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# l3 - D C Get D(equation 7 Step 4 Calculating the Angle of...

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16.810 IAP 2005 Engineering Design and Rapid Prototyping Prof. O. de Weck s A . B e l l , C . G r a f f Massachusetts Institute of Technology January 6, 2005 Version 1.0 XFOIL and Low Speed Airfoil Design/Analysis Notes from presentation by Mark Drela Equations Aspect ratio: S b AR 2 = (1) S = Area b = Span L = Lift b S c = = chord L i π α = (2) 3D angle i D D α α α + = 2 3 (3) Lift coefficient S V L C L 2 1 ρ = (4) Lift L SC V L 2 2 1 ρ = (5) 3D Lift 2D Lift (6) L C C Drag D SC V D 2 2 1 ρ = (7) Coefficient of Drag (8) i D d C C C + = Induced Drag AR C C L D i π 2 = (9) Center of Lift () l m cp C C c x = 4 1 (10) Reynolds Number s m 2 5 10 45 . 1

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Procedure Step 1 : 2D simulation in XFOIL Obtain , , & l C d C m C D 2 α for your airfoil Get AR (equation 1) Get ( ) cp c x (equation 10) Step 2 : Calculating Lift Get (equation 6) L C Get (equation 5) L Step 3 : Calculating Drag Get (equation 9) i D C Get (equation 8)
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Unformatted text preview: D C Get D (equation 7) Step 4 : Calculating the Angle of Attack Get i (equation 2) Get D 3 (equation 3) Structural Considerations Center of Lift along chord: ( ) cp c x is normally between 0.3 & 0.4 Place the spar at this location to avoid twisting of the airfoil. This is usually the thickest point. Apply fiberglass at 45 ° to the leading edge of the airfoil, (not 0 ° & 90 ° ) for torsional stiffness. If you are not using a spar then you need to apply fiberglass at 0 ° & 90 ° , allowing the fibers to act as a spar and bear the load. To transfer load out of the wing, you must add hard points to the foam wing. It is recommended to fiberglass and vacuum bag the wing for trailing edge strength, especially if you are using a thin trailing edge. 2...
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l3 - D C Get D(equation 7 Step 4 Calculating the Angle of...

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