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Aviation History
1920
1920 - 0666.PDF
JUNE 24, 1920 envelope, provided withrtransverse and lateral diaphragms,and of an outer one that completely surrouuds the former, a continuous and entirely free air space being left betweenthe two, the bottom portion of which forms the air ballonet. The air pressure in the latter is maintained during flight bymeans of air-intake valves located in the rigid nose of the envelope,- consisting of a large number of balanced blades.A mechanically-driven fan maintains air pressure when not in full flight. Excess of pressure is disposed of by meansof automatic air-relief valves located at the rear of the envelope where the aerodynamic influence of velocity is practicallynil. By this form of construction, the gas envelope is not only protected against the action of the sun, but it is relievedfrom all stresses due to velocity—-in fact, the conditions obtaining in the rigid are closely approached. The outerenvelope is plain varnished silk, strengthened by a series of closely-set longitudinal and circumferential bands fittedto its inner surface, and suitably connected to the inner envelope. It is connected to the underside of the rigidframe by two catenary bands, and the bottom portion of the envelope can be opened up longitudinally, exposing to viewfor inspection or repair the frame, suspension and gas envelope. The inner or gas envelope is divided into numerous inde-pendent gas-tight compartments by transverse and longi- tudinal diaphragms, the latter radiating from the fore andaft axis of the envelope, where a strong " axial band " is formed. From this band is suspended the rigid girder frameby a wire suspension. The envelope is of silk, the longitudinal diaphragms being of plain natural silk, and the transversediaphragms of gummed and varnished silk. The suspension band is of nine-fold silk. Each gas compartment has itsown gas relief valve, acting as a safety valve or control valve. In the former case, they are operated directly andautomatically by the lower portion of the envelope, by means of a rope, and in the latter pneumatically. The connection between the girder and the envelope isby means of wire-rope ribs leading^n pairs from the junction knots in the upper extremity of the girder to the undersideof the suspension band, the bottom edge of which consists of a series of catenaries ; whilst further lateral connectionsare provided to retain the top portion of the envelope in true form. Thus it will be seen that the whole suspension—the car being practically speaking integral with the girder frame—is concentrated about the axis of the ship, resultingin an exceptionally rigid construction. The frame or backbone of the ship, as previously stated,is contained within the envelope, and consists of an entirely rigid triangular lattice girder extending from end to end ofthe ship, and including the nose. Projecting as it does upwards within the envelope, it divides the lower portion ofthe gas envelope. It is built up of steel tubes braced with diagonal steel wires, and carries the car, control surfaces,etc. The girder is designed to withstand any stresses that may arise from abnormal flying conditions (pitching, etc.),or uneven distribution of load due to the partial or total deflation of any of the gas compartments. The car, also ofsteel tube construction, is suspended from the girder-frame by rigid tubular connections, and is arranged almost flushwith the envelope. It is almost completely enclosed, the covering being of fabric, and the nose is provided with glasswindows. A shaft extends upwards through the envelope from the car to a gun platform on the top of the envelope.The stiffening of the nose is carried out by a rigid conical cap, from which a set of slightly elastic ribs extend rearwardsto support the forward portion of the outer envelope. The whole " umbrella " is rigidly connected to the girder-frame. The control and stabilising surfaces are in two groups,the former, for steering the ship vertically and horizontally, being located at the stern of the ship, whilst the latter arearranged admidships. These stabilising surfaces consist of two groups of superimposed horizontal planes, mounted oneon each side of the car. The control surfaces consist of two symmetrical grids, comprising vertical and horizontal surfaces,mounted on the end of the rigid girder or keel. None of these surfaces are hinged, but they are flexible, having theirleading edges firmly fixed and being warped for the required horizontal and vertical control. They are operated throughan irreversible worm gear. Except in the case of models F. 3, F. 6 and F. 7, theForlanini dirigibles are equipped with two engine (the others have four), which are mounted tandem-fashion on the floorof the car, and drive through a friction clutch and gear-box two four-bladed air screws, one mounted on each side, of thecar. The gear-box is so designed that either engine can drive any one, or both air screws as desired. Should oneengine stop, it is kept warm by the running engine, thus facilitating starting and preventing the water and oil freezingat low temperatures. The air screws are of the adjustable reversible pitch type, similar to those on the M. and V. type.The following table gives comparative characteristics of the various Eorlanini dirigibles, Nos. F. 3 to F. 7 :— 666 ,<,-,,,-,,,,: —;,..-.,,V,,,,V,,v,.
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