I'm not an aeronautical engineer, but I am making a brave attempt to perform a preliminary design for an 4-metre wingspan radio controlled glider. With special thanks to @mns I have now learned a formula for calculating the coefficient of induced drag. The question now is how do I use it to calculate total drag.
Considering the formula below, how do I make a reasonable estimation of efficiency factor (e)
I've selected a prismatic inner wing with tapered outer wing to assimilate an ellipse? I understand that they state that (e) for a perfect ellipse is 1. What is 0 then, a square? Here is my wing planform:
They then state that I should add CDi to CD0 to offer me a total CD.
The question I ask now is why add CD0 (That is CD at 0 degrees AoA if my angle of incidence (setting angle of the wing) is 6.25 degrees?
I assume that I then run this through the lift formula to get drag in newtons.
The curve for CD / Alpha can be seen here