Solar Challenger
Future starts now
Tim van Leeuwen & Jesper Haverkamp
V6
Hermann Wesselink College
Advisor: F. Hidden
March 2010
Research Project – Solar Challenger – JeT Productions – Tim van Leeuwen & Jesper Haverkamp - 2010
Abstract
Main goal of this project was to make calculations and respective designs to create an electric
airplane prototype, capable of powering its flight either entirely or partially using solar
energy. This project intended to stimulate research on renewable energy sources for aviation.
In future solar powered airplanes could be used for different types of aerial monitoring and
unmanned flights.
First, research was done to investigate properties and requirements of the plane. Then,
through a number of sequential steps and with consideration of substantial formulas, the
aircraft‟s design was proposed. This included a study on materials, equipment and feasibility.
Finding a balance between mass, power, force, strength and costs proved to be particularly
difficult. Eventually predictions showed a 50% profit due to the installation of solar cells. The
aircraft‟s mass had to be 500 grams at the most, while costs were aimed to be as low as €325.
After creating a list of materials and stipulating a series of successive tests, construction itself
started. Above all, meeting the aircraft‟s target mass, as well as constructing a meticulously
balanced aircraft appeared to be most difficult. Weight needed to be saved on nearly any
element. We replaced the battery, rearranged solar cells and adjusted controls. Though
setbacks occurred frequently, we eventually met our goals with the aircraft completed whilst
weighing in at 487 grams.
Testing commenced with verifying the wings‟ actual lift capacities. Results were satisfying.
In addition, further testing on drag and propulsion was gratifying as well. Finally, the aircraft
truly took to the skies, but sadly crashed due to flaws in steering. Testing on solar cells
however, was disappointing. Instead of the expected 50 %, we only managed to achieve 10 %
profit. In addition, one can pose the question if leaving out the solar cells entirely would have
meant saving such considerable weight, that there would have been more profit after all. Final
costs of the project were €515.
Ultimately we can conclude purely solar powered flight is impossible, at least with the
materials available and taking Dutch climate into account. Further developments in solar
technology might create possibilities for solar planes in future. For now, in order to install
solar cells, too many aspects of the plane are sacrificed to save weight. This for example
resulted in a frame far too fragile.
Still, it should be noted that the plane we manufactured was a prototype only. Many
adjustments can be made. During the project we have seen that there is quite some room for
improvement. That is obvious, as this was the very first airplane we ever build. We gathered
enormous amounts of knowledge and we hope that in future this knowledge will be used to
continue working on solar powered planes. For if development continues, solar powered
aircraft might truly be used in future. Bear in mind: Future starts now.
2
Research Project – Solar Challenger – JeT Productions – Tim van Leeuwen & Jesper Haverkamp - 2010
Introduction
As we both enjoy aviation and are considering a study involving the aircraft industry, it had
soon become clear we wanted to do our research project about a topic related to flying.
Though aviation is a complex part of technology, we thought our expertise on physics and our
passion for flying would guide us through this project. Our first concern was finding a topic
both interesting, challenging and future-proof. Due to current turbulence in aviation we
decided on the following:
The desire to fly is nearly as old as humanity itself. Ever since we walked the earth, we
longed to get airborne, just like the birds above us did. In 1783 this dream became reality 1 .
“Historians credit France's Montgolfier brothers with the first pioneering balloon flight ” 2 .
Aviation‟s next revolution was in 1903, when Orville and Wilbur Wright took off with their
„Flyer 1‟ and flew 36 metres with their plane 3 . Flyer 1 was powered by a petrol engine, just
like later aircraft. Nowadays, aviation accounts for three percent of all CO 2 -emissions
produced by mankind 4 .
This doesn‟t seem much, but more important is that profit of commercial aviation strongly
relies on the oil price. Due to high prices 5 of crude oil lately, profits of commercial aviation
have been diminished and aviation industry is now looking for alternative energy sources to
propel modern-day aircraft. Options that are being considered are bio fuels, hydrogen and
ethanol6 . An option which is rarely considered is solar energy, an option we wanted to
investigate.
1
http://adventure.howstuffworks.com/first-flight-attempt.htm
Robert Lamb, 2008
3
http://www.wright-brothers.org/History/Just%20the%20Facts/1903fly.ht m
4
http://www.rotterdamairport.nl/nl/generalmenu/Over_Rotterdam_Airport/In_de_samenleving/Feiten_en_cijfers
5
http://images.angelpub.com/2009/03/1606/oil-price-chart-1-12-09.png
6
http://www.faa.gov/news/conferences_events/aviation_ forecast_2007/agenda_presentation/media/9 %20Rich%20Alt man.pdf
2
3
Research Project – Solar Challenger – JeT Productions – Tim van Leeuwen & Jesper Haverkamp - 2010
Table of contents
Front page
Page
1
Abstract
Page
2
Introduction
Page
3
Table of contents
Page
4
Introduction phase
Phases
Main goal, purpose and expectations
Research questions
Requirements
Page
Page
Page
Page
5
6
7
8
Design phase
Design proposal
Construction proposal
Test proposal
Page 9
Page 30
Page 32
Construction phase
Media attention
International aspect
Construction
Page 35
Page 36
Page 41
Test phase
Test results
Page 54
Conclusion phase
Conclusion
Evaluation
Page 60
Page 62
Additional sources
Page 68
Acknowledgements
Page 69
Jesper‟s log
Page 70
Tim‟s log
Page 73
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Research Project – Solar Challenger – JeT Productions – Tim van Leeuwen & Jesper Haverkamp - 2010
Phases
In order to minimize chances of failure, we set up the following scheme. It divides up the
project in five different phases, all having their own planning, goals and requirements:
Phase
Elements
Introduction phase Determine main goal, research
questions, requirements, planning.
Design phase
Research, orientation, plans,
calculations, proposals.
Construction phase Description of construction itself:
what succeeded, what went wrong
and in which way did we alter our
designs and plans.
Test phase
Observations and experiences
during testing and test results.
Conclusion phase Interpretation of test results,
conclusion, evaluation,
recommendations for future
projects.
Goal
Provide a starting point for our
project.
Set up a design proposal,
construction proposal and test
proposal.
Give an accurate description of the
progress of our project.
Provide an accurate description of
occurrences during testing.
Describe what can be learned from
this project, why it succeeded or
not and how this project can be
used later.
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Research Project – Solar Challenger – JeT Productions – Tim van Leeuwen & Jesper Haverkamp - 2010
Main goal, purpose and expectations
The main goal of this project is to make calculations and respective designs to create an
electric airplane prototype, capable of powering its flight either entirely or partially using
solar energy. This project intends to stimulate research on renewable energy sources for
aviation. Hopefully this will result in the environment no longer suffering due to emissions of
burning oil products. In future solar powered airplanes could be used for different types of
aerial monitoring and unmanned flights. Due to their light weight, silent engines and infinite
flying time, they might also be used as spy planes in inhospitable areas.
By doing broad research and making appropriate calculations, we hope to design an aircraft
which is actually able to fly. Our first concern is composing the right electrical system to be
used in our aircraft. Selecting suitable equipment and making useful drawings and schemes
will provide us with the basis for our project. Extensive testing will show how effective our
system functions in different circumstances. Once completed, our circuit will be combined
with the aircraft‟s frame.
If we manage to correctly set up our calculations, the aircraft should be able to fly. In case
testing shows the aircraft is not able to take off, we will first investigate how we can improve
the plane‟s properties. Though, when nothing seems to help anymore, we will slightly shift
our main goal and try to create a controllable, energy efficient vehicle using all equipment we
gathered so far. This will only be done in case all goes wrong.
This project runs over an extensive period of time, which will provide us with sufficient
opportunities to do research and create designs. We will make a strict planning and a precise
proposal to make sure our project will run smoothly. Assuming we will be able to make
accurate calculations, our expectations are that we will actually produce an aircraft capable of
flying on solar power. Even though we try to plan and predict everything as well as possible,
setbacks might occur. To prevent failure, we shall make sure there is enough room for
unexpected events.
6
Research questions
Research Project – Solar Challenger – JeT Productions – Tim van Leeuwen & Jesper Haverkamp - 2010
From our main goal we can derive the main research question involved in our project:
Is it possible to create an electric airplane prototype capable of using solar power to partly or
entirely power its flight?
Sub questions
In order to answer our main question completely, we need to look at several sub questions:
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
Is it possible to let the aircraft fly on solar power only?
How do you make sure no precious energy is spilled when the solar panels generate very
little energy?
How do you deal with the cells’ varying output in cloudy or sunny circumstances?
Which extra equipment is needed to make the solar cells function properly?
Which circuit is needed to make the plane remote controllable?
Which equipment and components are needed to control the plane?
What will be the plane’s size, mass, speed?
Which airfoil do you use, how big is it and how does it work?
How much lift do you need?
Which engine and propeller do you need?
Which solar cells generate most electricity with fewest mass and how big are they?
How do you mount the solar cells on the aircraft (inside or outside, wing or body)?
What will be the structure’s design?
Which materials do you need to construct the plane?
Where do you place all electrical equipment, making sure the aircraft is balanced and
what will the fuselage be like?
What will be the shape of the tail and elevator and how are they controlled?
In which order are you going to construct the plane?
Which effect does the position of the solar cells have on the efficiency of both the plane
and panels?
How much profit do the solar cells provide?
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Research Project – Solar Challenger – JeT Productions – Tim van Leeuwen & Jesper Haverkamp - 2010
Requirements
Before writing a design proposal, a complete set of requirements is needed. In this way we
know which limitations there are during construction. Not only will these requirements be a
guideline throughout our project, they will provide us with a starting point as well. After all,
mass, power, size and costs of an aircraft are all related. You need to fill in one first in order
to determine the others.
Element
Available time
Available
materials
Number of
participants
Final
product’s size
Number of
products
Budget
Requirements
At least 100 hours of which 50 are before the
summer holidays, 20 after the summer
holidays.
Nearly everything as long as we can afford it
and it‟s available in shops (on the internet) and
not custom made. Plenty of tools are available.
Two
Notes
Construction will be
before and during summer
holidays.
Experts, teachers and
other sources not
included.
Between 1.0 and 1.5 metres in width in order to Length and height depend
not let it be too small or too big. These
on mass and balance,
measurements can vary slightly if needed.
which will be determined
later.
One (prototype)
No more than €400 in total as long as no
sponsor has been found.
Environment
Outside
Media attention www.solarchallenger.tk, website with our
progress, sponsors, TU Delft?
No rainy circumstances
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Research Project – Solar Challenger – JeT Productions – Tim van Leeuwen & Jesper Haverkamp - 2010
Design proposal
When designing, there are three things to be considered. First there is the main goal, secondly
there are the research questions and thirdly there are the requirements. When combined, those
three elements form the basis of making a design proposal. To start out, we use the
requirements and see how we can implement them in our ma in goal and research questions.
The requirement we are currently most interested in, is the model aircraft‟s size. We intend to
construct an aircraft with a span measuring 1.5 metres. In this way the aircraft will not be too
large to handle and at the same time it will be large enough to provide us with enough room
for mounting solar cells and other equipment without space becoming too crowded. We will
use this very measurement as a basis throughout the design proposal.
To design the plane in an organized way, we set up a plan consisting of a number of steps.
These steps deal with several sub questions and will be filled in as we go:
Step 1:
Step 2:
Step 3:
Step 4:
Step 5:
Step 6:
Step 7:
Step 8:
Step 9:
Step 10:
Designing the right basic electrical system (no sizes, properties, etc. included).
Research on the size of the aircraft and probable mass.
Feedback on the engine, solar cells, battery etc.
Final decision on mass and thus the size of the aircraft.
Designing the final electrical system including properties and components.
Determining where to place the solar cells.
Designing the wing and doing a final check on lift, mass, size, etc.
Determining construction materials.
Designing the aircraft itself, keeping mass, centre of gravity, etc. in mind.
Calculating final costs
Step 1
Before continuing with calculations involving the size of the aircraft, we will look at the
electrical system involved. After all, our plane would be useless without properly functioning
electronics. This implies we will start out with answering sub questions 1, 2, 3, 4, 5 and 6:
1.
2.
3.
4.
5.
6.
Is it possible to let the aircraft fly on solar power only?
How do you make sure no precious energy is spilled when the solar panels generate very
little energy?
How do you deal with the cells’ varying output in cloudy or sunny circumstances?
Which extra equipment is needed to make the solar cells function properly?
Which circuit is needed to make the plane remote controllable?
Which equipment and components are needed to control the plane?
To start, we will answer question 6. A properly controllable plane needs several pieces of
equipment 7 .
7
http://www.mvccolu mb ia.nl/hoebeginik.htm# 07
9
The answer to question 1 was very obvious once we investigated the power consumed by an
engine. A website 8 showing engine characteristics listed a considerable number of engines.
All of those appeared to consume quite a lot of energy. Besides the fact that our engine needs
an enormous amount of power (which will unlikely be generated by our solar cells due to
Dutch climate 9 ) the engine also needs a steady energy flow. We don‟t want our aircraft to
crash due to one cloud and for that reason we will use a battery combined with solar cells.
Then the answer to question 2: When the solar panels are not generating lots of energy, we
must prevent energy from flowing from battery to solar panels. Therefore we will install a
diode between the solar panels and the battery. The diode will unfortunately consume some
power, but this is the only way to get things working. In order to keep voltage loss as low as
possible, we are going to use a „Schottky diode‟. This specific type of diode only uses 0.1-0.2
volts compared to a regular diode which contributes to the loss of 0.7-1.7 volts 10 .
Since we found a solution to question 1, the answer to question 3 has already been given.
Using a battery will not only help us keeping the plane airborne when limited energy is being
delivered by the solar panels, but it will also make sure that whenever the output of the solar
cells drops (for example due to a cloud passing by) the engine still receives enough power.
Knowing all the information we gathered so far, we can draw a circuit basically showing the
electronics inside the aircraft, which answers question 5 up to a certain extent. Since we don‟t
know anything about power, mass, battery size etc. yet, we are not able to draw all details.
The following scheme just provides us with a basic idea of which elements are needed to
control the aircraft, thus giving us a starting point for calculating the aircraft‟s mass in future.
-
+
-
-
Servo
Controller
Solar Cells + Battery +
Receiver
Research Project – Solar Challenger – JeT Productions – Tim van Leeuwen & Jesper Haverkamp - 2010
First there are a transmitter and receiver, which are used to send and receive signals from a
control panel. The receiver, located inside the plane, will send signals to elements called
servos. They can move the rudder, ailerons and elevator. Besides, the receiver also controls
the engine throttle. We will come back to question 6 in more details later, when we know
more about the mass, size and power of the aircraft.
Servo
Servo
M
8
http://www.rctechnics.eu/-c-130.ht ml
http://www.nlp lanet.com/nlgu ides/dutch-climate
10
http://www.absoluteastronomy.com/topics/Schottky_diode
9
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Research Project – Solar Challenger – JeT Productions – Tim van Leeuwen & Jesper Haverkamp - 2010
Step 2
Having completed the basics of our circuit, we can resume calculations about the aircraft‟s
size. When combined with the circuit, we can derive the engine‟s, battery‟s and solar cells‟
requirements. As proposed in „Requirements‟ (page 8), we intended to construct an aircraft
with a span measuring 1.5 metres. The influence of the wingspan on the plane‟s other
measurements will be investigated next. Research questions involved are:
7.
8.
9.
What will be the plane’s size, mass, speed?
Which airfoil do you use, how big is it and how does it work?
How much lift do you need?
These three research questions are related to each other as much as can be, namely lift comes
with speed and determines mass and size, but it relies on the airfoil used. We will look at the
aircraft‟s size first.
Size
We determined the aircraft‟s span should be
about 1.5 metres. In order to make
calculations and construction of the wings
easier, we change the span into 1.6 metres.
The ratio between span and chord
(illustrated 11 right) in average model aircraft
is between 1:7 and 1:8 12 . In our airplane this
would imply:
Width is 1.6 : 8 = 0.2 metres
Knowing both the wing‟s width and span,
we can calculate the wing‟s surface area.
This size will later be used in several
calculations.
Surface area= 1.6 metres × 0.2 metres = 0.32 square metres
Airfoil
Not only surface area is important for a well functioning wing, but having a correct airfoil is
important too. It is the airfoil‟s shape that provides the aircraft‟s lift. All airfoils rely on same
principle 13 , Bernoulli‟s principle. It 14 describes the relationship between velocity and pressure
in a moving liquid or gas:
11
http://www.myaero modelling.co m/wp/wp-content/uploads/2008/01/ar.jpg
http://www.mvccrash.nl/overons/00000097940bbf72d/
13
http://library.thinkquest.org/27948/bernoulli.html
14
http://www.daviddarling.info/encyclopedia/B/Bernoullis_law.html
12
11
Research Project – Solar Challenger – JeT Productions – Tim van Leeuwen & Jesper Haverkamp - 2010
P + ½ρv2 + gρh = k
P = Pressure (Pa)
ρ = Density (kg / m3 )
v = Velocity (m / s)
g = Acceleration due to gravity (m / s2 )
h = Distance from reference, measured in opposite direction of the gravitational force (m)
k = constant (kg / ms2 )
The formula proofs that if gravity, air density and position remain unchanged, pressure will
drop when flow velocity increases. In other words: if you have an airflow of high velocity and
low velocity under the same circumstances, the area containing the high airspeed, will show a
lower pressure. This implies that if the air flowing over the wing moves faster than under the
wing, the air pressure above the wing will be lower, thus sucking the wing up into the sky.
