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## Design of Airfoil and Problem-Solving Using FoilSim Answers

Step 1. Set the velocity to 50 mph and record the lift. Increase the airspeed slider to 100 mph. Record lift. Increase the velocity to 150 mph and record lift again. Finally increase the velocity to 200 mph and record lift. Describe the change that you observe in lift as velocity changes. Graph lift vs. velocity.

 50 mph 100 mph 150 mph 200 mph Lift =505 Lift =2022 Lift =4550 Lift =8089

As velocity doubles, lift quadruples.

Step 2. Return to the Reference condition and select the "Stall Model". Set the angle at 2.5 and record lift. Repeat, setting the angle for 5.0, 7.5, and 10 and record lift for each setting. Graph the results. Complete your graph with a stall at an angle of 12. Will lift be generated at an angle of 0? No Explain.  Symmetric airfoil (camber = 0) has symmetric flow field and generates no lift at angle = 0.

Step 3. Return to the Reference conditions. Set the surface area to 100 sq.ft. Record the value for lift. Double the surface area. How is lift affected? Record lift. Double surface area two additional times and record lift. Graph lift vs. surface area from the data recorded. Explain how an airplane can slow its velocity for landing and still maintain sufficient lift to avoid a stall.

 Surface Area=100 Surface area=200 Surface area=400 Surface area=800 Lift =2696 Lift =5393 Lift =10786 Lift =21572

Step 4. Return to the Reference conditions. Set the camber at 0. Record lift. Increase camber to 6.25, 7.5, 8.75, 10.0, 11.25, and 12.5 and record the changes in lift for each setting. Graph lift vs. camber with the data recorded. Is it possible for camber adjustment to initiate a stall? Explain.

 0 6.25 7.5 8.75 10.0 11.25 12.50 Lift =8089 Lift =28537 Lift =32626 Lift=36714 Lift =40806 Lift =44889 Lift =48975

Step 5. Return to the Reference conditions. Adjust the altitude slider to 15000 ft., 25000 ft., 35000 ft., and 45000 ft. and record lift at each setting. Graph lift vs. altitude with the data collected above and predict the next two points on the graph. Is lift affected by an increase in altitude? List possible reasons for any changes observed.

 15000 feet 25000 feet 35000 ft 45000 ft Lift =5910 Lift =4212 Lift =2914 Lift =1810

Step 6. An airplane is beginning its descent at an altitude of 1500 ft. and a beginning velocity of 200 mph. Gradually decrease altitude and velocity and note the change that occurs in lift. Record your observations. Explain how the lift force can be maintained while velocity and altitude are being decreased as the airplane approaches landing. Check your explanation using the FoilSim demonstrator. Summarize your results.

Discussion must include angle of attack and camber.

Step 7. An airplane travels 40,000 feet horizontally from the point where it began its descent at an altitude of 1500 feet. Draw a diagram of the descent showing the vertical and horizontal components, and calculate the angle of descent for the airplane.

Angle of descent = 2o

### FOILSIM APPLICATION ACTIVITY

Design and build a paper airplane that has the longest time aloft and travels the greatest distance.

Step 1.
Use unlined paper for your construction. Determine the wing area by breaking areas of the wings down into triangles and rectangles. Measure and calculate.

Step 2.
Using the same launch angle and velocity, fly your airplane through five trials. Measure the wing surface area, distance traveled, and angle of inclination for the wings in each trial. Make a data table and record your results. Repeat the trial flights for time aloft. Again, record the wing surface area, time aloft, and angle of inclination for the wings in each trial. Graph the area/time or area/distance data for each set of trials. The trial flights must be completed indoors to eliminate wind effects.

Step 3.
Write a summary of your results.

Step 4.
Cut one inch off the trailing edge of the wings. Place the cut off pieces within the folds of the airplane so the mass remains constant.

Step 5.
Repeat the trial flights, data collection, graphing, and written summary as above.

### EXTENSION ACTIVITY

Design and construct airplanes with other wing shapes. Repeat the steps of the preceding activity for each design. Provide a written discussion comparing all results.