OCR Text |
Show Aeroplane Propellers. Selected ash, which is both stronj: " and light and will not split under' vibration or shock, or built-up layers lay-ers of spruce with mahogany centers,, are the materials with which the propellers pro-pellers of aeroplanes such as are being be-ing used in the Kuropean war are constructed. con-structed. The framework of the machines, ma-chines, too, is generally made of wood,, spruce being much used on account of its straight grain and freedom front hidden defects. |