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  Partner: UNT Libraries Government Documents Department
 Serial/Series Title: NACA Special Report
 Collection: Technical Report Archive and Image Library
The Effect of Surface Irregularities on Wing Drag. II - Lap Joints, 2, Lap Joints

The Effect of Surface Irregularities on Wing Drag. II - Lap Joints, 2, Lap Joints

Date: February 1, 1938
Creator: Hood, Manley J.
Description: Tests have been made in the NACA 8-foot high-speed wind tunnel of the drag caused by four types of lap joint. The tests were made on an airfoil of NACA 23012 section and 5-foot chord and covered in a range of speeds from 80 to 500 miles per hour and lift coefficients from 0 to 0.30. The increases in profile drag caused by representative arrangements of laps varied from 4 to 9%. When there were protruding rivet heads on the surface, the addition of laps increased the drag only slightly. Laps on the forward part of a wing increased the drag considerably more than those farther back.
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The Effect of Surface Irregularities on Wing Drag. IV - Manufacturing Irregularities, 5, Manufacturing Irregularities

The Effect of Surface Irregularities on Wing Drag. IV - Manufacturing Irregularities, 5, Manufacturing Irregularities

Date: February 1, 1938
Creator: Robinson, Russell G.
Description: Tests were made in the NACA 8-foot high speed wind tunnel of a metal-covered, riveted, 'service' wing of average workmanship to determine the aerodynamic effects of the manufacturing irregularities incident to shop fabrication. The wing was of 5-foot chord and of NACA 23012 section and was tested in the low-lift range at speeds from 90 to 450 miles per hour corresponding to Reynolds numbers from 4,000,000 to 18,000,000. At a cruising condition the drag of the service wing was 46% higher than the drag of a smooth airfoil, whereas the drag of an accurately constructed airfoil having the same arrangement of 3/32-inch brazier-head rivets and lap joints showed a 29% increase. The difference, or 17% of the smooth-wing drag, is apparently the drag caused by the manufacturing irregularities: sheet waviness, departures from true profile, and imperfect laps. the service wing, for one condition at least, showed a drag increase due to compressibility at a lower air speed than did the more accurate airfoil.
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Correction of Profile-Drag Results from Variable-Density Tunnel and the Effect on the Choice of Wing-Section Thickness

Correction of Profile-Drag Results from Variable-Density Tunnel and the Effect on the Choice of Wing-Section Thickness

Date: March 1, 1938
Creator: Jacobs, Eastman N.
Description: Profile-drag coefficients published from tests in the N.A.C.A. variable-density tunnel (Technical Reports Nos. 460, 537, 586, and 610, references 1 to 4) have tended to appear high as compared with results from the N.A.C.A. full-scale tunnel (Technical Report No. 530, reference 5) and from foreign sources (references 6 to 8). Such discrepancies were considered in Technical Report No. 586, and corrections for turbulence and tip effects were derived that tended to reduce the profile-drag coefficients, particularly for the thicker airfoils. The corrected profile-drag coefficients, designated by the lower-case symbol cdo as contrasted with the older CDO, have been employed in the airfoil reports published since Technical Report No. 460, but even these corrected results continued to appear high, particularly for the thicker sections. The important practical result is that a smaller increase of drag with airfoil thickness is indicated, which may be of primary importance to the airplane designer in choosing the optimum airfoil sections for actual wings. Further investigations of this subject were, of course, undertaken, one of the most important being an investigation of three symmetrical sections N.A.C A. 0009, 0012, and 0018 under conditions of low turbulence in the full-scale tunnel. Preliminary results from this investigation also ...
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Preliminary Full-Scale Wind-Tunnel Investigation of Wing Ducts for Radiators, Special Report

Preliminary Full-Scale Wind-Tunnel Investigation of Wing Ducts for Radiators, Special Report

Date: March 1, 1938
Creator: Silverstein, Abe
Description: Wing ducts for liquid-cooled engine radiators have been investigated in the N.A.C.A. full-scale wind tunnel on a large model airplane. The tests were made to determine the relative merits of several types of duct and radiator installations for an airplane of a particular design. In the test program the principal duct dimensions were systematically varied, and the results are therefore somewhat applicable to the general problems of wing duct design, although they should be considered as preliminary and only indicative of the inherent possibilities.
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The Torsional and Bending Deflection of Full-Scale Duralumin Propeller Blades under Normal Operating Conditions, Special Report

The Torsional and Bending Deflection of Full-Scale Duralumin Propeller Blades under Normal Operating Conditions, Special Report

Date: March 1, 1938
Creator: Hartman, Edwin P.
Description: The torsional deflection of the blades of three full-scale duralumin propellers operating under various loading conditions was measured by a light-beam method. Angular bending deflections were also obtained as an incidental part of the study. The deflection measurements showed that the usual present-day type of propeller blades twisted but a negligible amount under ordinary flight conditions. A maximum deflection of about 1/10th of a degree was found at V/nD of 0.3 and a smaller deflection at higher values of V/nD for the station at 0.70 radius. These deflections are much smaller than would be expected from earlier tests, but the light-beam method is considered to be much more accurate than the direct-reading transit method used in the previous tests.
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Investigation in the 7-By-10 Foot Wind Tunnel of Ducts for Cooling Radiators Within an Airplane Wing, Special Report

