The Retractable Wing RC Aeroplane

FOLDABLE WING –RC PLANE
AEROMODELLING CLUB IITK

PROJECT MEMBERS
ANKITA MITTAL
JEETESH AGRAWAL
KRATIKA AGRAWAL
PRATEEK SAZAWAL
RAVINDRA DHAMA
VIKAS RANA
ankitami@iitk.ac.in
jeetesh@iitk.ac.in
kratika@iitk.ac.in
sazawal@iitk.ac.in
dhama@iitk.ac.in
ranav@iitk.ac.in

INTRODUCTION
FOLDABLE WING IS A SIMPLE WING WITH
ITS OUTER PARTS FOLDING.IT REQUIRES
SOME SPECIFIC MECHANISM TO FOLD THE
WINGS.IT IS MADE OF BALSA WOOD AND
BALSA PLY AND USED TO GIVE THE PLANE
ITS REQUIRED LIFT.

AIM AND OBJECTIVE
This report is about a remote controlled plane
(RC plane) with foldable wings and this action of
folding will also be remote controlled.
The basic aim behind folding the wings is that it
can be used both as a car and an airplane.
The most important aspect of this kind of plane
is that this can serve as a cheaper version of a
Plane Car.

AIM AND OBJECTIVE
The basic plan would be to make first a simple
RC plane at first with partitions in each wing
then we make use of hinges and springs to make
the wings fold.

DIFFICULTIES FACED

FINDING A SUITABLE PROBLEM
STATEMENT
First of all the problem must be feasible.
Secondly it must give you the maximum chance
to learn.
Keeping these two points in mind we decided to
go for this model.

HOW TO FOLD THE WING
The most challenging aspect of the project is to
find a suitable mechanism to fold the wing.
For this several methods were first tried on the
previous years models available with the club.
Stability of the wing in air was a very critical
issue.

DIFFERENT MECHANISMS TRIED
To fold the wing using a servo alone.
This was not possible since the servo could not
take this much of load.
Then we tried it with a hinge.
The problem here was that of the fact that the
servo might loose control at any time and one can
not be very sure.

DIFFERENT MECHANISMS TRIED
Then keeping these things in mind we decided to
use a rod in combination with the hinge.
In this case we will have to synchronize the
movement of the hinge and the rod.
The rod will provide stability and will give proper
strength.
But, it was a very difficult task to synchronize
the movement of the hinge and the rod.

DIFFERENT MECHANISMS TRIED
So, we finally tried to modify the servo in such a
way that with a small movement of the servo we
could achieve a greater change in the angle by
which the wing moves.
For this we used a piece of ply to make the
Even, fiber glass would have worked well for this
purpose, but due to lack of availability we
couldn’t use it.

MAKING WING
Along with that we were working on the wing.
We needed to use a software DESIGNFOIL to
decide upon the airfoil shape and size.
Once this was done we had to make the wing.
Since our project was a folding wing we had to be
extremely careful while assembling and joining
the different airfoils.

MAKING WING
Thick balsa had to be used at the end of every
segment.
A lot of support was provided to the wing using
stringers.
Keeping in mind the complexities of the wing, we
decided to keep it simple and hence we did not
provided any dihedral angle.

AIRFOIL SPECIFICATIONS
Airfoil name NACA-2515-63
Chord length 26 cm
Angle of attack 3 degrees
Lift 0.667
Drag 0.0079
Lift to drag ratio 84.4
Coefficient of lift 0.667

POSITION OF AILERONS
Generally, in a wing on the trailing edge we
provide with flaps and ailerons.
The flaps are near to the fuselage and the
ailerons are near the wing tips.
This is done so that the ailerons work effectively.
Since the ailerons work on the principle of
torque.

