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Aviation History
1913
1913 - 0398.PDF
l/yoB? coefficient, then it is apparent that the face pressure formula must have its coefficient changed to suit the form of the object. This change in the coefficient can only be determined by experiment. It is, however, a matter of interest to find that when the resistances of long, fair-shaped bodies are studied without any attempt to divide them into separate parts, the resist ance as a whole approximates to the character of Zahm's formula, having, however, an entirely different coefficient. Thus, for example, in a series of dirigible forms tested at the N.P.L., the coefficients varied from -0000124 to •0000165, that is to say, the amount of friction calculated by Zahm's formula and coefficient would have been from 50 to 75 per cent, of the total measured resistance. Now, whichever way the problem is regarded, it is evident that each particular shape needs its own particular coefficient, and since the nature of the resistance as a whole appears to follow the frictional law for long stream line bodies, there seems to be very little point in dividing it up into two parts. Zahm's experiments, it must be remembered, were ® ® ROYAL FLYING CORPS. THE following appointment was notified in the London Gazelle of the 4th inst. :— R.F.C.—Military Wing.—Second Lieutenant Robert R. Smith- Barry is confirmed in his rank. The Admiralty announced the following appointment on the 4th inst. : Carpenter f. J, Brownridgc to the " Act;eon," additional, for training in repairing aeroplanes ; to date April 3rd. Motto for the R.F.C IN the April Army Orders it is announced that His Majesty the King has been graciously pleased to approve of the Royal Flying Corps being permitted to adopt the motto " Per Ardua ad Astra" (Through Toil to the Stars). APRIL 12, 1913. conducted on flat plates, and it is only to be expected that a flat plate should present its surface in the most advantageous manner from the standpoint of low resist ance. It does not seem necessary to identify all sorts of frictional surfaces with Zahm's cotfficient or necessarily justifiable to argue that the amount so earmarked in respect to the exposed surface of a fair-shape is a complete expression of the frictional part of the force in question. Indeed, from the fact that the whole resistance of such bodies seems to adhere closely to the frictional law, it would seem that the whole resistance is frictional by nature, although not so little in amount as if the surface were presented as a perfectly flat plate. The shapes to which the above remarks .have reference all possess a considerable fineness ratio (length to diameter), the least of the series being 4-2. In strut sections and shapes that have quite a low fineness ratio, it is not to be expected that the above should hold true, inasmuch as the ratio of the exposed surface to the projected area is so much less, and the deadwater region in the wake is, ordinarily, much more pronounced. ® ® QUESTIONS IN PARLIAMENT. ON Wednesday of last week in the House of Commons, Mr. Toynson-Hicks asked the Prime Minister whether his attention had been directed to the German army and navy estimates, in reference to their proposed increase in the preparations for aerial warfare ; and, as our existing Estimates were framed without knowledge of thete preparations, what steps he proposed to take to place Great Britain in a position adequately to defend her shores against possible attack. Mr. Asquith replied : All new facts arising after the presentation of the Estimates of the year which may affect the naval or military position are considered by the Departments concerned, and any further action which is found necessary can and will be taken without delay. The latest Henry Farman hydro-aeroplane in flight at the Monaco Meeting. 404
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