Propulsion And Manoeuvring Systems

Summary

This script offers an in-depth look at various ship propulsion and maneuvering systems, emphasizing the importance of hull form and engine power for optimal performance. It discusses traditional single propeller setups, controllable pitch propellers for thrust optimization, and advanced rudder systems like flap, rotor, and Schilling rudders that enhance maneuverability. The script also touches on diesel and steam turbine engines, the impact of rudder design on steering, and the use of autopilots for precise navigation.

Takeaways

• 🚢 The chapter provides an overview of common propulsion and maneuvering systems in ships, emphasizing the importance of hull form, engine power, and propeller and rudder systems for optimal performance.
• 🔄 Most ships use a traditional single fixed propeller and rudder, which can be challenging for maneuvering in confined waters.
• 🛠 Some vessels are equipped with alternative propeller and rudder systems to balance maneuverability and economy more effectively.
• 💡 Diesel engines are widely used due to their cost-effectiveness, with low-speed engines operating directly onto the shaft and medium to high-speed engines often used in smaller vessels.
• ⚙️ The response time of steam turbines to control orders is slow, which requires careful planning when maneuvering.
• ⚓ Controllable pitch propellers (CPP) allow for thrust optimization under different load conditions and can be adjusted using a hydraulic mechanism.
• 🔄 The direction of a ship's turn can be influenced by the rotation direction of the propeller, with most sea propellers being left-handed, moving anti-clockwise.
• 🌀 Ducted propellers provide increased power output and better steering, especially at low speeds, by utilizing a shroud that forces water through a smaller aperture.
• 🛳 Conventional rudders are a compromise between economy and necessity, with different designs like spade, balanced, and semi-balanced rudders serving different types of vessels.
• 🛑 Advanced rudder systems like flap, rotor, and T rudders offer improved maneuverability and turning performance, though they come at a higher cost.
• 🕹 The Schilling rudder system uses a fixed-pitch propeller with two synchronized rudders controlled by a joystick, providing unique maneuvering capabilities.
• 🔄 The direction of a ship's turn can be influenced by the design of the propellers, with twin-screw ships often having right-hand turning starboard propellers and left-hand turning port propellers to reduce cavitation and enhance transverse thrust.

Q & A

What is the main focus of the chapter discussed in the transcript?

The chapter focuses on an overview of the most common propulsion and maneuvering systems used in ships, including the relationship between hull form, engine power, and propeller and rudder systems.

Why do traditional single fixed propellers pose a challenge for ship handlers?

Traditional single fixed propellers are designed primarily for economical travel from point A to B, which can be challenging for ship handlers when maneuvering in confined waters due to limited maneuverability.

What are controllable pitch propellers and how do they optimize thrust?

Controllable pitch propellers are a type of propulsion system that allows for the modification of the pitch to optimize thrust under different load conditions, improving maneuverability and fuel efficiency.

How do diesel engines operate in ships, and what are some considerations for ship handlers?

Diesel engines, especially low-speed ones, operate directly onto the shaft. Ship handlers must consider the difficulty of starting the engine when making headway and the potential limitations of starter availability.

What is the main drawback of steam turbines from a ship handler's perspective?

Steam turbines have a slow response to control orders for changing the direction of shaft rotation, which requires careful planning of each movement when maneuvering the ship.

What are ducted propellers and what advantages do they offer?

Ducted propellers are enclosed in a tube or tunnel with the propeller inside. They offer more output power, reduced propeller wash, better steering at low speeds, and improved turning characteristics.

What is the difference between a conventional rudder and a flap rudder?

A flap rudder has an additional flap on the trailing edge for steering, allowing up to twice the steering power compared to a traditional rudder, making the ship more maneuverable.

What is the purpose of the rotor rudder, and how does it improve ship turning performance?

The rotor rudder is a conventional rudder with a rotating cylinder mounted vertically on the edge. It smooths the water flow at high rudder angles, improving the ship's turning performance.

