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The torsion of box beams with one side lacking

Description: The torsion of box beams of rectangular section, the edges of which are strengthened by flanges, and of which one side is lacking, is analyzed by the energy method. The torsional stresses are generally taken up by the bending of the two parallel walls, the rigidity of which is augmented by the third wall. The result was checked experimentally on duralumin and plywood boxes. The torsion recorded was 10 to 30 percent less than that given by the calculation, owing to self-stiffening.
Date: April 1, 1940
Creator: Cambilargiu, E

Transient Effects of the Wing Wake on the Horizontal Tail

Description: An investigation was made of the effect of the wing wake on the lift of the horizontal tail surfaces. In the development of expressions for this effect, the growth of wing circulation and wing wake, the time interval represented by the tail length, and the development of lift by the rail were considered. The theory has been applied to a specific case to show the magnitude of the effect to be expected. It is shown that, for motions below a certain frequency, the development of lift by the tail may be represented by a simple lag function. The lag is, however, somewhat greater than that indicated by the rail length.
Date: August 1, 1940
Creator: Jones, Robert T & Fehlner, Leo F

Variation in Velocity Profile with Change in Surface Roughness of Boundary

Description: The present report deals with the variation of a turbulent velocity profile in flow from rough to smooth wall and vice versa. Expressions obtained for the shear-stress distribution with respect to the distance from the point of junction of the different roughnesses and from the wall distance, are utilized to ascertain the developing velocity distributions. Under simplified assumptions, the use of these formulas renders possible the integration of the motion equations for the shear stress. This calculation is carried out and compared with the experiments.
Date: September 1, 1940
Creator: Jacobs, W.

The Wheat Jointworm and Its Control

Description: Revised edition. "The wheat jointworm is a very small grub which lives in stems of wheat, feeding on the juices of the plant and causing a slight swelling or distortion of the stem above the joint. The egg from which it hatches is laid in the stem by an insect resembling a small black ant with wings. This insect attacks wheat only. The injury which it causes to wheat is very distinct from that caused by the Hessian fly, yet the effects caused by these two insects are often confused by farmers." -- p. 1-2. This bulletin gives a brief outline of the life cycle and the nature of the injury to the plant by the jointworm so that any farmer may readily recognize its work and be able to apply the measures of control herein recommended.
Date: 1940
Creator: Phillips, W. J. (William Jeter), 1879-1972 & Poos, F. W.

Why potatoes run out.

Description: Describes the types of diseases attacking potatoes, how to identify them, and how to treat the plants and seed potatoes in order to prevent the spread of disease.
Date: 1940
Creator: Schultz, E. S. (Eugene S.), 1884-

Wind-tunnel investigation of an NACA 23030 airfoil with various arrangements of slotted flaps

Description: AN investigation was made of a large-chord NACA 23030 airfoil with a 40- and a 25.66 percent-chord slotted flap to determine the section aerodynamic characteristics of the airfoil affected by flap chord, slot shape, flap position, and flap deflection. The flap positions for maximum lift, the position for minimum drag at moderate and high lift coefficients, and the complete section aerodynamic characteristics of selected optimum arrangements are given. Envelope polar of various flap arrangements are included. The relative merits of slotted flaps of different chords on the NACA 23030 airfoil are discussed, and a comparison is made of each flap size with a corresponding flap size on the NACA 23021 and 23012 airfoils. The lowest profile drags at moderate lift coefficients were obtained with an easy entrance to the slot. The 25.66-percent-chord slotted flap gave lower drag than the 40-percent-chord flap for lift coefficients less than 1.8, but the 40-percent-chord flap gave considerably lower drag for lift coefficients. The drag coefficients at moderate and high lift coefficients were greater with both sizes of flap on the NACA 23030 airfoil than on either the NACA 23021 or the NACA 23012 airfoil. The maximum lift coefficient for the deflections tested with either flap was practically independent of airfoil.
Date: March 1, 1940
Creator: Recant, I G

Wind tunnel investigation of fuselage stability in yaw with various arrangements of fins

