The manoeuvrability of ships at low speed

NEDERLANDS SCHEEPSSTUDIECENTRUM TNO

NETHERLANDS SHIP RESEARCH CENTRE TNO

SHIPBUILDING DEPARTMENT

LEEGHWATERSTRAAT 5, DELFT

*

THE MANOEUVRABILITY OF SHIPS AT LOW SPEED

(DE MAÑOEUVREERBAARHEÏD VAN SCHEPEN BU LAGE SNELHEID)

by

Ia.J. P. HOOFT

Netherlands Ship Model Basin

and

IR. M. W. C. OOSTERVELD

Netherlands Ship Model Basin

Issued by the Council

REPORT No. 138 s

May 1970

Het bestúreñ van zeer grote tankers in havens en riviermonden baart vele zorgen Immers bu toenernende grootte van het schip neemt enerzijds de laagste sneiheid toe waarmee grote tankers nog op koers gehouden kunnen worden anderzijds kan alleen sleep-boothuip geboden worden bu verminderde scheepssnelheid

0m het schip toch bu zeer lage sneiheid te kunnen besturen is het gebruikehjk orn voor korte tijd het aantal schroefomwente lingen te verhogen waardoor de effectiviteit van het roer groter wordt. Helaas neemt tengevolge van deze manoeuvre de scheeps-sneiheid ook toe.

Het dod van het in dit rapport weergegeven onderzoek is ge weest de winst in manoeuvreerbaarheid te bepalen die verkregen

wordt door bu een zekere roeruitsiag ook het schroeftoerental te verbogen. Daärtoe wetden modeiproeven uitgevoerd in de

ondiepwatertank van het N.S.F. teneinde de krachten in langs- en dwarsrichting en het giermoment ùitgeoefend op het model te bepalen voor verschillende scheepssnelheden, schroeftoerentallen

en roeruitsiagen. Tevens werden stuwkracht en askoppel

ge-meteñ.

Met dealdus verkregen rneetgegevens was het mogelijk een

dia-grarn te ontwikkelen, waaruit men kän afleideri hoe groot de

kiacht is, die het rer opwekt bij een bepaalde scheepssnelheid, roerhoek en toerental orn verstorende krachten ten gevolge van

wmd stroom golven etc te cornpenseren

Tenslotte zijn enige draáimanoeuvres van het schip bij lage

sneiheden berekend. De úitkomsten van deze berekeningen läten de invloed z.ien, die een toename van het schroeftoerental heeft op de wendbaarheid en de snelheid van het schip.

HET NEDERLANDS SCHEEPSSTUD1ECENTRUM TNO

Operating very large tankers in harbours and river estuaries is a matter of great concern For with increasmg size of the ship on the one hand the minimum speed at which large tankers still can be kept on course increases on the other hand tugboat assistance can only be given at decreased speed of the ship

In order to handle the ship at very low speed it is common

practice to increase the number of propeller revolutions for a short

period thus enlarging the rudder effectiveness It is a pity that the speed of the ship will increase also as result of this manoeuvre

The purpose of the investigatiOn presented in this report has been to determine the benefit obtained from increasing the pro peller rpm for a certain rudder deflection Therefore model tests were carned out in the Shallow Water Basm of the N S M B to

determine the longitudinal and lateral forces and the yawing

moment acting on the model at different speeds, propeller rpm's

and rudder deflectiôns. At the same time propeller thrust and

torque were measi.irèd.

With the information thus Obtained from the tests it was pos-sible to construct a diagram from which the force generated by

the rudder at a certain speed rudder deflection and propeller

rpm can be derived in order to compensate the disturbing forces dueto wiñd, current, waves and so on.

Finally some turning inanoeúvres of the ship at low speed have

ben calculated. The results of these calculations show the in-fluence of the increased propeller rpni on the turnability and

speed of the ship.

THE NETHERLANDS SHIP RESEARCH CENTRE TNO

CONTENTS

page

LiÑt Of symbols 6

Summary

7

1

töciiicion

7

2

Hull form and propeller characteristics of tanker model

7

3 Teslarrkdout

8

4

Discusulon of test results

9

5

Manoeu'iiing at low speeds

.. 10

6 COnclUsions 11

Réfèrencès

il

LIST OF SYMBOLS

f(t), g(t)

Functions dependent on mass, momént of inertia and

hydrodynarnic characteristics of the ship

¡

Characteristic length

v(t)

Duft velocity of ship

C

Rudder coefficient, C = Y/sin(5 ö0)

N

Yawing rnomeñt

T

Propeller thrtust

T0

Ptopeller thrust for self-propulsion of ship

V

Ship speed

X

Longitudinal fOrce.