What is the Schilling rudder system, and how does it differ from other rudder systems?

The Schilling rudder system features a fixed-pitch propeller that is constantly running, with two rudders that can rotate through a total arc of 145 degrees. It is controlled by a single joystick, offering a unique and efficient maneuvering capability.

How do twin-screw ships achieve better maneuverability, and what factors contribute to this?

Twin-screw ships achieve better maneuverability through a combination of factors including propeller configuration, the effect of talk, transverse thrust, the pivot point, and the skill of the ship handler.

What is the importance of planning turns in confined waters, and how can autopilots assist with this?

Planning turns in confined waters is crucial for navigational safety and precision. Modern autopilots with preset turning radius or fixed rate of turn modes can assist in executing and controlling turns accurately.

Outlines

00:00

🚢 Ship Propulsion and Maneuvering Systems Overview

This paragraph introduces the common propulsion and maneuvering systems found on modern ships, emphasizing the relationship between hull form, engine power, and rudder systems. Traditional setups often consist of a single fixed propeller and rudder, designed for economical travel. Challenges arise when maneuvering in tight spaces. Some vessels have advanced systems for improved maneuverability and economy. Diesel engines are prevalent due to their cost-effective operation, with low-speed engines running at 85-130 RPM, and medium to high-speed engines offering better responsiveness and power efficiency. Steam turbines are used in larger, high-speed ships but have slow response times. Controllable pitch propellers offer thrust optimization and are controlled by a Combinator for balanced performance and fuel savings.

05:00

🌀 Advanced Propeller and Rudder Technologies

The second paragraph delves into advanced propeller and rudder technologies, such as controllable pitch propellers that allow for speed adjustments and low-speed maneuvering. Ducted propellers provide increased power and better steering characteristics. Conventional rudders are discussed, highlighting their limitations and the benefits of semi-balanced designs. The paragraph also explores various rudder types, including spade, full, and heel rudders, each with specific applications and advantages. Modern autopilots with preset steering modes for turns are mentioned, emphasizing the importance of planning and precision in maneuvering.

10:01

🛳️ Enhanced Rudder Systems for Improved Maneuverability

This section discusses the development of more efficient and advanced rudder systems over the past few decades. Flap rudders, rotor rudders, and T rudders are introduced, each offering increased steering power and improved turning performance. The flap rudder uses an additional flap for enhanced maneuverability, while the rotor rudder smooths water flow for better performance at high angles. The T rudder combines features of flap and rotor designs for optimal performance, albeit at a higher cost. Special rudders capable of deploying up to 70 degrees are also mentioned, providing outstanding lateral motion when used with bow thrusters. The paragraph concludes with a unique rudder system featuring a fixed-pitch propeller with twin Schilling rudders controlled by a joystick, offering a different approach to maneuvering.

15:01

⭕️ Twin-Screw Ships and Autopilot Maneuvering Strategies

The final paragraph examines twin-screw ships, which are designed with right-hand and left-hand turning propellers to reduce cavitation and maximize transverse thrust. The importance of the rudder's position in the propeller slipstream is highlighted, along with the factors contributing to a ship's maneuverability. Autopilots with preset turning radius and rate of turn modes are discussed, emphasizing the benefits of planning turns for precision and predictability. The paragraph provides a mathematical formula for calculating the rate of turn and suggests using the largest possible radius and accounting for external factors like wind and current. The importance of adjusting heading manually when necessary is also noted, along with the advantages of using a low rate of turn for safety, economy, and comfort.

Keywords

💡Propulsion Systems

Propulsion systems are the mechanisms that move a ship through the water. In the context of the video, they are crucial for understanding how ships are maneuvered and the efficiency of their travel. The script discusses traditional single fixed propellers as well as more advanced systems like controllable pitch propellers and ducted propellers, highlighting their impact on a ship's maneuverability and economic operation.

