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Aviation History
1918
1918 - 0615.PDF
JUNE 6, 1918. Construction. Wings.—As will be seen from the scale drawings, the wings are of characteristic form. The central portion consists of a rectangular centre cell permanently attached to the fuselage. The lower wings support the engines. In this centre cell the planes are set horizontally. At each side of it the lower main planes are swept upwards with a vertical dihedral of 2.75°, the top planes being kept flat, and both main planes are swept backwards in the horizontal plane to an angle of 40 fcr the immediately tinder -the engines, whilst between them and the fuselage is fixed a strip of corrugated aluminium which acts as a footway. The fabric is attached in the usual manner, and . is stitched to the ribs both top and bottom. The two surfaces ' are stitched together behind the metal rod, which acts as a stringer, and by this means the actual trailing edge wire is relieved of a certain amount of tension. The wing structure is internally braced by means of steel tubular cross-pieces and stranded cables. A single fitting is employed for the Fig. 1.—Aerofoil section A.E.G. aeroplane. Fig. 2. bottom plane and 30 for the top plane. As, the central portion of the upper main plane has 4 ins. of negative stagger relative to the bottom plane, this difference in angle brings their tips practically vertically over cne another. The/angle pi .inci- dence attains a maximum of 40 at the base of the engine struts, i.e., 7 ft. lof ins. from the centre. At the second strut the angle is 3J0, and at the end strut 2|°. These angles are painted in circles on the surface of the planes, evidently for the convenience of riggers. The camber of both planes is washed out gradually towards the tips, and a representative section of the main planes taken at the junction of the engine bearer struts is given in Fig. 1. For purposes of reference the R.A.F. 14 section is superimposed. This figure also shows the position of the main spars, which are of steel tube. These are 50 mm. in outside diameter, but their wall thickness is not at present known. In order to allow the thinning down of the wing section, these tubes are flattened out towards the extremity of the wing. They are chamfered down to a narrow end and a fiat plate acetylene welded on to each side ; thus at the spar tip the section is roughly rectangular. The main spars are kept parallel throughout the whole of their length, and are attached to the central cell by means of pin joints, similar4» those on the Friedrichshafen. The ribs are of solid wood and are constructed as shown in Fig. 2. It is rather notable in comparison with other German machines of all types that ply wood is almost entirely absent. In the A.E.G. construction the rib webs are perforated and streng- thened by wooden uprights at intervals and are glued into a attachment of the interplane struts and for that of the bracingtubes. * This fitting is shown in Fig. 4. It is a tight fit on the spar, to which it is fixed by a bolt, and is formed with an exten-sion lug which acts, as shown, as an anchorage for thebracing tube, whilst a sideways extension of the same lug carries aneye for the bracing wire. It is provided with a cup-shaped upper extension, into which there is screwed a steel dome whichcarries the ball of the strut socket fitting and also acts as a wiring plate for the interplane bracing wires. As shown inthe sketch, the fabric is run into the space between the upper and lower flanges of this fitting, the whole making a very neatjob. Struts. These are of streamline section steel tube and of uniformdimensions throughout. The section is 92 mm. long by 48 mm. broad. The ends are sharply tapered down, and into 1l:<m Fig. 3. grooved flange. The ribs are placed 300 mm. —325 mm. apart —and are not directly or firmly attached to the spars on which they are a relatively loose fit. Passing through the ribs of the bottom plane and extending from their junction with the centre section to the extreme outside strut are two steel tubes, approximately 17 mm. in diameter, which act as housings for the aileron control wires. These tubes are very strong, and it is thought possible that they are also counted upon to lend rigidity to the wing structure. The leading edge, which is of the usual semi-circular section, acts as a distance piece, as also does the wire trailing edge. Thirteen inches in front of the last named is a stringer formed of a steel rod Apart from this, the spars are the only longitudinal members of the wings. Between the main ribs are false ribs running from the leading edge to a point a few inches behind the leading spar and applying only to the upper surface. One of these false ribs is sketched in Fig. 3. It is secured as shown in the sketch by means of a s emi-circular saddle and a wrapping of tape which passes as shown through holes in the rib. Where it meets the leading edge it is furnished with triangular packing pieces, which locate and hold it in position. The lower plane is covered as to its upper surface with sheet metal Fig. 4. Fig. 5. is welded a cupped ferrule which drops on to the ball shown in sketch Fig. 4, and is there held in position by a cotter pin. The attachment is shown complete in Fig. 5. This joint gives a considerable range of lateral freedom, as is the usual practice on machines of German design. Fuselage. The whole of the fuselage is built up of steel tubes welded together. It is of plain rectangular section, and the cross tubes are attached directly to the main bocms without the intervention of any clips. This detail of construction is shown in Fig. 6, which also illustrates the single and double lugs which are used for the purpose of securing the bracing wires. Under the nacelle and in the neighbourhood of the main petrol tanks and the bomb racks the fuselage is reinforced with thin tubular steel tie-rods. Fig. 7 shows the manner in which the upper booms of the fuselage are provided with sockets for the inclined struts of the central cell. The fitting consists of two circular steel plates welded into position to form an integral part of the frame joint, the front one of these flanges being provided with lugs for the anchorage of bracing cables. The inclined struts are secured by a ring>of short set screws 613
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