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Aviation History
1918
1918 - 1110.PDF
OCTOBER 3, 1918. Rear view of the Fokker biplane. Reproduced from the Official Report. Fabric and Dope. The fabric is coarse flax, coarser and less highly calendered than the type usually met with, and a good deal heavier. It is colour-printed in the usual irregular polygons. The bright red paint, mentioned below, is removable by alcohol, but not soluble in it, coming off as a skin under the treatment. Under the paint is a dope layer—an acetyl cellulose. Neither paint nor dope presents unusual features. Weights— Paint . . Dope .. Fabric .. 92'o gms. per sq. m. 68-i 303-7Strength .. . . .. . - ' 1,772 k/m. Extension .. .. .. 70 per cent. Where the wings are not painted, the fabric is covered with a thin layer of dope only. [With these comments upon and extracts from the official report, we now commence our own description, in its original form, of the Fokker biplane.] - ' - ^~x [Ofthe machines now on view at the Enemy Aircraft View Rooms, Agricultural Hall, Islington, few are of greater interest than the Fokker biplane, D VII. This is mainly due to the fact that this machine is of recent manufacture the wings bear the stamp 24. IV. 18) and is at present employed in considerable numbers on the Western Front, but also on account of the unusual design of some of its more important component parts. In our issue of July 25th, 1918, we published a more or less diagrammatic perspective drawing of this machine, the set of wings then available for inspection being in a very damaged and incomplete condition. At the same time we gave a brief description of the main characteristics, which will, therefore, be familiar to readers of " FLIGHT." A complete set of main planes is now available, and by the courtesy of the authorities we have been permitted to inspect the tnachiru and to prepare the following drawings, sketches, and description.-—ED.] As its class letters (D VII) indicate, the Fokker biplane is of the single-seater fighting type of machine. As distinct from all previous types of Fokker machines it is fitted with a large water-cooled engine, with the radiator mounted in the nose of the body. As regards its wings the Fokker biplane forms a compromise between the one-and-a-half*- plane originated by the Nieuport firm and the ordinary single- Strutter machine with both planes of the same span and chord. In the Fokker the upper plane is considerably greater in area than the lower, while the difference between the two is not quite so pronounced as in the Nieuport type. The single pair of interplane struts form the link of similarity to what we have termed the ordinary single strutter, inasmuch as they are not of the Nieuport Vee type, but follow general practice with the one exception that they are braced by a single diagonal tube instead of the more usual incidence wires. From the general arrangement drawings it will be seen that the upper plane is mounted comparatively low in relation to the top of the fuselage, thus giving a fairly good view forward. Owing to the method of mounting the top plane there are no bracing wires running across the top of the body, interfering with the two machine guns, which are mounted above the bodj'. As pointed out in our preliminary report on this machine, it is of the " wireless " type as regards its wing truss, no lift wires or landing wires being provided, although internal drift wires are fitted in the wings. This feature has bedn made possible by choosing an extremely deep wing "section, very similar to that of the Fokker triplane described in our issue of May 30th, 1918, which gives ample room for a spar deep enough to take the wing loads without the external aid of lift wires. The construction of the wings will be dealt with in detail later, but at the present juncture a few words regarding the aerodynamic side of the question may not be amiss. When describing the Fokker triplane we expressed a doubt as to whether all things considered, the deep wing section was " worth while." One has become accustomed to regard such a deeply cambered section as liable to have a high resistance factor, although its lift coefficient may be, 'ai! probably is, high. At the time we strongly urged that the N.P.L. should carry out wind tunnel tests on a model of thel section to ascertain what, exactly, are its lift and dragf coefficients and other characteristics. Up to the time of ' writing we have no information to the effect that such tests have been made. Nor are we prepared to express the opinion that tests would necessarily reveal any astonishing and un- 1 expectedly good features. When, however, we see such a \ 1 section employed in a machine of so recent manufacture -^ as April of this year, we confess that we do think there is reason to suppose that the section cannot be so very inferior; otherwise why continue to employ it ? Surely the scientific German mind would not tolerate its retention just to please a designer of a " freak " machine ? One is therefore forced to the conclusion that the enemy has found that the wireless, wing truss with the (possibly) larger resistance section hasj^, its advantages over low-resistance sections plus their wire bracing. That the particular spheres of flying in which the section scores may be climbing and a high ceiling we should be the last to deny, but even so the enemy must, after weighing the cons and pros, have come to the result that these two attributes are of more importance than mere speed, if the latter is obtained at the cost of the former. Without the wind tunnel tests, or actual tests of a full size machine, one does not even know whether or not the Fokker biplane does have a comparatively low maximum speed. We would ^ y therefore again urge that tests be carried out in the wind tunnel, ^ and that the results be made known to British manufacturers and designers. 1111 ':. ^£_-, ^.--^Sfesassrs
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