For this reason wings are shaped in such a
way that air moves faster along the upper
surface. This is done through making the
air above the wing move a longer distance
in the same time than the air underneath
the wing. Therefore the wing‟s upper
surface is more curved than its lower
surface. 15
Throughout the years many airfoils have
been developed 16 . Every single one of
them had excellent properties for different purposes, like low or high speeds, or stability.
Concorde‟s wing was quite different from a Boeing 747‟s for example. Still, there is no such
thing as „the perfect airfoil‟. Properties needed simply depend on the characteristics of the
aircraft. Our plane just needs a simple and ergonomic airfoil. It will be „Clark-Y‟ 17 :
Clark-Y18 basically is an airfoil with a flat bottom and a curved top. Not only have there been
many experiments about this type of wing, it is also easy to construct. The following table19
shows certain numbers defined as lift coefficient. These statistics will later be used in
calculations on lift.
15
http://www.yes mag.ca/focus/flight/bernoulli.gif
http://www.ae.illinois.edu/m-selig/ads/coord_database.html
17
http://upload.wikimedia.org/wikipedia/en/6/6a/ Clark_y.JPG
18
http://www.gliders.dk/clark_y.ht m
19
http://www.gerritentiny.nl/documenten/Microsoft%20Word%20-%20VLIEGEN4.GER.pdf
16
12
Research Project – Solar Challenger – JeT Productions – Tim van Leeuwen & Jesper Haverkamp - 2010
Angle of attack
0
1
2
3
4
5
6
7
8
9
10
11
12
Lift coefficient
0.29
0.36
0.43
0.50
0.57
0.64
0.71
0.78
0.85
0.92
0.99
1.06
1.12
Speed
Before we determine the aircraft‟s mass, we will take a look at its speed. Investigation on
several model aircraft shows the approximate flying speed is between 25 and 100 kilometres
per hour. 20 Taking into account the limited capacity of our solar cells, we aim to let the
aircraft fly at 30 kilometres per hour.
30 kilometres per hour= 30 × 1000 metres : 60 minutes : 60 seconds = 8.3 metres per second.
Mass & lift
At this very point in our investigation there are two options. Either we determine the probable
mass of the aircraft and try to design the appropriate plane in order to ga in enough lift or we
determine the lift we will probably gather and try to match the corresponding weight. We
choose the latter, since it is easier to make a plane lighter than to increase its lift. Making a
plane lighter can be done through removing several pieces of equipment or replacing them by
lighter ones (saving on the battery for example). On the other hand, trying to increase lift
takes a great effort, because it requires redesigning and manufacturing the entire wings.
Lift can be calculated precisely through „aviation‟s most important formula‟ 21 :
L = ½ c ×  × A × v2
L = Lift in Newtons
c = Lift coefficient (no unit)
= Air density (kg / m3 )
A = Wing‟s surface area (m2 )
v = Velocity (m / s)
20
21
http://www.aeroclub-drachten.nl/pagina's/modelvliegen.html
http://www.grc.nasa.gov/WWW/K-12/WindTunnel/Activities/lift_formu la.ht ml
13
Research Project – Solar Challenger – JeT Productions – Tim van Leeuwen & Jesper Haverkamp - 2010
This formula should not be confused with the formula for calculating drag 22 . This formula is
based on the same parameters, although when calculating drag the „drag coefficient‟ is used
and the letter A represents the frontal area of the object.
From our previous investigation we can derive the wing‟s surface area and the plane‟s
velocity. The lift coefficient is taken from the table previously shown by assuming that the
angle of attack is larger than one degree at take off. At ground level the air density23 is
approximately 1.23 kg / m3 . When filling in all numbers the results are as follows:
L = 0.5 × 0.36 × 1.23 × 0.32 × 8.32 = 4.88 N
The lift generated by our wings will be able to compensate for 4.88N of gravitational force.
Since 9.81 Newtons of gravitational force correspond to one kilogram of mass 24 , we can
calculate the mass of our aircraft:
4.88 N = 4.88N : 9.81N/kg = 0.497 kg
The second calculation shows us the answers to sub questions 7 and 9. When travelling at take
off speed the wings of our aircraft generate 4.88 N of lift, thus being able to lift 497 grams.
We will make a slight margin concerning mass. Therefore our target mass will be 450 grams.
Reynolds number
Besides determining if our wings generate enough lift, we must also know if our wings
actually generate lift at all. Namely, gently and laminar airflow over a wing will only start at a
certain velocity. In addition, when flying too fast, the airflow will also become too irregular
and turbulent. The speed range at which the airflow will be smooth and laminar, can be
estimated using a value called the Reynolds number. 25
Reynolds number 26 is a value given to the flow conditions around objects. For any object the
optimal Reynolds number differs, but as a rule of thumb we can assume the Reynolds number
is supposed to be between 5.0 × 104 and 2.0 × 105 for aircraft wings 27 . The Reynolds number
can be calculated through the following formula 28 :
Re = ρ × v × L × μ-1
Re = Reynolds number (no unit)
Ρ = Density (kg / m3 )
v = Velocity of fluid or gas (m / s)
L = Travelled length of fluid or gas (m)
μ = Dynamic viscosity (Pa × s)
22
http://en.wikipedia.org/wiki/ Drag_equation
http://en.wikipedia.org/wiki/Density_of_air
24
http://en.wikipedia.org/wiki/Mass
25
http://home.earthlink.net/~x-plane/FAQ-Theory-Reynolds.html
26
http://en.wikipedia.org/wiki/ Reynolds_number
27
http://www.personal.psu.edu/lnl/097/belg iu m.pdf
28
http://www.aerodrag.co m/Articles/ReynoldsNumber.ht m
23
14
Research Project – Solar Challenger – JeT Productions – Tim van Leeuwen & Jesper Haverkamp - 2010
The air density is 1.23 kg / m3 as determined previously (page 14). The travelled length of the
air is just over the wing‟s chord: 0.205 m. The dynamic viscosity differs according to
temperature and air pressure. At room temperature it 29 is 1.85 × 10-5 Pa×s. When filling in all
numbers, the results are as follows:
Minimum speed = Re × p-1 × L-1 × μ = 5.0 × 104 × 1.23-1 × 0.205-1 × 1.85 ×10-5 = 3.8 m/s
Maximum speed = Re × p-1 × L-1 × μ = 2.0 × 105 × 1.23-1 × 0.205-1 × 1.85 × 10-5 = 14.7 m/s
Fortunately our take-off speed is within those boundaries. The airflow over the wings should
be smooth and laminar.
Step 3
Having determined mass, size and the electrical system, we no longer need to estimate things,
but we can calculate values precisely. The first thing to do now, is to combine mass and size
with the electrical system. In this way we can start to create a list of materials and equipment
needed.
Parts included in the electrical system are the battery, servo engines, controller, engine and
solar cells. These elements are linked in the following way: The size of the aircraft determines
the engine‟s size. The engine requires certain power supply, which determines battery size
and controller size. Because of this order we will look at a suitable engine first. The sub
question involved is:
10. Which engine and propeller do you need?
Engine
Engines vary in certain ways . There are engines for high speed and engines for much force
at lower velocity. Namely, the power of an engine is described in rotations per minute per
volt. The lower this number, the more powerful the engine. A slow turning engine will be able
to pull heavier aircraft at lower speeds, whereas fast turning engines will pull lighter (stunt)
aircraft at higher speeds. Compared to other model aircraft, we intend to fly rather slow.
Therefore we will use an engine with a low volts to turns ratio.
30
Initially we found an engine which met some of our requirements: a speed 400 engine. Then
we discovered there are several other types of engines 31 . On one hand there are brushed
engines (e.g. speed 400), on the other hand there are brushless engines. The latter is a modern
invention and consumes considerably less power than the initial one. Brushless engines come
in two types 32 : inrunner and outrunner.
29
http://www.ce.utexas.edu/prof/kinnas/319LA B/Book/ CH1/PROPS/ GIFS/dynair.gif
http://adamone.rchomepage.co m/guide5.ht m
31
http://www.dynetic.co m/brushless%20vs%20brushed.htm
32
http://www.rcuniverse.com/foru m/outrunner_versus_inrunner%3F/ m_2371948/t m.ht m
30
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Research Project – Solar Challenger – JeT Productions – Tim van Leeuwen & Jesper Haverkamp - 2010
An inrunner consists of a several magnets covered by a metal casing. This creates a powerful
engine, which unfortunately produces lots of heat, thus loosing efficiency and requiring a
cooler. As we cannot afford extra mass, we decided to go for a less powerful, but more
efficient „brushless outrunner’. Taking mass and all other requirements into account, the
following engine 33 seems most suitable to us:
2208/17 Brushless Outrunner 1100KV
Price: €14.50
Element
KV (RPM / V)
Voltage
Nominal current
Maximal current
Efficiency (at 4-7A)
No load current (at 10V)
Internal resistance
Axle diameter
Dimension (Øxl)
Mass
Recommended model mass
Maximal propeller
Value
1100
6-12V
3-6A
8A (max 60 s)
74%
0.6A
225 mΩ
3mm
27.5 x 26 mm
36 g
200-500 g
8.5 x 5 inch
Propeller
As shown in the scheme above, a recommendation has been given on the maximal propeller
size, with the first number being the propeller‟s maximal diameter and the second being
maximal lead. A propeller with its lead being similar to its diameter is best suited for fast
flying airplanes, whereas a propeller with small lead and larger diameter is excellent at
providing maximal force, thus being perfect for heavy, slow flying aircraft. 34 As our plane
flies rather slow, the following propeller 35 seems most suited:
Master Airscrew Electric Propeller 8 X 5
Price: € 3.35
Element
Mass
Diameter
Lead
Value
Unknown
20.3 cm
13 cm
To be absolutely sure this propeller is perfectly suited to propel our aircraft, we can apply the
following formula and rule of thumb 36 , which shows the relation between speed, rotations and
lead. The propeller‟s speed must be two to three times as high as the airplane‟s take-off speed.
33
http://www.rctechnics.eu/220817-brushless-outrunner-1100kv-p-1692.ht ml
http://www.zinin mijnleven.nl/hobby/propellors/index.ht m
35
http://www.rctechnics.eu/electric-propellor-p-116.ht ml
36
http://www.modelbouwforu m.nl/ foru ms/%5Bfaq%5D-modelvliegen-electro/21998-welke-spoed-moet-mijnprop-hebben.html
34
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Research Project – Solar Challenger – JeT Productions – Tim van Leeuwen & Jesper Haverkamp - 2010
vprop = l × f
v = Velocity (m / s)
l = lead (m)
f = Rotations per second (Hz)
Our engine is rated to provide 1100 rotations per minute per volt. As our system functions at
8.5 volts (see below), we expect to operate at 9350 rotations per minutes, which is 156
rotations per second.
Propeller speed = l × f = 0.13 metres/rotation × 156 rotations/second = 20.3 m/s
Ratio propeller speed : airplane speed = 20.3 / 8.3 = 2.45
The propeller we selected should be perfectly suited, since its speed is approximately two and
a half times as high as the aircraft‟s speed. Therefore its torque is sufficient to propel the
aircraft.
Batteries
The engine requires a voltage ranging from six to twelve volts. This voltage should be
provided by both our solar cells and our battery. Another key aspect of the battery is mass.
In our quest for suitable batteries we first had a look at lithium- ion polymer batteries due to
their excellent power to mass ratio. However, LiPo batteries bring notable risks with them,
such as spontaneous combustion when overloaded 37 . LiPo batteries work best at a steady
power supply, but since the output of our solar cells varies heavily, we decided not to take the
chance of our airplane catching fire in mid-air, but doing extra research on alternative
batteries instead.
The second option is nickel-metal hydrate batteries. These batteries have the disadvantage of
being much heavier than LiPo batteries, but their reliability made us favour nickel- metal
hydrate batteries over LiPo batteries. We will install seven „high output‟ batteries, producing a
total of 8.4 volts, weighing in at 175 grams and having a capacity of 2500 mAh38 . This
capacity means that the cells will be able to provide a continuous current of 2.5 A during one
hour.
Solar cells (1)
The solar cells should provide enough power during flight to extend flying range drastically
or even power the aircraft entirely. Just as with all materials used on our plane, mass is a
crucial element, so the solar cells can‟t be too heavy. The research question involved is:
11. Which solar cells generate most electricity with fewest mass and how big are they?
37
38
http://www.rctoys.com/pr/2006/ 10/ 20/safe-use-document-thunder-power-lithiu m-poly mer-batteries/
Battery packet, HEMA Photo batteries
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Research Project – Solar Challenger – JeT Productions – Tim van Leeuwen & Jesper Haverkamp - 2010
There are very few companies selling single solar cells. Cells are often being integrated in
glass, something that would contribute far too much weight. Eventually we found a German
company, Lemo-Solar 39 , selling single cells. Fortunately their shop contained a variety of
cells, including one that meets our requirements:
Single solar cell
Price: €10.60
Element
Dimensions
Soldering strip
Polarity front
Polarity back
Nominal voltage
Nominal current
Maximal output
Mass
Value
100 x 100 mm
Tinned, 2 mm
Minus
Plus
0.5 V
3200 mA
1600 mW
6.4 g
Because of the chosen batteries and the 0.1-0.2 volts lost over the diode, solar cells we use on
the airplane must have a total output of 8.5 volts. This would require seventeen solar cells.
Besides the financial aspect, seventeen solar cells will also weigh too much and will probably
not fit in the airplane (more information in step 6). Therefore we will need smaller solar
panels besides the ones mentioned above. The cells will be soldered together with flexible
wiring. This will be no problem, as the cells are already equipped with soldering strips.
Solar cells (2)
Single solar cell
Price: €3.-
Element
Dimensions
Soldering strip
Polarity front
Polarity back
Nominal voltage
Nominal current
Maximal output
Mass
Value
29 x 78 mm
Tinned, 2 mm
Minus
Plus
0.5 V
630 mA
340 mW
1.6 g
In total we plan to use twelve solar cells measuring 10 by 10 centimetres and six cells
measuring 29 by 78 millimetres. When adding properties of all solar cells, the results are as
follows:
Mass: 12×6.4g + 6×1.6g = 87 g
39
http://www.lemo-solar.de/default_1.ht m
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Research Project – Solar Challenger – JeT Productions – Tim van Leeuwen & Jesper Haverkamp - 2010
Output: 12×1600mW + 6×340mW = 21240 mW ≈ 21 W
Engine power: 5A× 8.4V = 42 W
This implies that under ideal circumstances the solar cells will provide 50% of the engine‟s
power supply. Of course this would be an utopia, since we didn‟t take power loss by the
receiver, servo‟s and controllers into account. Tests will eventually show how close we can
get to our 50% energy reduction goal. We will go into more details about testing in the „Test
proposal‟.
Servos
The next step after investigating the right materials for energy supply and propulsion, is
finding the right equipment for controlling the aircraft during flight. This equipment includes
the receiver, engine controller and servos. First, we have a look at the servos, devices
operating the plane‟s ailerons and rudder 40 , which control vertical and horizontal movement.
These machines come in different sizes and shapes. Since our plane is lightweight and forces
on the aircraft won‟t be tremendous, we decided to go for the lightest servos 41 :
Micro Servo 3.7 grams
Price: € 7.50
Element
Dimensions
Mass
Speed (4.8V)
Torque (4.8 V)
Operating voltage
40
41
Value
19.7 x 17.44 x 8.37 mm
3.7 g
0.1 sec / deg
0.5 kg / cm
4.8 – 6.0 V
http://www.rc-airplane-world.co m/rc-airp lane-controls.html
http://www.rctechnics.eu/micro-servo-gram-p-2497.html
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Research Project – Solar Challenger – JeT Productions – Tim van Leeuwen & Jesper Haverkamp - 2010
Every flap, rudder or aileron needs a servo to operate. A regular airplane is co ntrolled using
ailerons 42 for rolling movements, the elevator 43 for up and down movements and the rudder44
for crosswind compensations. This is illustrated by the drawings on the previous page 45 .
We are unlikely to fly at high wind speeds due to expected fragility of our aircraft. Therefore
we will eliminate the servo for the rudder. It will not only save us weight by not using a servo,
but also through the removal of wiring. The total mass of our servo engines will be:
Mass: 3 × 3.7g = 11.1 grams
Engine regulator
Next up in the controlling equipment is the engine regulator. It controls throttle given by the
engine. Again, this part should weigh as little as possible and should be able to cope with
current and voltage in our circuit. We found the following suitable engine regulator 46 :
12A FLY Brushless ESC
Price: € 16.95
Element
Operating voltage
Continuous load
Peak load
Dimensions
Mass
Low voltage turn off 47
Value
7.2-12 V
12 A
15 A (Max 5 s)
22 x 18 x 5 mm
7.1 g
Automatic
Receiver
Of course the airplane doesn‟t control itself. We want a person on the ground to be able to
remotely control the aircraft. For this reason, we need a remote controller and a receiver. The
controller will send signals to the receiver, which will instruct the servo engines and the
engine regulator. We found the following suitable parts 48 :
E-Sky receiver, 6 channels, 35Mhz
Price: € 13.50
Element
Frequency
Mass
Dimensions
Voltage
Current
Antenna Length
Value
35 Mhz
14 g
45 x 23 x 13 mm
5V
11.5 mA
100 cm
42
http://www.rc-airplane-world.co m/image-files/rc-airplane-ailerons.gif
http://www.rc-airplane-world.co m/image-files/rc-airplane-elevators.gif
44
http://www.rc-airplane-world.co m/image-files/rc-airplane-controls-rudder.gif
45
http://www.rc-airplane-world.co m/image-files/rc-airplane-controls.gif
46
http://www.rctechnics.eu/12a-fly-brushless-esc-p-393.ht m
47
Once voltage drops below 7.2 volts, the controller switches off power to the engine, thus preventing batteries
fro m d ischarging too much.
