1. Structures and Weights
Team One
Speakers
Todd Mostrog
Chris Grupido
Daniel Halla
John Apostol
Structures and Weights
PDR 2
03 March, 2005

2. Overview Load Factor Selection Load Conditions Torsional Analysis
Bending Analysis
Structural Design
Wing
Fuselage
Tail Section
Weight Estimation
Landing Gear Design

3. Load Factors Maximum Load Factor, nmax
For CLmax of Wing = 1.24 and Wing Area = 2.2 ft2
Stall Speed : VSTALL = 20 ft/s : nmax = 1.00
Take-off Speed : VTO = 24 ft/s : nmax = 1.44
Turn Speed : VTURN = 25 ft/s : nmax = 1.56
Loiter Speed : VLOIT = 30 ft/s : nmax = 2.26
Max Speed : VMAX = 40 ft/s : nmax = 4.01

4. Load Factors Turn Considerations Bank Angle (deg) n Turn Radius (ft)30
1.15
34.18 45
1.41
19.53 60
2.0
11.21 75
3.86
5.21

5. Load Factors Vertical Turn / Loop Considerations
Considered for Loiter Speed : V = 30 ft./sec.
For Pull – Up
For Velocity Vector Vertical
For Pull - Down

6. Load Factors Conclusions Load Factor of 2.4 chosen
Aerobatics Performed at Loiter Speed or Below
Max Speed for Level Dash Only
Max Bank Angle of 60 degrees
Turn Radius of ft.
Vertical Turn Radius:
Pull-Up : ft.
Velocity Vector Vertical : ft.
Pull-Down : 8.22 ft.

7. Load and Moment Conditions
For Maximum Load Factor of 2.4 and Weight of 1.3 lbf
Maximum Load = 3.12 lbf
Lift Distribution on Wing is 83% Elliptical
- Centroid of Elliptical Parabolic Semisegment : x = 3/8 base
- Assumed Resultant Loading at ½ Wing Section Span
x = ½(b/2) = ½(3.85 ft. / 2) = 0.96 ft.
Maximum Bending Moment at Root Chord
M = 1.5 ft.-lbf = in.-lbf

8. Torsional Analysis Twist Angle Equation For Root Chord = 5.04 in.
For Twist of 1 deg :
Twist Angle = rad/in.
For Monokote Skin
t = in. and G = 406 ksi
For Root Chord = 5.04 in.
Shear Flow = 0.33 lb. \ in.
Shear Stress = 330 psi
Torque Applied = 9.52 lb.-in.
For Tip Chord = 9.28 in.
Shear Flow = lb. \ in.
Shear Stress = 204 psi
Torque Applied = 0.47 lb.-in.

9. Modeling Assumptions Simplifying Assumptions Wing loading
Concentrated lift force
Centroid of a semi-segment of nth degree 3/8 span
Originally modeled at .5 span -- maintained
Effect of landing gear weight ignored
Wing Geometry
Sized from bending analysis
Constant size spars

10. General Construction Wing and Fuselage
Traditional rib and stringer construction
Balsa leading edge
All stringers are 0.125” square
Tail Assembly
Solid Balsa
Monokote Covering
0.001 thick
Grade “B” Balsa (trade study pending)
Hidden fixed gear with 4 tires
Foam main wheels
0.02 lbs (pair)
Tail wheels
Manufactured

11. Wing/Tail Properties Wing 3.7 ft. Span Weight =0.12 lbf
Polar Moment of Inertia = in.4
Maximum Moment
17.97 in.-lbf (2.4 gs)
0.67 in. max deflection
Spars
(2) X 0.5 (average)
20 Ribs
2.2 in. Separation
2 Stringers
Solid Tail Section
31.74 in.3
0.17 lbf

12. Wing Geometry

13. Fuselage Properties 3 in. diameter 25 in. length Weight = 0.05 lbf
Polar Moment of Inertia = in4
Maximum Moment
19.2 in.-lbf
J = in4
0.36 degrees/inch of twist
6 Ribs
4.18 inches of Separation
12 stringers spaced 30 degrees apart

14. Fuselage Geometry

15. Landing Gear 1 ¾” diameter foam wheels (2) Fixed to wing ribs
Designed for no failure
Top half hidden in wing section picture of this below

16. Landing Gear Main Considerations Four points of contact
Increases on ground stability
Aft landing gear on tail
Rudder mounted for ground directional control
Forward landing gear in wing
Simple structure attachment
Reduce drag
Four point landing gear, two forward two aft.
Aft gear mounted on the bottom edges of the rudder.
Allows for steering, so as rudders turn aircraft will turn.
Forward landing gear mounted halfway into wing, in the bottom flat section of wing.
Simple attachment, no real strut will be needed, direct axel design.

