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Aviation History
1918
1918 - 1285.PDF
NOVEMBER 14, igi8 V Fig. 15.—General sketch of internal bracing and fafinter-plane strut attachment on lower plane of the Berg single-seater. striking a wing will deflect the trailing portion, thus virtuallyreducing the lift, and the equilibrium of the whole machine may not, as a consequence, be disturbed to the same extentas would be the case in a machine having a rigid section. It is also possible that the reflex curvature may reduce tosome extent the travel of the centre of pressure, and so improve the longitudinal stability. As regards the efficiencyof this section we have no data available. Constructionally, the wings are built up of spruce spars ofthe box type, with ribs having spruce flanges and poplar webs. The webs are fret-sawed for lightness, and the solidportions between lightening holes are reinforced by vertical pieces of wood, riveted through the webs. The leading edgeis also of spruce, hollowed out to a U section. The trailing edge is in the form of a wire. Between the spars there is azig-zag formation of tape, passing over one rib and under the next and so on. The top plane, which is in one piece and has no dihedralangle, is supported from the body by N strute sloping outward slightly, as shown in the scale drawings published in our issueof October 24th. These struts are stream-line steel tubes, and are pin jointed so as to allow of adjustment when rigging.The fore-and-aft adjustment—which also serves to bring the wings at right angles to the centre line of the bod '—is carriedout by having portions of the diagonal struts provided with a thread-and-locknut arrangement. The lateral adjustmentis carried out in a, similar manner. The centre section struts form a letter W, as seen in front view, and the inner legs areprovided with the same form of adjustment as are the dia- gonal side struts. In the rear bay the lateral bracing is inthe form of cables, crossing above the body, since these are out of the way of the engine. By using struts in the frontbay and placing them in a W formation the difficulty of clearing the engine is overcome, and adjustment still renderedpossible. Fig. 11 shows the attachment of the front and diagonal side-struts to the top longeron. The struts haveforked ends, which fit over the vertical lugs of the base plate that rests on and is bolted to the longeron. Directly boltedto the inner part of this base plate is the foot of the strut that provides lateral bracing for the front bay. This strut isrigidly attached to the longeron, but has the thread-and- locknut adjustment at its upper end. The attachment ofthe rear side-strut is shown in Fig. 12. This is similar to the attachment of the front struts, but there is the differencecaused by the fact that in this bay the lateral bracing is in the form of cables. The manner in which this cable is attachedto the base plate is shown in the sketch. The attachment of the lower planes to the fuselage isshown in the sketches, Figs. 13 and 14. The rear spar attachment is shown in Fig. 13. To the outer base plate is welded the lug to which the spar is attachedby a forked spar box and a quick-release bolt. The rear strut of the undercarriage is alsowelded to this base plate, but to the lower horizontal part of it. Fig. 14 shows the attachment of the lowerfront spar and of the lift cables. The spar attachment is, it will be seen, very similar tothat of the rear spar. There is, however, a horizontal tube running across the fuselage,thus resisting any tension there may be on the spars, while the lift cable attachment is alsoextended some distaitce in the manner shown, so as to spread the load to other of themembers of which the bulkhead is composed. The fittings for the internal bracing of theplanes are of a very neat and simple type. The compression struts are in the form ofsteel tubes, and the drift bracing is stranded cables, while the anti-drift wires are of thesolid type. The inter-plane struts are stream- line steel tubes, forked at their ends andfitting over eyebolts passing vertically through the spars. The general arrangement of theseattachments and of the internal bracing system are indicated in Fig. 15. An analytical Fig. 16.—Analytical sketch of inter-plane strut attach- ment, lift cable attachment, internal drift bracing and compression tube In lower plane of the Berg .single- seater. 1286
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