The Impact of Container Ship Trim on Fuel Consumption and Navigation Safety

Abstract

Fuel consumption, fuel cost savings, environmental pollution, and navigation safety are significant factors for shipping companies. Maritime transport represents 3% of total greenhouse gas emissions globally. Trim optimization is one of the ways to save energy and reduce ship emissions. Thus, this study aimed to evaluate how the optimization of the trim of container ships at different speeds can decrease exhaust gas emissions and fuel consumption while considering the safety of navigation. This research was conducted by calculating the fuel consumption in real conditions and calculating the optimal trim for different speeds and gases of a container ship of 11,400 TEU. All obtained results were statistically processed to analyze fuel consumption at various speeds, considering the ship’s trim. It turns out that savings should never be at the expense of navigation safety, especially in limited maneuvering areas, such as canals. When maneuvering in such places it is necessary to adjust the trim to ensure navigation safety, i.e., to improve the rudder and propulsion device response, instead of reducing fuel consumption

1. Introduction

Maritime transport is one of the key indicators of the European Union (EU) economy [1] and one of the most energy-efficient modes of transportation, but it is also a significant and escalating source of greenhouse gas emissions. Given the above, the requirements for ship energy saving and emissions reduction are becoming more rigorous in the EU and worldwide.

According to the International Maritime Organization (IMO), it is forecasted that the potential carbon dioxide (CO₂) emissions from international shipping could grow as much as 50% to 250% by 2050 [2]. The Fourth International Maritime Organization (IMO) Greenhouse Gas (GHG) Study demonstrated that it will be difficult to achieve the IMO’s 2050 GHG reduction ambition only through energy-saving technologies and ship speed reduction. Therefore, it is significant to study measures to reduce the amount and intensity of carbon emissions [3]. The International Maritime Organization (IMO) committed to new targets for reducing GHG emissions in July 2023 and devised and implemented a set of measures in 2025 to fulfill these goals [1].

Technical and operational optimizations are the two methods for improving energy efficiency and reducing pollution caused by ships, as proposed by the IMO’s ship energy efficiency management plan (SEEMP) [4]. Shipping companies are becoming increasingly interested in operational optimization methods, which include speed and trim optimizations [5]. Most ships are designed to carry a certain amount of cargo at a specified speed to reduce fuel consumption. The specification of set trim conditions is necessary for this [4].

In addition to rules related to saving ship energy and reducing emissions, shipping companies must comply with the IMO conventions, here listing three of which are particularly relevant to shipping; the International Convention for the Safety of Life at Sea (SOLAS) from 1974, the Convention on the International Regulations for Preventing Collisions at Sea (COLREG) from 1972 and the International Convention on Standards of Training, Certification and Watchkeeping for Seafarers (STCW) from 1978 [6].

Having identified the problem, this study aimed to determine the influence of ship trimming on fuel consumption and navigation safety, and their mutual influence. Trim significantly impacts a ship’s resistance through the water, whether empty or fully loaded, and optimizing it can result in significant fuel savings [4]. A properly trimmed ship provides several key advantages [7]:

• Stability: Improves the stability of the ship and reduces the risk of overturning or rolling due to sea conditions.
• Efficiency: It reduces the water resistance, which leads to less fuel consumption.
• Safety: Properly distributed cargo reduces the risk of shifting cargo during navigation, which can cause accidents.
• Maneuverability: It facilitates ship management, especially at lower speeds and in confined spaces such as ports.

As a result, the impact of trim on fuel consumption and navigational safety has become a major concern for scientists and shipping companies.

