International Journal

on Marine Navigation

and Safety of Sea Transportation

Volume 4

Number 2

June 2010

157

1 INTRODUCTION

It is well known that a controllable pitch propeller

(CPP) can provide smooth speed control. On the

other hand, in case of ships with single CPP and sin-

gle rudder, the difficulties of coasting manoeuvre

and stopping manoeuvre are reported (Takeda 1992,

Yabuki 2006).

During coasting manoeuvre of CPP ships with

propeller pitch feathered to zero, the rudder force re-

duces significantly and CPP ships are difficult to

control their head turning motion by steering espe-

cially under windy condition. Furthermore, during

the stopping manoeuvre of CPP ships, an additional

unstable yaw moment is often exerted, which intro-

duces a significant reduction in manoeuvrability,

and, under this condition, it is difficult to control

their head turning motion by steering.

In order to improve the manoeuvrability of CPP

ships at coasting, the authors propose the use of the

Minimum Ahead Pitch (MHP) of CPP. The MHP is

the smallest blade angle of CPP for ahead propulsion

which ensures adequate steerage. The authors con-

ducted full-scale experiments using a 5,884 G.T.

single-CPP, single-rudder training ship to confirm

the effectiveness of the MHP operation in coasting.

Figure 1 shows the general arrangement and prin-

cipal particulars of the test ship.

A simulation study using the MMG type mathe-

matical model was performed in order to investigate

the in-harbour ship-handling method to control the

unstable stopping motion of CPP ships. The test ship

was the same CPP ship as stated above. Based on the

results of the simulation study, the authors propose

an effective ship-handling method that applies a

turning moment to the ship by the maximum rudder

angle steering prior to the reversing operation of the

CPP.

Figure 1. Principal particulars of the test ship

On the Control of CPP Ships by Steering

During In-Harbour Ship-Handling

H. Yabuki

Tokyo University of Marine Science and Technology, Tokyo, Japan

Y. Yoshimura

Hokkaido University, Hakodate, Hokkaido, Japan

ABSTRACT: This paper describes the results of experimental and simulation studies that aimed at developing

effective control methods for single-CPP single-rudder ships during the coasting manoeuvre and the stopping

manoeuvre. In order to improve the manoeuvrability of CPP ships under coasting, the authors performed full-

scale experiments and confirmed that CPP ships under coasting using the Minimum Ahead Pitch (MHP) of

CPP are controllable by steering. A simulation study was also conducted to evaluate the ship-handling method

during the stopping manoeuvre that applies a turning moment to the ship by the maximum rudder angle steer-

ing prior to the reversing operation of the CPP and it is confirmed that CPP ships can be controlled sufficient-

ly by the proposed method.

Principal Particulars

Hull

Length: Lpp (m) 105.00

Breadth: B (MLD, m

17.90

Depth: D (MLD, m) 10.80

Cb 0.5186

draft: d (m) 5.96

Propeller (CPP)

Prop. Brade No. 4

Prop. Dia.: Dp (m) 4.70

P.R. (Brade Angle) 1.050 (25.5°)

Rudder (Flap Rudder)

Ar (㎡)

10.034

Ar/Ld 1/63.4

Aspect Ratio 1.865

158

2 CHARACTERISTICS OF TURNING MOTION

OF CPP SHIPS DURING STOPPING

MANOEUVRE AND COASTING

2.1 Turning motion during stopping manoeuvre

The test ship is equipped with a CPP and can also

reverse the main engine directly. This system makes

it possible to perform a comparative experiment us-

ing the same hull and engine under the same condi-

tion to investigate the difference of a turning motion

during the stopping manoeuvre between CPP and

FPP (Fixed Pitch Propeller) ships.

Full-scale stopping tests were performed under

almost the same condition in deep water in both CPP

and FPP operation modes. As light breeze was ob-

served during the experiment, the initial course was

set into the wind for all stopping tests. In Figure 2,

the final head turning angle

()Ψ

when the ship is

stopped is plotted against the initial advancing con-

stant

( /( ))

J U nP= ⋅

both in the CPP mode and

in the FPP mode. In the figure, the results of the

stopping manoeuvre in which the propeller was re-

versed and the maximum rudder angle was applied

simultaneously are plotted in addition to those with

the rudder amidships.

