Structures Weights PDR Objective Examine airfoil structure choices
Structures & Weights PDR
Objective • Examine airfoil structure choices • Examine fuselage structure • Examine wing, boom, tail attachment methods • Examine landing gear options
Airfoil Structure • Options being considered: • Balsa Rib and Spar • Advantages • Experience • Software Modeling • “One-Cut” Ribs • Wing Jig Available • Disadvantages • Inconsistent Material Properties • Trailing Edge Confinement • Time Consuming to Monokote • Heavy Relative to Foam (11 lb/ft 3)
Airfoil Structure • Styrene Foam • Advantages • Easier to Form “Exotic” Shapes • Light Weight (1. 42 lb/ft 3) • Good Compression Qualities • Disadvantages • Does not Carry Bending Moment • Will Require Balsa Stiffeners • Hot-Wire Slack
Finite Element Methods Modeling 3/8” 1/8” All Spars
F E M Modeling Exaggerated Wing Deflection Uniform Pressure Load: 3. 5 lbs*2. 5 g’s*1. 5 sf = 13. 13 lbs Divided by ½ Wing Area: 13. 13 lbs / 891 in^2=. 0147 psi
F E M Modeling Moment in the Z-direction (up) • Huge percentage of bending moment transmitted to all spars • Final sizing of spars critical to balancing weight with applied load! FEM Calculated Weight: . 77 lbs for ½ wing
Fuselage Structure • Traditional Balsa Structures • Advantages • Experience • Software Modeling • Disadvantages • “Glued-Together” Pieces Design • Foam • Advantages • Light Weight • “One-Piece” Design • Disadvantages • Does not carry Bending Moment • Difficulty Attaching Boom
Tail Attachment Concept
Fuselage Attachment Concept
Main Gear Attachment Concept
- Slides: 11