Here we continue in the vein of Probs. 5.34 to 5.36, except we examine a thicker airfoil and look at the relative percentages of skin friction and pressure drag for a thicker airfoil. Estimate the skin friction drag coefficient for the NACA 2415 airfoil in low-speed incompressible flow at Re = 9 × 106 and zero angle of attack for (a) a laminar boundary layer, and (b) a turbulent boundary layer. Compare the results with the experimentally measured section drag coefficient given in App. D for the NACA 2415 airfoil. What does this tell you about the relative percentages of pressure drag and skin friction drag on the airfoil for each case?