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DESIGN OF WINGS

By

MAYANK

(Reg No. 100933006)

3rd Semester

Department of Aeronautical Engineering

MIT, MANIPAL

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TABLE OF CONTENTS

Title page no

1. Introduction…………………………………………………………………………… 4

2.Study of wing Parameters and its design……………………………………………... . 5

2.1. Number of Wings…………………………………………………………… 5

2.2.Vertical position relative to the fuselage(High, Mid or Low)……………………. 7

2.3. Horizontal position relative to fuselage……………………………………………. 9 2.4. Aerofoil………………………………………………………………………........... 10

2.5. Aspect Ratio………………………………………………………………………... 11 2.6. Taper Ratio…………………………………………………………………………. 15 2.7. wing loading………………………………………………………………………… 18 2.8. MAC…………………………………………………………………………........... 19 2.8. Wing Area…………………………………………………………………………… 22

3. Conclusion……………………………………………………………………………… 23

4. References...................................................................................................................... 24

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ABSTRACT

Aerodynamics is the branch of dynamics concerned with studying the motion of air, particularly when it interacts with a moving object. This project deals with the wing design and the parameters involved in a RC model which in turn helps to study this motion.

This project is majorly concerned with the study, design and implementation of the wing so as to acquire greater lift. The study of the parameters includes the weight, height and length of the RC model of the plane is to be carried out in this project. A great deal of information regarding the lift, drag and weight is studied and understood for the given specifications of RC model. The information achieved is analysed using graphs and presented. The advantages and disadvantages of the models are also discussed.

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CHAPTER 1

INTRODUCTION

What is aerodynamics? The word „AERODYNAMICS‟ comes from two Greek words: aerios, concerning the air, and dynamics, which means force. Aerodynamics is the study of forces and the resulting motion of objects through the air. Judging from the story of Daedalus and Icarus, humans have been interested in aerodynamics and flying for thousands of years, although flying in a heavier-than-air machine has been possible only in the last hundred years. Aerodynamics is the way air moves around things. The rules of aerodynamics explain how an airplane is able to fly. Anything that moves through air reacts to aerodynamics. A rocket blasting off the launch pad and a kite in the sky react to aerodynamics. Aerodynamics even acts on cars, since air flows around cars. The work concentrated in the field of aerodynamics specifies about the wing design in the RC model and also its parameters.The wing gives the major contribution of the lift for an aircraft to fly in the air. These configurations are presented and are available in various open sources such as books, pdf's and online documents. The study of the parameters includes weight, height, length, breadth of a plane is designed with the RC model that helps in improving greater lift, less drag, less weight.The main concern about this RC model is in the study, design and implementation of the wings for greater lift and is discussed along with wing parameters.

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CHAPTER 2

LITERATURE SURVEY

2. Study of wing parameters and its design

2.1. Number of wings

Wing is a part of aircraft,which contributes more lift.There are two types of wings that are studied in this design.

i. Monoplane - Is an aircraft with the one fixed wing.

ii . Biplane - Is an aircraft with two set of wings.

i.Monoplane

The design for the wing is considered much here in the monoplane. The monoplane design has been universally adopted over multiplane configuration because of airflow interference between adjacent wings reduces efficiency.

i(a) Advantages

Fixed wing configuration.

Due to only one set of wings, the drag is less.

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Weight is less, since monoplane has only one wing.

Smooth flow of air around the wing.

Load factor is high.

Small head resistance due to the entire absence of vertical supporting post.

Load distribution is varying according to the section it makes structurally advantage, due to dihedral configuration.

Cost effective as only one set of wings is present.

i(b) Disadvantages

Presence of only one set of wings makes the lift to be comparatively less.

ii. Biplane

An aeroplane having two pairs of wings fixed at different levels, especially one above and one below the fuselage.

ii(a) Advantages

Approximately more than 20% lift generating is achieved by the biplane as compared with that of the monoplane.

Low induced drag.

ii(b) Disadvantages

The increase in drag due to the presence of two set of wings.

The upper wing and the lower wing heavily flow (downwards). It will combine when having trailing edge of the wing. The lower and upper wing drag is thus combined.

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Biplane has a smaller span but larger length when compared to that of a monoplane. Hence the load increases.

iii. Triplane

A triplane is a fixed-wing aircraft equipped with three vertically-stacked wing planes.

iii(a) Disadvantages

Drag is more.

Weight is more.

Maneuverability is less. Pressure distribution is comparatively less and pressure

interaction is more.

2.2. Vertical position relative to the fuselage (High, Mid or Low)

i. Low wing

Low wing is the configuration in which the wing is attached to the lower part of the fuselage.

i(a) Advantages

The landing gear can be placed in the wing. The flow of vortices will not either affect the vertical stabilizer

or the horizontal stabilizer.

