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Aviation History
1911
1911 - 1067.PDF
DECEMBER Q, 1911. [/GCHT Conducted by V. E. Theory and Practice. " It has been found thai many model makers fly their machines without the slightest idea of the reason of the flight and this condition the club intends to do their level best to remedy." * An excellent decision, on which the Liverpool Model Aero Club deserve congratulations. Also, note on the same page, with respect to the Conisborough and District Aeroplane Society, that theoretical tests have already been established. I trust that every other club which has not yet adopted this plan will do so forthwith. No better method could possibly be adopted to build up a science of model aeroplaning. Most assuredly no first-class certificate should be awarded for practical results alone. This supposes, of course, that such results could be obtained by such means, which we much doubt. The theoretical means employed might be indirect ones, founded on the work of others, and copied or tmbodied in the design because they were found to give better results in practice. The resulting model might differ in certain respects from its prototype, but would certainly not be original, using the word in the sense intended in my former article. The greatest advances in any art have always been made when theory and practice go hand in hand. In the early achievements of any art, practice always outstrips theory, for until you have, by practice, acquired certain data, you can have no theory. Sound theory is the accumulation of observations and experiments, i.e., of practice until general principles can be deduced, and some new theory be evolved therefrom : and then this new theory becomes the rule and guidance of future practice. It is for this very reason, because the theories of the ancient were not so founded, that when the dawn of modern science broke upon the world, they fell. Theorising upon insufficient data— '' Falls like an inverted cone, Wanting its proper base to stand upon.'" Which is the reason why as data multiply, theories change. The evidence on which the laws of motion are accepted is the absolute agreement with observed phenomena of calculations, based on the assumption of their truth. Probably no law of nature stands on a firmer basis than the conservation of energy, because there is no principle towards the overthrow of which so much ingenuity has been fruitlessly directed, viz., in the search for " perpetual motion " —that something for nothing, which nature will never give us. If there is a failure in the application of a principle, then there is either some practical error in the application or some flaw in the principle itself, and a design essentially incapable of proving good in practice, cannot with propriety be said to be good in theory. To say that a thing is good in theory, but bad in practice, is a clear logical fallacy—moreover, it is not true. > There was once a very practical man who decided to build a house—he determined to be his own architect; he knew nothing of the theory of architecture, he said it only wanted common sense, the house was founded, tne walls erected, the floors laid one after * FLIGHT, Dec. 2nd, 1911, p. 1046. JOHNSON, M.A. the other, the windows inserted and the roof completed, the house was finished, and had but this single defect, that to get from the lower floor to the upper there was no staircase. Lifts were not then invented (for this is a very old story, but it illustrates my point). There are always the two, theory and practice, you cannot have sound theory without practice or the best practice without reliable theory; such being the case let us cultivate both. I propose, then, to take each week some specific case and dealing with it, briefly, and in as plain and simple language as possible. My subject next week will be "The Respective Areas of Main Plane and Elevator." I have before me several articles on " How to Build a Mode Aeroplane " (of quite the ordinary type). Before writing on any subject (no matter what its nature) it is advisable to make oneself familiar with what has already been done in the e g.4*v5MMf Model aeroplane, by £. Brayshaw, weighing 7 ounces. subject—both in magazine and book form. Much disappoint ment is sure to be averted. Please remember that it is one thing to build a successful model, but quite another thing to write about it in such a manner that anyone else (novices included) can do the same thing. For instance, one of my correspondents does not think it necessary to state a single dimension, and I never knew anyone yet who could measure Mr. C. Ian Russell's model. Note the excellent position of the rudder; but the span is excessive. 1075
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