ZMC-2 - AbsoluteAstronomy.com

The ZMC-2 (Zeppelin Metal Clad 200,000 ft. capacity) was the only successfully-operated metal-skinned airship

Airship

An airship or dirigible is a type of aerostat or "lighter-than-air aircraft" that can be steered and propelled through the air using rudders and propellers or other thrust mechanisms...

ever built. Constructed at Naval Air Station Grosse Ile

Naval Air Station Grosse Ile

Naval Air Station Grosse Ile was a Naval air station located on the southern tip of Grosse Ile, Michigan. It operated from 1927 until late 1969, and is now a township airport. During World War II NASGI was one of the largest primary flight training stations for Naval aviators, and RAF pilots...

by The Aircraft Development Corporation of Detroit, the ZMC-2 was operated by the U.S. Navy at Lakehurst, New Jersey

Lakehurst, New Jersey

Lakehurst is a Borough in Ocean County, New Jersey, United States. As of the United States 2010 Census, the borough population was 2,654.Lakehurst was incorporated as a borough by an Act of the New Jersey Legislature on April 7, 1921, from portions of Manchester Township, based on the results of a...

from 1929 until its scrapping in 1941. While at Lakehurst it completed 752 flights, and logged 2265 hours of flight time.

Development

The ZMC-2 was built in Grosse Ile, Michigan

Grosse Ile Township, Michigan

Grosse Ile Township is a general law township of Wayne County in the U.S. state of Michigan. The township is situated on several islands in the Detroit River, but the largest island is also referred to as simply Grosse Ile. The name comes from French Grosse Île, meaning "Big Island"...

by the Aircraft Development Corporation, a division of Detroit Aircraft Corporation

Detroit Aircraft Corporation

The Detroit Aircraft Corporation was incorporated in Detroit, Michigan on July 10, 1922, as the Aircraft Development Corporation. The name was changed in 1929...

, on a site shared with, and later acquired by Naval Air Station Grosse Ile

Naval Air Station Grosse Ile

. The ZMC-2 was the brainchild of Ralph Hazlett Upson, a balloonist and engineer who had previously won the Gordon Bennett Cup

Gordon Bennett Cup

There were three Gordon Bennett Cups, all established by James Gordon Bennett, Jr.*Gordon Bennett Cup in auto racing*Gordon Bennett Cup in ballooning — for a time, a separate cup was also awarded for powered air racing...

for Balloon racing in Europe, bringing the cup to the United States for the first time. Upson teamed up with Carl B. Fritsche of Detroit and together they formed the Detroit Aircraft Corporation, with backing from Henry Ford

Henry Ford

Henry Ford was an American industrialist, the founder of the Ford Motor Company, and sponsor of the development of the assembly line technique of mass production. His introduction of the Model T automobile revolutionized transportation and American industry...

and Edsel Ford

Edsel Ford

Edsel Bryant Ford , son of Henry Ford, was born in Detroit, Michigan, USA. He was president of Ford Motor Company from 1919 until his death in 1943.-Life and career:...

, as well as Charles Kettering

Charles Kettering

Charles Franklin Kettering was an American inventor, engineer, businessman, and the holder of 186 patents. He was a founder of Delco, and was head of research for General Motors for 27 years from 1920 to 1947. Among his most widely used automotive inventions were the electrical starting motor and...

of General Motors

General Motors

General Motors Company , commonly known as GM, formerly incorporated as General Motors Corporation, is an American multinational automotive corporation headquartered in Detroit, Michigan and the world's second-largest automaker in 2010...

, Alex Dow, president of Detroit Edison

Detroit Edison

The Detroit Edison Company, founded in 1903, is an investor-owned electric utility which serves most of Southeast Michigan. Its parent company, DTE Energy , provides energy services to a variety of clients beyond Detroit Edison's service area.- History :...

, and William B. Stout, a local industrialist. The airship was constructed in a special blimp hangar built in 1925 for the construction of the ZMC-2, and expandable for the construction of much larger metal-clad zeppelins the company envisioned would be produced later. The hangar measured 120' high, 120' wide and 180' long, and remained the largest structure on the Naval Air Station property until 1960, when it was dismantled and the roof reused in the construction of a bowling alley in nearby Trenton, Michigan

Trenton, Michigan

Trenton is a small city in Wayne County in the southeast portion of the U.S. state of Michigan. As of the 2010 census, the city population was 18,853...

.

The ZMC-2 was nicknamed the "Tin

Tin

Tin is a chemical element with the symbol Sn and atomic number 50. It is a main group metal in group 14 of the periodic table. Tin shows chemical similarity to both neighboring group 14 elements, germanium and lead and has two possible oxidation states, +2 and the slightly more stable +4...

