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Aviation History
1912
1912 - 1207.PDF
DECEMBER 21, 1912. experiments with what he termed his plane dropper, ie an arrangement by which he was able to investigate (up 'to a speed of 70 m p.h.) the Ume of fall of a thin lamina pro jected horizontally m its own plane, he found that the time of fall increased rapidly with the horizontal velocity, and at a given velocity, was greatest for a plane whose width from back to front was small in comparison with the length of the ad vancing edge—a result which we should naturally expect to be the case. The well-known principle of the boomerang also depends partly on the same principle. In this case it is the initial throw and spin of the boomerang (instead of propeller thrust and elevator) which keeps it edge on to the wind, because a spinning body has a strong dislike to change the axis about which it is spinning. It returns to the sender for the simple reason that it is easier for it to do that than to do anything else—in other words it always chooses the path of least resistance. Supposing it has travelled out from the sender in the half ol an oval sweeping curve, at an angle inclined some 30° to the horizontal, and has arrived at the highest point of its flight. The force which has propelled it is used up—but it is still spinning. Gravity or the attraction of the earth, which has never ceased to act upon it, now has the upper hand and it com mences to fall. It slides down the same plane by which it went up— the path of least resistance. To go in any other direction it would have to change its plane—and this its spin prevents it from doing. The model illustrated in Fig. 1 is essentially a "flying-stick" on wheels, as such it undoubtedly was quite a successful model. Messrs. A. W. Gamage's Latest Power-Driven Model Aeroplane and Hydroplane. We give this week some very clear illustrations obtained in Messrs. Gamage's great bazaar in Holborn, of the above. It will be noticed that both are designed on strictly scientific principles, and the general workmanship and finish leave nothing to b: desired. As is clearly shown in the photographs, in the case of the model GAMAGE MONOPLANE.—Compressed air pumped in with tyre pump. A speed of 30 m,,p.b. aeroplane, the compressed air cylinder also forms the backbone or fuselage of the machine to which the wings, tails, and chassis are attached in a very neat and simple manner ; the model is of very light weight for a power-driven model, and being well-surfaced is able to fly with, comparatively speaking, a low power. The com pressed air cylinder is charged with a tyre pump, the reservoir-valve being situated in the rear. The speed of the model is stated to be 30 m.p.h. The price, £6 1 $s. complete. The model hydroplane has a ^ h.p. petrol motor. Single propeller. Its speed 14 m.p.h. The speed of the engine, 3,000 r.p.m. Propeller speed, 1,500 r.p.m. Length of hydroplane, 4 ft. It will be noticed there is a distinct joggle or step, about midway in its length, the use of such in the case of a hydroplan; pure and simple is a necessary condition for efficiency, as I have explained in FLIGHT some time ago. Now that hydro-aeroplanes have become of such primary importance, many more experiments are likely to be made with power-driven hydroplanes, and, to anyone desiring to make such, the machine illustrated would undoubtedly be of considerable value. Moreover, such a machine could easily have wings attached to it and be, at any rate, turned into a skimming air-boat, even if it did not actually fly. It would be a most interesting experiment to test what effect such an alteration had upon its speed. The price of the machine as illustrated is £ 1$. I Mr. Temperley's Query. The following reply has been received re Mr. Temper-ley's Ouery from Mr. Oswald Hamilton, Junr. :—" 1 have not yet personally built ar.o.g model, but have a deign in hand (fuselage of which is completed), and owing to other calls upon my time, have practically gone little heyond the designing stage, so my remarks will not be those based upon experiment and trial. V dealing with the questions raised, in rotation, we first have ' the ratio of lifting surface to weight.' In the design I propose to build, 1 have allowed a load of 1 oz. to 20 sq. ins. of surtace, the total weight of the model calculated to come out at 8 ozs., hence 160 sq. ins. of surface ; this Vicing proportioned as follows :—Main plane, 130 sq. ins. in area ; elevator, 50 sq. ins. in area. N.B.—I should have mentioned that this model is one of the tail-first type, " With regard to question two :—I have not actually worked out the weight of rubber in terms of the surface, i.e., effective lifting surface as not having had any flying experience with a model of this type, but with a view to an experimental comparison, I decided to lit twice as much rubber as 1 found successfully flew a hand- launched molei of the same type, and which weighed $k 01s. ; the amount of rubber used on the 5i-oz. model was one dozen yard* \ in. strip which weighs, I believe, approximately g oz., the surface of this machine is about 90 sq. ins., the extra proportion onjhe r.o.g. model allows for the overcoming ol the resistance on the ground when machine starts under its own power. Hence in my proposed model the ratio of surface to rubber is 160 sq. ins. to J or. of rublicr. " With regard to the third question, here again Mr. Ternperley's procedure in design is different from mine. I have not actually calculated the ratio of surface to thrust or pitch or diameter of propeller, hut in designing or considering the blade area, pitch and diameter of propeller or propellers to be used, 1 take into account the chord of the plane, whether this makes the whole plane possess a high aspect ratio or a low one. In the design I have introduced into this letter, the chord of the plane is 6J ins., with leading edge of plane 21 ins. in span, the trailing edge of plane is 19 ins. in span, so the model will have a low aspect ratio, hence, as it would not be logical to fit high aspect ratio propellers to a machine which is more or less designed to be a duration model, I propose fitting profilers of 9 in. diameter, width of blade in widest part l.J, ins., with a pitch at the tip of blade of 2 ft. Of course, this will not IK' the actual pitch as the propellers will be steamed from blanks cut out of satin walnut (the true pitch will be the average of the various angular measurements taken along the blade). " In reply to question four : Total weight of machine to weight of rubber, this will be in the ratio of 8 ozs. to J oz., where 8 ozs. is total weight of machine and j- oz. the total weight of rubber. "As the subject matter of the above answer is only calculations prepared for an initial experiment with r.o.g. models, I should esteem it a favour if the calculations for the proposed design are not in accordance with the main principles that underlie the designing of r.o.g. models, if any reader would point out the weak points of design." Protectors. Reply to R. R. WESTON.—A protector is a loop of wire or cane placed on the nose of a model to act as a buffer or shock absorber in event of the model hitting something or somebody while in flight. It has absolutely nothing to do with the railing or roping round of the models while on exhibition. Replies in Brief. LEONARD OPI>YKE.—We should certainly advise against the building of a monoplane glider ; procure a copy of '* How to build a 20-ft. biplane glider "(Spon and Chamberlain, New York), or consult Mr. T. W. K. Clarke. You will require an incline of about I in 4. Speed depends on surface. Commence by running against the wind on level ground, and making short jumps, then try a gentle slope, and so on. An active supporting surface of about 150 sq. ft. is sufficient to cany the weight you mention. S. CAMM.—With respect to covering in the body this is a matter which I must leave to you—personally I should 1* inclined to cover it in with, say, a light varnished silk, which showed the construction through it. I do not see why you should not make a successful r.o.g. single propeller model—using two equal gear-wheels for rubber motor. You must, however, keep your weight down. Should not use a swept-back wing unless you have had experience with them—yes, I should u e staggered planes. In reply to your last query-—I doubt it. ® ® ® ® Sparking Plugs. A MOST useful little treatise on the subject of " Sparking Plugs— their design, choice, and use," by Mr. Alec M. Lodge, has just been issued by Messrs. Lodge Bros, and Co., and a copy will be sent to any of our readers who apply to the firm at their new address at Wrentham Street, Birmingham. The book i? in no sense a catalogue, and contains a good deal of information which will probably be new to many readers.
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