48
http://www.rctechnics.eu/esky-ontvanger-kanaals-35mh z-p-1367.ht ml
43
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Research Project – Solar Challenger – JeT Productions – Tim van Leeuwen & Jesper Haverkamp - 2010
Remote control
Both the sender and receiver should function at the same frequency. Therefore our options for
choosing a suitable remote control were slightly reduced. Additionally there are great
differences between remote controls operating at the same frequency. Some are equipped for
controlling helicopters only, whereas others are best suited for controlling petrol powered
planes only. This difference originates from different controls needed for different planes. A
helicopter for example does not have a retractable undercarriage, while a large aircraft does.
Eventually we found the following49 :
E-Sky remote control, EK2-0404A
Price: € 29.95
Element
Channels
Frequencies
Energy source
Servo reverse
Voltage indicator
Dimensions
Colour
Antenna length
Usage
Value
4
35, 40, 72 MHz
8 x 1.5 AA battery
Manually
Automatic, Led
185 x 205 x 55 mm
Black
100 cm
Airplane, helicopter, Glider
Step 4
We can now make a decision on size and mass of the plane. At the start of our research
project, the wingspan we were striving for was 1.6 metres. Looking at the dimensions of the
equipment we will be putting in the airplane, there is no reason to change this plan.
Element
Engine
Battery
Servos
Receiver
Propeller
Engine
Wiring
Solar cells 1
Solar cells 2
Frame
Unforeseen
Total
49
50
Mass (grams)
7.1
175
11.1
14
5
36
10
76.8
9.6
70
10.4
425
Now we‟ve decided on the parts to be used, we can also
give a more informed prediction of the mass of the
plane. All the parts we just summed up add to a total of
335 grams, well below our target mass of 450 grams.
However, we haven‟t included all elements yet (such as
the frame, wiring and unforeseen additional mass). In
addition, we aren‟t certain yet about the mass of the
propeller, but we estimate it weighs 5 grams. We
reserve 70 grams for the frame, a reasonable amount
according to experts on internet forums 50 . Furthermore
we reserve 10 grams for wiring and 10 grams for
unforeseen mass. All these numbers add up to a total of
425 grams, so we should be well under our target mass.
http://www.rctechnics.eu/esky-zender-kanaals-35mhz-ek20404a-p-2784.ht ml
http://www.modelbouwforu m.nl/ foru ms/bouwverslagen-vliegen/59216-bouw-van-een-fijn-zwevertje.ht ml
21
Step 5
+
-
+
18 in series:
9.0 V
3200 mA
7 in series:
8.4 V
2500 mAh
+
Solar cells
Batteries:
1.2 V each,
2500 mAh
Batteries:
Solar Cells:
0.5 V each,
3200 mA
-
Servo
Controller
Receiver
Research Project – Solar Challenger – JeT Productions – Tim van Leeuwen & Jesper Haverkamp - 2010
The electrical system has now been completed. Knowing mass, size and properties we are
able to draw the final circuit:
Servo
M
Servo
-
Step 6
12. How do you mount the solar cells on the aircraft (inside or outside, wing or body?)
With the solar cells being a critical part of the plane, it is logical to have a good thought about
the solar cells‟ position in the plane. The solar cells account for a large part of the total mass,
so their position has to be well considered to keep the plane balanced, both on the ground and
during flight. Since the plane‟s fuselage will be very slim and the solar cells measure 10
square centimetres, it is most obvious to place the solar cells on the plane‟s wings. With the
plane being 160 centimetres in wingspan, we have plenty of space to place all solar cells. In
addition, placing solar cells on the tail will not only be impossible due to the tail‟s size, but
the plane‟s centre of gravity will also be shifted too much to the back.
22
Research Project – Solar Challenger – JeT Productions – Tim van Leeuwen & Jesper Haverkamp - 2010
We have to determine whether we will place the solar cells on top of the wings or inside the
wings. The choice was made quickly: we will place our solar cells inside the wings, since it
offers multiple advantages:



The assembly of the solar cells becomes much easier. If we would place the solar cells on
top of the wings, we would have to attach the solar cells to the covering foil which might
pierce the foil and possibly ruin lift properties.
Placing the solar cells inside the wings will leave aerodynamic properties of our wings
intact, whereas putting solar cells outside the wings would drastically increase the drag
of the wings and could reduce the lift they provide.
Placing the solar cells inside the wings largely eliminates the risk of damaging the highly
vulnerable solar cells, since they will now be protected by foil.
The schematic drawing below gives an impression of the right wing:
The six big yellow squares represent the six big solar cells in the wing; the small yellow
squares represent the smaller cells. We will leave some space between the solar cells to place
the ribs of the wing. All these ribs will give the wing its structural integrity. In step 7 we will
go into more details about the construction‟s design.
Step 7
13. What will be the structure’s design?
14. Which materials do you need to construct the plane?
Now that the solar cells‟ placing has been determined, we can make a list of all the additional
equipment we will be placing in the wings. Parts that will be put in the wings are:








Solar cells
Servos
Wiring
Foil
Ribs & cornices
Triplex beams
Axle for aileron
Ailerons
23
Research Project – Solar Challenger – JeT Productions – Tim van Leeuwen & Jesper Haverkamp - 2010
Our plane‟s wings will have a wingspan of 160 centimetres, a width of 20 centimetres and an
expected height of 2.5 centimetres. To prevent the wing from bending we will place two
triplex beams running through the wings. The front and rear cornice have already been preshaped 51 . In the diagram below you can find an overview of the wing. The numbers above the
wing represent the rib that is placed there:
The ribs will be made out of balsa wood, the lightest type of wood known to men 52 . Each rib
measures three millimetres in thickness. We will cover the wings using a covering foil called
Mylar. This material can be applied to the wing loosely, but will be tightened around the
frame by ironing it 53 . It weighs approximately seven grams per square metre and is strong
enough to lift the aircraft.
Cross section 1
The drawing below shows one of the wing‟s regular ribs. The yellow circles represent holes in
the ribs for wiring. The black rectangles in the middle of the wing represent two triplex
girders running through the wing. On top of these we will mount the solar cells. Besides
providing a base for the solar cells, the girders also give the wing structural integrity. The
black semi-circle and triangle show the pre-shaped front and rear cornice. The blue rectangle
shows the position of a solar cell in between the ribs.
1
Our solar cells will be mounted inside the wing. This requires the ribs to be placed eleven
centimetres apart, for else the solar cells won‟t fit. We also need to make sure there is enough
room to construct the ailerons. Besides, some space must be kept free to install a servo engine.
These demands result in three alternative ribs which will be used in the aft of the wing:
51
http://muco-modelbouw.n l/index.php?lang_id=1&c_id=590&ref_change=outside
http://pldaniels.com/fly ing/balsa/balsa-properties.html
53
http://www.modelbouwforu m.nl/ foru ms/verlijming-constructie/44864-mylar-folie-hoe-verwerk-je-dat.html
52
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Research Project – Solar Challenger – JeT Productions – Tim van Leeuwen & Jesper Haverkamp - 2010
Cross section 2
In the second cross section we see the servo‟s placing in the wing.
Cross section 3
The third cross section represents the last rib before the aileron, the element in the wing which
allows us to steer the plane. You may notice an extra beam just before the hole for the aileron.
This beam provides a surface around which the covering foil can be wrapped.
Cross section 4
The fourth cross section is the rib that can be found in the part of the wing where the aileron is
placed. As you can see, the rear cornice of the wing has been cut off. Instead we will place the
aileron there. In addition, the large solar cell isn‟t shown, because in this part of the wing we
will locate the smaller cells instead. They are too small to rest on top of the triplex beams.
Therefore they will be suspended on top of a little piece of rope attached to the triplex girders.
4
Step 8 & 9
Fuselage
The aircraft‟s fuselage is among the most important parts of the plane. All electronic
equipment is to be installed here. Moreover, wings and landing gear are connected to the
plane‟s fuselage. As weight and balance are crucial to an aircraft, it is important to make a
detailed drawing showing where all equipment will be placed. To monitor the balance the
plane‟s fuselage will be suspended by one thread during construction. In that way a flaw in
balance will be noticed quickly as the plane flips over when not properly loaded. Sub
questions involved in parts 8 and 9 are:
25
Research Project – Solar Challenger – JeT Productions – Tim van Leeuwen & Jesper Haverkamp - 2010
15. Where do you place all electrical equipment, making sure the aircraft is balanced and
what will the fuselage be like?
16. What will be the shape of the tail and elevator and how are they controlled?
Fuselage
First up is the fuselage. Since drag is an important factor when co ncerning the engine‟s
capacity, we should keep drag as low as possible. We intend to construct a frame measuring
seven centimetres wide. In order to keep the structure both light weight and strong, we shall
construct a triangular shaped fuselage. The fuselage will be 28 centimetres long, thus
providing us with enough room to place all electrical equipment. However, our seven AA
batteries measure 54 five centimetres each. Therefore they can‟t be installed in one line. The
entire scheme of our plane‟s fuselage can be found below. Due to heat produced by several
pieces of equipment 55 the back side will be left open.
As shown in the drawing, the centre of gravity is to be located at ⅓ of the wing‟s depth. This
is a rule of thumb 56 for building aircraft. With the equipments‟ mass being so low and exact
mass of the frame yet unknown, it is impossible for us to calculate the momentum for each
element in the plane. Therefore the scheme shown above will be used as a guideline to
position all equipment.
Once our aircraft has been completed, its centre of gravity will be determined precisely by
slightly moving the equipment inside the plane‟s fuselage. Another rule of thumb 57 is to rather
position the plane‟s centre of gravity slightly too far in front than too far to the rear. This is
due to the plane getting in stall position too easy when the centre of gravity is located in the
rear.
54
http://en.wikipedia.org/wiki/AA_battery
http://www.modelv liegclub-swentibold.nl/To_BEC.ht m
56
http://www.modelbouwforu m.nl/ foru ms/zweefv liegen/74239-afstellen-zwaartepunt-zwever.ht ml
57
http://www.fms-spaarnwoude.nl/home/content/view/272/ 88888915/
55
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Research Project – Solar Challenger – JeT Productions – Tim van Leeuwen & Jesper Haverkamp - 2010
The fuselage‟s frame will be constructed with balsa wood and covered with Mylar foil.
However, due to safety reasons, we will manufacture the fuselage‟s base out of a plate of
balsa wood, for else the equipments‟ heat will melt the Mylar foil. The frame itself will
feature triangular shaped parts. The holes in between the 2nd and 3rd and between the 4th and
5th triangle are points to attach the wing to the fuselage. As shown in the diagram below, the
main gear will be placed slightly in front of the centre of gravity. This will make the aircraft
fall over to the back when landed. A little wheel mounted underneath the tail will prevent the
aircraft from sustaining damage. Besides, when on the ground the aircraft will always stand in
a tilted position, thus providing more lift at take off (see diagram page 13).
Another important element of our aircraft is the positioning of two supporting triplex beams
for the wings. They can be seen in the diagram below. The triplex beams will be attached to
the landing gear, to provide maximum support for our wings. The beams will measure 10 x 5
millimetres.
Tail and elevator
Up so far there are still two vital airplane parts we haven‟t mentioned. They are the horizontal
and vertical stabilizer, better known as tail and elevator. They provide stability for our
aircraft. In addition they are vital elements in controlling the plane. Just like the fuselage,
elevator and tail will be constructed with balsa wood and Mylar foil. Strength is once again
provided by triangular shaped balsa frames.
The tail‟s and elevator‟s size are determined by the wing‟s area. The ratio 58 between elevator
and wing is 4:1, whereas the ratio between tail and wing is 25:1. This implies the areas of
both the tail and elevator will be as follows:
Wing area: 1.6 × 0.2 = 0.32 m²
Elevator area: 0.32 × 0.25 = 0.08 m²
Tail area: 0.32 × 0.04 = 0.0128 m²
Elevator size: 60 centimetres wide and 13 centimetres in depth.
Tail size (triangular): 18 centimetres in depth and 15 centimetres high.
58
http://www.auf.asn.au/groundschool/umodule6.ht ml
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Research Project – Solar Challenger – JeT Productions – Tim van Leeuwen & Jesper Haverkamp - 2010
The tail will be connected to the fuselage with a triplex beam. For extra structural integrity the
beam will run all the way from tail to engine. The diagram below shows the entire aircraft,
including the tail, wings and fuselage.
As a final check we will calculate the balsa wooden frame‟s mass. Every rib will weigh half a
gram. Twenty ribs weigh 10 grams. Triplex beams, front cornice and rear cornice will weigh
approximately 30 grams. In addition, the fuselage and landing gear weigh 20 grams,
compared to 10 grams for the tail. Mylar will come in with just several grams. This adds up to
a total of 70 grams.
Step 10
As our design proposal has nearly been finished, we can now determine the costs of our
project. Our budget is €400. The table below shows we should be well under that amount.
Element
Solar cells 1
Solar cells 2
Engine
Propeller
Remote control
Receiver
Servos
Engine controller
Battery
Frame
Wiring
Unforeseen
Total
Cost
€ 127.20
€ 18.00
€ 14.50
€ 3.35
€ 29.95
€ 13.50
€ 22.50
€ 16.95
€ 25.00
€ 35.00
€ 5.00
€ 14.05
€ 325.00
28
Research Project – Solar Challenger – JeT Productions – Tim van Leeuwen & Jesper Haverkamp - 2010
Another crucial issue is weight. Having a clear picture of which elements we will be using, it
is time to add up the masses of all individual components. The results show we are still well
on track to reach our target mass.
Element
Engine controller
Battery
Servos
Receiver
Propeller
Engine
Wiring
Solar cells 1
Solar cells 2
Frame
Unforeseen
Total
Mass (grams)
7.1
175.0
11.1
14.0
5.0
36.0
10.0
76.8
9.6
70.0
10.4
425
= estimated
29
Research Project – Solar Challenger – JeT Productions – Tim van Leeuwen & Jesper Haverkamp - 2010
Construction proposal
After having done thorough research on the plane‟s design, it is time to start thinking about
construction itself. Just as we did in the design proposal, we set up a plan dealing with the
order of construction:
Step 11:
Step 12:
Research on where to order construction materials.
Determining the order of construction.
The sub question being answered is:
17. In which order are you going to construct the plane?
Step 11
To start with, we will order the parts of the electrical system. We try to keep mailing costs as
low as possible. Therefore we must order as many items as possible at the same supplier. We
composed the following list of materials needed. All supplies will be ordered on the web.
Electronics
All the electronics are to be ordered at rctechnics.eu. Their shop features a broad range of
items, all good quality products according to people on internet forums. The following items
will be ordered at rctechnics.eu:





Receiver
Engine regulator
Servos and wiring
Engine
Remote control
Construction materials
Just as the electronics, the propeller and landing gear wheels will be ordered at rctechins.eu.
Unfortunately this shop doesn‟t sell other construction materials. In addition, finding a web
shop which sells and ships balsa wood is extremely difficult. Eventually we found a supplier
in Groningen, who could offer us balsa wood and beams for the ailerons and rudder:
netshop.nl/shop/krikkem. Glue is available at a local DIY shop and batteries will be bought at
the local HEMA. In contrast, Mylar is not available in any shop in Holland. At last we found a
shop in Great Britain selling Mylar: indoorflyer.co.uk. The shopping list for construction
materials is as follows:



Propeller (rctechnics.eu)
Landing gear wheels(rctechnics.eu)
Balsa (netshop.nl/shop/krikke)
30
Research Project – Solar Challenger – JeT Productions – Tim van Leeuwen & Jesper Haverkamp - 2010




Beams for ailerons and rudder (netshop.nl/shop/krikke)
Glue (Praxis)
Mylar (indoorflyer.co.uk)
Batteries (HEMA)
Solar cells
As told in our design proposal, the solar cells will be ordered at lemosolar.de.
Step 12
Once we receive our supplies, we will put together the electrical system. After composing it,
we will run several tests as described in the „Test proposal‟. We will collect data we need and
make amendments to the system if desired. After such possible adjustments we will make a
new estimation of the plane‟s mass and, if needed, adjust the wings‟ size or the plane‟s
design.
With the electrical system being complete, it is time to focus on the plane‟s body. A crucial
element here is design and construction of the wing. This is the next step in our process of
construction. We will construct two separate wings out of balsa wood, place solar cells on the
correct places and then wrap the wings with Mylar foil to secure their shape.
Once completed, we can test the lift the wings generate. The test is described in our „Test
proposal‟. If the wings don‟t produce the lift required, we will have to make adjustments.
With the wings and electrical system now completed, we will construct the rest of the aircraft,
which consists of the elevator, tail and fuselage. Next, we will mount the electrical system in
the plane‟s fuselage, glue the landing gear onto the plane and determine the centre of gravity.
