Determine Wheel Over Point (WOP): 3 Methods for Accurate Ship Turns ll Rate of Turn (ROT)

Summary

This video provides a detailed guide on how to manually determine the wheel over point for altering a ship's course. It covers three different methods, starting with using an arc centered on a reference point like a lighthouse, followed by using parallel index lines without a reference point, and finally, a calculation-based approach. Each method is explained with step-by-step instructions, ensuring precise navigation and avoiding overshooting or undershooting the intended course. The video is useful for mariners needing to manually plan course changes, emphasizing safety and accuracy.

Takeaways

• 📍 **Wheel Over Point:** The specific point along the planned track where the helm must be executed to alter the ship's course to the next intended direction.
• ⚓ **Purpose:** Ensures the ship begins its turn at the right moment to achieve the desired new course without overshooting or undershooting the target.
• 🛳️ **Factors Considered:** Ship speed, turning radius, rate of turn, and the angle of the intended course change are crucial in determining the wheel over point.
• 📏 **Method 1:** Plot an arc or circle with the lighthouse at the center and a radius of one nautical mile. This helps to maintain the desired distance while turning.
• 🧭 **Turning Point:** Draw a perpendicular line from the lighthouse to the planned track to find the turning point where the ship starts to turn.
• 📐 **Method 2:** Use parallel index lines on both tracks with the chosen radius to determine the wheel over point without a fixed reference point.
• 📝 **Calculation:** Find the course difference, ship's rate of turn, time run, distance run, and reaction distance to calculate the wheel over point accurately.
• ⚙️ **Rate of Turn:** Determined by dividing the ship's speed by the turning radius, providing a rate in degrees per minute.
• ⏱️ **Time Run:** The time it takes for the ship to turn from the turning point to the end of the turn, calculated by dividing the course difference by the rate of turn.
• 🔍 **Distance Run:** The distance the ship travels during the turn, found by multiplying the ship's speed by the time run.
• 🗺️ **Reaction Distance:** Distance from the waypoint to the turning point, helping to pinpoint the exact wheel over point location.

Q & A

What is the 'wheel over point' in ship navigation?

The 'wheel over point' is the specific point along the planned track where the ship's helm must be executed to alter the ship's course to the next intended direction. It ensures that the ship begins its turn at the right moment to achieve the desired new course without overshooting or undershooting the target.

What factors need to be considered when determining the wheel over point?

The factors to consider when determining the wheel over point are the ship's speed, turning radius, rate of turn, and the angle of the intended course change.

How does one determine the wheel over point using the first method described?

In the first method, an arc or circle is drawn with the lighthouse at the center and a radius of one nautical mile. The planned route is then transferred along this arc. The wheel over point is found by measuring a distance of one ship's length backward from the turning point along the planned track.

What is the significance of the turning point in the process of altering a ship's course?

The turning point is the location along the planned track where the ship starts to respond to the helm execution and physically begins to turn. This point is crucial in determining when to execute the turn to achieve the desired course alteration.

Why is it important to account for the ship's length when determining the wheel over point?

Accounting for the ship's length is important because it takes time for the rudder to react before the ship starts to turn. Therefore, an allowance of about one ship's length is given to ensure that the turn begins at the right moment.

What is the second method for determining the wheel over point, and how does it differ from the first method?

The second method involves drawing parallel index lines on both tracks at a chosen radius. The intersection of these lines serves as a reference point. The wheel over point is then determined by measuring one ship's length backward from the turning point along the initial planned track. This method differs from the first in that it does not require a fixed reference point like a lighthouse.

How is the ship's rate of turn calculated?

The ship's rate of turn is calculated by dividing the ship's speed by the turning radius. The result gives the rate of turn in degrees per minute, which indicates how quickly the ship can change its course.

What is the purpose of calculating the time run and distance run in the third method?

The time run is the time it takes for the ship to complete the turn, while the distance run is the distance traveled by the ship during the turn. These calculations help determine the reaction distance and the exact location of the turning point, which are essential for accurately finding the wheel over point.

Why might the third method be particularly useful when communicating with port authorities?

The third method, which involves calculations based on the ship's speed, turning radius, and rate of turn, is useful for providing precise and detailed information. This can be helpful when discussing navigational details with port authorities or when precise documentation is required.

How do the three methods compare in terms of determining the wheel over point?

All three methods ultimately lead to the same location of the wheel over point. The first method uses a fixed reference point like a lighthouse, the second method uses parallel index lines without a fixed reference point, and the third method involves detailed calculations. Despite their differences, they all yield consistent results.

