Bushnell’s “Turtle”

The submarine is often thought of as a weapon of the 20th century. But the first submarine attack on an enemy warship was actually made during the American Revolution, in 1776.

Cutaway replica of Bushnell’s Turtle, on display in Groton CT

In 1775, after the Revolutionary War battle at Bunker Hill, the British forces in Boston were surrounded by the fledgling Continental Army of George Washington. After almost a year of constant cannon fire, the British General William Howe decided to withdraw in the summer of 1776, and moved his entire force to Halifax, Canada.

Having secured Boston, Washington now turned to New York. Holding this city would be difficult—not only was it surrounded by rivers and islands, but much of its population were Loyalists who opposed the Revolution and supported the Crown Government. But New York was a political target as much as it was a military objective—as one of the colony’s largest cities it had to be kept out of the hands of the British. Washington moved his troops and occupied several strategic spots on Long Island and Manhattan.

As expected, the British attacked New York in force. A fleet of 200 warships, commanded by Admiral Richard Howe—General Howe’s brother—arrived from London. Some 32,000 troops—the largest force ever sent to America by the British—landed in New York Harbor and, on August 27 at the Battle of Long Island, the Continental Army was defeated and forced to abandon much of the city. Desperate for a way to strike back at the British and break the naval blockade, Washington turned to a new contraption he had heard about that was secretly being built by a Patriot named David Bushnell.

Bushnell, a student at Yale, had been working on a way to explode a black powder bomb underwater to attack ships. Although he called his device a “torpedo”, it was more like a forerunner to the modern naval mine: it consisted of a wooden keg with 150 pounds of black powder, a clocklike apparatus connected to an ordinary flintlock firing mechanism to act as a timer, and a waterproof fuse to detonate the explosive. After a few months, he had perfected a reliable device. Now, he needed a good way to deliver it.

Working in secret in Connecticut with funding from the Continental Army, Bushnell and his brother Ezra constructed a one-man submarine. The odd-looking craft was made from wooden planks steam-bent into shape to form two domed ovals that were held together with iron hoops, like a flattened beer keg. The hull measured 7.5 feet tall and 6 feet across, and was just thick enough in the middle for a man to fit inside. The whole thing was waterproofed with a layer of pine pitch. Because it’s shape looked like two side-by-side turtle shells, Bushnell called the contraption the “Turtle”.

Everything inside the Turtle was hand-operated. The operator (Ezra) climbed inside through a waterproof hatch in the top, and sat on a wooden bar. There were two hand-cranked propellers: one of them drove the Turtle forward and backward, and the other raised or lowered it in the water. A tiller operated a rudder at the back for steering. The bottom of the Turtle was filled with 200 pounds of lead ballast which kept it upright in the water. To make the Turtle submerge, a pair of hand pumps would pull water in from the outside, flooding the bottom of the compartment (and submerging the operator up to his waist). To surface, the pumps would push the ballast water back out.

Navigation came from a single compass. Since the instruments could not be seen in the dark when submerged, the needles on the dials were covered with bioluminescent fungus to show their positions. (These stopped glowing if the temperature dropped too low, so the Turtle could not be used during the winter.) A cork floating in a tube gave a crude measure of depth. Since there was no air pump, the operator could only submerge for short periods until he began to run out of air and had to resurface.

To attack an enemy ship, the Turtle would stealthily approach the target on the surface and make its way alongside, then submerge. A pointed iron bar would make contact with the target’s wooden hull, and would be hand-cranked to screw it in securely. This bar was connected by a short length of rope to the mine, so when the Turtle withdrew, the mine remained attached to the target ship’s hull. Hours later, the clockwork timer would light the waterproof fuse and detonate the explosive.

By the time Admiral Howe’s fleet entered New York Harbor in 1776, the Turtle had undergone a series of successful tests (some of them witnessed by Benjamin Franklin) and was preparing for an actual combat mission. But, unexpectedly, Ezra Bushnell became sick and was no longer able to act as the submarine pilot. So a volunteer militiaman named Ezra Lee was recruited and hastily trained to take his place.

