The early steam examples reveal the design consequences of putting propulsion machinery on the ship's sides. Positioning the wheels slightly forward of amidships improved their access to clean water and made the arrangement more economical. The paddle boxes greatly increased overall beam even though the underlying hull could remain comparatively narrow and shallow. In return, the forward and after hull remained unobstructed by shafting, and the propulsion system did not require a shaft opening through the underwater hull.
Chapter · 7:30-9:41
Paddle wheels reshaped hull layout
Side wheels produced a broad beam and shallow draft while leaving the bow and stern free of propeller shafts and underwater openings.