Lokukaluge et al. [8] examined the identification of optimal trim conditions with ship performance and navigation data and found that selecting appropriate trim conditions could improve log speed or reduce ship fuel consumption. One of the easiest and cheapest methods to optimize ship performance and reduce fuel consumption is trim optimization, which was investigated by the authors [9]. Undap and Follidah [10] discussed the impact of using optimal trim during the cruising phase, which can reduce resistance and fuel consumption, resulting in less emissions production by the ship. The authors Xie et al. [5] developed a speed and trim joint optimization method that utilizes sensor data and a fuel consumption prediction model to reduce fuel consumption. They demonstrated that joint optimization could overcome the limitations of single-factor optimization, such as trim and speed optimization, by considering multiple factors simultaneously. In this study, three tanker ships, three container ships, and two bulk carrier ships were utilized. In their research, the authors [11] developed a method to reduce fuel consumption by optimizing trim, while using a dynamic axle power estimation model based on available driving data. Gao et al. [12] studied the trim optimization problem with CFD numerical simulations of an oil tanker and concluded that the hull resistance as well as the fuel consumption of the tanker can be significantly reduced by trim optimization. Cepowski and Drozd [13] determined mathematical relationships between fuel consumption and operating parameters, such as turning speed, draft, trim, hull fouling time, wind speed, wave height, and seawater temperature. They also developed a hierarchical impact of operating parameters on fuel consumption. Yu et al. [14] developed a trim optimization method that aims to find the optimal initial trim to minimize fuel consumption during a voyage with a fixed main engine (ME) power.

Although there is increasing research on reducing marine fuel consumption, there is a significant gap in the current literature. Concerning the previously mentioned works, in this case study the authors connected three key elements that need to be considered when maneuvering a ship: saving fuel, reducing exhaust gas emissions, and navigational safety.

The authors have divided this case study into several parts. The introductory part of the paper defines the problem, subject and goal of the research, as well as the background of the research and the results of the literature review of existing studies. The second part of the paper, Materials and Methods, presents the technical characteristics of the ship and the mathematical formulas that were used during the research. In the third and fourth parts of the paper, the obtained results are presented and explained. The part with the case study is based on a comparative analysis of fuel consumption and environmental pollution reduction on the Rotterdam–Singapore route concerning ship trim. In the last part of the paper, conclusions are given.

2. Materials and Methods

This research was conducted through a combination of theoretical analysis and experimental research, i.e., case studies. We used different scientific methods. A compilation method was used to review previous research. A description method was used to describe the research problem. Data collection and statistical analysis were used to obtain data on fuel consumption. The process of choosing the best trim with less fuel consumption and less environmental pollution for a container ship with a capacity of 11,400 TEU was made during a navigation period of more than two years. The data were recorded and used for this research. The method of analysis and synthesis of data sets was also used to achieve trim optimization. Technical, ecological, and safety aspects were considered. This research has been carried out only in favorable weather conditions, while measurements were not considered in extreme weather conditions. Data about the ship are shown in

Table 1. The technical characteristics of the ship.

Specifications	Value
Main engine type	Diesel engine—HYUNDAI B&W
Main engine power Auxiliary engines	72,240 kW 4 × 4300 kW
Gross tonnage	131,332 GT
Draught	15.5 m
LOA (Length overall)	363.61 m
Breadth	45.66 m
Height	69.7 m
Displacement	171,371 t
TEU	11,388
Speed max.	−25 kn
Fuel type	HFO
Class	Bureau Veritas

.

In the part with the theoretical analysis, the importance of reducing fuel consumption on environmental pollution and the economic aspects of higher energy efficiency are briefly analyzed. The first part presents the collected data on consumption concerning the previous parameters. The data were analyzed and compared to enable a more efficient assessment and comparison of consumption emissions and fuel costs.

The second part of this research identified actual fuel savings and reduction of environmental pollution for a case study of the most common route during this research, from Rotterdam to Singapore. This research was conducted using various draught and ship speeds at a specific trim. The experimental process was carried out at 10 to 24 knots (kn) for draught 10 to 15 m (m), trimming from 2 m by the stern to −1 m by the ship’s bow.

The last part of this research refers to the impact of trim on navigation safety when navigating narrow canals or limited navigation areas. The 11,400 TEU ship had 4 auxiliary engines with the power of 4300 kW each. During the research, there were 2 auxiliary engines under constant use, but the consumption of auxiliary engines is not affected by the change in trim, as the trim affects only the load on the main engine. Auxiliary engines are in use as a power supply and their load during the tests was constant and so was consumption as well, around 15 t per day for both engines.

