Why the great wing flex? less drag?
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Dantheman, I think it is just mostly because it looks cool. Obviously (and I don't blame them) Boeing thinks cool looks are more important than accurate ones. But hey, it looks pretty damn cool, but I could not imagine there being that much wing flex (I am not an engineer though).- Fly United -
My photos.
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well, I wish I had been paying more attention during this day in aerodynamics so I could go more in depth, but you'll have to deal with the short version instead. Some companies use wingflex to help make the wing more efficient in cruise. To get the plane off the ground sooner you need the wing to be at a higher angle of attack (the angle between the wing and the relative wind) so that it creates more lift. But once you're in the air the plane will usually be going fast enough that that extra built in AOA will cause more drag so if the wing twists forward a bit you'll have a lower AOA and less drag...
...at least that's sorta how i remember it.
Also dihedral (having the wings slope up from the fuselage) helps make the aircraft more stable about its lateral axis
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Originally posted by screaming_emuwell, I wish I had been paying more attention during this day in aerodynamics so I could go more in depth, but you'll have to deal with the short version instead. Some companies use wingflex to help make the wing more efficient in cruise. To get the plane off the ground sooner you need the wing to be at a higher angle of attack (the angle between the wing and the relative wind) so that it creates more lift. But once you're in the air the plane will usually be going fast enough that that extra built in AOA will cause more drag so if the wing twists forward a bit you'll have a lower AOA and less drag...
...at least that's sorta how i remember it.
Also dihedral (having the wings slope up from the fuselage) helps make the aircraft more stable about its lateral axisYou've got to try to find what's right before your eyes-Finger Eleven
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Originally posted by JeffinDENReally? Can you back that up? I would love to see a link.- Fly United -
My photos.
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Well, I guess I'm qualified to address this question. As some of you know, I'm a Stress Analysis engineer working on the 787 wing. My responsibility covers the wing finite element model. The FEM is a computer-based mathematical representation of the wing structure. It models the internal loads, strains, and deflections that the wing will experience in flight.
The wing deflection in the artist's rendering at the top of this thread is the real deal. In a level 1g cruise attitude, the tips of the wing are higher than the top of the fuselage. For a 2.5g dive maneuver, you'd see around 8m of vertical deflection at the tip.
Since I'm not an aerodynamicist, I can't speak for the efficiency gains that result from high wing deflection. Boeing's aero group has made a lot of advancements in computational fluid dynamics, which gives them the power to assess many more wing configurations than back in the day when they had to rely more heavily on wind tunnel data.
Additionally, the composite wing can handle larger deflections than an aluminum wing, because it won't develop fatigue cracks. With aluminum, you would have a higher risk of cracking in the lower surface, so you would have to make the panels thicker, creating a weight penalty. Of course, that in turn would reduce the wing deflection, defeating the purpose.
I remember remarking on how much the 777 wing flexed when I first saw it fly. That will pale in comparison to the 787 wing.
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