Description: An investigation was made in the 7-by-10 foot wind tunnel to determine the effects of dorsal-type fins and various arrangements of fins on the aerodynamic characteristics of a streamline circular fuselage. Comparative plots of the aerodynamic characteristics of the fuselage alone and the fuselage with various fin arrangements are given to show their effects on coefficients of yawing moment, drag, and lateral force. Results are also given for one case in which a rear fin on a circular fuselage was faired with modeling clay to obtain a fuselage shape with the same side elevation as the fuselage with the unfaired fin but with an elliptical cross section over the rearward portion of the fuselage. The results indicated that fin area to the rear of the center of gravity of the fuselage was beneficial in reducing the magnitude of the unstable yawing moments at large angles of yaw; whereas, fin area forward of the center of gravity was harmful. The dorsal-type fin was more effective for increasing the yawing stability of the fuselage than was a smoothly faired rearward portion with the same side elevation as the fuselage with the unfaired dorsal type fin. The minimum drag coefficient and the slope of the curve of yawing-moment coefficient of the fuselage at zero yaw were unaffected by the addition of the fins, within the experimental accuracy of the tests.
Date: November 1, 1940
Creator: Hoggard, H Page, Jr

Wind-Tunnel Investigation of Rectangular Air-Duct Entrances in the Leading Edge of an NACA 23018 Wing, Special Report

Description: A preliminary investigation of a number of duct entrances of rectangular shape installed in the leading edge of a wing was conducted in the NACA 20-foot tunnel to determine the external drag, the available pressure, the critical Mach numbers, and the effect on the maximum lift. The results showed that the most satisfactory entrances, which had practically no effect on the wing characteristics, had their lips approximately in the vertical plane of the leading edge of the wing. This requirement necessitated extending the lips outside the wing contour for all except the small entrances. Full dynamic pressure was found to be available over a fairly wide range of angle of attack. The critical Mach number for a small entrance was calculated to be as high as that for the plain wing but was slightly lower for the larger entrances tested.
Date: September 1, 1940
Creator: Biermann, David & McLellan, Charles H.

Wind-Tunnel Investigation of the Lift Characteristics of an NACA 27-212 Airfoil Equipped with Two Types of Flap, Special Report

Description: An investigation has been made in the NACA 7- by 10-foot wind tunnel of a large chord NACA 27-212 airfoil with a 20% chord split flap and with two arrangements of a 25.66% chord slotted flap to determine the section lift characteristics as affected by flap deflection for the split flap and as affected by flap deflection, flap position, and slot shape for the slotted flap. For the two arrangements of the slotted flap, the flap positions for maximum section lift are given. Comparable data on the NACA 23012 airfoil equipped with similar flaps are also given. On the basis of maximum section lift coefficient, the slotted flap with an easy slot entry was slightly better than either the split flap or the slotted flap with a sharp slot entry. With both types of flap the decrease in the angle of attack, for maximum section lift coefficient, with flap deflection is large for the NACA 27-212 airfoil as compared with the NACA 23012 airfoil. Also with both flaps, the maximum section lift coefficient obtained with flaps is much lower for the NACA 27-212 airfoil than for the NACA 23012 airfoil.
Date: September 1, 1940
Creator: Swanson, Robert S. & Schuldenfrei, Marvin J.

Wind-tunnel investigation of two airfoils with 25-percent-chord Gwinn and plain flaps

Description: 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.
Date: May 1, 1940
Creator: Ames, Milton B , Jr

Wind tunnel tests of an NACA 23021 airfoil equipped with a slotted extensible and a plain extensible flap

Description: An investigation has been made in the NACA 7- by 10-foot wind tunnel of a large chord NACA 23021 airfoil equipped with two arrangements of a completely extended 15 percent chord extensible flap. One of the flaps had a faired juncture, without a gap; the other was provided with a slot between the trailing edge of the airfoil and the nose of the flap. The results showed that the basic airfoil gave the lowest profile-drag coefficients over the low lift range, the airfoil with the plain extensible flap gave the lowest profile-drag coefficients over the moderate lift range, and the airfoil with the slotted extensible flap gave the lowest profile-drag coefficients over the high lift range. The airfoil with the slotted extensible flap had the same maximum lift at a flap deflection of 25 degrees as the airfoil with the plain extensible flap had at a flap deflection of 60 degrees. The results of comparisons of the airfoil pitching-moment coefficients obtained with the two types of flap are dependent upon the basis chosen for comparison. Complete aerodynamic section characteristics are presented for the various flap deflections for both flap arrangements in the completely extended portion.
Date: November 1, 1940
Creator: Swanson, Robert S & Harris, Thomas A