custer channel wing investigation

DEVELOPMENT AND TESTING OF A CHANNEL WING MODEL AIRPLANE

Wade M. SpurlockMississippi State UniversityMississippi State University

OutlineOutlineo Assumptionso Blick Theory

o Static Caseo Five Components of Lifto Lift Coefficient

o Designo Motor Testinggo Channel Fabrication

2Channel Wing Model AirplaneWade Spurlock

AssumptionsAssumptions

o Subsonico Subsonico Incompressible

Adiabatic

Low Flight Speeds,Takeoff and Landing

o AdiabaticRef. 3


Blick TheoryBlick Theoryo Static-case channel lifto Five components of lift

o Upper surface of channelo Lower surface of channelo Pressure differential on channelo Wing minus channelo Vertical thrust component

o Overall lift and lift coefficientRef. 1


Static Case: V = 0 Static Case: V∞ 0 e em AVρ=&

sineL mV ε= &

Ref 2 Ref 1Ref. 2 Ref. 1


Lift: Channel SectionLift: Channel Section*1CU LC CdL C q Sη⎛ ⎞

⎜ ⎟⎜ ⎟⎜ ⎟⎝ ⎠

= −o Upper Surface:

*

cosCL LC C

P Cd

L C q S

L q q S

η

α

⎝ ⎠

⎛ ⎞⎜ ⎟⎜ ⎟

∞

∞

=

= −

o Lower Surface:

o Pressure Difference:

2:

1= dynamic pressurewhere

q Vρ

cosP Cdq q S α⎜ ⎟⎜ ⎟⎝ ⎠

∞

Ref. 1 dynamic pressure 2 = planform area = conditions at propeller disk (upper channel)= freestream conditions

q VSd

ρ

∞* = freestream conditions= unpowered lift coefficient = the fraction of lift provided by the lower

LCη

∞

surface of airfoil= span average angle of attackα = span-average angle of attackα

Channel Wing Model Airplane 6Wade Spurlock

Lift: Outboard Wing and ThrustLift: Outboard Wing and Thrust*

W LW WL C q S∞=

sin( )sin

TL nTnT

α εα

= +≈

:where

Ref. 1

:

outboard wing = number of engines= thrust

where

WnT

=

thrust = angle of attack = downwash angle

Tαε


Lift: TotalLift: Total* *1 cosLC C LC C Cd dL C q S C q S q q Sη η α⎛ ⎞⎛ ⎞

⎜ ⎟⎜ ⎟⎜ ⎟⎜ ⎟

⎜ ⎟ ⎜ ⎟⎝ ⎠ ⎝ ⎠∞ ∞= − + + −

* sinLW WC q S nT α ε⎜ ⎟ ⎜ ⎟⎝ ⎠ ⎝ ⎠

⎛ ⎞⎜ ⎟⎜ ⎟⎝ ⎠

∞+ + +

R f 1Ref. 1

* *

Case of zero thrust ( ) :dq q

L C q S C q S

∞=

= +

* * * *With constant airfoil ( ): LW LLC

LW WLC C

LC C C

L C q S C q S

L C q S

∞ ∞

∞= =

= +

=

Channel Wing Model Airplane

LW LLC L

8Wade Spurlock

Coefficient of Lift: CLCoefficient of Lift: CL

1Using 1 1 ,2d

TV

CV⎛ ⎞⎜ ⎟⎜ ⎟⎜ ⎟⎝ ⎠

= + +

2* *

2

11 14

C WL T LWLC

V

S SC C C CS Sη

η

⎜ ⎟⎝ ⎠

⎡ ⎤⎛ ⎞⎢ ⎥⎛ ⎞ ⎛ ⎞⎜ ⎟⎢ ⎥⎜ ⎟ ⎜ ⎟⎛ ⎞⎜ ⎟⎢ ⎥⎜ ⎟ ⎝ ⎠ ⎜ ⎟⎜ ⎟⎢ ⎥⎜ ⎟ ⎜ ⎟⎜ ⎟⎜ ⎟⎢ ⎥⎜ ⎟ ⎜ ⎟⎝ ⎠

∞

−= + + + +

2

4

1 1 1 1 cos sin

L T LWLC

C

S S

S C nCα α ε

⎜ ⎟⎢ ⎥⎜ ⎟ ⎜ ⎟⎝ ⎠ ⎜ ⎟⎜ ⎟ ⎢ ⎥ ⎝ ⎠⎝ ⎠ ⎢ ⎥⎣ ⎦⎡ ⎤⎛ ⎞⎢ ⎥⎜ ⎟ ⎛ ⎞⎢ ⎥ ⎛ ⎞⎜ ⎟ ⎜ ⎟+ + + + +1 1 1 1 cos sin4

