0" 262' 0"
Overall width 32' 0" 35' 6" 49' 3" 56' 9"
Overall height 46' 0" 49' 0" 57' 6" 69' 3"
Hydrogen capacity
(cubic feet) 70,000 100,000 210,000 360,000
Gross lift (lb.) 4,900 7,000 14,500 24,300
Disposable
lift (lb.) 1,850 2,200 4,850 8,500
Crew 3 4 5 10
Lift available
for fuel and
freight (lb.) 1,370 1,540 4,050 6,900
Petrol consumption
at full speed
(lb. per hour) 3.6 7.2 18.4 29.8
Gals. per hour 0.36 0.72 2.05 3

CHAPTER VII

NAVAL AIRSHIPS.--THE RIGIDS--RIGID AIRSHIP No. 1

The responsibility for the development the Rigid airship having been
allotted to the Navy, with this object in view, in the years 1908 and
1909 a design was prepared by Messrs. Vickers Ltd., in conjunction with
certain naval officers, for a purely experimental airship which should
be as cheap as possible. The ship was to be known as Naval Airship No.
1, and though popularly called the Mayfly, this title was in no way
official. In design the following main objects were aimed at:

1. The airship was to be capable of carrying out the duties of an
aerial scout.

2. She was to be able to maintain a speed of 40 knots for
twenty-four hours, if possible.

3. She was to be so designed that mooring to a mast on the water
was to be feasible, to enable her to be independent of her
shed except for docking purposes, as in the case with surface
vessels.

4. She was to be fitted with wireless telegraphy.

5. Arrangements were to be made for the accommodation of the crew
in reasonable comfort.

6. She was to be capable of ascending to a height of not less
than 1,500 feet.

These conditions rendered it necessary that the airship should be of
greater dimensions than any built at the time, together with larger
horse-power, etc.

These stipulations having been settled by the Admiralty, the Admiralty
officials, in conjunction with Messrs. Vickers Ltd., determined the
size, shape, and materials for the airship required. The length of the
ship was fixed at approximately 500 feet, with a diameter of 48 feet.
Various shapes were considered, and the one adopted was that
recommended by an American professor named Zahm. In this shape, a
great