Lift to drag ratio and elevation angle

[PierreB]

I just learn that the elevation angle would be given by the lift-to-drag (L/D) ratio as Tan(elevation angle). For example the L/D or glide ratio is (roughly) 4. Tan(elevation angle) is 4(76 degrees). On a trigonometric table we go to tangent for 76 degrees and we see the value of 4.

http://2e5.com/kite/ld/ provides some indications and the graph below:

I don’t know if this is correct but that proves my knowledge of physics and math is so limited that I have to do some research each time I run into a problem in AWE.

[tallakt]

I believe this is correct. This is true if the kite is at rest and without mass.

In practice, the mass of the kite will have a large effect in low-moderate winds. With mass, every time a gust hits, the ratio of lift lost to gravity is smaller, causing the effective L/D to increase, causing the kite to fly forward.

Also to make this more complex, a soft kite will be bridled relative to the tether. Flying higher results in a reduction of angle-of-attack and thus different C_L and C_D for the wing.