Before each test condition during this research, the following limitations have been set to ensure the safety of the ship and the maximal accuracy of the test:

Research has been carried out only during favorable weather conditions as follows:

-

Maximum accepted sea state on the Douglas scale up to condition 4;

-

Maximum accepted true wind on the Beaufort scale up to condition 5.

The stability criteria of the ship were checked before each loading condition to ensure compliance with the safety parameters of the ship and tests were carried out only if the following parameters had been fulfilled:

-

Metacentric height above 1 m;

-

Bending moments and shear forces less than 98;

-

Torsion moments less than 95%.

Operational criteria were established as follows:

-

Propeller immersion over 110%;

-

Minimum UKC 70 m.

Calculation of Parameters Relevant to the Research

Trim is the difference between aft draft (T_A) and forward draft (T_F). It is an indicator of the ship’s longitudinal stability [15]:

$$\mathrm{T}\mathrm{r}\mathrm{i}\mathrm{m}={\mathrm{T}}_{\mathrm{A}}-{\mathrm{T}}_{\mathrm{F}}$$

(1)

It is important to mention that if the trim value is positive (+), this means the ship is trimming by the stern, while if the value is negative (−), it means the ship is trimming by the bow.

The cost of the ship in navigation is directly proportional to the daily fuel consumption, the time spent in navigation, and the fuel price. During navigation, the ship usually consumes heavy fuel oil for the main engine and auxiliary engines. The fuel consumption is directly influenced by the measurements and dimensions of the ship (length, width, draft, trim, and displacement), the shape of the hull, the propulsion of the ship, the required engine power, or the required speed. The cost of heavy fuel oil (Ttg) can therefore be expressed as the equation below:

$$\mathrm{T}\mathrm{t}\mathrm{g}=ctg\sum qtg·sz·Dpi$$

(2)

where ctg is the price of heavy fuel oil, qtg is the specific daily fuel consumption per day, sz is the required engine power, and Dpi is the number of days of navigation according to [16].

If daily fuel consumption for an even keel trim is taken as a reference, knowing the daily consumption for each trim, it can be established there is a differential of tons consumed per day according to trim. The cost of the ship in navigation is directly affected by significant changes in fuel prices.

The amount of ship squatting cannot be accurately calculated because of the many factors that affect it, some of which are impossible to predict. Still, simplified equations are used that provide us with approximate information about the number of ship squats. One of these is the simplified Barrass equation [17]:

$$Sqat={\displaystyle \frac{C_b·S^{0.81}·V^{2.08}}{20}}$$

(3)

where C_b is the block coefficient, S is the blockage factor, and V is the ship’s speed [m/s] [18].

From Equation (3), two simpler ones arise, so Equation (4) shows the amount of ship’s squat for a shallow water area with no width limitation:

$$\mathrm{S}\mathrm{q}\mathrm{a}\mathrm{t}={\displaystyle \frac{{\mathrm{C}}_{\mathrm{b}}·{\mathrm{V}}^2}{100}}$$

(4)

Equation (5) shows the amount of ship squat for the area of narrow canals, i.e., in the area where the S is between 0.100 and 0.265:

$$\mathrm{S}\mathrm{q}\mathrm{a}\mathrm{t}={\displaystyle \frac{{\mathrm{C}}_{\mathrm{b}}·{\mathrm{V}}^2}{50}}$$

(5)

Ship squatting occurs for all types of ships. However, the strength of its influence is determined by various factors. A prerequisite for its formation is a limited depth and width of the waterway. When the ship is in shallow water, the most important factors on which the size of the ship’s squat will depend are the ship’s speed, the ship’s block coefficient, blockage factor, the ship’s trim, and the influence of other ships.

Ship speed is the most important factor affecting ship squatting. It is evident from the equation that reducing the speed by half will reduce the ship’s squat to a quarter of the previous amount. The block coefficient of the ship (C_b) is the ratio of the displacement volume of the ship and the volume of a rectangle whose sides are equal to the length, width, and draft of the ship.

