FLY RC Snapshot: Recreating the USS Macon...

Recreating the USS Macon

By Jack Clemens

 

Every once in a while a model comes along that stops you in your tracks. This unique airship designed and built by Jack Clemens is a perfect example of such a project and we are honored to present it to you here at FlyRC.com.

 

 

How else can you build a model at 1/40 scale and still qualify as an RC Giant?

 

MOTIVATION

I had done a lot of modeling in my youth in the 1940’s. Family and job kept me away from any serious projects during my adult life and so my pent up urges had to wait until I retired in2002.

 

A poignant 1930's photo of a cavernous Hangar One at Moffett Field in Sunnyvale California—empty, illuminated, and awaiting the Navy’s giant flying aircraft carrier which was never to return—started the process. The cavernous Hangar One just off Highway 101 is nothing more than an oddity to most of the thousands of motorists that pass by every day. It struck me that it would be a fitting tribute to aeronautical history to return the Macon to its hangar in the form of a model. So began the effort to create a replica of the earliest hi-tech project on the San Francisco peninsula and fly the Macon one last time in its home.

 

HISTORY

The history of the Macon is well documented. In brief summary it was a giant dirigible capable of carrying, launching, and retrieving scouting aircraft to serve as the pre-radar “eyes of the fleet.” Distinguished from the more common teardrop shaped balloons known as blimps that dangerously distorted when flown at high speeds, the Macon employed a rigid interior airframe which held its aerodynamic shape at any operating speed. First flown in April 1933, the Macon operated out of Moffett Field in support of the Pacific Fleet until it was lost in a weather related accident off the California coast in Monterey Bay in February 1935.

 

The airship had a  rigid exterior airframe containing 12 gasbags for buoyancy, a hangar deck housing up to five Curtiss F9C "Sparrowhawk" airplanes, a trapeze device for launching and retrieving the aircraft, crew quarters for 50 men, eight directed thrust motors, and an under slung command control cabin. The airframe was constructed from lightweight duralumin girders running the length of the cigar shaped hull with 12 main frames forming the circular cross sections. The airship was immense at 785 feet in length and over 130 feet in diameter. 6,500,000 cubic feet of helium filled the interior and provided the lift necessary for flight.

 

CONSTRUCTING THE MODEL

A request to the Smithsonian resulted in many archived photos and an overall drawing of the airship interior. Construction that matched the original seemed the best approach using balsa wood as the structural material for light weight. Very thin, 50 micro-inch metalized mylar was selected as the lightest material available to contain the helium. Computer modeling allowed some fairly decent estimates of weight and lift. When scaling models, weight of the sheeting materials increases as a square of dimensions whereas lift increases as a cube function, so bigger tends to be better with airships. My calculations showed a size of at least 20 feet in length would be necessary for the model to achieve buoyancy. A scale of 1 inch to 1 meter provided the required size and would just fit diagonally in our two-car garage. Patterns for the gas bags just fit onto the available 4 foot wide rolls of mylar.