Aerodynamic force tests of an NACA 23018 airfoil with a Gwinn flap having a chord 25 percent of the overall chord and of an NACA 23015 airfoil with a plain flap having a 25-percent chord were conducted to determine the relative merits of the Gwinn and the plain flaps. The tests indicated that, based on speed-range ratios, the plain flap was more effective than the Gwinn flap. At small flap deflections, the plain flap had lower drag coefficients at lift-coefficient values less than 0.70. For lift coefficients greater than 0.70, however, the Gwinn flap at all downward flap deflections had the lower drag coefficients.

Pressure-distribution tests of an NACA 0009 airfoil with an 80-percent-chord plain flap and three plain tabs, having chord of 10, 20, and 30 percent of the flap chord, were made. Section data suitable for application to the design of horizontal and vertical tail surfaces were obtained. Resultant-pressure diagrams for the airfoil with the flap and the 20-percent-chord tab are presented. Plots are also given of increments of normal-force and hinge-moment coefficients for the airfoil, the flap, and the three tabs. A comparison of some characteristic slopes for the 30-, the 50-, and the 80-percent-chord flaps, tested in the general investigation of plain flaps for control surfaces, is included. Section aerodynamic and load data have been made available for a wide range of flap and a tab chords to be used on an NACA 0009 airfoil or on other conventional sections.

From Summary: "Pressure-distribution tests of an NACA 0009 airfoil with a 30-percent-chord plain flap and three plain tabs, having chords 10, 20, and 30 percent of the flap chord, were made. The purpose of these tests was to continue an investigation to supply structural and aerodynamic section data that may be applied to the design of horizontal and vertical tail surfaces. The results are presented as diagrams of resultant pressures and of resultant-pressure increments for the airfoil with the flap and the 20-percent-chord tab. Increments of normal-force and hinge-moment coefficients for the airfoil, the flap, and the three tabs are also given. At all unstalled flap and tab deflections, the experimental distributions agree well with those calculated by an analytical method. The agreement is poor, however, then the stalled or the unstalled condition of the flap or tab deflected alone was changed to an unstalled or stalled condition by the simultaneous deflection of both the flap and the tab."

Note presenting an investigation of three centrifugal impellers, the same except for angular blade curvature, to determine the effect of the distribution of blade loading on impeller performance. Results regarding impeller efficiency, energy addition and pressure ratio, flow characteristics, and operating range are provided.

"An analytical investigation is made of the effect of shear lag on the bending vibration of wings that are designed essentially as shallow box beams, and a procedure is outlined for incorporating this effect in the determination of bending modes and frequencies. Numerical examples show that shear-lag action in a box beam can have a large influence on its vibration characteristics. The calculations indicate that even though only a small shear-lag action may be observed in a simple static deflection test of the beam, reductions in the second and higher-mode frequencies may be relatively large" (p. 1).

"A solution based upon small-deflection theory is presented for the critical shear stress of curved rectangular panels with simply supported edges. Computed curves which cover a wide range of panel dimensions are presented; these curves are found to be in good agreement with test results. Estimated curves are also given for panels with clamped edges" (p. 1).

Report presenting the aerodynamic characteristics of 19 isolated tail surfaces, which have been determined by wind tunnel tests. Testing was also made of rectangular airfoils of various aspect ratios with and without double end plates of various shapes. The analysis indicated that the slope of the lift curve could be predicted within 10 percent for all models by use of lifting-surface-theory equations.

Report presenting tests to determine the damping in roll and aileron rolling effectiveness of three wings with different degrees of sweepback. The results showed that the values of damping in roll decreased with increasing sweepback. The rolling effectiveness of the aileron of the sweptback wing was found to be predicted with fair accuracy from static aileron-rolling-moment tests and wing-damping tests.

Note presenting an investigation of several laminated glass windshields to determine their suitability for use in airplanes with pressurized cabins. The various constructions of the extended portions of the windshields which serve for mounting purposes included plastic alone, plastic and one sheet of glass extended, plastic extension reinforced with an aluminum strip, and plastic extension reinforced with a steel strip. The results indicated that the laminated windshields with plastic-mounting extensions reinforced by aluminum or steel were resistant to creep and bursting at pressures of the order that will be encountered in service.

Note presenting a determination of friction coefficients for three constant-area vaneless diffusers, used in conjunction with a centrifugal impeller, from static- and total-pressure surveys taken at several radii and from the usual overall measurements of temperature, pressure, and air flow. The average value of the friction coefficient through the entire diffuser was approximately 50 percent higher than that for fully developed turbulent flow in smooth pipes.

