Such a large angle of incidence
results in a very poor lift-drift ratio (and consequently great
loss of efficiency), except at very low velocities compared with
the speed of modern aeroplanes. At the time such aeroplanes
were built velocities were comparatively low, and this defect
was; for that reason, not sufficiently appreciated. In the end
it killed the ``canard'' or ``tail-first'' design.
Aeroplanes of the Dunne and similar types possess no
stabilizing surface distinct from the main surface, but they
have a longitudinal dihedral which renders them stable.
The main surface towards the wing-tips is given a
decreasing angle of incidence and corresponding camber. The
wing-tips then act as longitudinal stabilizers.
This design of aeroplane, while very interesting, has
not proved very practicable, owing to the following
disadvantages: (1) The plan design is not, from a mechanical
point of view, so sound as that of the ordinary aeroplane
surface, which is, in plan, a parallelogram. It is, then,
necessary to make the strength of construction greater than
would otherwise be the case. That means extra weight.
(2) The plan of the surface area is such that the aspect ratio
is not so high as if the surface was arranged with its leading
edges at right angles to the direction of motion. The lower
the aspect ratio, then, the less the lift. This design, then,
produces less lift for weight of surface than would the same
surface if arranged as a parallelogram.
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