Suction does. Air flow follows pressure gradients, and the lift-creating suction over the upper wing pulls in more air, not only from ahead of the airplane (which explains the induced angle of attack), but also from the side. The explanation of induced drag on the Boldmethod page is actually quite good; only gems like the wingtip vortices curve up and around ...


Don't Twist, morphing sounds torsionally flexible. Add mass to a soft spring and you get all kinds of resonances and eigenmodes. Better put the engine mass to a stiff and strong structure that can deal with its mass and forces.

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