721

1 INTRODUCTION

Berthing of a ship is a critical phase of a journey that

could lead to damages of own vessel as well as other

structures [1, p. 2]. A navigator may experience

avderse effects of wind while manoeuvring in harbors

or restricted waterways [2]. This article will address

this force in regards of power consumption,

considering that external forces have implications for

energy usage.

A detailed description of berthing operations will

follow in the next section. It will also address some of

the factors that affect ship handling and how to

compensate for them. Section three will present the

method used in this field study and important

information about the ship and port. Section four

presents the results of the study while section five

discuss the results based on relevant literature. The

last sections will present a conclusion and further

research on the topic.

2 BACKGROUND

Ship handling is explained as close-quarter work were

the navigator has to use forces under his control,

direct or indirect, to cater for elements that are not

under control [3, ch 1, p.1]. Elements under control

would be propulsion or loading condition, while

external factors such as current, wind or visibility are

not under control [1, pp. 10-13]. A ship will be safely

handled if elements are taken advantage of instead of

disregarding them.

A ship handler needs to know how his ship

responds to these factors and especially in port

environments where there are several risks involved.

2.1 Golden rules of berthing

To safely berth a ship there are some universal

guidelines that must be followed. One important rule

Wind Affecting Berthing Operations

E.M. Kløvning

Norwegian Univ

ersity of Science and Technology, Trondheim, Norway

ABSTRACT: Almost every voyage culminates in a manoeuvre to berth the ship safely along a quay or wharf.

During this phase a ship is affected by a number of factors, one of them being wind. This paper seeks to

understand how wind affect a ship in regards of power consumption during berthing. A field study was

conducted on a car passenger ferry, where every approach in one harbour was logged and analysed over a

period of four months. The goal was to provide greater knowledge about energy usage and the study presents

several interesting findings. It is estimated that power consumption is stable when the median wind speed is

less than 4 m/s. Stronger winds have a significant effect on power consumption, e.g 17 m/s gives an 106,31%

increase from calm conditions. Furthermore there is not discovered any correlation between consumption and

wind direction in this study.

http://www.transnav.eu

the

International Journal

on Marine Navigation

and Safety of Sea Tran

sportation

Volume 14

Number 3

September 2020

DOI:

10.12716/1001.14.03.26

722

is to have a controlled approach at slow speed [1, p.

4]. Slow speed is critically important when under keel

clearance is low or when using a bow thruster.

Depending on the hull design, a bow thruster will be

ineffective between 2 and 5 knots [1, p. 12], [3, ch 1, p.

12]. At the same time, current and wind will have a

greater effect on manoeuvrability at slow speed.

2.2 Berthing in wind

Wind is essentially air in motion that occurs due to

pressure and temperature differences [3],[4]. The air is

drawn from high pressure areas to low pressure areas

to equalize the difference. Wind speed, also called

velocity, increases with the pressure joint gradient.

Near ground level, there are several factors that

determine wind direction, such as terrain, topography

and structures. Wind speed can also vary, creating

gust winds that are remarkably dangerous [3, ch 3

p.94].

Strong winds could cause leeway and heading

changes [1, p. 14]. Naturally the effect will vary

depending on wind speed, direction and windage

area of the ship [2]. Usually the ship will be most

vulnerable when presenting its broadside, which has

the largest windage area. The size of this area will

also vary with loading condition [5, p. 41]. During

strong winds a navigator must plan the manoeuvre

according to the wind to minimise the potential

danger and maximise the assistance.

The force of the wind can be understood as a point

of influence on the above-water structure of a ship [1,

p. 14]. This point will move depending on the ships

heading and speed. The ship will usually settle in a

position where the point of influence of the wind

aligns with the pivot point. The pivot point is a

theoretical point that indicates where the ship rotates

along its length [1, p. 10], and the transverse ship

speed equals 0.

If the ship has forward speed the pivot point (P) is

forward [5, p. 36], [3, ch 1, p.11] and the point of

influence of wind (W) will be astern. The result of this

will be a force that turns the bow towards the wind.

Note that this example uses a ship with large windage

area aft.

Figure 1. Alignment of W and P [1, p. 15]

The navigator must use available propulsion

sufficiently to compensate for this resultant force.

Wind force can be estimated using the following

formulae [1, p. 16]:

( )

18000

Wind speed windagearea

Wind force

The ship in this field study has a windage area of

approximately 1000m² on both sides, and 250m² in the

front and stern.

Example:

4 1000

0,88

18000

= =

8 1000

3,55

18000

= =

8 250

0,88

18000

= =

This example shows two important points. First, it

shows that a doubling of wind speed gives

approximately four times the force acting on the ship.

