Research and scale effect in manoeuvring tests carried out on ship models Part 1: Manoeuvring tests on board destroyer HNMS MARNIX in the Bjornefjord, Norway

ARCHIEF

Dr. fr J. BALUAN

Research

on scale effect

in manceuvring-tests carried

out on ship models

Publicatie Nr 109

Nederlands Scheepsbouwkundig Proefstation

0

Lab.

v. Scheepsbouwkunde

Technische Hogeschool

Deift

Part I.

Manceuvring-Tests on board the Destroyer H. N. M. S. <<MARNIX

HESEA1ICH ON SCALE EFFECT IN MAMEUVRINGTEST

-

CARRIED OUT ON ShIP MODELS

PART I. MAN(EUVRING-TESTS ON BOARD THE DESTROYER

H. N. M. S. ((MARNIX)> IN THE BJORNEFJORD, NQR WAY. by Dr. Jr. J. BALHAN

Publication No 109, Netherlands Ship Mode] Basin, Wageningen, Holland

I. - INTRODUCTION

One of the items on the programme of the Scientific Research Department of the Netherlands Ship Model Basin comprises the research on scale-effect in manoeuviing-tests

carried out on ship models Up till now it has been customary to conduct tests in order

to determine the so-called initial steering-properties In these tests the mode1 is held parallel

to and along the centre-line of the model -basin. Measurements are taken at varying

rudder-angles either of the rudder-head torque and of the longitudinal and

ships components of the rUdder fOrce, or of the rudder-head torque and of the. two athwart-ships forces, one fore and the other aft, which hold the model on a straight course parallel

to and along the centre-line of the basin The moment of these athwart-ships forces with

regard to the longitudinal centre of gravity of the model is knpwn as the ship4.urning moment.

The magnitude of this moment forms a standard for the reaction of the model to the rudder-angle at the first instant of the first phase of turning

Large numbers of these tests have been carried Out and they have contributed in

great measure to the present knovledge of the properties of rudders (1). They are, however,

only of value for purposes of comparison with each other and concerning the first instant after

putting over the rudder, and connot he checked up on board a ship.

-Nevertheless, when making a design it is necessary to know what the steering-pro-pertiès of the projected ship will be.

Nowadays resistance and propulsion tests are carried out in a mode] basin for prac tically every projected ship, and it is equally desirable that not only initial manoeuvring-tests on a model-basis should be made, but also turning-circle tests and tests on a zig-zag course. Occasionally, for instance with harbour-tugs and warships, turning-circle tests are carried

out These tests are confined to the determination of the turning-circle under a varying

number of revolutions of the screw and varying rudder-angles.

It is however desirable during both the turning-circle tests and the zig-zag course to determine the following factors on a time-basis :

Ship's speed Ship's course

Number of Tevolutions of the propellor-shaft

Rudder-angle

-(1) For an etensive survey on mariuvring-tests with ship models, see the chapter on

Steeriiig-by Ir. J. G. Koning in c Resistance, Propu1ion .and Steering of Ships

Rudder-head torque

lift of the rudder

Resistance of the rudder

Angle of inclination of the ship.

Apart from this,it is necessary that in these, as in all model-tests, the phenomena relating to the geometrically similar objects, ship and model, should appear also in

mechani-ca1ly similar form This requirement leads to the well-known ((model-laws)) Besides

the conditions to be satisfied during propulsion-tests, the following requirements have also to be complied with.

The ship as well as the model, will, as a result of the rudder-action, turn with regard

to a vertical axis. This means that the mass moment of inertia of the ship with regard

to a vertical axis, e. g. through the centre of gravity of the ship, and the corresponding mass

moment of inertia of the model must bear the. same proportion to each other as the fifth

power of the scale. Atthe same time, however, the ship will incline with regard to a horizontal

longitudinal axis _{This means that the mass moment of inertia of the ship with regard}

to the horizontal longitudinal axis through the centre of gravity of the ship and the

corres-ponding mass moment of inertia of the model must be in the same proportion to each other, and that the metacentric heights of the vessel and of the model must bear the same proportion to each other as the scale.

These conditions make it almost impossible to carry out zig-zag courses with a manned

model, seeing that the slightest mOvement ofthe experimenter will be sufficient to alter. the above-mentioned quantities, especially the metacentric height. It is therefore most

desirable that the model should be steered by wireless Moreover the model-law of Froude

will have to be conformed to, so that the corresponding times of model and ship must bear

the same proportion to each other as the. square-root of the model-scale. This implies that,

in the ase of the model, the times required to put the fuddr through a certain angle and to

obtain a certain deviation in the course cannot be chosen freely, but must correspond with the times for the ship.

In order to investigate the influence of scale-effect in manoeuvring-tests, it is moreover

necessary to carry out these tests on a ship and on the corresponding model. _{As many}

as possible of the eight points mentioned above must be determined on one and the same

time-basis for both objects. Finally, in order to obtain a correct impression concerning

scale-effect, these tests should be extended to a number of ships and- their corresponding models.

The foregoing forms an extensive researéh, from which already a part can be offered

to those who are interested.

Hence that this publication, which 'thus forms a part of the study of scale-effect in

manoeuvring-tests on ship models, will treat: ((The Manoeuvring-tests on Board the Destroyer

H. N. M. S. Marnix in the BjOrnefiord,. Norway, from 19th to 27th November, 195l.

These tests on the ship of actual size will be repeated in their entirety on a model.

It has also been decided to cary out the same manoeuvring-tests on a Victory-ship, _{a cargo}

vessel of medium dimensions and on their corresponding models.

