Steamboat

A steamboat is a boat that is propelled primarily by steam power, typically driving propellers or paddlewheels. The term steamboat is used to refer to small steam-powered vessels working on lakes, rivers, and in short-sea shipping. The development of the steamboat led to the larger steamship, which is a seaworthy and often ocean-going ship.

Steamboats sometimes use the prefix designation SS, S.S. or S/S (for 'Screw Steamer') or PS (for 'Paddle Steamer'); however, these designations are most often used for steamships.

The first steamboat designs used Newcomen steam engines. These engines were large, heavy, and produced little power, which resulted in an unfavorable power-to-weight ratio. The heavy weight of the Newcomen engine required a structurally strong boat, and the reciprocating motion of the engine beam required a complicated mechanism to produce propulsion.

James Watt's design improvements increased the efficiency of the steam engine, improving the power-to-weight ratio, and created an engine capable of rotary motion by using a double-acting cylinder which injected steam at each end of the piston stroke to move the piston back and forth. The rotary steam engine simplified the mechanism required to turn a paddle wheel to propel a boat. Despite the improved efficiency and rotary motion, the power-to-weight ratio of Boulton and Watt steam engine was still low.

The high-pressure steam engine was the development that made the steamboat practical. It had a high power-to-weight ratio and was fuel efficient. High pressure engines were made possible by improvements in the design of boilers and engine components so that they could withstand internal pressure, although boiler explosions were common due to lack of instrumentation like pressure gauges. Attempts at making high-pressure engines had to wait until the expiration of the Boulton and Watt patent in 1800. Shortly thereafter high-pressure engines by Richard Trevithick and Oliver Evans were introduced.

The compound steam engine became widespread in the late 19th century. Compounding uses exhaust steam from a high pressure cylinder to a lower pressure cylinder and greatly improves efficiency. With compound engines it was possible for trans ocean steamers to carry less coal than freight. Compound steam engine powered ships enabled a great increase in international trade.

The most efficient steam engine used for marine propulsion is the steam turbine. It was developed near the end of the 19th century and was used throughout the 20th century.

An apocryphal story from 1851 attributes the earliest steamboat to Denis Papin for a boat he built in 1705. Papin was an early innovator in steam power and the inventor of the steam digester, the first pressure cooker, which played an important role in James Watt's steam experiments. However, Papin's boat was not steam-powered but powered by hand-cranked paddles.