"A total of 183 panel specimens of 24ST aluminum alloy with nominal thickness of 0.020, and 0.040 inch with extruded bulb-angle sections of 12 shapes spaced 4 and 5 inches as stiffeners were tested to obtain the buckling stress and the amplitude of the maximum wave when buckled. Bulb angles from 3 to 27 1/2 inches long were tested as pin-end columns. The experimental data are presented as stress-strain and column curves and in tabular form" (p. 1).

"The magnitude, the direction, and the fluctuations of tow forces exerted upon gliders by towing them aloft behind an automobile were measured under a variety of conditions covering a range from gentle to severe types of operation. For these tests, the glider towing force did not exceed 1.6 of the gross weight of the glider. V-G records obtained during the towed-flight period as well as during the subsequent return glide to earth showed accelerations in the range from 3 to -1 g. The results of preliminary airplane tow tests are also presented" (p. 1).

A new method of studying the flow of the water along the bottom of a model of a flying-boat hull is described. In this method, the model is fitted with a transparent bottom and is divided down the center line by a bulkhead. The flow is observed and photographed through one-half of the model by means of the diffused illumination from a battery of lamps contained in the other half of the model. Photographs of the flow, particularly of the changes that occur when the step ventilates, are shown. The results of the present investigation indicate that the method has considerable promise, chiefly in connection with motion-picture studies.

"The vortex theory as presented by the author in earlier papers has been extended to permit the solution of the following problems: (1) the investigation of the relation between thrusts and torque distribution and energy loss as given by the induction of helical vortex sheets and by the parasite drag; (2) the checking of the theorem of Betz of the rigidly behaving helical vortex sheet of minimum induced energy loss; (3) the extension of the theory of the screw propeller of minimum energy loss for the inclusion of parasite-drag distribution along the blades" (p. 1).

The problem of determining values of structural damping for use in flutter calculations is discussed. The concept of equivalent viscous damping is reviewed and its relation to the structural damping coefficient g introduced in NACA Technical Report No. 685 is shown. The theory of normal modes is reviewed and a number of methods are described for separating the motions associated with different modes. Equations are developed for use in evaluating the damping parameters from experimental data. Experimental results of measurements of damping in several flutter models are presented.