text: In order to obtain low drag sections, the 
  transition from laminar to turbulent must be 
  delayed so that a greater portion of the sur- 
  face will be influenced by the laminar bound- 
  ary layer. The conventional, low speed air- 
  foil shapes are characterized, by minimum 
  pressure points very close to the leading edge. 
  Since high 
  local velocities enhance early 
  transition, very little surface is covered by 
  the laminar boundary layer, A comparison 
  of two 9 percent thick symmetrical airfoils is 
  presented in figure 1.25. One section is the 
  NACA C!UO~ section which 
  “conventional” 
  has a minimum pressure point at approxi- 
  mately 10 percent chord at zero lift. The other 
  section is the NACA 66039 which has a 
  minimum pressure point at approximately 60 
  percent chord at zero lift. 
  The lower local 
  velocities at the leading edge and the favor- 
  able pressure gradient of the NACA 66-009 