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Aviation History
1913
1913 - 0415.PDF
APRIL 12, 1913. IfijGHT 1 Edited by V. E. An Attempt to Obtain a Greater Measure of Longitudinal Stability in a Model. WE have received from a correspondent (Mr. M. H. Canning), the following communication re the above, which we publish both because such types of experiments are worthy of every encourage ment, and also with a view of inviting the criticisms of our readers on the same. We might just mention, to avoid any misunderstanding, that the elevator is not fixed during any flight, but pivoted at the centre of pressure for some given angle, the idea being that whatever the attitude of the machine the elevator should remain at the same angle. The method adopted by our correspondent is to find the centre of pressure for a given angle (1 in 7, say), and then to mount the elevator on the machine by pivoting it at the centre of pressure. The centre of gravity of the elevator is also made to coincide with the centre of pressure by the addition of small weights to the leading edge of the elevator, the main idea being that if the angle between the chord of the elevator and the horizontal one is constant, no matter what the position of the machine, the result will lie a greater degree of longitudinal stability on the part of the model. " While flying one of my models I was struck by the idea that I could obtain more longitudinal stability if I could only arrange to AttW PIANt 51Dt CLtVATlQN -SMAU. BRASS TUBES - PIWO MW- mar em m<mPti" '^W^ouow *». FRAME AND jH"-. ••: ff. rfM.<f , SOLDERED ^Orr^r-^.rR^ FIOZ DIAGRAM 5H0WIN6 ATTACHMFNT OF FLLVATOR Diagrams showing the side eUvatlon and attachment of elevator. keep the elevator at a constant angle during flight, no matter what the position of the rest of the machine was in. I saw that if the front of the machine rose the main plane would have an increased angle of incidence, and as the lift of the elevator was the same, the machine would tend to resume its normal position in flight. If the front fell the main plane would have decreased lift, and would alto fall till the frame was horizontal. " To obtain an elevator which would keep a constant angle in flight, I made a small plane, and pivoted it at a point on the under side, approximately at its centre of pressure. I then placed a small weight on the front edge of the plane, so that it might balance in any position. The angle I chose for its incidence was I in 7. The method of pivoting the elevator, and the fixing of its carrier to the frame, is shown diagrammatically in Diagram 2. The model to which the elevator was fixed was a glider only, about 3 ft. long. As it was without propellers, the main plane was placed farther forward than is usual in the ordinary elevator in front type models. The model is shown in side elevation in Diagram 1. A small sliding weight of about \ oz. was placed on the frame in rear of the main plane to make minor adjustments. I had to experiment a good deal to find out the correct position of the centre of pressure of the elevator for the angle of incidence desired. A fair amount of dihedral angle was given to the main plane in order to give the model good lateral stability in order that the observation of the behaviour of the model in the air might be as easy as possible. " To see if this model had really a larger amount of longitudinal JOHNSON. MA. stability than the ordinary' tyi*. I constructed another model with exactly the same dimensions and loading, but with a fixed elevator. " Thr leM-. given were : (!) Model projected downwards at angle of 45 : 12) model projected upwards at angle of 4$"; (\,\ mi* dropped with frame vertical; (4) model Btofiyq with frame horizontal. " Tests were conducted bom 11 platform about 11 ft. high. In tests I and 2 lioth mod< K recovered, but the stability of the movable elevator one was apparent, and it covered a an greatar distance before touching the ground. In test 3 the fixed elevatoi model did not recover m time to glide. " In test 4 there was a slight advantage in favour of the movable elevator machine." The K. and MA. Association. In a recent article in the French Temps, on models and kites, the writer draws attention to ilie Kite tad Model Aeroplane Associa tion, and after giving a list of its reeords, &c, he imprcsies on the French nation the importance of eitliii rWtttiflf I GMMNJMIM H committee, or the taking up of the matter by the Aeto Hub ef France, the writer, in conclusion, holding up the English Association as a model to be copied. Now, without a doubt, an association which can meet with such appreciation boa • nation so much to the fore in aeronautical matters a* thr limili is an association which should meet with every tuppott OB the part of aeromodellists throughout this country. The rise and progress made by the association since its inauguration M February 27th, 1909, DM ba«a most rapid, and in certain respects most useful as well. During last year no less than seventeen com petitions Mr. J. H. Dollttle's Olympia model. Awarded very high marks for design and construction, but did not compete in the flying tests at Hendon. were held—fourteen for models and three for kites. But competi tions cannot be arranged and good prizes awarded without con siderable funds, and the same remark applies to the carrying on of the general work of the Association, and additional members and increased funds would at the present juncture be of inestimidile value. There is not a single aeromodellist, or anyone interested in models or aviation generally throughout the country, but could well affoid to be eith«r a Memljer, Associate Fellow, 01 Fellow, and by thus helping the only officially recognised Iwdy to deal with models and kites, he or she would 1* doing something to further the cause in which they are interested. One can scarcely over estimate the value of a strong and powerful paramount l>ody in any art or science Two things are essential for such to be the case, viz., a large membership and ample funds. Provided the first be obtained, the second generally follows as a matter of course. All ,ind each interested in model work, either as a sport or as a scientific adjunct to aeronautical matters gcne:ally, should take the earliest opportunity of joining the Association, and inducing as many as possible of their friends to do the same. Every effort (on the part of the Association) will be made to hold a great international competition during the present year. If those in this country arc either unable or unwilling to raise the necessary funds, then the French offer will undoubtedly have to be accepted and the meeting held abroad, which would no doubt not only prevent many English aeromodellists from being among the comjietitors, but would also not reflect greatly to the credit of 1 ngl.-ind, which 421
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