Another solution is to use a solid web, lightly channelled out, as in [Fig. 33].
In some wing structures the ribs are uniform throughout, a strut of either steel tube or wood being inserted and to which the internal wiring is attached. This latter method is possibly more desirable, that is, if the joint between the compression strut and spar can be combined with the interstrut fitting. This may necessitate a little extra work in the latter, but this is preferable to the use of a separate fitting, involving additional piercing of the spar.
Importance of Even Contour.
Whilst on the subject of rib building, one cannot over emphasize the desirability of even contour, and the template, illustrated by [Fig. 34], serves as an admirable check. It is cut from very dry material to the outside curve of the section, and if this is tried on as each rib is fixed, one may be sure of comparative uniformity. The root rib is generally of stouter construction, and usually follows the same lines as the compression ribs. At this point the pull of the fabric has to be contended with, which is not infrequently a considerable strain. The same conditions prevail at the wing tip, which is one reason against excessive reduction of material at this point. Instances occur where the tension of the fabric after doping has considerably deformed the tip curve, which is at least unsightly, and may entail reconstruction.
SHAPED TO UNDER SURFACE
Fig. 34.—Template for testing rib contours.
Wing Tip Details.
The actual shape of the wing tip varies with the make of machine, and forms one of the distinctive features of the complete assembly. There is a general tendency to rake the ends, making the back spar longer than the front, on the score that increased efficiency due to reduction of end losses is attained. While this is somewhat problematic, seeing that several notable machines have square tips, and some actually constructed with the longest edge leading, it undoubtedly imparts a pleasing and distinctive appearance.
The actual construction is largely a matter for individual preference, as there are several ways of forming it. For instance, a single piece of ash may be bent to shape, or it may be cut out in sections from spruce boards and glued together with a long splice, while in another instance oval steel tube is the material. This small section steel tubing seems admirably suited for such items as wing tips, trailing edges, and the various components of the empennage, such as the fixed stabilizer, elevators, fin, and rudder.