A very satisfactory monoplane can be made from the plans shown in Fig. 49.

The material for the frame should be quarter-inch white pine or spruce. The six long strips are 30 inches in length, and for fastening, holes should be drilled and the connection made by passing fine soft wire through them and binding fast.

The top frame, formed of four of these long strips, should be made first, with particular attention to the measurements, so that both sides shall be exactly the same size and weight.

At the rear end the two long strips may be wired together temporarily. The propeller shown in the drawing can be made at any time from a piece of white pine ⁷/₈ inch thick and 12 inches long by 1³/₄ inches wide. It is a good piece of whittling work.

The ³/₈-inch hole for the shaft should be bored first, and the propeller blades reduced to a thickness of ¹/₈ inch at the centre of the blade, and ¹/₁₆ inch or less at the edges.

The shaft needs to be strong, and should be made of a piece of ³/₈-inch dowel rod. Make a saw cut with back saw in the end, which is to be fastened in the propeller.

When ready to assemble, push this end into the ³/₈-inch hole in the propeller, drive in a soft pine wedge with a little glue, and a rigid fastening will result.

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.The four sides of the frame are now whittled down to fit the block, and wired to it.

Last comes the question of motive power.

This is the great problem. The writer is opposed to encouraging boys to believe that these toy aeroplanes can be made to fly great distances. The propeller would have to be made to revolve at high speed for several minutes in order to accomplish this, and the tension of rubber bands is not equal to it. The machines can be made to fly short distances only. The problem of aviation is now a question of motors, and the smallest gasolene motor, with its tank, etc., requires a fairly large aeroplane to lift it. No doubt, the problem will be solved within a short time, but it has not been done at the time of writing.

For this size of toy monoplane several large rubber bands may be tied together, fastened at the screw eye on one end and to a piece of strong linen kite cord at the other.

Pass this cord forward under the spool and up to the propeller shaft.

Drill a small hole in the shaft, draw the cord taut, and fasten it through this hole.

While the model has no planes as yet, it is wise to get the propeller working before putting them on, as the space for working is freer. Wind up the propeller until the bands have been stretched to their limit, then let go. It may be necessary to place wheels at the rear, the same as in front. On a smooth floor, the machine should be drawn forward several feet by the action of the propeller.

It is entirely practicable, on a plane of this size, to use the works of an ordinary alarm clock in place of rubber bands.

Remove the outer casing of an old clock; loosen the four brass nuts that hold the frame together, and take out all the wheels, except the axle on which the mainspring is fastened. Put the frame together again with the four nuts.

The axle for the mainspring extends outside of the frame, and is threaded to receive the handle for winding. Take this handle off. Drill a hole in the end of the propeller shaft, slightly smaller than the mainspring axle, and screw the latter into the propeller shaft.

You now have the clock-works on the end of your shaft, and it is necessary to fasten a strip of pine ¹/₂ in. by ¹/₄ in. to the upper sticks of the frame in order to wire the works fast, as they must not be allowed to turn. By turning the propeller you wind up the clock, and as soon as you release it, as there is no escapement now to regulate the spring, it tries to unwind at once, and the propeller starts at terrific speed. Look out for your hands, as the propeller blades have no conscience.

This action, although strenuous, is short lived, but much more powerful than rubber bands. The spring of an ordinary alarm clock is powerful enough to drive a wooden two-bladed propeller 12 inches in diameter with blades two inches wide at the outside. It will draw a monoplane of this size along the floor several feet.

Having finally decided the question of power, it remains to attach the planes.

The remaining long strip is wired to the top pieces, 12 inches from the front, and the plane, made of silk, oiled paper, or very thin card-board, attached.

In many toy aeroplanes the bands of rubber are not stretched, but twisted. The shaft in this case is a wire which, after being fastened to the propeller, passes through a glass bead and then the frame, ending in a hook to which the rubber bands are attached. There must be a perfectly clear space from front to back of the frame. The glass bead between the propeller and frame is to relieve the friction.