The accomplishment and success of these manoeuvting-tests are in considerable measure due to the exceptional co-operation which we received horn Vice-Admiral F. Stam, from the Head of the Shipbuilding Bureau, Jr. G. de Rooy, and to the- expert help and enthusiasm of the Captain, Lt. Commander Dryfhout van Hooff, the officers and crew of

measuiing-group consisted of mèmbefs of the crew of the Marnix >. On the completion of this ex periment a cordial word of thanks is due tp the authorities mentioned above as welt as to all those whose interest and energy have so largely contributed fo its success

2 MANOEUVRING-TESTS ON BOARD THE DESTROYER H N M S MARNJX

A. - GENERAL SURVEY

Before discussing the manoeuvring-tests, on zig-zag courses and turning-circles, preceded by speed-tests in order to calibrate the various instruments, we give here some

figures concerning the ((Marnix)) :

Data of the ship : :

= 95.105 m

Lo.a. = 98.503 m

B outside shell plating - 10.064 m

Depth from underside keel to main-deck = 5.872m

The lines-plan of'the vessel with positions of propellers and rudder are given in fig.. 1. Data concerning prope1ers

Diameter = 3.000 m

No. of blades 3

Pitch = 4.064 m

Developed blade area ratio = 0763

H.NM.SMARNIX PRINCIPAL OIMLNNIONS LENGTH OCR Ca 323.17 FT. 12007,4fl.P 302.02 Fl 070017 OF HULL EXTREME 03.02 FT. DEPTH TO 0*111207 NT SIDE 9.27 Ft LLL1*U1Y1iII

IIuutlJrnulI

iWUYMJI

Fig. 1 : Lines-plan with positions of pi'opellers and rudder of H N MSIlMarnixI).

As has already been nentioned in the introduction, it is necessary to know the mass moment of inertia of the ship with regard to a vertical axis and a horizontal longitudinal

axis through the ship s centre of gravity G as well as the metacentnc height MG These

values, however, vary from day to day as a result of the consumption of -fuel and water. This explains why the levels in the oil- and water-tanks were noted at the end of each day,

while on 22 11 51 an inclination-test and a rolling-test were carried out As well as this

we have at our disposal a detailed weight-curve of the ship.

By means of these data it is possible to calculate the mass moment of inertia in relation

to a vertical axis through G and the metacentric height MG for each day, besides which

the mass moment of inertia with regard to a horizontal longitudinal axis through G can be

calculated fOr. the conditions prevailing on 22.11. '51.

Prom the inc1intion-testS on.22A1.'51 the MG can be calculated by means of

the-equation :.

p.b.

tgLP=

in which zp = angle of inclination caused by the horizontal athwart-ships displa-cement of a weight p;

b distance through which p is displaced

P weight of ship

The MG thus obtained applies to the situation on 22 11 '51, so that it must first be

converted to apply to the conditions when all tanks are full. Next the reduced metacentric

heights can be calculated for the other test-dates.

The mass moment of inertia 'm with regard to a horizontal longitudinal axis through G has been determined by means of the equation below, for the conditions prevailing on

22.11.'51.

P.MG

whereby T = time in see. of a single oscillation of th ship

= mass moment of inertia in ton. meter sec..2 P = ship's weight. in tons (1 ton = 1000 kg). MG = metacentric height in meters.

In order to calculate the mass moment of inertia in ton m2, the figure obtained must be multiplied by the acceleration due to the force of gravity g in m sec2

The mass moment of inertia 'ml with regard to a vertical axis through G has been calculated for each testing-day from the weight-curve and from the figures given for the

tank-volumes Table I gives a survey of the results of these calculations

TABLET

In anticipation of the zig-zag and turning-circle tests, it may be noted here that the rudder-head torque during these tests has been determined by measuring the pressures in

the steering-cylinders. The rudder-head torque can be calculated from these pressures if

the diameter of the cylinders and the length of the tiller are known These dimensions

are given in fig 2, which shows a schematic arrangement of the above-mentioned parts

Date 'm in ton m2 I,,, in ton m2 MG in m

19-11 886000. 0.651 20-11 857000 0.641 21-11 844000 0.632 22-11 26560 832000 0.654 23-11 807000 0.648 26-11 772000 0.624 27-11 765000 0.626

42

C

PIuner

Fig. 2 Schematic arrangement of rudder, tiller and steering cylinders.

B - SPEED TRIALS

The chief aim of these tests is to calibrate the ChernikeeffAog, in order that the ship's speed during the standard manoeuvring-tests and turning-circle tests can be deduced from the number of revolutions of this log.

During a number of trips on the measured mile, the revolutions of the Chernikeeff-log were recorded on a paper strip sliding over a table the latter having been set up in the

steering--compartment in front of the rudder-head The time was also recorded on this

- strip. Henceforth the table will be referred to as the recording-table.

By means of a Maihak-torsionmeter, measurements were also taken on this trip of the torque in the propeller-shafts, as well as the number of r p m of the propeller-shafts

These revolutions were likewise recorded on the above-mentioned recording-table These

measurements were carried out in order to determine the re]atioriship between the. number

of revolutions and the power During the standard man.oeuvring-tests (henceforth zig-zag

tests) it was impossible to measure the torque-yariation of both shafts simultaneously, (1)

so that the, torque of only one shaft and the revolutions of both shafts were determined; From the relation between number of revolutions and power determined above, a fairly accurate estimate can be made of the torque of the shaft of which only the revoLutions have

been determined At the same time the relation between the number of revolutions and the

velocity was determined, so that during the zig-zag and turning-circle tests a speed, previously

fixed on according to the number of revolutions of the shafts could easily be obtained Finally, the ((plot ))-apparatus was calibrated duringthe trip on the measured mile, for it is desirable that the parth of the centre of gravity should be determined during the

zig-zag - and turning-circle tests The path can be determined with more accuracy with

the pJot> than with the aid of radar-apparatus, which accounts for preference being given

to the former.

For the ((plot)) apparatus, a sheet of paper is stretched on a glass table 1.5 mx 1.5 m.