Y

Lateral force

Rudder angle

ô0

Rudder angle for zro ruddet force

i(t)

Heading of ship

THE MANOEUVRABILITY OF SHIPS AT LOW SPEED

by

IR. J. P. HOOFT

and

I. M. W. C. OOSTERVELD

Summary

This report deäh with the manoeuvrbility of a 65,000 dwt tanker at low speed. The influence of an increase of the propeller rpth on the forces and moments actmg on the ship at different rudder angles has been determined From these tests it was concluded that the ship can be handled very well at low speeds by increasing the propeller rpm.

Fmally the result of an analysis of the manoeuvrabihty of the ship at low speed and with increased propeller rpm is given

i

Introduction

The minimum speed at which large tankers can be kept

on course increases with increasing size of the ship.

Besides, with increasing tize of the ship, useful tugboat

assistance can only be given at decreased speed of the

ship From these considerations it is evident that the

handling of very large tankers in confined areas

(har-bours, river estuaries) becomes a matter of great

cOncern.

To the experience of several pilots, however, large.

tankers can still be hand-led at very low speeds without

tugboat assistance (see [1]). To handle the ship at very

low speed, it is common practice to enlarge the rudder

effectiveness by increasing the number of revolutions of

the screw propeller or by short brsts of increased

propeller revolutions. However, the speed of the ship

will increase also during this manoeuvre which is an

inconvenient circumstance.

This' report deals with investigations performed at

the Netherlands Ship Model Basin, concerning the

handling of a tanker at low speed. The purpose of this

investigation was to determine the benefit of coupling

the propeller rpm to a rudder deflection. Model tests

have been carried out to establish both the increase of

the rudder effectiveness and. the acceleration of the

tanker at low speed due to an increase of the propeller

2

Hull form aiid propeller characteristics of tanker

model

The tests have been carried out with a 65,000 dwt.

tanker model equipped with a conventional screw

propeller.

The principal dimensions of the ship are summarized

in table I, the hull form and the stern arrangement are

given iñ figure 1.

TabiC, I. Principal' dimensions of tanker

7

O APP _{20 FPP}

Fig. 1. Body plan and stern arrangement of tanker.

Length between perpendicular L 248.27 m Length on water une LWL 253.62 m

Breadth moulded B 32.97 m

Draft rhoulded T 13.15 m

DiSplacement moulded ¿1 86,296 m3

CCntre Of buô'añëy' frôni FP 119.10 m

Rudder area A 47.00 m2

LIB 7.53

BIT 2.51

0.8017

The propeller design for the ship was based on 24,600

metric DHP at 90 rpm and a ship speed of 16.5 knots.

The screw was designed according to the circulation

theory for wake-adapted propellers.

'the principal full-scale characteristics of the

pro-peller are given in table II; further details of the screw

propeller are presented in figure 2.

Table II. Propeller characteristics Diameter.

Pitch at blade root Pitch at blade tip Pitch at 075R Pitch ratio Blade area ratio Number of blades

3

TestS carried out

Resistance and self-propulsion tests Were carried out

with the tanker model in the Deep Water Basin of the

N.S.M.B All mdel data were extrapolated to

full-scale ship values using Schoenherr's friction coefficients

with an addition öf 0.00035 for correlation allowance.

For turbulence stimulation, a trip wire of 1 mm

dia-meter was fitted to the, model at a section 5 per cent

of L aft .of fore perpendicular. The model was tested

in the loaded conditiom

Further, model tests were conducted in the Shallow

Water Basin of the N.S.M.B., to determine the fòrces

and moments acting on the model at different

pro-peller rpm's and rudder deflections. The waterdepth in

the basin corresponded to a waterdepth, at fUll scale,

of 35 m.

Fig. 2. Particulars of propeller.

During the tests, the model was restrained on a

straight. course at zero drift angle. The model was

at-tached to the towing carriage by means of a

longitu-dinal and two lateral arms as shown in fig. 3.