The engine mount can be placed over the wing. So the thrust of the engine will not affect the tail portion.

Dihedral angle can be introduced.

It can carry more load as it is directly attached to the fuselage without the help of any truss and struts.

Better advantage of grounding effect.

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Due to equal lift distribution from tip to tip, the speed will be more.

The simple structure provides more manoeuvrability.

i(b) Disadvantages

The interaction between the fuselage and the wing tends to be more.

ii. High Wing

High wing is the configuration in which the wing is attached to the higher portion of the fuselage.

ii (a)Disadvantages

The down wash arising from the trailing edge of all the wings affects the tail portion.

Low banking is achieved.

Low manoeuvrability is present.

Slower than low wing.

It is not more aerobatic.

The presence of vortices makes the tail load to be more.

Leads to poor visibility up and behind the plane.

iii. Mid Wing

The configuration where the wings are connected to the middle part of the fuselage is known as mid wing configuration.

iii(a) Disadvantages

This configuration affects the tail portion.

The presence of mid wing leads to structural disadvantages.

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The bending moment arising from the wing lift must be carried through the fuselage in some manner.

The aircraft structure is heavier, due to the necessity of reinforcing wing root at the intersection with the fuselage.

The mid wing is more expensive compared with high and low wing configuration.

2.3. Horizontal position relative to fuselage

i. Dihedral Angle

When we look at the front view of an aircraft, the angle between the chord-line plane of a wing with the “xy” plane is referred to as the wing dihedral. The chord line plane of the wing is an imaginary plane that is generated by connecting all chord lines across span. For the purpose of aircraft symmetricity, both right and left sections of a wing must have the same dihedral angle. There are several advantages and disadvantages for dihedral angle. In this section, these characteristics are introduced, followed by the design recommendations to determine the dihedral angle.

The purpose of dihedral is to improve the aircraft stability during flight. Dihedral angle is added to the wings for later or rolls stability. When the aircraft encounters a slight roll displacement caused by distribute from air stream or a gust of wind. An aircraft wings with some dihedral will naturally return to its original position.

The front view of this wing shows that the left and right wing do not lie in the same plane but meet at an angle. The aircraft‟s wing is inclined upward an angle from root to tip. The angle that the wing makes with the local horizontal is called the dihedral angle.

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If the wing tip is higher than the xy plane, the angle is called positive dihedral or simply dihedral, but when the wing tip is lower than the xy plane, the angle is called negative dihedral or anhedral.

2.4. Aerofoil

The aerodynamic cross section of a body such as a wing that creates lift as it moves through the air. The shape of airfoil strongly affects the amount of lift.

NAME = NACA 1315-53, #Pts=71, Re=3000000

ReyN = 3000000

AOA Cl Cd Cm

-5

0.008 -0.018 -4 -0.362 0.0078 -0.019 -3 -0.24 0.0075 -0.02 -2 -0.118 0.0072 -0.02 -1 0.005 0.0071 -0.021 0 0.127 0.0068 -0.022 1 0.249 0.0071 -0.023 2 0.371 0.0073 -0.023 3 0.493 0.0071 -0.024 4 0.615 0.0075 -0.025 5 0.736 0.008 -0.026 6 0.858 0.0087 -0.026 7 0.979 0.0098 -0.027 8 1.097 0.0106 -0.028 9 1.191 0.0118 -0.029 10 1.268 0.0129 -0.03

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11 1.329 0.0141 -0.03 12 1.375 0.0162 -0.031 13 1.406 0.018 -0.032 14 1.422 0.0198 -0.033 15 1.423 0.0219 -0.034 16 1.41 0.0242 -0.035

The above plot represents the curve between coefficient of lift (CL) and angle of attack

The above plot represents the curve between the coefficient of drag (CD) and coefficient of lift (CL)

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

-10 -5 0 5 10 15 20

Series1

0

0.005

0.01

0.015

0.02

0.025

0.03

-0.5 0 0.5 1 1.5 2

Cd

Cd

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2.5. Aspect Ratio

Aspect ratio is an indicator of the general performance of an aircraft wing. In aerodynamics, the aspect ratio of a wing is defined as the square of the span divided by the wing chord. It is a measure of how long and slender a wing is from tip to tip. For “high” aspect ratio aircraft wing indicates long, narrow wings, whereas a “low” aspect ratio wing indicates short and stubby. Higher aspect ratio has the effect of a higher rate of lift increase, as angle of attack increases, than lower aspect ratio wings. The wing planform area with a rectangular or straight tapered shape is defined as the span times the mean aerodynamic chord. Thus, the aspect ratio shall be redefined as:

Several rectangular wings with the same platform area but different aspect ratio.