On September 6, 1776, the Turtle was ready for its first mission. The selected target was the frigate HMS Eagle—Admiral Howe’s own flagship. At 11pm Ezra Lee climbed into the Turtle, and began slowly making his way out into the harbor to the anchored ship.

He successfully made it to the Eagle and stopped alongside her, completely undetected by the lookouts. Carefully submerging, he then moved underneath the ship and came up to the bottom of the hull. But when he tried to attach the underwater mine, he had a problem. Naval ships of this time were made of wood (usually oak), and over time they became infested with marine organisms such as barnacles, shipworms and burrowing clams, which not only increased the drag and slowed the ship, but weakened the hull over time. To prevent this, the hulls were regularly coated with a mixture of beef fat, sulphur and pine resin, to kill the organisms and prevent new ones from re-attaching. But the British Navy had recently begun a new treatment, in which flat copper plates were attached to the underwater portions of the hull. The smooth copper not only prevented organisms from attaching themselves, but gave less friction in the water and produced a noticeably increased speed.

In the Turtle, Lee now tried twice to screw the mine onto the Eagle’s hull, but both times he hit the copper hull plating, and his hand-cranked screw was not able to penetrate it. Tired, cold, wet, and running out of breathable air, he had to abandon his mission and wearily paddled back to shore. The world’s first submarine mission would be unsuccessful.

Well, not entirely unsuccessful…..

After Lee and the Turtle surfaced and headed toward shore, the sun was just coming up, and a group of British sailors on a nearby island happened to spot the weird-looking thing and rowed out to investigate it. To lighten his load and to distract his pursuers, Lee now armed the mine and cut it loose, and the British sailors, not knowing what it was, quickly retreated back to shore. As the Turtle made it to safety, the loose mine now floated around in the harbor until its detonator went off, and the 150 pounds of black powder ignited in a tremendous explosion that rocked the harbor. American Army officers watching from shore heard the explosion and thought the Eagle had been successfully hit—they did not learn until later that the mission had failed.

The British intelligence network already had collected bits and pieces of information about Bushnell and his strange underwater craft, and eventually they pieced the story together. And although the attack had been a failure, the British Navy apparently took the threat seriously and began to keep their warships far enough away from shore, where they thought they would be out of reach. This had the unexpected beneficial side effect for the colonials of reducing the accuracy of the British shore bombardments.

The Turtle, meanwhile, was transported to the Hudson River after the fall of New York, where it made two more unsuccessful attempts to attack British ships near Fort Lee. The submarine was then lost when the ship that was transporting it down the Hudson was sunk by a British shore battery.

David Bushnell remained with the Continental Army for the rest of the war, and continued his work on explosive devices. Washington himself praised Bushnell’s Turtle as “an effort of genius”. In one incident in January 1778, Bushnell released a number of floating mines down the Delaware River towards the British fleet, causing minor damage to one ship. It became known as “The Battle of the Kegs”. After the war Bushnell was placed in command of the US Army Corps of Engineers at West Point.

In recent years a number of functional replicas of Bushnell’s Turtle have been built, most for use as props in movies or TV shows. In one odd incident, a performance artist in New York built a one-man sub from plywood and fiberglass, based on the Turtle’s design, and paddled it next to the Queen Mary 2—and was arrested by the Coast Guard.

A replica of the Turtle is on display at the USS Intrepid Museum in New York. Another, with cutaway sides to show the internal mechanisms, is exhibited at the US Submarine Force Museum in Groton CT.


3 thoughts on “Bushnell’s “Turtle””

  1. There is at least one British researcher who has concluded that Bushnell’s Turtle simply would not have worked at all, and that the Americans made up the whole story as a propaganda stunt.

Post a Comment

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s