Figure 2. Comparison of the head turning angle between FPP

and CPP

In the FPP mode, the test ship exhibits the typical

stopping motion of a right turning single propeller

ship, i.e. she turns her head to the starboard steadily

and the direction of her turning motion can be suffi-

ciently controlled by steering. On the other hand, the

turning motion in the CPP mode proved to be less

stable than that in the FPP mode and the effect of

steering to control the direction of turning motion

was not observed. The direction of turning motion in

the CPP mode seems to be fixed mainly by the rela-

tive wind direction at the initial stage of propeller

reversing.

From the above-mentioned results, it is assumed

that the direction of turning motion of CPP ships is

fixed by the head turning moment at the initial stage

of propeller reversing.

2.2 Turning motion during the coasting manoeuvre

The authors performed course keeping tests using

the same CPP ship as mentioned above in order to

compare the effects of steering control under the

coasting manoeuvre between the propeller pitch zero

operation and the MHP operation. The time history

of heading, rudder angle, CPP blade angle and ship

speed are plotted in Figure 3.

In the coasting manoeuvre under the propeller

pitch zero operation, the test ship turns her head into

the wind even though the wind was very weak (1

m/s) and her head turning motion can not be con-

trolled by steering with the maximum rudder angle.

Since the obtained results agree with the results of

other experiments (INOUE 1992) qualitatively, the-

se characteristics seem to be common among ships

with a single CPP and a single rudder.

Figure 3. Comparison of the course keeping ability between

pitch zero operation and MHP operation

ＦＰＰ

-80

-40

120

-1.6 -1.2 -0.8 -0.4

Jso

Ψ(deg.)

Wind ; Starb'd Bow

Wind ; Port Bow

Helm ; +35

Helm ; -35

C ＰＰ

-80

-40

120

-1.6 -1.2 -0.8 -0.4

Jso

Ψ(deg.)

Wind ; Starb'd Bow

Wind ; Port Bow

Helm ; +35

Helm ; -35

-6

-4

-2

U(knots)

, Ψ

CPP (deg.)

-40

-30

-10

δ (deg.)

CPP

Wind 1 m/s

Stop Eng.

Pitch Zero

90 sec

-6

-4

-2

-40

-30

-20

-10

CPP

MHP

90 sec

Wind 5-6 m/s

159

This manoeuvring difficulty may be due to the

pitch distribution of blades at propeller pitch zero

operation. Though the pitch around the boss is main-

tained to the advance side, the pitch around the tip is

changed to the reverse side at propeller pitch zero

operation and the unstable flow which reduces the

rudder force is generated around the stern.

On the other hand, in the case of the coasting ma-

noeuvre with the MHP, the test ship can keep her

original course under strong wind conditions (6 m/s)

by applying the appropriate helm. This experimental

result seems to prove the effectiveness of the MHP

operation under the coasting manoeuvre and that

CPP ships under coasting using the MHP can keep

and control their heading by steering.

3 CONTROL OF TURNING MOTION OF CPP

SHIPS DURING STOPPING MANOEUVRE

3.1 Stopping motion prediction of CPP ships

The stopping motion of CPP ships is predicted using

the MMG type mathematical model. The mathemat-

ical model can be described by the following equa-

tions of motion using the coordinate system in Fig-

ure 4.

(1)

The hydrodynamic forces can be expressed by the

following equations.

(2)

where,

= mass of ship;

= moment of inertia of

ship in yaw motion;

= axial velocity, lateral

velocity, rate of turn respectively.

The terms

and

represent the hydrodynamic

forces and moment. The subscripts H, P ,

and W

refer to the hull, propeller, rudder and wind force re-

spectively.

The detailed expression of hydrodynamic forces

and moment on the hull, propeller, rudder and wind

are available in the references (Yabuki 2006, Yabuki

2007).

The hydrodynamic derivatives and coefficients

for simulation were measured by the captive model

tests such as CMT, oblique towing tests, and rudder

tests using 1/24.48 (Lpp = 4.29m) model. The hull

force and moment coefficients are measured by

CMT and oblique towing tests. As for the forces and

moment induced by propeller reversing, the thrust

coefficients were estimated using the 4 quadrant

POT result on the reversing blade angle and thrust

data on MAU charts. The thrust deduction coeffi-

cient was obtained by the model test. The lateral

force and moment were obtained from the captive

model tests on the reversing blade angles. Rudder

force and moment coefficients are measured by rud-

der tests and the interactive coefficients between hull

and rudder are obtained from the gradients of these

coefficients. The wind force and moment coeffi-

cients were derived from a wind tunnel test using the

1.5 m length model. The hydrodynamic derivatives

and coefficients for simulation are available in the

references (Yabuki 2006, Yabuki 2007 ).

