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Aviation History
1909
1909 - 0805.PDF
DECEMBER II, 1909. TOBOGGAN GLIDERS. To the Editor of FLIGHT. SIR,—I was much interested in the account of Mr. Vaughan's glider, as I am also making an aeroplane which I mean to try as a glider first. I think the best chance of gliding will be a good fall of snow ; my machine will be fitted with skids, and I imagine one could start it like a toboggan down a slope. I also hope it will soar in a stiff breeze, and I imagine it would be much easier to hold it if the ropes were run through pulleys fastened to the ground by stakes and ropes. Detachable Frames. The biplane is made in three parts to take to pieces easily. 1 see you have an illustration of this sent by Mr. Yeatman, which would be quite unsuitable if it is meant for a full-size machine ; it would weaken the wood with those bolts, and probably the whole thing would snap off at the joint with the first strain on the machine. Main spars should be joined with 6teel clamps and screws, the latter through the flanges of steel sockets, and, if necessary, the spars can be lapped round with strong cord also. In the framework, where wire is used, this should also be bound or soldered where it crosses in centre to make a perfectly rigid framework. Airproof Calico. E. Phillips wants to know a good varnish to make calico airproof. Two-coat calico with the following mixture after it is stretched on framework : 4 per cent, gelatine and 5 cc. of 10 per cent, formalin (added when gelatine is melted), to 50 cc. This makes the calico waterproof. The formalin makes the gelatine insoluble ; probably alum would do as well. For small models ordinary butter paper coated with this is as tight as parchment on a drum, and I have a 6-ft. model covered this way, which has been out in several gales and come in without damage. Ash v. Spruce. Your correspondent " F. M." would do better if he used ash in- stead of spruce for his spars, but the best spruce is Oregon. Ash spars toft, long, \\ by I in., weigh about 5 lbs. each; and for a machine weighing about 600 lbs. ash spars of \\ by 2 in. are used. Hoping this information may be of use. Yours truly, Belfast. LILIAN E. BI.AND. [It is at all times a pleasure to us to receive such a thoroughly helpful letter as the above, and the fact that it comes from a lady not only enhances the interest which attaches to it, but shows how far-reaching is the fascination of flight. We expect much from Ireland in aviation, as in every other phase of daring sport, and we cordially wish success to our correspondent.—En.] CORD AND BAMBOO. To the Editor of FLIGHT. SIR,—I should like to help your correspondents " M. J. Carroll " and " F. M.", who write in your issue of December 4th. For the control of large kites I think he would find hollow brass rings lashed to his main cable at certain distances, say every 3 yards, through which are rove the guy ropes for controlling the angle of the kite, will obviate the twisting of the cords, at the same time keeping them together. He would do well to buy his rope stretched and the "turn" taken out of it by the ropemakers. The alternative is plaited flax line, but this is more expensive. To pierce a long bamboo from end to end, take a straight piece of metal rod the size of the hole required and, say, 4 ft. long. Drive this in the top end, and then set the pole on end and jar it on something solid, keeping the pole as upright as possible. The rod will make its way down and pierce a straight hole. Remove the rod and jar out the chips. This plan will answer for the ordinary mottled and yellow bamboos ; the tonkings must be bored out. Reverting to M. J. Carroll's query, I would advise him to beware of " clothes line," and get his cordage from a reliable yacht chandler's. Get samples of " Hambro line" and " lacing." Attach the carrying chair to the second ring—an extra strong one—on the main cable. Faithfully yours, Fawley. T. OSBORN SMITH. FARMAN DETAILS. To the Editor of FLIGHT. SIR,—I am building a model Farman biplane, scale 1 in. to 1 ft. I should feel much obliged if you would let me know the following :— 1. How the tail is attached to the outrigger. Do the spars go right to the end of the tail ? 2. With reference to the main planes : a, angle of entry ; b, angle of trail; c, camber ; d, angle of incidence. The drawings of Farman's machine are in No. 42, October 16th,pp. 641—644. Yours faithfully, Bromsgrove. H. C. CUTLER. [The outrigger spars stop short at the front transverse spars of the tail, the former being made by aluminium socket-brackets, as elsewhere throughout the machine. The tail is therefore " over- hung," but it is, of course, braced by the diagonal wires which cause it to become integral with the outrigger frame. Unfortunately, we are unable at present to give answers to the second question. —ED.] " TORQUE." To the Editor of FLIGHT. SIR,—I should be very glad of your advice on the following point. In designing a small model monoplane on the general lines of an Antoinette, what points should be borne in mind to avoid the torque produced by a single elastic-driven tractor screw ? In particular does (1) the pitch, 2) the size, (3) the speed of revolution of the screw affect matters ? Also am I right in supposing that the elastic and the screw each have a separate torque of their own on the machine ? I enclose a stamp for reply. Thanking you in advance. Yours faithfully, South Croydon. C. A. R. [Torque being essential to the transmission of power (it is merely a technical expression for the word " twist") cannot be avoided in any system in which power is transmitted by rotary motion, although its ill-effects in particular cases may be eliminated by special pre- cautions. For instance, the objection to the torque of the drive on a model flyer is that its reaction tends to cant the machine, and thus makes it follow a curved path. This effect of torque reaction can be neutralised by fitting twin propellers revolving in opposite directions. It can also be compensated for, within reason, by adjusting the wing tips of the planes so as to give a correcting effect such as will constantly steer the machine straight. This, however, is only a makeshift, and impairs the full flying capabilities of the machine. The torque of the elastic and of the propeller cannot very well be considered apart. It is the system as a whole which produces the torque, and the torque itself is only rendered evident—in fact can only exist—because of the abutments at each end of the propelling mechanism. Thus the abutment for the elastic is the frame of the flyer, while the abutment for the propeller is the air. The torque of the elastic is expended in overcoming the resistance of forcing the blades of the propeller through the air, and from Newton's law, " action and reaction are equal and opposite " it follows that what- ever torque is exerted in actually driving the screw must also be exerted as reaction in a contrary direction as a tendency to cant the flyer. But for the fact that the wings of the flyer act as huge paddles of great resistance, the machine would revolve about its axis as the result of this torque. A simple experiment may help to fix ideas on this subject. Mount two similar propellers on opposite ends of a piece of elastic, and wind up the elastic in the usual way. Arrange a little frame so that the propellers are suitably held apart with the elastic between them (see sketch). When the elastic is wound up, let go both propellers simultaneously ; they will revolve in opposite directions but at equal speeds. Again wind up the elastic and let go one propeller only; it will revolve in the Same direction as before but twice as fast. Substitute some kind of paddle for the propeller at one end of the elastic, and again let go both simultaneousry ; the paddle will revolve in the opposite direction to the propeller, but at a slower speed. If the paddle is made large enough in proportion to the propeller, it will not revolve at all, but merely cant over a little during such time as the propeller is revolving. This is the state of affairs which is reached in the case of the flying machine. ED.] 807 BOOKS ON MODEL MAKING. To the Editor of FLIOHT. SIR,—In answer to your two correspondents, "Gravity" and " Pressure," in the issue of December 4th, I recommend a very
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