17. Landing Gear Main Concerns Forward tip over Rudder mounted aft gear
Location of center of gravity close to location of forward point of contact
Rudder mounted aft gear
Strength of rudder to avoid failure
In wing forward gear
Limits allowable propeller size
Forward tip over is important, making sure the center of gravity will be aft of the forward landing gear contact point.
Rudder structure needs to be strong enough for tail strike on take off or rough landing.
Rudder also needs to be strong enough to not break when rudder is moved.
Rudder will be solid balsa structure and can be reinforced with small wire if necessary.
The in wing mounted landing gear reduce propeller clearance and so a three blade propeller is being analyzed, slight adjustments can be made to wing to increase the distance from motor centerline to ground in rest position.

18. Landing Gear In wing mounted gear Tail mounted gear Tip-over Analysis
Low center of gravity
5-10 degrees before wing strike
Tail mounted gear
Initial positive rest angle
5-10 degrees
For tip over the in wing mounted gear will lower out center of gravity and cause the wingtips to touch long before the center of gravity passes over the point of contact.
Between the radius of the tire and the wing dihedral there will be approximately 5-10 degrees before wing strike.
So it will be stable on ground but will not allow for much roll on landing.
Due to the aft landing gear being mounted in the rudders, there will be a slight nose up position when at rest at ground, this will help the nose tip over as it shifts the project center of gravity farther aft of the forward landing gear.
This will also add propeller clearance when at rest, as aircraft accelerates on takeoff the tail will natural rise and thus moving the aircraft body line closer to parallel to the ground, this will also be looked at when deciding on wing incidence angle.

19. Center of Gravity Centers of Gravity Xc.g. = 0.20 * Aircraft Length
Number
Part 1
Motor 2
Batteries 3
Wing 4
Wheels 5
Aileron Servos 6
Speed Controller 7
Fuselage 8
Gyro 9
Mixer 10
Receiver 11
Tail Servos 12
Tail 13
Tail Gear
Increasing Weight 13 9 11 7 12 8 5 6 10 4 3 1 2
Centers of Gravity
Xc.g. = 0.20 * Aircraft Length
Zc.g. = 0.55 * Aircraft Height

20. Mass Moments of Inertia
Equations to solve MOI
Mass Moments of Inertia
Ixx = lb-ft2
Iyy = lb-ft2
Izz = lb-ft2

21. Products of Inertia Since aircraft is symmetrical around y-axis plane:
Equations to solve for POI
Mass Product of Inertia
Ixz = lb-ft2
Since aircraft is symmetrical around y-axis plane:
Ixy = Iyz = 0

22. List of Parts Part Description Weight (lbs) Motor
Graupner SPEED V (ungeared)
0.36
Batteries
Kokam Li-Poly 2-cell 1250 mAh x 2
0.365
Wing
Grade B (Medium) Balsa Wood
0.09
Main Landing Gear
LYT 1 ¾” Foam Wheels x 2
0.020
Aileron Servos
JR Mini 311 x 2
0.082
Speed Controller
Castle Creations PIXIE-20P
0.018
Fuselage
0.02
Gyro
GWS PG03 Piezo Gyro
0.0125
Mixer
Vee Tail OMNI
0.0126
Receiver
JP 6-Channel
0.038
Tail Servos
Tail
0.03
Tail Landing Gear
Lexan EM1210 Polycarbonate x 2
0.0024

23. Parts Location Number Part Motor Batteries Wheels Aileron Servos
Speed Controller
Gyro
Mixer
Receiver
Tail Servos
Tail Gear

24. Questions or Comments?