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Aviation History
1924
1924 - 0130.PDF
MARCH 6, 1924 the owner to take it with him on a passenger train. Our illus trations show the form which the solution of these problems has taken. First of all, a small paper model was made, as shown in one of our diagrams. The slotted forward area corresponds to the jib of a boat, and the triangular area at the back represents the mainsail. The model was weighted by a paper clip in the nose, and by bending down the corners of the " jib " the model could be made longitudinally stable. Turning down the starboard corner made the model turn to ihe right, and similarly an increase in the angle of the port corner resulted in a left-hand turn. Both corners turned down elevated the model, and turning them up made it dive. Thus directional and longitudinal controls were provided. For the sake of simplicity it was desired to avoid any lateral control, and the " wings " were therefore given a very large dihedral angle, which is stated to have done away with the necessity for lateral control. It is stated that the directional control was so effective that even when the model was dropped flat, i.e. without forward velocity, the rudders were effective. After the first experiments had shown that the paper model would glide, a larger model of wood and silk was made, having a span of 1 -3 m. (4 ft. 3 ins.) and a " sail area " of 0 -4 sq. m. (4 -3 sq. ft.). This model, which was first flown in November, 1922, " sailed " in a light wind, with a loading of £ lb./sq. ft., and repeatedly gained height. In order to ascertain how a larger machine was likely to behave, especially with deflection of spars and the variable " section " formed by the single- surface wing covering, a second model was built having an 13 H AT last the main regulations governing the competition for light 'plane two-seaters which is being held this summer have been drawn up, and are published in this issue of FLIGHT. Although a considerable number of subsidiary regulations are still to be decided upon, it is possible to form a fairly clear opinion of the nature of the competition. It will be seen that in the main the feature that has been aimed at is speed range. Thus this year's competition will differ materi ally from that held at Lympne last October, when economy was the keynote, with everything else subordinated to the attainment of low fuel consumption. This year, as far as the rules indicate, there is to be no restriction on fuel con sumption other than that formed incidentally by limiting the engine capacity to 1,100 c.c. Getting off and pulling up com petitions are part of the programme, it is true, but a perusal of the rules indicates that as regards obtaining marks these are of relatively small importance, and that but a fairly small number of marks can be gained by machines capable of materially reducing the distances of take-off and pulling up. * * * * THE formula to be used as a basis for the award of marks is simple enough as it stands, but certainly it must have taken a considerable amount of scheming to evolve it. As will be seen from the official rules, the basis is a percentage figure obtained by dividing into the speed-range (in miles per hour) the figure for landing speed (also expressed in m.p.h.). Thus a machine with a slow speed of 35 m.p.h. and a top speed of 75 m.p.h. has a speed range of 40 m.p.h., and the percentage figure would be 40 : 35 = 1-1425, or 114-25 per cent. A minimum of 33-33 per cent, is stipulated, and this minimum is to be subtracted from the percentage figure obtained, so that in above case the figure used for awarding marks would be 114 -25 — 33 -33 = 80 -92 per cent. * * * * FROM the fact that the basis used for the award of marks is speed range divided by slow speed, it appears that, although the formula obviously aims at a medium-speed machine, it favours the slow type rather than the fast one, since for a given speed-range the percentage figure increases with decrease in slow speed. A few numerical examples may serve to make this point quite clear. * . * * * THE medium-speed machine has already been examined in the example given above. The number of marks awarded in this case would, of course, be 80 -92 x 8 = 647 -36. Let us now take the case where the highest permissible landing speed of 45 m.p.h. is used. In order to obtain the same number of marks this machine would have to have a speed range of about 51 -4 m.p.h., giving a top speed of 96 -4 m.p.h. It is somewhat doubtful whether this speed could be attained with a machine having a power loading of round about 30 lbs./h.p. area of 14 sq. ft. There was no appreciable difference in the performance. It was then decided to build a full-size machine, and in a few days this was accomplished. e The large machine has an area of 172 sq. ft., and consists of a central skid, of steel tubing in front and of circular section wood at the rear. Two large sockets welded to the sides of the skid receive the spar roots. The spars themselves are also of circular section wood, but it is not stated whether solid or hollow section. A change will be noted in the full-sized machine compared with the paper model. By bending the central skid upwards the " jibs " are raised a considerable height above the central portion of the " mainsail." Cables run from the spar tips to the front and rear ends of the skid The wing surface is fabric, but there are no ribs of any sort. The machine was first tried over the slope of some sand dunes, being weighted by ballast and held in position by four ropes, the wind being strong enough to keep it " kiting." Pilots of various weights were then " taken up," and were able, by operating the " jibs," to keep the machine trimmed and facing the wind. The firstiree flight was made in Febru ary, 1923, and is stated to have been quite successful. When folded the machine packs into a space measuring 11 ft. by 14 ins. by 10 ins., and weighs 40 kg. (88 lbs.). It is not claimed that the machine is as efficient as the or dinary aeroplane-built monoplane gliders, but it is thought that its cheapness and simplicity will enable quite a good deal of fun being got out of it. Personally, we fail to see why the spars do not fold up, as they are very improperly braced. H H AT the other end of the scale we have the slow machine whose top speed is no more than the minimum stipulated, i.e. 60 m.p.h. Such a machine would have-to have a speed range of about 32 m.p.h. and a landing speed of 28 m.pjh. to give the same percentage figure, and thus obtain the same number of marks. While this very low landing speed would necessarily entail very light wing loading and fairly high- lift wings, it does appear that the speed-range is more easily obtained at the lower end of the scale than at the upper. Another fact rather in favour of the slower type is that a certain number of marks are to be gained by the lightly loaded machine in the taking-off and pulling-up competitions, although with one mark per yard saved these figures are not likely to be of nearly as much importance as is the speed range figure. As usual in such cases, it seems probable that the machine with the best speed-range figure will not be at either extreme of the scale permitted, but will be somewhere mid way. In other words, it does not appear to pay to load up the machine to the 45 m.p.h. slow speed, nor to keep it so lightly loaded as to get the minimum top speed of 60 m.p.h. A machine departing from both figures, but perhaps more from the faster type, seems to offer the best compromise. There is not much doubt that a very " clean " monoplane with a landing speed of round about the 35 m.p.h. should be capable of a t6p speed of 75 or 80 m.p.h., and should gain between 900 and 1,000 marks. On the other hand, it seems likely that a " clean " biplane, with lighter loading, would do almost if not quite as well nearer the lower end of the scale Thus there is reason to believe that both types will be repre sented in the forthcoming trials. At any rate, the biplane is much more even with the monplane than it was in last year's " economy " competition. * * * IT would seem that the demand for speed-range and low- landing speeds should be particularly favourable to machines fitted with slotted wings, variable camber gear, etc., and it is therefore to be hoped that both Handley Page and Fairey will be represented at this year's competitions. No mention is made in the rules of such gear being prohibited, and it is stated that brakes will be permitted, provided they are carried throughout the competitions. Presumably, therefore, cam ber gear and slotted wings are also permitted, although in a training machine they might perhaps be regarded as unneces sary complications. * * * WITH reference to the sort of machines that may be expected to be produced, a rough estimate indicates that the total loaded weight will probably be from 750 lbs. to 950 lbs., with 800 lbs. as the average figure. As wing loadings, to give the sort of landing speeds required, will probably average about 4 lbs./sq.ft., the machines may be expected to be of approxi mately 200 sq. ft. of surface, perhaps a little less in the case of 130
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