• S2055-PT (Fig. 12.78)
The S2055 is a slightly thinned and decambered S2048. The results of this small perturbation in shape are marginally lower drag and a downward shift of the lift range. As with other F3B airfoils, flaps are necessary to fully realize the capabilities of the airfoil.
Of all the airfoils tested, the S2055-PT had the lowest drag at 300k. Although several attempts were made to reduce the drag further through the use of trips, none worked. Instead, the drag was increased except when the trip was far aft, and then it had no effect.
Although this is the lowest drag airfoil tested and should do very well on sailplanes where speed is paramount, the 8% thickness offers a significant construction challenge.
Also see: SD2030, S2048, RG15, HQ2/9, SD8000 Digitizer plot: Fig. 10.28 Polar plot: Fig. 12.78
Thickness: 7.99% Camber: 1.66%