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Design and Development of Hexa-copter for Environmental Research
Conference Paper · April 2015
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Suman Pathak
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2. Design and Development of Hexa-copter for Environmental Research
S. Bhandari1
, S. Pathak1
, R. Poudel1
, R. K. Maskey2
, P. L. Shrestha1
and Binaya Baidar1
1 Department of Mechanical Engineering,
2 Department of Civil and Geomatics Engineering
School of Engineering, Kathmandu University, Dhulikhel,
Phone: +977-011-663736, Fax: +977-011- 661443
Email: pth.saurav010@gmail.com, sjnbhandari12@gmail.com and poudel.ravi@yahoo.com,
rmaskey@ku.edu.np
Abstract
UAV (Unmanned Aerial Vehicle) is a flying robot capable of flying without on board pilot. It is
controlled either manually or autonomously. It is an emerging new technology for developing countries
like Nepal and could be applied for environmental research applications like aerial surveillance,
photogrammetry, delivery of medicine, conservation surveillance and many more. Use of big manned
helicopters and other aerial vehicles could be replaced for some applications by UAV’s making those
applications really cheap and accessible. This would definitely be advantageous when being concerned
about economy and risk of operation of the aerial vehicles. For the purposes like disaster scouting,
supplying medical aids and extreme rescue operations, UAVs could prove themselves far worthy and
economical than its counterpart. There are many different types and designs (Multirotors and fixed wings)
of UAVs available in the global market but not easily available in the context of Nepal. The UAV
designed and developed at Kathmandu University is called as KU-COPTER, which is a multirotor with
six propellers (technically called as hexa-copter). It can vertically take-off and land with the purpose to
take aerial surveillance and supply of medical aids. Since the scope of Unmanned Aerial Vehicle (UAV)
is wide, so its development will pave a path for the university in exploring various applications in the
context of developing countries like Nepal. Its indigenous design and development provide the basis for
further modification and features addition according to the area of application.
Keywords: Unmanned Aerial Vehicle (UAV), emerging technology, surveillance, disaster management,
photogrammetric applications.
1. Introduction
Unmanned Aerial Vehicle (UAV) is a type of aircraft which has no pilot or passenger on board. UAVs
include both autonomously controlled (drones) and remotely piloted vehicles (RPVs) controlled via Radio
transmitter. UAVs are commonly used in situations where there is high risk in sending a human piloted
aircraft or where using a manned aircraft is impractical. One of the early practices of UAVs was the
“aerial torpedoes”, designed and built during World War I. The history of multirotor aerial vehicle dates
back to late 1920s and was known as Gyrocopters with four rotors. These were primitive UAVs, relying
on mechanical gyroscopes to maintain straight and level flight, and flying until they ran out of fuel. Later,
due to the complications in control part and workload for pilot it was replaced by an aircraft with single
rotor which is known as helicopter today. But, multirotor UAV have once again gained popularity among
us due to its multiple application and structural integrity with perfect stability.
More advanced UAVs used radio technology for controlled flight. Then the invention of integrated circuit
led to UAVs that can be controlled via electronic autopilots. Modern UAVs are controlled with both