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The designer has infinite options to select the wing geometry. For instance, consider an aircraft whose wing reference area has been determined to be 30. A few design options are as follows:

A rectangular wing with a 30 m span and a 1 m chord (AR =30)2.

A rectangular wing with a 20 m span and a 1.5 m chord (AR =13.333)3.

A rectangular wing with a 15 m span and a 2 m chord (AR = 7.5)4.

A rectangular wing with a 10 m span and a 3 m chord (AR = 3.333)5.

A rectangular wing with a 7.5 m span and a 4 m chord (AR = 1.875)6.

A rectangular wing with a 6 m span and a 5 m chord (AR = 1.2)7.

A rectangular wing with a 3 m span and a 10 m chord (AR = 0.3)8.

A triangular (Delta) wing with a 20 m span and a 3 m root chord (AR = 13.33; here to note that the wing has two sections (left and right))9.

A triangular (Delta) wing with a 10 m span and a 6 m root chord (AR = 3.33)

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2.5.1 Aspect Ratio Affect on the Stall Angle of Attack of RC Airplane

Let us now consider the effect of Aspect ratio on the Stall Angle of Attack of RC Airplanes. Consider the graph below, on the x-axis is Wing Angle of Attack in degrees and on the y-axis is the Wing Lift Coefficient (CL). Lift curve of different RC Airplanes Wings are drawn with increasing Aspect ratio.

Here to note, that the maximum Lift coefficient is considered the same for all the RC Airplanes Wings with different Aspect Ratio. From the graph, we can see that an RC Airplane with small Aspect Ratio stalls at a higher Angle of Attack. On the other hand we can see that when the Aspect Ratio of the RC Airplane Wing is increased the wing stalls at a lower Angle of Attack.

So, from this we can conclude that a wing with a smaller value of Aspect ratio stalls at a higher Angle of Attack and a wing with a higher Aspect Ratio stalls at a lower value of angle of attack. Now, we know that Aspect Ratio is defined as, (Wing Span*Wing Span) / Wing Area or b2/S. When the value of Aspect Ratio is higher, the wing reaches the maximum lift coefficient at a smaller angle of

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attack. Further, increase of the angle of attack will cause the flow separation and the wing will stall. When the aspect ratio is smaller, higher values of angle of attack are required to achieve the maximum lift coefficient and thus the wing stalls at a higher value of Angle of Attack.

Triangular (Delta) wing with a 10 m span and a 6 m root chord (AR = 3.33)

2.6. Taper Ratio

The taper ratio of a wing is simply the tip chord divided by the root chord. High aspect ratio wings with low taper ratio (tip chord much less than root chord) are extremely prone to tip stalls so it is best to avoid using both on the same wing.

If we want a highly tapered wing then we have to contribute the aspect ratio. If we want a high aspect ratio wing then keep the taper ratio closer to 1 (same root and tip chord).

Knowing the taper ratio, aspect ratio and wing area allows you to calculate the root and tip chords assuming the wing does not have multiple tapers. This definition is applied to the wing, as well as the horizontal tail, and the vertical tail.

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The geometric result of taper is a smaller tip chord. In general, the taper ratio varies between zero and one. Three major planform geometries relating to taper ratio are rectangular, trapezoidal and delta shape which are presented. In general, a rectangular wing planform is aerodynamically inefficient, while it has a few advantages, such as performance, cost and ease to manufacture. A wing with a rectangular planform has a larger downwash angle at the tip than at the root. Therefore, the effective angle of attack at the tip is reduced compared with that at the root. Thus, the wing tip will tend to stall later than the root. The spanwise lift distribution is far from elliptical; where it is highly desirable to minimize the induced drag. Hence, one of the reasons to taper the planform is to reduce the induced drag.

In addition, since the tip chord is smaller than root chord, the tip Reynolds number will be lower, as well as a lower tip induced downwash angle. This is undesirable from the viewpoint of lateral

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stability and lateral control. On the other hand, a rectangular wing planform is structurally inefficient, since there is a lot of area outboard, which supports very little lift. Wing taper will help resolve this problem as well.

The above figure shows the wings with various taper ratios

The typical effect of taper ratio on lift distribution

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2.6.1 Elliptical Wing

Elliptical wings are very efficient but difficult to build — particularly elliptical wings having elliptical thickness. Wood doesn't like compound curves. Some designs get around this by adjusting the airfoil (rib height) to create a straight taper in thickness from root to tip which never looks right.

The way to build a wing easily while approaching the efficiency of an elliptical wing is to build a taper wing.

