2. Verslag
bij de integrerende opdracht
ontwerp, bouw en vlieg een papieren modelzweefvliegtuig
Naam Nick Beentjes Studentnr. 500715585
Naam Jeroen Berends Studentnr. 500703406
Naam Glenn De Decker Studentnr. 500705423
Naam Marnix van der Galien Studentnr. 700502957
Naam Bart Savenije Studentnr. 500704428
1. Geef een beschrijving van jullie conceptuele ontwerp, inclusief een beschouwing
over de functie en de vorm van jullie vliegtuigje. Leg een verband tussen de
ontwerpeis voor een zo lang mogelijke vliegtijd en de ontwerpparameters.
The main objective of the assignment is to design and build a glider which can use the potential
energy as efficient as possible and convert said force to kinetic energy to conserve height,
staying aloft as long as possible. The Kinetic or speed energy is converted into lift by the airfoil,
consequently reducing the rate of which height is lost. The actors considered to contribute to the
maximization of the distance traveled are:
• the shape of the wing
• the aspect ratio
• the aircraft weight
• the aircraft shape
Considering these factors, low weight, a sleek aircraft body and using a thin wing profile with a
high aspect ratio will maximize the gliding distance. Designing our sail plane we opted for a wing
root structure at the center of the body. The wings are connected through a wing truss (figure 1)
and the empennage is connected by a single beam (figure 2), enforced by the aircraft
monocoque structure ensuring structural integrity. The long wings are high in aspect ratio and
are mounted in dihedral to facilitate positive stability. The rudder and elevator are attached to the
skeleton through two incisions to insure sound attachment to the structure. (figure 3)
Figure 1: Wing root structure Figure 2: Beam structure Figure 3: Empennage
3. Using the straws to build beams for the wing, we opted to cut the straws in half to save weight,
which ultimately reduces the amount of lift needed and the induced drag that is created. This will
increase the strength of the structure and increase the gliding distance of the sail plane.
The monocoque structure is also designed to use the least amount of paper as possible and
using a sharp nose cone, we are able to reduce the form drag in the front of the aircraft.
2. Geef een overzicht van jullie fysische berekeningen, te beginnen met een VLS van
jullie vliegtuig tijdens de vlucht. Laat zien hoe jullie het vliegtuigje in evenwicht
houden.
Before we can make balance calculations, the centre of gravity of the aircraft has to be
assessed. For stable flight it is important that the centre of gravity lies in front of the wing. When
a stall occurs the aircraft’s nose decreases in angle of attack providing an increase in speed and
will recover from the stall. For the substantiation of the calculation of the centre of gravity,
please refer to the annex. According to the calculations shown in the annex, that the centre of
gravity lies at 0.00307 meters referenced from the middle of the aircraft in front of the wing.
In order to maintain a balanced flight, lift should equal weight. Furthermore the moment of the lift
of the wing should equal the moment of the downforce of the stabilizer to prevent undesirable
rotations around the lateral axis.
One can see that this is indeed the case with our aircraft in the free body diagram shown in the
annex. The wings of the aircraft are designed so that lift equals weight (further information
regarding wing design can be found in ‘opdracht 3.3’.) To prevent the aircraft from rotating, the
following equation should be applied :
Ideally this equation equals zero, however if this equation cannot equal zero for practical
reasons, it is desirable that the result of this equation is a little below zero. This means that the
moment of the down force is slightly greater than the moment of the lift, which results in a
clockwise rotation around the centre of gravity. Thus, a slight upward pitch. A counter clockwise
rotation is less desirable, as our wing Is angled at zero degrees geometrical angle of attack.
Thus if a downward pitch is used it would position the wing at or below the point of zero effective
angle of attack.
Filling our design parameters into the equation,
yields:
4. Note that the result of the equation is below zero but negligible.
5. 3. Geef een toelichting op het aerodynamische ontwerp, inclusief berekeningen van de
benodigde afmetingen van vleugel en staartvlakken.
For our aerodynamic design we have chosen for an angle of incidence of zero degrees. This
angle of attack give a CL-value of 0,4375, according to the wind tunnel lab with a Clarck Y-14
profile (shown in the CL graph). Shown in the CL/CD graph, an angle of incidence of zero
degrees gives the lowest value. The lift force is calculated by approximating the mass the aircraft
in order to maximize the flight distance.
With the CL value the wing area can be calculated:
T = 20 degrees = 293 degrees Kelvin ; Standard temperature of 287 in degrees Kelvin
Atmospheric pressure = 99.600 Pascal ; Air density; Rho: 99600 / (287*293) = 1,18443115
kg/m3
Lift = total weight = 0,365057 N ; Speed = 5,5 m/s ; CL = 0,4375
S (Wing area needed): S = 0,365057 / (0,5*1,18443115*5,5^2*0,4375) =0,04657763 m2.
Ultimately we opted for wings that are 40 cm long and 6 cm wide on both sides. This leads to a
total wing area of 0,048 square meters. Using this configuration the aircraft has more wing area
than that is needed, resulting in a smaller loss of altitude as speed decreases. The wings are
square shaped, with high aspect ratio, ensuring the least amount of resistance. The tail section is
8 by 3 cm giving a total area of 0,0024 m2. This generates a negative lift of:
L = 0,024 * 0,5*1,18443115*5,5^2*0,4375 = 0,018810247 N
The nose of the glider is shaped in such a manner that the aircraft is as sleek as possible
decreasing the parasitic drag.
6. 4. Geef een toelichting op het constructief ontwerp, inclusief bouwschetsen.
The paper aircraft is based on modern gliders. When looking at the aircraft design from above, a
slight water drop shape is apparent. The building materials used are: 80 g/m2 paper, plastic
straws and glue. The sailplane was designed with a wing root structure at the center of the
aircraft with as a backbone, a single straw that runs from the wing root to the empennage.
Ensuring a strong wing, a vertical straw is placed every 29mm glued perpendicular to the
horizontal straw that runs from the wing root to the wing tip as shown in the schematic. To save
weight the wing spars are ¼ diameter of a straw. The stabilizer is constructed in a similar way;
however the spars are placed 14mm apart and mounted to a separate wing root structure similar
to the main wing root.
5. Wat is het geschatte gewicht van jullie ontwerp? Beschrijf hoe jullie dit hebben
vastgesteld.
We approximated the weight of the glider, by calculating the weight of the paper that will be used
to construct the airfoil and fuselage. The straws where bundled and weighed to calculate the
weight of a single straw. Using this data we calculated the amount of material needed and
entered these values into excel to find the total weight of the aircraft. Taking the glue into
consideration, which accounts of 45% of the total weight, we estimated the total weight of the
aircraft to be 0,3650 Newton. The weight of the wing is calculated per 10 cm. To approximate the
total weight of the wing this must be multiplied by the total wing length. These calculations can
be found in the appendix.
