1. Solar-cell voltage-current observations and graph
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SOLAR PANEL CHARACTERISTICS |
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Voltage |
Current |
Power |
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volts |
amperes |
watts |
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0 |
0.752 |
0.00 |
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0.25 |
0.746 |
0.19 |
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1.8 |
0.710 |
1.28 |
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2.34 |
0.675 |
1.58 |
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2.95 |
0.662 |
1.95 |
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3.25 |
0.660 |
2.15 |
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3.68 |
0.631 |
2.32 |
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4.06 |
0.630 |
2.56 |
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4.59 |
0.600 |
2.75 |
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5.03 |
0.564 |
2.84 |
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5.23 |
0.541 |
2.83 |
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5.76 |
0.491 |
2.83 |
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6.08 |
0.446 |
2.71 |
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6.41 |
0.396 |
2.54 |
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6.83 |
0.319 |
2.18 |
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8.2 |
0.000 |
0.00 |
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2. Model Weight and Balance
The object of the weight and balance is to find a good starting position for attaching the wing on the fuselage. The cg of the completed model should be 6.25 cm (2.5 inches) aft of the wing leading edge, according to the scaled model drawing.
Note that the ARM below is measured (positive is toward the rear) from a Datum on the fuselage side about 8.7 cm behind the propeller. Xle is the ARM of the wing leading edge.
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Model Weight and BalanceTable |
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Component |
Mass |
Arm |
Mass x Arm |
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g |
cm |
g.cm |
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fuselage |
77.94 |
22.3 |
1738.062 |
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wing |
108.52 |
8.3 |
900.716 |
+108.52 Xle |
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H. Tail |
10.35 |
96.5 |
998.775 |
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V. Tail |
4.65 |
86.9 |
404.085 |
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Wheels |
7.3 |
1.5 |
10.95 |
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Prop |
4.56 |
-8.7 |
-39.672 |
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Total |
213.32 |
Equating |
4012.916 |
+108.52 Xle |
=213.32 (Xle+6.25) |
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Solving : Xle = 25.6 cm |
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From this table, the wing should be mounted with its leading edge 25.6 cm aft of the fuselage Datum.
3. Wiring Wing Solar Power Connections
4. Aircraft Design Targets
Weight
a) Battery Powered model design target for weight= 0.4 g/in2 (source: www.skyhooks.ca)
b) Our design obtained the following:
Wing area S:
S = 22.5 x 7.125 + [12 ( 5.5 + 7.125)]/2
= 160.3 + 151.5= 311.8 square inches
Airplane Mass = 213 g
Wing Loading: M/S = 213/311.8 = 0.68 g/in2
This exceeds our Target by 70%. The reasons for this are thought to be those documented here.
The design target was based on battery-powered or rubber-powered model experience.
The solar panels had to be soldered together and solder is lead-based and very heavy.
The solar panels had to be mounted on balsa for attachment to the wing structure and that attachment required spray glue in addition to the weight of the balsa itself.
Full span wiring was required to tie the solar panels to the motor and receiver and copper tape was needed to join the panels to each other.
Thrust
The Static thrust of the model, in bright sunlight, was measured at 53.2 g. The Thrust to Weight ratio achieved for the model was thus 0.25 and hence our objective was achieved.
