Marine propellers are the unsung heroes of watercraft propulsion, driving boats and ships forward with precision and efficiency. However, not all propellers are created equal—each type is uniquely designed to suit specific vessel requirements, from speed and maneuverability to fuel efficiency and load capacity. Whether you’re navigating the open sea, harboring in shallow waters, or transporting heavy cargo across vast distances, the right propeller can make all the difference. This guide dives deep into the fascinating world of marine propellers, exploring the various types available and their unique applications. By the end, you’ll have a clear understanding of how these mechanical marvels are tailored to meet the diverse demands of modern boating and shipping.
What are the Main Types of Propellers Used in Marine Applications?
- Fixed-Pitch Propellers (FPP)
These propellers have blades set at a constant angle, providing durability and reliability. They are commonly used in vessels with consistent speed and power requirements.
- Controllable-Pitch Propellers (CPP)
With adjustable blade angles, CPPs allow for greater control and efficiency. They are ideal for ships that require frequent changes in speed or direction, such as tugboats and ferries.
- Ducted Propellers (Kort Nozzles)
These are encased in a duct or nozzle, enhancing thrust and efficiency, especially for slow-moving vessels like tugboats.
- Twin-Screw Propellers
Found on larger ships, twin-screw systems use two propellers to improve maneuverability and balance, providing better stability during operation.
- Surface-Piercing Propellers
Designed for high-speed vessels, these propellers operate partially above the water surface, reducing drag and increasing speed potential.
By understanding these main types, boat operators can select the best option to optimize performance and meet their specific operational needs.
What is a Fixed Pitch Propeller?
A Fixed Pitch Propeller (FPP) is a type of marine propeller in which the blade pitch is permanently set during manufacturing and cannot be adjusted during operation. This fixed design offers several advantages, such as simplicity, durability, and cost-effectiveness, making it a popular choice for a wide range of vessels, including cargo ships, fishing boats, and small pleasure craft.
Typically made from materials like bronze or stainless steel, FPPs are engineered for specific operational conditions. The propeller’s pitch, blade design, and diameter are customized based on factors like the vessel’s intended speed, engine power, and operating environment. One key benefit of FPPs is their robust construction, which makes them highly reliable under continuous and demanding usage.
Fixed pitch propellers are also notable for their energy efficiency, as they are optimized for a specific speed range. However, they lack the flexibility of variable pitch systems, which can adapt to changing conditions. Studies indicate that FPPs are best suited for vessels with consistent speed and load requirements. For example, in cargo ships, properly designed FPPs can achieve fuel efficiency rates of up to 85%, which is a critical factor in reducing operational costs and environmental impact.
Their relatively low maintenance requirements further enhance their appeal, as the absence of mechanical or hydraulic adjustment mechanisms means fewer components are susceptible to wear and tear. This durability ensures that FPPs maintain peak performance over extended periods, making them a practical and economical choice for many marine applications.
How Does a Controllable Pitch Propeller Work?
To understand how a Controllable Pitch Propeller (CPP) functions, it’s essential to first grasp the unique design that sets it apart from a fixed-pitch propeller. A CPP is equipped with blades that can be rotated around their vertical axis by a control mechanism, allowing the pitch to be adjusted dynamically. This ability enables the propeller to optimize thrust output at various vessel speeds and operational conditions, significantly improving efficiency and maneuverability.
At the core of the CPP mechanism is the hydraulic or mechanical control system housed within the hub of the propeller or actuator assembly. This system receives inputs from the vessel’s control console, typically located on the bridge. Through hydraulic cylinders or mechanical linkages, these inputs translate into precise pitch adjustments of the blades. Data shows that vessels utilizing CPPs can achieve fuel savings of up to 15% due to this adaptability, especially when operating under variable load conditions or during frequent speed changes.
Additionally, CPPs enhance a vessel’s ability to respond swiftly during critical operations, such as docking or navigating tight waterways. By enabling immediate reversal of thrust without stopping the engine, they reduce reaction times and improve safety. Advanced CPP designs now incorporate automation systems and monitoring technologies that further optimize performance. For instance, some modern systems can automatically adjust blade pitch based on real-time data, such as engine load or sea state, further boosting efficiency and reducing emissions. These capabilities make CPPs an indispensable component in modern marine engineering, particularly for vessels like tankers, fishing fleets, and ferries that require precise control and high versatility.
