ve an aspect ratio of 10 to 1.

For A GIVEN VELOCITY and A GIVEN AREA of surface, the greater the
aspect ratio, the greater the reaction. It is obvious, I think, that the
greater the span, the greater the mass of air engaged, and, as already
explained, the reaction is partly the result of the mass of air engaged.

Not only that, but, PROVIDED the chord is not decreased to an extent
making it impossible to secure the best camber owing to the thickness
of the surface, the greater the aspect ratio, the better the lift-drift
ratio. The reason of this is rather obscure. It is sometimes advanced
that it is owing to the "spill" of air from under the wing-tips. With
a high aspect ratio the chord is less than would otherwise be the case.
Less chord results in smaller wing-tips and consequently less "spill."
This, however, appears to be a rather inadequate reason for the high
aspect ratio producing the high lift-drift ratio. Other reasons are also
advanced, but they are of such a contentious nature I do not think it
well to go into them here. They are of interest to designers, but this
is written for the practical pilot and rigger.

5. Stagger.--This is the advancement of the top surface relative to the
bottom surface, and is not, of course, applicable to a single surface,
i.e., a monoplane. In the case of a biplane having no stagger, there
will be "interference" and consequent loss of Efficiency unless the
gap between the top and bottom surfaces is equal to not less than 1 1/2
times the chord. If less than that, the air engaged by the bottom of the
top surface will have a tendency to be drawn into the rarefied area over
the top of the bottom surface, with the result that the surfaces will
not secure as good a reaction as would otherwise be the case.

It is not practicable to have a gap of much more than a distance equal
to the chord, owing to the drift produced by the great length of struts
and wires such a large gap would necessitate. By staggering the top
surface forward, however, it is removed from the action of the lower
surface and engages undisturbed air, with the result that the efficiency
can in this way be increased by about 5 per cent. Theoretically the top
plane should be staggered forward for a distance equal to about 30 per
cent. of the chord, the exact distance depending upon the velocity
and angle of incidence; but this is not always possible to arrange
in designing an aeroplane, owing to difficulties of balance