FFA

Pitch distribution

in percent

175.1.6.

Fig. 3. Set up of models tests.

FAL and FFL = Strain gauges for mesaurement of the lateral forces.

FFA = Strain, gauge for measurement of the

axial force.

CG = Centre of gravity..

The following quantities were measured:

The longitudinal and lateral force and the yawing

moment on the model with strain gauges mounted

on the longitudinal and lateral arms.

The propeller thrust, torque and rpm.

The rUdder deflection.

The speed.

The forces and moments acting on the model were

measured at speeds corresponding to 0, 2.5, 5.0 and

7.5 knots and at 88, 77, 63 and 45 rpm of the screw.

8.146m 4.939 m 6.146m 5.979m P/D 0.734 A E/Ao 0.624 4 APP. F PP

4

Discussion oftest results

The propeller thrust and absorbed power for differeiit

ship speeds and propellet rpm s are given in diagram

i (See appendix).

The results of the measurements of the forces and

moments acting on the model are given in the

dia-grams 2, 3 and 4.

In diagram 2 the longitudiñal force X acting on the

ship mOdel is given for the ship's speeds considered

V, = 0, 2.5, 5 and 7.5 knots, as a function of the

rudder angle ô with the propeller rpm as a paiametet.

In addition curves according to the following

rela-tiOn are presented in this diagram:

X = Tcos(ôô0)T0

where T0 and ô0 denote the propeller thrust fôr the

self-própulsioiì point of the ship and rudder angle for

a straight course ahead respectively. This equation was

based on the assumption that the fòrce on the rudder

is determined by the deflection of the propeller jet due

to the rudder angle. See fig. 4. At increasing ship speeds

the rudder force will also be caused by the speed of

advance of the rudder due to the main stream velocity.

Over the range of ship speed s considered here,

how-ever, this effect on the longitudinal force is negligible

From the results given in diàgram 2 it can be seen that

for the ship speeds and propeller rpm considered this

relation approximates adequately the test results

The lateral force Y acting on the ship is given in

diagram 3 (see appendix). At increasing ship speeds the

rudder force will not only be caused by the deflection

of the propeller jet due to the rudder angle but also by

the speed in advance of the rudder due to the main

stream velocity. Here the effect of the main Stream

velocity is not negligible and therefore the lateral forçe

Y was approximated by:

Y

Csin(öô0)

in which C depends on propeller rpm and ship speed.

Fig. 4. Components of the measured longitudinal fórce

X = TCOS (ò-50)T,.

T = Propeller thrust

T, = Ship resistance

ô = Rudder angle

At zero speed of the ship, the coefficient C will be

a measure for the way in whibh the rudder succeeds in

deflecting the propeller jet, Curvés according to this

relation are presented in diagiam 3.

Finally, the yawing moment N acting on the ship and

curvesaccording to the relation

N

Y.l = C.lsin(ôô0)

are given in diagram 4;

Here ¡ denotes the distance obtained experimentally

between the centre of gravity of the ship and the point

of application of the lateral force. The distance 1 was

not influenced by the ship speed V,, the rudder angle 5

and the propeller rpm

With the aid of the results in diagram 3 and the

corresponding propeller thrust T it is possible to give

the coefficient C = Y/sin (ô

ô) as a function of the

propeller thrust with the ship speed and the propeller

rpm as parameters. See figure 5.

A

's'

70 _Limiting

IAI.

dAt 4á1 lI

80RPM Line for power maximum 100 200 300 ¿00

T. propeller thrust (b tons). Fig. 5. Relation between lateral force coefficient

C = Y/Sin (ô--ô,), Ship speed, propeller rpm and thrust.

In addition, the curve for the free running speed of

the ship and the limiting line for maximum power are

indicated in this figure.

