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.