Development Phase

In the preliminary design stages, various designs were studied and analysed for

their performance in accordance with the problem statement. Design aspects

which were beneficial for one aspect of flight but harmful for some other were

weighted for pros and cons and an ultimate decision was made in order to come

up with the best possible design for the required problem statement.

The monoplane was selected even though the biplane design offers greater

strength. This was because, strength was not the paramount concern as the plane

was supposed to be light and the preliminary designs which were tested using

ANSYS software confirmed that the structure was strong enough for the

purpose. Further biplanes have inherently more drag for a given amount of lift

than monoplanes. Monoplanes are capable of higher speeds and lower energy

consumption.

Markets were surveyed for the availability of construction material as well as

the auxiliary items required to build the plane under a decent budget and of the

desired quality.

Out of the various types of batteries available, the Lithium Polymer (Li-Po)

battery was chosen even though it is more expensive. Li-Po batteries offer the

advantages of lower weight and increased capacity and power delivery.

Management Phase

Organization of the team

Figure1.

Various team members were given the responsibility of various aspects of the

project. They were given these responsibilities along with the authority

necessary to carry out their responsibilities. The person best suited for the

department was chosen democratically and according to their abilities. The

members in each department were also chosen according to their abilities and

keeping in mind their personal choice. Figure1 is a diagrammatic representation

of the team’s organization.

The network analysis diagram in figure 2 clearly shows the time taken in days

in order to complete a specific task. Division of work enabled the work to be

completed quickly as members of each department were able to complete their

own tasks in a short period of time as not much man power was required for any

aspect of the project

Conceptual Design

The problem statement requires us to carry the greatest payload possible over a

specified course. There are various regulations on take-off and flight and some

restrictions on the weight. Therefore, it is imperative to design the aircraft under

such strict conditions. The greater the payload, the more power the airplane

requires which increases the size of the batteries and the motors ultimately

increasing the size of the plane and its weight as well. Therefore, by restricting

the total weight of the airplane there is also an implied restriction on the payload

that can be carried. Better design and manufacture will help us achieve a result

as close to the maximum as possible.

The NACA four-digit wing sections define the profile by

1. First digit describing maximum camber as percentage of the chord.

2. Second digit describing the distance of maximum camber from the airfoil

leading edge in tens of percents of the chord.

3. Last two digits describing maximum thickness of the airfoil as percent of

the chord.

This formula is for the shape of a NACA 00xx foil, with "xx" being replaced by

the percentage of thickness to chord.

where:

c is the chord length,

x is the position along the chord from 0 to c,

y is the half thickness at a given value of x (centerline to surface), and

t is the maximum thickness as a fraction of the chord (so 100 t gives the last

two digits in the NACA 4-digit denomination).

Figure (A)

Various aspects like chord, camber etc. are illustrated in figure (A).

Equation 2

where:

m is the maximum camber (100 m is the first of the four digits),

p is the location of maximum camber (10 p is the second digit in the NACA

xxxx description).

Equation 2 was used as the cambered airfoil offers a number of advantages over

the symmetrical one.

Considered formulas:

1. Ar = Wing span/Chord length

Ar is aspect ratio

2. Wing loading= weight in oz / area in ftsq.

3. Lift=1/2 .rho. v sq.. wing area.coff. of lift

4. Wing planform area= chord length . wingspan( both for upper and lower

wings added)

Preliminary Design

• Various components like wings, fuselage etc. were designed using PTC

wildfire 5.0 (Pro/E).

• The design is according to the norms given in the rulebook.

• The initial design was tested for operational validity using ANSYS.

• Calculations for specifications of the driving and control motors were

done using MotoCalc 8.

The usage of software to design and test a prototype eliminates the need to

construct and test the component time and again thus saving a lot of time and

money both of which can be put to better use. But, the usage of the software

does not completely eliminate the need for models.

Several 1:1 scale models were made for solving the following problems.

• Check the availability of space for components like motor, controls etc.

• Check the dimensions achieved in actual practice.

Figure 3

Figure 3 shows the first prototype which was constructed out of thermocol and

glue. As can be seen, it employed a biplane design which was later discarded in

favour of a monoplane design as the monoplane gave a more satisfactory result

in analysis.

Figure 4.

