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  Partner: UNT Libraries Government Documents Department
 Collection: National Advisory Committee for Aeronautics Collection
Influence of model surface and air flow texture on resistance of aerodynamic bodies

Influence of model surface and air flow texture on resistance of aerodynamic bodies

Date: January 1, 1923
Creator: Zahm, A F
Description: This report is an analysis of two resistance equations which have particular application in the comparison of tests from different aerodynamical laboratories.
Contributing Partner: UNT Libraries Government Documents Department
Periodic stresses in gyroscopic bodies, with applications to air screws

Periodic stresses in gyroscopic bodies, with applications to air screws

Date: January 1, 1918
Creator: Zahm, A F
Description: Report discusses periodic stresses in gyroscopic bodies with applications to air screws caused by particle mass. Report concludes that all modern air screws obey the laws found for plane groups of particles. In particular the two-bladers exert on the shaft a rhythmic gyroscopic torque; the multibladers a steady one; both easily calculable for any given conditions of motion and mass distribution.
Contributing Partner: UNT Libraries Government Documents Department
Pressure of air on coming to rest from various speeds

Pressure of air on coming to rest from various speeds

Date: January 1, 1927
Creator: Zahm, A F
Description: The text gives theoretical formulas from which is computed a table for the pressure of air on coming to rest from various speeds, such as those of aircraft and propeller blades. Pressure graphs are given for speeds from 1 cm. Sec. up to those of swift projectiles.
Contributing Partner: UNT Libraries Government Documents Department
Relation of rib spacing to stress in wing planes

Relation of rib spacing to stress in wing planes

Date: May 1, 1920
Creator: Zahm, A F
Description: The stress relations to the fabric and the rib consequent upon a change of spacing between ribs in a wing plane are discussed. Considering the wing plane as a static structure, and ignoring the question of aerodynamic efficiency, it appears that the unit stress in the rib and fabric will remain constant for constant p if the linear dimensions of both rib and fabric are increased alike, viz., if wing and fabric remain geometrically similar. Since the bulge and the structural dimensions remain geometrically similar, the whole distended plane remains so, and hence should have the same pressure distribution and efficiency. If therefore the Burgess rule of making the rib spacing always one-fifth of the chord of the plane be valid, it must be valid for all others that are mechanically similar in structure and covering.
Contributing Partner: UNT Libraries Government Documents Department
The six-component wind balance

The six-component wind balance

Date: January 1, 1923
Creator: Zahm, A F
Description: Dr. Zahm's report is a description of the six-component wind-tunnel balance in use at the Aerodynamic Laboratory, Washington Navy Yard. The description of the balance gives the mechanical details and the method of operation, and is accompanied by line drawings showing the construction of the balance. The balance is of particular interest, as it allows the model to be set up quickly and accurately in roll, pitch, and yaw, without stopping the wind. It is possible to measure automatically, directly, and independently the drag, cross-wind force, and lift; also the rolling, pitching, and yawing moments. It is also possible to make the balance self-recording.
Contributing Partner: UNT Libraries Government Documents Department
Stability equations for airship hulls

Stability equations for airship hulls

Date: January 1, 1926
Creator: Zahm, A F
Description: In the text are derived simple formulae for determining, directly from the data of wind tunnel tests of a model of an airship hull, what shall be the approximate character of oscillation, in pitch or yaw, of the full-scale airship when slightly disturbed from steady forward motion. (author).
Contributing Partner: UNT Libraries Government Documents Department
Theories of flow similitude

Theories of flow similitude

Date: January 1, 1929
Creator: Zahm, A F
Description: The laws of comparison of dynamically similar fluid motions are derived by three different methods based on the same principle and yielding the same or equivalent formulas. This report outlines the three current methods of comparing dynamically similar motions, more especially of fluids, initiated respectively by Newton, Stokes (or Helmholtz), and Rayleigh. These three methods, viz., the integral, the differential, and the dimensional, are enough alike to be studied profitably together. They are treated in succession then compared. (author).
Contributing Partner: UNT Libraries Government Documents Department
The vector ruling protractor

The vector ruling protractor

Date: March 1, 1924
Creator: Zahm, A F
Description: The theory, structure and working of a vector slide rule is presented in this report. This instrument is used for determining a vector in magnitude and position when given its components and its moment about a point in their plane.
Contributing Partner: UNT Libraries Government Documents Department
A study of wing flutter

A study of wing flutter

Date: January 1, 1929
Creator: Zahm, A F & Bear, R M
Description: Part I describes vibration tests, in a wind tunnel, of simple airfoils and of the tail plane of an M0-1 airplane model; it also describes the air flow about this model. From these tests are drawn inferences as to the cause and cure of aerodynamic wing vibrations. Part II derives stability criteria for wing vibrations in pitch and roll, and gives design rules to obviate instability. Part III shows how to design spars to flex equally under a given wing loading and thereby economically minimize the twisting in pitch that permits cumulative flutter. Resonant flutter is not likely to ensue from turbulence of air flow along past wings and tail planes in usual flying conditions. To be flutterproof a wing must be void of reversible autorotation and not have its centroid far aft of its pitching axis, i. e., axis of pitching motion. Danger of flutter is minimized by so proportioning the wing's torsional resisting moment to the air pitching moment at high-speed angles that the torsional flexure is always small. (author).
Contributing Partner: UNT Libraries Government Documents Department
Airplane Stress Analysis

Airplane Stress Analysis

Date: January 1, 1918
Creator: Zahm, A F & Crook, L H
Description: Report presents stress analysis of individual components of an airplane. Normal and abnormal loads, sudden loads, simple stresses, indirect simple stresses, resultant unit stress, repetitive and equivalent stress, maximum steady load and stress are considered.
Contributing Partner: UNT Libraries Government Documents Department