The last step in construction is to fasten the wings to the fuselage. If needed, we will move
items inside the plane in order to get the centre of gravity in the right position.
If all goes well, we have built a complete plane by now and we can start testing. If required,
adjustments will be made during and after testing.
31
Test proposal
Research Project – Solar Challenger – JeT Productions – Tim van Leeuwen & Jesper Haverkamp - 2010
To make an organized test proposal we have to follow the steps we‟ve set ourselves:
Step 13:
Step 14:
Determining what needs to be tested and in which order.
Set up plans on how to run tests, where and with which materials required.
Step 13 & 14
Throughout the project several tests need to be run. We will investigate the following data:




Solar cells’ output and profit
Lift test
Drive test
Flight test
The solar cells‟ output and profit
18. Which effect does the position of the solar cells have on the efficiency of both the plane
and panels?
19. How much profit do the solar cells provide?
To answer the two sub questions concerning the solar cells‟ profit, we came up with the
following test setting. After we ordered components such as solar cells and the engine, we
will compose the electrical system. At this point we haven‟t started construction of the plane
yet. First, we will fully charge the batteries, connect them to the engine and then let the engine
run at full throttle. We will record the time it takes for the batteries to run out. In order to
minimize errors, we will redo the test three times.
In a second test we will add solar cells to our electrical system. We make sure the solar cells
receive plenty of light and then we let the engine run at full throttle again. We will write down
the time it takes for the batteries to run out and compare this to the previously clocked time. In
this way we will be able to tell something about the profit of the solar cells.
A third test aims to determine the effect of Mylar foil on the solar cells‟ output. We will run
the second experiment again, but now, we will place Mylar foil over the solar cells. This will
probably decrease their power supply. Through this experiment we will be able to say
something about the influence of the Mylar foil.
Unfortunately the solar cells‟ output strongly depends on weather. If time is available we will
do the second and third test several times in both cloudy and sunny conditions. Unfortunately
a photo meter to measure sunlight intensity59 is not available.
59
http://en.wikipedia.org/wiki/Photometer
32
Research Project – Solar Challenger – JeT Productions – Tim van Leeuwen & Jesper Haverkamp - 2010
Lift test
Once construction of the wing has been completed, it is time to test lift. At this point we still
have two separate wings. Before both parts are glued together, we will take one of the wings
and attach it to a force meter. This composition will be mounted into a free ly moveable frame.
The frame, composed of K‟nex parts, will be fit on a bicycle‟s basket.
One of us will cycle at 30 kilometres per hour, the intended take-off speed. Speed will be
measured with an odometer on the bicycle itself. If calculations have been correct, the force
meter should measure a difference of approximately 2.5 Newton. Of course we will take into
account influences that could disturb our test, like wind, loss of surface area due to K‟nex
frame, etc.
Drive test
Eventually we reach a point where the aircraft is finished. We will have determined the centre
of gravity and will have made sure the controls function properly. Before it is actually time to
take off, we will perform several driving tests. We will position the airplane on a smooth
surface, for example a gym floor. Then we will slowly increase throttle to let the aircraft
„taxi‟.
Now it is time to make final adjustments. Drive tests might show deviation in driving
direction, lack of power or other defects. Once those problems have been solved, we will do a
final driving test. We will keep increasing throttle until the tail will get airborne. Namely, the
tail coming off the ground is a first indication of taking off. This is because the mass of the
aircraft is no longer supported by the wheels, but by the wings. The centre of gravity is
slightly behind the wheels, thus making the aircraft falling over to the back. When the mass of
the aircraft is no longer supported by the wheels, but by the wings, the centre of gravity is at
⅓ of the wing, thus balancing the aircraft. This process is shown by the following
pictures 60/61 .
Taxiing
Take-off
Fn
Fn
Fg
60
61
Flif t
Fg
http://media.photobucket.com/image/ph-pba/AirKas1/PH-PBA_GRQ_12-07-09kj.jpg
http://farm4.static.flickr.co m/3135/2768004875_d48345f8bc_o.jpg
33
Research Project – Solar Challenger – JeT Productions – Tim van Leeuwen & Jesper Haverkamp - 2010
Flight test
At this point in our research project we know whether or not our wings produce enough lift
and the engine and propeller generate enough power to propel the plane. Still, there is one big
challenge left: flying.
According to people on internet forums, flying a model aircraft is a very difficult discipline. It
requires extensive expertise and experience with flying. As we don‟t want to crash our aircraft
during its maiden flight, we will bring in an experienced person from a flying club. He will fly
our aircraft at first. With his help we will eventually learn how to control the plane.
The last problem that needs to be solved is finding a suitable runway. As our plane is
probably going to be fragile, it is unlikely we can take off from any parking lot. Currently we
plan to use an artificial turf field as a runway.
34
Media attention
Research Project – Solar Challenger – JeT Productions – Tim van Leeuwen & Jesper Haverkamp - 2010
Website
We intended to launch a website on the internet. Here people would be able to follow our
progress and see pictures of the airplane. However, we didn‟t want to spend any money on an
expensive internet domain, so once the free testing period had expired, unfortunately the
website was cancelled.
Sponsors
Since this project is quite costly, we had to take a look at possible sponsors. Being
environmentally friendly is a major aspect in our project. We searched for companies that
present themselves as environmentally friendly. Companies we ended up looking at were
Triodos and ASN bank. However, Triodos only sponsors five major projects on a yearly basis
and the ASN bank rejected our proposal.
Another effort we made was with the company that supplied us with solar cells. We asked
them if they were willing to provide us with solar cells or give us discount on solar cells in
return for some promotion. Luckily, they gave discount on the solar cells, but mailing costs
proved to cancel out our „profit‟.
Logo
Just like any plane, ours will feature a company logo on its tail. We chose to create the
following logos:
Ai rcra ft Cons truction Company
Ai rline
„JET‟ is not only a synonym for airplane, it also represents our initials: J(esper) E(n) T(im).
The globe shown on the logo represents JET‟s internationally orientated roots.
35
Research Project – Solar Challenger – JeT Productions – Tim van Leeuwen & Jesper Haverkamp - 2010
International aspect
As part of our internationally orientated education, our research project should include a piece
in which we discuss how our research project is internationally relevant. We think our
research project is internationally relevant, because it is based on a world-wide hot topic.
Energy demands
The issue of meeting the worldwide energy demands is currently high on any politician‟s
shortlist. Right now we are able to fulfil our needs, but knowing we consume 85 million
barrels of oil a day62 , it is clear we will run out of our energy supplies one day. That day is
coming closer by the minute. Engineers worldwide are searching for a lternatives to meet our
demands. Their focus mainly lies on the renewable energy sources, such as wind and solar
power 63 .
Their reasoning to focus on these sources of energy is simple: such sources won‟t run out for
billions of years and are capable of meeting the world‟s energy demand. Covering 10% of the
Sahara desert area with solar cells for example would be sufficient to supply energy to the
whole world 64 and wind turbines in shallow coastal waters could account for 20% of energy
demands in the USA 65 .
Solar power thus is an interesting option. Recent years have seen solar power production
climb with a staggering 40% per year 66 , but when looking at statistics showing67 shares in
total energy supply, we will notice that solar power production does not even account for one
percent. We should realise that there still is a long way to go.
Our solar powered plane could let people come to realize just what the possibilities of
renewable energy sources are, especially solar cells. If we can make a plane fly using solar
power, other possibilities are nearly endless! People might consider placing solar panels on
their roof or on their carport to supply part of the power for their houses. There are a lot of
advantages to solar panels: four square metres of solar panels supply 10% of the annual
energy consumption of an average household 68 . In addition, solar panels could recover 69 their
costs in about ten years and solar panels can increase the value of your house, since a home
becomes friendlier to the environment and has considerably lower energy costs.
Not only is solar power being looked at as an option to supply energy we use in our
households, solar power has also come into picture for powering vehicles. This mostly shows
through all sorts of contests being held for technical institutions.
62
http://peakoil.b logspot.com/2006/03/peak-o il-is-closing-in.ht ml
http://en.wikipedia.org/wiki/ Renewable_energy
64
http://en.wikipedia.org/wiki/Desert#Solar_energy_resources
65
http://www.motherearthnews.com/ Renewable -Energy/Offshore-Wind-Po wer.asp x
66
http://en.wikipedia.org/wiki/Solar_power#Develop ment.2C_deploy ment_and_economics
67
http://www.iea.org/textbase/nppdf/free/2008/key_stats_2008.pdf
68
http://www.milieucentraal.nl/pagina?onderwerp=Zonnepanelen
69
http://www.olino.org/articles/2006/ 07/ 31/de-terugverdientijd-van-zonnepanelen
63
36
Research Project – Solar Challenger – JeT Productions – Tim van Leeuwen & Jesper Haverkamp - 2010
Solar cars
The most serious option being looked at is solar energy to power cars. With hybrid and plugin electric cars being introduced to the market, solar power becomes an interesting option to
supply energy. A famous contest between solar powered cars is the World Solar Challenge, a
race across the Australian desert being held every two years 70 . This race catches worldwide
attention. Technology used in cars involved can be replicated in other cars.
In recent years the race has become well-known in The Netherlands because of success of the
Technical University of Delft with their NUNA 71 solar powered car. The TU Delft has won
the World Solar Challenge four times in
a row 72 , each time with a modified and
upgraded car. When the team entered
competition with NUNA 1, they won
the race with an average speed of 92
kilometres per hour 73 . Two editions
later NUNA 3 74 won the World Solar
Challenge with an average speed of 103
kilometres an hour 75 . In fourth edition
NUNA 4 won with an average speed of
93 kilometres an hour, even though this
car had only 6 m2 of solar panels,
instead of 9 m2 used in previous editions 76 .
Cars competing in the World Solar Challenge distinguish 77 themselves from normal cars
because of their extremely low drag and low mass. The cars are very aerodynamic (up to 6
times more aerodynamic than cars driven today) and have a very low rolling resistance,
thanks to thin and well lubricated wheels. Moreover, the cars are as light as a feather
compared to normal cars. Namely, a regular car usually weighs 78 around 1000 kilograms,
whereas the newest version of the NUNA (NUNA 5) weighs 79 just 160 kilograms. Solar
panels used on these cars are of very high quality and have an extremely high output
compared to normal solar cells. Although the NUNA 5 doesn‟t have the luxurious items we
might want in our cars, such as a radio or air conditio ning, we can still learn a lot on how to
make our cars lighter and how to lower their drag. Besides, we can learn how to incorporate
solar cells in our cars. All these aspects could make present day cars more fuel efficient.
70
http://www.wsc.org.au/
http://www.tudelft.n l/live/pagina.jsp?id=a43ae927-9cc7-4716-ab01-c4795f6c11a3&lang=nl
72
http://www.globalg reenchallenge.com.au/wsc-evolution/previous-winners
73
http://en.wikipedia.org/wiki/ Nuna_1
74
http://c0378172.cdn.cloudfiles.rackspacecloud.com/12227_15070993902.jpg
75
http://en.wikipedia.org/wiki/ Nuna_3
76
http://en.wikipedia.org/wiki/ Nuna_4
77
http://nl.wikipedia.org/wiki/Categorie:Zonnewagen
78
http://www.cbs.nl/nl-NL/ menu/themas/verkeer-vervoer/publicaties/artikelen/archief/ 1999/1999-0361-wm.ht m
79
http://www.nuonsolarteam.nl/ 2009/06/nuna5-onthuld/
71
37
Research Project – Solar Challenger – JeT Productions – Tim van Leeuwen & Jesper Haverkamp - 2010
Solar boats
Solar power has become an interesting option for small boats too, mainly due to the Frisian
Solar Challenge held in 2006 and 2008 80 . The organizers of this event wanted to create a
counterpart of the World Solar Challenge and have done so by making solar powered boats
race on the very same water used for the famous „Eleven cities‟ speed skating race 81 .
Since small boats need a relatively small engine to power them (a five horsepower engine is
sufficient to power a small vessel 82 ) an electric power source is a serious option to be
considered. A solar panel might just be the ideal way to
power the engine since most boats have a large area to place
the solar cells on and spend all their time outdoor in sunlight.
The hydrodynamics used in the Frisian Solar Challenge can
be applied to commercial yachts as well, no matter what size
they are. A streamlined hull is a key element for a vessel to
achieve low fuel consumption and streamlining is just what
the Frisian Solar Challenge is all about. Powering freighters
using solar power is no realistic option since big carriers
require tremendous power 83 . Giant kites would be more
suitable to propel these ships 84 . Still, we could reduce global
carbon dioxide emissions drastically by making vessels more
efficient, since naval traffic accounts for five percent 85 of
worldwide CO 2 emissions, nearly twice as much as aviation.
Solar planes
Last of all, attempts have been made in the last decades to power aeroplanes using solar cells.
One of the biggest organisations researching the feasibility of a solar powered plane is NASA
with their ERAST program86 . This program resulted in four prototype electrical planes
(NASA Pathfinder 87 , NASA Pathfinder Plus, Centurion88 and Helios 89 ) which all four flew
using solar cells. The planes got increasingly bigger as the project went on and several
records, such as the altitude and endurance records 90 , were broken. These planes, however,
were unmanned planes, steered through radio controls. Although Helios could carry up to 230
kilograms of mass, there was no place for a pilot.
80
http://www.frisiansolarchallenge.nl/
http://www.frisiansolarchallenge.nl/route-en-reglementen/route
82
http://www.s malloutboards.com/choose.htm
83
http://www.howstuffworks.com/ floating-city1.ht m
84
http://iloapp.seamanshiptutor.com/blog/blog?ShowFile&image=1201089418.jpeg
85
http://www.guardian.co.uk/environ ment/2007/ mar/ 03/travelsenviron mentalimpact.transportintheuk
86
http://www.nasa.gov/centers/dryden/history/pastprojects/Erast/index.ht ml
87
http://en.wikipedia.org/wiki/NASA_Pathfinder
88
http://www.dfrc.nasa.gov/gallery/ movie/Centurion/HTM L/ EM -0003-01.ht ml
89
http://www.pvresources.com/en/helios.php
90
http://askmagazine.nasa.gov/pdf/pdf11/48741main_FIG1.pdf
81
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Research Project – Solar Challenger – JeT Productions – Tim van Leeuwen & Jesper Haverkamp - 2010
Planes that did succeed in carrying a person with it were
Sunseeker 91 and Solar Challenger 92 . In 1981 Solar Challenger
crossed the Channel93 , whereas in December 2008 Sunseeker
was the first solar powered plane to cross the Alps. In 2010
the successor of Sunseeker, Sunseeker II 94 , will make a tour
across Europe to demonstrate the possibilities of the plane.
Sola r Challenger
In June 2009 a new solar powered plane was
revealed 95 to the world: Solar Impulse 96 . This
plane has a wingspan of 64 metres (larger than
most commercial aircraft 97 ), can carry one person
and weighs just 1600 kilograms. If all tests go
according to plan, the successor of Solar Impulse
will make a flight around the world in 2011. The
designers reckon this will take approximately 25
days, since the plane flies at just 90 kilometres an
hour.
The examples above illustrate that it is still impossible for mankind to transport hundreds of
people in a plane over large distances using solar energy. One of NASA‟s aircraft could carry
three persons, but the ride wouldn‟t be very comfortable due to the plane‟s shape. Also speed
is an issue: whereas current planes have a cruising speed of 900 kilometres per hour, solar
powered planes travel at approximately 80 kilometres per hour. At this speed a trip from
London to Sydney would take about 216 hours, or 9 days! To keep aviation the way it is
today, we have to use fossil fuels, just because the amount of energy they deliver is
unmatched.
Investigation aircraft
Although solar powered airplanes are not useful for passenger transport at this moment, it
might offer new possibilities to other brands of aviation. Solar planes have features common
planes don‟t have. The most useful ability is that solar powered planes could stay airborne
forever, for they, rather than carrying their fuel with them, gather their energy while flying.
This ability provides lots of opportunities for solar powered planes. NASA already fitted their
Pathfinder plane with measuring devices to observe coral reefs around Hawaii, forest
regrowth after damage by a hurricane and sediment concentrations in coastal waters 98 . As the
examples illustrate, solar powered planes could be used for research because of their long
flight time, low flying speed and ability to fly at nearly any altitude.
91
http://solar-flight.com/sunseeker/index.ht ml
http://www.donald monroe.com/gallery/albums/solar-challenger/sc126_01.jpg
93
http://www.donald monroe.com/gallery/solar-challenger/
94
http://solar-flight.com/sunseekerII/index.ht ml
95
http://www.solarimpulse.co m/sitv/pictures.php?lang=en&group=med ia
96
http://www.kennislin k.nl/publicaties/solar-impule-v liegt-op-zonlicht
97
http://en.wikipedia.org/wiki/File:Giant_planes_comparison.svg
98
http://www.nasa.gov/centers/dryden/news/FactSheets/FS-034-DFRC.html
92
39
Research Project – Solar Challenger – JeT Productions – Tim van Leeuwen & Jesper Haverkamp - 2010
Commercial use of solar planes
Solar powered planes have been tested for commercial use as well. In 2002, NASA‟s
Pathfinder Plus was fitted with communication relay equipment and was sent to fly at an
altitude of 19 kilometres. From there it was able to send television signals back to earth,
making the plane equivalent to a radio tower with a height of 19 kilometres 99 .
