plotted as graphs—Deductions—Various relations—How to obtain the most efficient results—Relations between the torque and the number of strands, and between the length of the strands and their number. § 7. Analogy between rubber and "spring" motors—Where it fails to hold. § 8. Some further practical deductions. § 9. The number of revolutions that can be given to rubber motors. § 10. The maximum number of turns. § 11. "Lubricants" for rubber. § 12. Action of copper upon rubber. § 12A. Action of water, etc. § 12B. How to preserve rubber. § 13. To test rubber. § 14. The shape of the section. § 15. Size of section. § 16. Geared rubber motors. § 17. The only system worth consideration—Its practical difficulties. § 18. Its advantages.

24 Section II.—Other Forms of Motors. § 18A. Spring motors; their inferiority to rubber. § 18B. The most efficient form of spring motor. § 18C. Compressed air motors—A fascinating form of motor, "on paper." § 18D. The pneumatic drill—Application to a model aeroplane—Length of possible flight. § 18E. The pressure in motor-car tyres. § 19. Hargraves' compressed air models—The best results compared with rubber motors. § 20. The effect of heating the air in its passage from the reservoir to the motor—The great gain in efficiency thereby attained—Liquid air—Practical drawbacks to the compressed-air motor. § 21. Reducing valves—Lowest working pressure. § 22. The inferiority of this motor compared with the steam engine. § 22A. Tatin's air-compressed motor. § 23. Steam engine—Steam engine model—Professor Langley's models—His experiment with various forms of motive power—Conclusions arrived at. § 24. His steam engine models—Difficulties and failures—and final success—The "boiler" the great difficulty—His model described. § 25. The use of spirit or some very volatile hydrocarbon in the place of water. § 26. Steam turbines. § 27. Relation between "difficulty in construction" and the "size of the model." § 28. Experiments in France. § 29. Petrol motors.—But few successful models. § 30. Limit to size. § 31. Stanger's successful model described and illustrated. § 32. One-cylinder petrol motors. § 33. Electric motors. 39 CHAPTER V. PROPELLERS OR SCREWS. § 1. The position of the propeller. § 2. The number of blades. § 3. Fan versus propeller. § 4. The function of a propeller. § 5. The pitch. § 6. Slip. § 7. Thrust. § 8. Pitch coefficient (or ratio). § 9. Diameter. § 10. Theoretical pitch. § 11. Uniform pitch. § 12. How to ascertain the pitch of a propeller. § 13. Hollow-faced blades. § 14. Blade area. § 15. Rate of rotation. § 16. Shrouding. § 17. General design. § 18. The shape of the blades. § 19. Their general contour—Propeller design—How to design a propeller. § 20. Experiments with propellers—Havilland's design for experiments—The author experiments on dynamic thrust and model propellers generally. § 21. Fabric-covered screws. § 22. Experiments with twin propellers. § 23. The Fleming Williams propeller. § 24. Built-up v. twisted wooden propellers 52 CHAPTER VI. THE QUESTION OF SUSTENTATION.
THE CENTRE OF PRESSURE. § 1. The centre of pressure—Automatic stability. § 2. Oscillations. § 3. Arched surfaces and movements of the centre of pressure—Reversal. § 4. The centre of gravity and the centre of pressure. § 5. Camber. § 6. Dipping front edge—Camber—The angle of incidence and camber—Attitude of the Wright machine. § 7. The most efficient form of camber. § 8. The instability of a deeply cambered surface. § 9. Aspect ratio. § 10. Constant or varying camber. § 11. Centre of pressure on arched surfaces 78 CHAPTER VII. MATERIALS FOR AEROPLANE CONSTRUCTION. § 1. The choice strictly limited. § 2. Bamboo. § 3. Ash—spruce—whitewood—poplar. § 4. Steel. § 5. Umbrella section steel. § 6. Steel wire. § 7. Silk. § 8. Aluminium and magnalium. § 9. Alloys. § 10. Sheet ebonite—Vulcanized fibre—Sheet celluloid—Mica. 86 CHAPTER VIII. HINTS ON THE BUILDING OF MODEL AEROPLANES. § 1. The chief difficulty to overcome. § 2. General design—The principle of continuity. § 3. Simple monoplane. § 4. Importance of soldering. § 5. Things to avoid. § 6. Aerofoil of metal—wood—or fabric. § 7. Shape of aerofoil. § 8. How to camber an aerocurve without ribs. § 9. Flexible joints. § 10. Single surfaces. § 11. The rod or tube carrying the rubber motor. § 12. Position of the rubber. § 13. The position of the centre of pressure. § 14. Elevators and tails. § 15. Skids versus wheels—Materials for skids. § 16. Shock absorbers, how to attach—Relation between the "gap" and the "chord" 93 CHAPTER IX. THE STEERING OF THE MODEL. § 1. A problem of great difficulty—Effects of propeller torque. § 2. How obviated. § 3. The two-propeller solution—The reason why it is only a partial success. § 4. The speed solution. § 5. Vertical fins. § 6. Balancing tips or ailerons. § 7. Weighting. § 8. By means of transversely canting the elevator. § 9. The necessity for some form of "keel". 105 CHAPTER X. THE LAUNCHING OF THE MODEL. § 1. The direction in which to launch them. § 2. The velocity—wooden aerofoils and fabric-covered aerofoils—Poynter's launching apparatus. § 3. The launching of very light models. § 4. Large size and power-driven models. § 5. Models designed to rise from the ground—Paulhan's prize model. § 6. The setting of the elevator.