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Old 02-25-2010, 03:16 PM
  #17  
victorzamora
 
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Default RE: Spanwise Lift and Stall Sequence

Wow, that's really obnoxious....I typed WAY more than that! However, I feel like I can add to what others have said since I thought I posted. The wingtip vortices reduce the effective AOA, creating an artificial twist. What it does is it increases the pressure over the top of the wing, moreso at the tip than at the root. You don't have to consider it or calculate it....all you have to do is run the equations that already take those effects into account. It's just a concept you need to understand.

The reason that taper, twist, and aspect ratio are important IS because of wingtip vortices. Twist is partially used to reduce spanwise flow. Taper and aspect ratio is to minimize the area that the vortices effect the most. Vortices effect approximately the same AMOUNT of span where you have to account for it, and you can ignore the rest (for a simple model). Say your plane needs 100 squares per wing-half. Vortices effect (for example) 4 inches of span. If you have a wing that's 10in semispan, 10in chord...the vortices effect 40% of the wing (aspect ratio of 1, no twist). If your wing is 25in semispan and 4 in chord, then the vortices only effect 16% of the wing (4in semispan*4in chord). Taper also reduces the area effected, by making the area at the wingtip less for the same span length. I hope that makes sense. If it doesn't...I'll draw something up.

Mechanical twist is LITERALLY twisting the wing to LITERALLY vary the angle of attack of the wing along the semispan.

I don't think that elliptical wings stall at the TE of the root first, and the picture showing stall tendencies shows that.