The fin profile describes the cross-sectional shape of the fin with several parameters.
- The thickness/chord ratio of the fin is the thickness D expressed as the percentage of the chord S. If a fin is 8 mm thick and 8 cm wide, its relative thickness is 10 %.
- The position of the greatest thickness is described as the distance T of the maximum thickness from the leading edge N expressed as the percentage of the chord S. A standard percentage would be 30 %.
- The camber of the profile is the shape forward of and rear of the greatest thickness.
- The radius of the nose is the radius of leading edge.
- The trailing edge is the rear end of the fin profile.
Figure 3: Characteristics of the fin profile
fc front camber
rc rear camber
te trailing edge
T distance of the maximum thickness from the leading edge
D/S = thickness/chord ratio, e. g. D = 9 mm, S = 100 mm à 9%
T/S = e. g. T = 30 mm, S = 100 mm à 30%
The various cross sections are defined by the NACA sections (National Advisory Committee for Aeronautics). NACA 0012 for instance describes a profile with thickness/chord ratio 12 %.