In place of fins or wings the flying machine is equipped
with a propeller, the action of which is furnished by the
engine. Fins and wings have been tried, but they don't
work.
While operating on the same general principle, aerial
propellers are much larger than those used on boats.
This is because the boat propeller has a denser, more
substantial medium to work in (water), and consequently
can get a better "hold," and produce more propulsive
force than one of the same size revolving in the air.
This necessitates the aerial propellers being much larger
than those employed for marine purposes. Up to this
point all aviators agree, but as to the best form most of
them differ.
Kinds of Propellers Used.
One of the most simple is that used by Curtiss. It
consists of two pear-shaped blades of laminated wood,
each blade being 5 inches wide at its extreme point,
tapering slightly to the shaft connection. These blades
are joined at the engine shaft, in a direct line. The propeller
has a pitch of 5 feet, and weighs, complete, less
than 10 pounds. The length from end to end of the two
blades is 6 1/2 feet.
Wright uses two wooden propellers, in the rear of his
biplane, revolving in opposite directions. Each propeller
is two-bladed.
Bleriot also uses a two-blade wooden propeller, but
it is placed in front of his machine.
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