The fact that the machinery will not work below a

certain number of revolutions is not taken into account

in the results given in this figure. This number of

revo-lutions depends strongly on the particular kind of

machinery considered. With the aid of this figure 5 one

is able to derive the forces generated by the rudder

500 Loo 300 C D 200 C. w 100

'o

Thus it can be determined quantitatively to what

tion of turning manoeuvres of the ship are given in

extent disturbing forces due to current, waves, wind

figures 6 through 8.

and so on can be compensated.

to indIcate the wäy for entering the figure the

following example may be useful. For this ship with

____________________________________

a speed of 7.5 knots it can be derived in figure 5 from

the intersection of the steady ahead line and the speed

curve that at a rudder angle (5 of 30 degrees the lateral

force Y amounts to be 110 x

55 tons. It can be

assumed that in practibe this ship never gives troubles

in relation to the rudder effectiveness at a speed of 7.5

knots. The conclusion can be drawn that a rudder

force of 55 tons i enough fòr controlling the ships in

all circumstances. From figure 5 it can also be derived

that at zero speed of the ship and with increased

pro-peller rpm (rpm equal to about 65) the same lateral

T ___________

force can be obtained as in the case of the ship running

o

steady ahead with a speed of 7.5 knots. In both cases

the rudder angle ô was assumed to be eqüal.. FrOm this

Fig. 6. Turnability of ship at low speeds.

o - - 100 200 ' 300 400 ' 500 600 700 60

E z

comparison it can be concluded that the ship can be

handled properly at very low speeds if the propeller

6

rpm is increased during manoeuvring.

In addition it can be seen from figure 5 that at a ship

speed of 7.5 knots the rudder effectiveness or the lateral

force Y can be increased about 2 5 times by increasing

the propeller rpm from .37.6 to maximum.

3

5

Manoeuvring at low speeds

Some manoeuvres of the ship at low speed will be

calculated now These calculations will be based on the

assumption that the motions of the ship are

propor-tional to the rudder force. Then the ship motions can

be written asc

i(t) =f(t).Y(ô)

v(t) =g(t)Y(ô)

where fr(t) and v(t)denote the ship's heading and the

drift velocity respectively.

The adequacy of describing the ship's motions by

these relations were extensïvely discùssed by Brard [2]

and Hawkins [3].

The functions f(t) and g(t) can be determined from

the rudder effectiveness K and the time constant T and

depend on the mass, the moment of inertia of the ship

and the hydrodynamic characteristics such as the added

mass and' damping. For an analysis of these functións

reference is made to the investigations performed by

Davidson and Schiff [4], Nomoto [5], Norrbin [6] and

Shiba [7]. The K- and T-values of the ship under

dis-cussioñ were already given in [8].

With the aid of the above relations, for the heading

and the drift velocity of the ship, the turning

manoeu-vres can be' derived. Some of the results of the

calcula-E30 z z 30 25 15 E10 z z u. u, z 4 z ADVANCE IN

rn----Fig. 7.

Turnability of ship at low speed (5 knots) with

in-creased propeller rpm and at a rudder angle of 20 degrees.

Fig 8. Turnability of ship at low speed (2.5 knots) with

in-creased propeller rpm and at a rudder angle of 20 degrees.

500 -

IffIIIItV(.JIrAiTI.!I U

4(I _________________________ 30 0

FII.1f4;l*:4(.iIM,1

U

_____wvIá

t

--

u,.

..#..

IJILIJ RUDDER ANGLE:20°

I50TIAL RUDDER

SPEED 5KNOTS ANGLE 20°

46RPM (INCREASED)

200 SEC. AFTER ECUTE-

/

37.6RPM(INCREASED) (

FXCUTu OF RUDDER ANGLE _7

,

265 RPN (NOT ÍNEASEÖ) /TIMEOSECONDS

__._-INITIAL RUDDER SPEED 2.SKNOTS ANGLE 20° CEA5ED

200 SEC. AFTER EXECUT _/

(L z -(NOI INCREASED) -200 600 700 600 ADVANCE IN

n

so too ADVANCE IN

m-

'sa 200 250 300 350 400

From figtire 6 it can be seen that the turabiity of

the ship does not change very much with decreasing

ship speed. However, the handling of the ship at low

speeds will still give difficulties because the rudder

forces are not large enough to compensate the

dis-turbing forces due to wind, current and other

influen-ces. This fact has also been shown by Welnicki [9].

Therefore, as stated in the previous sections, the

pro-peller rpm has to be increased in order tO enlarge. the

rudder forces. The influence of an increase of the

pro-peller rpm on the turning manoeuvre in still water is

shown in figures 7 and 8 The corresponding increase

of the ship speed is also indicated in these diagrams.