POSITION OF AILERONS
However in our project since the wing is a folding
one so we can not have either flap or aileron on
the part near the wing tip.
Since ailerons are vital to an aircraft’s movement
we placed only ailerons on the wing.
We kept the aileron a bit bigger in our case
keeping in mind that it is placed near the
fuselage ( generally ailerons are kept far from
fuselage so as to produce large torque )

WING SPECIFICATIONS
Wing span = 182 cm
Chord Length = 26 cm
Dihedral angle = 0 degrees
Area of wing = 182*26 cm 2 = 4732 cm 2
Aspect ratio = 7

Length of part 2= Length of part 3 = 45.5 cm
Length of part 1 = Length of part 4 = 45.5 cm

AILERON SPECIFICATIONS
Length of aileron = 40 cm.
Breadth of aileron = 5 cm.
The edges of the aileron were
minimize the drag effect.
rounded to

MAKING TAIL
Once different parts of the wing were made, we
moved on to the tail.
One point to be kept in mind while making the
elevator and rudder is that their area too is to be
included in the area of the tail and vertical
stabilizer respectively.

HORIZONTAL TAIL SPECIFICATIONS
The maximum length between base and its topmost
portion is 14.5 cm.
The minimum distance is 8 cm.
The length of the base is 64.5 cm.
The tail was inclined at a negative angle of 3 degrees
with respect to the fuselage.

VERTICAL STABILIZER
It was made trapezium shaped with the following
specifications.
Height = 29.3cm
Length of two parallel sides were 2 cm and 23
cm.

RUDDER SPECIFICATIONS
Length = 78 cm
Breadth = 7 cm
Its cross section was airfoil shaped so as to minimize
the drag .

FUSELAGE
We went for an simple fuselage design.
Our project was meant to be a high wing plane
since we do not know flying ( high wing planes
have higher stability,so they are recommended
for beginners)
Generally length of a typical fuselage is 70-90%
of the wing span.
In this case it is 82.5%.
Length of fuselage being 150 cm.

FUSELAGE
After making it we made the base.
We used 3 mm ply to make this basic structure of
the fuselage.
Hence, we need to impart strength to the
fuselage at several places.
Depending on the strength needed at several
places we used single or multi layers of 6 mm
balsa wood or ply.

FUSELAGE
In an aircraft reliability is a very important
issue.
Hence the strength of the plane is a very critical
issue and needed to be handled carefully.

FUSELAGE
To maintain the proper aerodynamic shape of the
fuselage several scanners were set in the hind
section of the fuselage.
Between the scanners trusses were made.
Similarly on the base we made trusses.
At some places 6 mm balsa wood was also used to
give strength.

FUSELAGE
Proper strength must be there because it must
not break due to the vibrations of engine.
Also, the part where Landing Gear have to be
mounted must be very strong, so that it can take
up the vibrations at the time of landing.
These parts were made using double layers of 6
mm ply.

FUSELAGE
For the landing gear a similar piece of ply was
attached at the bottom of the fuselage so as to fix
it in its proper place.
And then we tightened it using nuts and bolts.
We used cycle spokes as wires to connect servos
to different parts of the plane like ailerons,
rudder, elevator.
To the rudder also a landing gear was attached to
ensure the proper landing and take off.

FUEL TANK
We used a mixture of methanol and castor oil.
Level of fuel tank must match the oil input valve.

FINDING THE POSITION OF WING
One of the most important thing is to find a
suitable position for the wing.
For if the centre of gravity of the entire system is
not in between the aerodynamic centre and the
tail then the plane will not be stable.
We did not have exact data required for the
calculations.

FINDING THE POSITION OF WING
What we did then was to try to keep the position
of centre of gravity at a distance of 0.1c to 0.2c
from the aerodynamic centre.
Here c is the chord length.
The aerodynamic centre is located at a distance
of 0.25c (approximately) from the leading edge of
the wing for subsonic speeds.

FINDING THE POSITION OF WING
The centre of pressure is the position where
actually the total force vector is located.
But in most of the practical cases aerodynamic
centre is used for calculation purposes.

FIXING WING
The wing is attached to the fuselage with the
help of thin rubber tubes.
With this we can separate the two parts and
change the position of the wing as per the
requirements.
Like we can use a engine of better capacity.
But with that the weight will increase and so the
position of centre of gravity will vary.
So, we will have to readjust the wings position.

FINALLY FLYING…..
We need to use a five channel transmitter as
against the normal four channel transmitter.
Since in our case we have used an additional
servo for folding the wing.

For more information visit our website
http://students.iitk.ac.in/aeromodelling
Contact
Jeetesh Agrawal
Kratika Agrawal
Tushar Sikroria
jeetesh@iitk.ac.in
kratika@iitk.ac.in
sikroria@iitk.ac.in