the propellers through
two gear wheels only. The propeller gear box is supported by steel
tube outriggers attached by brackets to the framework of the car. The
petrol is carried in a series of tanks situated beneath the keel
walking way, and are interconnected so that any tank either forward or
aft can supply any engine, by this means affording assistance for the
trimming of the ship.

Four-bladed propellers are used throughout the ship.

Water ballast is carried in fabric bags also situated beneath the keel
walking way, and a certain amount is also carried beneath the floor of
the car.

Engine-room telegraphs, swivelling propeller telegraphs, speaking tubes
and telephones, with a lighting set for the illumination of the cars
and keel, were all fitted in accordance with the practice standard in
all rigid airships.

The lift and trim trials taken before the initial flight trials showed
that the ship possessed a disposable lift under standard conditions of
5.7 tons. The original disposable lift demanded by the specification
was 3 tons but this was reduced by 2 tons owing to the machinery
weights being 2 tons in excess of the estimate. Since then these
weights had been increased by another half-ton, making a total of 2 1/2
tons over the original estimate. It was evident that with so small a
margin of lift these ships would never be of real use, and it was
decided to remove various weights to increase the lift and to
substitute a wing car of a similar type to those manufactured for the R
33 class for the heavy after car at present in use.

R 23 carried out her trials without the alteration to the car, which
was effected at a later date, and the same procedure was adopted with R
24 and R 25. In the case of R 26, however, she had not reached the
same stage of completion as the other two ships, and the alterations
proposed for them were embodied in her during construction. The
gasbags were of lighter composition, all cabin furniture was omitted
and the wing car was fitted in place of the original after car. This
wing car is of streamline shape with a rounded bow and tapered stern.
The lower portion is plated with duralumin sheets and the upper part is
covered with canvas attached to light wooden battens to give the
necessary shape. This effected a very considerable reduction in
weight. The original 250 horse-power Rolls Royce engine was installed,
now driving a single large two-bladed propeller astern. A test