LJ LEN S

I-NUT SCREW THREAD SCREW THREAD '

Fig. 3 Plot apparatus (schematic)

A ray of iight is projected on to this table from underneath (see fig. 3). The movement

of the light-spot thus obtained represents the path folJowed by the Chernikeeff-log Hence

the path of the centre of gravity of the ship can be determinded This movement is deduced

from the revolutions of the Chernikeeff-log and of the gyro-compass,

Ip order to carcy out these speedteSts, *e reqpire the following persons 3 time observers

1 observer to note time beginning of run 1 > tofsionmeter

1 recOrder torsionmeter

1 observer direction and velocity of wind

I recording-table

1 > Tacho-revolution counters engine-room

2 observers plot >>-table

1 contact-man bridge

engine-room

I torsion-meter

1 >> steering-compartrnent

1 > ((plot>) table.

Before beginning the trip on the measuied mile, the turning-circle was measured

at full, power and at a rudder-angle of 10°. After this a run No. 0 was made along the

measured mile in order to give the various observers the opportunity of taking their bearings

During this run no measurements were taken '1 he course followed is shown in fig 4

10° rudder was given iii order to avoid loss of speed. When passing the points A and B

on fig. 4, at a distance of I mile ahead of the meaSured mile when the ship is on the right

course, a signal is given to the contact-man on the bridge; he then notifies the other obser-vation-points that observations can be begun.

Fig. 4: Measured mile

The engines are constantly adjusted to the number of revolutions given by the contact-man in the engine-room; the latter' receives ihese figures from the contact-contact-man bridge.

This adjustment need not be carried out with very great accuracy, but is sufficiently exact

within the limits of 3 revolutions. As soon as the engines have been adjusted, the

contact-man engine-room reports this to the contact-contact-man bridge. After this no more regulations

to the engines are made. The number of revolutions shown by the revolution-counters

is read off and noted by the observer at this point. The determination, of the times required

to cover the measured mile is made in the usual way by three time-Observers working

in-dependently.

Afier a warning has been given by the contact-man. torsion-meter, via the contact-man

budge, that the ship is approaching the measured mile, the readings of the torsion-meter

are begun. These readings are continued until the Signal has been given by the

contact-man that the measured mile has been passed. During the courses over the measured mile,

the wind-observer has read- off the wind-direction and Speed at regular intervals of30 seconds. The observer at the recording-table, after having received a signal from the contact-man steering-eompartment that the measufea mile is being approached, sets the paper

strip in action, and brings the pens which record the revolutions of both propeller-shafts,

the revolutions of the Chernikeeff-log and the times, on to the paper and subsequently sets

the master-clock going. He stops the observations on a sign from the contact-man steering-compartment.

The contact-man s plot (>-tab]e receives the signal that the measured mile is being

approached from the contact-man bridge.; this is the siga for the commehcement of

observa-tions at the ((plot -tab1e,which sign is passed on by the man at the tab1e to the corresponding

observer, just as is the sign ((Measured mile passed . Between the two signals the observers

plot -table determine the course followed and the time in which this has taken place..

C. STANDARD MANOEUVRING-TESTS

-The standard manoeuvring-test consists of a zig-zag course which is obtained as

follows : on .a certain course the rudder is put over a° to port. As soon as the 'deviation

amounts to bo to port In relation to the original course, the rudder is immediately reversed

to a° to starboard. ' When the deviation amounts to b°-to,starboard in relation to the original course, 'the rudder is reversed again to a° to port, etc.

FOr the figures a and b see E. Result 0/ Measurennts. The course foliowed is givçn

BC Bridge A 8 Engine-room. a from 8.

'B'

to 7 1=Anemometer :2:= Plotlable :3. = Inclination-meter Chernikeeff- log 5. Maihak torsion-meter 6:= Revoluhon-counter movement 0 compass bearing rudder angle

Fig. 5 : Course during standard manceuvring-tests.

The aim of these is to determine the following data as functions of time during the

zig-zag courses

Speed of ship

Course of ship with regard to original course Path of ship's centre of gravity

Number of revolutions of propeller-shafts Rudder-angle

Rudder-head torque

Angle of inclination of ship Torque of propeller-shafts

Speed and direction of wind

For schematic arrangement of the necessary measuring-apparatus _{see fig.} 6.

7 Recorder-table

8.=Master-clock

Advedko- manometer

io: Ribbon -compass

11= Signalling-key rudde A = Observer S = Liason person C Writer 0 = Helmsman

Fig. 6 Schematic arrangement of measuring-apparatus on board HNMS Marnix

-. B .6. to.?. Steering-engine-room = .11. A . A BC Plot room

ad. 1. The speed of the ship is determined by means of the Chernikeeff-log, which

has been calibrated beforehand during the speed-trials. A time-relay has been set up in

the steering-compartment on the same table on which therevolutions of the log are recorded.

ad. 2. At the back of the steering-compartment, where a ribbon-compass has been set up, there is also a signalling-key. At each 50 change of course, an observer makes contact

with this signalling-key. This is also recorded on the recording-table. The ribbon-compass

is a repeater-compass of the master gyro-compass on the bridge, and has the advantage over

a compass with a normal compass-card that the graduation are far larger.

ad. 3. The pa\th of the ship's centre of gravity is determined by means of the ((plot >>.

ad. 4. The number of revolutions of the propeller-shafts is recorded by means of

revOlution-counters mounted on the shafts (see fig. 7).

These revolution-counters make one contact per revolution, which is also recorded

on the recording-table in the steering-compartment.

ad. 5. The rudder-angle is directly deduced from the rudder-head by means of a

system of levers and is then noted on the recording-table, which for this purpose is placed in front of and near to the rudder-head (see fig. 8).

Fig. 7: Revolutionscounter mounted on the shaft. Fig 8 : Recording-table with system of levers for

re-cording the rudder-angle

46

/7

ad. 6. The rudder-head torque is, determined by means of two self-recording

Avedjio-manometers, which are mounted on the pipe-lines of the steering-engine cylinder. (One

for each cylinder). The pressures are recorded on a round disc, to be found on every

pressure-gauge. Along the outside of the two discs a time-relay is to be found, directed by a

master-clock which also works the tithe-relay on the reco1ding_tale (see fig. 8, top left).

ad 7. _{An inclination-meter has been set up in the engine-room. The angle of}

inclination is recorded on a drum. A time-relay, also directed by the above-mentioned master-clock, is mounted on the edge of the drum (see' fig. 9).

ad. 8. As has already been noted, during the zig-ag course the torque of only one

shaft can be determined. This is done with the aid of the Maihak-torsionmeter, (see fig. 10).