Outlines

00:00

⚓ Understanding the Wheel Over Point

The first paragraph introduces the concept of the wheel over point, which is crucial for altering a ship's course accurately. It explains the purpose of the wheel over point, emphasizing its role in ensuring the ship turns at the correct moment to achieve the desired course without deviation. Key factors such as ship speed, turning radius, rate of turn, and course change angle are considered. The paragraph also mentions that the wheel over point can be determined manually or with an Electronic Chart Display and Information System (ECDIS), and the video will demonstrate the manual method.

05:02

🧭 Method 1: Plotting the Wheel Over Point Using a Lighthouse

The second paragraph details the first method of determining the wheel over point, using a plotted arc with a lighthouse as the reference point. The method involves measuring distances using the latitude scale, transferring the planned route along the arc, and identifying the turning point where the ship starts to turn. The wheel over point is calculated by measuring a distance equivalent to the ship's length in nautical miles before the turning point. This method serves as a guide, with a recommendation to refer to the ship's safety management system for specific procedures.

10:03

📏 Method 2: Using Parallel Index Lines for Wheel Over Point

In the third paragraph, the second method for determining the wheel over point is discussed, using parallel index lines. These lines are drawn on both tracks with the distance between them equal to the chosen turning radius. The intersection of these lines serves as the reference point, similar to a lighthouse in the first method. The turning point is identified by drawing perpendicular lines from the reference point to the planned track. The wheel over point is then calculated by measuring the ship's length in nautical miles backward from the turning point along the initial track. This method is compared with the first, showing that both yield the same result.

📐 Method 3: Calculating the Wheel Over Point

The final paragraph describes the third method, which involves calculating the wheel over point using a mathematical approach. The method begins by determining the course difference between the initial and final courses, followed by calculating the ship's rate of turn using speed and radius. The time taken for the turn and the distance run during the turn are then computed. The reaction distance, or the distance from the waypoint to the turning point, is found by dividing the distance run by two. Finally, the wheel over point is determined by measuring the ship's length in nautical miles backward from the turning point along the initial track. The paragraph concludes by confirming that all three methods produce the same wheel over point.

Keywords

💡Wheel Over Point

The Wheel Over Point is the specific location along a ship's planned track where the helm must be executed to alter the ship's course to the next intended direction. This point ensures that the ship begins its turn at the correct moment to avoid overshooting or undershooting the desired new course. It is crucial in precise navigation to maintain a safe and efficient route.

💡Turning Point

The Turning Point is the location along the planned track where the ship physically starts to turn in response to the executed helm. It is determined based on the intersection of a perpendicular line drawn from a reference point, such as a lighthouse, to the planned track. The Turning Point is distinct from the Wheel Over Point, which is located slightly before it.

💡Planned Track

The Planned Track refers to the intended route that a ship is expected to follow during its voyage. It includes various waypoints and course changes that guide the ship from its origin to its destination. The accuracy of the planned track is vital for safe navigation, and adjustments may be necessary based on real-time conditions or instructions from the captain.

💡Radius

In navigation, the Radius refers to the distance from the center of a turning circle to the path the ship follows during a turn. It is a key factor in determining the Wheel Over Point, as it influences the ship's turning characteristics. The radius is chosen based on the ship's size, maneuvering capabilities, and the desired course change.

💡Rate of Turn

The Rate of Turn is the speed at which a ship changes its direction, measured in degrees per minute. It is calculated by dividing the ship's speed by the turning radius. The rate of turn is crucial for determining how long it will take the ship to complete a course change and is used to calculate the distance traveled during the turn.

💡Reaction Distance

Reaction Distance is the distance from the waypoint to the Turning Point, representing how far the ship travels before it begins to respond to the executed helm and starts to turn. It is calculated as half the distance the ship travels during the turn and is essential for precise navigation.

💡Helm

The Helm refers to the ship's steering mechanism, typically controlled by a wheel, which is used to change the ship's direction. Executing the helm involves turning the wheel to adjust the rudder, causing the ship to turn. The correct timing and execution of the helm are critical for navigating the planned track and reaching the Wheel Over Point effectively.

💡Nautical Mile

A Nautical Mile is a unit of measurement used in maritime and aviation navigation, equivalent to 1,852 meters. It is based on the Earth's circumference and is commonly used to measure distances at sea. In the video, nautical miles are used to calculate distances, such as the ship's length and the radius of the turning circle.

💡Perpendicular Line

A Perpendicular Line in navigation is a straight line drawn at a right angle to the planned track or another reference line. In the video, perpendicular lines are used to identify the Turning Point by intersecting the planned track at the exact location where the ship should begin its turn.