The method of obtaining the size of the block coefficient is shown by Equation (6):

$${\mathrm{C}}_{\mathrm{b}}={\displaystyle \frac{\nabla }{\mathrm{L}·\mathrm{B}·\mathrm{T}}}$$

(6)

where ∇ is the displacement [t], L is the length [m], B is the ship width [m], and T is the draft [m].

From the equation of the ship’s squat, it is evident that its size directly affects its block coefficient. The block coefficient provides information about the shape of the underwater part of the ship, i.e., about the fullness of the ship’s form. Ships that need additional space for loading cargo have a fuller ship shape, because this allows them to store a large amount of cargo below the waterline, but at the same time, the maneuverability of the ship is reduced. The block coefficient for a container ship is 0.65 to 0.70 [19].

The blockage factor S is significant for canal navigation. It represents the ratio of the surface of the immersed part of the main rib to the cross-sectional area of the canal. There is no exact definition or measure according to which it is possible to determine which channel is narrow and which is not since its concept is subjective and correlates with the size of the ship.

The size of the blockage factor S is obtained by Equation (7):

$$\mathrm{S}={\displaystyle \frac{\mathrm{B}·\mathrm{T}}{\mathrm{b}·\mathrm{h}}}$$

(7)

where B is the ship width [m], T is the ship draft [m], b is the canal width [m], and h is the canal depth [m].

If the ship is not on an even keel, the influence of the ship’s squat will increase further on the side where the ship sank more. In the event of passing another ship in shallow water, rules similar to those for navigation in a canal of limited width apply. Due to the reduced space for water flow on the sides, the ship will sink further. It is possible to predict whether the ship will sink more with the bow or stern, knowing the size of the block coefficient of the ship. Namely, for ships whose block coefficient is over 0.7, the bow will additionally sink; when the block coefficient is 0.7, both the bow and stern will dive equally; and with a block coefficient of less than 0.7, the stern will additionally dive [20]. When navigating in shallow waters, the ship’s squat leads to additional submergence, which can cause grounding.

According to the above, the equation [21] for fuel consumption can be written as follows:

$$\mathrm{F}\mathrm{C}=\mathrm{S}\mathrm{F}\mathrm{O}\mathrm{C}(0.5·{\mathsf{\rho }}_W·S_W·C_T·V^2+R_S+R_{bank})·V/{\mathsf{\eta }}_H/{\mathsf{\eta }}_O/{\mathsf{\eta }}_R/{\mathsf{\eta }}_S$$

(8)

where SFOC is the specific fuel consumption [g/kWh], ρ_W is the density of water [kg/m³], S_W is the wetted surface area [m²], C_T is the total resistance coefficient, V is the ship speed [km/h], R_S is the resistance due to the squat in shallow water [kN], R_bank is the resistance due to the bank effect [kN], V is the ship speed, η_H is the hull efficiency, η_O is the propeller open water efficiency, η_R is the relative rotative efficiency, and η_S is the transmission efficiency including the combination of gearbox and shaft loss.

Ship squat affects fuel consumption as can be seen from Equation (8). This research wants to emphasize that the safety of navigation in confined waters is important, and that more attention should be paid to it. In the mentioned conditions, fuel consumption should be secondary to the safety of navigation. The previous research is mostly based on models in simulated conditions and on unconfirmed computer simulations. This research was carried out with the limitations mentioned above.

3. Results

The lowest fuel consumption was observed when trimming the ship by the bow (bow trim) according to the results of the research on total resistance acting on the ship. The trim of 1 m by the bow resulted in the lowest daily fuel consumption for a ship with a capacity of 11,400 TEU. Higher speeds resulted in the most significant deviations in daily fuel consumption between the bow and stern trim. A significant decrease in daily fuel consumption can be observed in Figure 1, Figure 2, Figure 3, Figure 4 and Figure 5 when using a trim of 1 m by the bow for a draft range of 11–15 m at various speeds.

At a speed of 24 knots for trim 2 m by the stern, the daily fuel consumption was 246.9 t, while for the 1 m bow trim, it was 224 t at a draft of 11 m. Significant saving of 22 t can be determined, i.e., about 10% less daily fuel consumption.

If we take as a reference the daily fuel consumption for an even keel trim, knowing the daily consumption for each trim, we can establish a differential of tons consumed per day according to trim.

