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Aviation History
1910
1910 - 0151.PDF
FEBRUARY 26, 1910. FLYER EFFICIENCY. [377] ^ In calculating the efficiency of the various machines, both Mr. Evans and W. S. Flight fall into the same error of assuming that the smaller the area per lb. the more efficient the plane must be. No calculation can be of any value without taking into con sideration the wing-angle. Two machines of widely differing features as "Antoinette" and " Bleriot XI" cannot be compared without knowing the wing- angles. The one has a large area and small angle, the other small area and large angle. Both systems have much for and against. Again in Mr. Flight's table there are one or two figures given which are not taken on the same basis, and therefore the calculations are of little value. In the case of " Bleriot XI," the weight, 715 lbs., is about her full load. Now to place Antoinette and Wright on the same footing another 350 and 200 lbs. should be added respectively, also in the same speed table Bleriot's 45 was not under similar conditions to the Antoinette's 42; that the Antoinette is a much faster machine there is no doubt, and no one who has seen the two machines under the same conditions will deny. Then in calculating the area of the Bleriot, another 30 square ft. (roughly) must be added to the 150 of the main wings, as the tail plane in this type has a lifting effect. Now all this makes a vast difference to the figures given as the efficiency of the several machines, and unless care is taken to place all machines on the same basis for calculation, some very misleading results are bound to be arrived at. The reason why Bleriot comes out so well in the two tables in question is the value given to area, which alone means, practically, under this method of calculation, that two machines identical in every respect, save area—the one having a large area and small wing angle, the other a small area and large wing angle— the one having the large area would be hopelessly inefficient. G. H. HANDASYDE. |/0GHT) BENDING BAMBOO. [378] Having seen no reply to the questions asked by Miss L. E. Bland (Letter No. 263) in the issue of January 1st, I beg to submit information as follows :—In cases where small bamboo is required, and the bending not severe, " dry " heat from a " spirit" lamp or stove would answer very well for any diameters from f in. up to f in., but not for anything larger; for diameters up to ,1 in., 2 ins., or more, I should certainly use " wet " heat, or better still " steam," if possible, and even with dry heat it is a good plan to well soak the bamboo rods in very hot water before applying heat, and to keep wetting with same while bending. This is to prevent as far as possible " scorching " the fibres of the inside of bend, as if burnt they become very brittle, and would most likely crack through when left free. For rods of I in. and upwards for any bending beyond very slight curves it is better to bore holes through the middle of the "joints" if possible, continuing quite through several joints beyond the part to be bent, then carefully fill up each and every " cavity" with dry sand, tapping the part being filled repeatedly during the operation to ensure each " cavity " being quite full of the sand, but leave the very end cavity empty of sand, and pour in this one some warm water, watch till it disappears and continue to pour more water until quite sure "all the enclosed" sand is at least well damp, if quite wet all the better ; put a cork " loosely" in open end, cover over with a bit of rag or canvas, and tie round to prevent its coming off; now immerse the whole portion to be bent in hot water, boiling if possible, and test the rod while doing this, till finding it begins to bend at that part more easily than any other. This may take any length of time from half-an-hour to three hours', according to size of rod ; when ready, take from water and place over a wooden former of some kind about the proper curve required, I say about because, when cooled and dry, the bend is sure to "go back" a little, more or less, so it is better to bend to rather more curve than actually required when finished. The sand helps to retain the heat and also, what may, perhaps, be more important, it keeps the form or " section " of the bend almost, if not quite, its natural shape, and while allowing the outer fibres on top of bend to stretch, it prevents the inside fibres from buckling too severely upon each other and overlapping, the action being more compressive than " folding," besides avoiding much rupturing of these fibres in com pression. The bent part should be firmly secured to the former or curved block till quite dry, sand and all, if possible, when sand will shake out, or can be easily withdrawn by inserting a long wire, and treat as though cleaning out a tobacco pipe with a bent stem. This may seem a long " job " on paper, but is easily and quickly accomplished if attention is given to each detail, and will give very satisfactory results to the merest amateur. I shall be pleased to supplement any of above details if not found sufficiently clear to be easily followed. Newport Pagnell. HY. BATH. PAPER GLIDER. tr379l I thought this little glider might be of interest-to you. If you cut this out of stiff notepaper, and weight it with sealing wax at A it will glide eight yards or more when started just from your hand. I have tried several gliders, but I find this one much the best. If you find this one does not rise enough put the front planes level, and cut out at B and C, and bind down on the dotted line. I 6 r mm \ -X 4, £ — The shaded parts are to be turned up. I have found that the longer the wings of these are the more steadily they fly (of course you must make the wings stiff). I should be very pleased if any of your readers could explain to me whether I am right or wrong in my ideas. Granville Place, W. E. BURTON. PAPER GLIDER RECORD. [380] In answer to the question in FLIGHT of the 5th inst. as to the record flight of a paper glider, the longest I know of is a flight of nearly 90 ft. This flight was made nearly two months ago by a paper glider belonging to a certain Arthur Hope. Rugby. HIRUNDO. [381] In reply to " Sturnus " (333), I should like to give par ticulars of flights obtained by paper gliders of my own make :— Glider (bird shaped), 6 ins. length in calm 62 ft. „ ,, „ in breeze 75 ft- „ ,, ,, 3 ins. length 49 and 54 ft. My longest glide was with a strip glider which measured 14 ins. by 2 ins., weighted at the nose with a small piece of lead ; the distance travelled over level ground and thrown from the height of 6 ft. was 32 yards I ft. 9 ins. I don't know if this is a record ; if not, I should be pleased to know of one better. According to experience, I consider that anything above 6 in 1 is good gliding—that is, the glider travelling 6 ft. to every I ft. of fall. However, I have never eclipsed " Sturnus's " glide with a glider made from a sheet of notepaper. Allow me to congratulate him. Monton. AEON. [382] In reply to the question of " Sturnus " in a recent number, I have made a flight of 97 ft. with a paper glider (5 ins. across) in a still room, starting from 12 ft. above landing point. Also with a self-propelled paper model aeroplane (3^ ins. by 3J ins.) I have made a flight of 45 ft., starting from a point 7 ft. above the landing point (this is not counting any glide). Bristol. A. H. PHILLIPS. ANALYSIS OF MODERN FLYERS. [383] The following method of arriving at a figure of merit may be of interest. In any design of aeroplane, the following relation holds good between horse-power, weight and area :— W3 . W3 HP2 x = constant. A Ax HP2 According to Mr. K. H. Evans' figures, this constant for an Antoinette — 1941, for Bleriot = 1640. If the factors of safety were known to be identical in the two cases, and if the weights given were the maximum total weight which could be carried with the given HP and area, it would follow that with the same \V and HP an Antoinette monoplane could fly with ^f J-f- of the area of a Bleriot. It would then be possible by comparing the necessary weight of the two designs to see which was the better. In your issue of January 1st, Mr. Kenelm Edgcumbe rightly emphasises the importance of the minimum HP of flight, but the methods which he suggests for calculating the figure of merit are open to objection. By his first method (taking the ratio of weight lifted to propeller thrust) the figure of merit is not affected by such vital points as the overall efficiency of engine propeller and gearing («f any). His second method (measuring the cotangent of the least gliding angle)—presumably the aeroplane is flying at full speed when the glide begins—is preferable, as the effect of this efficiency is felt in the initial velocity—that is, with an efficient engine and propeller the same velocity is attained with less weight and HP. This test might, however, in practice prove to be hardly accurate enough for exact comparisons. 147
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