Total length of rib = 80 cm. Curve = 1 in 18. Highest point of curvature = 0.25 from front. Section of rib = 10 mm × 14 mm. at the point of attachment to mid-rib, tapering to 8 mm. × 12 mm. at the front point and to 7 mm. × 2 mm. at the tip. The rib was clamped with the tip projecting [p202] 46 cm. and was weighted at different percentages of its length to such an extent that it was deflected 11 per cent of its length, or 5 cm. The weight of the 46 cm. length of rib which projected from the clamp was 11 grammes, the whole rib weighing 22 grammes and balancing on a knife edge placed at the point where it was clamped. Point of Absolute Weight in Deflection application weight terms of in terms of weight in greatest of in terms of grammes. weight. length. length. 0.39 7680 1.0 0.11 0.445 5980 0.78 0.11 0.56 3680 0.48 0.11 0.75 2300 0.30 0.11 0.95 1100 0.143 0.11 1.00 930 0.121 0.11 A lighter rib than the above, which was constructed at the same time, was also tested with the results shown in the following table. This rib was also 80 cm. long, but was only one-half the linear dimensions in section of the rib previously tested. The rear portion of it projected 46 cm. from the clamp. The total weight of the rib was 11 grammes, or 5.5 grammes for the 46 cm. on which the measurements were made. Point of Absolute Weight in Deflection application weight in terms of in terms of weight grammes. greatest of in terms of weight. length. length. 0.39 1400 1.0 0.11 0.445 1100 0.785 0.11 0.56 700 0.50 0.11 0.75 400 0.275 0.11 0.95 250 0.178 0.11 1.00 220 0.157 0.11 A still lighter rib of the same length, weighing 9 grammes, suitable for use in the wings of the quarter-size model, was constructed and a set of tests was made on it with the following results. As in the above test, 46 cm. of the rear portion of it projected from the clamp which held it. Point of Absolute Weight in Deflection application weight in terms of in terms of weight grammes. greatest of in terms of weight. length. length.