Sydney Harbour's first ferries were sail and/or oar powered, but by the mid-19th century, paddle steamers were well established. Double-ended ferries became common as they did not require turning at terminating wharves in Sydney's busy but narrow bays, including at the main hub at Circular Quay. Double-ended ferries, however, provided technological challenges for screw (propeller) propulsion and Sydney's shift from paddle steamers to screw ferries in the closing years of the nineteenth century was relatively late. Diesel power first came to Sydney Harbour ferries mainly through the conversion of existing steam ferries to diesel in the 1930s and the 1950s, when during the slow post-Bridge decades ferry companies could generally not afford new ferries. Hydrofoils were introduced to the Manly