What is the Role of Ducted Propellers?
Ducted propellers, also known as Kort nozzles, play a critical role in enhancing the efficiency and performance of marine propulsion systems. These systems consist of a propeller encased within a specially designed duct or nozzle, which helps channel water more effectively. The primary benefit of ducted propellers lies in their ability to generate higher thrust at lower speeds, making them highly suitable for vessels such as tugboats, trawlers, and other workboats that require powerful, slow-speed maneuverability.
The duct surrounding the propeller is typically shaped to maximize hydrodynamic efficiency by reducing turbulence and improving water flow. Studies have shown that ducted propellers can improve thrust by approximately 10-20% compared to conventional, open-propeller designs under specific operating conditions. Additionally, they reduce cavitation—the formation of vapor bubbles caused by pressure changes in the water—thereby minimizing vibration and noise while extending the overall lifespan of the propulsion system.
Another key advantage of ducted propellers is their increased fuel efficiency. By channeling water more precisely and boosting performance at low speeds, these systems reduce the energy required for propulsion, indirectly cutting down fuel consumption and emissions. This functionality aligns well with modern sustainability goals in the marine industry, where reducing the environmental impact is a top priority.
Furthermore, ducted propellers provide a high degree of directional control and stability, particularly in rough sea conditions. This makes them indispensable for vessels operating in challenging environments. Technological advancements, such as integrating variable pitch propellers within the duct, have further improved adaptability and efficiency, ensuring that ducted propellers remain a vital solution in marine propulsion.
How Does the Number of Blades Affect Propeller Performance?
The number of blades on a propeller significantly impacts its performance by influencing its efficiency, thrust, and noise levels. Fewer blades typically result in higher efficiency because there is less drag and resistance in the water. However, more blades provide smoother operation, increased thrust, and reduced vibration, making them ideal for vessels requiring greater stability and power. The optimal number of blades depends on the vessel’s purpose and operational conditions, balancing efficiency with performance needs.
Understanding Propeller Blade Configurations
Propeller blade design is influenced by a range of factors that directly impact a vessel’s performance, including blade geometry, pitch, diameter, and material composition. Blade pitch, which refers to the angle of the blade, determines how much water is displaced per rotation. A higher pitch allows for greater speed but requires more engine power, while a lower pitch is better suited for slower speeds and higher torque.
Diameter, another critical factor, plays a significant role in efficiency. Larger diameters increase thrust, making them ideal for heavy, slower-moving vessels, whereas smaller diameters are better suited for high-speed crafts requiring quick acceleration. Modern designs often incorporate computational fluid dynamics (CFD) simulations to optimize these parameters, ensuring efficiency and reducing cavitation.
Material innovation also shapes propeller design. Traditional materials like bronze are being supplemented or replaced with advanced composites and titanium alloys, offering enhanced durability, corrosion resistance, and weight reduction. For instance, studies indicate that composite propellers can reduce weight by up to 30%, contributing to fuel efficiency and extending the life of the propulsion system.
Furthermore, the number of blades is chosen based on specific use cases. While three-blade propellers are common for recreational and smaller commercial vessels due to their balance of efficiency and thrust, high-powered vessels or ships requiring minimal vibration, such as naval or research vessels, often favor four or five blades.
Overall, advancements in material science and computational modeling have enabled engineers to fine-tune propeller designs for different operational needs, resulting in safer, more efficient, and environmentally friendly maritime propulsion systems.
What is the Impact of Two Propellers on Ship Stability?
The use of two propellers, often referred to as a twin-screw configuration, has a significant impact on ship stability, maneuverability, and operational efficiency. From a stability perspective, two propellers can help distribute thrust more evenly, minimizing vibrations and ensuring a smoother and more balanced operation. This configuration also provides greater reliability; if one propeller fails, the ship can still operate using the other, reducing the risk of complete propulsion loss.
Twin propellers greatly enhance a ship’s maneuverability, particularly in complex operational environments such as docking, navigating narrow waterways, or avoiding obstacles. Ships equipped with two propellers can achieve superior directional control because each propeller can be operated independently. For example, by running one propeller forward and the other in reverse, the vessel can effectively pivot in place, a feature critical to precise handling in tight conditions.
