The last twelve months have brought out a surprising number of new aeroplanes, while notable progress has been made in the standard types. To realize the immense strides or flights forward in the construction of heavier-than-air machines, one need only set the 1911 models beside the aeroplanes of a year or two years since. Even to the eye of the layman in such matters, the older machines are beginning to appear obsolete. In a previous volume, it was suggested that within a few years the aeroplane of to-day would appear like cumbersome stage coaches to one familiar with racing automobiles, and certainly the prophecy is being quickly realized. The general tendency is in the direction of greater simplicity in design in passenger-carrying craft, as in model aeroplanes. Both the monoplane and biplane types are being developed side by side, and each continues to have its enthusiastic advocates. The increase in the passenger-carrying qualities is realizing the most sanguine hopes. Aeroplanes have carried fifteen passengers for several miles. The speed qualities of machines have developed correspondingly. If the development of model aeroplanes leads the way in perfecting heavier-than-air machines, as many believe, the monoplane form seems destined to replace all multiplane types. During the past year practically all of the biplane forms have been abandoned by model builders. As a result of wide experiments, it has been found that the monoplane exerts more sustension per unit of surface than any two or three-plane machines. In theory, it is, of course, possible to increase the sustained force by setting one plane above another, but in practice it has been found that the planes must be set so far apart that the arrangement is impracticable. When planes are separated, they must, of course, be stayed and trussed to keep them rigid, and all this adds to the weight and complexity of the machine. [Illustration: A good specimen of plane building.] [Illustration: "Finish one end of the blade before cutting away the opposite end."] [Illustration: Model aeroplane. Designed by Cecil Peoli.] The builder of model aeroplanes has a great advantage over the designer of man-carrying crafts. The spread of the wings of his model is comparatively small, and the problem of staying and trussing is greatly simplified. The monoplane, especially in a model, requires practically no staying at all. Then again the skin friction is greatly reduced in the monoplane form. Simple as it is, there are great possibilities in the arrangement of these surfaces. The effect of outline upon resistance again may be more closely observed in the monoplane than in the multiplane forms. In other words, if your model goes wrong, it is far easier to locate the fault and rectify it than in the more complicated arrangement of planes.