💡Lighthouse

A Lighthouse is a tall structure, typically located on a coast or island, that emits a light to guide ships safely at sea. In the video, the lighthouse serves as a reference point for plotting the ship's course and determining the Wheel Over Point. The ship must maintain a safe distance from the lighthouse while turning to avoid hazards.

Highlights

Explanation of the wheel over point as the specific location on the track where the helm must be executed to change the ship's course.

Discussion on the importance of determining the wheel over point to avoid overshooting or undershooting the intended course.

Factors affecting the wheel over point: ship speed, turning radius, rate of turn, and the angle of the intended course change.

Introduction of three different methods to manually determine the wheel over point, starting with a method involving plotting an arc or circle with the lighthouse at the center.

Method 1: Using the latitude scale to measure distance and draw an arc for the ship to follow when altering course.

Explanation of how to transfer the previously planned route along the arc to maintain a 1 nautical mile distance from the lighthouse.

Detailed steps on finding the turning point and determining the wheel over point by measuring the ship's length in nautical miles.

Method 2: Using parallel index lines and a reference point without needing a physical landmark like a lighthouse.

Comparison of Method 1 and Method 2, showing that both methods lead to the same wheel over point, whether a fixed reference point is available or not.

Introduction of Method 3, which involves more calculation and might be useful when discussing with port authorities.

Step-by-step guide on calculating the course difference, rate of turn, and time run in Method 3.

Explanation of how to determine the reaction distance and distance run during the turn in Method 3.

Demonstration that all three methods result in the same location for the wheel over point.

Emphasis on checking the pilot card for the ship's maneuvering characteristics when selecting the desired radius during course alteration.

Final reminder to refer to the company's safety management system (SMS) manual for official procedures on determining the wheel over point.

