Fig. 6. Performance of theoretical rectangular wings with varying wave speeds. Wings were generated with a first-degree polynomial (20% of the wing area in the outer one-fifth). S_p=0.0069m², U=0.15ms^-1, H=0.058m and f=2.27s^-1. (A) Thrust versus average chord length. (B) Efficiency versus average chord length. S_p, total area of one pectoral fin; U, velocity; c, wave speed; H, fin tip amplitude; f, flapping frequency.