This cannot be recorded, so that the reading-off times must be determined by means of a stop-watch that must be staPLed simultaneously with the master-clock in the steering-compartment.

ad. 9. The speed and direction of the wind must also be read off immediately before he beginning of the zig-zag course.

During the turns (1)5 E, F, and D', E F' in fig. 5) 'not more than 10° rudder is given,

in order to avoid loss of speed. As soon as the deviation from the original course amounts

to bo, the rudder must immediately be put over Therefore during the zig-zag tests the ship

was steered not from the bridge but from the steering position aft (see fig 6) in order to avoid

loss of time due to transmission This is also the reason why, during the zig-zag course,

a. contact-officer in the steering-compartment gives cormartds to the man' at the helm.

Imnediately' before the ship deviated from its original 'course, the coffimand was given':

a° port or starboard At the moment that the ship had the required deviation from the

original course, the command c Now)) was given, and the man at the helm put over the

rudder as rapidly as jossible tO the required position. The steering-ehgine of H. N.. M. S.

MarnixD teacts very rapidly. -

-On passing the points and A' (fig. 5), situated at about a mile ahead Of the measured mile, and 'on condition' that the ship is on the right course, the cOntact-man on the bridge is warned; hereupon the' latter passes on the message to the various observation-posts that

the observations can be begin and that the various instruments can be set going. As soon

as he hears that this has been done, he gives a long warning-signal on the alarm-siren, followed 2 seconds later by a shott.operation-signal. At this moment the master-clock in the steering-compartment is set going, as well as the stop-watches for the torsion-meter and the

((plot-table. Five seconds after the short operation-signal on the alarm-siren, the contact-man

on the bridge reports t the contact-officer in the steeriiigs-compartrnent that the. rudder

must be put over a° to port (port was always taken first) and the deviation must amount to b°.' ,The subsequent progress of the zig-zag course i's 'under the command of the

contact-officer, in the steering-compartment. The ship must then make following deviations : port.

starboard - port starboard

-C- port.

As soon as the ship has put abdut 10° to port for the last time, the measurements are stopped and the officer on the bridge takes over command again.

For the sake of simplicity the original course must amount to a whole number of

degrees. Moreover each- zig-zag course is carried out twice. and in opposite directions.

The. directions for the' .egine-room mentioned under B.. Speed-Tests apply also here. Two time-observers are 'required for the zig-zag tests : one for the

Maihak-torsion-meter. and. one for the ((plot -tàble, for these are the only two .Qbservatons whichare not

the àiarmsiren, the stop-Wãthes of the tinie-obsèrver-torsionrrieter'

id

thtim-obsetêr-((plot ((-table are set going The time-observer at the ((plot ))-tablei,ves a sign every 5 seconds tO the observer at the )(.plot.))±-tahle, whereupon the. latter :Inaiks a point on the

curve representing the course followed These observations are cQntinued until notice

s received from the contact-man bridge that the measurements have been finished The

stop-watch used by the time-observer-torsion-meter is a so called doub1e stop-watch

Each time that the observer-torsionmeter completes an observation, he at oace presses in

the stop=watch : one hand stands still, the other continues to turn. The number of seconds

shown by the suspended hand is read off by the time observer and noted by the writer The stop-watch is pressed in again and the suspended hand springs into position by the

other hand etc These proceedings are likewise continued until notice is received from the

contact-man-torsionmeter via the contact-man bridge that the observation is fiPished.

Between the points A B and A'B' (see fig. 5) the wind-direction and speed

are noted by the wind-observer He receives a sign for this purpose from the contact-man

bridge.

After the officer in the steering-compartment has reported, via the

contact-man bridge, that point A or A' has beeh passed, the observer by the recording-table sets

the paper stnp in action and places all the pens on the paper Immediately after this the

observers concerned set the recording manometers going. As soon' as this. has been done

the fact is announced to the contact-man bridge via the contact-man steering-compartment Shortly afterwards a long warning-signal is given, follo'ed by a short operation-signal

At this moment the observer at the recording-table sets the master-clock going Shortly

afterwards followsthe command ((a° port-)) per te]ephone. tO the contact-Officer in the

steering-compartment.. The latter then passers on this command. The observer at the

ribbon-compass gives a Jong pressure on the signalling-key once for every 5° change of course

When the-ship crosses the original course again, the signalling-key is given one short pressure

These cOntacts are noted on the recording-table. These' operations cont,jnue until the

command Observations eneds is given.

The observer of the inclination-meter receiVes the commands a-Adjust instruments's

and- s..Observatiorts_.ended.-.. from. the.contact-rnan engine-room.

D. TURNiNG-CIRCLE TESTS

During the turning-circle tests the. same observations are made and in the same manner as those descnbed undei C Standard Manoeuvring Tests, excepting that the observer

at the ribbon-compass now makes .a contact with the signalling-key once every 10°.

'The turning-circle test is carried out by giving a° port or ,starboard on a specified

course. The course is given in. fig. 11.

48 1 MILE -A BB A' 'I... I. S. B. OR' PORT 2X

Group A Group B 15° 25° 35° 250 Speed in kilots 5° 5° Rudder angle

Speed Tests

Four runs over the measured mile at each speed..