Military purposes
World-wide military organizations could also be interested in solar powered aircraft. A solar
powered plane satisfies many of the needs of military organizations. It doesn‟t use any fuel, is
silent because of the electric engines, can fly at high altitudes (which makes it difficult to
detect on radar), can fly without refuelling, is relatively cheap compared to modern day planes
and can fly unmanned so no human lives are risked. All these properties will make a solar
powered plane desirable. Also, military organizations can mount a camera or measuring
devices on the plane to use it for purposes like observation, an aspect o f warfare which has
become more and more important the last decades.
Model aviation
Our solar powered plane could also inspire a whole new branch to be formed in the mode l
flight industry. Right now model flight industry is mainly based on aircraft with an electric
engine or a combustion engine and few planes with an electric engine charge their batteries
using solar cells. After having shown flying with solar cells with a relatively small budget is
possible, our plane could inspire many people around the world to build an aircraft of their
own. When we posted questions on a forum asking whether other people, whom mostly had
extensive experience with model aircraft, thought our project was feasible, we got numerous
reactions of people asking us to let them know if and how we had succeeded, so they could try
building a plane of their own.
99
http://en.wikipedia.org/wiki/ NASA_Pathfinder#Atmospheric_satellite_tests
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Research Project – Solar Challenger – JeT Productions – Tim van Leeuwen & Jesper Haverkamp - 2010
Construction
Electrical system
When all electrical components had been received, we made an appointment at Jesper‟s place
to construct the electrical circuit and run some tests. These tests included operating the engine
at full throttle to see how long the batteries would last when fully charged and some weighing
of the components to see if their masses matched those of specifications. Below you will find
an account of our findings during construction of the electrical system.
Electri cal components
Constructing the electrical system wasn‟t
much of a problem, since all components
included a clear manual. The construction
process was straight forward as well. All
components simply had to be linked
together according to scheme. Then we ran
the first test. Results of the endurance test
can be found in the „testing‟ part of this
document.
After having constructed the electrical
system and having done the first engine test,
we had some time left. We decided to get ourselves a scale and weigh the components we
already had. We wanted to achieve two things: in first place we wanted to check the mass we
were given by the manufacturers of components we had received. In second place we wanted
to check if our assumptions of unknown masses of components had been right. Overall the
test turned out pretty dissatisfactory, with most components proving to be heavier than we
thought they would be. Below you find a table showing components‟ masses.
Element
Engine controller
Battery
Servos
Receiver
Propeller
Engine
Wiring
Solar cells 1
Solar cells 2
Frame
Unforeseen
Total
First plan (grams) Actual mass (grams)
7.1
8
175.0
220
11.1
20
14.0
11
5.0
11
36.0
43
10.0
60
76.8
76.8
9.6
9.6
70.0
150
10.4
10.4
425.0
619.8
New plan (grams)
8
50
20
11
11
43
70
120
0
165
2
500
= estimated
41
Research Project – Solar Challenger – JeT Productions – Tim van Leeuwen & Jesper Haverkamp - 2010
In the second column you find data that was shown in the design proposal. It displays masses
we started with during this project. The third column shows the actual masses as measured
during testing. It appeared all components we measured turned out to be heavier, with
batteries, frame and wiring being significantly heavier than assumed. With the total mass
being over 600 grams now, we were forced to think of a new plan.
This new plan was all about saving weight, since 600 grams was way above our maximum
take-off weight. The easiest way to save a lot of weight was changing power source. In the
beginning of the project we decided to go for NiMH-batteries, because we thought they were
more reliable than LiPo-batteries. Because of disappointing results during mass testing we
were forced to go for a LiPo-battery after all.
The decision to use a LiPo-battery brings three drawbacks however. First of all capacity of the
LiPo-battery is smaller, so we won‟t be able to run the engine for as long as we could using
NiMH-batteries. A second drawback concerns the reliability 100 of the power source: LiPobatteries are prone to exploding 101 . We will have to be careful. A third drawback is the need
for alternative charging equipment 102 . LiPo batteries can‟t be charged using regular chargers.
They require equipment dividing power equally over the battery‟s numerous segments.
Still, we decided to continue our testing with the NiMH-batteries. We would build the entire
plane and then replace the battery. Once we changed the power source into a LiPo-battery, we
would attempt to make the plane roll and eventually fly. In this way we keep risks of
something going wrong with the LiPo battery as low as possible.
We wanted a battery as light as possible, yet powerful enough to supply sufficient energy for
our airplane. In the end we found the following 103 :
Conrad energy LiPo Pack
7,4V/ 800 mAh/ 10C
Price: €19.95
Element
Mass
Dimensions
Capacity
Voltage
Plug
Value
38 grams
50 × 30 ×10 mm
800 mAh
7.4V
Mini Tamiya
As shown, voltage of the LiPo-battery is not equal to the voltage of NiMH-batteries.
Therefore we would have to alter the number of solar cells in the wings in order to get an
equal voltage from both the solar cells and the battery. If we don‟t, either the battery or solar
cells will blow up.
100
http://www.norfo lkhelicopterclub.co m/index.php?option=com_content&view=art icle&id =59&Itemid =66
http://www.utahflyers.org/index.php?option=com_content&task=view&id=22&Itemid=28
102
http://www.seven-segments.com/index.php?action=pageshow&id=67&idcat=44
103
http://www.conrad.nl/goto.php?artikel=229994
101
42
Research Project – Solar Challenger – JeT Productions – Tim van Leeuwen & Jesper Haverkamp - 2010
Number of solar cells = 7.5 : 0.5 = 15
In total the solar cells will provide us with 7.5 volts, 0.1 volt more than the LiPo-battery. This
difference will be cancelled out by the Schottky diode, which consumes approximately 0.10.2 volts. After finding out we would now need fifteen solar cells, we had to choose which
type of cells we would use. We will now use big solar cells only, measuring 10 cm by 10 cm.
Fifteen such solar cells would fit in our wings exactly. Still, in order to keep the centre of
gravity in the correct position we would have to put seven solar cells in each wing and one
solar cell in the middle of the wings.
Wing construction
One week after testing the electrical system we met again to start construction of the wings.
First, we decided to manufacture various ribs of the wing, which had to be cut out of a board
of balsa wood. Cutting demanded much
Balsa wood
precision and carefulness, since balsa wood
is very vulnerable and thus can be broken
easily. Because of this the first part of the
afternoon was spent on considering options
to cut ribs, e.g. cutting it with scissors,
sawing it with a fretsaw or cutting it with a
Stanley-knife. After some testing on leftover
pieces of wood, we went for the Stanleyknife, for it proved to be easiest to cut
corners. In addition it turned out to be very
precise.
Since we couldn‟t cut sections randomly, we needed some kind of template. We printed a
model of the wing (page 12) and used it as a template. In the end we were able to construct
twenty solid ribs. We then marked spots where supporting beams would have to be placed.
Since we now finished the ribs and already had the front and rear cornice available, we tried
to visualise the wing. When we laid down all the components of the wing we noticed straight
away that all aligned perfectly. This was greatly satisfying.
43
Research Project – Solar Challenger – JeT Productions – Tim van Leeuwen & Jesper Haverkamp - 2010
That very afternoon we also had some discussion on which rear cornice to use. Originally we
planned to use a cornice measuring 10 by 15 millimetres. Now, we also had a cornice
available measuring 5 by 3 millimetres. Both of us were worried that when using the smaller
one, contact area would be too small for gluing ribs and cornice together. Eventually we used
the smaller one, but, to be able to use this cornice, we would have to make incisions in the
wood in which to glue the ribs. This increased the contact area for the glue.
After cutting ribs, it was time to make incisions in the correct positions.
We started with holes through which we would run wiring for the solar cells and servo engine
(1). This didn‟t prove to be too difficult since the holes didn‟t have to be at an exact position
and could vary in size. We did decide to make only one big rectangular hole instead of the
three holes shown on the picture. Main reason was that cutting such small holes with a
Stanley knife is pretty difficult, while cutting straight went so smoothly that we could easily
manufacture a rectangular hole.
Next, we set out to construct the incisions through which the main supporting beams should
run (2). Making these incisions proved to be way more difficult since more accuracy was
required. All the incisions had to line up perfectly in order to make the wing straight and
uncurled.
We already marked places on each rib where incisions would have to be made (the red dots).
We did so by lining up all ribs, locking them in a clamp and drawing a perpendicular line
across the ribs using a try square. Since not all twenty ribs fitted properly in the clamp, we
split the ribs in two groups, one group of nine ribs for every wing. The two ribs left were put
away to be used as spare parts or test parts later.
After cutting holes, we tried to fit the ribs over the supportive beams. The holes proved to be
too narrow. Some filing made sure the holes became a bit wider, allowing the support beams
to fit neatly.
When fitting the beams, we discovered that the incisions were not deep enough. To
compensate, we made small incisions in the supporting beams. This plan gave the advantage
that the ribs could no longer slide over the supporting beams and we had a larger surface area
to glue the parts together.
Next we had to make the hole for the piston which would connect the aileron to the servo
engine (3). By now we had already ordered the beam, which was made out of carbon, and we
discovered its amazing low mass. It weighed so little, that it would be better to place the servo
engine at the beginning of the wing, eliminating the need for relatively heavy wiring.
44
Research Project – Solar Challenger – JeT Productions – Tim van Leeuwen & Jesper Haverkamp - 2010
Unfortunately the new plan demanded a hole in every rib, so again we fitted the ribs in the
clamp and we drilled a hole at the right place. Again we faced a minor problem: some of the
ribs fractured because the new hole required to be drilled very close to the edge of the rib.
Luckily cracks were only minor, so we could fix the problem with a piece of tape. As a
precaution measure, we used some tape to reinforce the unbroken ribs.
Ri bs, includi ng holes
When we put the beam through the newly drilled holes we discovered that there was too much
friction, because the holes were too small. When neglected, this would possibly result in the
servo engine not being able to turn the aileron. Again we used a file to widen the holes a bit.
The only thing left to do now was think about the ribs between the ailerons. Initially we
planned to cut off a part of them, but still leave the hole for the beam in place. After we saw
the beam was still strong enough without the extra support, we decided to cut the ribs at the
place the closing bar would be placed as shown below. This had the advantage that the
ailerons could be constructed out of a single piece of wood.
Ori ginal plan
New plan
With all ribs finished, we could start gluing the ribs to the supporting beams. This was done
pretty quickly and we soon could start attaching the front cornice and rear cornice as well.
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Research Project – Solar Challenger – JeT Productions – Tim van Leeuwen & Jesper Haverkamp - 2010
The front cornice was glued fairly easy but the rear cornice proved to be time-consuming. It
turned out the ribs didn‟t align perfectly at the back, so we had to make small incisions in the
rear cornice. This gave us the additional advantage that contact surface between the ribs and
the rear cornice drastically increased. After we inserted the beams for the a ilerons, fabricated
closing beams, and measured the ailerons, we had ourselves complete frames for the wings.
Landing gear
With wings completed now, we could think of how we would let the plane stand on its own.
The metal frame accompanying the supplied wheels proved to be far too heavy, so we had to
come up with another solution. By now we had also discovered that when only supported in
the middle, the wings would bend down. We decided to build two small gears underneath the
wings. They would be installed at one third of each wing. In this way the plane would be
supported by wheels during taxiing and supported by its wings during flight. In both situations
forces on the plane are equal and located at the same spot.
Fg
Fg
Fg
Fg
Fg
Fg
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Research Project – Solar Challenger – JeT Productions – Tim van Leeuwen & Jesper Haverkamp - 2010
Wing construction (2)
Still, we had two separate wings. We somehow had to connect the left wing to the right wing,
whilst maintaining structural integrity. We decided to cut off half of both supporting beams in
order to increase surface area. We then glued together both parts and inserted pins into the
beams to create both a glued and mechanical joint. This process is illustrated in the diagram
below.
Tail construction
Construction on the tail started out with a
triangular wooden beam which connects the
tail section to the wings. We then
manufactured the horizontal and vertical tail
section by using a few sticks of balsa wood
as a frame. A small rear wheel had to be
attached to this beam as well. Construction
was easy and fast.
Sequentially, it took us a long time to figure
out how we would have to control the
elevator. We had to think of a way to
convert the circular motion of the servo
engine into the up and down motion of the elevator. Obviously we couldn‟t use the same
system as we did in the wings. Not only there was no space available to mount a servo engine
near the tail, but in addition, mounting the servo engine at the rear would make locating the
centre of gravity even more difficult.
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Research Project – Solar Challenger – JeT Productions – Tim van Leeuwen & Jesper Haverkamp - 2010
Eventually we found out that we would need a so-called push-rod to control the elevator 104 . A
push-rod is a device that links the elevator with the servo engine. It took us a while to figure
out exactly how the push-rod functioned. When we had put it together, we came up with an
alternative idea, which might save some weight. We could replace the push-rod with an
ordinary piece of iron wire. In the end this turned out not to save any weight at all.
When testing the beam connecting the tail and
wings on strength, we noticed the beam gave way
more than we liked. We decided to glue another
triangular beam on top of the one we already used.
With this final adjustment the tail had been
completed.
Work in progress
Fuselage construction
Our plane‟s fuselage is where we would put most
of our electronics. Earlier on we had decided to
construct a balsa wooden frame with a sheet of
wood at the bottom to put all the electronics on. As
we now had expertise on construction using balsa
wood and balsa glue, we knew that just a few
beams would be enough to carry the electronics.
First however, we had to think about where we would want to put all our equipment on the
wooden sheet. It involved some puzzling, because we changed batteries and several wires
proved to be quite short. Secondly, we had to think about how the fuselage‟s interior would
affect the centre of gravity of our plane. After all, our initial plan (see page 28) on positioning
electronics had been changed drastically. We determined placing of all equipment by
balancing the plane on one finger.
Balancing the plane
104
http://www.airfield models.com/ informat ion_source/model_aircraft_hardware/pushrods_and_pull_pull_control
s.htm
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Research Project – Solar Challenger – JeT Productions – Tim van Leeuwen & Jesper Haverkamp - 2010
When the engine runs at full throttle, it will produce quite some thrust, which has to be
transferred to the plane. To accomplish a smooth transfer, we decided to mount the engine to
the plane at two points. One attachment will be connecting the engine to the main beam
running from wings to tail. The other attachment will be between the engine and the sheet of
balsa wood at the bottom of the fuselage.
We do not want to take any risk with the LiPo battery. S ince the near engine regulator can
become very hot 105 , we chose to mount it on the bottom of the wooden sheet. Here it will not
be able to contact the LiPo-battery. In addition, it would be cooled by the airflow generated
by the propeller.
To fix the servo engine regulating the elevator to the fuselage, we had to cut a hole measuring
the exact size of the servo engine in the wooden sheet of the fuselage. First we fixed the servo
engine upside down to reduce drag, but later
Servo in the wing
we chose to mount it straight, since it would
then be easier to fit the push-rod.
With this servo engine in place, we looked at
how to mount the other two servo engines into
the wings. Unfortunately screws available
were too short. Therefore we filed a hole in
the first rib of the wing, just large enough to
squeeze through the heads of the servo
engines. Finally we fixed the servo engines
into position using glue and new screws.
Mylar foil
The plane‟s frame had been completed now. Next steps would consist of putting solar cells in
place and wrapping the wings and tail with Mylar foil. Since Mylar foil was delivered much
earlier than the solar cells, we decided to cover the tail with Mylar foil first. This section of
the aircraft is relatively minor. It was perfect for us to get used to working with Mylar.
We were informed one should apply glue to the ribs and then wrap Mylar around the frame106 .
So we did. By heating the Mylar foil, it was supposed to shrink and wrap itself tight around
the frame. First, we attempted to heat the foil using a hairdryer, but this turned out to not be
hot enough. Though we had read one should use an iron to heat the Mylar foil, we tried the
hairdryer first, since we didn‟t want to damage the Mylar foil. Ultimately we went for the
iron, but we decided to keep some space between the iron and the foil. Even this didn‟t work
out. We finally discovered what really to do. Jesper touched the foil with the iron. Instantly
the foil shrank. We put the iron on the lowest temperature and ironed the foil with it. Using
this technique, we managed to cover the vertical and horizontal tail section with Mylar foil.
105
106
http://www.rctechnics.eu/download/MAN-HM-FLY.pdf
http://www.modelbouwforu m.n l/foru ms/verlijming-constructie/44864-my lar-folie-hoe-verwerk-je-dat.ht ml
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Research Project – Solar Challenger – JeT Productions – Tim van Leeuwen & Jesper Haverkamp - 2010
Ironing Myla r
Before (ri ght) and
after i roning (left)
After this, we could mount the rudder itself. We glued two small wooden segments onto the
aft of the elevator to support the rudder‟s axle. We did have to solve one small problem, since
the tail had deformed slightly under the force of the Mylar foil and was now slightly bent.
With the rudder positioned, we could install the push-rod to attach the servo engine to the
elevator rudder. At the aft we had some trouble mounting the push-rod to the rudder.
Moreover, cutting the push-rod at the right length was extremely difficult. This proved to be a
time-consuming job.
Fi nal resul t
Link between eleva tor and push-rod
Solar cells
Up so far we seemed to be able to keep to our tight planning. Then we hit a major delay
concerning the solar cells. Due to holidays in Germany, they were delivered three weeks late.