💡Maneuvering Characteristics

Maneuvering characteristics refer to how a ship handles and responds to control inputs for changing direction or speed. The video emphasizes that these characteristics are directly related to the hull form and are influenced by the engine power and the propeller and rudder systems. This concept is central to the theme of the video, as it discusses various systems designed to improve a ship's ability to maneuver in different conditions.

💡Diesel Engine

A diesel engine is a type of internal combustion engine that is widely used in ships due to its cost-effective operation. The script explains that low-speed diesel engines are connected directly to the ship's shaft and mentions the challenges of starting the engine when the ship is still moving. This keyword is important for understanding the power source of many ships and the practical considerations of operating them.

💡Steam Turbine

A steam turbine is another type of engine that is often found in large ships or those requiring high speed. While the script notes that steam turbines are smooth running and reliable, it also points out their slow response to control orders, which is a significant drawback for ship handlers when maneuvering. This term is key to understanding the different engine types and their operational characteristics.

💡Controllable Pitch Propellers

Controllable pitch propellers (CPP) are a type of marine propulsion system that allows for the adjustment of the propeller's pitch to optimize thrust under various load conditions. The script describes how this system can improve fuel efficiency and propeller performance by automatically balancing engine revolutions against propeller pitch. This keyword is central to the video's theme of discussing advanced systems for improved ship maneuverability.

💡Ducted Propellers

Ducted propellers are a specialized type of propeller enclosed within a shroud or duct, which enhances their power output and efficiency. The script mentions that these propellers provide benefits such as reduced propeller wash and better steering at low speeds. This concept is important for understanding innovative solutions to improve a ship's maneuvering capabilities.

💡Conventional Rudders

Conventional rudders are the standard steering devices found on many ships, designed as a compromise between economy and necessity. The script discusses their functionality, efficiency up to certain angles, and the limitations they present in terms of maneuverability at slow speeds. Understanding conventional rudders is essential for grasping the basics of ship steering and the need for more advanced systems.

💡Advanced Rudder Systems

Advanced rudder systems, such as flap rudders, rotor rudders, and T rudders, are designed to improve a ship's maneuverability and turning performance. The script provides examples of these systems and explains how they work, such as the flap rudder using an additional flap on the trailing edge for steering or the rotor rudder smoothing water flow at high angles. These keywords are integral to the video's exploration of modern solutions for ship maneuvering.

💡Twin-Screw Ships

Twin-screw ships are designed with two propellers, often turning in opposite directions, and are equipped with two rudders. The script explains the benefits of this configuration, such as reduced cavitation and improved transverse thrust. This term is key to understanding the video's discussion on the maneuverability advantages of certain ship designs.

💡Autopilot Systems

Autopilot systems are used on ships to automate steering and maintain a course, especially useful in confined waters or for executing turns with a preset turning radius. The script mentions modern autopilots with steering modes for precise track keeping and planning turns, which is important for understanding how technology aids in ship maneuvering and route planning.

💡Rate of Turn

The rate of turn is a measure of how quickly a ship changes its heading, typically measured in degrees per minute. The script provides a mathematical formula for calculating the rate of turn and discusses its practical implications for ship maneuvering, such as the advantages of using a low rate of turn for safety and fuel efficiency. This keyword is central to the video's educational content on ship steering and navigation.

Highlights

Overview of common propulsion and maneuvering systems in ships

Maneuvering characteristics are related to hull form and engine power

Traditional ships use single fixed propeller and rudder systems

Challenges in maneuvering in confined waters with traditional systems

Some vessels equipped with advanced propeller and rudder systems for better balance

Diesel engines are widely used for their cost-effective operation

Low speed diesel engines operate directly onto the shaft with specific RPM ranges

Difficulties in starting diesel engines while making headway due to propeller resistance

Medium and high speed diesels are popular in smaller vessels for their responsiveness

Steam turbines are found in large ships requiring high speed but have slow response

Controllable pitch propellers optimize thrust under different load conditions

Combinator balances engine revolutions against propeller pitch for fuel savings

Ducted propellers offer more output power and better steering characteristics

Conventional rudders are a compromise between economy and necessity

Advanced rudder designs like flap, rotor, and T rudders improve maneuverability

Twin Schilling rudder system with a constantly running propeller offers unique maneuvering