6

Conclusions

At very low speed of the ship and with increased

pro-peller rpm the same lateral force or moment on the

ship can be obtained as in the case of the ship running

steady ahead at

7.5

knots. As the ship can be handled

properly at a speed of

7 5

knots, it may be expected

that the ship can still be handled properly at lower

speeds by increasing the propeller rpm. The increase

of the propeller rpm will lead to an increase of the

ship speed. This is an inconvenient circumstance.

However, by keeping the duration of increased rpm

short, thus given "bursts" of increased rpm, the

in-crease of the ship speed will remain low. The influence

of the increased propeller rpm on the turnability and

speed of the ship at low speed has been shown.

References

1. SIBLY, J, The Handling of Mammoth Tankers. Trans. Insti-tute of Navigation, May 1968.

2 Bitn, R., Manoeuvring of ships in deep water, in shallow

water and in canals. Trans. S.N.AM.E., 1951.

HAWKINS, S. et al., The use of manoeuvring propulsion de vices on merchant ships. Publication of Robert Taggert In corporated. Washington, 1965.

DAVIDSON,K. S. M. and J. L. Scrnn, Turning and course keeping qia1ities.. Trans. S.N.A.M.E.;t946:

Noserro, K. et al., On the steering qualities of ships. Interna-tional Shipbuildihg Progress, Vol. 4, 1957.

NoanniN, N. R, A study of course keeping and manoeuvring performance. Publiintion no. 45, Swedish State Experimental Tank, 196O

Siim,

H., Model experiments about the manoeuvrability and tumthg of ships. David Taylor Model Basin. Report no. 1461.

Hoot, J. P., The mànoeuvrability of ships on a straight

course. Neth. Ship Research Centre TNO Report no. 99S. Wauaciu, W., Method of estimation of wind influence upon the course keeping ability of ships with large superstructure. Trans. R.LN.A., 1963.

12

APPENDIX

¿0000-30000 DH P (rnetr 2000Ó 10000 79 63 ¡,00 300

T, Thrust

(in tons)

200 100 88Rpp, 63 ¿5 25 se 7.5

.0

25 5.0

VShip speed (in knots)

Vs.Shipspeed(in knots)

I

(D L. o U. 200 o L. 4... D) E (n C o 4.' X 100 w o L. o 300 200 X 100 40

Results of model tests:

x 88RPM

D

77 .

o 63

+ 45

- Longitud ival force X T cos ( -S0)-10

30 20 10 0 10

udder angLeS

Port 20 30 (degree). Starboard 20 X 100 O 40 40 30 20 10 300 200 X 100 O O 0 10 20 30

Diagram 2. Longitudinal force X for different ship speeds, propeller rpm's and rudder angles.

40 13 Ship speed 5kt. u 4 o ° + o + + +

Ship speed 75kt

X a u ij

-D X

:

o o + + + + +

i

3flIp

pu

V V1

__Xo

_a o

ou__.

+ + 0 30 20 10 0 10 20 30 4 I I Ship speed I 2.5kt

_i

ii

o

!'i$

oUi

T'

14

u

L 4-W D

I--

o

.n .

CL

0(5

r

200

loo

o -100 20 lo YO -10

Results of model tests:

88 RPM

o 77

o ₆₃

+ 45

- Lateral force Y= C sin(&-80)

-200

-200

-40 -30 -20 -10 0 10 20 30 40

-40 -30

-20 10

Rudder angle.S (degree). Port Starboard_ 200 100 YO -loo -200 -200

N

o Ship speed 5 kt

N

Ship speed O kt o + - Ship speed 7.5kt Ship speed 2.5kt

-.--.-,'

-40

-30

-20

-10 O 10 20 30 40 -40

-30

-20 -10 O 10 20 30 40 &

8

Diagram 3. Lateral force Y for different ship speeds, propeller rpm's and rudder angles.

0 10 20 30 40

200

loo

YO

u L. w E E C

2

D D D

4-I.

-20 10 NO -40 -30 -20 -10 0 10 20 3Ö O

Rudder angLe1 (dègree)

port starboard 20 -10 20 o + o Ship speed 7.5 kt Ship speed 2.5 kt 20

lo

N O

-lo

NO

-10 I.'

I-Ship speedskt

e 20 -40 -30 -20 -10 20 10

Ship speed O kt

o

Diagram 4. Yawing moment N for different ship speeds, propeller rpm's and rudder angles.