Secondly, the force is vastly reduced when the

direction switches from broadside to stern or front. If

possible, the manoeuvre should therefor expose the

smallest windage area to reduce the effect of strong

winds [1, pp. 17-18].

In any situation, the navigator must use enough

power on the thrusters to compensate for the force

acting upon the ship.

3 FIELD STUDY

The goal of this study was to examine how wind

affected the ships power consumption during

berthing operations. The purpose is to present

information that can be used in optimalization of

operations, in regards of energy usage. To achieve

this, the author logged every approach in one port, for

four months.

3.1 The ferry

Every approach was made by MF Korsfjord, which is

a ro-ro passenger ferry that runs on liquid natural gas

(LNG). The ferry is a monohull, aft-bow symmetrical

vessel as seen on figure 2. Korsfjord has 2 Schottel

STP 1010, N=1000kW azimuth thrusters, one in each

end [6]. Both have fixed pitch propellers and in

general, thrust vectoring devices give enhanced

manoeuvrability because the thrust is vectored [1, p.

10; 3, p. 50]. This design allows fully actuated

berthing where surge, sway and yaw is controllable.

Unfortunately the ship has a large windage area on

both sides and a high B/D ratio. This indicates that the

ship has a great potential for leeway in strong winds

[1, p. 10].

Power is generated from two MITSUBISHI GS16R-

MPTK (900 kw) gas engines and a MITSUBISHI S12R-

MPTA (1000 kw) in standby. These engines provide

the thrusters with power and consumption is logged

using an energy monitoring system [7]. Consumption

is directly affected by RPM on the thrusters. An

increase in RPM gives an increase in consumption.

723

Figure 2. Starbord profile of M/F Korsfjord (courtesy of

Fjord1)

Table 1. Main dimensions of M/F Korsfjord [6]

_______________________________________________

Length 122,75m

Beam 16,7 m

Draught 3,5 m

Height 20,5m

Maximum speed 17,5 knop

Gross registertonnage 2971

_______________________________________________

3.2 The berth

The port of Molde is an area with varying degrees of

traffic. The quay is equipped with fenders. There is no

noticable current in the area but sometimes there can

be strong southern winds.

In the eastern end of the quay there is an

automated loading ramp for veichles. This ramp will

automatically position itself during berthing

operations. When the ships is in the right position the

ramp will lower itself to a shelf underneath the

trapdoor in the bow. This ramp will keep the bow

secured during loading and unloading, while the aft

thruster pushes the stern towards the quay.

Table 2. Main dimensions of berth

_______________________________________________

Length 85 m

Minimal depth 4,7 m

True course 065°

Weight 85 t

_______________________________________________

Figure 3. Satelite photo of M/F Korsfjord before loading in

Molde [8].

3.3 Data collection

This article is written as a result of a quantitative field

study. Data was collected between 07.10.19 and

31.01.20 on board MF Korsfjord that navigates

between Molde and Vestnes in coastal Norway. The

ships own equipment was used to log every bit of

information. The ship is equipped with an Høglund

IAS [7] that shows transit time, speed, course, position

and usage of KW for each journey. Wind is measured

by an external unit on the bridge roof [9],

approximately 20 metres above sea level.

Figure 4. Port of Molde [10].

Figure 5. Wheelhouse of M/F Korsfjord.

Berthing the ferry is split into different phases, as

shown in figure 4. During transit the ship sails at

around 11,5 knots towards Molde with both thruster

at around 220 RPM. Step 1 is a point at 0,9 nautical

miles from the quay where the course is adjusted to

approximately 070⁰. Here the forward thruster RPM is

reduced to 0. Aft thruster RPM is reduced to 160

RPM. The ship still sails on autopilot. At step 2 an

audio message plays on the bridge to inform the

navigator to commence manoeuvre procedure for

arrival. Here the ship is 0,4 nautical miles from the

quay. The ships speed is logged, then the navigator

turns off the autopilot and steers the ships towards

the quay. When the manoeuver is finished, the

navigator logs wind, consumption, notices and time

in the table at step 3. Every approach had to be

performed in 8 minutes or less, to be valid for this

study. Consumption and time spent manoeuvring is

logged between step 2 and 3. The track was created in

ECDIS and followed on each approach. Wind speed

and direction is logged visually as median wind over

a period of 30 seconds after arrival.

The ship is equipped with a surveillance system

[11] that give audio warnings when the speed limit i

broken. To complete a successful berthing the

navigator must keep a speed lower than what is

shown on table 3 at all times.