Twin-screw ships have specific propeller and rudder configurations for better maneuverability

Autopilots with steering modes for preset turning radius or fixed rate of turn

Importance of planning turns with the largest possible radius and adjusting for conditions

Mathematical formulas for calculating rate of turn and turn radius

Autopilots capable of following a preset curve for precision track keeping

Transcripts

This chapter will give you a general

overview of the most common propulsion

and maneuvering systems used today ships

maneuvering characteristics are directly

related to her hull form optimal

performance depends upon the whole shape

in conjunction with engine power and the

propeller and rudder systems most ships

are still equipped with traditional

single fixed propeller and single rather

designed for getting the ship from A to

B as economically as possible

this often represents a challenge to the

ship handler with reference to

maneuvering in confined waters in order

to achieve a better balance between

maneuverability and economy some vessels

are equipped with propeller and rudder

systems that differ considerably from

the traditional systems general

information about some of these new

systems will be given later in this

chapter the diesel engine is very widely

used as it tends to be the least

expensive to run low speed diesel

engines operate directly onto the shaft

maximum speed RPM is in the range 85 to

130 RPM the ship handler must remember

the difficulties can be experienced in

starting the engine when still making a

lot of headway

this is because the propeller will be

trying to turn in the water stream and

because of the direct drive the engine

tends to turn in the forward direction

another important thing to remember is

that sometimes there might be a limited

amount of starter available IE too many

starting orders during a short time

interval may empty the start air

reservoir making engine starts

impossible for some time

medium and high speed diesels are

popular arrangements in smaller vessels

fairies car carriers and other special

ships one or several engines drive shaft

through a gearbox

since clutch the engines are normally

operated from the bridge and are very

responsive and like their low speed

relatives can develop almost as much

power astern as ahead but of course the

application of this astern power is less

efficient as ships hulls propellers and

rudders are usually designed to work in

the head direction the steam turbine is

often found in large ships and on ships

where high speed is required a turbine

ship while being smooth running and more

reliable in the mechanical sense has one

major drawback from the ship handlers

point of view its response to control

orders for change of direction of shaft

rotation are slow

thus when maneuvering a turbine driven

ship each movement must be carefully

planned controllable pitch propellers

are very practical because by modifying

the pitch they allow for thrust

optimization under different load

conditions with the controllable pitch

propellers the user can modify the pitch

normally by means of a hydraulic

mechanism click on each hotspot to learn

more about CP pitch is the distance of

propeller drives forward for each

complete revolution assuming it is

moving through a solid element just like

a wood screw does when using a CP

propeller the main engine has to be

clutched in so the propeller is

continuously turning usually at quite

high revolutions as it is neither

practicable more economical to run an

engine continuously at excessive

high-rpm it is important to have some

kind of combined control over both RPM

and pitch so that the pitch for slow

speeds is balanced by a reduction in

revolutions on most ships this is

achieved by installing a Combinator

which automatically balances engine

revolutions

against propeller pitch that's producing

a savings in fuel and better propeller

performance to use ahead power a ship

with CP propeller is not restricted to

the old step progression that has been

associated with fixed pitch propellers

any speed can be selected by adjusting

the Combinator control to the required

setting it is also possible to set the

propeller pitch for extremely low speeds

so when it is essential to proceed at

very slow speeds the propeller and

rudder are still active and steerage way

can be maintained for a lot longer than

usual when low speed or stop are

demanded the blades of the CP propeller

are set with a very fine angle and pitch

if the ship's speed is too high and does

not already matched the propeller speed

the flow of water through it will be

restricted and turbulence will develop

behind the propeller which will also

have an adverse effect upon the rudder

if the ship's speed is not reduced

slowly and progressively in much the

same way as a large directional unstable

ship the rudder will be shielded and the

steering may become erratic or poor one

of the most common concerns mentioned by

