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Aviation History
1928
1928 - 1103.PDF
NOVEMBER 29, 1928 87 THE AIRCRAFT ENGINEER SUPPLEMENT TO FLIGHT diameter of the body, 10 m.p.h. has been deducted from thisfigure. Surface loading 8-33 lb./sq. ft. Power loading 15-38 lb./H.P. Maximum speed at ground level ... 94 m.p.h. Minimum speed 52 Rate of climb at ground level ... 600 ft.'/'min. Service ceiling, at least 10,500 ft. Absolute ceiling, at least 13,000 ft. This performance would have been considered reasonable and would have permitted the use of fields of moderate dimensions —thereibeing no club aerodromes then, of course—and together with Bert Hinkler, who was very attracted by the conception and possibilities of the scheme, it was decided to make an attempt at building a machine. The scheme fell through, however, for various reasons, the principal ones being the engine and propeller questions and to some extent a doubt as to the airworthiness in any but calm weather of such a small machine. The engine, we felt, should have had dual ignition, and this the makers could not readily fit to the standard engine. Then there was a question of a propeller for 3,000 r.p.m., which has since proved itself to be no difficulty at all. We half expected, however, that mysterious unforeseen factors might arise owing to the high rotational speed for a normal forward speed which would probably reduce the efficiency so much that our " standard " of performance would never be reached. Lastly, there was the probability that so small a machine would be perfectly hopeless in anything but a dead calm, which would have reduced the utility of the machine very seriously. Now as regards the price, I did not estimate in detail for the complete machine, as we had decided not to go on with it, but before making this decision I had completely estimated the cost of material for the wings and ailerons, and also had a quantity of data on prices of materials generally, and of items (engine, wheels, etc.) which would be purchased as units. As shown previously, the price of the material for the wings and ailerons, not including any allowance for scrap and waste, was £7 7s., which, if doubled for labour and increased in a fair proportion to cover establishment charges and scrap, gives a selling price of, sa '. £22 10s. for the wings and ailerons, or 9s. 4£d. per square foot, comparing favourably with the best prices for wings when they were being made in huge quantities during the war. The price of other components was proportionally low, owing to the very small size of the machine, and as far as I can remember we came to the conclusion that the material for the complete machine, including the engine, would have cost us somewhere between £125 and £150, inclusive of scrap. Taking the higher figure, it looks possible to produce a single seater to sell at £300 at a handsome profit if one could buy an engine for £42 less 10 per cent., and therein lies the snag. It will also be said now that two gallons is far too little fuel to carry, so that, apart from any increase in size neces- sary to provide accommodation for a more reasonable quantity, the additional weight of fuel required would put the weight of the machine up by at least 60 or 70 lb., and it would therefore be necessary to increase the span a little because the landing speed of the design as it stood was already rather too high. Subsequently, in January, 1927, the idea was further developed, this time with the " Bristol " Cherub engine as the basis. In this design, shown on the left in the set of drawings published last month, it was intended to commence with 3J gallons of fuel, the stress weight being sufficient to permit a larger quantity to be provided if necessary. The following are the estimated weights :— wt. lb. Top wings, 48-75 sq. ft 58-5 with struts. Bottom wings, 32-50 sq. ft. ... 390 „ „ Centre plane, 4-50 sq. ft. ... 6-75 Tail and elevators, 14 sq. ft. ... 17-50 Rudder and fin, 6 sq. ft. ... 7-60 wt. lb. Undercarriage 22-00 Fuselage and engine mounting ... 30-00 Petrol tank 6-50 Petrol, 3J gallons at 7 • 6 lbs. ... 24-70 Oil, \ gallon 5-00 Controls 6-50 Engine 100-00 Propeller 11-00 Tail skid 2-00 Pilot 14000 Seat and floor 3-50 Cowling 5-00 Estimated total 485-45 lb. Weight for stressing ... ... 550 1b. This design departs somewhat from the original one in that it is a biplane having fabric covered wings, external struts and wire bracing, and there are therefore a larger number of items comprising the complete aeroplane. While it is not quite as small as the original design, it is not without interest to find that a machine of practically identical wing area and dimensions generally, with a Cherub engine (the Powell biplane) was built in America, and par- ticulars published about a year ago, and one formed the opinion from the published accounts that it was considered to be a practicable flying machine in spite of its small size. There was also the Grain " Kitten " of 1916, a machine which as far as I can remember was of about 15 ft. span, and which gave very excellent results. There is evidence to show that it is practicable to build down to a size which is promising from the point of view of the £300 machine, and in my opinion it is possible so to simplify the construction as to make it feasible by sacrificing a certain amount of weight, provided that one obtains an engine of about 30 h.p. at price of say £65. As the American machine referred to above was, I believe, an amateur effort, it would be interesting, should this dis- cussion catch the eye of Professor Powell, who, I understand, is in England at the present time, to hear what he has to say about the cost of building his machine and about its air- worthiness. Another very small machine about which he may have some data is the Kreider-Reisener, which I am told was smaller still. Perhaps the Light Aeroplane Club fra- ternity may care to say something on the matter. In conclusion, the £300 single-seater does look possible if the price of the engine is right, and it is not too much, perhaps, to hope that the popularity of light aeroplanes at the present time may inspire some manufacturers to see what can be done to provide a power unit at a price low enough to make an attempt at a £300 machine worth further consideration. BUILDING THE STRUCTURE OF R.101 BY THE EDITOR Most readers of FLIGHT will probably have a fairly good idea of the general design of the new 5,000,000 cub. ft. rigid airship R.101, which is now being erected at the Royal Airship Works, Cardington, Bedfordshire. They will know that this is by far the largest airship ever built, not only in this country but in the world. They will know, from the paper read by Wing-Commander Cave-Browne-Cave before the Royal Aeronautical Society recently, that the engines are to be of the Beardmore heavy-oil type driving variable pitch propellers, and they will know, at least in a general way, that fuel and water is to be stored in tanks spread around the interior of the airship and capable of being transferred to any-desired point by powerful blowers. Of the actual structural details of R.101, however, the general public has hitherto been told relatively little, and nothing at all of the problems that arose in producing the structure once the general design had been decided upon. With other representatives of the technical press the Editor of THE AIBCRAFT ENGINEER was permitted to see at Norwich last week exactly how the various types of girder have been 1020e
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