Design Projects Other Pages Contact

AE 301 Design Project Fall 2000 For Dr. Tom Gally College of Engineering Embry-Riddle Aeronautical University, Prescott Arizona December 4, 2000 Induced Efforts Edgar Orsi Filho Kreg R. Voorhies Jeff Ballenski Chris Matsuno

1. Objective

Design, build and test an aerodynamic vehicle capable of efficiently lifting a 200 gm payload when traveling at a velocity of approximately 73 ft/sec (dynamic pressure of approx. 5.2 psf). The goal of the design is to lift the payload weight and vehicle weight while producing the least possible drag.

2. Concepts

The basic layout of the model was chosen for maximum lift to drag ratio and ease of construction. Because the test flow would be low subsonic, we chose not to sweep the wings. The design requirements did not call for roll stability, so no dihedral angle was used. We did consider winglets, but chose to go with a full 16” wingspan instead.

The airfoil was selected using the Airfoil Comparison Tool on the web at: http://soaring.cnde.iastate.edu/calcs/frames.shtml

The polar graph shown below was generated using this tool. Out of the airfoils available, the MA409 and S6063 had the lowest drag at about C_l = 0.2. The NACA 2414 is shown here for comparison. The S6063 was slightly better and easier to construct, so we chose to use the Selig S6063 low Reynolds number airfoil as our wing cross section.

To design the wing dimensions, we fixed the lift coefficient at 0.2 and the span at 16 in. We estimated the total weight to be about 0.55 lb. The Wing Vortex program was used to estimate the span efficiency to be about 0.992. Using the equation:

We found AR = 3.35, c = 4.78 in. The result was checked using the lift equation.

Reduced Reynolds number is a way to factor out the velocity dependence of the Reynolds number. According to the information on the website, the reduced Reynolds number is given by:

Inserting RRe = 75648 and C_l = 0.2, we got Re = 1.69 x 10⁵. Using the equation for Reynolds number we estimated the Reynolds number at test conditions to be about 1.58 x 10⁵. The numbers are close enough to validate the graph data. Since the polar graph is taken from wind tunnel data based off our wing span, area, and weight, we assumed that the drag shown is total drag. Note that our estimated drag came directly from the graph and did not include any allowance for the payload and tail structure.

Because the airfoil is 7.05% thick, there was not enough thickness to hide the payload inside the wing. We also needed to attach a tail surface to provide the required yaw stability. The twin boom layout provided good structural support for carrying the payload behind the wing. To minimize wetted area, we opted not to construct a fuselage or fairing around the weight. Since we had no numerical method to determine the appropriate tail area and distance behind the wing, those dimensions were “eyeballed.”

3. Construction

Allowable materials:

· Wood

· Glue

· Fishing String

· Masking Tape

· Paper

Materials used:

· Wood

· Glue

Table of Materials	Material	Use
	Balsa Wood	Wing Spar
		Wing Ribs
		Tail Sections
		Tail Booms
		Leading edge
		Trailing edge
		Payload Cradle
	1/64” Balsa Wood Sheet	Airfoil Cover
	Glue	Assembly

Construction of wing

1) Build template of airfoil.

2) Build wing ribs and sand them to match template.

3) Build wing spar to hold wing ribs.

4) Build leading edge and trailing edge and sand them to match template.

5) Glue ribs and spar to the leading edge and trailing edge.

6) Cover the airfoil with 1/64” balsa wood sheet.

7) Finish fit and sand airfoil to match template.

Construction of tails

1) Construct template.

2) Rough cut balsa to templates

3) Streamline edges.

Construction of tail booms

1) Rough cut to size specifications

2) Cut slits for tails

3) Taper top edge to match bottom of airfoil

4) Smooth edges and streamline

Assembly

1) Insert tails into slits in tail boom and secure with glue

2) Glue booms to wing structure

3) Glue payload cradle between tail booms

Picture 1. Bottom View of the wing without the tails

Picture 2. View of the wing ribs and spar

Picture 3. Right View of the wing

Picture 4. Isometric View of the wing

Picture 5. Top View of the wing

4. Estimated Calculations

Design Requirements
Payload Weight	Wp = 0.200 Kg	0.441 lbf
Dynamic Pressure	q = 1.000 inH2O	5.197 Psf

Wing Characteristics
Span	b = 16.00 in
Chord	c = 4.78 in
Area	S = 76.41 in^2
Aspect Ratio	AR = 3.35
Airfoil Thickness (S6063)	7.05%	0.33667 in

Weight Approximation
Approximate Wing Volume	V1 = 20.58 in^3
Approximate Structural Volume	V2 = 1.00 in^3
Total Approximate Volume	V = 21.58 in^3
Approximate Balsa Wood Density	Rhob = 16.00 lbf/ft^3
Model Weight	Wm = 0.200 lbf
Total Weight	W = 0.641 lbf
Performance Estimation
Coefficient of Lift	CL = 0.232
Span Efficiency	e = 0.993
Coefficient of Drag	CD = 0.009
L/D ratio	L/D = 25.8

5. Wind Tunnel Results

Experimental Data
Total Weight	W = 279 gm
Dynamic Pressure	q = 1.000 inH2O
Normal Force	N = 324 gm
Lift	L = (610 gm – 324 gm) = 286 gm
Wind Tunnel Drag with model	D = 54 gm
Wind Tunnel Drag without model	D = 31 gm
Total Drag	DT = 23 gm
L/D ratio	L/D = 12.4
Angle of Attack at L = W	a = -0.6 degrees

Experimental Calculations
Coefficient of Lift	CL = 0.229
Coefficient of Drag	CD = 0.0184

Picture 6. Wing in the wind tunnel

Picture 7. Wing during the wind tunnel testing

Picture 8. Another picture of the wing during the wind tunnel testing

6. Conclusion

Our project was found to be below expectation, the anticipated L/D was 25.8, the coefficient of lift was 0.232, and the coefficient of drag was expected to be 0.009. Our actual results from the experiment were, L/D of 12.4, a coefficient of lift was calculated at 0.229, and the coefficient of drag was calculated as 0.0184.

From this data we concluded that the drag coefficient was much higher than anticipated. The tail section and the payload support were not estimated for initial drag calculations. This was most likely the reason our preliminary calculations varied from the actual data.

Further improvements on our project would include, redesign of the tail section, redesign of the payload support. We also found that we would be able to reduce the overall wing area, to decrease induced and parasite drag associated to oversized wing structures.