Construct two serviceable planes the same size, six by eighteen inches. These should be flat and covered as smoothly as possible. Now attach to the rear edges of each plane a series of three ailerons each two by five inches, fastening one at either end and the third at the middle. Make the frames of the ailerons of a very light lath strip and wire them to the rear edge in such a way that they may be swung up or down through a small arc. At the outer ends of each of the planes, attach semicircular tips, each with a base of six inches and a radius of six inches. These may be rounded off or cut away to sharp points as desired. They should also be attached so that they may be bent up or down and will hold their position. Mount the model on some simple arrangement of reed skids, so that it will be elevated at a very slight angle above the horizontal. The model complete should weigh about eight ounces. Equipped with twin motors of fourteen strands of one-sixteenth-inch rubber each, the propellers should be turned about four hundred times. A medium-pitch propeller will best serve your purpose. In flying this model, bear in mind that the flight will be directed in an opposite direction from the angle of the ailerons, or rudders, just as a boat answers its helm. The wing tips should be bent up or down until the flight is stable. The complete equipment of ailerons enable one to correct any defects in proportion which are likely to be needed in models built by beginners. AN EFFICIENT THREE-OUNCE MODEL. (Record 900 Feet) A surprising variety of designs may be carried out in models of the three-ounce class. One of the easiest to control is a broad adaptation of the Bleriot model, flown with its small surface forward. For a three-foot model, first build two planes of very light material. Wire frames are especially suited for this model. The main plane should measure two feet in length by four in width, or with an aspect ratio of six. The smaller plane, carried forward, should be one foot in length with the same aspect ratio. It will be found a good plan to carry the outer edges of this plane back, forming two inch squares at the rear edges. A plane with a slight camber will prove the more stable. For the frame secure two light sticks three-sixteenths of an inch square of some fairly strong wood; a straight spruce is good. Attach the motors to these sticks before completing the frame. Select some rigid support for the propeller axle. Prepare two ten-inch propellers, carving the blades from propeller blanks three-fourths of an inch thick. The motor will probably work best when made up of six strands of rubber, one-eighth of an inch square, although this should be finally determined by actual test flights. Keep all parts of the motors extremely light.