The letter evaluates the performance of a ship target's radar cross section (RCS) using a commonly used over-the-horizon radar's plane wave at 28 MHz. In contrast to prior work, we conduct a comprehensive analysis by simultaneously considering the following factors: (i) 3D modeling of a ship target, (ii) varying plane wave incidence angles, and (iii) the influence of sea surface clutter. Our simulation study shows that the RCS of the same ship target can vary significantly at different incident angles of the plane waves, primarily due to the complex ship structure.