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Aviation History
1910
1910 - 0855.PDF
OCTOBER 15, 1910. Now with regard to the " stray field." You say the leakage round the ends of the plane is lost, and the way to make that loss as small as possible is to make the chord short as compared with the span. I do not at all follow this. The leakage is caused by the disturbance in the air due to the passage of the cutting edge of the plane. This leakage is in direct proportion to the length of that edge, and has no reference whatever to the fore and aft length of the plane. To put it crudely, if a plane has a cutting edge of 30 ft., it will cause a certain amount of disturbance, and this disturbance will be just the same whether the plane is 6 ft. fore and aft or 60 ft. fore and aft. It seems to me, therefore, that the way to reduce the leakage is to reduce the disturbance, and the way to reduce the disturbance is to reduce the cutting edge of the plane. The Dunne machine owes its stability to this among other things, for its arrow-shaped edge enters the air with the minimum of effort. As to other things, there is no comparison in the advantages of the end-on aeroplane. Speed, for instance ; stability has been already mentioned ; lift, of course, remains the same product of angle and speed ; the elimination of constructional difficulties, also, would be of immense advantage, and the plane might be made much stronger and lighter. To conclude. With regard to the yacht. I am not a professional, and I speak subject to correction, but when I was at sea I always understood that it was the object of the sailor to sheet the sails home so as to get as flat a surface as possible to the wind. And I was always under the impression that the only reason why the sails were not absolutely flat was because it was impossible to get them so. 1/ycHT Manchester Street. W. LK MAITRE. [We cannot quite understand the point of view taken by our corre spondent, for although everyone is, of course, quite at liberty to hold a personal opinion on any subject, something more substantial than mere verbal argument must be advanced by anyone who seeks to refute that something that has come to be commonly accepted as so much of a physical fact as the relative efficiency of the broadside aspect as compared with the end-on aspect of an aeroplane. Our correspondent seems to confuse the issues somewhat in respect to the " Tee" test. The object of this test is to show that the broadside aeroplane has a greater lifting efficiency than an end- on aeroplane. The head and the stem of the Tee have equal areas, but the experiment always shows that the head tries to rise above the stem, thus proving that it is exerting a greater lift. The question of relative stability was not one that we were discussing in our article. Our correspondent remarks that the lift of an end-on aeroplane " remains the same product of angle and speed," but this is an absolute contradiction of fact (see Note 19 " Flight Manual "). The implied suggestion that the Dunne aeroplane flies in end-on aspect is one that we should imagine will not receive very much support from the inventor of that particular machine.—Ed.] ENGINE CONTROL. [819] Referring to this vital proposition, it would appear that in most cases no ignition timing or carburettor control is arranged for. Throttle manipulation may be useful for various slow circuit com petitions, &c, and as a safeguard when cutting off, but a carburettor which can give the best results attainable under the widely varying atmospheric conditions without the use of a hand-controlied extra- air valve, is certainly a wonderful piece of apparatus. We are not considering for the moment the question of efficiency so much as reliability, but the former alone will probably be a sufficient reason in the near future to render this extra-air device necessary. The very usual automatic extra-air valve as applied to car engines can only be expected to approach and not invariably attain the best results. As regards ignition, it is well known that the spark from a magneto is not automatically advanced in the same proportion as the engine speed, it being necessary to vary the speed under Certain conditions, particularly when flying at a great altitude. As the slight additional weight of, say, 5 lbs. apparently indicates considerable advantages, do you consider that the above modifica tions should be so often neglected ? Whitefield. OSWALD H. BROWNE and JOHN B. BUTLER. [We have little doubt that these details will settle themselves in course of time, when pilots become so expert that they feel the need of such refinements and demand their provision. But just at the moment the problem is to get engines to develop their power at all, even when allowed to go as they please, and pilots as yet have only asked that the power shall be enough for flight when the engine is working on full open throttle. Improvements in carburation and ignition are bound to come in as the art itself advances.—ED.] MODELS. "TAIL FIRST- MODEL, [820] In reference to F. N. H.'s letter (735), the model is of a monoplane type, and flies tail first. The span is 3 ft. and the length 30 ins. The main planes are of the Antoinette type, tapering, being 5 ins. in the centre and tapering off to 3 ins. at the tips. It is driven by a 9 in. propeller of my own make, and takes 8 yards of rubber made into 10 strands. The planes are set at a slight dihedral angle, and the front plane has two large ailerons. The frame is triangular, with a central stay of bamboo. The weight of the machine is 4 oz. Thames Ditton. C. RIDLEY. DURATION OF MODEL FLIGHTS. [821] Could some reader tell me how long the average model flyer will remain in the air during the course of one of its best flights, and what length ot time would probably create a record in this respect ? At model competitions, is there generally a class for machines which stay in the air for the longest time ? I should think it would bring better and quicker developments than either distance or speed competitions. Hammersmith. ]. MORSE SCOTT. PAPER MODELS. [822] I am sending under separate cover two or three of the paper models which I happen to have by me, from which you will readily judge whether you consider their style and construction likely to be of interest. Their chief points are that they are cheap, easy to make, and very efficient. The propelled model has made several flights of 100 ft. or more. PAPER MODE.L 6y G C She The glider is a plan of a rook, which I measured up last spring, and of which I have other particulars. The separate propeller is enclosed to demonstrate the construction of the bearings, which you will notice consists of paper-fastener heads, an eyelet, and a pin, all parts easily obtained. I thought it possible that some of your readers would be able to develop the ideas contained in them. Ingatestone. GEO. C. SHERRIN. SUMMARY OF OTHER CORRESPONDENCE. [823] Cambering Ribs.—A. J. C. (Prestwich), like No. 731, would be glad of information as to the best and simplest way of making a single-surface plane with correct camber. [824] H. Boulter (Kidderminster) asks what size model an 8-in. Cochrane propeller will fly. [825] Derby.—For the method of fixing wings to the framework of a monoplane see sketch of the Bleriot attachment that appeared in FLIGHT, July 31st, 1909. [826] District Model Clubs.—Arthur Rippen (5, Liverpool Road, Nunhead) would be pleased to help in forming a club for South London. 853
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