FlightGlobal.com
Home
Premium
Archive
Video
Images
Forum
Atlas
Blogs
Jobs
Shop
RSS
Email Newsletters
You are in:
Home
Aviation History
1909
1909 - 0695.PDF
OCTOBER 30, 1909. THE DIHEDRAL ANGLE. To the Editor of FLIGHT. SIR,—In a recent article on the Antoinette monoplane appearing in your issue of October 23rd, the writer, in speaking of the auto- matic stability arising from the dihedral angle of the wings on these machines, bases his explanation of the stabilising effect solely upon the righting couple produced by the alteration in magnitude of the vertical components, P^of the resultant pressure, P, as the machine heels. The effect of the horizontal component, P2, which is increased as the machine heels, is totally disregarded in the article. If the effects of both forces, P! and P2, be considered, and the hypothesis, assumed by the writer, that the pressure, P, remains constant so long as the velocity of the machine through the air is unaltered, be taken as correct, it will be seen that there is no resultant righting moment, and therefore no stabilising effect pro- duced. For, referring to the figure, the sum of the moments due to P, and P2> about the axis, O, is equal to the moment of their resultant, P, about the same axis. This applies for both wings, and, therefore, whatever the angle of heel, the moment due to the whole pressure, P, on the one side, is always counterbalanced by an equal and opposing moment, due to the pressure on the other side of the machine.c No doubt in practice there is an automatic stability resulting from the use of the dihedral angle, since such firms as the Antoinette Co. adopt the principle, but if this is the case the article in question •certainly failed to explain it. Yours truly, Forest Hill. L. C. KKMP. To the Editor of FLIGHT. SIR,—I have taken your admirable paper now for some months, and have read with interest your series of articles on successful types •of aeroplanes. In your last issue, of October 23rd, while describing the Antoinette monoplane, you enter into an analysis of the action of the dihedral T ' Lateral Force X - Lateral rslatiue wind mkicK restores equilibrium iP - Resultant Pressure wtH righting movement about CQ. angle as a means of automatic stability. This analysis is surely dncorrect, for a moment's glance at your second figure will show that there is no resultant moment tending to right the machine. A more plausible explanation seems to me to be as follows :— In whatever position (laterally) the machine is moving in still air, the resultant pressure is W (the weight) upwards in a direction bisecting the dihedral angle. This and W (the weight), vertically downwards through the centre of gravity, have in a tilted position a resultant small force, F, in the direction of the lower wing. The effect of F is to move the machine laterally downwards. The resulting lateral wind on the lower wing tends to raise it (the wing) to its normal position. May I enclose a diagram to make myself clearer ? Trusting I have not trespassed on your space, 1 am, yours truly, Birmingham. MAURICE OLLEY. [In the above note Mr. Kemp looks upon the problem of the dihedral angle as analogous to that of a bell-crank-lever pivoted upon a fixed point, O. For such a case it is true that there is no restoring couple, but in a flying machine the point, O, is not fixed ; on the contrary, it is one of the forces acting, being by hypothesis the position of the centre of gravity. The restoring couple is formed by gravity acting about some point representing the centre of pressure on the lower wing. The centre of gravity moves laterally, as pointed out by Mr. Olley, but the restoration of equilibrium is effected by an accompanying descent of the centre of gravity through space.—ED.]. • METAL VERSUS WOODEN PROPELLERS. To the Editor of FLIGHT. SIR,—While quite agreeing with Mr. Rogers as to the superiority of metallic (all steel) propellers over wooden ones, I must take exception to his claim that any propeller other than the " Hollands" is " infinitely superior lo any on the market that have yet been tried." I also object to Mr. Cochrane's assertion that his propeller "will stand a greater breaking strain and give a greater thrust than any other propeller on the market." Now, as I know by repeated complete tests what the " Hollands " propeller will do and stand I am fully warranted in claiming those vital qualities for the '" Hollands " propeller. Mr. Cochrane must remember too that I have challenged him to a contest between larQe propellers of each type. I now repeat it, and also protest against this further advertised assertion that he "has challenged and beaten all comers." Speaking of challenges, let me mention that I am still awaiting a notification from Mr. Handley Page, whom I challenged in July last (issue of 24th), and who stated that he would have a monoplane ready for the contest in three or four weeks thence. Yours faithfully, Oct. 25th, 1909. SIDNEY H. HOLLANDS. [Feeling that no further useful purpose can be served by this and similar correspondence between designers and makers of propellers —the advertising columns being the proper place for statements such as those referred to above—no further letters of this nature can be published.—ED.] LOAN OF MODELS WANTED. To the Editor of FLIGHT. SIR,—I am to lecture on November 9th, 1909, for the Erith Literary and Scientific Society on " Flying Machines." I bad hoped to be able to show a number of representative models other than those of my own monoplane. I have, however, found it very difficult to procure these models, and should esteem it a very great courtesy if any of your readers could assist me by lending some. I would, of course, pay any expenses attached, and guarantee their return in perfect condition. It would facilitate my work if lenders would permit me to mention their names as the designers or makers of any models in question. Yours truly, Belvedere, Kent. ALEXANDER THIERSCH. BRITISH FLYING GROUNDS. To the Editor of FLIGHT. SIR,—I have no doubt the two " Flying Weeks " that have just taken place at Doncaster and Blackpool have been a great success as far as " the gate " is concerned, but it seems to me that so far as aviation is concerned they have only served to impress more deeply upon the country ihe fact that England is terribly far behind France and America. During the entire period, at neither of these two meetings, did a single English machine leave the ground with any success, and some even came in for a considerable amount of ridicule. Of course, I do not include Mr. Cody in this category. In my opinion, the key to the whole situation lies in the fact that there is not at present a single really good aviation ground in the whole of England. Let me explain what, from my experience, I think is absolutely necessary for us to have in the way of a ground before English aviation can be successfully carried out. 697
Sign up to
Flight Digital Magazine
Flight Print Magazine
Airline Business Magazine
E-newsletters
RSS
Events