12 15 18 21 24. 27

Standard Mannu-vring-Tests

Each run was carried out twice, Once in eaCh direction

Speed 17.5 knots Ship's course deviation in rel. to origil course 10° 20° 30° 45° 10° 20° 30° 45° Speed = 22 kiiots 10° 20° 30° 45° 10° Date 1911-1951 1941-1951 19-11-1951 20-114951 20-114951 20-114951 r Date 22-11-1951 22-11-1951 21414951 2i-111951 .21-11-1951 21114951 21-11-1951 21414951 21-114951 27-11-1951 27-114951 27-11-1951. 27-11-1951 27-114951 2211-1951 22-111951 22-11-1951 22-11-1951 22414951 22-11-1951 27-114951 49 80° 45° 10° 200 30° 45° 10° 20°

50 Group B

(Ofltr) Rudder angle

5° 150 25° 350 Speed = 26 knots Ship's course deviation in rel. to original course 100 20° 30° 45° 200 30° 450

Turning-Circle Tests

Each turning-circle was carried, out twice,

once to port and once to starboard

Group C Speed = 17.5 knots

Speed 5= 22 knots Speed 26 knots Date 22-1 1-1951 22-114951 23414951 23-11-1951 231 1-1951 23-11-1951 2341-1951 23-11-1951 23-11-1951 2341495 28-11-1951 23-11-1951 28-114951 150 26-114951 25° 2641-1951 350 _:26-11-1951 15° 2611-1951 25° 26-114951 350 2641-1951 100 200 100 200 300 450

Rudder angle Date

Rudder angle Date

Rudder angle Date

Fig. 13 PnrI -. S S -Speed l7.5hn. -30 Rndd.r angle is Cnmpann beanings.20n 20 I0.

.1,

General course _angle

90e 4 'rudder 0 -/ :::: 10-I __. cylinderS 2.4Q0. 7_ -< S.H.Pp0

/...-'

--I9OE Pert Pl 30' .l40 '10_ E 20

--/'\

"\ / \ .-. rudder angle 10 / _/

\ 7

/

\z'

S /compans-200 I / bearing 0 ". '. -- cross-/ ". 1 '., monemenl 0 E / '/'-..

\

/sogie , 200 20

-\

/

"--'

\_./

heel SB. I ' 0 30 60 90 120 150 180 210 240 270

Bane nI lime in Sec.

Porl ' ' S S -' Speed l7.kn. 5 35, . Rudder angle 15e Corepann b.aring20e 20-55,5'.,

I"

General cnurne angle

270n rudder '°' I \:' ---'\ 1! '5/'5., 5

0'

-"-. -!J' ! ! ::: In 5 10' I I cylinderl .s20 ,,"' 30-cS.6 2300 S5S...,,_/S/" "._..js11'1_portshart 2l00, .180 E 0 _S__5' Npnr .160 Port .140 30 .io.. 20 ('5"-/55, /

\.,-"

/ ..-" rudder angle ..

:-/

\'

-' /

)"

,' -'" / -ompasi' b earing c :. -0 S / I -CtOSI 0 0 's. 1 1 -moaemeol 0 9 10 ' \ S/S / '/. -'-200 20 \

/S

-/

/

"angle el heel S 0 30 -60 90 120 150 120 210 240 270

Bane of lime In sic,

Fig. 15 Fig. 14 Purl

40-:_0.

"V.20 -1

Speed Redder angle _{'CO rnPa}

-180 ISO -10 b.aring.20° I Z°kn. 36 udder angle 10 40 Porl 40- 30- 20 I L / -

-'/'

presine n '.. I steering h' cylinders -perlshall ruoO2r 005!! 7"-\/ \ .., ," /

\/

\. \ I! / ' " -0 30 60 90 120

Bane of lime in see.

150 140 210 240 270 Port -Speed .l75kn 40-Redder angle .25° Compass bearing. 20° ': "

-\

--10 I Cylinders 20-i1'\\J I -14

2AOOPerlshal F

2.200 -B

':N.._____._,,.__- "----::: -160 Pen .140 ,, ::. ,-' .1 udder angle

L X

V I ' \.-'-' ' Cross-mooenrentO V -0 -0 0

I(

-". '-mpass-' l0-\ \ "./ j \ bearlg 52009 20-\, -/ N -'

\

/ '-angle oi E " / .1 heel -10 30-

'-''

6.8.40 0 30 60 90 120 ISO ISO 210 240

Fig. 17

Fig. 16

Part

Speed Redder angle

=35° Campans bearing.30° -40 -' 30 : to /

::' :

I " .'cyl d ro (

/

'< ' to I ! \ \ 3O h f / I! ?udder angle .leoo 170 :: Port 50 40 /

/\

\ /

\

S's

:

::

/

/ / \\ adder a gte ° /

ii

\. cms; : 5. / ""..._....roSS-'I0 I 's. / ./ /movement o 200 E

!20.

' 1S=.. ! / 'angl:oF '.3°. .5

/

I 40 \

/

I

/

,l5 S5 50 \_.' \ 5960 0 30 60 90 120 150 180 210 240 270 300 330 Base at time In 0cc. Port0 . Speed =22 hn. Rudderangle =25° 30 I Compass bearIogn 10° 1 'rudder angle =20 -10 0 r./I 1 ./"-j' = \ ( pressare in IS Slearleg . cylinder, n.20 I \'All 30

5200.'

4800 220 4400' H.PporlshaIl Pan 52

:il;.\i//J

5;;. o1

10 \...J

\

Y... I J'oemenio .200 20 J\

/

/ "angle at '.1 heel 0 30 60 90 120 150 160

Fig. 19 Fig. 18 Port 40-Speed .22 Rudder anglo =350 30 Compass beartng 10° f--20

':'°-/ v.1,_S -l ( ::30 0n911 rdder 50-II Ishall 4000 t4pur-, .170 Port -:' I -bearIng -5 6 to I ,--\ ' -200. 4 . cross-o 0 0 E movement® \ _i / '. \ : \ s.. o ' ;I 0 = 20 I 30 -. angie 01 <. hflI .,. -IS 40. -s0_ -0 3b -60 -90 120 ISO tOO 210 Base ottime-tnsec. Port so -Speed .28 ho. Rudder angle .150 Compass bear.ing=30°