Bubble" and was also sometimes called a "tinship". The skin was not tin but Alclad

Alclad

Alclad is a trademark of Alcoa used as a generic term to describe corrosion resistant aluminium sheet formed from high-purity aluminium surface layers metallurgically bonded to high strength aluminium alloy core material. These sheets are commonly used by the aircraft industry...

. The airship was roughly teardrop shaped and had eight small stabilizer

Stabilizer (aircraft)

In aviation, a stabilizer provides stability when the aircraft is flying straight, and the airfoil of the horizontal stabilizer balances the forces acting on the aircraft....

fins, four of which had rudder

Rudder

A rudder is a device used to steer a ship, boat, submarine, hovercraft, aircraft or other conveyance that moves through a medium . On an aircraft the rudder is used primarily to counter adverse yaw and p-factor and is not the primary control used to turn the airplane...

s. It was held together with over 3.5 million rivet

Rivet

A rivet is a permanent mechanical fastener. Before being installed a rivet consists of a smooth cylindrical shaft with a head on one end. The end opposite the head is called the buck-tail. On installation the rivet is placed in a punched or pre-drilled hole, and the tail is upset, or bucked A rivet...

s., which were applied by an innovative sewing machine-like device which produced airtight seams.

The ZMC-2 was 52 feet in diameter and 150 feet long. The control car was 24 feet long by 6 feet wide. It contained three fuel tanks to give a maximum cruising range of about 600 miles. The ZMC-2 was powered by two Wright Whirlwind J5 engines of 200 hp each, carried on outriggers and mounted in a tractor arrangement, rather that the pusher position usually employed on blimps. At first the landing gear was an unusual hollow steel ball about the size and shape of a football, mounted on a tripod attached to the car. This was done to create a shape with less drag in order to guarantee the Navy's requirement of a 62 mph top speed. Later, after the ZMC-2 had attained this speed with ease, the ball was replaced with a conventional swiviling soft tire.

The crew consisted of a pilot, copilot and flight engineer-navigator, with space for one or two additional passengrs.

Assembly

The ZMC-2 was constructed out of Alclad

Alclad

, an aluminum alloy sheet clad with a very thin skin of pure aluminum on each side with the high corrosion resistance of pure aluminum and the high tensile strength of the alloy. The resulting material was about as strong as carbon or mild steel. The downside was that Alclad was thicker than sheet aluminum, making the ship several hundred pounds heavier than originally envisioned. The aircraft was already under construction, and over 20 feet of the nose completed using Duraluminum when the decision was made to switch to Alclad. The reason for the switch was that duraluminum is highly susceptible to rust, particularly in a salt water environment, the exact sort of environment a Navy blimp operates in. The ZMC-2 was the first aircraft of any kind constructed from Alclad, and no previous experience could be drawn upon for its handling.

To assemble the ZMC-2 a skin-riveting machine was developed by the Aviation Tool Co., a division of the Detroit Aircraft Corporation

Detroit Aircraft Corporation

The Detroit Aircraft Corporation was incorporated in Detroit, Michigan on July 10, 1922, as the Aircraft Development Corporation. The name was changed in 1929...

. The device was invented by Edward J. Hill, who had come to work on the ZMC-2 after leaving the Naval Aircraft Factory

Naval Aircraft Factory

The Naval Aircraft Factory was established by the United States Navy in 1918 at Philadelphia in order to assist in solving the problem of aircraft supply which faced the Navy Department upon the entry of the U.S. into World War I...

in Philadelphia, Pennsylvania

Philadelphia, Pennsylvania

Philadelphia is the largest city in the Commonwealth of Pennsylvania and the county seat of Philadelphia County, with which it is coterminous. The city is located in the Northeastern United States along the Delaware and Schuylkill rivers. It is the fifth-most-populous city in the United States,...

. The machine consisted of an aluminum casting, weighing about 100 pounds, and was supported on springs from a framework that ran on concentric circular rails set into the floor of the hangar. There were two sets of circular rails, one at each end of the building. Three riveting machines were made, one for each set of tracks, and one for reserve when repairs might be needed. The reason for two sets of tracks was that the hull was built in two sections, front and rear. Each end started from a circular plate suspended from the hangar roof by a cable and free to rotate as each 18 inch wide strip Alclad was added. In this manner, each end of the ship slowly grew as succeeding rows were added, looking like a bulls eye at first and later like a huge inverted teacup. Both sections were under construction continuously 24 hours a day, seven days a week, once the hull was started. The riveting machine fed three small aluminum wires from large spools to make a seam about a quarter inch wide composed of three rivets, one above the other in a staggered pattern. In theory the machine could sew about 50 feet of seam in an hour, but in practice about 10 or more feet was the average. The sheets of Alclad used were eight to nine thousandths of an inch thick. As the each section of the hull grew internal annular rings were added at appropriate distances to give stiffness and reinforcement to the hull skin. In addition, lightweight longitudinal channels were added between the circular rings, giving the internal structure the appearance of a huge bird cage. The Helium