The figure above shows the wheelhouse of the

ferry used in this study. Wind is registered using the

display in the ceiling. On the right side is a display of

724

ECDIS-chart, used for marking the points in points in

figure 5.

Table 3. Speed limit during berthing.

_______________________________________________

Distance to pier Maximum speed over ground

_______________________________________________

277,8 nm 7

245,5 m 6

122,75 m 5

61,375 m 3

_______________________________________________

4 RESULTS

There were conducted 140 approaches in Molde port,

during this trial. Of those 140, 15 approaches were not

included in the analysis because the speed limit was

exceeded or the approach lasted for more than 8

minutes, resulting in corruption of data. The study

gave the following results based on n=125

approaches.

4.1 The Effect of Wind speed

First off is a comparison of average time spent

manouevring and average consumption needed for

approaches in different wind conditions. Note that

table 4 only presents wind speed, regardless of

direction. The table also depicts the change in

percentage for each variable, using 0 m/s as a starting

point. Time spent on the approach shows a slight

increase in time, even though the goal was to use the

same amount of time on each approach.

During the trial there were a lot of approaches in

calm weather, while only a few approaches were

made during strong winds. No wind speed were

registered on 13 m/s or 16 m/s, and therefore the

values were removed from table 4. The average

consumption seems to be quite stable between 0 m/s

and 4 m/s. At 5 m/s and beyond the consumption

gradually increases with stronger winds, if we

disregard the result from 6 m/s. Figure 6 shows a

graphic representation of table 4.

Table 4. Overview of results from field study.

_______________________________________________

Wind Average % Average %

speed time consumption

(m/s) (seconds) (kw)

_______________________________________________

0 (n=4) 360 1 23,75 1

1 (n=29) 369,55 2,65 25,20 6,10

2 (n=30) 368,16 2,26 25,16 5,93

3 (n=15) 371,13 3,09 25,26 6,35

4 (n=17) 365,29 1,46 24,95 5,05

5 (n=3) 361,33 0,36 28,33 19,28

6 (n=1) 364 1,11 24 1,05

7 (n=4) 374,75 4,09 27,75 16,84

8 (n=6) 383 6,38 30,16 26,98

9 (n=1) 387 7,5 31 30,52

10 (n=1) 357 -0,83 30 26,31

11 (n=2) 381 5,83 32,5 36,84

12 (n=2) 382,5 6,25 37,5 57,89

14 (n=3) 373,66 3,79 39 64,21

15 (n=6) 395,66 9,90 42,5 78,94

17 (n=1) 382 6,11 49 106,31

_______________________________________________

Figure 6. Illustration of results from table 4.

4.2 Consumption and wind direction

Figure 7 shows a graph for consumption in relation to

wind direction. During this trial there were no wind

above 4 m/s, registered from north or east. The result

shows that consumption gradually increases, but

there are few to no differences in consumption when

divided by direction. Unfortunately the result is

dominated by western winds, which makes it difficult

to accurately measure differences in consumption.

Figure 7. Wind speed compared to consumption for

different directions.

5 DISCUSSION

There are several interesting findings that were

revealed during this study. As mentioned above,

wind affect the ferry by causing leeway or heading

changes. It is therefore necessary to counter this force

using the ships propulsion system. However, an

increased usage of RPM on thrusters leads to

increased power consumption.

The results from table 4 indicates that wind effect

is absent in winds with speed of 4 m/s or less. In these

conditions there is no need for increased RPM, above

minimum steering RPM, to counter the force of wind

during berthing. As a result, the average consumption

lies between 23,75 kw and 25,26 kw, which is a

relatively marginal difference.

Figure 6 shows a trend that indicates an increased

consumption when wind speed is 5 m/s or greater.

Increase in consumption could be explained as an

effect of more force acting upon the ships windage

725

area. A necessary increase in RPM would therefore

cause a higher consumption during berthing.

On the other hand, the increase in consumption is

not that high considering the vast increase in wind

force. As mentioned earlier, doubling the wind speed

gives four times the force acting upon the ship [1]. It

would be logical that consumption rose proportional

with wind force. However, this is not the case.

Consumption seems to follow an almost linear

growth. For example, doubling the wind speed from

7m/s to 14m/s only gives an increase in consumption

of approximately 40,54%.

This phenomenon could be explained by the

guidelines for berthing provided in section 2.2. It

stated that ship handler should plan a manouvre to

maximise the assistance. In calm conditions the

propulsion system need a minimum amount of power

to steer the ship or maintain speed. This amount of

power is measured to be around 25 kw in this study.