Studies have also shown that twin-screw designs can contribute to energy efficiency under specific operating conditions. While a single large propeller may deliver greater raw efficiency at constant speeds, the flexibility and control offered by two moderately-sized propellers can improve fuel consumption during variable or dynamic operations. Modern computational fluid dynamics (CFD) tools and simulation technologies enable naval architects to calculate optimal placement and alignment for twin propellers, further enhancing their benefits.
Finally, the adoption of twin propellers is crucial for vessels undergoing advanced stabilization or propulsion requirements, such as dynamic positioning systems in offshore or research operations. This configuration not only improves redundancy but also enhances roll and yaw control, ensuring steadiness even under turbulent sea conditions.
What are the Components and Design Factors of a Ship Propeller?
Components of a Ship Propeller
A ship propeller consists of several key components, each playing a vital role in its operation:
- Blades: Curved surfaces that generate thrust by interacting with water. The number and shape of the blades impact efficiency and performance.
- Hub: The central part of the propeller that connects the blades to the shaft.
- Boss Cap: Attached to the back of the hub, it helps reduce drag and improves hydrodynamic flow.
- Shaft: Transfers engine power to the propeller, enabling rotation and thrust.
Design Factors Influencing Ship Propellers
Several design factors contribute to the effectiveness of a ship propeller:
- Blade Number and Shape: Optimum blade numbers and shapes contribute to reduced vibration, noise, and cavitation.
- Diameter: The size of the propeller affects thrust output and directly correlates with the vessel’s speed and load capacity.
- Pitch: Refers to the angle at which blades are set, influencing the propulsion force and efficiency.
- Material: Common materials like bronze or stainless steel provide durability and resistance to corrosion.
Careful consideration of these components and design factors ensures optimal performance, fuel efficiency, and operational reliability.
Exploring the Propeller Shaft and Tail Shaft
The propeller shaft and tail shaft form essential components of a vessel’s propulsion system, ensuring the efficient transfer of energy from the engine to the propeller. The propeller shaft connects the engine’s gearbox to the tail shaft, transmitting rotational energy to propel the vessel forward. Modern propeller shafts are engineered with high-strength materials such as carbon steel or alloy steel to achieve exceptional durability and resistance to stress under high torque conditions.
The tail shaft, positioned at the aft end of the propulsion system, supports the propeller, facilitating smooth rotation and optimal alignment. Typically housed within a stern tube, the tail shaft operates in demanding underwater environments. High-performance seals and bearings, such as water-lubricated or oil-lubricated bearings, play a critical role in reducing friction and preventing water ingress. For instance, water-lubricated bearings have gained popularity for their eco-friendly design and compatibility with modern regulatory standards.
Numerical data highlights the load-bearing capacities and sizes of these components. For example, propeller shafts in merchant vessels can handle rotational speeds typically exceeding 250 RPM under loads of several hundred metric tons. Advanced computational design techniques, like finite element analysis (FEA), further optimize shaft dimensions, reducing vibration and enhancing fatigue resistance.
By integrating precision engineering practices and stringent material selection, both the propeller shaft and tail shaft contribute significantly to the vessel’s reliability and efficiency across various operational conditions.
Key Elements of Propeller Design
The design of a propeller is a critical aspect of ensuring optimal performance, efficiency, and durability for a vessel. Modern propellers are engineered with several key considerations, incorporating both theoretical principles and advanced technology to achieve desired outcomes.
- Blade Geometry
The shape, size, and pitch of the propeller blades play a fundamental role in determining how effectively thrust is generated. Blades are often tailored to the vessel’s specific operating conditions. For example, high-speed vessels may utilize propellers with fewer, longer blades to minimize drag, while larger vessels rely on multi-blade configurations to distribute force efficiently.
- Material Selection
Propellers are most commonly crafted from materials like bronze alloys, stainless steel, or nickel-aluminum-bronze. These materials offer a combination of corrosion resistance, mechanical strength, and durability to withstand harsh marine environments. Modern advancements also explore composite materials to reduce weight while retaining structural integrity.
- Hydrodynamic Efficiency
Achieving optimal hydrodynamic efficiency requires minimizing cavitation—air or vapor bubble formation near the blade surface—which can lead to vibration, energy losses, and eventual blade erosion. Computational Fluid Dynamics (CFD) modeling allows designers to predict and refine blade performance in various conditions, ensuring smoother water flow and reduced energy loss.
