A proper treatment of the construction and properties of airship fabrics would require a book rather than an essay. In what follows, it is possible therefore to deal briefly only with the principal types of fabrics, classified according to the main functions of each, describing their structure and behaviour and the chief factors affecting their permanence when in service. There are, then three main classes :—

I. Fabrics for the envelopes of non-rigid airships.

II. Fabrics for the gasbags of rigid airships.

III. Fabrics for the outer covers of rigid airships.

In all cases low specific weight (expressed here in grammes per square metre) is clearly of the greatest importance.

I. Fabrics of this class must possess gas-holding properties, mechanical strength and pliability. The internal pressure (equal to about 30111ms. of water) which maintains the shape of the envelope sets up in its fabric considerable tension, and this is increased by the distributed weight of the whole ship.