The camber distribution from root to tip is not the same in all fin designs. Fins with low or medium lift performance will be rather flat and thin at the tip region. For longer fins and Formula fins, ideas of yacht constructions can be helpful.
For Formula fins, it can be of advantage to combine a rather slender, slightly tapered and trapezoid outline with
- a slightincrease of the thickness/chord ratio
- a slight decrease on the distance of the maximum thickness from the nose.
Another interesting detail is the root profile. The root of the fin is lying within the boundary layer of the underside of the board. The flow around the fin is being disturbed. Therefore, it seems to be of advantage to construct the root profile as a laminar profile to delay the flow breakdown.
Figure 21: Two examples of Formula fins (characteristic profile parameters, length 70 cm)
PW root profile
PM profile at 35 cm
PS profile in the tip region
Fin A: slightly better upwind performance
thickness/chord ratio thickness distribution
PW 7.5 % 35 %
PM 8.1 % 29 %
PS 10 % 26 %
Fin B: higher speed potential
PW 7.3 % 42 %
PM 8.0 % 30 %
PS 8.8 % 26 %