Helium

Helium is the chemical element with atomic number 2 and an atomic weight of 4.002602, which is represented by the symbol He. It is a colorless, odorless, tasteless, non-toxic, inert, monatomic gas that heads the noble gas group in the periodic table...

gas was contained by the hull only, no fabric was used to contain the helium. Inside the hull were two large airbag cells, called balloonets, made of rubberized fabric and containing air. These cells could be expanded or contracted to control pressure as the helium expanded or contracted with the heating or cooling of the atmosphere. In operation the ZMC-2 was susceptible to heating and cooling affects of the sun causing it to pop and buckle in the evenings if pressure from blowers was not applied. During its service life the ZMC-2 was found to have a gas diffusion rate much lower than that of fabric-hulled blimps, meaning that a much longer time would pass before additional helium needed to be added.

As the airship neared completion a decision had to be made on how best to fill it with Helium. Once the two halves were completed they were suspended horizontally from cables attached to the hangar ceiling, and the two halves were joined with a final array of rivets. Since Helium mixes freely with air it was impossible to pump Helium directly into the airship until the air was removed. It was decided that the airship would first be filled with CO2, a heavy gas. Once filled with CO2 the Helium could be pumped in under pressure from valves at the top of the chamber, forcing the CO2 out through valves located on the bottom. Only a few weeks before this procedure was to begin a bright young engineer noted that once filled with CO2 the ZMC-2 would be many thousands of pounds heavier than when filled with air. The rest of the airship's assembly had to be postponed for several weeks while additional reinforcing panels and stronger connectors were attached in order to support the increased weight of the CO2 filled airship.

Operations

The airship was first flown on August 19, 1929, and transferred to Lakehurst, New Jersey

Lakehurst, New Jersey

in October 1929. The airship was nicknamed "the Tin Blimp". Her first Navy skipper was Red Duggan, who expressed reluctance at operating the airship, believing it unsafe. Duggan's concerns would be proven wrong, though he would later lose his life in the crash of another airship, the USS Akron.

As a sub-scale test vehicle, it was considered to be very successful, but the company that built it did not weather the Great Depression

Great Depression

The Great Depression was a severe worldwide economic depression in the decade preceding World War II. The timing of the Great Depression varied across nations, but in most countries it started in about 1929 and lasted until the late 1930s or early 1940s...

well, and by the time a successor might have been built, there was little interest in pursuing it. In the year before the Depression, the US Army was seeking funding for an airship based on the ZMC-2, that would have been larger than the German Graf Zeppelin, and powered by eight engines of 600 hp to 800 hp. The US Army was planning to use it as a tender for air launched aircraft similar to plans the US Navy had for its future dirigibles. The $4.5 million dollars need for construction was never approved by Congress.

The ZMC-2 was operated with a zero internal pressure at speeds up to 20 mph, sufficient for it to be considered a 'rigid' airship. With its low fineness ratio

Fineness ratio

Fineness ratio is a term used in naval architecture and aerospace engineering to describe the overall shape of a streamlined body. Specifically, it is the ratio of the length of a body to its maximum width; shapes that are "short and fat" have a low fineness ratio, those that are "long and skinny"...

of 2.83, the ZMC-2 was difficult to fly. By 1936 the airship had traveled over 80,000 miles with little signs of corrosion. In its lifetime the ZMC-2 logged 752 flights and 2265 hours of flight time. In its final years its use had dropped significantly. Between December 1938 and April 1941 it only logged 5 hours flight time.

It was scrapped in 1941, reaching its planned lifetime after more than 10 years of service. Other, more conventional blimp

Non-rigid airship

A blimp, or non-rigid airship, is a floating airship without an internal supporting framework or keel. A non-rigid airship differs from a semi-rigid airship and a rigid airship in that it does not have any rigid structure, neither a complete framework nor a partial keel, to help the airbag...

s did go on to serve in World War 2

World War II

World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...

Specifications (ZMC-2)

ZMC-2 in Popular Culture

The ZMC-2 plays a key role in the Clive Cussler

Clive Cussler

Clive Eric Cussler is an American adventure novelist and marine archaeologist. His thriller novels, many featuring the character Dirk Pitt, have reached The New York Times fiction best-seller list more than seventeen times...

novel Cyclops (1986) in which it is fictionally saved from scrapping and renamed Prospertier.

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