- Number of Blades and Diameter
Propellers with a higher number of blades tend to operate more quietly and smoothly due to evenly distributed pressure, essential for passenger ships or submarines. Conversely, the diameter is matched with engine power and hull design, balancing thrust with operational efficiency.
- Revolution Rate and Tip Speed
The propeller’s revolution rate and corresponding tip speed dictate the balance between efficiency and noise generation. Higher tip speeds are correlated with increased noise and cavitation risks but may be necessary for specific vessel types. Advanced design techniques mitigate these challenges without compromising performance.
- Energy-Saving Devices (ESDs)
Incorporating innovative features like fins, ducts, or pre-swirl stators around the propeller enhances energy recovery and can reduce fuel consumption. Many modern vessels now integrate ESDs into their propeller systems to align with global sustainability goals.
- Testing and Optimization
Post-design, propellers undergo extensive model testing in towing tanks and with simulation tools to analyze their real-world performance. This step ensures that the theoretical designs translate accurately into practical applications, reducing the need for costly on-site adjustments.
By carefully balancing these elements and leveraging advancing technologies in computational design and materials science, modern propellers are not only enhancing vessel performance but also contributing to greater fuel efficiency and environmental sustainability.
Understanding the Propeller Hub
The propeller hub serves as the central point of connection between the propeller blades and the propulsion system. Its role is critical, as it ensures the effective transmission of torque from the engine to the blades, enabling smooth and efficient operation. Typically cylindrical in shape, the hub houses key components like the spline, which locks the hub in position on the shaft, and the retaining nut that secures the assembly.
Modern propeller hubs are designed with advanced engineering techniques to optimize performance and durability. For instance, some hubs now feature cushioned drive hubs, which reduce vibrations and absorb shocks during operation, resulting in quieter performance and enhanced longevity. Materials used in these hubs, such as corrosion-resistant alloys or composites, are chosen to withstand extreme operational environments, from saltwater exposure to high mechanical stresses.
According to recent advancements in marine engineering, some hub systems now integrate automatic pitch control mechanisms. This allows the blades to adjust their angle dynamically based on the vessel’s speed and load, significantly improving efficiency. Statistical data highlights that ships with such adjustable pitch hubs record fuel savings of up to 15-20%, while also reducing CO₂ emissions.
The design and maintenance of the propeller hub are pivotal in ensuring seamless maritime operations. Routine inspections, proper lubrication, and alignment checks are critical practices to prevent wear and enhance the hub’s lifespan, thereby keeping vessels operational while minimizing repair costs. By combining innovation with regular upkeep, the propeller hub continues to be a driving force behind efficient and eco-friendly marine propulsion systems.
How Do Boat Propellers Generate Thrust?
Boat propellers generate thrust by converting the rotational energy from the engine into forward or backward motion. The blades of the propeller are angled so that when they spin, they push water backward, creating a reaction force that propels the boat forward. This process is based on Newton’s third law of motion, which states that every action has an equal and opposite reaction. The speed and shape of the propeller, as well as the angle of the blades, directly influence the amount of thrust produced, ensuring efficient movement through the water.
The Concept of Propeller Pitch and Its Importance
Propeller pitch refers to the distance a propeller would theoretically move forward in one complete revolution if there were no slippage in the water. It is a critical factor in determining a vessel’s performance, efficiency, and suitability for specific applications. Measured in inches, propeller pitch directly influences the speed and power of a boat; higher pitches generally allow for faster speeds but may require more engine power, while lower pitches provide better acceleration and are ideal for towing or heavy loads.
For instance, a propeller with a 21-inch pitch theoretically moves 21 inches forward with each spin. However, in real-world scenarios, factors like water resistance and vessel weight cause some slippage, meaning the actual distance traveled per revolution is slightly less. Research and testing data indicate that optimal pitch selection can enhance fuel efficiency by up to 10-15% for many boats, making it a crucial consideration for boaters aiming for cost-effective performance.
Additionally, the relationship between RPM (revolutions per minute) and pitch is vital. If the pitch is too high for an engine’s power capabilities, the engine may struggle to reach the ideal RPM range, compromising performance and increasing wear. Conversely, a pitch that is too low could cause the engine to over-rev, leading to inefficiencies and potential damage. Properly matching a propeller’s pitch to the boat’s specifications, engine type, and typical use is fundamental to achieving the best overall performance and longevity.
