Description: In connection with the DVL Report 272 on the theory of the lateral stability of airplanes, the formal results are here amplified in some respects and their technical significance again briefly explained. Three numerical examples show how model tests for checking the lateral stability are to be evaluated and supplemented, if necessary, and how the stability limits depend on the design of the airplane and on the conditions of flight.

Description: This report presents towing tests made in the N.A.C.A. tank of a parent form and five variations of a flying-boat hull. The beams of two of the derived forms were made the same as that of the parent and the lengths changed by increasing and decreasing the spacing of stations. The lengths of the two others of the derived forms were made the same as that of the parent while the beams were changed by increasing and decreasing the spacing of buttocks, all other widths being changed in proportion. The remaining derived form has the same length and beam as the parent, but the lines of the forebody were altered to give a planing bottom with no longitudinal curvature forward of the step. The test data were analyzed to determine the minimum resistance and the angle at which it occurs for all speeds and loads. The results of this analysis are given in the form of non dimensional curves for each model. The effect of variation in over-all size, as indicated by a "complete" test on any given hull, is pointed out. The effect of changing length alone by the spacing of buttocks, as well as the effects of the ...

Description: Four planing surfaces, all having beams of 16 inches and lengths of 60 inches but varying in dead rise by 10 degrees increments from 0 degrees to 30 degrees, were tested in the N.A.C.A. tank. The results cover a wide range of speed, loads, and trim angles, and are applicable to a variety of problems encountered in the design of seaplanes. The data are analyzed to determine the characteristics of each surface at the trim angle giving minimum resistance for all the speed and loads tested. A planing coefficient intended to facilitate the application of the results to design work is developed and curves of resistance, wetted length, and center of pressure are plotted against this coefficient. Several examples, showing the application of the test data to specific design problems are included.

Description: Three tapered airfoils based on the N.A.C.A. 2200, the N.A.C.A.-M6, and the Clark Y sections were tested in the variable-density wind tunnel at a Reynolds Number of approximately 3,100,000. The models, which were of aspect ratio 6, had constant core center sections and rounded tips, and tapered in thickness from 18 percent at the roots to 9 percent at the tips. The aerodynamic characteristics are given by the usual dimensionless coefficients plotted for both positive and negative angles of attack and by effective profile-drag coefficients plotted against lift coefficients.

Description: The present report gives a method for computing the torsion of boxes with thin shear-resistant or simply tension-resistant walls under any torsional load, support and dimension. The final stress condition is developed from that of a principal system with unconstrained sectional warping corresponding to Bredt's formula and an additional stress condition due to constrained cross-sectional warping. This is computed by means of the deflection condition of the principal system from a statically indeterminate calculation. Conformably, the torsional rigidity of the final system is derived from that of the principal system with unconstrained sectional buckling.