For a range of bending stiffness distribution (Fig. 9A), we computed the maximum local curvature over the fin ray during impact, and the maximum magnitude of the spatially-integrated force on the fin ray (Fig. 9B). The values are plotted vs. Bdistal, the value of B at a location 67% of the ray length from the base. Over an intermediate range of Bdistal (which includes a biological value, boxed), the maximum curvature is nearly inversely proportional to Bdistal. Surprisingly, the maximum force decreases as the fin ray becomes more flexible. Although the distal region bends more sharply when it is more flexible, it cannot resist large fluid forces due to its small bending rigidity. Thus, the fluid force on the fin ray near the vortex is constrained to be small. For a very flexible fin ray (d 5 0.048), we found rapid oscillations of curvature near the distal 20% of the fin ray during the impact (Fig. 9C). The alternating patches of blue and red show the large values of oppositely signed curvature. Decreasing the flexibility further caused a stronger attraction, with no apparent oscillation of curvature. Details of this attraction (and eventual collision), for a point vortex, are studied in Alben (2012).