The limitations of this research are manifested in the fact that the research was conducted during favorable weather conditions. Extreme situations were not considered because they can significantly affect the operation of the main engines and thus increase fuel consumption.

Figure 6, Figure 7, Figure 8, Figure 9, Figure 10, Figure 11, Figure 12, Figure 13, Figure 14 and Figure 15 present HFO daily consumption concerning the even keel’s situation for a given speed and correlating with trim, and the percentage of daily gain variation.

From Figure 7, it is visible that trim by the bow has the most optimal fuel consumption for all speeds at a draft of 11 m. The largest effect is visible at the highest speed, while at low speed, such trim is less effective but still with a better daily gain than the other trim options.

An increase in draft trim by the bow becomes ineffective in terms of “low-speed usage”. As displayed in Figure 9, for the trim of 12 m and speed of 12 kn, such trim is less effective than an even keel trim, but for higher speeds, trim by the bow is still showing the largest daily gain, especially for speeds between 18 kn and 21 kn.

At the 13 m draft, trim by the bow becomes ineffective for high speeds, especially above 21 kn, while showing the best daily gain at median speeds between 15 and 18 kn as shown in Figure 10.

The 14 m draft trim by the bow is ineffective in terms of extremely low and high speeds while still holding the best daily gain for median speeds of 15 to 18 kn as shown in Figure 13.

For a fully loaded ship with a draft of 15 m and above, an even keel trim is the best option with the most optimal daily gain while trim by the bow becomes completely ineffective at all speeds as shown in Figure 15.

4. Discussion

After the conducted tests and obtained results, it was concluded that trim by the bow has the largest application considering the given range of drafts and speeds as shown in Figure 16. Therefore, we can establish the following ranges of application for the trim by the bow with the highest effect on fuel consumption:

-

For any speed range at a draft of 11 m;

-

For a speed range of 14–24 kn at a draft of 12 m;

-

For a speed range 14–19 kn at drafts 13 and 14 m.

The research data presented show significant daily fuel savings achieved by bringing the ship to the desired trim. Up to 5% higher fuel efficiency has been achieved with trim optimization. Trim by the stern, or stern trim, is the current practice in the maritime industry because it enhances the safety of maneuvering and the stability of keeping a constant course.

The smallest differences in daily fuel consumption between the bow and stern trim were recorded at low speeds of 12 knots, however, the visible differences are of great significance considering the full container liner service. A reduction of voyage costs is one of the key factors imposed on ship owners in sustainable shipping policy.

4.1. Case Study—Comparative Analysis of Fuel Consumption and Environmental Pollution Reduction on the Rotterdam—Singapore Route Concerning Ship Trim

A case study for the Rotterdam–Singapore route was used as shown in Figure 8 to demonstrate real fuel savings. The data about the ship was already mentioned in Table 1, so it shall not be explained again. It should be emphasized that navigation through the Suez Canal was not considered on the planned route due to navigation safety reasons. Namely, when navigating the canals, it is necessary to consider that these are limited areas for maneuvering the ship, so the emphasis is placed on safety navigation.

The planned voyage from Rotterdam to Singapore is shown in Figure 17 with a blue line, which is 9233 nautical miles (nm), requires 21.3 days of navigation by a container ship at a speed of 15 kn, and the ship’s draft is 13 m. According to this research, there was a significant fuel saving of 66.1 tons (t) (Fuel saving 1516.6 t—1450.5 t = 66.1 t), Data from

Table 2. Case study Rotterdam–Singapore (without Suez Canal).

Variables	Value	HFO Consumption
Distance	9223 Nm	/
Time	21.3 days	/
Speed	15 kn	/
Draught	13 m	/
Trim 1 m by bow (optimal)	68.1 t/day	1450.5 t
Trim even keel	69.1 t/day	1471.8 t
Trim 1 m by stern	70 t/day	1491 t
Trim 2 m by stern	71.2 t/day	1516.6 t

. The fuel saving for this case was 4.55%. According to Table 2, navigating on a trim of 1 m by the bow can result in fuel savings of USD 43,956.5 for the planned voyage (Total fuel saving 66.1 t × 665 USD [22] = 43,956.5 USD, Data from Table 2).