Figure 4. Coordinate system

Figure 5. Comparison of the stopping motion between meas-

ured and simulated

mu mvr X

mv mur Y

Ir N

−=



HP W

XX X X X

YY Y Y Y

NN N N N

= ++

160

The accuracy of the mathematical model of the

test ship was confirmed by comparing the simulation

results with those of full-scale experiments as shown

in Figure 5. In the stopping test, turning moment is

applied to the test ship by maximum rudder angle

steering prior to making slow astern operation while

proceeding at 4 knots. Although the time history of

ship speed indicates some discrepancy between sim-

ulation and actual measurement, the predicted

changes of heading and trajectory are in good

agreement with the measured results. Thus, it seems

reasonable to consider that the proposed simulation

model represents the stopping motion accurately.

3.2 Steering control of CPP ships during stopping

manoeuvre

As described in section 2.1, the direction of turning

motion of CPP ships during the stopping manoeuvre

seems to be determined by the yaw moment at the

initial stage of propeller reversing. Therefore, the au-

thors propose the stopping manoeuvre to control the

head turning motion of CPP ships that applies turn-

ing moment by the maximum rudder angle steering

prior to propeller reversing and performed the simu-

lation test to confirm the effectiveness of proposed

method.

Figure 6 shows the simulation results of the stop-

ping manoeuvre where the propeller is put slow

astern while proceeding at 3 knots under 10 m/s left

wind. In the stopping manoeuvre with the rudder

amidships, the test ship drifts leeward and turns her

head into the wind. On the other hand, in the stop-

ping manoeuvre that applies the maximum rudder

angle steering to leeward prior to propeller revers-

ing, although the test ship drifts leeward, the yaw

moment can be reduced sufficiently and her original

heading is well maintained.

4 APPLICATION OF PROPOSED METHODS

TO IN-HARBOUR SHIP-HANDLIN

4.1 Anchoring under windy condition

The series of ship-handling for anchoring consists of

four simple manoeuvring elements, i.e. approaching,

stopping, laying out anchor and fetching up. When

approaching, it is necessary to proceed on the

planned track and reduce the speed by the coasting

manoeuvre. The proposed MHP operation is appli-

cable for the coasting manoeuvre while approaching

the anchorage especially under windy condition.

When stopping for laying out anchor, it is essential

to control the ships heading into the resultant of all

external forces such as wind and current. The pro-

posed steering control method can be applied to the

manoeuvre to stop the ship while keeping her head-

ing into the wind.

Figure 6. Example of controlling yaw moment by applying lee

helm prior to reversing. (Left wind, 10 m/s)

Figure 7. Effective CPP ship handling for anchoring in windy

condition (Full scale trial)

The authors applied the above two control meth-

ods to the actual anchoring of the test ship under the

7.5 m/s beam wind condition and the results are

161

shown in Figure 7. During the approach ship-

handling, the test ship first reduced her CPP blade

angle from dead slow ahead to the MHP while pro-

ceeding at 4 knots for speed reduction and proceed-

ed on the planned track by applying lee helm proper-

ly to control the head turning moment to windward.

Next, when the headway was reduced to 3 knots, the

test ship used hard-starboard steering to apply the

maximum yaw moment to windward. After the yaw

moment increased sufficiently, the test ship changed

the blade angle to slow astern directly, skipping the

propeller pitch zero operation. Finally, the test ship

stopped with her heading into the wind and the chain

was laid out adequately to leeward. The above re-

sults of the full-scale experiment indicate that the

proposed methods can be effectively applied to an-

choring under external forces.

4.2 Crash stop astern manoeuvre in a harbour area

The proposed steering control method during the

stopping manoeuvre is applicable to the crash astern

manoeuvre to avoid collision with other ships. In

this case, it is necessary to stop the ship with the

shortest distance by the propeller reverse operation

and turn her head to the starboard as great as possi-

ble by the steering. To achieve this collision avoid-

ance manoeuvre, the authors recommend the ship-

handling method that puts the propeller to full astern

after applying the starboard head turning moment by

the maximum rudder angle steering and confirm the

effectiveness of this method by simulation.

