Very little wood is now used for the planes of model aeroplanes; but to build a plane of veneer, it should first be cut to the shape required and then a strip of birch pinned and glued on the under-side of the leading edge for strength. The veneer is then pinned and glued to the ribs which have previously been bent to the correct camber. The reader may be reminded that birch is the most suitable wood for bentwood propellers, the wood being first cut to shape with a fret-saw, then soaked in hot water and bent over a bunsen burner to the desired pitch. This requires considerable experience, but can be done quite quickly by an experienced workman. For propellers up to 12 in. in diameter, use ¹/₁₆-in. wood; this should gradually taper off to ¹/₃₂ in. at the tips.
Fig. 170.—Geared Motor
for Model Aeroplane
Fig. 171.—Fixing Shaft
of Carved Screw
Making Motor for Model Aeroplane.—A geared motor suitable for a model aeroplane is given by [Fig. 170]. A cage E for the gears A can be made from ¼-in. by ¹/₃₂-in. strip iron, and the propeller shafts B can be made from cycle spokes. The illustration also shows a method of fixing the propeller to the shaft. The piece C is soldered to the shaft B, and engages with two holes drilled in the propeller boss, the propeller being secured by the nut D. The gears A have an equal number of teeth. There is no advantage in using a geared-up motor. F is the fuselage of the model.
Fixing Propeller of Model Aeroplane.—With a carved propeller, the motor hook can be secured to the propeller as in [Fig. 171]. If a bentwood propeller, the best way is to fasten a strip of tin round the centre and solder the motor hook to this.
CHAPTER XVII
Easily-made Tailless and
Box Kites
One of the difficulties that beset the juvenile kite-flyer is the inability to get the kite to rise from the ground unless there is a fairly good wind blowing. Even then the services of an assistant are required, whilst numerous trials to adjust the amount of weight on the tail, the position of the carrying thread on the kite, and the distance required to be run to get the artificial wind to enable the kite to rise above the surrounding buildings, are difficulties that damp the enthusiasm of the most inveterate kite-flyer.
To the kites sold in the shops the foregoing remarks apply. They are too heavy, and are suitable for flying at the seaside only. To make the sport interesting, the kite should fly in the least wind, and should be so made as to fly from the hand, the thread or string being paid out as the kite rises. It should be perfectly balanced so as to be stable in the most erratic wind. The kites shown in the accompanying illustrations, if made to the directions, will fulfil all the above conditions, and at the same time be easy of construction. The dimensions can be varied in proportion; but the would-be maker is advised to stick to the given sizes for the first attempt.