CT TC nCS α α ε⎢ ⎥ ⎛ ⎞⎜ ⎟ ⎜ ⎟⎢ ⎥ ⎜ ⎟⎜ ⎟ ⎜ ⎟⎜ ⎟ ⎝ ⎠⎢ ⎥⎜ ⎟ ⎝ ⎠⎜ ⎟ ⎢ ⎥⎝ ⎠ ⎣ ⎦

+ + + − + +

* *C f th t ( 0) C WS STC C C C⎛ ⎞ ⎛ ⎞⎜ ⎟ ⎜ ⎟⎜ ⎟ ⎜ ⎟+

Ref. 1

* *

* * * *L

Case of zero thrust ( 0) :

With constant airfoil ( ): C

C WT L LWLC

LW L LLC

TC C C Cq A S S

C C C C

⎜ ⎟ ⎜ ⎟⎜ ⎟ ⎜ ⎟⎜ ⎟ ⎜ ⎟⎜ ⎟⎜ ⎟ ⎝ ⎠⎝ ⎠

∞= = = +

= = =


LLW L LLC

9Wade Spurlock

1953 NACA Full-Scale Tests1953 NACA Full Scale TestsEffect of Power Settings on Static Lift

Propeller Speed (rpm) Power (hp) Tail On Lift δ = 0 (lb) Tail Off Lift (lb)Propeller Speed (rpm) Power (hp) Tail-On Lift, δe= 0 (lb) Tail-Off Lift (lb)

2450 170 688 677

2625 220 788 763

Maximum CL Values for Freestream Velocity, Power, and Angle of Attack Conditions

Freestream Angle of P = 0 hp P = 170 hpFreestream Velocity

Angle of Attack

p pChannel CL Overall CL Channel CL Overall CL

40 ft/sα = 0° 0.2 0.2 7.0 4.0α = 20° 2.2 1.3 14 8.0α = 38° N/A N/A 24 15

60 ft/sα = 0° 0.1 0.1 5.0 2.0α = 20° 2.2 1.3 7.0 5.0


α = 38° N/A N/A 13 7.5

10Wade Spurlock

Channel Wing DesignChannel Wing DesignLike Custer’s CCW-2, the channel wing model is a modified , g

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 wingmotors with propellers at the trailing edge of the wing.


Channel Wing DesignChannel Wing Design

o Previous research found that the ideal aspect ratio, or the length of the span divided by the length of the chord is 1the chord, is 1.

o The model’s wing has a 12-inch chord, so the channel’s span and propeller diameter are 12 in.

Wade Spurlock Channel Wing Model Airplane 12

Electric Motor SelectionElectric Motor Selection

o In order to attain the power-to-weight ratio of the CCW-2, p g ,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 Wmodification and requires a total of 1000 W.

o 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.


Power SystemPower System

o Lithium-Polymer batteries are the ideal choice for high y gperformance and low weight.

o An electronic speed controller capable of handling 60 A is i d f h trequired for each motor.

Exceed-RC Electric Propulsion ComponentsF i P S i Li P V l S i ESCFusion Power Series Li-Po Volcano Series ESC

Four-cell, 14.8 V 60 A Continuous, 80 A Burst (<10 s)4000 mAh Capacity, 15 C Discharge 2-6 Li-Po cell, 7.4 - 22.2 Vp y, g ,Weight: 15.3 oz Weight: 2.15 oz


Electric Motor TestingElectric Motor TestingDual-motor test stand6

5

1

2

3 4

Single motor test setup – electric propulsion system components include 1. r/c transmitter, 2. r/c receiver and battery, 3. Li-Po battery

k 4 W 5 ESC d 6 l i d ll


pack, 4. Watt meter, 5. ESC, and 6. electric motor and propeller

Electric Motor TestingElectric 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’s rpm.


o The digital tachometer detects the propeller s rpm.

Channel FabricationChannel Fabrication

o A cylinder was cut from high-density foam and wrapped with y g y ppfiberglass to provide a mold for the channels

o Four 3-inch-wide pieces of balsa are cut to 18 85 inches to form the 12-inch diameter18.85 inches to form the 12 inch diameter semicircular channel.

o The balsa is thoroughly wetted and formed t th li d b h d Th b l i thto the cylinder by hand. The balsa is then covered with paper towels and clamped in place to dry for at least one day.


Channel FabricationChannel Fabrication

Once the pieces of balsa are pcurved and dry, they will be covered as one piece with fiberglass and resin. The molded channel will be strongThe molded channel will be strong and lightweight, and the shape will be consistent for every fabrication.


ReferencesReferences1. Blick, E. F. and Homer, V., “Power-on Channel Wing Aerodynamics,”

Journal of Aircraft, Vol. 8, No. 4, April 1971, pp. 234-238.Journal of Aircraft, Vol. 8, No. 4, April 1971, pp. 234 238.2. Pasamanick, J., “Langley Full-Scale-Tunnel Tests of the Custer

Channel Wing Airplane,” RM L53A09, April 7, 1953, National Advisory Committee for Aeronautics.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, 2000.Reno, NV, Jan. 10 13, 2000.


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