This weekly technical progress letter details 100 Area activities for the week of May 28 through June 3, 1946.

Recent data show that test hole samples out from the center of a bar show greater expansion rates than do samples out from the edge of a bar. The previously noticed irregularities in expansion of test hole samples are attributed to this phenomenon. For unexplained reasons, the expansion of the graphite piles is in close agreement with the smaller expansion rates shown by test hole samples rather than with the larger rates. It is recommended that the neoprene coal on the far side of the F pile be placed before the end of the year. It is recommended that the neoprene seal on the near side of the D Pile be replaced after replacement neoprene is on hand. It is recommended that the compressed cork and about 4 inches of the cement block was in back of the Third Safety Tanks at the D Pile be removed at the time of replacement of the neoprene seal, and that the resulting gap be covered with a flexible air-impermeable membrane such as rubberized canvas. Actual measurement of the length of graphite between the gun barrels of Tube 3671-B confirms the predicted end-wise expansion of the graphite as deduced from jacking tests on …

A report describing the methods and results of a chemical copper determination. A colorimetric method was considered the most feasible. Results and further discussion are provided in the report.

"Tests have been made at high speeds to determine the drag of models, simulating propeller shanks, in the form of a circular cylinder and three airfoils, the NACA 16-025, the NACA 16-040, and the NACA 16-040 with the rear 25 percent chord cut off. All the models had a maximum thickness of 4 1/2 inches to conform with average propeller-shank dimensions and a span of 20 1/4 inches. For the tests the models were supported perpendicular to the lower surface of the wing of an XP-51 airplane (p. 277).

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Certain difficulties have been encountered in attempts to substitute a 'one-step' casting process, developed at Iowa State College, for the 'normal' process generally used for the production of extrusion billets. In the 'one-step' process molten metal is delivered from the reduction bomb to the billet mold instead of allowing the metal to solidify in the bomb with subsequent vacuum remelting of the biscuit metal before casting in the billet mold. Routine analyses had failed to establish significant differences in the composition of normal and one-step metal. The one-step billets had been extruded satisfactorily, and finished slugs were prepared and subjected to the usual canning operation. In subsequent tests however, it was found that a large percentage of the canned slugs were badly defective. An investigation was requested to determine the differences in composition or structure of the X-C and normal metal which would account for the failure of the X-C slugs. Samples of the failed slugs and of metal from various stages of both the one-step and normal processes were supplied by Madison Square Area, for comparison on the basis of analyses, microstructure, or such other tests as seemed desirable.

Tests were conducted in Langley 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 presented. Tests were made with afterbodies of two widths, two lengths, and two tapers. In the tests the depth of step and the angle of afterbody keel were held constant.(author).

"Because the results of preliminary flight tests had indicated the P-63A-1 airplane possessed insufficient directional stability, the NACA and the manufacturer (Bell Aircraft Corporation) suggested three vertical-tail modifications to remedy the deficiencies in the directional characteristics. These modifications included an enlarged vertical tail formed by adding a tip extension to the original vertical tail, a large sharp-edge ventral fin, and a small dorsal fin. The enlarged vertical tail involved only a slight increase in total vertical-tail area from 23.73 to 26.58 square feet but a relatively much larger increase in geometric aspect ratio from 1.24 to 1.73 based on height and area above the horizontal tail" (p. 1).