How Does a Screw Propeller Propel the Ship?
A screw propeller generates thrust to move a ship forward by utilizing the principle of Newton’s Third Law, which states that every action has an equal and opposite reaction. The propeller, shaped like a helical screw, rotates and pushes water backward. This backward flow of water, known as the slipstream, creates the reactive force that propels the ship forward. The thrust generated depends on several factors, including the propeller’s diameter, pitch, shape, and the number of blades.
Modern propellers are designed to maximize efficiency by reducing resistance and optimizing thrust. For instance, studies show that five-blade propellers often offer a balance of smooth operation and efficiency in large vessels, while smaller vessels benefit from three or four blades for enhanced speed. The angle, or pitch, of the blades plays a pivotal role in determining the speed and energy efficiency of the propulsion. A finely tuned pitch improves fuel consumption, often reducing it by up to 15% in optimal conditions.
Cavitation, a phenomenon when pressure around the propeller drops below water’s vapor pressure, is a critical consideration in design to prevent damage and efficiency loss. Technological advancements, such as computer-aided hydrodynamic simulations, allow for better customization of propellers to minimize cavitation and maximize thrust. Additionally, the use of lightweight and corrosion-resistant materials like composite alloys ensures durability and performance in diverse marine environments. These innovations significantly enhance the ability of ships—from ferries to massive cargo vessels—to operate efficiently and reliably.
What are the Advantages and Disadvantages of Different Propeller Types?
- Fixed-Pitch Propellers (FPP)
Advantages: Simple design, low maintenance requirements, and cost-effective. They are highly durable and ideal for consistent operating conditions.
Disadvantages: Limited flexibility—unable to adjust to changing load or speed conditions, reducing efficiency in variable environments.
- Controllable-Pitch Propellers (CPP)
Advantages: Allows for greater operational control by adjusting blade angles, improving efficiency across varying speeds and loads. Ideal for vessels requiring frequent speed adjustments.
Disadvantages: More complex design, higher upfront and maintenance costs, and additional susceptibility to mechanical issues.
- Ducted or Kort Nozzle Propellers
Advantages: Increased thrust at low speeds, suitable for tugboats or vessels requiring high towing power. Better fuel efficiency during slow operations.
Disadvantages: Reduced effectiveness at high speeds and less maneuverability in certain conditions.
- Surface Piercing Propellers
Advantages: High efficiency at very high speeds, excellent for racing boats or high-performance vessels. Reduced drag due to partial submersion.
Disadvantages: Limited general application, increased vibration, and wear due to exposure to air and water interaction.
- Twin-Screw Propellers
Advantages: Enhanced maneuverability, particularly in port operations or tight areas. Redundant propulsion increases safety.
Disadvantages: Higher installation and running costs, requiring more complex alignment and maintenance.
By understanding the specific needs of a vessel and its operational environment, the best propeller type can be chosen to balance efficiency, cost, and reliability.
Comparing Fixed-Pitch Propellers with Controllable Pitch Propellers
When evaluating Fixed-Pitch Propellers (FPP) and Controllable Pitch Propellers (CPP), their characteristics, operational flexibility, efficiency, and cost must be carefully assessed to determine the optimal choice for specific maritime applications.
Fixed-Pitch Propellers (FPP)
FPP have blades set at a fixed angle, making them mechanically simple, reliable, and cost-effective. They are highly efficient in operations requiring consistent speed or load, such as cargo shipping or bulk carriers. FPP’s robust design demands less frequent maintenance and is particularly suitable where operational conditions remain stable. However, they offer limited maneuverability, as their performance cannot be adjusted dynamically to varying loads or directional changes.
Controllable Pitch Propellers (CPP)
CPP, on the other hand, have blades that can be rotated to change their angle of attack. This adjustability allows for optimized propulsion in fluctuating conditions and tasks requiring frequent speed or direction changes, such as ferries, tugs, or offshore vessels. CPP systems enhance fuel efficiency by adapting more effectively to varying loads and can reduce engine wear over time. Nevertheless, CPP systems entail higher initial costs, complex maintenance requirements, and increased vulnerability to mechanical faults due to their sophisticated design.
