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Aviation History
1913
1913 - 0340.PDF
[/ycHT] MARCH 22, 1913. Edited by V. E. Some Lessons from 'he Flying Tests at Hendon. VVE have received the following communication and accompanying sketches from Mr. James McBirnie. The account which Mr. McBirnie t;ivrs of his models' peiformances contains several points of especial interest [ we therefore print it in cxtemo, together with some remarks on the points raised therein. " llydre-aeroplmii. -This was not successful in actual flight— firstly because 1 made the mistake of endeavouring to obtain a long duration flight by attaching a coarse-pitched pair of propellers, necessitating a longish run before rising. This would have Mr. Desoutter's model. been successful had the water been calm—but as it was, the rough water was against it, while on the other hand a smaller diameter and a finer pitched pair of propellers would have forced the model upwards almost immediately. Kor the second and third trials I added more rubber, but the extended immersion after the first trial, besides adding considerable weight, had made the model rather sloppy and weakened the float support, so that although the model rose from the water at the .third trial, one of the main floats swung inwards causing the model to tilt over and the wind assisting . . . disaster. "A".('.(/. Biplane.—This model was quite successful in flight and remarkably stable, considering the rough wind. I find that the large span, together with the tip extension on the upper plane, assists both the lateral and longitudinal stability, respectively while the position of the elevator, 3 ins. above xhzjuselage, is a consider able advantage ; the duration of flight was not excessive, owing to the model l>eirjg heavy (10 ozs.) for the power applied. I might mention here that the rudder, although not called into use on the occasion specified, is very effective in the position underneath and slightly at the rear of the elevator. " llanii-laitiiihid Monoplane.—This was not successful, i.e., from a hand launched point of vit-w, its best performance being, I believe, 35 sees, duration. The model was 4ft. in length and weighed over 7 ocs. I was rather surprised at not getting a greater duration out of this model, and, although I added more rubber, no appreciable advantage accrued. I find that, while I can get a 90-sec. duration with a 4-ft. model weighing about 5 ozs., a 7-oz. model of the same length does not give half the result. I account for it in the inevitable sagging of the heavier skein of rubber." Commenting on the foregoing, we must first congratulate Mr. McBiruie 011 the use of the expression, " I made the mistake," the usual expression to which we are accustomed being, " I had such rotten luck, you know," &c., &c. We quite agree with our correspondent's remarks re position of tlevatoi and fine and coarse pitched propellers. Considering the time of year, the average condition of the water at the Welsh Harp and the atmospherical conditions prevalent on the day of the contest, he undoubtedly made an error of judgment in this case, and we believe we are not wrong in saying that he was not the only competitor who did so. We might also add that the type of float employed in this case requires more power to get the model off rough water than the type employed by Mr. Williams. Of course, the immersion should not JOHNSON, M.A. have weakened the float support, i.e., we should say there was some small constructional error here ; a hydro-aeroplane is a machine which should be specially designed to be waterproof in every part. In not a few cases even the flotational tests applied at Olympia clearly showed that even in such a " vital" part as the floats absolute watertightne.'s had not by any means been achieved. Referring to our correspondent's remarks on his r.o.g. biplane, " remarkably " stable is a very strong term to apply, a term which, we are afraid, we should have some hesitation in applying to any model. Generally speaking, we think aeromodellists are somewhat too prone to attach too much importance to some particular shape of wing, fin, wing extension, special form of camber, &c, &c, and too little weight to the factor which speed plays in the steadiness of flight exhibited by their models. Taking quite an unbiassed view—and calling any model having a speed in calm air of over 15 m.p.h. a quick-flying model—it is a matter of ordinary observation that in general such models do exhibit a noteworthy steadiness in flight ; many of these models differ markedly in both design and construction, but they have all one factor in common, that of speed. In making the above remarks we do not in any way question the effectiveness of the devices used in this or in any other case to secure additional steadiness or stability (the two things are not, of course, necessarily the same, although very often confused). We have a very clear recollection of the flights made by Mr. McBirnie's model, and the stability was decidedly good. It would certainly be an interesting competition for the coming season to have one for stability and slowness of flight, a model for instance with a soaring velocity of 10 miles an hour or under, which could make a good steady flight on a day like the one at Ilendon, could, we think, truly be termed a "remarkably" stable model. 5'4-. 346 REAR VIEW A model by Mr. James McBirnie.
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