Report presenting a study of a family of diffusing scrolls designed for use with a mixed-flow impeller and a small-diameter vaneless diffuser. Results regarding a comparison of performance of scrolls and comparison of performance of various compressor configurations are provided.

"By consideration of antisymmetrical, as well as symmetrical, buckling configurations, the theoretical shear buckling stresses of clamped rectangular flat plates are evaluated more correctly than in previous work. The results given, which represent the average of upper- and lower-limit solutions obtained b the Lagrangian multiplier method, are within 1 1/4 percen of true buckling stresses" (p. 1).

"New application of the Lagrangian multiplier method to stability analysis are described by means of elementary examples. The use of the method in analyzing the stability of (a) clamped plates in shear and (b) plate-stiffener combinations is demonstrated. A detailed analysis for finding upper and lower limits to critical stresses of clamped rectangular plates is presented in the appendix" (p. 1).

Note presenting an investigation to determine the stability and control characteristics of an airplane model with a skewed wing in the free-flight tunnel. Flight tests, force tests, and damping-in-roll tests were made on the model with the wing set at angles of skew from 0 to 60 degrees. The investigation was of an exploratory nature and was intended to provide only a preliminary and qualitative indication of whether such a design could be flown.

Note presenting damping data obtained from free-flight-tunnel tests of 13 models; the results are analyzed and compared with calculated results. The contributions of the wing, flaps, fuselage, tail surfaces, and power to the damping in pitch and yaw were studied. For complete models, fairly good agreement was obtained between experimental and calculated values for power-off, flaps-neutral conditions.

Note presenting an investigation of the electromagnetic-analogy method used to provide lifting-surface-theory solutions applicable to the determination of aspect-ratio corrections for the slope of the curve of hinge-moment coefficient against flap deflection. A comparison of the results of the present measurements with those of previous tests indicated that the increment of induced downwash at the 0.5-chord line over the value predicted by lifting-line theory is a linear function of the center-of-pressure coefficient.

From Introduction: "A collection balanced-aileron test data is given in reference 1. Reference 2 presents a collection of data applicable to the design of tail surfaces. The results of analyses of data for control surfaces with internal balances, plain-overhang and Frise balances, beveled trailing edges, and unshielded horn balances have already been published in references 3 to 6."

"The effects of outdoor weathering for 2 years and of an accelerated weathering test on the weight, dimensional stability, and flexural properties of selected reinforced plastics were investigated. The results of all tests, both in this report and the previous report (NACA TN No. 1240), indicate that none of the laboratory aging tests correlated with outdoor weathering with respect to all properties and all materials" (p. 1).

Report presenting the results of experiments with a technique for investigating the spray characteristics of flying-boat models. The forebody of a pointed-step flying boat hull was used for testing, and the effects of varying trim, propeller position, and amount of power were investigated. Either of the two types of spray that emanate from a forebody can limit the gross load of a flying boat depending on the configuration.

Report presenting tests conducted in tank no. 2 on models of an unconventional flying-boat hull called a planing-tail hull to determine the effects on resistance of varying a number of afterbody parameters. The effects of varying length, width, and plan-form taper of the afterbody are explored. Results regarding the effect of decreasing width of the afterbody, effect of increasing length of the afterbody, effect of tapering afterbody, and a comparison of planing-tail hulls with a conventional hull are also provided.

Note presenting an application of the iterative interference method to three problems concerning the design of cascades. The three problems considered include the determination of the shape and setting of thin blades with a prescribed type of vortex distribution, determination of the shape and setting of thin blades with certain prescribed types of pressure distributions, and determination of the blade setting for a cascade of given airfoil shape and solidity.

Report presenting an investigation of the forward-flight performance characteristics of a typical single-rotor helicopter equipped with main and tail rotors. Testing occurred over a range of tip-speed ratios and thrust coefficients. Results regarding the fuselage effects and rotor characteristics are provided.

"Concurrent tests were performed on a 1/16 and a 1/20 scale model (wing spans of 2.64 and 2.11 ft. respectively) of a modern low wing monoplane in the NACA 15 foot free-spinning wind tunnel. Results are presented in the form of charts that afford a direct comparison between the spins of the two models for a number of different conditions. Qualitatively, the same characteristic effects of control disposition, mass distribution, and dimensional modifications were indicated by both models" (p. 1).

Note presenting testing performed on scale models of a modern low-wing monoplane in the 15-foot free-spinning wind tunnel. Results are presented in the form of charts that afford a direct comparison between the spins of the two models for a number of different conditions. The results indicate that, within the range of Reynolds numbers used in the present investigation, such factors as difficulty of ballasting and testing are more important in determining proper model size than the changes in scale effect likely to result from the use of different sizes of models.