Previously it has been shown [M. J. Hinich and W. Rule, J. Acoust. Soc. Am.58, 1023–1029 (1975); W. S. Hodgkiss, IEEE J. Ocean. Eng.OE‐8, 120–130 (1983)] that deformations of towed arrays from a straight line shape can produce significant distortions in beam patterns and errors in bearing estimation if the beamforming assumes linearity. It has also been shown that a deformed array helps to remove left/right ambiguities in the beam patterns, provided the beamforming is done with the correct array configuration. In this work these two effects are studied for undamped and damped sinusoidally deformed arrays (as observed in practice) of one, two, and three half‐cycles with relatively small array amplitudes. By use of fixed arc length separations along the array, the phone (x, y) coordinates are determined numerically for each sinusoidal shape. The complex pressure fields are modeled for sources at various locations. Then beamforming is carried out (1) with the known array configuration, and (2) assuming that the array is linear. Degradations resulting from assuming linearity and the ability to remove left/right ambiguities are discussed in terms of reduced gain, angular resolution, and bearing errors.