Data-Driven Comparison
Fuel efficiency is often a critical deciding factor. Studies indicate that CPP can achieve 5-15% greater fuel savings in variable load conditions compared to FPP, particularly in vessels with frequent speed adjustments. However, in steady operational profiles like long-haul shipping routes, FPP demonstrates similar levels of efficiency at a significantly lower cost. For larger vessels, the installation and maintenance costs of CPP systems can be 15-30% higher than FPP systems, making long-term cost planning a pivotal consideration.
Pros and Cons of Bladed Propeller Designs
Bladed propeller designs, commonly used in marine propulsion, come with a range of advantages and disadvantages that must be weighed carefully when selecting the right type for specific vessel operations.
Pros
- Efficiency in Propulsion
A well-designed bladed propeller can achieve high levels of propulsion efficiency, particularly at consistent speeds. Fixed-Pitch Propellers (FPP), for example, are optimized for steady operations and provide smooth thrust, reducing fuel consumption over typical routes.
- Durability and Maintenance
The robust design of bladed propellers ensures long-term durability. With fewer moving parts compared to more complex systems like Controllable-Pitch Propellers (CPP), FPP requires less maintenance and proves cost-effective over time.
- Cost-Effectiveness
For vessels with predictable travel patterns, such as cargo ships or tankers, bladed designs, particularly FPP, are economically favorable due to lower initial costs and reduced servicing needs.
- Powerful Thrust
Propellers with optimized blade configurations can generate substantial thrust in shallow or deep waters, supporting various applications like heavy cargo transit and fishing vessels.
Cons
- Limited Maneuverability
Fixed-pitch options in bladed propellers lack adaptability for dynamic operational environments. This limitation is especially evident in vessels requiring frequent acceleration, deceleration, or precision steering, as they cannot adjust blade angles on demand.
- Fuel Inefficiency in Varying Conditions
While fixed-pitch propellers offer efficiency at constant speeds, their inability to adapt blade pitch leads to decreased fuel economy under variable speed or load conditions.
- Cavitation Risks
Cavitation, the formation of vapor cavities or bubbles near blade surfaces, poses a significant risk. This phenomenon can lead to reduced performance, increased noise, and potential long-term damage to the propeller’s structure, especially if the design is not tailored to the operating conditions.
- Noise and Vibration
Bladed propellers, particularly older or less advanced models, can generate considerable noise and vibrations, which may affect crew comfort and marine life in surrounding areas.
Reference Sources
Frequently Asked Questions (FAQs)
Q: What are the different types of marine propellers?
A: Marine propellers come in various types, including fixed pitch propellers, controlled pitch propellers, and ducted propellers. Each type serves specific purposes and is chosen based on the type of ship and operational needs.
Q: How does a blade propeller function?
A: A blade propeller functions by converting rotational energy from the main engine into thrust. This thrust is generated as the propeller blades push against the water, making the boat or ship move forward.
Q: What is a controlled pitch propeller (CPP), and how does it differ from conventional propellers?
A: A controlled pitch propeller (CPP) allows the pitch of the blades to be adjusted while in operation. This differs from conventional propellers, where the pitch angle is fixed. The ability to change the pitch provides better maneuverability and efficiency.
Q: What are the main components of the propeller?
A: The main components of a propeller include the hub, blades, and body attached to the propeller shaft. These components work together to convert engine power into thrust.
Q: How does the pitch of a propeller affect its performance?
A: The pitch of a propeller determines how much water the propeller moves during a rotation. A higher pitch means more displacement with each turn, affecting speed and fuel efficiency. Adjusting the pitch by rotating the blade can optimize performance for different conditions.
Q: What are the advantages of using a CPP type propeller?
A: CPP type propellers offer advantages such as improved fuel efficiency, enhanced maneuverability, and the ability to reverse thrust easily. This makes them ideal for various boat propeller types and ship applications.
Q: Why are three propellers sometimes used on ships?
A: Three propellers are often used on larger ships to distribute the propulsion load more evenly across the vessel. This configuration can provide better balance and efficiency, allowing the ship to move more smoothly through the water.
Q: How does the propeller drive system work?
A: The propeller drive system works by transmitting power from the main engine to the propeller shaft. This rotational force causes the propeller to spin, generating thrust and moving the ship forward or backward, depending on the propeller’s rotation.
Q: What is the relationship between the displacement that a propeller makes and the ship’s speed?
A: The displacement that a propeller makes for every full rotation is directly related to the ship’s speed. More displacement typically means higher speed, as more water is pushed back, propelling the ship forward more effectively.
