The HQ-series of airfoils are apparently generated in a manner similar to the NACA four – and five-digit airfoils. In this method, the thickness distribution is wrapped around a camber line. Although no details of Quabeck’s method have been given, based on the lack of smoothness of the coordinates it appears that neither the thickness distribution nor the camber are analytical functions, as they are with the NACA sections.

Quabeck’s design philosophy, which has been widely published in the Euro­pean model press, concentrates largely on the effects of the camber distribution on the airfoil pitching moment29. Although it is not often mentioned, Quabeck has been guided by his prolific building and expert flying skills.

The airfoils themselves are characterized by a fair amount of aft loading. For some of them, the upper-surface velocity distribution has a gradual pressure recovery region which lowers drag. In our opinion this feature is the principal key to the success of Quabeck’s more popular sections.

Finally, it should be noted that the airfoil designation “HQ” is also used by Horstmann and Quast, who collaborate in the design of airfoils for full-scale competition sailplanes (for example, the Ventus, ASW-22, and ASH-25).

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