions

are phase-synchronized vith the Master transinssjon an two Siáve stations

are aIsoph3se.vnchroIj?e(1 and thus atso radiatea

pattern of hyperbolic _{position lines. 13y siting the}

Green trann1itter

in

such a pocition that the perpendicular bisector of the_{ReJfGrecn base line} coincides

_{ith the centre line of the inner channel,}

this also can bi..

marked byan electronic_{leading line.}

Since, hocer,

_{it is not possible to obsere the hperbolic}

pttern

rac1iated by thet _{o slave stations on the standard Decca receis er,}

a special attachment to thc _{standard Marl. i 2 receiver has been designed}

br the

purpose. This is called the 'Brown box' because the _SlaveSlave hyper-bolic pattern

_{is printed in bron on the chart The bron box}

rncorpor-ates three decorneters, one each for the red, _{green and bro%n patterns} The s)stern _{is %ery simple in us and the}

pilot brings the rehtl\J.

_small

'bro-n bo

on botrd

_{ith him It}

is connected to the Mark _{i 2 recels er} with a long lead v.hich enables the pilot _{to carrs the box ssith I im to a} COnsenlent position on the bridge

_{B keeprig the red ]ndicatorstead on}

pre-dctLrmlned reading he_{can fohlos the centre-line ofthe}

82° 30'

chan-nel. When at

_{a certaj}

distance, point Ki, course has to be altered _to

¡12°, the pilot keeps his

_{brown indicator on another pre-determined}

readin

_{in order to follos the}

centre-line of the i i a° channel Distances along the two centre lines are indicated by the green pattern.

. SIMULATOR STUDIES. In investigating the _{problem of}

manceuvring a large ship through the channels three_{elements can be distiniished:}

the ship and her characteristics,

the position fixing systems with theh accuracies and characteris tics,

4u) the humiri operators handling the ship,

_{the pilot/helmsman}

combination

The, first two _{can be observed separately, both}

theoretically arid iñ practice As it was pr-tct[callv

_{irnpocible to stud' the}

combination of a1l

three elements at sea, research was carried _{out on the prototype}

manuv-ring simulator _{installed a}

the Institute for Technical Constructions in Deift, which resembles the flight

_{stmuNors used b) the}

aircraft rn-dnstry.34 The_{results provide}

an important contribution for the interpre. tation of observation.s_{in actual ship handling.}

The ship's _{characteristics are}

programmed for the

_{computer part of}

the simulator

_{in the form of}

equations of motion. In

_{a mock-up of a}

navigation bridge, thL wheel, _{compass .nd seseral other}

naugational aids are at the disposal of' the man handling the ship. An_{important feature of} the simulator_{is the s isual displa w hich prcsentc an Image of the}

sea and

coastline, including the leading line; a display of electronic _navigational aids such _{as radar, hsperbolic}

systems &c _{, can also be simulated As in} real life, the navigator gives manuvring

orders, speed, wheel and course

to steer, and the

_{responses to these orders}

arc fed into the

_computer

NO. 3 MANU\'RING IN

_{THE CHANNELSTO EU1OPOORT}

311

equations of moton. The ru1rs óf.

_{the computations}

_{are fed back to}

adjust the 'sua1 dicph _{The simulationis in retI time and a continuous} reco3d is made of the track thdc gQod, engine and rudder _movements,

course &c A fe

_{of the special SitU3tiOnS and n1anaures which have}

been studied in this way are worth mentioning. .

Thefirst investigations

_{were on Inuvring in the}

_{i i 2° channel, and} to get a better insight into the influence of the human factor the tests ere carried out with ¡flore than one pilot/helmsman combination. Pilots were requested to keep the ship _{on the ccntreline ofthe channel under}

various external conditions. A 'brown box' was included in the simulation _to investigate manuvring along an electronic ladng line coinciding _vith

the centre-line of the channel, normal dalight as

ell as sky 'sac

conditions at night being simulated.

