• Flat Plate-PT (Fig. 12.37)
This airfoil was the only one machined from solid metal. It was A in thick, had a rounded leading edge, and the aft 3 in were tapered to a ^ in trailing edge. Since this model was completely symmetrical, the data served to check several aspects of the instrumentation.
The geometry of the flat plate is typical of that used for slab, sheet-balsa stabilizers. The polar data is representative of a full-flying stabilator. In other words, there was no elevator deflection, only angle of attack changes.
As shown in the polars, the lift and drag coefficients are practically the same over the Rn range tested. From both theory and many previous measurements it is known that for a flat plate developing lift, the recovery pressure gradients on the suction side are both early and steep. This promotes a rapid transition to turbulent flow. The independence of drag with Rn and the relatively high value of the drag are commonly found when the flow is turbulent, as it is here.
Comparing the data with the symmetrical SD8020, for example, shows that the drag of the flat plate is considerably higher. Consequently we recommend a more streamlined airfoil like the SD8020 for stabilizers.
Also see: SD8020 Polar plot: Fig. 12.37 Lift plot: Fig. 12.38
Thickness: 2.08% Camber: 0.00%