Once delivered, we immediately wanted to join all solar cells together. We went about by
soldering them using the soldering strips. This wasn‟t done however before we tested a solar
cell‟s output by using a multimeter. This test really satisfied us, since the solar cell proved to
provide us with an even higher voltage than expected (0.6 volts instead of 0.5 volts).
Although the electric current may still vary, this reading could be considered a good sign.
Another positive finding was that the solar cells turned out to be as heavy as specifications
told us. We were yet another step closer to achieving our goals.
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Research Project – Solar Challenger – JeT Productions – Tim van Leeuwen & Jesper Haverkamp - 2010
Whilst trying to solder the solar cells, we stumbled upon some problems. It appeared the solar
cells couldn‟t be soldered. At first we assumed our old soldering equipment was to blame.
Then, after using state of the art soldering equipment offered by Computer Services Alphen,
we were still puzzled by unconnected solar cells. It turned out ordinary solder tin was not
suitable for soldering solar cells. We would need soldering tin containing silver. We had
nearly bought this expensive substance, when an expert on soldering noted that the strips on
the solar cells had probably been chromed, which implied that they couldn‟t be soldered at all.
Not only did these events consume considerable amounts of time, also this setback meant we
would have to resort to more primitive methods when connecting the solar cells. We figured
out that the easiest way to link all solar cells would be to place wires between the cells and
tape the wires to the cells using duct tape. Before we could do this however, we had to glue
the solar cells to the two supporting beams. Otherwise they would come off when sticking
tape on them.
Drilling new holes
The wires demanded new holes in the ribs, which we
drilled between the front cornice and the first supporting
beam. Wiring all the cells demanded great care since the
cells proved to be extremely fragile.
Another setback occurred when we discovered our
wiring was so stiff, it would rip itself off the solar cells.
Luckily we still had servo extension cables left, as we
had replaced wiring by carbon beams. Those cables
were much more flexible, thus perfectly suiting our
demands.
The new wi ring
When we tested all cells after they were connected, we
found out the circuit wasn‟t complete. One cell had
cracked and thus disconnected the circuit. We solved
this by taking the tape and the wire off the cell and
attaching the wire to the solar cell again behind the
crack. When all solar cells were tested outside, we found
out that the fifteen solar cells produced eight volts, 0.5V
more than we expected.
Last thing we had to do concerning the electric circuit
was to include the Schottky diode in the circuit. Figuring
out which way to mount the diode took some time, since
our multimeter didn‟t function properly. After soldering
the diode into our circuit, the last thing we had to do was
to wrap the diode in duct tape, so our circuit wouldn‟t
shortcut when the diode touched one of the solar cells.
All cells in pla ce
5151
Research Project – Solar Challenger – JeT Productions – Tim van Leeuwen & Jesper Haverkamp - 2010
Mylar foil (2)
With all solar cells and the diode in place, we could finish the wings by wrapping them with
Mylar foil. Because of the experiences we had while applying Mylar to the tail section, this
was done quickly. However, we couldn‟t apply Mylar foil to the wings in one go. First we had
to cover the wing sections at which the ailerons are located, because we could only mount the
aileron itself after these sections had been covered.
We had to choose whether we would literally
wrap the Mylar foil around the wings or
apply two big strips of Mylar foil, one for the
top and one for the bottom half. Eventually
we decided to wrap the wings at the ailerons
sections and to cover the rest of the wings in
two parts. After we had applied the foil, we
heated it with the iron to let it shrink.
Something concerning we noticed, was that
the shape of the wing altered when we ironed
the segments in front of the ailerons.
Because of the shrinking foil, wrapping
around the aileron‟s closing beam too tight,
the wing had become a little dented. Luckily the ironing didn‟t affect the shape of the rest of
the wing.
Finishing off
Finishing off consisted of mounting the wings to the fuselage to create one completed aircraft.
The joint between fuselage and wings is the plane‟s most important joint, since it deals with
the greatest forces in the aircraft.
Before we could mount the wings to the fuselage however, we had to determine the centre of
gravity for both wings and tail. This was done by balancing the fuselage on our fingers. We
knew the wings had to be placed on the fuselage at one third of their chord. Next we had to
check whether in fact it was possible to mount the wing at this position. It turned out not to be
possible to mount the wing in the desired
spot, since wiring for the servo engines
would be too short to reach the receiver. To
fix this problem we positioned the receiver
slightly to the back and moved the wings one
centimetre forward to make sure the servo
engines‟ wiring would reach the receiver.
This action would not be harmful for the
plane‟s centre of gravity, for we could still
alter the centre of gravity a little by
positioning the wheels in the proper place.
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Research Project – Solar Challenger – JeT Productions – Tim van Leeuwen & Jesper Haverkamp - 2010
Once position of the wings on the fuselage had been dec ided, we prepared to fix the wings in
place. First we had to file minor segments out of the fuselage to make sure contact area
between the wings and the fuselage would be as big as possible. Next, we turned the wings
upside down and laid them on the table, so we could glue the fuselage onto the wings. We
applied a good amount of glue to both segments. Still, in order to provide extra strength to the
joint, we wrapped around duct tape as well.
Finally we went to mounting the wheels. We had already decided we would place the wheels
at some distance from each other. In the end we placed the wheels under the fourth rib of each
wing. Because the wings had been covered in Mylar foil by now, we would have to glue the
wheels onto the foil and reinforce them by sticking pins into the wood. However, we still
found the wheels to be unstable, so we mounted them with an extra supporting beam to
prevent them from wobbling forwards and backwards. With these reinforcements in place, we
lifted the airplane and put it on the ground, where it proudly stood on its own wheels, finally
finished. Most important, the plane‟s final mass was 487 grams!!
Wi thout reinforcements
Wi th reinforce ments
Our plane when suspended
53
Test results
Research Project – Solar Challenger – JeT Productions – Tim van Leeuwen & Jesper Haverkamp - 2010
Electrical system testing
During a first test on the electrical system we investigated how long the batteries could keep
the engine running at full throttle. This was the first part of a series of tests in which we
wanted to investigate the difference between using and not using solar cells as an additional
power source. During the second test, we would redo the first test but with solar cells
included. Comparing both runs would give us an indication of the extra flying time the solar
cells provided.
Our first test didn‟t run as smooth as we had hoped for, since the engine shut down abruptly
several times. This was caused by not tightening all wiring very securely due to the test
setting being temporally. Although we had mounted the engine secure ly to a wooden board, a
wire disconnected once in a while. Now and then the engine shut off. After reconnecting the
wiring we were able to continue testing. In the end we found out that using battery supplies
only, the engine could run for about 15 minutes. At this point we still used NiMH-batteries, so
when we would repeat the test with solar cells, we would have to use NiMH-batteries as well.
Unfortunately we hadn‟t received the solar cells yet, so we weren‟t able to run the test with
solar cells immediately. When we had finally received the solar cells, we found that we could
run the test in an alternative way as well. Earlier on, we had calculated that the engine would
consume about 42 watts of power and that the solar cells would produce 21 watts of power
under ideal circumstances. We had also found our solar cells‟ output was 8 volts under
reasonably sunny conditions. The only thing left now was to determine the electric currents
produced by the solar cells. This was done by completing the circuit with the solar cells by
inserting a small light bulb between the wires of the solar cells and measuring the current that
went through it. The current turned out to be only 0.3 Amps in sunny autumn conditions. This
meant:
Power of solar cells = 8V × 0.3A = 2.4W
Using another calculation, we could now find out how much the solar cells would contribute
to the total power supply. First we needed to measure the engine‟s power consumption. We
presume that during flight the engine will run at about 75%, which means that the current is
3.5 Amps, as shown in the table.
Engine speed
No load current
25%
50%
75%
100%
Current (Amps)
0.166
0.513
1.2
3.5
6
Amount of energy supplied by solar cells = 0.3A :3.5A × 100% = 8.6%
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Research Project – Solar Challenger – JeT Productions – Tim van Leeuwen & Jesper Haverkamp - 2010
This value is way under what we had estimated, since we had expected that under ideal
circumstances solar cells would account for 50% of the total energy supply. Still, this setback
didn‟t mean the end of our project. We can still charge batteries using the solar cells when the
plane is on the ground and the solar cells can provide a little extra power during flight. With
the data we gathered, we can also calculate how long it will take to recharge the batteries
using solar energy under reasonably sunny circumstances:
Time to charge = capacity of battery : current of solar cells = 800 mAh : 300 mA = 2.67
hours = 2 hours and 40 minutes.
Charging the batteries for 2 hours and 40 minutes will fully load them and will allow us to fly
for about a quarter of an hour. This is shown through the following calculation:
Flight time= capacity battery : energy consumption= 800 mAh : 3500mA= 0.228 hours = 14
minutes
This would mean that we could fly for about 14 minutes. When we take the solar cells into
account, which we had found out to generate 300 mA, the calculation for the flying time is as
follows:
Flying time= capacity battery : energy consumption= 800 mAh : (3500-300)mA= 0.25 hours
= 15 minutes
Extent flying time = (0.25-0.228) : 0.228 × 100% = 9.6%
Our flight time has been prolonged with 1.2 minutes, which is an extension of 9.6%
Lift test
After testing the electrical system, it was time for a lift test. Initially we had thought of a
construction to place one wing in a K‟nex frame and cycle with it. However, when we
manufactured the wings, we decided to construct the wing segment as a whole. This meant we
had already connected the wings when we installed the solar cells and applied the Mylar foil.
Because of the fragility of the wings it was irresponsible to carry out the initial plan. We were
forced to think of a new plan. We decided to finish the entire plane before performing the lift
test.
Because we would now be testing with the complete and extremely fragile aircraft, we had to
come up with a new setup for testing. Since we didn‟t want to test lift with a moving plane we
needed to perform the test with the plane standing still. This implied we would have to blow
air over the wings. We thought of several options, such as placing the airplane on a big
wooden board which would be placed on scales and then positioning fans in front of the
aircraft. When turning on the fans, we should see a decrease in weight indicated by the scales.
Another option was to hang a force meter from the ceiling and then hang the board under the
force meter. The force meter should show a drop in reading when the fans would be turned
on. In the end however, we did decide to use the force meter, but we made the plane hang
underneath a wooden stick attached to the force meter instead (see picture on following page)
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Research Project – Solar Challenger – JeT Productions – Tim van Leeuwen & Jesper Haverkamp - 2010
We lifted the plane with four belts wrapped
around the wing and the wooden stick. This
would make sure no unnecessary forces
worked on the plane as it hovered. A last
thing to think of was to make sure the plane
wouldn‟t start swinging once the fans were
turned on. We resolved this by fixing a small
piece of wire to a hole in the nose cone.
We still needed to arrange fans. We were
told our school possessed two big fans.
When testing the fans however, we
discovered that maximal wind speed they
could produce was six metres per second, or 21.6 kilometres an hour. This was short of our
take off speed, which is over eight metres per second. Still, at these wind speeds we should
already see some lift.
When setup was finally complete, we could
start testing. First results were disappointing.
At a fairly low wind speed (about two
metres per second) the wings didn‟t seem to
provide any lift. This confirms calculations
on the Reynolds number (see page 15).
Then we increased wind speed (the fans
turned out to accelerate the air to four metres
per second at full power), which showed
some results. In total the wings generated
about 0.4 N of lift, nowhere near the 5 N of
lift we need. However, when we tilted the
aircraft to 15° (maximal angle of attack) we found the wings already generated 1.2 N of lift.
These results were promising, since we found out that not every part of the wings had wind
blowing over it. The fans didn‟t have a range large enough. In addition, the suspension cables
covered several inches of wing. This implied we were only able to use 60% of the wing.
Furthermore, we had assumed the plane‟s speed would be higher at take-off. In fact, we
calculated the speed of our plane would be twice as high as the wind speed produced by the
fans. This would mean that the lift of our wings would be four times as high, since the
variable „speed‟ has a quadratic influence in the lift formula.
1.2 N × 4 = 4.8 N
0.4 N × 4 = 0.8 N
4.8 : 60% × 100 = 8 N (at 15°)
0.8 : 60% × 100 = 1.3 N (at 0°)
After this test we may conclude that our wings should be able to generate e nough lift to let the
plane fly. Only, the angle of attack needs to be bigger than expected. This could be due to the
shape of the wing not being perfectly according to plan, as explained on page 52.
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Research Project – Solar Challenger – JeT Productions – Tim van Leeuwen & Jesper Haverkamp - 2010
Drive test
After the successful lift test, we went on to the next test: driving. The first part consisted of
making sure all controls worked properly and making sure the plane would be remotely
controllable. The test was performed at school, where we showed the plane to our supervisor
and other interested people. However, we couldn‟t perform the actual driving test yet since we
had discovered a problem. Because the wheels were placed some distance from each other,
the middle part of the airplane had slightly dropped, which meant there was very little
clearance between the propeller and the ground. If we would drive at such a speed that the tail
would lift off, we would risk the propeller hitting the ground, possible destroying the
propeller and the aircraft itself.
It was clear an adjustment would have to be
made, which we did by installing a third
wheel in the middle of the plane to support
the fuselage. This adjustment meant that the
propeller now had a clearance of about a
centimetre. In addition, the third wheel was
placed slightly to the front, so risk of the
plane toppling over was largely eliminated.
Putting the plane on the ground had shown
however that the wheels were prone to
movement to the left or right. This problem
was overcome by placing reinforcing beams
to the wheels.
The supporting wheel
With all the problems concerning the landing gear now sorted out, we could perform the drive
test. We had managed to find a fully flat floor, namely the floor of the school‟s auditorium.
This room was large enough to drive the plane without the risk of crashing and was long
enough to drive in a straight line.
During the test we stumbled on some more problems though. It turned out that our plane
didn‟t drive in a straight line. The cause was quickly found. Friction in each wheel had to be
exactly equal in order to let the plane drive in a straight line. This friction could be adjusted
by tightening or loosening the nuts that held the wheels. It resulted in another problem though.
Tightening the wheels too much would make friction too big to let the plane drive. Loosening
the nuts too much in order to decrease friction, resulted in the nuts coming off because of the
vibrations caused by the engine. Whenever the nuts came off, so did the wheels. This sent our
plane spinning several times.
When we had found the right setup, it was time to perform the driving test. It was an absolute
success. With the engine not even at full throttle, we could see the tail coming off the ground,
a first indication of the plane taking off. Luckily, we were able to catch this moment on
camera (see page 65).
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Research Project – Solar Challenger – JeT Productions – Tim van Leeuwen & Jesper Haverkamp - 2010
Flight test
With the first three tests now completed and all results suggesting that our plane is capable to
fly, it was time to get airborne. Weather conditions made us postpone the maiden flight
several times. Eventually, on the 3rd of March 2010, flight JET001 was ready for take-off.
After having made some adjustments on the wheels and doing some checks on controls, we
hit our last problem. One of the ailerons malfunctioned, probably due to a fractured joint
between its axle and the servo engine. We had to keep this aileron in place through tape.
Steering the aircraft could only be done now using the sole remaining aileron.
We gently opened throttle,
made the airplane role and
then opened throttle fully.
Within seven metres the
plane took to the skies,
reaching an approximate
altitude of six metres. Then
the nose pitched up, the
aircraft stalled and crashed
just moments after take-off.
Initially we were greatly satisfied. Our hard work had paid off, our calculations, predictions
and constructions had been correct. Later we started wondering why the aircraft stalled so
quickly. There were two possibilities: either the plane‟s centre of gravity had been shifted too
much to the back or the plane was steered into a stall position.
It appeared we are to blame for the
aircraft‟s crash. In order to not let
the propeller hit the athletics track
used as a runway, we ordered the
rudder to push the plane‟s nose up
as much as could be. Being so
excited by the plane actually taking
off, we forgot to move the rudder
into neutral. The plane steered itself
into stall position. Disaster was
inevitable.
Another noticeable fact was the
aircraft taking off so quickly. It had
not yet reached a speed anywhere near the 8.3 metres per second required. When looking at
the formula for lift, this situation can easily be explained:
L = ½ × c ×  × A × v2
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Research Project – Solar Challenger – JeT Productions – Tim van Leeuwen & Jesper Haverkamp - 2010
Analysis showed the angle of attack was about twelve degrees at take-off, whereas in our
calculations we had assumed it would be one degree. At twelve degrees the lift coefficient is
1.12, compared to 0.36 at one degree. In addition, when taking off, head wind speed was
approximately two Beaufort, which corresponds to 1.7 metres per second. This results in:
Take-off speed = √(½-1 × 1.12-1 × 1.23-1 × 0.32-1 × 4.88) – 1.7m/s = 3.0 m /s
Off course the Reynolds formula (page 15) predicted we cannot fly at speeds lower than 3.8
metres per second. It should be noted that the velocity mentioned above is the ground speed.
The airspeed is the plane‟s groundspeed, plus its headwind. For our take-off situation this
would be 4.7 metres per second. That would perfectly be possible according to the Reynolds
formula.
The noticeable difference in angle of attack therefore explains why our plane took to the skies
so quickly. Moreover, the angle of attack might have been even higher than the angle used in
calculations. Namely, the angle of attack is said to be zero degrees in the following
situation107
We assumed zero degrees would be the following situation.
This would imply the values used for the angle of attack in all our previous calculations were
too low, which would confirm an ever lower take off speed.
In the end, the low flying speed and high angle of attack turned into a devastating stall and
crash. Luckily damage was only minor and mostly concerned the landing gear. Most
important after all: our solar powered plane had taken off.
