Briefly put, these results showed:—
1. The inefficiency of a propeller of the fan blower or of the static thrust type.
2. The advantage of using propellers having hollow-faced blades and large diameter.
3. That diameter was more useful than blade area, i.e. given a certain quantity (weight) of wood, make a long thin blade and not a shorter one of more blade area—blade area, i.e., as proportionate to its corresponding disc area.
4. That the propeller surface should be of true stream-line form.
5. That it should act on a cylinder and not tubes of air.
6. That a correctly designed and proportioned propeller was just as efficacious in a small size of 9 in. to 28 in. as a full-sized propeller on a full-sized machine.
Fig. 37.—An Efficient Propeller, but rather Heavy.
Ball bearings, old and new. Note difference in sizes and weights. Propeller, 14 in. diam.; weight 36 grammes.
A propeller of the static-thrust type was, of course, "first off," sometimes 10 ft. or 12 ft. ahead, or even more; but the correctly designed propeller gradually gathered up speed and acceleration, just as the other fell off and lost it, and finally the "dynamic" finished along its corresponding wire far ahead of the "static," sometimes twice as far, sometimes six times. "Freak" propellers were simply not in it.