0 10 20 30 40

10 20 30 40

ResuLts of modeL tests: 15

X 88RPM

o 77

0 63

+ 45 N=Y.L 40 -30 -20 O O 10 20 30 40 3b -20

-io

PUBLICATIONS OF THE NETHERLANDS SHIP RESEARCH CENTRE TNO

PUBLISHED AFTER 1963 (LIST OF EARLIER PUBLICATIONS AVAILABLE ON REQUEST)

PRICE PER COPY DFL.

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Reports

57 M Determination of the dynamic properties and propeller excited vibrations of a special ship stern arrangement. R. Wereldsma,

I 964.

58 5 Numerical calculation of vertical hull vibrations of ships by

discretizing the vibration system, J. de Vries, I 964.

59 M Controllable pitch propellers, their suitability and economy for large sea-going ships propelled by conventional, directly coupled engines. C. Kapsenberg, 1964.

60 5 Natural frequencies of free vertical ship vibrations. C. B. Vreug-denhil, 1964.

61 S The distributiOn of the hydrodynamic forces on a heaving and pitching shipmodel in still water. L Gerritsrna and W. Beukel-man, 1964.

62 C The mode of action of anti-fouling paints Interaction between

anti-fouling paints and sea water. A. M. van Lónden 1964.

63 M Corrosion in exhaust driven turbochargers on marine diesel

engines using heavy fuels. R. W. Stuart Mitchell and V. A. Ogale, 1965.

64 C Barnacle fouling on aged anti-fouling paints; a survey of pertinent literature and some recent observations. P. de Wolf, 1964. 65 S The lateral damping and added mass of a horizontally oscillating

shipmodel. G. vanLeeuwen, 1964.

66 S Investigations into the strength of ships' derricks. Part I. F. X. P. Soejadi, 1965.

67 S Heat-transfer in cargotanks of a 50,000 DWT tanker. D. J. van der Heeden and L. L. Mulder, 1965.

68 M Guide to the application of method for calculation of cylinder liner temperatures in diesel engines. H. W. van Tijen, 1965. 69 M Stress measurements on a propeller model for a 42,000 DWT

tanker. R. Wereldsma, 1965.

70 M Experiments on vibrating propeller models. R. Wereldsma, 1965.

71 5 Research on bulbous bow ships. Part II. A. Still water perfor

mance of a 24,000 DWT bulkcarrier with a large bulbous bow. W. P. A. van Lanimeren and J. J. Muntjewerf, 1965.

72 S Research on bulbous bow ships. Part II. B. Behaviour of a

24,00( DWT bulkcarrier with a large bulbous bow in a seaway. W. P. A. van Lammeren and F. V. A. Pangalila, 1965.

73 S Stress and strain distribution in a vertically corrugatód bulkhead. H. E. Jaeger and P. A. van Katwijk, 1965.

74 S Research on bulbous bow ships. Part I. A. Still water investiga-tions into bulbous bow forms for a fast cargo liner. W. P. A. van Lammeren and R. Wahab, 1965.

75 S Hull vibrations of the cargo-passenger motor ship "Oranje

Nassau", W. van Horssen, 1965.

76 S Research on bulbous bow ships. Part I. B. The behaviour of a fast cargo liner with a conventional and with a bulbous bow in a sea-way. R. Wahab, 1965.

77 M Comparative shipboard measurements of sUrface temperatures

and surface corrosion in air cooled and water cooled turbine outlet casings of exhaust driven marine diesel engine

turbo-chargers. R. W. Stuart Mitchell and V. A. Ogale, 1965. 78 M Stern tube vibration measurements of a cargo ship with special

afterbody. R. Wereldsma, 1965.

79 C The pre-treatment of ship plates: A comparative investigation

on some pre-treatment methods in use in the shipbuilding

industry. A. M. van Londen, 1965.

80 C The pre-treatment of ship plates: A practical investigation into

the influence of different working procedures in over-coating

zinc rich epoxy-resin based pre-construction primers. A. M van Londen and W. Mulder, 1965.

81 5 The performance of U-tanks as a passive anti-rolling device.

