The Overlooked Origins of the Jet-Powered Boat

By Sam Moore
Published on January 3, 2014
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A replica of James Rumsey’s steamboat in front of a mural showing the crowd of onlookers on the wharf on the date of the public trial in December 1787.
A replica of James Rumsey’s steamboat in front of a mural showing the crowd of onlookers on the wharf on the date of the public trial in December 1787.
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Portrait of James Rumsey, probably painted by George W. West.
Portrait of James Rumsey, probably painted by George W. West.
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The James Rumsey monument erected in the early 1900s along the bank above the Potomac River at Shepherdstown, W. Va., by the Rumseian Society.
The James Rumsey monument erected in the early 1900s along the bank above the Potomac River at Shepherdstown, W. Va., by the Rumseian Society.
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Live Stream is allowed into the Steam Cylinder by the Control Valve and pushes up the Steam Piston. The Connecting Rod pulls up the Water Piston, thus drawing water in through the River Valves into the Water Cylinder. At the top of the stroke the Control Valve is flipped to start the thrust, or vacuum, stroke.
Live Stream is allowed into the Steam Cylinder by the Control Valve and pushes up the Steam Piston. The Connecting Rod pulls up the Water Piston, thus drawing water in through the River Valves into the Water Cylinder. At the top of the stroke the Control Valve is flipped to start the thrust, or vacuum, stroke.
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When the Control Valve is flipped, the Steam Cylinder is connected to the Condenser, which condenses the steam, creating a vacuum. Because of the vacuum in the Steam Cylinder, air pressure now pushes the Steam Piston and Water Piston down, forcing water out of the Water Cylinder, through the Truck Line and out the stern. By reaction, this mass of water thrown backward propels the boat forward, in the same way as a jet or rocket.At the same time, more water is pumped into the Water Tube Boiler by the Injector Pump, and condensed water and trapped air are pumped out of the Condenser by the Air Pump.Notice the water passing through the Trunk Line Flapper Valves during the Steam Stroke? These allow water from the Thrust Stroke to continue moving out the Trunk Line during the intake of new water through the River Valves.
When the Control Valve is flipped, the Steam Cylinder is connected to the Condenser, which condenses the steam, creating a vacuum. Because of the vacuum in the Steam Cylinder, air pressure now pushes the Steam Piston and Water Piston down, forcing water out of the Water Cylinder, through the Truck Line and out the stern. By reaction, this mass of water thrown backward propels the boat forward, in the same way as a jet or rocket.At the same time, more water is pumped into the Water Tube Boiler by the Injector Pump, and condensed water and trapped air are pumped out of the Condenser by the Air Pump.Notice the water passing through the Trunk Line Flapper Valves during the Steam Stroke? These allow water from the Thrust Stroke to continue moving out the Trunk Line during the intake of new water through the River Valves.

Look across any fairly large body of water on a warm summer day and you’ll see the high plume of water that marks the passage of someone on a jet ski. (Jet Ski is a registered brand name of Kawasaki Motors, Inc., but seems to have been adopted as a generic name for all personal watercraft.)

Jet boats and Jet Skis are all the rage these days; besides the popular one- or two-passenger Jet Skis, passenger and car ferries, excursion boats, and other small to medium-sized, high-speed boats for myriad uses have been developed. The South African navy has four 3,700-ton jet-propelled frigates, and the amphibious assault vehicle that was being designed for the U.S. Marine Corps a few years ago (and canceled in 2011 by then Defense Secretary Robert Gates as it was too expensive) was to be water jet-propelled while in the water.

Sir William Hamilton is credited (in the 1950s) with developing the jet boat to ply the shallow rivers of his native New Zealand where conventional propellers often struck bottom. However, a modern fun seeker skimming over a lake at high speed on a jet ski would undoubtedly be astonished to learn that the first jet-powered boat was powered by a steam engine. And even more amazingly, it was first launched in 1787!

A chance meeting

In 1783, after the end of America’s Revolutionary War, Gen. George Washington resigned his commission and retired to Mount Vernon and his farm. Washington owned large tracts of land in western Virginia and Kentucky and dreamed of opening a waterway to these lands using the western headwaters of the Potomac River, which, of course, flowed past Mount Vernon’s doorstep. In September 1784, Washington set out on a trip west to explore the possibilities of the upper Potomac.

He stopped at Bath, Va. (now Berkeley Springs, W. Va.), to “take the waters” and stay at the inn operated by 31-year-old James Rumsey. A personable man, Rumsey charmed the general and showed him a working model of a mechanical boat he had devised. The little boat had a paddle wheel in its center that was connected by a crank to a long pole outside each gunwale. Rumsey placed the model into a fast-running little stream and the current spun the wheel, which moved the poles alternately against the stream bottom. Before Washington’s skeptical eyes, the poles pushed the boat upstream against the current using only the power of the stream itself!

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