In designing a motor base bear in mind that it must be made as long as possible for installing the motor, and broad enough to afford stable support for the wings, the whole being kept as light and as rigid as possible. Since the length of the flight depends directly upon the length of the motor, the frame of your model should be at least two feet in length. The width of the frame may vary widely, as a glance at the successful model aeroplanes of the year will prove. For racing model aeroplanes, the base may be increased to four or even five feet in length. THE FAMOUS "ONE OUNCER." The one-ounce models, which have been brought to such perfection in England, are among the simplest aeroplanes to build. Fig. A models have a record of 1,500 feet. The adjustment is delicate, however; it is a very "tricky" affair to manage, and whether you can get the remarkable flights made abroad is another matter. For the stick, select a piece of straight-grained ash or some light wood three feet in length and one-quarter of an inch square. The planes should be cut from a thin board one-sixteenth of an inch thick. The main plane should measure fifteen inches by three inches, and the smaller plane eight by one and a half inches, thus giving them a high aspect ratio. They should taper slightly towards the ends. Round off the corners of both planes and sandpaper the edges down. If the wood will stand it, work it down, using a sharp plane or sandpaper. The planes should be bent by steaming slightly across the middle and set at a slight dihedral angle. [Illustration: A — The Famous "one Ouncer." B — A Small Experimental Model. C — A Modified Burgess Webb Model.] The model is driven most efficiently by a six-inch propeller. If it be a one-piece blade, prepare a propeller blank six inches by one inch, cut from a half-inch board. Cut away to the thinnest possible blade. Use a very simple support for your propeller shaft as well as for the motor anchorage at the extreme forward end. The planes should be tied with rubber strands to the stick and glued in position when properly adjusted. Try out your model with a motor consisting of two strands of one-eighth-inch rubber, and increase if necessary. You will need all your ingenuity and skill and workmanship to construct a stable model even of so simple a design which will come within one ounce. Throw it with the wind. A MODIFIED BLERIOT. In improving the lines of the various self-raising models, many of the designs have been greatly simplified. With the number of members reduced, the construction of a successful model becomes much easier and the chances of failure more remote. A simple rectangular frame with two planes driven by twin propellers requires very little skill or experience to put together. It is very easy to locate and correct the trouble in such a model, and quickly adjust it to rise and fly for considerable distances.