Feathering mechanisms kept paddle blades close to vertical while passing through the water, improving efficiency and reducing wash. Ocean conditions still created difficulties: rolling alternately immersed and exposed the wheels, placing strain on the common drive shaft. Changes in loading also altered immersion, while naval paddle wheels remained vulnerable to gunfire. A submerged propeller avoided many of those problems. In the 1845 comparison, screw-driven HMS Rattler and paddle-driven HMS Alecto had similar engine power, but Rattler won a long race and towed Alecto stern-first at 2.7 knots in the tug-of-war. Later development favored shorter, wider blades and additional propellers as engine power increased.
Notable Point · 2:18:56-2:23:38
Paddle-wheel limits and HMS Rattler's screw trials
Feathering improved paddles, but rolling, loading, and gunfire exposure helped favor submerged screws.