many navigators and pilots is the

uncertainty as to which way the bear

will count if at all when a CP

propellers put a stern to answer this

question it is necessary first to know

which way the propeller is turning when

it is viewed from astern the majority of

the sea propeller is left-handed ie they

move in an anti-clockwise direction the

effect however is similar to a fixed

pitch right-handed propeller working

astern IE the bow make aunt to starboard

it is important to note that the

transverse thrust on some ships with CP

propellers maybe weekend unreliable user

vortices or turbulence around the

propeller blades it

therefore advisable to exercise some

caution when anticipating the effects of

stern power on some CP ships many

vessels ranging from tugs to large

ocean-going ships are equipped with

ducted propellers a shroud or duct is a

tube or tunnel light construction with

the propeller inside the forward end of

the duct has a larger diameter than the

aft end the increased power comes from

the propeller constantly drawing a

massive water into the duct which then

has to be forced out through a smaller

aperture the main advantages which can

be expected of the ducted propeller are

more output power from the propeller

reduced propeller wash to a smaller arc

thereby reducing erosion of canal and

river banks better steering especially

at low speed better turning

characteristics conventional rudders

found on thousands of ships worldwide

represent a compromise between economy

and necessity conventional rudders

normally function satisfactorily for

normal steering and cause change

requirements in open waters the basic

conventional rudder is efficient up to

maximum 45 degrees at high angles the

rudder is not capable of maintaining a

smooth water flow across both sides of

the rudder and the rudder stalls IE

loses its effect if the runner has its

entire area after the rudder stock then

it is unbalanced a rather with between

twenty and forty percent of its area

forward of the stock is balanced most

modern brothers are of the semi balanced

design this means that a certain

proportion of the water force acting on

the after part of the rudder is

counteracted by the force acting on the

forward part of the rudder hence the

steering gear can be lighter and smaller

there are several types of rudder

designs pick the hot spots to see the

three most common types

this is the most used rather type on

ferries and smaller ships the Spade

rather provides good maneuverability

this type of brother is most commonly

used on bigger ships it is not as

effective a speedrunner of the same size

the heel rather is supported with

bearings on the top and bottom providing

an enjoyable rudder construction

conventional riders are somewhat

restricted when it comes to

maneuverability at slow speed in

confined waters several manufacturers

have developed more efficient and

advanced radar systems the last two or

three decades and quite a few ships are

now fitted with modern and more

efficient rudders click the rudders to

see some examples the flap rudder is

different from a conventional rather in

that it utilizes an additional flap on

the trailing edge for steering this

allows up to twice the steering power

compared to a traditional rudder

translating into a much more

maneuverable ship the rotor is

essentially a conventional rudder but

with the addition of a rotating cylinder

mounted vertically on the edge of the

rudder

the purpose is to smooth the water flow

at high rudder angles and thereby

improve ship turning performance the

purpose of the tea rather is to combine

the advantages of the flap and rotor

rather in order to get the best possible

rather performance the performance is

indeed excellent but unfortunately the

price is high

not many ships invest in this excellent

rudder system this is an alternative

design to the flap rudder the shape of

the rudder is such that it can be turned

up to 70 degrees

and still retain excellent performance

the four body of the rudder is

elliptical in shape but runs into a rear

body section which is concave expected

turning performance with flap rotor and

T rudder systems this diagram shows the

expected increase internal performance

for a ship equipped with a modern flap

or rotor rotor system as can be seen

from the diagram considerable turning

improvements are obtained special

rudders deploying up to 70 degrees are

used in much the same way as

conventional rudders when used in

combination with a good bow thruster it

is possible to develop outstanding

lateral motion care should be taken not

to move with two high-speed as this may

damage the road system or result in

unnecessary wear and tear some systems

don't allow a rudder angle of more than

35 degrees when the speed is more than 5

knots

this system is totally different from

all other rudder systems both in design

and operation the most unusual but

essential feature of this system is the

