Which wing?

What factors affect the aerodynamic properties of an aeroplanes wing?

How does camber affect speed of an aeroplane?

How does camber affect sink rate of an aeroplane?

How does section thickness affect speed of an aeroplane?

How does section thickness affect sink rate of an aeroplane?

How does angle of attack affect speed of an aeroplane?

How does angle of attack affect sink rate of an aeroplane?

How does the position of a wing tip affect speed of an aeroplane?

How does the position of a wing tip affect sink rate of an aeroplane?

Background theory

Lift is created by the pressure difference created on the upper and the lower surfaces of the wing. This is because the air moving above the wing has a further way to travel to reach the trailing edge of the wing than the air moving under the wing, so creating a lower pressure above the wing.

Because the air moving over the wing has a further way to travel, it moves faster than the air moving under the wing. When air moves faster it becomes less pressurised and so creating the pressure difference above and under the wing.

Things that affect amount of lift produced:

Wing surface area and flying speed. The bigger the surface area and the higher the speed the more lift is produced.

The camber of the section is the curvature of it. The higher the camber the more lift is produced because the air has to travel further over the wing so creating less pressure above the wing.

Camber is the maximum distance between the chord line and the mean line. The chord line is a straight line from the leading edge to the trailing edge. The mean line is an equidistant line from the top and bottom of the aerofoil.

Section thickness is the thickness of the thickest part of the wing. The higher the section thickness the higher the lift. Generally increasing the thickness also increases the stalling rate, which is the angle at which the air behind the wing becomes turbulent with a sudden reduction in lift. The higher the camber or section thickness of the wing the more drag there is.

A by-product of lift is drag. Drag is how much an object pushes against air or how much force an object needs to move at a certain speed through the air.

The angle of attack can also affect lift and speed. The angle of attack is at what angle the wing sits on your aeroplane. We measure this from the foremost point of the wing to the rearmost point of the wing. The higher the angle of attack (The higher the front of the wing compared to the back) the higher the lift up to a certain point when the wing stalls.

Plan form is the geometry of the plane. (Nose, tail, wings, tailplane etc.)

Wing tips reduce drag by stopping the vortex of air swirling around the wing. You get tips that face up and tips that face down.

All of the above are theoretically correct.

Sink rate is measured in horizontal distance over vertical distance. If sink rate is low, then an aeroplane can travel a longer distance without falling out of the sky.

Apparatus

Aeroplane, launcher, stopwatch, testing ground, measuring tape

Testing procedure

We built an aeroplane that had detachable wings. We used an aerofoil called the HQW. We then changed the camber but left the section thickness the same. We changed the section thickness but left the camber the same. We then chose the HQW 3,5 - 9 to test the angle of attack and the wing tips. We increased the angle of attack and used wing tips facing up and tips facing down.

Independent variable: Section thickness

 Section thickness Camber 1 8% 2,5% 2 14% 2,5%

Independent variable: Camber

 Section thickness Camber 1 9% 1,0% 2 9% 3,5%

Independent variable: Angle of attack

 Section thickness Camber Angle of attack 1 9% 3,5% 4° 2 9% 3,5% 6°

Independent variable: Wing tips positioning

 Section thickness Camber Wing tip position 1 9% 3,5% Up 2 9% 3,5% Down

Controlled Variables

Wind, Aspect Ratio, Launching angle, temperature, weight, aerofoil shape, launching force.

Measurement

Time in air, distance travelled.

Precautions

Wind, launch angle, launch force and air pressure should be controlled.

Results

Raw data tables

HQW 1,0 - 9

Camber: 1,0% Section thickness: 9%

### Sink rate: 0,16 m/m

HQW 3,5 - 9

Camber: 3,5% Section thickness: 9%

 Time (sec) taken to touch down Distance travelled to touch down while falling 4,23m vertically (m) 7,66 44,4 8,63 55,4 7,56 43,8 7,75 46,5 7,4 43,8 7,4 43,2 8,28 42,4 8,16 49,8 Average: 7,85 Average: 46,16 Speed: 5,88 m/sec Sink rate: 0,09 m/m

HQW 2,5 - 8

Camber: 2,5% Section thickness: 8%

 Time (sec) taken to touch down Distance travelled to touch down while falling 4,23m vertically (m) 4,15 26,2 4,09 26,0 4,31 26,4 4,10 24,9 4,37 26,43 4,19 25,89 4,53 26,82 Average: 4,24 Average: 26,09 Speed: 6,15 m/sec Sink rate: 0,16 m/m

Graphed Results

Results of investigation into the effect of camber on speed.

Results of investigation into the effect of camber on sink rate.

Results of investigation into the effect of section thickness on speed.

Results of investigation into the effect of section thickness on sink rate.

Results of investigation into the effect of a angle of attack on speed.

Tables showing all results

Section thickness

 Section thickness (%) Mean time to travel (sec) Mean distance travelled (m) Speed (m/sec) Sink rate (m/m) 8 4,24 26,09 6,15 0,16 14 5,32 31,98 6,01 0,13

Camber

 Camber (%) Mean time to travel (sec) Mean distance travelled (m) Speed (m/sec) Sink rate (m/m) 1,0 4,08 25,65 6,14 0,16 3,5 7,85 46,16 5,88 0,09

Angle of attack

 Angle of attack ( ° ) Mean time to travel (sec) Mean distance travelled (m) Speed (m/sec) Sink rate (m/m) 4 4,96 31,39 6,33 0,13 6 4,60 27,99 6,08 0,15

Wing tip positioning

 Wing tip position Mean time to travel (sec) Mean distance travelled (m) Speed (m/sec) Sink rate (m/m) Up 5,22 33,72 6,46 0,12 Down 5,46 36,40 6,66 0,14

Conclusion

Increasing camber decreases sink rate and decreases speed.

Increasing section thickness decreases sink rate and decreases speed.

Increasing angle of attack increases sink rate and decreases speed.

Wing tips facing up decrease sink rate and decreases speed.

Wing tips facing down increase sink rate and increase speed.

Suggestions for further investigation

We will test a much bigger spectrum of factors such as aspect ratio and plan form.

Significance

Model aeroplane designers or racers can see from our results what profile to use for speed or lower sink rates. They can also see what effects different types of wing tips have on speed and sink rate. We are also testing if the theory is correct.

Bibliography