Maritime transport plays an essential role in the global economy but is also a large and growing source of greenhouse gas emissions. Considering the latest strategy for the reduction of greenhouse gas emissions adopted by IMO in 2023 [24], maritime companies need to establish a model of trim optimization to reduce fuel consumption and therefore the emission of greenhouse gases into the air.

Exhaust Gas Emission

The exhaust gases released during navigation in this case study from Rotterdam to Singapore can be seen in

Table 3. Marine fuel (HFO) emission factors in kg/metric ton.

Pollutant	Emission Factor	Trim 1 m by Bow (Optimal)	Trim 2 m by Stern	% *
CO2	3114	4.58 × 106	4.72 × 106	3.05
CO	2545	3.69 × 106	3.85 × 106	4.33
NOX	77.26	1.12 × 105	1.17 × 105	4.46
SOX	47.73	69.23 × 103	72.38 × 103	4.55
PM	7.25	1.05 × 104	1.10 × 104	4.76

* The total reduction of exhaust gas in this case study is 3.05% CO₂, 4.33% CO, 4.46% NO_X, 4.55% SO_X, and 4.76% PM.

. This research suggests that an optimal trim of 1 m by the bow is recommended, and 2 m by the stern is the worst option.

Fuel consumption and emissions directly impact the percentage reduction of CO₂, carbon monoxide (CO), nitrogen oxides (NOx), sulfur oxides (SOx), and particulate matter (PM). Table 3 presents the emission of exhaust gases and their comparison after trim optimization. Emission factors used in Table 3 are taken from the Fourth Greenhouse Gas Study 2020 [3].

Optimizing a ship’s trim affects the ship’s resistance, which is directly correlated to the changes in the used engine power and fuel consumption to achieve the desired speed. Resistance changes under different trim conditions; therefore, the engine power changes as well, as is visible from

Table 4. Engine load (%) for different speeds and ship trim.

Speed/Trim	2 m	1 m	0 m	−1 m
12 kn	9%	9%	9%	9%
15 kn	20%	20%	19%	19%
18 kn	35%	34%	34%	32%
21 kn	52%	51%	50%	48%
24 kn	75%	72%	72%	71%

.

4.2. The Relationship between the Safety of Navigation and Trim of the Ship

Navigation through the Suez Canal was intentionally excluded and will be mentioned in this research section. Special attention is given to the safety of navigation and how the ship’s trim impacts that segment while maneuvering the ship.

It is common knowledge that the ship’s trim has an impact on its maneuverability. Proper balance makes it easier to maneuver a ship, while poorly balanced ones can make it difficult and increase the risk of accidents. Negative trim can make it difficult to maneuver the bow during a turn. In difficult weather conditions when waves, currents, and wind are strongly influencing the ship’s behavior, this is particularly important.

The limited depth and width of the waterway, which is the case with narrow canals, significantly affects the behavior of the ship and it differs greatly from the behavior of the ship in the open sea. Therefore, it is very important that the crew is aware of the specifics of the hydrodynamic forces that act on the ship when navigating the canal, and that they prepare in time and predict how the ship will behave. For this to be possible, it is important to be familiar with and understand the reasons for the occurrence of the important phenomena that mostly affect the maneuvering of a ship in a narrow canal and shallow waters, as previously explained in the second part of this research. Proper passage planning is crucial for safe navigation from point A to point B. This is a highly demanding and complex process that must be approved by the Master [25]. Poor passage planning can result in fatal consequences such as groundings, environmental pollution, human casualties, and other significant losses for the company. To comply with the guidelines of SOLAS Chapter 5 (regulations 27 and 34) [26] along with the STCW Convention [27] and the associated IMO guidelines resolution A.893(21) [28], a detailed passage plan must be prepared.

It is evident from the results (

Table 5. Container ship 11,400 TEU squat in different areas at different speeds.