2.7. Wing loading

Weight the model, fully assembled, in ounces. Include all accessories normally used during a flight, such as fuel, batteries, engine and propeller. We should be very careful about the measurement to ensure the math turns out correctly.

Measure the wing dimensions (in inches).

Measure the wingspan (tip to tip) and the chord line (leading edge to trailing edge).

If the wings taper down towards the wingtips, then we should measure an average chord line about halfway from wing-root to wingtip.

Determine the surface area of the model's main wings. For total surface area in square inches, multiply wingspan time‟s chord line.

Surface Area= (Wingspan) x (Chord line)

Divide the RC model's weight by the wing's total surface area to obtain wing loading in ounces per square inch.

(Weight)/(Wing Area)=Wing Loading.

A good wing loading is .15 ounces per square inch, with anything falling between .11 and .20 ounces per square inch being acceptable.

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2.8. MAC

MAC is nothing but the abbreviation for mean aerodynamic chord. MAC can be traced on a wing by using the following steps.

1. Measure the root and tip chord.

Then draw the following lines on the plans:

At the root of the wing, draw a line parallel to the centerline of the fuselage extending forward from the leading edge and

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rearward from the trailing edge. Both lines should be the length of the tip chord.

Do the same thing at the tip but drawing the lines the length of the root chord.

Connect the ends of the lines so that they create an "X" over the wing panel. Where the two lines intersect is the spanwise location of the Mean Aerodynamic Chord.

If the plan indicates that the CG should be located at some percentage of the MAC, then measure the MAC and put the CG the given percentage back from the leading edge along the MAC. For example, if the MAC is 10" and the plan indicates the CG should be 25% back from the leading edge, then the CG is 2-1/2" back from the leading edge at the MAC.

This drawing will help us to visualize what we need to do:

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The lines cross at the spanwise location of the MAC. It is not the fore/aft CG location (unless the CG happens to be located at 50% MAC).

The following formula will give the measurement (chord) of the MAC. It does not give the span wise location of the MAC.

where

rc = Root Chord t = Taper Ratio = (Tip Chord ÷ Root Chord)

MAC = rc x 2/3 x (( 1 + t + t2 ) ÷ ( 1 + t ))

Using the drawing above, let's say the root chord is 11" and the tip chord is 6"

t = 6 ÷ 11 = .5455

Now pluging into the formula to find the MAC. Here the point to note that the wingspan and sweep do not matter. No matter what the span or how much the wing is swept, the MAC will always be the same length.

MAC = 11 x 2/3 x (( 1 + .5455 + .54552 ) ÷ ( 1 + .5455 ))

MAC = 22/3 x ( 1.8431 ÷ 1.5455 )

MAC = 7.3333 x ( 1.8431 ÷ 1.5455)

MAC = 7.3333 x 1.19254

MAC = 8.7453"

My thanks to Alasdair Sutherland, author of Basic Aeronautics for Modelers (Traplet Publications), for providing us with this information.

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2.9 Wing Area

It is better to determine the wing area based on the target wing loading which is based on target weight. For this example we're building a model to weigh 55lbs with a wing loading of 20 oz./ft2. Plug those numbers into the wing loading equation to find the wing area:

Given:

Wing Loading = 20 oz./ft2 Target Weight = 55lbs

Find the Wing Area:

Wing Loading = (Weight x 2304) ÷ Wing Area

Rearrange the equation to find the wing area:

Wing Area = (Weight x 2304) ÷ Wing Loading

Plug in given parameters:

Wing Area = (55 x 2304) ÷ 20

Wing Area = 79.59in2

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CHAPTER 3

CONCLUSION

From the above studies and discussions, the most preferred wing design for a RC plane will be a monoplane, low wing dihedral model. The RC plane should be made monoplane as a monoplane offers less drag and less weight when compared to other models. The dihedral angle model is chosen as it will make the RC plane much more stable. The low wing is preferred in this study over high wing and mid wing because there is not much interference with the landing gear as it is placed on the wing and also the selection of such a low wing model provides a high aspect ratio to the plane. The simple structure of the low wing model helps solving various manoeuvrability problems in the plane. Taper ratio is chosen close to 1 so as to provide a high aspect ratio plane. The studies finally also show how to calculate the best wing area, wing loading and MAC to enable

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CHAPTER 4

REFERENCES

1. John .D. Anderson “Aircraft performance and design” Tata McGraw-Hill Education Edition 2010.

2. Ajoy Kumar Kundu ”Aircraft Design” Cambridge Aerospace series.

3. L.J Clancy,”Aerodynamics. 4. Theodore A. Tally “Introduction to the Aerodynamics of

flight NASA 1975. 5. www.wings.avkids.com/book 6. www.sdsefi.com 7. www.quest-global.com