3. autopilots, and manual controllers. This allows them to fly long, safe flights under their own control, and
fly under the command of a human pilot during complicated phases of the mission.
A multirotor UAV is an aircraft heavier than air, capable of vertical take-off and landing (VTOL), which
is propelled by rotors with propellers, positioned in the same plane, parallel to the ground. The number of
propellers in multirotor generally available are three (Tricopter), four (Quadcopter), six (Hexa-copter) and
eight (Octacopter). The size of the multirotor UAV produced ranges from a simple CD to more than a
meter in diameter. Unlike, standard helicopters, a multi coper use fixed-pitch blades in its rotors and its
motion through the air is achieved by varying the relative speed of each propeller.
1.1 Applications
Its ability of VTOL and hover in the position with proper stability and manoeuvrability brings many
mission options into possibilities. This makes the Unmanned Aerial Vehicle (UAV) versatile and may be
used for various purposes. Few application areas are described here:
 Aerial surveillance:
UAV these days are widely used for aerial surveillance. Aerial surveillance drones includes conservation
drones mostly used for wildlife conservation. It is also used by different organisation like military forums
for aerial surveillance for their specific purpose.
 Photogrammetry:
Different organisations use this vehicle for photogrammetric purpose where the high resolution aerial
images taken by the UAV is used for generating 3D images of the landscapes and generate maps.
 Delivery robot:
These days different companies are using UAV as their delivery Kit or robot. Domino’s Pizza uses its
Domocopter (Oct-copter) for delivering Pizza to its customers.
 Precision farming:
Developed countries are using this vehicle for precision farming where the crops are continuously
inspected and the corresponding action are taken for greater productivity.
 Rescue missions:
This vehicle could also be used for rescue purpose and delivering medicine kit for casualties where
manned vehicle is riskier to take.
2. Project Design and Development
Due to wide area of mission possibilities of UAV in various sectors its demand has been increasing day
by day. This has led to commercial development of parts and components of UAV in developed countries.
Meanwhile for developing countries, the idea of UAV is still in emerging phase. So the development and
commercial production of UAV and all of its components has not yet been widely practiced. That is why
our focus for the design and development of hexa-copter has been limited to the design of the frame and
selection of appropriate and economic material for the manufacture of the frame. By assembling the off-
the-self electronic components, available in the market at affordable price, on the frame designed and
developed by us, we have been able to develop a fully functioning hexa-copter.

4. 2.1 Design
We have designed the frame for the aircraft by incorporating the logo of Kathmandu University. The logo
of Kathmandu University led to the idea of developing the hexa-copter by producing six arms from the
six vertices of two triangles present in the logo of KU. Hence the name KU-Copter has been given to the
hexa-copter.
Figure 1 Bottom view of the design of the hexa-copter frame
2.2 Material selection via simulation
Selection of material has to be such that it satisfies the demand of the Hexa-copter frame i.e. material
must be light weight and economic. The most commonly used material for commercial drones is carbon
fibre which is extremely light and extraordinarily strong making it cost very high too. In order to develop
a frame from the appropriate material available at our market in relatively low price, we had to select
between Aluminium Composite Panel (ACP) and PVC Foam (Foam Board). Both the materials were
found to be light weight and rigid which were the basic criteria for the development of frame.
The PVC Foam (Foam Board) available was of thickness 18 mm and ACP was of 4 mm.We had to select
the material that is strong, light and economic. Experimentally, we found that 18 mm Foam board is
heavier than 4 mm ACP but we were not sure about strength of 4 mm ACP. We also had another option
which was to sandwich 2 ACP sheets which was found to be slightly heavier than foam board and a little
more expensive but it seemed to be stronger than foam board. Table 1 shows the comparison of weight of
ACP and Foam board frames.
Table 1 Material thickness and mass
Material Thickness(mm) Mass(gm)
ACP single layered 4 155
ACP Double layered 8 310
Foam board 18 256
2.3 Simulation Setup
We had to optimize the design of the frame and select the best material. This was done using the
Simulation tool Mechanical APDL where we conducted the static structural simulation provided
boundary conditions via experimental measurements and references, the objective being to observe the
maximum stress concentration in various designs and optimize using the simulated result. Firstly, we
were focused on frame manufacture using foam board because it was very light and economic and seemed

5. to be strong enough. So, we designed two foam board frames in solid works; one with slots in the arms
and another without slots.
The created CAD files of the two designs were imported in Ansys for simulation using Mechanical
APDL. We conducted static structural simulation of those frames. The designs were separately simulated
to solve for the maximum deformation and maximum stress on the frame. Material Database was created
for Polyisocyanurate Foam in Ansys Engineering Database. We used patch confirming method with
tetrahedral mesh for the modelling. Mathematical modelling was program controlled by mechanical
APDL.
Figure 2 Tetrahedral mesh created in applied geometry
The boundary conditions were defined as per the values obtained from measurements of weight and other
material properties. Faces where boundary values needed to be provided were split in solid works and
boundary values were provided and parameterized, and we were able to observe results in different
boundary conditions and the results were interpreted accordingly. Boundary conditions applied were
equal in both the designs and the results were compared at similar conditions.
Figure 3 Applied boundary conditions

