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Aviation History
1915
1915 - 0461.PDF
Edited The Best Length for a Fuselage. By REV. ALFRED J. B.YRTLETT. " IN some notes written on the loth September, 1913, I drew attention to the advantages of a shonfuselagt, having experimented exhaustively in this direction, and I pointed out that the chief ad vantage is quickness of recovery in the even/ of a dive, on the analogy of a short-keeled boat, which all yachtsmen will understand. " May I now add the following observations ?:— " In nature the best gliders have the tail-plane small and close to the body, e.g., the seagull, and this is contracted to the smallest dimensions, except when required, while the tail-less butterfly, though not perhaps a true monoplane, glides to perfection, cj,, the fritillary. " This introduces a further interesting problem, viz., not the position but the function of the tail-plane. Hypothetically the best glider will be one which requires no tail-plane, except in emergency, because the drag exerted in correcting continuously the faulty tendency of the wing planes reduces speed, besides interfering with the action of the wing tips or ailerons. " Hence arises the question of the desirability of a true ' mono plane,' i.e., a glider in which the wing planes possess independent fore and aft stability. The problem itself was experimentally solved by me in years gone by, in proof of which I send you a battered tail-less paper model of a seagull, which you will find to glide per fectly ; also a butterfly, which, being heavily built, must be launched with some force. " The result is obtained by means of conflicting positive and negative surjaces. Doubtless this reduces speed somewhat, but less, I think, than the dragging tail-plane, and with the advantage of greatly increased steadiness. "Adopting this principle, I would employ in practice a con- tractible tail-plane, normally closed, but expanding and lifting when it is desired to soar, or to correct a dive or ' pancake.' " These broad observations are so far proper to the subject ol fuselage or rather tail-plane, but they open up questions of wing- formation and speed variation upon which, with your kind consent, I will give the result of my experiments later." Mr. Bartlett encloses with his communication several models of the various gliders. Generally speaking, these glide remarkably well, especially in rather gusty winds. The best one, on the whole, is, we think, the one that is herewith reproduced, Fig. I. We reproduce below the chief points in Mr. Bartlett's original notes: — " In view of Lieutenant Dunne's discoveries a description of some independent experiments and theories which led me years ago to similar discoveries may interest your readers. " I first noticed, about the year 1886, the surprising ' lift' of an umbrella held nearly parallel with the wind. This suggested ' lifting' wings with dipping front edge now so common. " Next, finding the lift excessive as my model gained speed, I greatly reduced the dip amidships, and leaving the trailing edge normal throughout, I exaggerated the dip towards the wing tips 80 as JOHNSON, to present a reversed plane which shouldpai ti.Uly .ouiitcraa th without apfeciahly checking speed. Such gliders held upside down in the palm and launched as if bowling at the wicket* will l>e found L«»«*->*«4«' tmlM>f t*t* Fig. 1.—The Rev. A. J. Bartlett's model- to travel at high speed horizontally. In a full sire machine this 1 reversed plane ' would lie increased in pitch or extent with increase of speed, as sometimes seen in birds when gliding downward against wind. (l'ig. a ) "My next discovery was the fa,iltty of steering by means of Ktich wing lips, the minutest variation of pitch producing a marked variation in direction, thug dispensing with rudder or fins. Balanced by this means my glider flew perfectly straight. But 1 lie most surprising discovery was its extreme steadiness and alneihe <>/ oscillation. I attributed this to the rigid' gripping ' of the wing between the two opposing pressures. "A tail set at an inappreciable V secured fore-and-aft stability and vertical steering. Fig. 2.—Sketch of ptgesn "gliding" against a strong wind (seen through 12 power field glass). Notice the twist in the wings becoming negative from the middle to the outer ends. " Later I varied the shape, though retaining these principles. All were steady in strong winds, and even quite unpromising shape* when carefully balanced glided admirably. " My models were shown privately to friends many years ago, more recently 1909) to a director of an aeroplane company, and ; 9ur principle, r my enlighten- later to Col. Capper, who exclaimed, ' You have got « and forthwith made a paper model of the ' Dunne 'for 1 Photo, t'y Jamei C. liatdeti. Mr J. Mills' twin-screw water biplane model, which appeared at a recent meeting of the Scottish Aeronautical Society Model Aero Club. View from In front and from behind, and. In the centre, tint getting o . Span top plane, 25 In. bv 4 ins -Span, lower plane, 20 ins. by 4 Ins.; Gap 5 Ins.; Length 33 Ins.; Propellers 7J Ins,,,13 In., pitch aoprox- Rubber brands, A m. each; Floats (front;, 6 Ins, by M Ins. by r| Ins. (rear); Total weight 7 ox».; Tall vr 11 ins. by 1\ Ins- 461
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