er
be overlooked, and it was decided to make another attempt to build a
rigid airship in conformity with existing Zeppelin construction. The
first proposals were put forward in 1913, and, finally, after eleven
months delay, the contract was signed. This airship, it has been seen,
was designated No. 9.

No. 9 experienced numerous vicissitudes, during the process of design
and later when construction was in progress. The contract having been
signed in March, 1914, work on the ship was suspended in the following
February, and was not recommenced until July of the same year. From
that date onwards construction was carried forward; but so many
alterations were made that it was fully eighteen months before the ship
was completed and finally accepted by the Admiralty.

The ship as designed was intended "to be generally in conformity with
existing Zeppelin construction," with the following main requirements
stipulated for in the specification:

1. She was to attain a speed of at least 45 miles per hour at the
full power of the engines.

2. A minimum disposable lift of five tons was to be available for
movable weights.

3. She was to be capable of rising to a height of 2,000 feet
during flight.

The design of this ship was prepared by Messrs. Vickers, Ltd., and as
it was considered likely that owing to inexperience the ship would
probably be roughly handled and that heavy landings might be made, it
was considered that the keel structure and also the cars should be made
very strong in case of accidents occurring. This, while materially
increasing the strength of the ship, added to its weight, and coupled
with the fact that modifications were made in the design, rendered the
lift somewhat disappointing. The hull structure was of the "Zahm"
shape as in No. 1, a considerable portion being parallel sided, while
in transverse section it formed a 17-sided polygon. In length it was
526 feet with a maximum diameter of 53 feet. The hull framework was
composed of triangular duralumin girders, both in the longitudinal and
transverse frames, while the bracing was carried out by means of high
tensile steel wires and duralumin tubes. Attached to the hull was a
V-shaped keel composed of tubes with suitable wire bracings, and in it
a greater part of the strength of the structure lay. It was designed
to withstand the vertical forces and bending moments which resulted
from the lift given by the gasbags and the weights of t