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Aviation History
1932
1932 - 0310.PDF
FLIGHT, APRIL 1, 1932 AIR TRANSPORT The Breda 32 Commercial Monoplane Concluded from p. 260.) IN last week's issue the general features of the Breda 32 were dealt with. This week we propose to review briefly the structural design of this interesting Italian machine The fuselage of the Breda 32 is an all-metal structure in which the duralumin skin assists in stabilising the in ternal framework. The latter is composed of four longerons placed in the corners in the usual manner, joined by vertical and horizontal struts, and braced by the metal skin. The longerons and many of the fuselage struts are of built-up box section, corrugations being used in the walls of the longerons for stiffening them under com pression loads. The boxes are so designed that all rivets are external, and easy to get at for riveting and holding up. In the curved roof of the cabin the con struction is slightly different, the cross members being in the form of cambered deck beams and the skin bracing reinforced by diagonal members running from corner to corner in the bays, crossing each other in the centre. The roof construction of the Breda 32 is not unlike that of the forward portion of the Handley Page " Hannibal " fuselage. Although superficially the skin of the Breda 32 appears smooth in the photo graphs, it is in reality corrugated, but in a somewhat unusual manner. In place of the regular and uninterrupted corrugations with which the Junkers firm have made us familiar, the stiffness is obtained, in the Breda, by lines of interrupted corruga tions. The same principle is used in the metal skin of the wings, and the principle of it will be understood from an inspection of the sketch on page 287. Whether this form of stiffening is better than the plain corrugations used by Junkers is difficult to say. The depth of the corrugations is less, and there are considerable flats be tween the corrugations, although the small gaps between the longer are certainly rein forced by a pair of shorter " blisters." The Breda skin looks as if it would be rather easier to apply, as the amount of flattening to be done at edges should be a good deal less than in Junkers practice. The Breda 32 wing construction is parti cularly interesting to British readers just now, because it carries out in a different way the same idea as that underlying the Monospar wing design. In place of Mr. Stieger's I-section metal spar, torsionally braced by wires, the Breda single spar is a duralumin box girder, in itself fairly well strong enough to resist torsional as well as bending and shear loads, but reinforced by a metal skin. If riveting is considered a big job, the Monospar version of the single-spar construction appears the simpler. In the Breda spar there is a very large number of rivets, each member of the girder being a riveted-up box, strut or tie, and the separate boxes being riveted together. The spar DETAILS OF WING AND UNDERCARRIAGE : This photograph gives a good idea of the construction of the single spar, which is a girder built up of box-section booms and struts. The telescopic leg of the under carriage is attached to the spar, and housed inside the wing. The other lugs seen are for the support of the engine mounting. 286
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