# How does wing flex reduce wave drag?

If I'm reading this post right: What is the effect of airfoil thickness on aerodynamic lift?

• Airfoil thickness increases the lift coefficient.
• Wing flex reduces wave drag.

I'm wondering about the how. My theory is that the air sees a thicker airfoil in a flexed wing, without actually building one. Is that assumption correct? Or is it related to the end-plate effect?

Front view of a flexed wing. Orange indicates that perceived increase in airfoil thickness.

• I'm having trouble with the air sees a thicker airfoil bit... – fooot May 5 '17 at 17:26
• Right but I'm having a hard time seeing why the direction is relevant. Lift will still be perpendicular to the wing, right? – fooot May 5 '17 at 17:34
• There's a whole 2D plane that's perpendicular to the airflow, you need another reference to get a vector. – Steve May 5 '17 at 17:55
• Right, but like Steve said air flow is one dimension, you have to have a reference plane to define something perpendicular. Seems like lift would be perpendicular to the surface that is generating it. – fooot May 5 '17 at 17:56
• But what's the rationale for taking the orange slice not perpendicular to the wing? – fooot May 5 '17 at 18:27