Well-made screw — the key to a successful flight “butterflies”. Pick up the wood, without the ROE and knots. Billet screw vystrugat in the form of a rectangular bar size 160х8х10 mm. In the center of the puncture hole for the axis. Then make a paper template of one of the propeller blades. Aligning the centers of the template and of the bar, move the contours of the blade first on one half of the bar, and then another. Billet astrogate a knife strictly on the contour, do the same with a lateral projection. Holding the billet in his left hand, on the opposite half cut the right corners. When finishing, try to front (top) part of the blade was slightly convex and the lower flat or even slightly concave.

The screw is made smooth with sandpaper. At the same time to balance it: make the same weight of the blades. The screw can be ready to varnish, paint or varnish. Now Linden cut the top and bottom of the boss. They also carefully apply the sandpaper.
Two pine slats size 135X3X3 mm vystrugat plane or a knife. When processing it with emery paper, be careful not to round the edges of the bars, as this will make them less hard.
Bamboo cut rail with a length of 300 mm and a cross section of 4X3 mm (outer glossy side of the bamboo to cut impossible). Over a candle flame or a spirit lamp bend the workpiece along the contour of the part 5, transferred to 1:1 scale on paper, then carefully split the workpiece into two parts, each of which is processed to a cross section of 1,5X1,5 mm and sanded with abrasive paper. Hooks for attaching the rubber motor bend with round nose pliers steel wire according to the drawing. From strips of sheet metal 8 mm width roll up so that in a free rotated the axis of the screw. The tube is pressed into the hole of the upper boss. The upper end should be on the same level with the boss, the bottom may be beyond it.
6 pine slats to glue to the front and bottom lugs. To the last pre-attach the hook as shown in the drawing. On the rails the thread with a sizing clamp the frame of the wings. The lower ends of the wings, pre-lubricated with glue, insert into the hole of the lower boss. The tube in the upper boss insert the longer hook, the end of which fasten to the blades.
After the glue has dried, fit an wings on one side tissue paper (for better tension it can be lightly sprinkled with water). Now hook thread two thread model aircraft rubber section 1X4 mm, insert the screw and let the model in flight. If brightly colored wings, the model will resemble a butterfly.
V. JERKINS, the engineer

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