I- 11

-F -.---.5_P " -_. .0 20 .1 .1 rudder angle

:0

30 -I--m 40 I - SB. 1I.500 10.000-. -280 F bri 260 -240.c Por.F

40-/ \

/ \ -/ _/ \ \ --10 II"

\

: e05lo 200= :10

\,

'J

/

,bear 9 200 E zo / ... ,j

\

/'angueut -.-400 / . / heel - -io- 30-I / -/ -S.., . -. -/ -15 5-, 40 sB. 0 3b 80 90 l0 ido ida 210 240 270 300

Fig. 21

Fig. 20

Pori

50 40

Speed Ruddee Coel065s

26 ho. aole .35° bed rIng2O° :1 rudder angle 0 ,ressure n o / \ I " steering 10 . -' "sI cylinders Iii 11.000 -23: 10.500 0 10.00. S.HPDorthali 5500 280 260° Port 220 40 15 udder angle C 30

I\

\"

10 20

\

/ \X 10 / . I -200

-I

cross-0 --0 E mooemenr. .to . -200. I . i--compass_ 5 B -\ f bearIng 0 20 I o-4000 30 \ I ' / ';. 10 ' I / ' 'angie Of 840 heel 15 0 30 60 90 120

Base of time In Sec.

150 ISO 210 Port Speed =26hn 40 . Rudder angle =25° Cornpor bcarInq 20° E 30 "I ' an5lo ru0d '-'30 - 40 :: ':'10,500 9500\ 271) 9 20- 17

\/

rudder coesPas-f /

lo.j/

L_bea 9 / 0 10

..ilk____k

0 = -0 -200 I I ' / f moeementG . 20-/ angle of C E / 30-1 '--heel 40. -15: 0 SB. 0 30 60 80 120 150 100 210

\& 72o -\7. ). jctt1Uc

k.

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?

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-speed Ruddnr anIe Dianeer Furning_circin

1?.5kn 13.3° sb 7OO m Vs Nr 10n 270° 360° 900 1800 -270° Nub. 360°

/

0 do o --:--io iso iho -.-20 2O 250 300

Base of lime in sec.

3O 3O 30 4o 450 480 510 - 540 5;0 -, K L) a LLl

K'

-te. '7-- 16 : is 14-

160-'S.

as- 1.5-

1.0-N

Speed Rudder 0091, 2*0° lb., DIumeer rnn_cbcl, d?5m N pori N Lb iB00 270° ₉₀ 380° 0 0 6O 90 120. 150 190 210 240 270 300 330 360 390 420 basi of lime in iic -

-Fig. 23 Fig 24

3;7.a\

c

c

120-I J - I -Speed Rudder angle DePir -109_circle 17.5 in 33,7° Lb. 407 m Vi

140-\

-Nrt . -180 270 -- -360 90° . 180 -270 --360 0 / 30 . 6O / 90 120 ISO 180 210 240 270

Bee of tithe in Sec.

300 330 360 390 420

L/R

HU ₌ 1 Fig. 25 Fig. 26 Yc

=

a2,

c,oic

ã1cZ1

2. 220-210 leo-E - 2.0-1 59116 Rudderanqli QIameljr tupnT..CircI. 22kn =13.81s.b. - 755 m N 9019 - Nsb -90 180 270 360 -180 270 360 ol 0 60 80 120 150 180 210 240 - 270

Base of lime In sec.

300 330 360 390 420 450 480 - - -- Speod =22 kn 24- Rudde on5le =222° 23 Lpjdn1 turnln3-cI 53m vs 220- -25- 0 _{o o} -=0 =0 0-5 =, 0 0 30 60 90 120 150 180 210 240 272 320 330 360

-t

₂₃

K

-Fig. 27 Fig. 28

)2,

d,oRcc

-speed - - - - 22 k 22O

it

2.5- 1800 2700 350 900 f$50 _270° 3600 1,5-I 0 30 60 90 120 150 180 210 240 270 300 330 360 390

Base of time IS Sec

I::

25-t

230-B 2.0-° 1.5 11.0 05 - - Speed Redder asgte Diameter torning_cecIe 132°.b. = 1083 26kn m -900 1:0° 2700 ---360° --90° -1800 270° 360° -0 I 0 30 r 60 50 120I 150I 190I I 210 I I, 240 270 300

Base of time in Sec. I

330 360I 390 420 452 482I I

510

I

The following tests have been carried out :.

In figs. 12,to 21 the results of a considerable amount of standard manoeuvring-tests

are, given and in figs. 22 to 28 those of the turning-circle tests.

The results of the standard manoeuvring-tests are given for one sathng-threction because the curves calculated froi the observations of the other sailing-direction are almost

identical (ci. fig. 12 with fig 13). Hence we can draw the conclusion that the measurements are reliable This reliability is chiefly due to the fact that almost all the observations were carried out so as to be self-recording, whilst the two observations executed with the aid of stop-watches ( plot ))-apparatus and torsion-meter) were carried out with such care and

precision that possible inaccuracies in time were reduced to a minimum Working out

the observations thus obtaired requires howe\ er a large amount of calculation and drawing A study of the results of the standard manoeuvring-tests brings the following facts

to l,ight

at a rudder-angle of 5° it appears that when giving starboard tudder the pressure in

the port steering-cylinder increases and vice, versa, at 25° and 35° rudder-angle when giving

starboard rudder the pressure in the starboard steering-cylinder increases and vice versa,

whifr at 15° rudder-angle no definite, tendency is present. -At 5° rudder-angle the pressure-

-point thus lies in front of the rudder-head, at 25° and 35° rudder-angle behind it, and at

15°rudder-angle the pressure-point is to be found very, close to the rudder-head. The

loga-rithm of the Reynolds number, 'ith regard to the length of the rudder, amounts to roughly

7.5 for the three speeds at which the zig-zag tests were carried out. At an angle of incidence

of 0° a rudder can roughly be compared to a flat plate, so that it is interesting to plot the above-mentioned value in the diagram in which' the resistance coefficients of flat plates are

given as. functions of 'the Reynolds number. This diagram is given in fig. 29. The equation

applying to curve 1 has been drawn up by Prandtl, those applying to curve 2and curve 3 are

known as the friction-formulae of Prandtl-Schhchting, and the one applying to curve 4 has

been deduced by Blasius. .._ .

