CHAPTER XI.

HELICOPTER MODELS.

§ 1. Models quite easy to make. § 2. Sir George Cayley's helicopter model. § 3. Phillips' successful power-driven model. § 4. Toy helicopters. § 5. Incorrect and correct way of arranging the propellers. § 6. Fabric covered screws. § 7. A design to obviate weight. § 8. The question of a fin or keel. 113