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.
Towards the end of 1909 a new aluminium alloy was discovered,
known as duralumin. Tests were made which proved that this new
metal possessed a strength of twenty-five tons per square inch,
which was over twice as strong as the nominal strength of
aluminium, and in practice was really five times stronger. The
specific gravity of the new metal varied from 2.75 to 2.86, as
opposed to the 2.56 of aluminium. As the weights were not much
different it was possible to double the strength of the ship and
save one ton in weight. Duralumin was therefore at once adopted.
The hull structure was composed of twelve longitudinal duralumin
girders which ran fore and aft the length of the ship and
followed the external shape.
Pages:
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122