DEVELOPMENT AND TESTING OF A CHANNEL WING MODEL AIRPLANE
Wade M. Spurlock Mississippi State University
Outline o o
Assumptions Blick Theory o Static Case o Five Components of Lift o Lift Coefficient
o o o
Design Motor Testingg Channel Fabrication
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Channel Wing Model Airplane
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Assumptions o o o
Subsonic Incompressible Adiabatic
Wade Spurlock
Low Flight Speeds, Takeoff and Landing Ref. 3
Channel Wing Model Airplane
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Blick Theory o o
Static-case channel lift Five components of lift o Upper surface of channel o Lower surface of channel o Pressure differential on channel o Wing minus channel o Vertical thrust component
o
Overall lift and lift coefficient
Ref. 1
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Channel Wing Model Airplane
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Static Case: V∞= 0 m& = ρ AeVe L = mV & esinε
Ref 2 Ref.
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Ref 1 Ref.
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Lift: Channel Section o Upper Surface:
* q S LCU = 1−η CLC d C
o Lower Surface:
* q S LCL =ηCLC ∞ C
⎛ ⎜ ⎜ ⎜ ⎝
⎛ ⎜ ⎜ ⎜ ⎝
⎞ ⎟ ⎟ ⎟ ⎠
⎞ ⎟ ⎟ ⎟ ⎠
o Pressure Difference: L = q − q∞ S cosα P C d where: Ref. 1 q = dynamic pressure 1 ρV 2 2 S = planform area d = conditions at propeller disk (upper channel) ∞ = freestream conditions CL* = unpowered lift coefficient η = the fraction of lift provided by the lower surface of airfoil α = span-average span average angle of attack Wade Spurlock
Channel Wing Model Airplane
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Lift: Outboard Wing and Thrust * q S LW = CLW ∞ W
LT = nT sin(α +ε ) ≈ nT sinα Ref. 1
where: W = outboard wing n = number of engines T = thrust α = angle of attack ε = downwash angle
Wade Spurlock
Channel Wing Model Airplane
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Lift: Total L = 1−η ⎛ ⎜ ⎜ ⎜ ⎝
⎞ ⎟ ⎟ ⎟ ⎠
⎛
⎞
* q S +ηC* q S + ⎜⎜ q − q ⎟⎟ S cosα CLC LC ∞ C ⎜⎝ d ∞ ⎟⎠ C d C
⎛ ⎞ * ⎜ +CLW q∞SW + nT sin ⎜α +ε ⎟⎟ ⎝ ⎠
R f 1 Ref.
Case of zero thrust (qd = q∞) : * q S + C* q S L = CLC ∞ C LW ∞ W * = C* = C* ): L = C* q S With constant airfoil (CLC LW L L ∞ Wade Spurlock
Channel Wing Model Airplane
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Coefficient of Lift: CL Vd 1 ⎛⎜ ⎞ = ⎜⎜1+ 1+ CT ⎟⎟⎟ , Using V∞ 2 ⎝ ⎠ ⎛ ⎜ * ⎜ LC ⎜⎜ ⎜ ⎝
CL = C ⎛ ⎜ ⎜ ⎜ ⎜ ⎜ ⎝
⎡ ⎛ ⎞ ⎢⎜ ⎟ ⎢⎜ ⎟ ⎢⎝ ⎟⎢ ⎟⎢ ⎟⎢ ⎠ ⎢ ⎣
⎤ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎥ ⎦
⎛ ⎞ 2 ⎜S ⎟ SC 1−η ⎞ * ⎜ W⎟ 1+ 1+ CT ⎟⎟⎟ +η + CLW ⎜ ⎟ S 4 ⎜ S ⎟ ⎠ ⎜ ⎟
⎞⎡ ⎟⎢ ⎟⎢ ⎟⎢ ⎟⎢ ⎟⎢ ⎠⎣
⎞ ⎟ ⎟⎛ ⎠⎜ ⎜⎜ ⎝
2 ⎞
⎝
⎠
⎤ ⎥ ⎥ ⎥ ⎥ ⎥ ⎦
SC 1 ⎜⎛ ⎟ −1 cosα + nC sin ⎛α + ε ⎞ + 1 + 1 + C ⎜ ⎟ T ⎟⎟⎠ T ⎝ ⎠ S 4 ⎜⎜⎝ ⎛ ⎜ * ⎜ LC ⎜⎜ ⎜ ⎝
C Case off zero thrust th t (CT = T = 0) : CL = C q∞ A
Channel Wing Model Airplane
⎞
⎛
⎞
⎠
⎝
⎠
SC ⎟⎟ * ⎜⎜ SW ⎟⎟ + CLW ⎜ ⎟ ⎟ S ⎟⎟ ⎜ S ⎟ ⎜ ⎟
* = C* = C* ): C = C* With constant airfoil (CLC LW L L L
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Ref. 1
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1953 NACA Full Full-Scale Scale Tests Effect of Power Settings on Static Lift Propeller Speed (rpm)
Power (hp)
Tail On Lift, Tail-On Lift δe= 0 (lb)
Tail Off Lift (lb) Tail-Off
2450
170
688
677
2625
220
788
763
Maximum CL Values for Freestream Velocity, Power, and Angle of Attack Conditions Freestream Velocity 40 ft/s
60 ft/s
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Angle of Attack α = 0° α = 20° α = 38° α = 0° α = 20° α = 38°
P = 0 hp p Channel CL Overall CL 0.2 0.2 2.2 1.3 N/A N/A 0.1 0.1 2.2 1.3 N/A N/A Channel Wing Model Airplane
P = 170 hp p Channel CL Overall CL 7.0 4.0 14 8.0 24 15 5.0 2.0 7.0 5.0 13 7.5 10
Channel Wing Design Like Custer’s CCW-2,, the channel wingg model is a modified Piper Cub. Below is a CAD model of the conceptual design with the channels replacing the inboard sections of the wings and twin motors with propellers at the trailing edge of the wing. wing
