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Aviation History
1912
1912 - 0204.PDF
f/jiGHT MARCH 2, 1912. Conducted by V. We'ght of Model and Length or Duration of Flight. Twin v. Single Propeller. Referring to our remarks re the above in January 6th issue—we have received interesting communications from Mr. G. Haddon Wood (Hon. Sec. Birmingham Aero Club), and others. Mr. Wood mentions amongst other items, that Mr. G. Mason (a club member), with a 15-oz. model, constructed about last April, of 4 ft. span and 6 ft. in length, fitted with a single propeller, Obtained (lights of 90 seconds and over 500 yards ; also that Mr. E. E. Noble won the championship of the Midlands in September, 1910, with a duration flight of 48 sees., this machine also had a single screw ; and that Mr. E. Trykle's model, which holds the club duration record with a flight of 92 sees, [we thought it was 95], has a span of 30 ins., and a 4 ft. motor rod, single propeller, and a total weight of 5 02. Longest flight not known exactly, but estimated at about 900 yards. These items with respect to performances made by single screw models are of especial interest and can only cause one to wonder why this type of model is not still more in evidence. So far as the weight of the model and the duration, &c, of the flight are con cerned the bulk of the evidence to hand (which we much regret pressure on our space forbids us to allude to more in detail) all goes to show that large rubber-driven models can be built to compete quite successfully against smaller machines. Theoretically, it can be shown that if the type be kept the same the distance is a constant quantity, and so far as actual practical construction goes, the advantage lies with the larger model, for it is always easier to build more accurately on a large scale than on a small one, the larger machine will also be less disturbed by wind irregularities, owing, for one thing, to its greater apeed. Sunshine and Duration of Flights. Mr. L. Roche (Chairman, Ealing and District Aero Club) writes calling attention to the above. He says : " On Saturday, January 27th—the sun having been shining the whole morning—in the after noon my models flew well at high altitudes (estimated 90 to 100 ft.), the flight invariably ending in a long glide. On Sunday, 28th, sky cloudy, no sun at all, and a slight mist, the same model, with exactly the same rubber as on the previous day, would not rise to more than about 30 ft., the speed was increased, and it was im possible to obtain a vol plane ; in fact, the model landed with the rubber still slightly wound. On both occasions the temperature was below freezing point, and there was practically no wind. I have also noticed that my best flights have been obtained on those hot and sunny days experienced last summer." We should much like to hear from other correspondents their experiences relative to the above. Temperature and Rubber. Generally speaking heat causes bodies to expand—but water is an exception—so is bismuth and so also is rubber. When Professor William Thomson was made aware of this fact he suggested that stretched rubber might shorten on being heated. The test was applied by Mr. Joule and the shortening found to take place. The singular experiment is fully described and illustrated in Professor Tyndall's Heat, a mode of motion, pp. 88-89. The amount in con traction is considerable but not actually stated. Will some reader carry out a series of careful and accurate experi ments on this matter, and also re the effect of temperature on rubber lubricants. The results could not fail to be both interesting and valuable. It is this kind of work that is wanted in model aero- planing, and it is also experiments of this nature which will be the ones to endure. Official Records. In order to prevent any misapprehensions which might arise, it may be as well to state that although the distances are actually measured out to feet and even inches, the unit of distance is the yard, and in the actual published record no part or parts of a yard are stated. Messrs. Mann and Grimmer, writing to us with respect to the above, state that Mr. Grimmer's machine (second duration flight) struck a cycle belonging to a bystander, and was considerably damaged in consequence, with the result that Mr. Grimmer was placed at a considerable disadvantage. We had no idea that such a thing occurred, nor was the matter reported to the observers, the JOHNSON, M.A. crowd made it very difficult to see what actually did happen just in the immediate vicinity. Scale Models. The following is part of a communication received from Mr. Ernest A. Vessey on a very important subject—the remainder will appear in next week's issue :— "When investigating the laws of aeronautics by the aid of models it is now, thanks to Mr. W. Lanchester, a well-known rule that such models must be strictly to scale, not only as regards size, but also as regards weight; i.e., for every linear scale there is a corresponding weight scale which must be rigidly adhered to, if the behaviour of the model in free flight is to resemble in any manner that of the full-sized machine it represents. Expressed in symbols if W = the weight of the full-sized machine, w = the weight of the model, lx = a linear dimension on the full-sized machine, l2 = the linear dimension of the same part on the model, then W -(if- /, If we put 3 = the scale in terms of full size = L, say, . . . (1). full size, its weight, w, then . W - L3 or w = WL Thus, if the model is to be made, say, W must equal W(T]B)3 = . 1000 When applying this law in practice there does not appear to be any serious difficulty in proportioning the various members of the framework, SO that their weight is in correct relation to the weight of corresponding members in the full-sized machines—all that is required is to make them strictly to scale, and of the same material as is to be employed in the full-sized counterparts. When dealing with the fabric covering the planes, a difficulty at once arises, thus. /Jfl B ifc* Ik 4 « m$* ^ i A m ^H B. mi ,* J "^^5 • ^'' - t/t^H HK • A 1W' ' •• "*WB fl ^B ^&WKr w^^ Some of the gold, silver, and bronze medals won by the Bragg-Smitb biplane, A fine example of what can be accomplished by a model as opposed to a flying stick. 204
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