Model Aeroplane Notes

Auckland Star, Volume LXIII, Issue 263, 5 November 1932, Page 3 (Supplement)

Model Aeroplane Notes

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In writing these weekly notes I have always endeavoured to give my readers the. very latest and best information ; obtainable in the world of model aeronautics. ' During this period I have in - . vited my readers to send along tlveir : queries, and the response thereto has at times been so great as to make the mail ; quite a large one. Some correspondents have written in quite often, and consequently I have acquired quite a number of pen-friends, who have not only sent photographs of their model 'planes, but also photographs of themselves. All these photographs I have had mounted in a book, and I take this opportunity of thanking you all for the interest taken. The letters come mostly from country boys, and I am glad to say that they usually show that the Writers have given a good deal of thought to the subject, some of the problems submitted being real "posers." I am iucluding in my notes this week a letter from a country boy, whose blushes will be spared as I do not intend to reveal his name or address, but I feel sure that you will agree with me that lie is keen and well worthy of a little help. The letter, with answers interspersed, reads:—

Dear Propeller,—As usual I have a few questions. Q. What relation should the length of propeller bear "to the wing span of a biplane? I should think it would be more than a monoplane. A. Biplane models have not been as popular in the past as 1 would have liked to see, and the datum regarding propeller sizes is not easy to get. However, the assumption that the propeller should be larger in proportion is not altogether right, as the size of the propeller is limited mostly by the amount of torque reaction the wings will allow. This means that, as you all know, there is a tendency for the 'plane to turn over in the opposite direction to that in which the propeller is revolving. As the actual span of a biplane is smaller you cannot "get away" with too large a diameter prop. If the 'plane can be made extremely light, a slow revving propeller of nearly half the wing span could be used, but so far I have found it better to keep to just a shade over 1-3 the wing span. Q.: During the Christmas holidays we will be staying at'a good bay with high hills at the back. I want to have a shot at a fuselage seaplane which may also be used as a glider from the hills. Although I have made smaller fuselage models I have made no 'plane more than 18 inches fuselage. Do you think there would be a good. chance of success? I would make the 'plane about 25 inches long, 30 inches wing span, fuselage slightly thinner than S.M.A.E. regulations and about llin propeller. About the floats. It will have to stand more than ripples, so would you advocate two floats, or one big one with wing tip floats on long Struts, so that it preserves a fairly even keel? It seems to me that although somewhat unrealistic looking, the long float and the low wingtip ones would present less friction. I could make a good stepped V-bottomed main float which could also have wheels attached turning it into an amphibian. As the first experiment of setting the wing is hardly ever correct how would I go about fitting the float ? Also would it have to be tilted backwards to ensure its not digging under at the end of the glide? What relation should, the length of the float be to the length of the fuselage?

A. T]io "double floats are better for all-round use. Set them up at a slight angle of incidence, about sdeg is correct, to stop digging- in. The wing tip floats are.the ones to dig in, so I would avoid them. The wing span could be increased to about. 34in. On a model such as this I would fit "a pair of floats shaped like the Schneider Cup winner, about loin long 2 Jin wide and lin in depth. ■ Q. Is cedar in cigar boxes any good for props? It seems to be a strong, light and easily worked wood. A. Cedar is quite good but is in- : dined to split Balsa wood is quite the best, being about one-fifth the weight, and the hard quality is quite strong. Q. Is coloured tissue obtainable? A. As far as T "know, no coloured tissue is available suitable for model use yet. Q. What amonnt of dope would bo required to treat the fuselage of such a machine? What is the best type of brush to use.' for doping ? I enclose a plioto. of my first attempt at a scale model. It js the Avro 631 Trainer, span 18in, prop 6in, and the wing construction follows the model SES given in your notes recently. Tail is reverse cambered, double sided, and about 10 per cent larger than scale of actual machine. The fuselage has eight one-sixteenth square longerons, and took a long time to make,, as each built up former is a different shape. The chief difficulty was the attachment of the lower wingß to th& roundish fuselage. The under carriage is streamlined 1/8 by 1/16 hard balsa, is amply strong and looks well; the same may be said of the wing struts, which are "N" type. Since the photograph has been taken the struts have been coloured black, circles added and bracing wires attached to the wings, which all adds tremendously to the appearance, v It glides well, but is a bit of a job to get flying, as even with no incidence the wings have a little too much lift, even with a heavy kauri propeller to keep the weight forward. It weighs just under one ounce. lam glad to see plans of various full-sized machines in the notes. Is there any chance of the Tiger Moth or the Westland Widgeon getting in ? The lastnamed is a good simple type for scale models, which, after all, are the only real model aeroplanes. With regard to a small BJin wing span model, I have been having much fun with this type. It can be adjusted to fly in a four foot circle, and from off the table goes round and round the light like an infuriated bumble bee. A. You would require about lJoz of dope. This should be thinned down and applied with a "mop" brush. The brushes I use are about 3in long, the handle being formed of a quill and the brush end a large mop of very fine hair about 5-Bin long. This allows the dope to be spread quickly and evenly. Keep the brush in an airtight tin, with a little thinner always kept in it. This will save you a lot of expense, as these brushes will harden up and be spoilt if allowed to dry with the dope in them. To overcome your difficulty in getting the scale Avro to fly, try leaning the propeller forward; that is, alter the angle of the line of thrust. This will generally overcome difficulties . such as you describe, but it is quite usual to have to add small lead weights to the nose piece in order to bring the centre of gravity forward far enough.