eased in
No. 23 to 535 feet, and the number of gasbags from seventeen to
eighteen. This gave a total volume of 997,500 cubic feet compared with
890,000 cubic feet in No. 9, with a disposable lift under specification
conditions of 5.7 tons as opposed to 3.8 tons.

The longitudinal shape of No. 23 is a modified form of "Zahm" shape,
the radius of the bow portion being twice the diameter of the parallel
portion, while the stern radius is three times the same diameter.

In design the hull framework is almost a repetition of No. 9,
particularly in the parallel portion, the same longitudinal and
transverse frames dividing the hull into compartments, with tubes
completely encircling the section between each main transverse frame.
The system of wiring the hull is precisely the same in both the ships,
and nets are employed in the same way.

The triangular section of keel is adhered to, but its functions in No.
23 are somewhat different. In No. 9 it was intended to be sufficiently
strong to support all the main vertical bending moments and shearing
forces, but in No. 23 it was primarily intended to support the
distributed weights of water ballast, petrol tanks, etc., between the
main transverse frames. Unlike No. 9, the keel is attached to the main
transverse frames only. The cabin and wireless cabin are disposed in
the keel in the same manner, and it also furnishes a walking way for
the total length of the ship.

The stabilizing fins, both vertical and horizontal, are similar to
those attached to No. 9, but the system of rudders and elevators is
totally different. In place of the box rudders and elevators in No. 9,
single balanced rudders and elevators are attached to the fins; they
have their bearing on the outboard side on the external girders of the
fins, which are extended for the purpose. The elevators and rudders
are composed of a duralumin framework, stiffened by a kingpost on
either side with bracing wires.

The bags, eighteen in number, are made of rubber-proofed fabric lined
with gold-beater's skin. It is interesting to note that the number of
skins used for the bags of a ship of this class is approximately
350,000. The system of valves is entirely different from that in No.
9. The Parseval type of valve with the pressure cone at the bottom of
the bag is omitted, and in the place of the two top valves in the
former ship are a side valve of the Zeppelin type entirely automatic
and a top valve entirely hand c