My Goals for this project:

• Improve the controls

• Increase the wing-span

• Reduce the drag

• Improve the picture quality of the onboard DVR, e.g., Vibration-isolation, and keep the prop out of the FOV.

• Use the Smart Tunnel to test and improve the design before the test flight.

Main-wing design

What I will do:

• Test the performance of the original airfoil of the Fox-Glider

• Choose an airfoil shape for the extended wing section.

• Test the final wing (original + extended part) if the design increased the total wing performance (L/D, Cl/Cd)

Constraints:

• The airfoil cord should be 90mm

• Normal flight speed will be ~10m/s. Hence, Low-Re# of 60K to 100K and probably high AoA ~7deg.

• The mounting angle of the new wing section should be aerodynamically matched to the original wing section.

• The pitch moment should be less than the elevator surface's maximum torque.

• I estimate that the upgraded model will weigh around 160[gr].

The airfoils that might work for this project are:

• Trainer60

• SG6043

• SG6041

• SD7037D

• SA7036

• SA2035

• Avistar

• BW-3

• Geo417A

• PT-40

Calculations:

Givens:

Re = V*L / u link

Lift = 0.5*p*Cl*V^2*A link

Re - Reynolds number

Lift - The lift force of the wing [N]

p - Fluid (air) density [Kg / m^3] = 1.225 kg/m3 @300K -< 25DegC

Cl - Lift coefficaint (from airfoil datasheet or wind-tunnel measurements)

A - Wing area [m^2]

V - Air velocity [m/s]

L - Referance lenght (airfoil cord) [m]

u - Fluid (air) kinematic viscosity = 1.57e-5[m^2/s] @300K -> ~25DegC

Model weight = 0.16[Kg]

Cruising speed = 10[m/s]

Wing area = 0.6*0.09 -> A=0.054[m^2]

Re = (10 * 0.09) / (1.57*10^-5) -> Re=57K (For normal flight)

0.16*9.8 < 0.5 * 1.225 * Cl * (10^2) * 0.054 -> Cl > 0.47 @10[m/s] Re=57K (Normal flight)

0.16*9.8 < 0.5 * 1.225 * Cl * (7^2) * 0.054 -> Cl > 0.94 @7[m/s] Re=40K (Slow flight) 

0.16*9.8 < 0.5 * 1.225 * Cl * (6^2) * 0.054 -> Cl > 1.3 @6[m/s] Re=34K (Landing)

0.16*9.8 < 0.5 * 1.225 * Cl * (5^2) * 0.054 -> Cl > 1.8 @5[m/s] Re=28K (Maybe possible with flaps)

After examining the results, I narrowed down the airfoil list to two:

• SG6043 - Good for high lift force at cruise speed of >10[m/s]

• Geo417A - Good for high lift force at slow speed of <10[m/s]

3D Printing

Assembly

Wind-Tunnel tests

Results for 4.2[m/s] air-velocity

+-6.4deg produces ~+-9[N*mm]. Similar to 3.4[gr] weight placed at the tail (9000/270/9.8 = 3.4[gr])

Results for 7.5[m/s] air-velocity

+-6.4deg produces ~+-23[N*mm]. Similar to 8.6[gr] weight placed at the tail (23000/270/9.8 = 8.6[gr])