The groove in the rear end of the shaft is to take the thrust of the propeller, and hold it in the machine. This groove may be readily cut out with the knife, and smoothed with sand-paper. Two bearings are necessary to hold the shaft in alignment. The forward one is a strip of pine 1⁄4 by 3⁄4 , with a 3⁄8-inch hole bored at the centre. This hole should be sand-papered until the shaft turns in it freely. The rear bearing is a strip 5⁄8 by 3⁄8 inch, laid out as shown at a. The quarter-inch hole must be bored first. Next, drill two small holes with a fine drill on either side of the hole for the wires which are to hold the two pieces together. Next saw on the pencil line shown, removing the small piece x. Test the bearing by placing the small grooved section of the shaft in the quarter-inch hole to see if it turns freely. When this has been accomplished, the propeller and its bearings are ready for the monoplane.
Looking at the front view, the two uprights are 9 × 3⁄4 × 1⁄4 inches. At the top ends they are rabbeted as shown, and wired to the top frame. At the bottom they are wired to the long strips which form the long sides of the bottom frame.
Before putting these uprights on, a 1⁄4-inch hole should be drilled 11⁄2 inches from the bottom of each. These are to receive the 1⁄4-inch dowel rod which acts as the axle for the spool s. This rod should be 10 inches or more in length, so that brads or wire may be passed through the ends outside the uprights to keep the axle in place.
The small spool which acts as a pulley must be perfectly free to turn on this rod, and be kept in place by two brads driven through drilled holes on either side of it.
The front and lower parts of the frame are now ready to be assembled.
The four long strips constituting the body of the frame are all wired together at the back, temporarily. To finish the forward part, saw out a strip 3⁄8 × 1⁄4 inch, and form on each end a rounded bearing, as in the automobile, for two wheels 13⁄4 inches in diameter. Saw the wheels out of 3⁄16-inch basswood, drill a hole at each centre, place on the bearing, and fasten in place with a flat-head wire nail and a small washer next to the wheel. Sand-paper the wheels smooth, and see that they turn freely. Tack the strip, or wire it to the uprights, as low down as possible.
The rear end of the monoplane is a nice little problem. Cut out a block of pine from 1 inch to 11⁄8 inches square. In the side facing the front place a screw eye for fastening the spring or rubber bands.
The rudder is shown in the drawing. Drill two holes, as shown, and drive in brads or flat-head wire nails, as large as the hole, so that the rudder may be turned by hand, but not free enough to turn with the wind.
Next drill a hole clear through the block for the axle of the tilting planes.
It is not necessary that the axle be at the exact centre of the cube. It should extend quite through both planes as well as the cube, and be bent around the edges, so as to make them rigid. They should be snug enough to turn by hand, but not loose enough for the wind to shift.