SWEEP: The angle measuring how far the outline of the fin is
curved backwards; also referred to as rake. Sweep has a direct
influence on pivot. Fins with more sweep produce a longer
turning arc, less sweep offers a tighter turning arc. FLEX: The
distortion of the fin from its original shape caused by lateral
pressure during a manoeuvre. Flex influences the response
characteristics of a fin. Fins with little flex (stiff) produce
instant response, speed and drive. Fins with more flex (flexy)
are more forgiving and offer a whipping sensation.