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Aviation History
1915
1915 - 0327.PDF
MAY 7, 1915- In my own model each lever operates every 3J sees. [This is too quick lor a duration machine, every 10 sees, would be better — V.EJ.]. Of the two levers, one works the rudder and ailerom combined the microtis being inter-connected, the other lever operates the tail elevator and is so adjusted that during the time the rudder and ailerons are in operation, the elevator has a positive angle, thereby keeping nose of machine down while turning. After the rudder has operated, the elevator takes a negative angle so causing machine to climb. A certain time elapses after each set of controls have been in operation, owing to slackness of control wires, <S:c. It will be seen that with this form of control one has a large number of movements, each of which may be easily adjusted. For instance, we will suppose we use the tail elevator control only; in theory, when the elevator is at a negative angle, machine \fiMH will climb, and then as the elevator gradually assumes a positive angle, machine is then flattened out at a higher altitude, the operations then being repeated ; it would seem that machine would be more efficient than if the controls were fixed (as in the ordinary model). Again, one could see if the rudder was sufficient to preserve balance while turning, and if not, how much ailerons need to be used to preserve balance. In the way of model " stunts," I think the chute de c6te, ragtime and switch-backing, &c, would be quite possible. This kind of control would be the most efficiently used on a larger type of model (say 12 to 20 ozs.), as the gear control could be made lighter in proportion and the power used to work the same would be almost negligible. I have not as yet tested machine in free flight, but from bench tests I have every reason to think the same will be successful. The elevator, rudder and ailerons work quite smoothly, and apparently with seven strands of £ strip rubber, machine will have quite sufficient power ; of course, there is the resistance on controls during flight, and whether this will use up the power to any large extent remains to be seen. The reason I did not test machine before giving a description of OX. A 2 \Z 12 12 6 oz. : ^6 : 2-45 : 147 1 Mi : IS 8 ox. . V8 : : 2-83 1 16-98: 17 : 17 : 16 oz. 21 i>». *'i6 : "'a 1 4 1 4-S8 24 : 27'48 24 : 27i 25 » 30 J™ T. W. Bennett's arrowplane-canard, h.1. model, in full 'l8nt» the most consistent flying model of the Liverpool Aero Research Club. The model is fitted with negative tips. the same was that the tests might not have been successful, and I should not have troubled to have drawn plans, &c, that might, as in the present instance, be of use to others desiring to experiment in this direction. [We trust that later on our correspondent will lei us know the results of the free flight tests, no matter what form they may actually take, success in this direction is, after all, only a matter of experiment.] Model Research Work. We have received the following interesting communication from Mr. W. E. Evans, the Hon. Sec. of the Paddington and District Aero Club, in reply to an enquiry as to how matters were pro gressing :— " Members have been rather slow with compressed-air models ; only one has been out flying up to the present—namely, that of Mr. R. Bird. He has had seTeral flights of from 15 to 30 sees, with a 26-oz. model. Lack of rigidity in construction has inevitably ended in many smashes. " Other meml>ers including myself are intent upon research work. One of the first items is to prove which is the faster, a pusher or a tractor. Special models are being constructed for this, so that the head resistance shall not l>e altered when the change over is made. " Have you any reliable data concerning the relation of speed to loading? If not, this is another matter we shall have to take in hand. According to Stony Stratford's Club Magazine the speeds for various loadings are given as follows :— Loading (per sq. ft.)... 4 oz. 6 oz. 8 or.. 16 oz. 21 oa. Speed (m.p.h.) ... 12 15 17 35 30 " Taking the above figures to be somewhere near correct, I find the speed varies approximately as the square root of the loading. " Assuming that speed of model necessary for horizontal flight with 40H. loading to be 12 m.p.h., and that the speed varies as V loading. It works out thus : — Loading Speed as Multiplying by 6 = c which nearly agrees with .. " Hut I should think my figures are nearer the correct speeds. " I am anxious to know whether there is anything in it, because if so propellers of suitable pitch can be fitted to a model straight away knowing the loading and therefore the flying speed." Referring to the above, the figures given in the Stony Stratford Club Magazine appear to be taken from the writer's lx>ok on Model Aeroplaning, p. 132, § 14, where the following formula and figures are given:— Formula connecting the weight lifted in lbs. per square foot and the velocity. V*C The empirical formula W = - ' where W = weight lifted in lb. per sq. ft., V = velocity in ft. per sec, C — a constant 0-25 or i\>> S — 32'2 or 32 approx., may be used for a thoroughly efficient model. This gives (approx.)— 1 lb. per sq. ft. lift at 25 m.p.h. 6 oz. per sq. ft. lift at 15 m.p.h. 21 oz. ,, 30 „ I 4 oz. „ 10 ,, The 8 oz. per sq. ft. lift at 17 m.p.h. is not given in the writer's book, but is deduced at once from the formula, and is, as a matter of fact, written in in pencil in the copy before me. It must be remembered the results work out in feet per second. To convert (approx.) into miles per hour multiply by f. This formula was deduced by me mainly from experiments with Clarke's models—early wooden type—which were, in their form, most decidedly scientific and efficient models. It has frequently been confirmed since to at any rate a close degree of approximation ; it never pretended to be anything more. If the Stony Stratford Club have arrived at a similar result from independent experiment it would be a remarkable confirmation of it. The close agreement with Mr. Evans's figures is very interesting, and it would appear (unless anything be adduced to the contrary) that the conclusion is a sale one. Referring to Mr. Evans's state ment, " One of the first items is to prove which is the faster, a pusher or a tractor," we must confess we fail to see how et/ually efficient models can be built so that when the change over is effected the head resistance shall not be altered. We should certainly like some further information on this interesting point. Wireless-Controlled Models. Mr. Derek Shannon (Olinda, Rhyl) writes us as follows:—"I read your article on * Wireless-Controlled Models' with interest. I am a member of the Liverpool Wireless Association, and before the war I did a great deal of experimenting with wireless. I have also done quite as much with model aeroplanes, and I should be very pleased to co-operate in any scheme that may be put forward." 327
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