of the longitudinal huff framework is parallel sided with curved
bow and stern portions, the radius of these curved portions
being, in the case of the bow, twice the diameter of the hull,
and in the case of the stern nine times the same diameter.
Experiments proved that the resistance of a ship of this shape
was only two-fifths of the resistance of a ship of the same
dimensions, having the 1 1/2 calibre bow and stern of the
Zeppelin airships at that time constructed.

A considerable difference of opinion existed as to the material
to be chosen for the construction of the hull. Bamboo, wood,
aluminium, or one of its alloys, were all considered. The first
was rejected as unreliable. The second would have been much
stronger than aluminium, and was urged by Messrs. Vickers. The
Admiralty, however, considered that there was a certainty of
better alloys being produced, and as the ship was regarded as an
experiment and its value would be largely negatived if later
ships were constructed of a totally different material, aluminium
or an alloy was selected. The various alloys then in existence
showed little advantage over the pure metal, so pure aluminium
was specified and ordered. This metal was expected to have a
strength of ten tons per square inch, but that which arrived was
found to be very unreliable, and many sections had, on test, only
half the strength required. The aluminium wire intended for the
mesh wiring of the framework was also found to be extremely
brittle. A section of the framework was, however, erected, and
also one of wood, as a test for providing comparisons. In the
tests, the wooden sections proved, beyond all comparison, the
better, but the Admiralty persisted in their decision to adopt
the metal.