From this sanding test it was seen that the cross-ribs must be materially stiffer, and a new set was accordingly made one-sixteenth of an inch larger in diameter at the various points of measurement. Upon giving the wing, equipped with these larger ribs, a sanding test it was found that, while there had been some improvement, it was entirely too flimsy, even when it been double-guyed by running a second wire on each cross-rib from the middle of the portion in front of the mid-rib to the middle of the portion behind the mid-rib. As the weight of the wing with these larger solid cross-ribs had now increased to more than 33 pounds, and the wing had proved itself altogether too weak for use on the aerodrome, it was evident that some other plan of constructing the ribs which would give greater strength for the same weight must be found. At first sight it might appear that the obvious way of increasing the stiffness of the cross-ribs was to employ a cross-section other than a round one, since material added to the depth of the rib is very much more effective than if added to the width. It must, however, be remembered that these cross-ribs were 11 feet long, and that, as the main mid-rib was 6 feet in front of the rear tips of the cross-ribs, with no intermediate bracing, except the light threads by which the cloth cover was attached, it was inevitable that, should the depth be made materially greater than the width, the rib would buckle sideways. Test ribs of I-beam form, which are later described, were constructed, but, although they proved exceedingly stiff, had to be discarded. In view of these facts the obvious remedy appeared to be to make the rib hollow, and one cross-rib, 3/4 of an inch in diameter at the point where it crossed the main rib, tapering to 5/8 of an inch at the front and 3/8 of an inch at the rear tip, was accordingly constructed. Tests showed that this form of rib, which was about 10 grammes lighter than the 1/2-inch solid ribs, was much stiffer than anything yet constructed. But when a wing, with cross-ribs of this size placed 20 inches apart, was sanded it was found that, although a great advance in construction had been made, still further improvement was necessary before a suitable wing for the large aerodrome could be procured. [p197]