function [ df ] = df(aoa)
%aoa (foil angle of attack in radians)
%df = 0.5-.25*cos(aoa);  %Percentage of chord

%df = 0.5;

D_AOA = [0    10  25 65 90 115 155 170 180];
D_df =  [.25 .25 .38 .47 .5 .53 .62 .75 .75];


df = interp1(D_AOA*pi/180,D_df,abs(RestrictAngle(aoa)));

end