Transcripts

wheel over point is the specific point

along the plan track where the helm must

be executed to alter the ship's course

to the next intended

Direction the purpose of wheel overo is

to ensure that the ship begins its turn

at the right moment to achieve the

desired new course without overshooting

or undershooting the target there are

factors to be considered to determine

the wheel over Point those are the ship

speed turning radius rate of turn and

the angle of the intended course change

this might be easy if you are using an

ectis in making a passage plan but in

today's video I will show you how to

determine the wheel over Point

manually assuming that this is your

planned route when a beam of cura point

the ship will alter course 050 ° with an

approaching course of 350°

true you've been advised by the captain

to move the plan track closer to a

lighthouse and maintain a distance of 1

nautical mile from the lighthouse while

the ship is turning to the next course

then determine the wheel over

point the ship's length overall is 280 M

with an average speed of 12

knots this video shows three different

methods on how to determine the wheel

over

point the first method is to plot an arc

or a circle where the lighthouse is at

the center with a radius of one nautical

mile the actual position of the

lighthouse is marked with a small small

circle at the base of the

symbol use the latitude scale to measure

the

distance as we know 1 minute of an arc

in the latitude scale is equal to 1

nautical

mile this latitude scale May differ from

the actual chart it is just made for the

purpose of this

video this Arc will be the track to be

followed by the ship when altering

course from 350° to 050 ° true in order

to maintain a one nautical distance

while turning to the next

course we will now transfer the

previously planned route along the

ark both tracks should be touching the

edge of the drawn

Arc we have now a clear view of where

the ship starts to turn and to where it

ends but we need to determine the exact

point draw a line from the

lighthouse this line should be

perpendicular to the plan track do this

on both

tracks this point where the

perpendicular line intersects with the

plan track is the turning point or

transfer

point this point along the plan track is

where the ship starts to respond from

the executed Helm and physically begins

to turn this point is not a wheel over

point on the other side where the

perpendicular line intersects with the

plan track is the point where the ship

ends its turn and continues to its new

course the wheel over Point can be found

about a ship's length before the turning

point so if the ship's length is 280 M

we need to convert it into a nautical

mile so that we can use the latitude

scale to measure 280 M before the

turning point to convert it 280 /

1,852 we divide it by 1852 because one

nautical mile is equal to

1,852

M the ship's length in nautical mile is

0.151 use the latitude scale to measure

0.151 this distance is

0.151 as shown on the

scale measured the distance from the

turning point along the plan

track this point is now our wheel over

point in this scenario when we reach the

wheel over point point we will execute

Helm to

starboard for bigger ships it takes time

for a Rudder to react before the ship

will start to turn so we give an

allowance of about a ship

length this method serves only as a

guide if you are on board kindly refer

to the company's safety management

system or SMS manual on how to determine

the wheel over

Point How about if there is no reference

point how can we determine our will over

point

this is the second method I will discuss

in this video on how to determine the

wheel over

point I will use the same length overall

speed radius and the plan tracked on the

same spot so that we can compare this

later on from the first

method first draw parallel index lines

on both

tracks these lines should be in the

inner part of the

turn the distance should be the chosen

radius in this scenario our radius is 1

nautical

mile for a smaller ship you can use a

smaller

radius for a much bigger ship you can

use a radius greater than 1

mile kindly check the maneuvering

characteristics of your ship on board

including the turning

radius once the parallel lines are

drawn the intersection of these line

serves as your reference point just like

a lighthouse in the previous

method if we draw an arc or a circle

with one nautical mile radius where the

intersection of the parallel index lines

will be at the center this is what it

looks like but I will not use this Arc

in this method assuming that you do not

have a compass divider on hand so let us

take it

out next we will determine the Turning

Point draw a perpendicular line on the

plan track intersecting the assumed

reference point which is the

intersection of the two parallel index

lines do this on both

tracks this point where the

perpendicular line intersects with the

initial track is the turning

point this is the point where the ship

starts to turn if the helm is executed

at the wheel over

point on the other side where the

perpendicular line intersects at the

plan track is the the point where the

ship ends her turn and proceeds to her

new

course the distance from this point to

this point is called reaction

distance the wheel over Point can be

found about a ship's length before the

Turning

Point the ship's length in nautical mile

is

0.151 so measure

0.151 nautical mile from the Turning

Point going backward along the initial

plan track

this point will be our willover

Point upon reaching this point execute

Helm to starboard the ship will start to

turn when she arrives at the Turning

Point let us compare this method to the

first method I have previously

discussed the two parallel index lines

intersect at the Lighthouse position

which serves as our reference point in

the second

method the turning point is at the same

spot as with the previous method so as

with the the wheel over point so whether

we have a fixed reference point or none

we can still determine our wheel over

Point manually based on our preferred

radius using the two parallel index

lines but kindly check the pilot card on

board for the maneuvering

characteristics of your ship so that you

can choose the desired radius during the

course

alteration the third method is more on

calculation this method might be useful

if you've been asked by some Port

Authorities

you can discuss it with him even on a

piece of paper I will use the same given

from the previous method with the same

plan track so that we can compare it

with the previous

method first we need to find the

difference between the initial and final

course the final course is 050 ° minus

the initial course which is

350° the course difference is 0

60° before you can subtract these two

add 3 60° to 050

° so we have now 410 -

350 the difference is

060 next we will find the ship's rate of

turn the formula is ship speed divided

by

radius the given speed is 12 knots but

remember that when the ship turns the

speed

reduces we will assume that that during

the turn the ship's average speed is 10

knots divided by the radius which is 1

nautical mile the rate of turn is 10°

per

minute supposed to be the rate of turn

is 10 hours if we examine the existing

units to convert it into degrees per

minute multiply it by 180 / Pi the value

of 180 / Pi is

57.3 so we have 10 hours *

57.3 to convert hours into minute we

will divide it by 60 since 1 hour is

equal to 60

minutes but usually we do not do this

procedure because if we look at the

value of 57.3 and the divisor which is

60 we can both cancel these

values the slight difference in the

value if we go through the procedure is

negligible when we are in the actual

maneuvering so just divide the ship

speed and the desired radius will give

you a rate of turn and the unit is in

degrees per minute I will make a

separate video with a detailed

explanation of how to determine a rate

of turn in this illustration we just

draw an arc assuming this is the ship's

track during the

turn this calculation will lead to the

exact location of the Turning

Point next we will determine how long it

takes for a ship to turn from the

turning point and until the end of the

turn known as the time run we will just

divide the course difference and the

rate of

turn so 60 / 10 the time run is 6

minutes or 0.1

hour we need to convert it into an hour

because we need it later on to convert

into an hour divide 6 minutes by 60

since in 1 hour is equal to 60

Minutes next we will determine the

distance traveled by the ship from the

point she starts to turn until the turn

ends known as distance run distance run

is equal to ship speed which is 12 mph

times the time run which is 0.1 hour the

distance run during the turn is 1.2

mil next we will determine the reaction

distance this distance is from the

Waypoint to the Turning

Point reaction distance is equal to

distance run divided by two which is

equal to 0.6

mile now measure 0.6 mile from Waypoint

to both sides of the

track this point now will be your

turning

point and on the other side this is the

point where the turn

ends use the given speed in calculating

the distance run which is 12 knots

because we will be measuring the

distance along the Waypoint not along

the Turning

Circle to determine the wheel over over

point we will use the ship's

length from the turning point measure

0.151 nautical mile going backward along

the initial

track this point is the wheel over point

if we check the reaction distance in our

previous method it is also 0.6 nautical

mile these three methods give the same

location of the wheel over Point that's

all for now I hope you find this video

helpful thank thank you for watching bye