Investigation in the 7-By-10 Foot Wind Tunnel of Ducts for Cooling Radiators Within an Airplane Wing, Special Report

Date: July 1, 1938
Creator: Harris, Thomas A.
Description: An investigation was made in the NACA 7- by 10-foot wind tunnel of a large-chord wing model with a duct to house a simulated radiator suitable for a liquid-cooled engine. The duct was expanded to reduce the radiator losses, and the installation of the duct and radiator was made entirely within the wing to reduce form and interference drag. The tests were made using a two-dimensional flow set-up with a full-span duct and radiator. Section aerodynamic characteristics of the basic airfoil are given and also curves showing the characteristics of the various duct-radiator combinations. An expression for efficiency, the primary criterion of merit of any duct, and the effect of the several design parameters of the duct-radiator arrangement are discussed. The problem of throttling is considered and a discussion of the power required for cooling is included. It was found that radiators could be mounted in the wing and efficiently pass enough air for cooling with duct outlets located at any point from 0.25c to 0.70c from the wing leading edge on the upper surface. The duct-inlet position was found to be critical and, for maximum efficiency, had to be at the stagnation point of the airfoil and to change ...
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Full-Scale Wind-Tunnel Investigation of Wing Cooling Ducts, Special Report

Full-Scale Wind-Tunnel Investigation of Wing Cooling Ducts, Special Report

Date: October 1, 1938
Creator: Nickle, F. R.
Description: The systematic investigation of wing cooling ducts at the NACA laboratory has been continued with tests in the full-scale wind tunnel on ducts of finite span. These results extend the previous investigation on section characteristics of ducts to higher Reynolds numbers and indicate the losses due to the duct ends. The data include comparisons between ducts completely within the ring and the conventional underslung ducts. Methods of flow regulation were studied and data were obtained for a wide range of internal duct resistance. The results show satisfactory correlation between the finite span and the previously measured section characteristics obtained with full-span ducts. The effects of the various design parameters on the duct characteristics are discussed. The cooling power required for the internal duct installation is shown to be only a small percentage of the engine power.
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Wind-Tunnel Investigation of Air Inlet and Outlet Openings for Aircraft, Special Report

Wind-Tunnel Investigation of Air Inlet and Outlet Openings for Aircraft, Special Report

Date: October 1, 1938
Creator: Rogallo, Francis M.
Description: An investigation was made in the NACA 5-foot vertical wind tunnel of a large variety of duct inlets and outlets to obtain information relative to their design for the cooling or the ventilation systems on aircraft. Most of the tests were of openings in a flat plate but, in order to determine the best locations and the effects of interference, a few tests were made of openings in an airfoil. The best inlet location for a system not including a blower was found to be at the forward stagnation point; for one including a blower, the best location was found to be in the region of lowest total head, probably in the boundary layer near the trailing edge. Design recommendations are given, and it is shown that correct design demands a knowledge of the external flow and of the internal requirements in addition to that obtained from the results of the wind tunnel tests.
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Wind-Tunnel Investigation of an N.A.C.A. 23012 Airfoil with a Slotted Flap and Three Types of Auxiliary Flap

Wind-Tunnel Investigation of an N.A.C.A. 23012 Airfoil with a Slotted Flap and Three Types of Auxiliary Flap

Date: December 1, 1938
Creator: Wenzinger, Carl J. & Gauvain, Wiliam E.
Description: An investigation was made in the N.A.C.A. 7- by 10- foot wind tunnel to determine the aerodynamic section characteristics of an N. A. C. A. 23012 airfoil with a single main slotted flap equipped successively with auxiliary flaps of the plain, split, and slotted types. A test installation mas used in which an airfoil of 7-foot span was mounted vertically between the upper and the lower sides of the closed test section so that two-dimensional flow was approximated. On the basis of maximum lift coefficient, low drag at moderate and high lift coefficients, and high drag at high lift coefficients, the optimum combination of the arrangements was found to be the double slotted flap . All the auxiliary flaps tested, however, increased the magnitudes of the pitching moments over those of the main slotted flap alone.
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Interference of Tail Surfaces and Wing and Fuselage from Tests of 17 Combinations in the N.A.C.A. Variable-Density Tunnel

Interference of Tail Surfaces and Wing and Fuselage from Tests of 17 Combinations in the N.A.C.A. Variable-Density Tunnel

Date: January 1, 1939
Creator: Sherman, Albert
Description: An investigation of the interference associated with tail surfaces added to wing-fuselage combinations was included in the interference program in progress in the NACA variable-density tunnel. The results indicate that, in aerodynamically clean combinations, the increment to the high-speed drag can be estimated from section characteristics within useful limits of accuracy. The interference appears mainly as effects on the downwash angel and as losses in the tail. An interference burble, which markedly increases the glide-path angle and the stability in pitch before the actual stall, may be considered a means of obtaining satisfactory stalling characteristics for a complete combination.
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