propeller which even though it is fixed

pitch is constantly running with the

engine permanently on ahead revolutions

normally in maneuvering speed full ahead

immediately astern of the propeller in

place of the conventional rudder are two

shilling rudders each of which can

rotate through a total arc of 145

degrees the rudders do not act

independently of each other but are

instead synchronized to work in harmony

with each other in response to a single

joystick control on the bridge between

shielding rudder system with its

constantly running propeller seems a

little strange at first however most

officers after a short period of

instruction appear to get the feel for

it relatively quickly in this diagram

you can see different joystick

missions and corresponding rather

positions if the joy-stickies back from

normal full ahead with the joystick in

full forward the rudders progressively

open outwards deflecting the propellers

wash or drive and thus reducing the

ship's speed to obtain stern power up to

the equivalent of full astern the

joystick is pulled right back until each

runner has rotated right around to 105

degrees

thus closing the gap between them the

propeller wash is then deflected

forwards and works in much the same way

as the reverse thrust of an aircraft's

jet engines when it is deployed to stop

the aircraft after landing study the

diagram carefully to understand how the

twins Schilling rather system works

the conventional propeller and rudder

arrangement has been around for a long

time the propeller can be designed to

turn clockwise or anti-clockwise the

position of the rudder which normally

lies in the propeller slipstream is

critical

with regard to cavitations as well as

efficiency conventional rudders normally

have a maximum rather angle of about 35

degrees

generally speaking a ship with a right

hand turning propeller can be expected

to have slightly smaller turning radius

to Port to starboard and vice versa for

a ship with left-hand turning propeller

conventional design twin-screw ships are

normally designed with the right hand

turning starboard propeller and a

left-hand turning port propeller and

equipped with two rudders one behind

each propeller the reason for making the

outward turning propellers is twofold

reducing cavitations and taking greatest

benefit from the transverse thrust the

essence of good maneuverability of

twin-screw ships is not the result of

one factor alone but rather several

factors combined these factors are the

router configuration the effect of talk

the effect of transverse thrust the

pivot point the turning ability a

competence ship handler in order to make

the turning maneuvers accurate and

predictable several modern autopilot

have steering modes for executing and

control of turns with preset turning

radius or fixed rate of turn in confined

waters the simplicity of the geometrical

shape of the circle will ease the

navigation and the control of the actual

track today when documentation of proper

route planning is an IMO requirement and

more and more ships are equipped with

Exodus and advanced auto pilots even

turns in open waters should be planned

and executed in an optimal way pick the

Waypoint

course and track mode buttons on the

autopilot to see the difference between

them

when turning with constant rate of turn

the radius may not remain constant do to

speed reduction during the term however

if the turn is made with very low rate

of turn for example 6 degrees per minute

the speed loss is next to nothing

no constant rate of turn setting on the

autopilot is most useful on passenger

ships fairies and other ships operating

in good weather with stabilizes inactive

in order to avoid rack and save fuel a

low rate of turn setting during a course

change avoids banking the ship even with

stabilizes inactive in general a low

rate of turn should be used whenever

possible as this has many advantages

seen from a safety economic and comfort

point of view the mathematical formula

for calculation of rate of turn is as

follows

for practical use the formula can be

simplified as follows if we know the

rate of turn

we can rearrange the formula and get the

turn radius exercise calculate the rate

of turn for a ship with speed 20 knots

and the turn radius of 0.5 nautical

miles you can use this calculator by

filling in the numbers in the gray areas

many ships are equipped with auto pilots

capable of following a preset curve

based on turn radius input turning with

a pre-planned fixed radius is

recommended

whenever precision track keeping is

required during a turn the following

points should be taken into account when

planning a turn using a fixed turning

radius use largest possible radius

established the wheel / point as

accurately as possible 121.5 ships

lengths from the start point of the

turning radius is a normal value for

most ships estimate wind current shallow

water if

ex cetera and be prepared to adjust

heading manually whenever necessary