107
http://marlongofast.tripod.com/zipped_aeronotes/clarky.ht m
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Research Project – Solar Challenger – JeT Productions – Tim van Leeuwen & Jesper Haverkamp - 2010
Conclusion
It is now time to draw conclusions. Extensive tests and respective calculations showed our
model aircraft is capable of flying, even partly solar powered. Tests also showed the wings are
capable of producing the desired amount of lift. Furthermore, observations showed the engine
is capable of propelling the aircraft to take-off speed. Most satisfying of course was the
moment when the plane truly took off.
One conclusion we can draw is that purely solar powered flight is impossible. In theory the
maximum power our solar cells can produce is 21 watts, nowhere near the 40 watts required.
Unfortunately our solar cells produced far less than the 21 watts they were meant to produce.
Main reason for this is Dutch climate. Moreover, difficulties in connecting the solar cells
contributed to power loss as well. Therefore flying on solar cells only is not possible. At the
most, solar cells will lengthen flight with 10%. When used as a charger for the battery, it will
take the cells two hours and forty minutes to fully load the battery. Maybe in future solar
cells‟ efficiency will be higher. For now, technology is not advanced enough.
A second conclusion concerns the weight aspect. With the solar cells already having a mass of
120 grams, it was extremely difficult to not exceed our target mass of 500 grams. Current
solar cells have a power to weight ratio far too low. In order to fit the number of solar cells
required, we were forced to cut weight on many other elements. In the end, we managed to
create a plane weighing in at 487 grams, but the aircraft was extremely fragile.
A third conclusion is that it is impossible to fly a solar powered plane using NiMH-batteries.
This power source proves to be too heavy. The current battery pack in our airplane, a LiPo
battery, weighs about 40 grams, whereas the original NiMH-battery pack weighed 225 grams.
That is nearly half the mass of the entire plane! Even though LiPo batteries bring considerable
risks with them, it still is the best option for our aircraft. One simply needs to be very careful
when handling the plane.
A fourth conclusion is that our methods of testing worked well and our calculations and
expectations have been correct. Especially the lift test gave results we expected. Although the
angle of attack needed to be bigger than expected, the wings still generated enough lift. This
confirms formulas we used have been both correct and accurate. Moreover, provided data has
been correct. Also we constructed the wings in a proper way. Therefore tests results were
satisfying.
The most satisfying test was of course when the aircraft truly took off. Cheer went up as we
realised our assumptions, calculations, measurements and constructions had been correct. But
most satisfying after all was that the plane took off completely balanced. Analysis showed the
aircraft took to the skies at a far lower speed than expected due to factors like wind and the
angle of attack. Sadly the aircraft‟s fragile frame didn‟t fully survive the crash landing.
A final conclusion we can draw is that even though they can‟t be used to entirely power
aircraft, solar cells are a serious option when trying to extend flight times of airplanes. As we
have seen, solar cells can keep our plane in the air for a nine percent longer period of time.
60
Research Project – Solar Challenger – JeT Productions – Tim van Leeuwen & Jesper Haverkamp - 2010
However, we can pose the question whether the weight savings following the exclusion of
solar cells wouldn‟t have had the same effect, since the plane would have been much lighter
without solar cells. In future projects further research could be done on this topic.
Last of all it should be noted that this version of our model aircraft is only the first version to
be built. This project has, more than anything, learned us a lot about building model aircraft
and has provided us with valuable experiences to use in future projects.
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Research Project – Solar Challenger – JeT Productions – Tim van Leeuwen & Jesper Haverkamp - 2010
Evaluation
Our research project has provided us with numerous experiences and insights to be used later
when constructing a better, second version of our plane. Our experiences and insights include
knowledge about what materials we should have used, what should be done differently and
which parts of the plane we could have upgraded.
What should be done different, what didn’t go as well as could be?
Weight savings
Mass of our aircraft has been a key factor in the project. Put simply, we have been trying to
save weight on every part of the plane. In the end, we have been pretty successful in doing so,
but there are some aspects of the plane on which more weight could have been saved.
First of all, we could have saved quite some weight on the two supporting beams in each
wing. Initially we decided on using triplex beams as girders. While constructing the wings,
now being familiar with the strength of balsa wood, we decided to use balsa wooden beams
instead. They saved us relatively much weight, while proving to be strong enough as well.
When connecting the ailerons to the servo using a carbon beam, we found out that we should
have used yet another type of material instead. We could use these carbon beams to replace
the supporting balsa beams, as they are as strong as balsa beams, but weigh half as much.
The carbon rods can also solve another problem concerning the wings. Since the balsa beams
were not long enough to run over the full length of the wings, we were forced to build each
wing individually and then glue the both of them together. The joint between the two wings
proved to be a very fragile one. Using two long carbon rods will eliminate the need of making
a joint at all.
Talking of the frame, we have to note that a more realistic estimation of masses should be
made at the start of the project. In the beginning we didn‟t exactly know what the mass of
balsa wood was. We estimated the frame would eventually weigh 70 grams. When the plane
was finished though, we ended up with a frame weighing nearly 160 grams.
The frame wasn‟t the only part of the plane that was heavier than expected. Numerous
components, such as the engine, batteries, propeller, engine controller, servo engines and
wiring turned out to be heavier than expected or promised. In future projects we should be
more pessimistic about components‟ masses, which would result in solely positive findings
rather than mostly negative findings.
Structural improvement
Because we did our utmost best to save weight, we might have pushed it a bit too far on some
aspects of the plane. This affected the strength of the plane. During lift test we noticed that
our tail looks pretty fragile, especially at high wind speeds. The rudder does seem to function,
but the tail section can only be described as wobbly. The connection we made between tail
section and wing is a bit too weak.
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Research Project – Solar Challenger – JeT Productions – Tim van Leeuwen & Jesper Haverkamp - 2010
A second structural improvement is the landing gear. During the design of the plane we
hardly spent any attention on the landing gear. This proved at the end of the construct ion
phase, when we were faced with the problem of what to do with the landing gear. We
managed to construct a suitable landing gear but it wasn‟t actually up to its job. This was
demonstrated when our plane crashed during its test flight. After the crash most damage was
done to the landing gear. Besides, we suffered a minor lapse in concentration whilst mounting
the wheels. This resulted in us placing one wheel slightly more forward than another. It
shouldn‟t be a real problem, but as mentioned before, our plane tends to drive in a curve. The
placing of the wheels might have to do with this.
Second of all, suspension of the wheels could have been more secure. Because we didn‟t have
enough nuts and bolts at our disposal, we mounted two wheels using pins. This resulted in the
wheels getting into a tilted position easily, thus creating more friction. Using bolts of the right
dimension on every wheel would have increased the stability of our plane and would have
reduced friction.
A third improvement involving the landing gear is making sure distance between wheels and
suspension is wide enough. Currently we put a piece of balsa wood between the wheel and the
supportive structure. The wooden parts separate the wheels from their suspension, but
dramatically increase friction. Instead, we could have used some of the tubing left over from
the push-rod to maintain distance between wheels and supporting structure. This would have
resulted in significantly lower drag and increased stability.
A last improvement to the wheels, is to make the wheel supports higher, in order to give the
plane a bigger ground clearance. This would eliminate the need to construct a third wheel
(thus adding extra mass and friction) and would make it safer to drive the plane.
A final structural improvement has to do with materials available. As we had to build the
plane all by ourselves and in our own house, we didn‟t have every material and tool at our
disposal. Because of this we had to resort to using pins and other „primitive‟ materials. If we
would have had more materials available, we might have been able to manufacture a more
rigid aircraft.
Solar cell improvements
Our plane‟s solar cells can also be improved in several ways. When doing our project, we
discovered how fragile solar cells are. Unfortunately we learned by failure. During our project
several pieces of solar cell cracked, due to too much pressure being exerted on the cells. This
might have resulted in the cells supplying a far lower current than the 3300 mA they should
have provided according to specifications. Solar cells we used simply were too fragile.
Next time we should consider using a different type of solar cell. The high-performance cells
we used are originally designed to be placed on cars or in glass solar panels; places where
they would have had support all over. We just had two supporting beams. This resulted in a
serious amount of pressure being exerted on the cells. In future we could use solar which are
more flexible and fracture less easily. Currently those cells are not available.
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Research Project – Solar Challenger – JeT Productions – Tim van Leeuwen & Jesper Haverkamp - 2010
A second method to provide more support for the solar cells is to simply add more supporting
balsa wood or use a different construction material. Some model planes are built using a sort
of polystyrene foam to fill up spaces between the wooden frame. In future projects this
method should be used. It will allow the solar cells to be laid onto the foam. Another proposal
is using a different airfoil. The wings should have a flat rear on which to put the solar cells.
A second improvement of our solar cells is the connection between them. We faced problems
with soldering and had to resort to connecting solar cells with ordinary tape and wire. This
wire seems to disconnect occasionally, thus stopping the electrical circuit. Tape blocks some
of the precious sunlight as well. Next time we should go for soldering strips Lemo Solar
offers. This will result in better connections between cells.
Cost savings
Another aspect of the project we could have improved on, was the cost aspect. After the
project we still had numerous materials left we hadn‟t used at all. Not all balsa wood we
bought was used for example. The final costs of this project are:
Element
Balsa
Glue
Engine controller
Propeller
Shipping costs
Battery holder
Landing gear
LiPo battery
LiPo balancer
Diode
Belts for testing
Costs (€)
41.09
10.16
16.95
3.35
54.96
3.50
22.95
19.99
12.99
1.12
4.95
TOTAL
515.00
Element
Battery (NiMH)
Receiver
Servos
Wiring
Engine
Remote control
Switch
LiPo charger
Solar cells
Mylar
Pushrod
Costs (€)
8.95
13.50
30.00
7.80
14.50
59.00
5.95
29.99
135.00
6.00
12.30
Parts that cost a lot were accessories for the LiPo-battery. Initially we planned on using a
battery balancer when charging the LiPo-battery, but when the battery was charged, we found
out it either didn‟t work or was unnecessary. Charging can be done without a balancer,
although it drastically shortens the battery‟s life expectancy.
Another part we didn‟t use was the adapter, which would transform the 230V mains into 12V.
When we received the adapter however, it turned out 230V mains was not transformed into 12
volts, but into 8 volts. We had to send back the adapter and resort to using a car battery
charger. Although we did get our money back, we had to pay shipping costs.
The remote control and receiver also gave us some problems. We wanted to order a separate
controller and receiver, but when the receiver had been delivered, we discovered we would
need a crystal to place in the controller and receiver. It turned out the easiest way of getting a
pair of crystals was to order a set containing a controller, a receiver and a pair of crystals. This
left our initial receiver unused.
64
Research Project – Solar Challenger – JeT Productions – Tim van Leeuwen & Jesper Haverkamp - 2010
Another financial improvement is the shipping costs. During the project we ordered materials
from several companies in several stages. Of course we intended to order all materials at the
same time, thus having to pay only once. However, as we needed several unforeseen parts
such as the LiPo battery, ordering was done in several stages. We can save quite some money
on shipping costs next time, as we now know which elements are really needed.
Test improvements
Last part of our research project that could be improved, is testing. Improvement mainly lies
in the lift test. We went about it as well as we could, but still it wasn‟t a very professional
setup. It would have been better if we had been able to test the plane in a wind tunnel, using a
device producing smoke, so we could take a look at the airflow. However, we didn‟t have a
wind tunnel at our disposal and arranging one would have been very expensive.
Or so we thought. Thinking „it is always worth a try‟, we sent an e-mail to the faculty of
Aerospace Engineering at the TU Delft in which we presented our finished Solar Challenger.
In the e-mail we requested using one of the faculty‟s wind tunnels. A bit to our own
amazement the faculty replied by stating that „the use of the wind tunnels for these purposes
can rarely be accepted. However, since our project looked very complete and we even had a
complete prototype, the faculty was happy to make an exception for us‟. Because our Solar
Challenger would need to be tested in the biggest wind tunnel, which has a full schedule until
July, we‟ll have to wait some more time to perform this test. This will give us the opportunity
to fix the plane after the crash during the test flight.
A second improvement for testing, is the time of the year. As this project was finished in
October, we had to deal with Dutch autumn weather during testing. This especially affected
the test concerning the solar cells‟ output, because the angle of the sun‟s rays in autumn
differs from the angel in summer and the sun‟s rays aren‟t as intense either. For this reason we
can‟t say for sure what the solar cells‟ maximum output is. Besides, recharging the battery in
summer will take less time than recharging during autumn.
Another improvement to be made when measuring the cells‟ output, is to have a light meter
available. Using such a device enables us to draw a graph about voltage and current produced
by the solar cells under various light intensities. Right now we can only describe weather as
„sunny‟, „cloudy‟ or „reasonably sunny‟.
Camera data
A last setback we encountered during test phase had to do with our camera footage. We
filmed all tests we ran, including the plane‟s driving test. Video footage would have enabled
us to show fragments of video in our presentation. Furthermore it contains the evidence of the
existence of our plane in case something bad happens to it. However, even though we
explicitly requested the TOA to put the video on computer immediately, it didn‟t happen.
When we returned after bringing home the plane, we discovered video recordings were lost.
They were erased by accident.
65
Research Project – Solar Challenger – JeT Productions – Tim van Leeuwen & Jesper Haverkamp - 2010
What we nt well?
We have seen quite some elements to improve during our research project. On the other hand
we also came across several techniques and designs which we think should definitely be
repeated in future projects.
Mylar foil
One of the absolute successes of this project, is the use of Mylar foil. When we received the
roll of foil, we thought we could have used kitchen foil as well. It was only when we applied
the foil when surprise came in. We were especially shocked when Mylar foil turned out to
shrink so well when being heated by an iron. Mylar foil is one of the key factors in the
success of the project.
Wing shape
Another good design used in our project, is the airfoil. Our choice to use a „Clark-Y‟ wing
profile has been a very good one, for numerous reasons. First of all, the ribs of the wing were
relatively easy to construct when compared to other airfoils. Second of all, the ribs connected
well to the front and rear cornice and proved to be strong. Our wing frame together with the
Mylar foil has proven to generate enough lift, thus sending our plane skywards.
Engine & propeller
The choice for an engine was a very difficult one, especially due to so many types being
available. This choice we made turned out to be a very good one. The engine fits nicely in the
frame, the propeller has the correct ratio with the frame and the engine doesn‟t consume too
much power. More importantly though, the engine is capable of propelling our aircraft to high
speeds.
Controls & steering
Controls are one of the most crucial aspects of the plane, since the plane is helpless without
them. After extensive research, a suitable receiver and remote controller had been found. Both
function properly. We haven‟t tested yet what the maximum distance between the remote
controller and the receiver can be, but it certainly is more than 100 metres.
The servo engines turn out to function properly as well. We had some small concerns about
the servo engines‟ torque, but it turned out all servo engines are capable of tilting the ailerons
and elevator. One small drawback is that one of the ailerons slightly drops once in a while due
to gravitational forces. Luckily this can be corrected easily.
Using carbon rods is a very good way of connecting servo engines with ailerons and is a good
way to save weight. Also the push-rod is a good solution to control the rudder. Although
installing is quite tricky, it works well. Moreover, the push-rod looks professional.
Last of all, the engine controller we used also functioned properly. We haven‟t had any
problems dealing with heat production or too high currents going through.
66
Research Project – Solar Challenger – JeT Productions – Tim van Leeuwen & Jesper Haverkamp - 2010
Our opinion
The past months, especially the past weeks, we have been working intensely on this project. It
has been a great challenge to us. Setbacks occurred on a daily basis and delays were
unavoidable. Still, we eventually managed to attain our goals.
This project has, more than anything, taught us lots about building model aircraft and
provided us with valuable experiences to use in future projects. We didn‟t construct a €500.plane, we gathered €500.- of knowledge and we are very satisfied with all results.
Last of all, this project has been an absolute success. Not only has it been great fun building
the plane, the reactions to the project have been overwhelming and Solar Challenger even
managed to pick up a prestigious price at our school. The whole project was a great
experience but of course, there was one moment that stood out specifically: the airplane
taking off. It was simply breathtaking.
67
Research Project – Solar Challenger – JeT Productions – Tim van Leeuwen & Jesper Haverkamp - 2010
Additional sources
Report writing:
http://www.ruf.rice.edu/~bioslabs/tools/report/reportform.html
Research project discussion on fuel savings for commercial aircraft, including on solar panels
http://www.wetenschapsforum.nl/index.php?showtopic=94691&pid=466140&st=0&
Solar powered model aircraft built by students from Puerto Rico:
http://www.youtube.com/watch?v=uzu2Y2kbPZw&feature=related
http://ceic.pupr.edu/html/Capstone/HybridWings/index.html
Students attempting to build a solar powered model aircraft as a research project:
http://www.modelbouwforum.nl/forums/electro-vliegtuigen/66600-modelvliegtuig-opzonnecellen-pws.html
Building the frame of a model airplane:
http://anjo.com/rc/aircraft/elder/
http://www.airfieldmodels.com/information_source/how_to_articles_for_model_builders/con
struction/wing_construction/index.htm
http://picasaweb.google.com/jaspapens/Charter#5154316415791691170
http://plans.rcmodell.hu/planelect.html
About model flying:
http://www.mvccrash.nl/overons/00000097940bbf72d/
Forum:
http://www.circuitsonline.net/forum/view/66253
http://www.modelbouwforum.nl/forums/accu-laad-techniek/69411-batterij- laden-dmvzonnecellen-2.html
Technical tips:
www.amcor-modelbouw.nl
68
Research Project – Solar Challenger – JeT Productions – Tim van Leeuwen & Jesper Haverkamp - 2010
Acknowledgements
Solar Challenger was a success. Still, completing our project would not have been possible
without the efforts, support and help of the following people, companies and organizations:











F. Hidden, our advisor. Though he was quite skeptical about feasibility of our project, he
approved with our ideas and plans. His critical thinking and expertise prevented us from
making unnecessary mistakes and taking inaccurate steps.
