FlightGlobal.com
Home
Premium
Archive
Video
Images
Forum
Atlas
Blogs
Jobs
Shop
RSS
Email Newsletters
You are in:
Home
Aviation History
1913
1913 - 0888.PDF
AUGUST 16, 1913. THE THEORY OF THE DUNNE AEROPLANE.* THIS small addition to the evening's programme has been made possible by the courtesy of Mr. Mervyn O'Gorman, who has cut out a portion of his lecture in order to make room for me. You, as scientific people, will realise that this is just about as generous a thing as a man can do, and I can assure Mr. O'Gorman that I am proportionately grateful. The title of Mr. O'Gorman's lecture has suggested to me that perhaps after all the simplest and most readily comprehensible way of describing this machine is to present it in its aspect of a com bination of a number of stability devices. This lecture will, there fore, be more qualitative than quantitative. The first person to try the effect of negative wing tips was Fig. 1.—Zanonia Leaf. (From JCriiik der Drachenfliegcr), Professor Marey—he tried it on a double sheet of note-paper, weighted as a glider. The first person to propose the use of backward-sloping wings was Mouillard. In advocating this plan-form he does not appear to have had stability in his mind at all, nor did he propose a permanent slope-back. His object seems to have been simply to provide a means for varying the speed. His apparatus was a man-carrying, motorless affair ; the wings, pivotted at the shoulder, being kept pointing forward at slow speeds, and sloped-back at high speeds. More modern machines which combine the sloped-back wings with the negatively disposed tip differentiate themselves naturally into two distinct classes. In one of these is contained all machines of Fig. 2.—Etrlch. (From 1905 Patent). that type which in Austria and Germany is styled "Zanoniaform," the other comprises those types with which I prefer to experiment. bo tar as I know, the Zanonia leaf represents Nature's solitary J3 m the Botanical Kingdom at the production of a gliding Fig. 1 shows a front elevation and plan view of this extraordinary rrfwhJ °" *1! SeC *" toenewy seed-pod is placed right in front hrW ,h StltUte%the kading ed8e of this ™* aeroplane, so as to Bang the centre of gravity into the proper position. The wines wh7/h J^r ehher SidC- As/he I"* wiLrfand dries, theTps nretnf, ™T%1 **"' °f ^ Wl^S' CUrl UP behind s° "to present a very marked negative angle of incidence Ahlborn of Berlin was the first to draw attention to the gliding Tblr-? I*62*00™16.*'-, Various Persons have attempted* embody >ts characteristics ,n full-size aero-surfaces, Bleriot among i tim?.^' »He" E!nCu has'Ihowe'er' ^ven the greatest amoun of time and attention to the study of this division of the retreating- Zlv ™$lMi-A 1S.\2 Sh,°WS a P'an and front elevation of the h/hL fon SA11' t!,kefn fl0m the I9°5 Patent- You wi» ^e that t rhtn? TA th£ leaf Pre»y^ely. The cross-sections shown in the patent drawing are nearly identical with those embodied in r VX^TTTA^ V~H »A,eI?n^tical S9** of Great «*»*». i>y J. w. Dunne, A.F.Ae.h. (Read at Meeting on January 29th, ion.) the Weiss machine; but the Weiss form was more elongated fore and aft, and was, I understand, evolved independently. Later Etrich added a tail (Fig. 3), and modtfied h.s man, wings, C°EtrSaha's had many followers, particularly in Germany, and doubtless the names of many machines built on these lines will Fig. 3.—Modern Etrich. (From Kritik der Drachenflieger). occur to you, but it is with the general characteristics of sloped-back;. wings that we have to deal, and this division is best described, as in Germany, as the Zanonia division. Violently opposed to the Zanonia type in most characteristics are the wing forms in the other division of the retreating-wing, negative-tip group : the division to which I have given most of my attention since 1904.t It is, perhaps, hardly worth v/hile devoting any of the limited time at our disposal to an elaborate description of the shape and contour of these wings. As you know, I give the wings a much more definite arrow form (see Fig. 4) than that of the Zanonia type ; the tips are rolled down in front instead of rolled up behind, so that we have a concave under surface instead of a concave upper surface in this region ; while the outstanding feature of the type is the fact that the whole wing forms the roof-part of a tunnel running backwards and outwards across the wing, the crown of the tunnel being sloped back at a greater angle than are the wiDgs themselves, and the sides of the tunnel preferably converging towards the rear end. The improvement in efficiency gained by this method of construction is quite extraordinary ; but as I wish to confine myself to-night to the safety devices embodied in the wings, I must for the present ask you to take my word for it that this converging tunnel tends to produce a positive pressure under the negative wing-tip, so- that for the same amount of negative pressure on the tip we are able to use a greater negative angle than in the Zanonia type. And it is the geometrical difference between the angle at the tip and the angle at' Figs. 4a and 4<5. the front of the machine which counts for most, though not for all, in natural stability. t My attention having been accidentally directed to fluid flow in divereine converging and vena-contracta pipes, it occurred to me thaTwings builtHrsuch lL QuTtTdlCnftrTT f$™*ZL <**>* Afferent from the o^ary, and - of °nv?tUratlR,T.U °^ fe *""" ?.f preSSUre> and were therefore Jorthy (To be coniintted.) 914
Sign up to
Flight Digital Magazine
Flight Print Magazine
Airline Business Magazine
E-newsletters
RSS
Events