6. 2.4 Post Processing
After defining the boundary conditions and meshing, we ran simulations in the two designs to obtain
equivalent von-misses stress or maximum stress on the frames along with total deformation. We
parameterized the equivalent stress and forces applied on the faces where motors are placed. Maximum
stress in the frame was to be compared with yield strength of material. Figure 4 and Figure 5 show
maximum stress on the frame and the graphs produced show relation between force and maximum
equivalent stress on foam board frame without and with slots respectively. At static conditions the load
applied are in the direction of gravitational force but when the hexa-copter takes VTOL than the load
applied are in the direction opposite to the gravitational force so the forces in the graph are in increasing
order in the negative direction from that of static condition.
Figure 4: Von- Mises stress on foam board frame without slot
Figure 5: Total deformation in foam board frame with slot

7. 2.5 Assembly and Analysis
After the completion of frame manufacture, we assembled all the electronic components required as
shown in Table 2. Analysis of the frame was done on the basis of equivalent stress and total deformation
on the frames in static condition and their relationship on increase of applied force in the direction
opposite to that of static condition. We created five different data points for force and plotted it against
the deformation and equivalent stress to observe the behaviour of the frame on increased load.
Table 2 Collected materials
COMPONENTS SPECIFICATION
Propeller 8 inch Plastic Propellers
Motor Brushless D.C 935 KV motor
Flight Controller NAZA M-lite flight controller
Electronic speed controller(ESC) 30 Ah ESC for 935 KV Motor
Radio transmitter Radio Control transmitter with six channels
Battery 3 cell Li-Po battery
Estimated time of flight: 8 min for Foam board frame
6 min for ACP frame
Charger 3 cell battery charger
Power distribution Board
Bullet connectors
M3 nuts and bolts
From the simulation result and graphs the stress concentration at static condition is found to be greater in
the design with slot i.e. 0.834 MPa than the design without slot i.e. 0.588 MPa. But the maximum
deformation was close in both the cases i.e. 0.0007 m. Since the materials of both the design are same so
the behaviour was found to be same in both the design. The value of the maximum stress corresponding
to the force applied in negative direction was found to be decreasing first and again starts to increase.
3. Result and Discussion
The stress concentration at static condition is low in both the cases but among the two, the design with the
slot has higher stress concentration. We have advantage of around 50 gm weight on providing the slots
but we have to compromise on strength of the frame.
From this analysis, we manufactured the foam board frame with slots in the arms. But after manufacture
and assembly the foam board frame was found to be quite brittle although being strong and very light.
During piloting practice, the hexa-copter suffered few crashes and the frame broke (Figure 6).
Figure 6: Broken Foam board frame after crash

8. Later we decided to manufacture frame with the ACP (Aluminium Composite Panel) sheet. Since the
ACP sheet was only 4 mm thick we decided to sandwich two ACP sheets and manufactured the frame
with sandwiched ACP of 8 mm thickness. ACP frame was found to be quite strong. Even though it also
suffered some crashes, it didn’t break easily. Rather it bent to some degree which could be straightened
using bench vice. The ACP frame is still functional.
Figure 8: Assembly on ACP frame
Figure 7 presents the first test flight of KU-Copter mounted on foam board frame, which proved to be
fragile against impact. Later the KU-Copter was assembled on ACP frame as shown in Figure 8. The final
version of KU-Copter was tested and demonstrated at several public occasions (Figure 9) and Figure 10
shows the snapshot taken from KU-Copter.
4. Conclusion
The application areas of multirotor UAVs have been increasing day by day all around the world. There
are prospects of such new and emerging technology in Asia and Asia pacific region for socio-economic
development. For developing countries, employing helicopters and other large aircrafts for different
purposes like surveillance, rescue mission, etc. is a challenge from the economic point of view. Similarly,
such missions also involve great risk of human lives. As an alternative, the developed KU-Copter using
the frame locally made of ACP and off-the-shelf purchased electronic parts is very stable, robust, easy to
operate and maintained. After a number of successful test flights and public demonstrations, it is now
fully functional and ready to take off the payload for different application as mentioned above.
Figure 10: Snapshot from KU-Copter
Figure 7: Test flight of KU-Copter on Foam Board
Figure 9: Public demonstration of KU-Copter

