Fig. 5. Perspective View of Wing Construction (Rear Spar Omitted), Showing Hollowed Entering Edge and Built-Up Spar. Rib Is of the "I" Beam Type. Courtesy "Flight."
Fig. 5. shows a typical form of wing construction (rear spar omitted). The front spar is of the "Built up type," and the trailing edge is a flattened steel tube. The rear spar is simply a solid rectangular beam. A central ash "I" beam is used as the front spar, with vertical spruce plates on either side. The spruce entering edge, or "nosing," is formed to the shape of the entering edge and is hollowed out for lightness. The rib is also of the built up type, the upper and lower flanges are of spruce and the middle portion (Web) is cotton-wood. At the point where the spar passes through the rib, the rib flanges pass over, and are tacked to the spar. The spruce nosing fits closely over the front web of the rib. The rib flanges are cut away so that the outside of the nosing will come flush with the flange line of the rib.
Fig. 6. Caudron Monoplane Wing with Steel Tube Spars and Flexible Trailing Edge. A Slot in the Rear of the Rib Web Permits the Deflection of the Trailing Edge. Drag Wire Bracing Is Used Between the Front and Rear Spars. Courtesy "Flight."
A wing of decidedly different construction is the Caudron monoplane wing shown by Fig. 6, the front and rear spars of this wing being steel tubes with an entering edge of thin wood. The drag bracing wires may be seen connected at alternate ribs by small steel plates and the latter also serve to attach the ribs to the spars. Instead of being cut out entirely, the webs of the ribs are hollowed out between the spars. Probably the most unique feature is the construction of the long flexible trailing ends of the rib at the right. The trailing rib edge is divided into an upper and lower section by a long slot, the upper sections being rigid, while the lower edge is thin and flexible. The flexible edges allow the lower ends of the ribs to give locally, and reduce the camber when struck by a heavy gust. This aids in the lateral stability, since the lift is thus considerably reduced at the point of impact, and it also relieves the wing of unnecessary stresses. The rigid upper section of the rib acts as a limit stop to the lower half, and prevents the flexure from exceeding a certain amount. Owing to the flexibility of the trailing edges a steel wire or cable must be used for the trailing edge.
Fig. 7. Standard H-3 Wing Construction. Spar, Rib and Drag Strut Connections at Left. Body Connection Fitting or Hinge at Right. Note Drag Wire Fittings. Courtesy "Aerial Age."
Details of the framing of the Standard H-3 are shown by Fig. 7. The figure at the left gives a clear idea of the connections between the drag struts and spar, while the view at the right shows the body connection at the end of the spar. I am indebted to "Aerial Age" for these sketches. The main spar is in a solid piece, channeled out to "I" beam form, except at the point where the spruce drag strut is attached. At the end of this strut is attached a sheet steel fitting that affords a means of connecting the drag wires, and for fastening the strut to the main wing spar. At the point of attachment, wooden plates are fastened to either side of the spar. These prevent the fitting bolts and the fitting from sliding along the spar when subjected to an uneven pull in the wires. A veneer top and bottom plate still further strengthen this joint and hold the sub-rib in place. The main ribs are strengthened, at the point where the spar passes through the rib web, by small vertical blocks. In the right hand figure the steel clevis is shown bolted to the spar. A lug for the wing drag wire is brought out from the fitting. The clevis on the wing engages with a similar clevis on the body of the machine, and the two are fastened together with a bolt or pin.
