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Aviation History
1910
1910 - 0050.PDF
loss as to the best way to go about it. I should esteem the favour if you or some of your readers could inform me of a good district not too far from London where suitable private workshop or garage, convenient to ground for experimental flights, could be obtained, and also which of the clubs would be most likely to be of use to a beginner. Russell Square, W.C. "ENGINEER." BLERIOT MONOPLANES. [288] As it has been stated in the Press that the sole agency for Australia for the above has been given to a certain individual, we should be much obliged if you could find room in your paper to contradict this statement. The exclusive agency for any Colony has not and will not be given to anyone. We are shipping and have shipped a good many of these machines to Australia and other British Colonies, and all applications should be sent direct to us. We may say that the whole output has been sold up to June, but it is possible to secure one or two machines for delivery in April at a premium. The training ground at Croix d'Hins, Bordeaux, is now nearly ready, arid arrangements can be made through us for free tuition, either here or at Pau, to purchasers of Bleriot machines. »"53-54. Long Acre, W.C. BLERIOT, LTD. TIMBER. [289] In reply to the letter of Mr. L. Mortelmans in your issue of the 18th December, and also to many other enquirers for light wood framing for model building, we would draw the attention of your readers to our advertisement of Special American Bentwood, which appears once a month in your advertising columns. This is specially imported by us, and machined up in our own works ; it is supplied in lengths from 2 ft. by ^ in. square, but owing to the restrictions of the postal authorities all lengths over 2 ft. have to be forwarded by rail. When we say that our works cannot make this fast enough to supply the wants of readers of FLIGHT, to say nothing of other less popular journals, we think we may fairly claim to supply " a long felt want." Varnish. In reply to Mr. Fred Collins, re varnish for planes, we use the best quality paper varnish, and find this answers admirably. It can be obtained at any good varnish dealers, is quite colourless, and if applied in a warm room on a previously sized surface will be bone dry in twenty-four hours. Wood Cutting;. We should like to tender our thanks to Mr. Henry Bath for his valuable advice on wood-cutting in the letter headed " Ash v. Spruce " in the same issue ; we think many manufacturers who are engaged in cutting wood for aeroplane making will be as grateful as we ourselves are to him for his many useful hints. Guildford. H. FENTUM PHILLIPS & Co. LOADING OF GLIDERS. [290] As a constant reader of FLIGHT I should be very much obliged if you would be so good as to answer the following queries :— 1. Is there any reason why one should not construct a glider on the monoplane principle ? With a span of 30 ft. and a chord of 6 ft. the lifting surface would be greater than that of the Bleriot machine, and the weight, I should think, might easily be made half of it, as there would be no engine, tanks, fuel, or wheels. Simplicity of construction would also be a point of superiority over the biplane. If such a machine was made do you think it would have a reasonable chance of success ? Minimum Power for Flight. 2. I have heard that there is no theoretical reason why one should not fly under power with a 5-h.p. motor weighing, say, 30 lbs. Mr. Parkes'40 ft. " jumps " would seem to bear this out. Could you inform me as to this ? W. W. SMITH. [1. A monoplane with a span of 30 ft. and a chord of 6 ft. would have an area of, say, 180 sq. ft. An average pilot weighs at least 150 lbs., so that even with a very light form of construction lor the glider itself the loading would run well over 1 lb. per sq. ft. While this value would be low for a flying machine, it is high for a glider, inasmuch as to produce the necessary supporting reaction from the air it would require a higher velocity of gliding flight than could either be conveniently obtained or would be safe to attempt. Up to the present time there are, unfortunately, no really authenticated figures based on practical work that enable such speeds to be determined in advance with any degree of nicety, but it is interest ing, at any rate, to take a glance at Lanchester's load table see FLIGHT, page 297, Vol. I) in order to get a theoretical view of the case. There it will be seen that an aspect ratio of 5, which is that JANUARY 15, 1910. of a michine with a 30 ft. span and 6 ft. chord, needs a minimum of 20 miles an hour to reach its supporting velocity under a load of about one pound per sq. ft. Those value, are, as a matter of fact, calculated for the planes themselves, end neglect the resistance of any supplementary framework and the pilot ; they further assume that the planes have been designed in accordance with the laws of minimum resistance. The actual speed required would thus be much higher. In gliding, it is necessary to acquire the greater part of the velocity by virtue of a head wind, because it is not commonly con venient to launch a machine at a speed exceeding 4 or 5 miles an hour ; the limiting velocity is therefore determined by the maximum velocity of the head wind in which it is safe to experiment. On Page 334 of FLIGHT, Vol. I, we discussed the area of gliders and suggested limitations represente I by 15 m.p.h. head wind and a 5 m.p.h. launching velocity, thereby making a total speed of 20 m.p.h. through the air. We further suggested that the loading should be about half a pound per sq. ft., and although this is- possibly unnecessarily low, we should hardly recommend preliminary experiments to be made with the loading in excess off lb. per sq. ft. until there is more evidence in favour of a higher value. 2. The minimum theoretical h.p. required for flight was dis cussed on page 335 of FLIGHT, Vol. I. Assuming a total load of 400 lbs. to be sustained at 35 m.p.h. with a thrust of 67 lbs., the actual h.p. represented by the performance is only (t\ h.p. To this must be added the losses in transmission, which would at least double the amount. It is improbable that a practical machine can at present be built to carry a pilot of average weight, which shall weigh very much less than 400 lbs., but we have always maintained that this end of the scale offers a useful and interesting field for experiment, inasmuch as it leads to the evolution of a light and handy flyer of moderate speed. Moderate speed and light weight mean a great deal to the beginner, if only on the score of reduced liability to damage when alighting on terra firma.—ED.] KITE CORDS. [291] Replying to an inquiry from M. J. Carroll, page 785, issue 49, December 4th, regarding cord for large kites, we believe that a plaited or braided cord will give the best results, for the following reasons :— It gives greater strength for a given weight of material, is very flexible, does not twist or curl upon itself, can be made in any length without knots and to any given breaking strain. We are builders of machines for the production of cords of this class, and if your correspondent cares to send his address we shall be pleased to communicate with him with a view to making experiments and giving to those interested the benefit of the experience thus gained. Nottingham. STANDARD MACHINE WORKS, LIMITED. [The sample of cord submitted to us by our correspondent is somewhat suggestive of circular lamp wick in appearance. It is very soft and should be more pleasant to handle than string. It can be twisted in either direction without unravelling.—ED.] CP. AND CG. [292] As a subscriber to your excellent paper, I should be glad if you would, through the medium of your columns, enlighten me. 1 have made a model monoplane, Antoinette type. Would like to know where centre of balance should be, if in centre of main planes or at trailing edge. Wimbledon. F. S. [Assuming that the tail does not carry load, and that the centre of pressure on the maki planes is about one-third of the chord from the leading edge, then the complete model should be in balance in the centre of a line drawn between the wing tips at this point.—ED.] f CHEAP GLIDERS.-WORKING DRAWINGS OF GLIDERS. [293] Do you know of anyone who could supply me with detail sketches of a glider which is entirely practical, and not too expensive to make ? I have already started on one, but somehow or other things are working out rather heavily. A little help as to where to procure the necessary design would be cordially appreciated. Wishing your interesting paper every success, and thanking you in anticipation. GERALD T. NEWENHAM-DEANE. Barrow-in-Furness. [If a gliding machine is successful, the operator must always be prepared to find himself some 20 ft. or 30 ft. aloft above the ground, and in that moment it will not add to his peace of mind if a thought 46
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