The lighter-than-air balloon has been around for
more than 150 years. French Engineer Henri Giffard
experimented with steerable airships as far back as 1852.
He powered his dirigible using a 250-pound, 3-hp steam
engine—along with a boiler and “coke” (coal) to fire it. He
succeeded in flying a small circle in a light breeze, but his
work went no further.
The next notable effort was by the French army in
1884. The La France used an electric motor and batteries
weighing 1,000 pounds. It could fly at 14 mph and return
to its starting point if the winds were very light; however,
the elongated balloon design had a limited range.
Then along came Alberto Santos-Dumont who built
and flew several single-person airships; the first in 1898
was known as Santos-Dumont No. 1. (In comparison,
Count Ferdinand Graff von Zeppelin flew his No. 1 in
1900.) Dumont’s No. 1 was 82. 5 ft. long with an envelope
diameter of 11. 5 ft. holding 6,354 cubic feet of hydrogen
and powered with a 3. 5 hp petroleum engine. By 1901,
Dumont, flying his No. 6, succeeded in winning the
Deutsch Prize by successfully completing a 14-mile circuit
from Park Saint Cloud, circling the Eiffel Tower, in 29. 5
minutes. His sixth design was 110 feet long, 20 feet in
diameter, and powered by a 242-pound, four-cylinder,
12-hp engine.
More than a century later Marvin is building balloons in Ardmore. An instrument-rated pilot who owns
a couple of Bonanzas, Marvin also flies hot air balloons.
“I’ve been an aviation enthusiast since I can remember,”
he said. “Everybody builds airplanes, so I decided to
build blimps.”
Above: Hangaring a blimp presents some unusual problems.
Marvin built his own “air dock” for the 80-foot long blimp No. 5.
Below: Volunteers help Marvin attach the “aluminum car” to the
bottom of the blimp. It can seat a pilot and pasenger and act as
a mount for one of the two engines that help direct the airship.
You can’t go to a kit supplier like Van’s Aircraft and pick
up a pre-engineered airship kit. To build an airship you
must begin with competent engineering and a good
understanding of an airship’s technical details, such as
how big it has to be and where to find special materials. Then you must determine how much a cubic foot of
helium can lift, how much the envelope will weigh, the
center of gravity, and the center of lift. What is a ballonet
and how is it used? How is lift controlled? What is the
best way to control steering and to ascend and descend
on command?
These concepts are far more complex than they may
first appear. Many people know the Goodyear blimps
have rudders and elevators. But until you fly one, you
can’t comprehend how slow they are to react. A number
of other control systems are needed to successfully fly an
airship. In the history of airship design, one discovers
all kinds of contraptions used in an effort to control the
flight. Dumont moved sand bags forward or aft to tip the
nose up or down. He used a small centrifugal blower just
above the propeller shaft to supply pressurized air to a
ballonet (an air-filled bag inside the envelope) through a
hose. This was used to pressurize the lifting gas to control
lift. There are many concepts for airship control, and a
designer has to make choices to achieve desired goals.
“I build my blimps ‘by guess and by gosh’ with no blueprints. Trial and error,” Marvin said. “I try this, and if it
doesn’t work, I try that until we benefit from my errors.”
The next big problem that has the potential to stifle
an airship project is the availability of a building large
enough to house an 80-foot long by 18.5-foot diameter
airship. Marvin was able to rent space in a large hangar,
but he eventually built his own hangar (or air dock) to
avoid the problems of shared hangar space. The cost of a
large hangar can be up to $50,000.
Another consideration is the cost of helium. Marvin
purchases the gas from local welding shops, and he said
it takes about 14,000 cubic feet of helium to fill the envelope. When he started this project eight years ago, the
cost was about $1,500 per filling. The cost today is near
$4,500. The helium cost might not be so bad if you could
fill the airship once and keep it, but it is very difficult to
keep the envelope from leaking. In a typical design, an
envelope can be made up of 12 gores with each having an
80-foot-long seam joining it to the next gore.
There are various ways to seal the gores together.
Marvin uses a pressure welding technique by which an
8-inch welding head creates a weld about an inch wide.
Two seams are lapped and the welding heads are aligned
lengthwise with the seam. The jaws are closed, placing
the seam under pressure and high temperature such that
the material partially melts and is bonded together. The
envelope material seam, or the welding machine, is then
moved about 8 inches and the process is repeated. For
the 80-foot seam the process is repeated some 130 times.
As more of the envelope is welded together it becomes
heavy to move; positioning the seam for an accurate weld
becomes more difficult. An accidental slip or bad weld
can make a very expensive leak.
Marvin estimated he has about 1,000 yards of material into this blimp. “You search until you find the right
material to use,” he said. He’s currently testing a material
