Separation Drag Reynolds Number Effect 64-009 and 64-012 Sections.

The drag polars for the 64-012 section and the 64-009 section are examined for the effect of Reynolds Number on the separation drag coefficient, Ksep. The result presents one Ksep for the transition fixed at leading edge of mid-chord and another Ksep when the transition is moving between those two points. The drag bucket is fully defined i.e., the minimum drag coefficients for leading edge and mid-chord transition are displayed, only for Reynolds Numbers of about 1 to about 6x10 to 6th power. Fixing the transition at the leading edge increases Ksep by a factor of three. This study extended only through the linear lift range in the data. Hydrofoil prototypes of symmetric, 9-12, 64 series section if practical would be defined by the Abbott and Doenhoff data if the drag bucket is neglected. Extrapolation of Abbott and Doenhoff to model test by Reynolds Numbers for the same sections is considerably less certain. Generalization of the structure of these results for other sections will be considered in later notes. This data defines an elegant structure which requires correlation with boundary layer theory for the transition point but time does not permit such an investigation.