Figure 8. Example of the crash astern manoeuvre that applies

maximum starboard rudder angle prior to the propeller revers-

ing (Calm condition)

The results of the crash astern manoeuvre, while

proceeding at 6 knots, that utilizes the maximum

rudder angle steering to starboard prior to the full

astern operation are shown in Figure 8. In the case of

the crash astern manoeuvre with the rudder amid-

ships, the test ship stopped turning her head slightly

to the right of the original track, and both the head

turning angle and the side reach are not enough to

avoid collision. On the other hand, when the maxi-

mum starboard rudder angle was applied prior to the

reverse operation, both sufficient starboard head

turning angle and side reach to avoid collision were

obtained. On this crash astern manoeuvre, although

the 15 second delay in the reverse operation is ob-

served compared to the manoeuvre with the rudder

amidships, the head reach shows the same figure

(2.5 L). This seems to be due to the additional re-

sistance which is exerted by the steering and the

oblique drift of the hull in the case of the manoeuvre

with the maximum rudder angle steering. Therefore,

it can be inferred that there is little effect of the re-

verse operation delay on the stopping distance in the

proposed crash astern manoeuvre.

Next the authors performed a simulation study to

confirm the effectiveness of the proposed crash

astern manoeuvre under windy condition. The simu-

lation was conducted with 10 m/s winds for various

wind directions and the obtained results are shown

in Figures 9-12.

In the case of the crash astern manoeuvre with the

rudder amidships, the test ship stops almost on the

original track with slight head turning, however the

head turning angle is not sufficient for collision

avoidance in the head-on situation. On the other

hand, the crash astern manoeuvre with the maximum

rudder angle steering, both sufficient side reach and

head turning angle for collision avoidance are ob-

served for each wind direction.

Figure 9. Crash astern manoeuvre with maximum starboard

rudder angle (Head wind, 10 m/s)

162

Figure 10. Crash astern manoeuvre with maximum starboard

rudder angle (Right wind, 10 m/s)

Figure 11. Crash astern manoeuvre with maximum starboard

rudder angle (Left wind, 10 m/s)

Figure 12. Crash astern manoeuvre with maximum starboard

rudder angle (Tail wind, 10 m/s)

This simulation study demonstrates that the pro-

posed crash astern manoeuvre is effective for colli-

sion avoidance under windy condition.

5 CONCLUSION

The authors performed full-scale experiments and a

simulation study in order to develop an effective

control method for CPP ships during the coasting

manoeuvre and stopping manoeuvre. Results ob-

tained in this study are summarized as follows.

1 CPP ships under coasting using the MHP are con-

trollable by steering, making it possible to keep

the planned course.

2 For ships with a single CPP and a single rudder,

the MHP operation improves the manoeuvrability

in coasting and in-harbour ship-handling.

3 The unstable head turning motion of CPP ships

during the stopping manoeuvre can be controlled

sufficiently by the ship-handling method that ap-

plies turning motion to the ship by the maximum

rudder angle steering prior to the reversing opera-

tion of the CPP.

4 This ship-handling method is applicable to the

ship-handling for anchoring under windy condi-

tion and the crash astern manoeuvre in a harbour

area.

5 Proposed steering control techniques are applica-

ble and effective for the in-harbour ship-handling

of CPP ships with forward accommodations such

as the test ship. It remains to be seen whether the-

se techniques are applicable for the ships with

different configurations

REFERENCES

Inoue, K. & et al. 1992. Unstable yawing motion of a ship

equipped CPP. Journal of Japan institute of navigation,

vol.87:163-170 (in Japanese)

Takeda S. et al. 1992. Coasting manoeuvre of single CPP

equipped ship. Journal of Japan institute of navigation,

vol.86, 243-250 (in Japanese)

Yabuki et al. 2006. Turning motion of a ship with single CPP

and single rudder during stopping manoeuvre under windy

condition. Proc. of international conference on marine sim-

ulation and ship manoeuvrability 2006:M6-1-8

Yabuki et al. 2005. A proposal of minimum ahead pitch

manoeuvring for single-CPP, single-rudder ships. Journal

of Japan institute of navigation, vol.112:331-337 (in Japa-

nese)

Yabuki et al. 2007. On the rudder control during stopping ma-

noeuvre for single-CPP, single-rudder ships. Journal of Ja-

pan institute of navigation, vol.116:153-160 (in Japanese)