William J. Claxton - The Mastery of the Air
with planes 144 feet long and 1 foot wide, and the other with planes 12 feet square. In the former the
entering edge of the plane would be twelve times as great as in the latter, and the lifting power would
necessarily be much greater. Thus, though both machines have planes of the same area, each plane
having a surface of 144 square feet, yet there is a great difference in the "lift" of the two.
But it is not to be concluded that the back portion of a plane is altogether wasted. Numerous experiments
have taught aeroplane constructors that if the plane were slightly curved from front to back the rear
portion of the plane also exercised a "lift"; thus, instead of the air being simply cut by the entering edge
of the plane, it is driven against the arched back of the plane, and helps to lift the machine into the air,
and support it when in flight.
There is also a secondary lifting impulse derived from this simple curve. We have seen that the air which
has been cut by the front edge of the plane pushes up from below, and is arrested by the top of the arch,
but the downward dip of the rear portion of the plane is of service in actually DRAWING THE AIR
FROM ABOVE. The rapid air stream which has been cut by the entering edge passes above the top of
the curve, and "sucks up", as it were, so that the whole wing is pulled upwards. Thus there are two lifting
impulses: one pushing up from below, the other sucking up from above.
It naturally follows that when the camber is very pronounced the machine will fly much slower, but will
bear a greater weight than a machine equipped with planes having little or no camber. On high-speed
machines, which are used chiefly for racing purposes, the planes have very little camber. This was
particularly noticeable in the monoplane piloted by Mr. Hamel in the Aerial Derby of 1913: the wings of
this machine seemed to be quite flat, and it was chiefly because of this that the pilot was able to maintain
such marvellous speed.
The scientific study of the wing lift of planes has proceeded so far that the actual "lift" can now be
measured, providing the speed of the machine is known, together with the superficial area of the planes.
The designer can calculate what weight each square foot of the planes will support in the air. Thus some
machines have a "lift" of 9 or 10 pounds to each square foot of wing surface, while others are reduced to
3 or 4 pounds per square foot.
CHAPTER XXV. The Wright Biplane (Cont.)
The under part of the frame of the Wright biplane, technically known as the CHASSIS, resembled a pair
of long "runner" skates, similar to those used in the Fens for skating races. Upon those runners the
machine moved along the ground when starting to fly. In more modern machines the chassis is equipped
with two or more small rubber-tyred wheels on which the machine runs along the ground before rising
into the air, and on which it alights when a descent is made.
You will notice that the pilot's seat is fixed on the lower plane, and almost in the centre of it, while close
by the engine is mounted. Alongside the engine is a radiator which cools the water that has passed round
the cylinder of the engine in order to prevent them from becoming overheated.
Above the lower plane is a similar plane arranged parallel to it, and the two are connected by light
upright posts of hickory wood known as STRUTS. Such an aeroplane as this, which is equipped with two
main planes, known as a BIPLANE. Other types of air-craft are the MONOPLANE, possessing one main
plane, and the TRIPLANE, consisting of three planes. No practical machine has been built with more
than three main planes; indeed, the triplane is now almost obsolete.
| 