Figure 4 shows the final model that was constructed which more closely

resembles the final design of the plane

It was constructed after the monoplane was found out to be more advantageous

as compared to the biplane design as per our requirements.

Detail design

After a number of designs on computer softwares and the construction of

models, a design was approved; which was deemed to be the final design.

Manufacturing and fabrication of the design was approved by the team with

valid proof that the design in robust and fit to carry out its function.

WINGS

Figure 5

Figure 5 shows the final design of the wings.

The final wing design has the following specifications;

• Design : NACA 2417 profile

• Material Used: Balsa Wood

• Strength (kPa): 18100 for compression parallel to grain, 4600 for shear

parallel to grain, 1200 or tension perpendicular to grain.

• Justification for selection: Balsa is an ideal material for constructing an

RC plane. This is due to the fact that not only is it light but also has high

strength for its weight. Also, it does not fail easily in bending which is the

type of stress which the wings need to withstand.

Figure 6 CFD analysis of airfoil

Figure 6 shows the successful CFD analysis of the airfoil carried out on

ANSYS.

Figure 7 Modal analysis

Figure7 shows the modal analysis of the wing span on ANSYS. Modal analysis

uses the overall mass and stiffness of a structure to find the various periods at

which it will naturally resonate. These periods of vibration are very important to

note in dynamic systems, as it is imperative that the natural frequency does not

match the frequency of expected vibrations. If a structure's natural frequency

matches the frequency of vibration, the structure may continue to resonate and

experience structural damage.

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Figure 8.

The analysis of the landing gear is important as the landing gear must be able to

withstand the entire weight of the plane while landing. Analysis of the landing

gear in ANSYS reveals that the design is well within the safety required for

operation.

PLANE DESIGN

Figure 9 shows the isometric view of the assembled plane on PRO/E.

Figures 10 and 11 show front view and top view respectively

DIMENSIONS

• Wing Span: 100 cm

• Length: 75cm

• Chord Length: 14.5

• Propeller: 9’’.

ELECTRICALS

Figure 12 Motor Specifications

Figure 12 shows the result for the motors to be used as indicated by the design

software MotoCalc. Using this information the driving and control motors were

selected from the ones available in the market.

Motor: 1800rpm/V; 0.2A no-load; 0.056 Ohms.

Battery: 1800mAh @ 3 cell 11.1V; 0.0257 Ohms/cell.

Speed Control: Generic Brushless ESC; 4 controls (separate); 0.006 Ohms;

High rate.

Figure 13

Figure 13 shows the controller used for flying the plane. It is a 4 channel

controller. The receiver that is used along with this controller is shown in figure

14.

Figure 14

The Lithium Polymer battery used is shown in figure 15.

Figure 15

Figure 16

Figure 16 shows a micro servo motor. Servo motors are used for control

mechanisms. Their capacities in accordance with the values calculated for a

satisfactory performance.

Manufacturing Process

Once the design was complete and the models were analysed and the team

members were satisfied that the design is up to the mark, the manufacturing

process was started.

The wing airfoil was made of balsa and bonded together in pairs in order to give

greater strength. The manufactured wing is shown in figure 17.

Figure 17

Such intermittent construction allows us to reduce the weight of the wings and

still maintain the shape and strength required for flight. A single airfoil is of the

shape shown in figure 18.

Figure 18

Figure 19

Figure 19 shows the fuselage of the plane. It has been constructed out of

chloroplast and has been bonded using super glue. Super glue was selected after

carefully analyzing the pros and cons of several bonding materials available.

The pros and cons are listed in table 1. Super glue was selected as it was easily

available and was the best option for bonding several components as the entire

airplane is not made of a single substance but is a composite of several

components.

Table 1

Figure 20

Figure 21

Figure 20 illustrates the push rod mechanism employed to control the motion of

the airplane. Figure 21 shows specifically the aileron control. The links are

fixed in such a way that they coincide with the zero position of the motor when

in the neutral position. This enables the controller to move the controls in either

direction easily and bringing it back to the mean position is a fairly simple task.

CONCLUSION

A safe and reliable design approach was adapted. Extensive testing has been

done including the gliding capabilities of the models constructed and static

analysis of the model we are ready with the final design and the airplane is

approaching completion. All is left to do is the flight analysis and test the limits

of the airplane so that the plane which we put forth to compete is capable of

competing with the other teams.