R.J.W. Haverkamp, Jesper‟s father. He provided us with all equipment we needed for
construction. This included tools and several instruments.
P.A. van Leeuwen, Tim‟s father. He helped through critical think ing and cooperation. His
tips and hints appeared to be pretty constructive. Moreover, ordering components abroad
would not have been possible without his credit card.
I.M. Prange and L.C. van Staveren, Jesper‟s and Tim‟s mothers. They were willing to
transport our fragile plane to and from testing locations. In addition they supported other
logistics and finances.
R. van der Laan, for providing us with his LiPo battery charger and safety equipment.
Lemo Solar, a German supplier of electronics. They gave us €24 discount on the solar
cells.
Athletics Club Startbaan, whose track was available as a runway for our plane.
TU Delft, for the usage of the lay out and style as far as the report and presentations are
concerned.
Computer Services Alphen aan de Rijn, for using all of their soldering equipment.
A.Ch. van Steen, for donating €15 to stimulate progress and development of our solar
powered plane.
All people from Modelbouwforum.nl and circuitsonline.net, for all their useful tips.
69
Research Project – Solar Challenger – JeT Productions – Tim van Leeuwen & Jesper Haverkamp - 2010
Jesper‟s log
Day
Date
Wednesday
01-04-09
Thurs day
02-04-09
Friday
03-04-09
Saturday
04-04-09
Sunday
05-04-09
Wednesday
08-04-09
Thurs day
09-04-09
Friday
10-04-09
Sunday
Wednesday
Saturday
Wednesday
Monday
12-04-09
15-04-09
18-04-09
22-04-09
27-04-09
Wednesday
29-04-09
Sunday
17-05-09
Wednesday
Tuesday
Thurs day
10-06-09
16-06-09
18-06-09
Start
time
17:00
19:00
10:15
17:00
19:00
11:30
10:45
11:35
16:00
18:30
13:55
End
time
18:00
21:00
11:15
18:00
21:00
11:45
11:30
11:50
18:00
19:30
14:10
Total
time
1
2
1
1
2
0.25
0.75
0.25
2
1
0.25
18:15
10:00
12:00
17:00
14:00
19:00
17:00
19:00
18:45
10:30
13:00
17:15
15:30
20:00
18:00
21:45
0.5
0.5
1
0.25
1.5
1
1
2.75
8:45
17:30
9:00
13:30
16:00
13:30
10:00
13:00
10:00
14:00
14:00
17:00
13:30
10:30
11:45
9:15
18:00
11:00
15:30
19:00
16:00
12:00
16:00
12:00
16:00
15:30
18:00
15:30
11:00
12:45
0.5
0.5
2
2
3
2.5
2
3
2
2
1.5
1
2
0.5
1
Description
Orientation on subject (websites universities, forum, etc.)
Orientation on subject (decision: solar challenger)
Discussion about subject (decision on solar challenger)
Information on feasibility (engine, solar panels)
Information on feasibility (propeller, balsa wood)
Discussion with Mr. Hidden
Looking up information on costs (solar panels, engine)
Discussion about subject (time, costs, size)
Possibilities of electrical system (servo, battery, engine)
Possibilities for construction (wood, glue, foil)
Consultation on possibilities (Who will do what? Jesper:
wing construction, loading batteries. Tim: Wireless
system, servo engines)
Possibilities of the wing (construction of frame, foil)
Take a closer look at wing design (Clark Y)
Take a closer look at electrical system (batteries)
Determine planning and research questions
Discuss electrical system (also on forum)
Read tips on forum and execute them
Found new engine and parts
Made a list of electrical equipment, made a list of
requirements
Drawing a scheme of electrical system
Writing on documentation
Update website
Start research proposal
Determine airfoil
Work on research proposal
Work on research proposal
Work on research proposal
Work on website
Work on research proposal
Work on research proposal
Work on research proposal
Work on research proposal
Work on research proposal
Work on research proposal
70
Research Project – Solar Challenger – JeT Productions – Tim van Leeuwen & Jesper Haverkamp - 2010
Monday
Wednesday
22-06-09
24-06-09
09-07-09
18-07-09
10:30
10:30
18:45
8:30
10:30
20:30
15:00
11:00
13:00
19:15
9:45
13:00
22:00
18:00
0.5
2.5
0.5
1.25
2.5
1.5
3
Thurs day
25-06-09
Thurs day
Sunday
Tuesday
21-07-09
14:15
17:45
3.5
Thurs day
Friday
23-07-09
24-07-09
15:00
10:15
11:00
16:30
10:45
13:30
1.5
0.5
2.5
Saturday
Saturday
Saturday
Sunday
Thurs day
Saturday
01-08-2009
08-08-2009
15-08-2009
16-08-2009
20-08-09
22-08-09
14:00
14:00
9:00
10:00
19:30
14:00
17:15
17:00
12:00
13:00
20:00
18:00
3.25
3
3
3
0.5
4
Monday
Wednesday
Thurs day
24-08-09
26-08-09
27-08-09
14:00
8:30
13:30
17:00
10:45
16:30
3
2.25
3
Sunday
30-08-09
17:00
16:45
17:15
17:45
0.25
1
Tuesday
01-09-09
20:00
21:00
1
Thurs day
Monday
Thurs day
Sunday
Thurs day
Saturday
03-09-09
07-09-09
09-09-09
20-09-09
24-09-09
26-09-09
19:00
10:30
21:30
10:00
14:00
19:00
20:00
13:00
22:30
13:00
16:30
21:30
1
2.5
1
3
2.5
2.5
Sunday
27-09-09
19:00
22:30
3.5
Monday
28-09-09
15:15
18:15
3
19:00
20:00
1
16:30
18:30
2
Tuesday
29-09-09
Work on research proposal
Round off research proposal
Round off research proposal
Round off research proposal
Round off research proposal
Order various components, update website
Unpack components, read manuals, connect components,
test them
First test electrical system (engine & batteries), check
mass of components
Research on new battery, solar panels and mass savings
Catch up with report
Investigation about Mylar, diode and other materials yet
to order
Start construction of wing
Continue construction of wing
Continue construction of wing
Continue construction of wing
Purchase carbon beams & push-rod in Amsterdam
Continue construction of wing + investigate push-rod
elevator
Construction of tail
Put wings together, start construction of fuselage
WeCo time: Continue construction of tail, wheels,
fuselage
Ordering batteries and final equipment
Making adjustments to engine mounting + preparing
wiring and electronics for new battery
Sending back wrong adaptor, testing LiPo battery charger
and components
Purchase rear cornice + supporting wooden beam
Continue construction
Spelling check + catch up with research project file
Apply Mylar + finish elevator & push-rod
Attempt soldering solar cells
Second attempt to solder solar cells, no results, silver tin
needed.
Drilling new holes, gluing solar cells, connecting wire to
cells with tape
Soldering diode, finishing wiring, testing voltage,
applying Mylar and ailerons
Soldering diode, finishing wiring, testing voltage,
applying Mylar and ailerons
Applying Mylar to wing
71
Research Project – Solar Challenger – JeT Productions – Tim van Leeuwen & Jesper Haverkamp - 2010
Wednesday
30-09-09
Thurs day
01-10-09
Friday
02-10-09
Saturday
03-10-09
Sunday
04-10-09
Monday
05-10-09
Tuesday
06-10-09
Wednesday
07-10-09
Thurs day
08-10-09
TOTAL
19:00
22:00
3
13:30
15:30
2
16:00
10:00
19:00
8:30
20:00
9:30
16:00
19:00
9:00
11:00
17:00
19:00
17:00
19:00
17:00
19:00
17:30
19:00
17:00
10:30
19:30
12:00
22:00
12:30
18:00
22:00
10:00
13:00
18:30
22:15
18:30
23:15
18:30
01:30
18:30
23:30
1
0.5
0.5
3.5
2
3
2
3
1
2
1.5
3.25
1.5
4.25
1.5
6.5
1
4,5
156
Gluing landing gear, determining centre of gravity,
gluing fuselage, wings and rudder together
Transporting plane to school, showing it at school, testing
controls
Installing new gear, doing final checks
Arranging equipment for testing
Setting up frame for testing
Lift test, drive test
Spelling check + catch up with research project file
Working on file
Working on file
Working on file
Working on file
Testing solar cells' profit
Working on file
Working on file
Working on file
Working on file
Working on file
Working on file
Working on file
Working on file
72
Research Project – Solar Challenger – JeT Productions – Tim van Leeuwen & Jesper Haverkamp - 2010
Tim‟s log
Day
Begin
time
Wednesday 01-04-2009 13:45
End
time
16:00
Total
time
2.25
19:45
20:00
0.25
20:00
21:00
1
10:15
11:15
1
20:00
21:00
1
11:35
11:50
0.25
18:00
19:00
1
Thurs day
Friday
Date
02-04-2009
03-04-2009
Saturday
04-04-2009
13:55
14:10
0.25
Sunday
05-04-2009
20:00
20:30
0.5
Tuesday
07-04-2009
9:45
10:15
0.5
Wednesday 08-04-2009
13:30
16:00
2.5
Thurs day 09-04-2009
Friday
10-04-2009
Wednesday 15-05-09
Wednesday 22-05-09
Wednesday 20-05-09
9:00
10:50
13:30
13:30
13:30
9:15
11:05
16:00
16:00
16:00
0.25
0.25
2.5
2.5
2.5
22:15
9:00
10:30
22:30
10:15
11:00
0.25
1.25
0.5
Wednesday 10-06-2009
13:30
16:00
2.5
Wednesday 24-06-2009
Thurs day 25-06-2009
10:00
10:00
13:00
13:00
3
3
18:00
15:45
18:30
16:30
0.5
0.75
Thurs day
Friday
Friday
Sunday
Monday
21-05-09
22-05-09
22-05-09
28-06-2009
29-06-2009
Description
Introduction to research project, explanations on
possibilities and brainstorming on topic
Telephone call with Jesper, idea of solar powered
airplane
Orientation on topic, look at possible materials and
parts, look up information, check out others ideas
Discuss findings with Jesper, brainstorm on topic, come
up with topics to be investigated
Look at feasibility of project, focussing on solar cells,
mass and engine
Discuss finding, determine size of aircraft, discuss first
materials
Search for materials and parts on the internet, look at
engines, look at forums
Telephone call with Jesper, divide first tasks for
looking up information. Tim will focus on controls,
Jesper on wings & electrical system
Orientation on controls, search the internet for
possibilities and available materials/parts
Discuss findings on ways of controls and number of
solar cells. Determine aimed mass
WeCo-time, report topic, look up parts together,
investigate battery overload problems, post questions
on forums and look at answers
Look at further answers on forum
Catch up with log
WeCo-time: Work on research proposal
WeCo-time: Work on research proposal
WeCo-time: Work on research proposal, step three
(engine, batteries, propeller & solar cells)
Catch up with log
Work on research proposal, step three (controls)
Work on research proposal, step four (determining final
mass & size)
Work on research proposal, finish step four and start
step six (placing of solar cells)
Work on research proposal, step seven (design of wing)
Work on research proposal, step seven (design of wing)
and finishing of research proposal
Research on international aspect of project
Research on international aspect of project
73
Research Project – Solar Challenger – JeT Productions – Tim van Leeuwen & Jesper Haverkamp - 2010
Tuesday
30-06-2009
Wednesday 31-06-09
Thurs day 01-07-2009
Friday
02-07-2009
Sunday
19-07-2009
20:00
22:30
9:30
10:15
19:00
19:45
20:30
8:00
11:15
13:30
15:30
11:00
17:30
22:15
23:00
10:00
10:30
18:30
23:15
23:15
9:30
11:45
15:30
15:45
11:45
18:15
2.25
0.5
0.5
0.25
1.5
3.5
2.75
1.5
0.5
2
0.25
0.75
0.75
18:45
19:00
0.25
20:30
22:15
1.75
Tuesday
21-07-2009
14:15
17:45
3.5
Tuesday
28-07-2009
19:15
22:00
2.75
Thurs day
Saturday
Saturday
Saturday
Sunday
Monday
30-07-2009
01-08-2009
08-08-2009
15-08-2009
16-08-2009
17-08-2009
15:15
14:00
14:00
9:00
10:00
13:30
15:45
17:15
17:00
12:00
13:00
15:45
0.5
3.25
3
3
3
2.25
16:15
16:45
0.5
Friday
Saturday
21-08-2009
22-08-2009
11:15
14:00
11:45
18:00
0.5
4
Monday
Tuesday
Wednesday
Thurs day
24-08-2009
25-08-2009
26-08-2009
27-08-2009
14:00
22:00
8:30
13:30
17:00
22:15
10:45
16:30
3
0.25
2.25
3
Friday
28-08-2009
15:45
17:00
1.25
03-09-2009
05-09-2009
07-09-2009
20:00
20:30
20:00
10:30
19:00
20:30
20:45
20:30
13:00
20:30
0.5
0.25
0.5
2.5
1.5
Thurs day
Sunday
Monday
Work on international aspect of project
Work on international aspect of project
Work on international aspect of project
Research lending solar cells
Research on international aspect of project
Work on international aspect of project
Work on international aspect of project
Work on international aspect of project
Work on international aspect of project
Research / work on international aspect of project
Start spelling & grammar check
Work on international aspect of project
Work on international aspect of project (spelling &
grammar check)
Work on international aspect of project (spelling &
grammar check)
Work on international aspect of project (spelling &
grammar check)
First test electrical system (engine & batteries), check
mass of components
Adjust 'construction' part in the research project
document after test, research Mylar
Buy beams at Praxis
Start construction of wing
Continue construction of wing
Continue construction of wing
Continue construction of wing
Work on 'construction' part in the research project
document
Work on 'construction' part in the research project
document
Send e- mails concerning solar cells and Mylar foil
Continue construction of wing + investigate push-rod
elevator
Construction of tail
E- mail for information on Mylar foil
Put wings together, start construction of fuselage
WeCo time: Continue construction of tail, wheels,
fuselage
Look for suitable sponsors, E- mail ASN + Triodos for
sponsoring
Order Mylar foil
Order solar cells
Look at Schipholfonds as a sponsor
Continue construction
Update construction report
74
Research Project – Solar Challenger – JeT Productions – Tim van Leeuwen & Jesper Haverkamp - 2010
Monday
Tuesday
Wednesday
Sunday
14-09-2009
15-09-2009
16-09-2009
20-09-2009
21-09-2009
16:30
22:45
13:15
10:00
21:30
19:15
16:45
23:00
13:30
13:00
22:00
20:45
0.25
0.25
0.25
3
0.5
1.5
Monday
Thurs day
Monday
24-09-2009
28-09-2009
14:00
15:15
16:30
18:15
2.5
3
19:00
20:00
1
29-09-2009
16:30
19:00
18:30
22:00
2
3
Wednesday 30-09-2009
13:30
15:30
2
15:30
10:00
16:30
8:30
13:00
17:00
10:30
17:30
12:00
16:00
1.5
0.5
1
3.5
3
16:00
18:45
2.75
19:30
21:30
2
21:30
10:15
22:00
13:00
0.5
2.75
16:45
17:45
1
06-10-2009
16:30
17:45
1.25
Wednesday 07-10-2009
10:15
17:00
19:00
21:00
14:00
11:30
18:30
21:00
0:30
15:30
1.25
1.5
2
3,5
1,5
139,25
Tuesday
Thurs day
01-10-2009
Friday
Sunday
02-10-2009
04-10-2009
Monday
Tuesday
Thurs day
TOTAL
05-10-2009
08-10-2009
E- mail school for information on finances
E- mail solar cell supplier for information on delivery
E- mail school for information on moving the deadline
Apply Mylar + finish elevator & push-rod
Update construction report
Update construction report + start spelling & grammar
check on research project document
Attempt soldering solar cells
Solder diode, finish wiring, test the voltage of solar
cells, apply Mylar to end of wings, install ailerons
Solder diode, finish wiring, test the voltage of solar
cells, apply Mylar to end of wings, install ailerons
Apply Mylar to rest of wing
Glue landing gear, determine centre of gravity, glue
wings, fuselage and rudder together, charge battery
Transport plane to school, show the plane, bring plane
back home
Install extra wheel, do final checks on plane
Arrange equipment for lift test
Film plane while driving, think of set-up for lift test
Perform lift test, drive test
Catch up with adjustments to research project
document, check spelling and grammar
Work on 'construction' part in the research project
document
Work on 'construction' part in the research project
document
Check international aspect
Work on testing part and media attention part in
research project document
Write conclusion for research project document + add
new data in testing part
Write about media attention, Start with evaluation in
research project document
Continue evaluation in research project document
Continue evaluation in research project document
Finish conclusion and evaluation
Order sources, finish logs, check document
Working on file
75