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The Barn OwlsChris “Mo” Baughman
Kate BrennanChristine Izuo
Dan MasseJoe “Sal” Salerno
Paul SlabochMichelle Smith
Motivation• To build an aircraft
which will take off (multiple times without crashing)
• Accurately predict the performance of the designed aircraft
• Maximize the speed and rate of climb
Guidelines and Limitations
• 400 – 800 sq. in. planform area • Given Astro-Cobalt 615G motor • Must be statically stable• Takeoff run < 300 ft.• No rockets!?!?!?!?!?!?!?!?!?!?!?!?!?!?!?
Schedule and Deadlines
• February 5th – Present Conceptual Design
• February 26th – Present Detailed Design
• March 4th – Complete Parts List
• April 6th-9th – Ground Tests
WeightsStructure (estimation) 1.5
Misc. (glue, monokote, screws) 0.4
Engine (Cobalt 15) 0.56
Propeller 0.06
Servo (5) 0.50
Receiver & Battery 0.25
GPS & Transmitter 0.5
Electronics Box 1.5
Speed Controller 0.08
Main Battery 0.65
Total (lbs.): 6.0
PowerplantModel No. p/n 615G
Name 05 Geared
Gear Ratio 2.38 to 1
Armature Winding 7 turns
Armature Resistance 0.069 ohms
Magnet Type Sm Cobalt
Bearings Ball Bearings
Motor Speed 1488 rpm/volt
Geared Motor Speed 652 rpm/volt
Motor Torque/amp 0.91 in-oz /amp
Geared Torque 2.17 in-oz /amp
Voltage Range 8 to 12 volts
No Load Currrent 2 amps
Maximum Continuous Current 25 amps
Maximum Continuous Power 400 watts
Gear Motor Length 3.3 inches
Motor Diameter 1.3 inches
Motor Shaft Diameter 5/32 inch
Prop Shaft Diameter 1/4 inch
Gear Motor Weight 9 oz
www.astroflight.com
Thrust VS SpeedPropeller Thrust vs. Airpseed for NACA Clark Y section and Handout efficiency plots
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
0 20 40 60 80 100
Airspeed (ft/sec)
Pro
pel
ler
Th
rust
(lb
f)
NACA
Handout
Airfoil – GO 769
Clmax 1.7000
Cl 0.0916
a.c. 0.2500
0L -6.0000
Cd0 0.0100
rle 0.0470
ClminD .22 - 1.22
(t/c)max 0.1330
Design Factors in Choosing Airfoil
• Appropriate Reynolds Number Data (low speed)
• Minimize Drag – t/c ~ 14%– wide drag bucket– Shallow increase in drag outside of drag
bucket
• Maximize Lift– High CL max
WingDesign Decisions• No sweep
• Maximize lift
• Ease of manufacture
• Taper ratio of 0.25
• Minimize drag
• Create large enough root chord length in order to provide clearance for payload
• Slight dihedral for roll stability
• Winglets enhance in-flight performance
Fuselage• Airfoil-shaped
fuselage serves as lifting surface
• Also serves as a wing box which carries electronics
• Conventional fuselage has been replaced by booms on order to minimize weight and drag
Horizontal Tail• NACA 0009 Airfoil
– Low drag, symmetric– Can Produce both Lift and Reverse Lift– Swept to maintain straight trailing edge
to maximize control surface while minimizing planform area
Take-off/Landing Estimations
Take-off Breakdown
1
34%
2
56%
3
7%
4
3%
Landing Breakdown
1
65%2
0%
3
22%
4
13%
Take-off Distance = 176 ft.
Landing Distance = 370 ft.
(does not take into consideration climbing over an obstacle)
Flaps• Slotted, 15% of total wing area• Used as flaperons
– Enhanced lift for take-off– Control during flight– Speed brakes during landing
Weight DistributionLoad Summary (fuselage)
Load Type Magnitude x/L_start x/L_end resultant M @C_lift dw
(lbs) x/L f-lb (+ cw)
Fuel 2.00 0 0.18 0.09 -0.4448 0.434783
Payload 1 0.18 0.36 0.27 0.0278 0.217391
Fus.Struct. 0.53 0 1 0.5 0.183773 0.025183
Engine(s) 0.50 0 0.18 0.09 -0.1112 0.108696
Wing Struct. 0.56 0 1 0.5 0.194413 0.026641
Horiz. Tail 0.03 2.2 2.4 2.3 0.086654 0.006082
Vert. Tail 0.03 2.2 2.4 2.3 0.087169 0.006118
Other 0.56 0 0.05 0.025 -0.17404 0.278247
L 5.205802 M -0.15023
Tail Lift (req) -0.05272 2.2 2.4 2.3 -0.15023 -0.01054
Static StabilityStatic Margin: 0.029753 (stable)
CM,α= -0.78423 (stable)
CN,β = 0.015653 (stable)
CLβ = -0.015653 (stable)