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Aviation History
1910
1910 - 0149.PDF
FEBRUARY 26, 1910. I^JGHTj CORRESPONDENCE. %• The name and address of the writer (not necessarily for publication) MQST in all cases accompany letters intenitd for imertion, or containing queries. Correspondents asking: questions relating; to articles which they have read in FLIGHT, would much facilitate our work of reference by giving; the number of the letter. NOTE.—Owing to the great mass of valuable and interesting corre spondence which we receive, immediate publication is impossible, but each letter will appear practically in sequence and at the earliest possible moment. AERONAUTICS FOR THE NAVY. [369] Your correspondent, Mr. Harold R. Ingersoll, questions my suggestion that dirigibles cannot be expected to go cruising with a fleet at sea, and he inquires how a gale can damage a dirigible when aloft. In saying that the first gale would mean their destruc tion, I did not wish to convey to the readers of FLIGHT that the • actual destruction would take place aloft, because I no more believe this would be the case than that the actual fall from a height can hurt anyone. It is the sudden landing, either on land or sea, in the gale that will work the destruction of the dirigible, because it must give way and drift to leeward as soon as the wind overpowers its driving power. Any attempt to tow with a rope attached to a vessel will also be futile in a gale of wind, because no aerial craft devised up to the present could face a full gale without collapsing under the strain. With regard to the suggestion that fuel could be supplied from a vessel beneath, I must observe that this could only be done in fine weather, and the first gale, entailing as it would the separation of the dirigible from its consort, and the subsequent disastrous landing of the dirigible, because it cannot remain in the air indefinitely, removes the dirigible in its present state from the sphere of practical marine navigation. With regard to your correspondent's amusing picture of the captive balloon being towed by a vessel chased by an enemy, I must say that, as an old balloonist, I fully appreciate the difficulty of such a manoeuvre. Such a "picnic" is one of your correspondent's suggestions, and not of mine. I did not think it necessary to explain that the spherical balloon used at sea would be inflated, and subsequently deflated, after taking the series of observations required, and that gas would be carried on board the vessel for some ten or twenty ascents to be made without returning to a base. I am glad of the information that the Italian and French Govern ments each have a balloon ship attached to their Navies. I was not aware of this, but it is welcome news to me, as showing that my suggestion, if not entirely novel, is approved of by two foreign Powers, and may therefore be adopted by our own Navy at a later date. Engelberg. GRIFFITH BREWER. THE ROE TRIPLANE. [370] A correspondent who signs himself " Cylinder " (348), " does not believe that the triplane can ever be designed so as to develop the extreme speeds which we may look for in the not very distant future." I am unable to agree with " Cylinder's " views. It seems perfectly obvious that the system which requires the least power must naturally be the swiftest, and up to the present the triplane holds the record for flying with little power. Given equal power, I think the biplanes and monoplanes will find a serious rival. Let us take two motor cars of equal power, but one has a badly-designed transmission, which absorbs a considerable amount of power; the other is otherwise, naturally the latter car will riln with less power than the other, and would beat it should they race. My 9-h.p. aeroplane carried over 50 lbs. per horse-power, whereas the French machines usually carry 25 lbs. per horse-power, and Santos-Dumont about 12 lbs. But horse-power is very deceptive, and one cannot get at the true results until they know exactly the cylinder capacity and speed of engine when flights are made. " Cylinder " asks for the number of revolutions that the 85 by 92 engine gives 9-h.p. It is about 1,600 r.p.m., and that is about the speed the engine used to run at. The engine I used weighed 964 lbs. without plugs, but with double ignition, Mabon _clutch, chain propeller, shafting, &c, weighed well over 150 lbs. ; the whole machine, with self aboard, weighed about 500 lbs. A. V. ROE. LONGITUDINAL STABILITY. [37i] The problem of longitudinal stability of aeroplanes is indeed puzzling. In No. 56 of FLIGHT (January 22nd, 1910) on page 55, is a description of the Wright Brothers' patent, in which they state that their machine has increased stability by reason of the small plane in front being set at a negative angle to the line of flight. On the very next page Mr. Clarke claims a certain amount of automatic stability for a machine of the same kind by having the small front plane at a greater angle than the large back one. More over, the arguments in the two cases are quite different, the Wright Brothers seeking to counteract the travel of the centre of pressure, while Mr. Cferke leaves this out of account entirely, giving two arguments for his system, one depending on the alterations of the angles of the planes to the line of flight when the machine is tilted, and the other (in the second column) showing how the line of flight itself tends to keep the same. Again, in the next issue of FLIGHT (No. 57), at the top of page 74, Messrs. Chittenden and Robinson explain how the travel of the centre of pressure alone tends to keep the machine at the proper angle to the line of flight without any supplementary surfaces at all coming into play. Analysing the various theories, it seems to me that we must first divide disturbances of longitudinal equilibrium into— (a) Alteration of the angle of the planes to the line of flight. (b) Alterations of the direction of the line of flight itself. Of course, most disturbances are combinations of (a) and (b). If the (a) kind are produced by variations of speed, the Wrights' nega tive angle will assist stability by counteracting the travel of the centre of pressure, as they show in their patent, but if speed is not altered, as Messrs. Chittenden and Robinson show, the centre of pressure will travel so as to give a righting effect, and also if the front surface has a greater angle than the back, as in the Clarke glider, a second righting effect will be produced. As for variations classes under (b), Mr. Clarke's arrangement will, by varying the speed of flight, as he shows, tend to keep the line of flight the same, such as the sideways movements produced by the dihedral angle tend to lateral stability. But then the correct construction for the machines must depend on the proportions in which the various disturbing and righting effects take place. The question is exceedingly complicated, and I should be glad if someone would clear up the problem in my mind by either agreeing with my theories or showing me where they are wrong. Trusting this letter is not too long. Wimbledon. B. BRUCE WALKER. RUBBER PRESERVATIVES. [372] I should be obliged if you would insert the following lines immediately. Several of your correspondents recommend vaseline and glycerine as lubricants and preservatives for rubber. I trust none of your readers have tried this treatment. If they have they will soon repent. I know from experience and the advice of several rubber experts that if you want to ruin rubber, glycerine, oil, and vaseline are the most deadly substances you can possibly lay hands on. Anything oily rots rubber and takes away all its elasticity. I have tried, and I know. The same gentleman who warned me against bringing my rubber into contact with oil told me that a weak solution of washing soda in water was an excellent preservative. I tried this, and am using the same rubber now that I bought in the summer. Those who have used any of the substances mentioned may very probably be able to save their rubber by bathing and thoroughly rinsing it in a warm solution of soda water. I have also used a substance called " Slypso," and sold by Messrs. Bonn. This liquid has the advantage that it does not evaporate quickly. It also seems to increase the number of turns which the elastic will stand. Regent's Park. ERIC B. PINDER DAVIS. FERGUSON MONOPLANE. [373] I am Just about to make a spare pair of wings for my machines, and I should esteem it a great favour if you will give me some advice on whether I am making them the right size for my horse-power. A comparison of my machine with Bleriot's "cross- Channel " type may be of some help to you. BLERIOT. MY MACHINE. Weight, complete, with aviator Weight, complete, with • 715 lbs. aviator 760 lbs. Lifting surface (minus tail Lifting surface ... i92sq.fi. planes) ... ... 150 sq.ft. h.p 35 h.p 25 Bore and stroke of engine Bore and stroke of engine 100 x 150, (8 cylinders) ... 85 x 95 145
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