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Structures PDR #1 AAE451 – Team 3 October 28, 2003. Brian Chesko Brian Hronchek Ted Light Doug Mousseau Brent Robbins Emil Tchilian. Introduction. Updated Weight Code Geometric Layout of Wing Structure Spar geometry, materials chosen, & location Material Properties
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Structures PDR #1 AAE451 – Team 3 October 28, 2003 Brian Chesko Brian Hronchek Ted Light Doug Mousseau Brent Robbins Emil Tchilian
Introduction • Updated Weight Code • Geometric Layout of Wing Structure • Spar geometry, materials chosen, & location • Material Properties • Analysis of Wing Loads • Twisting Moments • Deflection at Tip • Future Analysis
Weight Calculation Process • Initial guess at size and weight of aircraft with given geometry • For initial weight, wing resized for stall speed requirement • Plane resized around new wing size • Weight of aircraft updated • Process repeated until convergence
Weight Code Results • AR set at 5 • Span ~ 14 ft • Chord ~ 2.8 ft • Weight ~ 49 lbs P
Wing Structure • Spar(s) Configuration • 2 spars make convenient attach points for additional structure (similar to wing box) • Spar locations based on historical data • Front Spar ~ 15% of chord • Rear Spar ~ 60% of chord • Material Selection • Object of a trade study Ref. Niu, Airframe Structural Design
Spar Cross Section h h t t Difficult to manufacture Difficult to analyze Ugly Easy to manufacture Easy to analyze Pretty
What Materials to Use Titanium Bass / Spruce
Material Properties Titanium = difficult to obtain Wood = not difficult to obtain Ref. 1999 Forest Products Laboratory Wood Handbook Ref. www.towerhobbies.com
Twist Constraint (<1o) Ref. Kuhn pg. 49 Where T = Torque (in-lbf) L = Length (in) l= f(B0, A0) (ref. Appendix) A0 = f(E, I) (ref. Appendix) B0 = f(G,J) (ref. Appendix) E = Young’s Modulus (psi) I = Moment of Inertia (in4) G = Torsional Stiffness (psi) J = Polar Moment of Inertia (in4) Assumptions: Small Deflections Spars & Ribs Carry all Torsion Span ~ 14 ft Chord ~ 2.8 ft Safety Factor = 1.5 G-Loading = 5.0 Weight = 49 lbs Ref. Gere
Twist at Tip (Zoom) Chosen Front Spar = 0.73” thick Chosen Rear Spar = 0.25” thick
Deflection at Tip Load (lbf) Ref. Gere pg. 892 a (in) Where Load = Weight*SF*G-loading (lbf) L = Length (in) E = Young’s Modulus (psi) I = Moment of Inertia (in4) L (in) Assumptions: Small Deflections NO TORSION Span ~ 14 ft Chord ~ 2.8 ft Safety Factor = 1.5 G-loading = 5.0 Weight = 49 lbs For this design: a = 3 ft or 36 in (based on span-wise lift distribution)
Deflection at Tip Chosen Spar Configuration
Is Stress too High? Load (lbf) Ref. Gere pg. 323 a (in) Where M = Weight*SF*G-loading*a (in-lbf) y = Maximum Dist from Neutral Axis (in) I = Moment of Inertia (in4) L (in) Assumptions: Span ~ 14 ft Chord ~ 2.8 ft Safety Factor = 1.5 G-loading = 5.0 Weight = 49 lbs For this design: a = 3 ft or 36 in (based on span-wise lift distribution)
Covering • Traditional Monocote may not be strong enough for these large aircraft • Coverite 21st Century Iron on Fabric is stronger, and resists tears much better • 0.34 oz/ft2 • Approx. 2 lbs for entire wing Ref. www.towerhobbies.com
Summary • Main Wing • Spruce or Bass wood • Front Spar • 0.73” thick by 3.6” high • Rear Spar • 3/8” thick by 3” high • Weight • ~5.9 lbs for front spar • ~1.6 lbs for rear spar h t
Future Analyses • Landing gear • Strength analysis • Tip-over analysis • Keep updating weight & C.G. estimate • Tail assembly analysis • Similar to wing analysis • Fuselage construction • Materials
Appendix Ref. Kuhn
