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Aviation History
1914
1914 - 1084.PDF
Edited by V. E. JOHNSON, M.A. Mr. Holmari's Twin-Propeller Monoplane. OUR correspondent writes to us as follows: "lam enclosing for your inspection two " [one—the better design of the two—is repro duced—V.E.J.] "blue prints of designs which I have got out for r.o.g. machines. They are both original, and may (with limitations) be taken to represent the average type of machine flown by members of the Dover Model Aero Club. The members of the above club have for some time past been in bad repute in the model world owing to the fact that their machines seemed exceptionally heavy ; but the following fact may 1* of general interest;—The only avail able central flying ground that could be obtained was the Northfall Meadow in which M. Bleriot landed after crossing the Channel. This meadow was a good time ago abandoned by the military authorities as a shooting ground on account of the uneven contour of the ground, and the gusts and eddies which were consequently set up when there was any wind." [We should, perhaps, explain that Mr. Holman's communication is dated July 1st last.] " Bearing this fact in mind, can it be wondered that the strength of the machine needs to be well above the average ? " However, the distances and durations attained have improved somewhat of late, as the club report for the month shows. " I should be extremely pleased if readers of FLIGHT would point out any mistakes in design and give some friendly criticism on the same." Although this particular type of machine is one which finds no -favour with us either with respect to design or usefulness, it is or -has been the popular favourite for reasons which are too well known to require stating, and we shall be pleased to publish any good criticisms. Tandem Propeller Models and Concentric Spindles. So far as neatness of design is concerned, the usual type of twin propeller A frame or single stick model aeroplane has certainly but little to recommend it, more especially, perhaps, the latter. In the early days of aeronautics when no full-sized design had been standardised, incongruities, both in tull-sized and model work, may be said to be an essential feature of progress; but as progress is made, along certain lines, of course, such anomalies ought to die either a natural or an unnatural death. The chief feature of ugli ness in the single stick twin propeller model of the ordinary type is undoubtedly the rubber motors, sticking out on either side right away from the rest of the machine. The ordinary A frame, although, of course, quite sound from a mechanical point of view, must always possess a large lateral moment of inertia, and is a design to such an extent removed from full-sized work, even so far as mere appearance goes, as to deprive it of any scientific interest, at the present time ; it belongs essentially to the past. The advantage of using twin-propellers, i.e., two propellers instead of one, is—more turns of the rubber motor, longer durations, and therefore better flights. The stability problem is also simplified, since the torque, or rather the reaction of the model to the torque, of the single rubber motor is got rid of; there are also other advan tages. There is, therefore, every reason for employing more than one propeller. ?€•: RISING POSIT ION 9ortoSrrtiKb-f5i Strip rubber e-6*:>> s/«te. HOLMAN TwiN'PROPELLER MONOPLANE lentfTH v fle/?/vj£ CJQ ^lK The Holman twin-propeller model monoplane. IO84
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