	12 [kn]	15 [kn]	18 [kn]	21 [kn]	24 [kn]
Open sea	0.95 m	1.48 m	2.14 m	2.91 m	3.80 m
Narrow canal	1.90 m	2.97 m	4.28 m	5.82 m	7.60 m

, Figure 18) that in a narrow canal the speed has the greatest influence, and compared to the size of the ship’s squat in the open sea, a significant difference is noticeable in the increase of the ship’s squat in the narrow canal.

Large and fast container ships have a high fuel consumption, so even just a few percent fuel savings, achieved by optimizing the trim (0.5 to 3%) on an annual level bring about significant savings, which is also evident in this research.

The result of this trim optimization is that ships navigate with the larger trim by the bow, which limits the ship’s maneuverability. When navigating in a canal (restricted waters), an additional sinking occurs where the draft is greater when ships with a full displacement coefficient greater than 0.7 get an additional trim right at the bow. This means that if the ship navigates into the canal on an even keel, the forward draft will increase, bringing the ship to be trimmed by the bow, which always results in a decrease of maneuverability in confined waters.

During this research, no similar study was found to make a comparison and thus show the differences in the obtained research results. Although the data suggested confined waters navigation with a trim of 1 m by the bow, due to the demands of safety of navigation, the ship was slightly trimmed by the stern to increase maneuverability.

An example of the stranding of a container ship “Ever Given” occurred on 23 March 2021. It should be mentioned here since it caused a one-week blockade of the Suez Canal, disruption of maritime traffic, and the exchange of goods, and the ship continued its voyage 106 days after the ship owner had paid all costs. A ship must navigate through the canal at a safe speed to effectively stop any unwanted movement with short-term increased revolutions, with a greater deflection of the rudder, without the ship gaining too much acceleration. The ship’s dynamic instability was a result of its form and dimensional relationship, and it was likely caused by the trim by the bow to save fuel. For this reason, the permanent increase in revolutions to increase maneuverability was wrong, because as the speed increased, the ship’s maneuverability worsened, and the unwanted squat increased. Trimming and/or using a tug astern are the only options for improving poor maneuverability without exceeding safe speed. Safety is paramount over cost, so it is important to give this issue more attention so that ships navigate in canals with a larger trim by the stern for better maneuverability.

5. Conclusions

According to this research, ship trim plays a crucial role in enhancing container ship performance, enhancing navigation safety, reducing environmental pollution, and maintaining more efficient navigation.

Ships with trimming by the stern have better stability, improved maneuverability, and a reduced risk of accidents. Shipowners strive to reduce total costs because of their commercial and economic importance. The global economy benefits from economic efficiency, which reduces the cost of transporting goods, while container ships must comply with strict international safety and environmental protection standards, which include rules on harmful gas emissions.

The cost of fuel represents the largest part of the operating costs of the ship. Therefore, a properly trimmed ship can achieve significant savings, as shown in this research. However, this research also suggests that the cost of fuel and navigation safety should never be correlated.

Navigation safety should be a top priority, and ship Masters should not be placed in a situation where companies pressure for savings, which causes a decrease in navigation safety. In various situations, it has been demonstrated that savings, when accidents occur, is of less importance for the global economy than the unrecoverable damage caused by the accident.

With the correct trim, consumption is up to 5% lower with a constant course and speed on longer sailing routes. Saving fuel has a positive impact on reducing environmental pollution. The total reduction of exhaust gas in this case study is 3.05% CO₂, 4.33% CO, 4.46% NO_X, 4.55% SO_X, and 4.76% PM, which is not negligible.

This research revealed that a slightly improved ship’s trim can make significant savings in terms of consumption efficiency and pollution reduction. Research has indicated that it is necessary to navigate with a ship trimmed by the stern in narrow canals with limited maneuvering areas to improve ship maneuverability. To prevent maritime accidents, it is essential to adjust the ship’s trim according to the safety conditions to enhance maneuverability and prevent accidents. The optimum trim for different drafts and speeds has been determined from research conducted on a 11,400 TEU container ship.

Further research will be based on the development of optimization models for other container ship classes and by comparing them with software models, particularly for larger ships, which would lead to greater fuel savings and a decrease in environmental pollution.