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Channel Wing Model Airplane
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Channel Wing Design o
o
Previous research found that the ideal aspect ratio, or the length of the span divided by the length of the chord, chord is 1. 1 The model’s wing has a 12-inch chord, so the channel’s span and propeller diameter are 12 in.
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Channel Wing Model Airplane
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Electric Motor Selection o
o
In order to attain the ppower-to-weight g ratio of the CCW-2,, which had two 90-hp engines and weighed about 1000 lbs, the channel wing model is estimated to weigh 7.5 lbs with modification and requires a total of 1000 W. W The motor selected is the Rimfire 35-48-700 directly driving the 12-inch propeller. Full motor specifications can be found at www.electrifly.com.
Wade Spurlock
Channel Wing Model Airplane
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Power System o
o
Lithium-Polymer y batteries are the ideal choice for high g performance and low weight. An electronic speed controller capable of handling 60 A is required i d for f eachh motor. t Exceed-RC Electric Propulsion Components F i Power Fusion P S Series i Li Li-Po P Vl Volcano S i ESC Series
Four-cell, 14.8 V
60 A Continuous, 80 A Burst (<10 s)
p y, 15 C Discharge g 4000 mAh Capacity,
2-6 Li-Po cell,, 7.4 - 22.2 V
Weight: 15.3 oz
Weight: 2.15 oz
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Channel Wing Model Airplane
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Electric Motor Testing Dual-motor test stand
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5 2 1 3
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Single motor test setup – electric propulsion system components include 1. r/c transmitter, 2. r/c receiver and battery, 3. Li-Po battery pack, k 4. 4 W Watt meter, 5. 5 ESC, ESC andd 6. 6 electric l i motor andd propeller ll Wade Spurlock
Channel Wing Model Airplane
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Electric Motor Testing
o The system is turned on, and the throttle range is set. o The close-up view of the Watt meter displays the increasing current and power as the throttle is increased. The voltage of the battery pack slowly decreases as the pack is drained. o The digital tachometer detects the propeller propeller’ss rpm. Wade Spurlock
Channel Wing Model Airplane
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Channel Fabrication o o
o
A cylinder y was cut from high-density g y foam and wrapped pp with fiberglass to provide a mold for the channels Four 3-inch-wide pieces of balsa are cut to 18 85 inches to form the 12 18.85 12-inch inch diameter semicircular channel. The balsa is thoroughly wetted and formed t the to th cylinder li d by b hand. h d The Th balsa b l is i then th covered with paper towels and clamped in place to dry for at least one day.
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Channel Fabrication Once the ppieces of balsa are curved and dry, they will be covered as one piece with fiberglass and resin. The molded channel will be strong and lightweight, and the shape will be consistent for every fabrication.
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Channel Wing Model Airplane
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References 1. Blick, E. F. and Homer, V., “Power-on Channel Wing Aerodynamics,” Journal of Aircraft, Vol. 8, No. 4, April 1971, pp. 234 234-238. 238. 2. Pasamanick, J., “Langley Full-Scale-Tunnel Tests of the Custer Channel Wing Airplane,” RM L53A09, April 7, 1953, National Advisory Committee for Aeronautics. 3. Gunther, C. L. “Comparison of Channel Wing Theoretical and Experimental Performance.” Aerospace Sciences Meeting and Exhibit, 38th, Reno, NV, Jan. 10-13, 10 13, 2000.
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