C. Stigter, 1966.

82 S Low-cycle fatigue of steel structures. J. J. W. Nibbering and

J. van Lint, 1966.

83 5 Roll damping by free surfäce tanks. J. J. van den Bosch and

J. H. Vugts, 1966.

84 S Behaviour of a ship in a seaway. J. Gerritsma, 1966.

85 S Brittle fracture of full scale structures damaged by fatigue.

J. J. W. Nibbering, J. van Lint and R. T. van Leeuwen, 1966. 86 M Theoretical evaluation of heat transfer in dry cargo ship's tanks

using thermal oil as a heat transfer medium. D. J. van der

Heeden, 1966.

87 5 Model experiments on sound transmission from engineroom to accommodation in motorships. J. H. Janssen, 1966.

88 S Pitch and heave with fixed and controlled bow fins. J. H. Vugts, 1966.

89 5 Estimation of the natural frequencies of a ship's double bottom by means of a sandwich theory. S. Hylarides, 1967.

90 S Computation ofpitch and heave motions for arbitrary ship forms. W. E. Smith, 1967.

91 M Corrosion in exhaust driven turbochargers on marine diesel

engines using heavy fuels. R. W. Stuart Mitchell, A. J. M. S. van Montfoort and V. A. Ogale, 1967.

92 M Residual fuel treatment on board ship. Part II. Comparative

cylinder wear measurements on a laboratory diesel engine using

filtered or centrifuged residual fueL A. de Moy, M. Verwoest

and G. G. van der Meulen, 1967.

93 C Cost relations of the treatments of ship hulls and the fuel

con-sumptiòn of ships. H. J. Lageveen-van Kúijk, 1967.

94 C Optimum conditions for blast cleaning of steel plate. J. Rem-melts, 1967.

95 M Residual fuel treatment on board ship. Part I. The effect of cen-trifuging, filtering and homogenizing on the unsolubles in residual fuel. M. Vótwoest and F. J. Colon, 1967.

96 S Analysis of the modified strip theory for the calculation of ship motions and wave bending moments. L Gerritsma and W. Beu-kelman, 1967.

97 S On the efficacy of two different roll-damping tanks. J. Bootsma and J. J. van den Bosch, 1967.

98 5 Equation of motion coefficients for a pitching and heaving des-troyer model. W. E. Smith, 1967.

99 S The manoeuvrability of ships on a straight course. J: P. Hooft,

1967.

100 S Amidships forces and moments on a CB = 0.80 "Series 60"

model in waves from various directions. R. Wahab, 1967. 101 C Optimum conditions for blast cleaning of steel plate. Conclusion.

J. Remmelts, 1967.

102 M The axial stiffness of marine diesel engine crankshafts. Part I. Comparison between the results of full scale measurements and

those of calculations according to published formulae. N. J. Visser, 1967.

103 M The axial stiffness of marine diesel engine cran.kshafts. Part II. Theory and results of scale model measurements and comparison with published formulae. C. A. M. van der Linden, 1967. 104 M Marine diesel engine exhaust noise. Part I. A mathematical model.

J. H. Janssen, 1967.

105 M Marine diesel engine exhaust noise. Part II. Scale models of

exhaust systems. J. Buiten and J. H. Janssen, 1968.

106 M Marine diesel engine exhaust noise. Part ifi. Exhaust sound

criteria for bridge wings. J. H. Janssen en J. Buiten, 1967.

107 S Ship vibration analysis by finite element technique. Part I.

General review and application to simple structures, statically loaded. S. Hylarides, 1967.

108 M Marine refrigeration engineering. Part I. Testing of a

decentraI-ised refrigerating instìlltiòn.

J. A. Knobbout and R. W. J. Kouffeld, 1967.

109 S A comparative study on four different passive roll damping tanks. Part I. J. H. Vugts, 1968.

110 S Strain, stress and flexure of two corrugated and one plane

bulk-head subjócted to a lateral, distributed load. R E. Jaeger and

P. A. van Katwijk, 1968.

111 M Experimental evaluation of heat transfer in a dry-cargo ships' tank, using thermal oil as a heat transfer medium. D. J. van der Heeden, 1968.

112 S The hydrodynamic coefficients for swaying, heaving and rolling cylinders in a free surface. J. H. Vugts, 1968.

113 M Marine refrigeration engineering. PartII. Some results of testing a decentralised marine refrigerating unit with R 502. J. A. Knob-bout and C. B. Colenbrander, 1968.

114 S The steering of a ship during the stopping maîioeuvre. J. P.

Hooft, 1969.