9. 5. Acknowledgement
The project team is immensely grateful to the supervisor for his continuous guidance, support and help in
every phase of the project and for funding this project as well. The team is immensely grateful to School
of Engineering of Kathmandu University for providing a platform to design and develop the Hexa-copter.
It extends its gratitude to Centre for Excellence in Production and Transportation of Electrical Energy
(CEPTE), Department of Mechanical Engineering and Department of Electrical Engineering for
providing necessary equipment to test the performance of Hexa-copter. The team would also like to
acknowledge the authors of the reference materials that have been used here.
6. References
[1] S. Bhandari, S. Pathak, R. Poudel “A report on Design and Development of Hexa-copter (KU-copter)”
[2] Dupuis, M & Gibbons, J. (2008). Design optimization of quadcopter capable of autonomous flight.
Worcester polytechnic Institute. Retrieved August 8, 2014
[3] DiCesare, A. Design Optimization of a Quad-Rotor Capable of Autonomous Flight. Worcester
Polytechnic Institute.
[4]Fogelberg, J. 2013. Navigation and Autonomous Control of a Hexa-copter in Indoor Environments.
Lund University
7. Biographies
Sujan Bhandari was born on 27 June 1993 in Charikot, Dolakha, Nepal. He is currently studying Mechanical Engineering at
Kathmandu University.
His current research interest is UAV, its features, control system and application prospects in the context of our country, Nepal
Saurav Pathak was born on 22 May 1994 in Butwal, Nepal. He is currently studying Mechanical Engineering at Kathmandu
University.
His current research interest is UAV, its mathematical modelling and simulation of frame designs.
Ravi Poudel was born on 5 April 1991in Butwal, Nepal. He is currently studying Mechanical Engineering at Kathmandu
University. His current research interest is UAV, its frame designs and application prospects in the context of our country, Nepal.
Prof. Dr.-Ing. Ramesh Kumar Maskey was born on 21 December 1959 in Biratnagar, Nepal. He completed intermediate in
Electrical Engineering from Institute of Engineering, Tribhuwan University in 1979. He received MSc. in Civil-hydropower
Engineering from Beylorussian Polytechnic Institute, Beylorussia (1987) and MSc. in Resources Engineering from University of
Karlsruhe, Germany (1996). He received doctorate in civil engineering from University of Karlsruhe in 2004. Since March 2006,
Dr. Maskey is a full professor of civil engineering at Kathmandu University (KU) where he is currently the Associate Dean for
academic and administrative affairs of School of Engineering. He served the Department of Civil and Geomatics Engineering as founding Head
of Department till 2013 since 2009. He is supervising the development of Hexa-copter on behalf of Centre for Excellence in Production and
Transportation of Electrical Energy (CEPTE/KU). He has more than 27 years of academic and professional experience in the field of hydropower
engineering. His research interest encompasses hydropower, renewable energy technology, robotics, distributed power system and hydraulics.
Er. Pratisthit Lal Shresthawas born on 8 December 1985 in Kathmandu, Nepal. He received B.E in Mechanical
Engineeringfrom Kathmandu University in 2008 as the batch topper. He has Master’s degree in Thermal Power Engineering from
National Institute of Technology (NIT), Tiruchirappalli, Tamil Nadu, India in 2012. He is currently working as a lecture in
Mechanical Engineering at Kathmandu University.
He has worked in projects Experimental Analysis of Nanofluid based Vapor Absorption Refrigeration System, Experimental
Investigations and Thermoeconomic Optimization of Absorption Refrigeration with Air Cooled Absorber and Energy Audit of a Local Four Star
Hotel.
Er. Banaya Baidar was born on 27 February 1988. He received B.E. in Mechanical Engineering and Production Technology in
2011 from HAMK University of Applied Sciences, Finland. He has MSc in Aeromechanics in Turbomachinery (Erasmus
Mundus) from KTH Royal Institute of Technology (Sweden) ,Aristotle University of Thessaloniki (Greece), and University of
Liege (Belgium). He is currently working as research fellow and visiting lecturer at Turbine Testing Lab, Department of
Mechanical EngineeringKathmandu University. He has worked as R&D Engineer (International Trainee) in KONE Corporation,
Finland and as a Trainee in LMS: Siemens PLM Software, Belgium. His research interests are Vibrations in turbomachinery, particularly Francis
and pump-turbines, Fluid-Structural Interactions and Sustainable energy solutions.
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