Cirves 1 and 2 represent the connection between the frictional coéfficients and

the Reynolds number in a turbulent flow, curve 4 in a laminar flow and cürvè 3 in a turbulent

'flow with a laminar entrance.,(') From fig. 29 it appears therefore that the ship's rudder is

situated just above the critical area. If we choose a model-length of 10 rn (which is on

the very large side) when carrying out the rests on the ((Marnix , so that the

model-scale is roughly 10, then the Reynolds number for the model rudder is roughly 106. _This

implies that we are in the transitional field. In the case of sections, also of rudders, not

only the resistance but also the lift will be influenced by this field Here is thus a possible

so4rce of scale-effect for the manoeuvring-tests on ship-models to be -held later.

Concerning thjs ((possible source of scale-effect, we can say that, since we can assume

with rather gre'at certainty that the rudder, at the ship as well. as' at the model, works in the turbulent boundary layer of. one of either object, there cannot be spoken of a transitional

field 'at the model rudder. Indeed the velocity gradient in the boUndary layer of the ship

and the model will be different, so that this fact indeed will be a source of scale-effect However, apart from these. possible sources of scale-effect, there is the fact, that the forces working upon the rudder are highly influenced by internal frictional forces, at least suffici-,ently to expecca1e-effect, since, with the model tests, only the Froude's law of comparison

(i) This figure is 'discussed at length in cc Resistance, Propulsion and Steering of 'Ships)) p. '4O.etc.

60

is taken irLto account. With the marioeuvriñg-tests to be he1d later, thotoi4gh attention has to be paid to these facts.

From. diagrams 12 to 21 it appearsthat in nearly all cases the rudder has been put

over from port to starboard and vice versa at the right moment Putting over the rudder

from 35 port to 35° starboard takes roughly 10 to 12 seconds, which may be considered

8.1O 7 5 4 3 110' 0 5 - .-IoR 6 7 8 8

Fig. 29 : Resistance coefficients of smooth planes as a function of Reynolds' number.

fairly fast. After the rudder has been put over from one side to the other, the ip remains

only for a moment in its former course-deviation The time between putting over the rudder nd the moment at which the ship has reached its maximum course-deviation is 3 to 10

seconds The Marnix is thus a vessel which deviates rapidly from its course when the

rudder is put over, which fact is of great importance for a warship.

The curve representing the athwartships displacement of the centre of gravity of the ship lags behind, the cur-ye representing the course-deviation.

'When port rudder is given the rudder-surface fal]s within the screw-race of the port screw and as a result the number of revolutions of this screw diminished, and vice versa

This can be seen clearly in all the diagrams, especially in the case of larger rudder-angles. No adequate elanation cap he given of the Mlo'Wing points: the course-deviation to starboard is greater fhat td port; the time during which port rudder is given is greater than the time given to starboarth The only explanation we can offer for this is that the ship i slightly concave to starboarth

0.074. R 0.455. LO 0.455. tog 1.327 R'0'5 R250 R25° - 170CR' o WIetsbr, Gebers KOmpi 2 r' 3

4 -

--1__

-.

-;'

The following remrk can be mad conceirning the results of the turñiPg-cirle tests; with an increasing rudder-angle, the diameter of the turning-circle becomes smaller(and with increasing speed the diameter of the turning-circle becomes greater, both phenomena are

obvious It is noteworthy that the speed diminishes considerably after putting the rudder over, for instance from 17 5 knots to about 13 knots and from 22 knots to about 18 knots, the greater the rudder-angle the greater the loss of speed and at the same time the greater

the loss of revolutions Both the revolutions to port and those to starboard decrease With port rudder the revolutions of the port-shaft decrease more than those of the

starboard-shaft We saw the same tendency during the zig-7ag tests

Fig. 30 : Relation between diameter of the turniñg-cicle rudder-angie and initial speed of the ship

In fig. 30 the diameter of the turning-circle has been plotted on a base of rudder-angle

with the initial speed of the ship as parameter From this figure we can see that at a speed

of 22 knots the diameter of the turning-circle, when starboard rudder is given, is smaller

than that with port rudder This can also be explained by a concavity of the ship to

star-board.

F. - FINAL REMARKS

In this treatise we have dealt with the rnanoeuvring-tests on board the destroyer

H N M S

Marnix> Thanks to the co-operation of the Royal Netherlands Navy, we

were able to carry out these tests on a very extensive scale, so that we now have at our 62 800 7 0 0 soo 500. 400 -b kn Yr17.5K

N \

_N'

" N

-Port

-- Stdrboard ib° 150 200 250 3'QO 350 RUDDRANGL

disposal a wealth of facts which will be of great value for subsequent model-research. Owing to the fact that we had time at our disposal in which to set up instruments and lay on the

necessary telephone connections, it was possible to record most of the observations. And

those for which this was not the case could be carried out with the utmost possible accuracy. This explains the satisfactory nature of the results.

The measurements taken on the Marnix will also be taken on a model p1 this ship..

These comparative measurements will also be executed on a Victory-ship, a medium-sized

cargo-ship and their corresponding models. With the aid of these data we shall endeavour

to determine the influence of scale-effect as it appears in manoeuvring-tests with ship-models.

Contribution by Dr. ALLAN

I think 'the author and the organization concerned are 'to be congratulated on this work, which is very ambitious 'and extremely valuable.

One point I would ask' the author,' it is-not clear to me whether he measured the actual

path of the ship or only the angular mouvements. '

The ship chosen is a war vessel and it may be questioned if, this type of work is really

necessary on merchant ships It is a common view in Great Britain that so long as a

mer-chant ship can be kept on a straight course and steered within reason, extreme

mancuvra-bility is not of major importance. I would he interested to hear the author's view oii that

point.