In this group of _{Jfl\eStigations in particular, remarkable discrepancies} Were sometimes obsercd

_{hich shocd}

_{a strong correlation with the} human Operator handling the ship. The brown pattern is three times nal-1er than the red, shtch _{implies a moresensitie indication ofthe} centre-]ine.

The simulator was used in another group of investigations to study optimum sensitiity In the course of hese _{1n%estIgtIons it}

_{%as poed}

that the cimulator could be_{a '.er uceful ifl..trument for tialnlngpeop'e}

to mancLuuc large ships and a special

_{training programme is nos bcing}

designed Al! rest.lts hase not 'et bccn analysed in detail, but it can he

sted as a preliminary conclusion that the width of the path

recorded

under average condiUons

_{was about loo metres on either side of}

the centre-line, a uiguic which is quite in accordance _itl

_{the ship}

rnoe-ments obser-ed in präctice.

8. GINEitAL. At

_{present the pilot}

_{is already on board whçn}

a

VLCC is entering the

_{outer-channel, according}

_{to the owners' wish}

either from a pilot vessel in the calais Roads or by helicopter seaward of the outer channel. _{Considering the importance}

of the human operator

in rnanuvring and

_{navigation probleiris, the timely boarding of the pilot}

means an optimum use of the available navigation aids.

Experience has shown that

_{manuurring hi the approaeh channels}

mal cs se ere deimnds _{on both personnel and}

equipmen- in the human sphere much depends on the ability of the pilot and the bridge-personnel, in particular the helmsman. The pilot alone _{cannot complete the tasks of} interpreting the n't igational aids,

_{gi ing the rnnu ring orders}

(some-times with slight alterations)

_{and keeping}

constant contro! of their

execution. A trained helmsman _{is absolutely necessary. In}

a number of

cases it became eident that the_{helmsman was not sufflcientl}

competent and his replacement duringpassage_{was necessary.}

In the nautical and technical spheres cornpkte familiarity with the chart is essential (the Dutch ones far preferred) and with the sailing direc-tions covering the approaches to the harbour. The navigation equipment must be in good condition, in particular the Decca Mark i a receiver, the

.312

_{L. A. }OEL AND C.}

DON _{VOL. 24}

compass and the rudder deflection indicator. A reliable _{Communication} system with shore stations and other ships is also required.

Although much of the shore_{equipment for channel navigation is still} of a provisional character, it appears from _{many measurements on board}

tankers that if the basic

_{requirements are met navigation}

is not only

feasible but straightforward But human

_{error is still a factor to be}

con-sidered and the_{construction of the channels and the}

arrangement of the system of navigational aids has been _{designed to reduce this failing}

as far as possible. An optimum relationship has still to be achieved _{between the} sensitivity of navigation data _{and their.presentation}

_{on the bridge, with}

respect to methods of steering and the

sailing characteristics of thevessel. Based on experience and prototype studies, some modifications _have already been carried out in the channel. An example

_{is the recent}

de-crea.se from i 800 to

_{2oo nietres in the width of the}

outer channel as originally planned. lt also appeared that tankers needed a greater width halfway along the _{inner channel in connection with the change over of} navigation systems (from Decca _{or radar to leading line}

navigation) and also in relation_{to the other shipping in the area. At this point the width} was therefore increased from _{oo to soo metres. The final}

dimensions of the approach channels are subject to further studies.

REFERENCES

I

Dutch papers at XXJst arid XXHnd International Navigation_{Congreases, Stockholm,}

zGç, SCCLOR 112,Paris, 1969Section113.

2_{Hook, J. P. The}

rnanuvrabilit). of ships on _{a straight course. Report No. 99S,}

August 1967, Netherlands Ship Research Centre T.N.O.

3_{Manen, J. D. van}

(1970). _{The Netherlands Ship Model}

Basin, ship handling and manceurring simulator, lot._{Shipb. ¡'logrear, 17.}

4

Manen, J. D. van, and Hook, J. P. (1970). A three.dimensional _{simulator for}