When the wind force increases, the consumption also

increases but on a much smaller scale. The reason for

this could be that the wind force is used as assistance

when berthing. For example southern winds push the

ship towards the loading ramp, meaning that the

navigator has to use propulsion to maintain the

heading and slowly reduce speed. On the other hand,

no power is required to maintain speed during the

manouvre or push the ship forward. These

advantages propably reduce the overall power

consumption.

Figure 7 shows consumption categorized by wind

direction and wind speed. One of the goals of this

study was to examine possible differences in

consumption based on wind direction. Unfortunately

there were no winds above 4 m/s registered from

north or east during this trial. Strong winds were also

mainly registered from the south. This makes it hard

to compare differences in consumption by wind

direction. More data is needed to properly examine

this factor. Although there were insufficient data

gathered, it is possible to see a marginal difference in

consumption between southern and western winds.

Even though there are some differences, the study

has a great limitation in regards of measuring the

effect of wind direction. During berthing the ferry

changes course several times. This could reduce the

impact of wind direction. It would therefor be

reasonable to pinpoint that wind direction propably

have an effect on consumption but it did not appear

in this study.

It is possible to calculate the effect of wind in great

detail, using the results from this study. However,

there are several weaknesses to this method that

drastically reduces the validity of data. As mentioned

in chapter 2, the ships is affected by a number of

factors during berthing. In this trial these effects have

been neglected, simply because there were no

equipment available to accurately measure them. It is

highly likely that current, trim or waves have an

impact on consumption as well as wind.

The result is also based on trials conducted

manually by a human. To fully recreate an approach,

even in the same conditions, is not always possible.

The data gathered during this trial shows several

approaches in similar conditions where power

consumption and time spent manouevring varies. The

numbers presented in this study must therefore be

seen as estimates or trends.

6 CONCLUSION

Wind has been described as a factor affecting ships

during berthing operations. In this field study, the

effect of wind is not present at 4 m/s or lower in

regards of power consumption. Stronger winds

require more power on the propulsion machinery but

the increase is not proportional. Finally, no correlation

between consumption and wind direction were

discoveres during this field study.

7 FURTHER RESEARCH

It could be interesting to measure the effect of wind

during transit or recreating the same trial with

equipment to measure more variables such as trim,

draught and wave height. This research could be

relevant for optimalization of operations.

BIBLIOGRAPHY

[1] The Standard P&I Club, A Master’s Guide To: Berthing,

2nd ed. London: Charles Taylor & Co. Limited, 2012

[2] M. Szymoński, “Some Effects of Wind on Ship’s

Manoeuvrability,” TransNav, vol. 13, no. 3, pp 623-626,

September 2019. [Online]. Available

http://dx.doi.org/10.12716/1001.13.03.19 [Accessed Jan.

18, 2020].

[3] N. Kjerstad, Fremføring av Skip med

Navigasjonskontroll: For maritime studier, 3rd ed. Oslo:

Akademika forlag, 2013

[4] A. D. Sivle, “Vind,” snl.no, Des. 5, 2019. [Online].

Available: https://snl.no/vind. [Accessed: Jan. 12, 2020].

[5] D. J. House, Ship Handling: Theory and practice, Oxford:

Elsevier Ltd, 2007

[6] Skipsrevyen, ”M/F Korsfjord,” skipsrevyen.no. [Online].

Avaiable https://www.skipsrevyen.no/batomtaler/m-f-

korsfjord/. [Accessed: Feb. 18, 2020].

[7] Høglund, “Ship Performance Monitor,” hma.no.

[Online]. Accessed https://hma.no/solutions/marine-

automation/ship-performance-monitor-spm. [Accessed

Feb. 10, 2020].

[8] Google earth, “Satelite photo,” earth.google.com.

[Online]. Available

https://earth.google.com/web/@62.73673942,7.1680687,-

0.19837953a,185.5934564d,35y,0h,0t,0r. [Accessed: Feb.

12, 2020].

[9] Furuno, “RD-33,” furuno.no. [Online]. Available

https://www.furuno.no/nb-

NO/Produkter/remote_display/rd_33.aspx. [Accessed:

Apr. 28, 2020].

[10] Gule Sider. “Sjøkart,” gulesider.no. [Online]. Available

https://kart.gulesider.no/?c=62.725517,7.152271&z=13&l=

nautical&q=%22molde%22;geo. [Accessed: Mar. 12,

2020].

[11] Grieg Connect, “Shiplog traffic,” griegconnect.com.

[Online]. Available

https://griegconnect.com/blog/core/shiplog-traffic/.

[Accessed: Feb. 25, 2020].