In the lease of smaller specialised tugs and harbour boats the- question is rather

different In the tank at Teddington we carry out tests for vessels of that type, without

measuring the actual forces on the rudder or on the hull. , The mode] is free to be manccuvred,

putting the rudder over and controlling the propellers by a remote control system! ' The

interest is chiefly in the controllability, and we have found from very rough checks that

the results are repeated on the ships in a broad sense It is a useful method for demonstration

I suggest it is an extremely difficult thing to satisfy' all conditions given on page two of the paper and it must be difficult to repeat the model test to reproduce the full scale

test in a accurate manner On the model you have practically infinite power in respect

of propulsion and on board ship you have a limited torque machine, I suggest it would pro-bably be necassary to control the revolution performance on the model and not just leave

it connected up to 'the dynamometer in the usual way. in other words I have in mind

some kind of super-impOsd control of the revolution to represent what happens on the ship.

You also spoke of measuring the speed with a Chernikeef log This is a very

satis-factory instrument 'vhen it is calibrated, but in my experience it is sensitive to yaw

(Cher-nikeef and Pitotlog too). When the ship is swinging the indicated speed is in error. Some

tests conducted on H M Ships on the measured mile in forced rolling conditions indicated

a' seriouS error in speed. The angle of yaw is probably 'lower here, but the point may be

of importance. '

-Another point which occurs to me is the scale effect on the ,rudder forces.' If the

model tests are carried out on a normal model of the 1 /20th to 1 /24th size, there will be large

scale effects on the rudder forces, especially when the rudder angles are approaching and

- exceeding 'the stalled condition. ' ' '

-It is important to attempt such experiments and there is, no doubt we will learn a

great' deal from the results. ,

Contribution by Prof. AERTSSEN

T,his research on scale effect in manuvring tests on ship' models is very useful.

I remember 20 yaers ago when a Kort nozzle' was to be fitted on a Harbour tug. Mr,

Char-dome will fully agree with me we were very uneasy about what would be the manuvring qualities after fitting that nozzle, and while I think of the difficulties at that time, I am convinced that the exact knowledge of scale effect will aid in the direction of sohTing those

difficulties.

-The -authors are to be congratulated for their interesting paper.

Contribution by Prof. E.V. TELFER

I have, some experience in legal naval-architecture and .have been mixed as an expert in some collision cases, and the judge expects that a captain should know his ship and so

the diameter of the turning circle If the captain confesses, as many had to do, of no

know-ledge of the turning characteristics, the judge ar ounce regards the captain as an ignorant

person, who did not his duty to his ship owners. The chances that he will gain his cause

are more and more remote.

-I suggest 'it is essential to produce. a'- technique in this matter.

Another point is how to put this data over, a trick can be used, that is the use of

a steering polar. It cOnsists in pJotting to a base the rudder torque and the ship's turning

moment as an ordinate. The comparison of polars will be extremely useful for different

rudders and different ships.

I endorse what Dr. Allan said; could we have more than One model, and study from the model size, before taking the jump to the ship.

RespOnce by Dr Jr J. BALHAN

The actual path, of the ship was measured by means of the ((plot)) - apparatus and with the aid of the Chernikeefflog and gyro - compass indications.

I agree with Dr Allan that for a cargOship the most important thing is to keep the

ship on a straight course. 'So in the case of warships, tugs and harbourbOats, we are interested

in the' turning characteristics and in the case of merchantships we are interested in the

steering (course keeping) characteristics But from all the hydrodynamics problems of

the ship, that of turning and steering is one of which it has not yet become possible to

predict their characteristics with certainty in'the preliminary design stage. If we are thin

king of- -the calculation of a propeller with some rnoderà vortex théorie, if we are thinking of the calculation of the resistance of a ship, the frictional resistance with the aid of the ex-periments and in the last years the wave resistance pure mathematical, if we are thinking of the calculation of the stability of a ship in smooth water, if we are thinking of the desing of a ship with a Froude's number smaller than one, then we must confess that it will take several years before the steering problem will come in a position as the above mentioned

Indeed it i's very usefull to try to approximate the turning and steering problem purely

theo-retical as done by Davidson and others. But the problem is to Complicated, that in my

opinion the predictions of, the turning and steering characteristics with certainty in the preliminary design stage, can only be done in, routine testing of the model ,of the ship that will be built.

But before we can carry out responsible model tests, 'at first we must find a good cor-relation between model and full scale tests for turning as well as for steering.

- As Messrs. Brard en Bleuzen have shown in one of their papers, we will find differences,' which are very difficult, if at all possible, to explain.

We did not flatter ourselves with the hope that no difficulties were to overcome, but we find that we must approximate the problem in this way.

With the object to predict turning and steering characteristics in the preliminary

design stage in view, this research on scale effect in manuvring-tests was started. This

Marnix itself, as well as in the comparison of the full scale and modeltests- and that we have tried to do the full scale tests as accurate and extensive as possible, since we cannot repeat the full scale tests every time again.

The yaw of the ship has been smaller than 100 and tests in the Wageningen tank have indicated that the Chernikeefflog is not sensitive for this variation in angle of incidence

The tests in Norway were done in smooth water, so the ship was not rolling.

About the scale effect of rudders, I have already mentioned it in the paper As

cavitation form the propeller on the rudder can be a source of scale effect, I propose to do the followIng test in the cavitation tunnel, to determine the influence of this cavitation.

Put a rudder in the cavitation tunnel and measure the torque in the rudder axis at several speeds of the water, several angles of incidence and of course several cavitation numbers

with and without a propeller before the rudder Then I believe it is possible to determine

the influence of the cavitation on the rudder upon the ruddermoment. But 1 believe too,

that this influence at normal merchantshipspropellers will be very small But of course

at warshipspropellers the influencce can be considerable

I thank Prof. Telfer for his remarks and we will give attention to them. I thank Prof Aertssen for his congratulations

Delft, 23rd of July 1953.