CHAPTER XVI.
PROPELLERS,
MOTORS, GEARS, AND WINDING DEVICES.
There are four kinds of propellers:
1. Propellers carved out of solid and laminated blocks.
2. Metal propellers with curved or twisted surfaces.
3. Built up propellers. In this type a small block is used as a hub, and the wood or metal fans are projected out from this. The fans are attached on the diagonal.
4. Propellers made of pressed wood veneer. These are excellent, but require more skill and more apparatus to make.
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Figs. 244-251.
The carved out propeller is the one most generally used and is not only a good exercise in modeling with a knife, but is a good serviceable kind. There are a number of types of propellers, named mostly by men who have designed them. For simplicity in laying out and carving, I like the Langley type. A rectangle is made of wood, say 34″×112″×6″, Fig. 244. Draw the diagonals, as in Fig. 245. With a radius of 14″, and center at the intersection of the diagonals, draw a half-inch circle. Connect the diagonal lines and the circumference of the circle, as in Fig. 246, and cut down to the outline as it now appears. The blank is now as shown in
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