ft. As a rule the ribs are at right
angles to both main and rear spars.

The tension of the internal bracing wires should be just sufficient to
give rigidity to the framework. They should not be tensioned above that
unless the wires are, at their ends, bent to form loops. In that case a
little extra tension may be given to offset the probable elongation of
the loops.

The turnbuckles must now be generously greased, and served round with
adhesive tape. The wires must be rendered perfectly dry and clean, and
then painted with an anti-rust mixture. The woodwork must be well
varnished.

If it is necessary to bore holes in the spars for the purpose of
receiving, for instance, socket bolts, then their places should be
marked before being bored and their positions confirmed by whoever is in
charge of the workshop. All is now ready for the sail-maker to cover the
surface with fabric.

ADJUSTMENT OF CONTROL CABLES.--The adjustment of the control cables is
quite an art, and upon it will depend to a large degree the quick and
easy control of the aeroplane by the pilot.

The method is as follows:

After having rigged the controlling surfaces, and as far as possible
secured the correct adjustment of the control cables, then remove the
packing which has kept the control levers rigid. Then, sitting in the
pilot's seat, move the control levers _smartly_. Tension the control
cables so that when the levers are smartly moved there is no perceptible
snatch or lag. Be careful not to tension the cables more than necessary
to take out the snatch. If tensioned too much they will (1) bind round
the pulleys and result in hard work for the pilot; (2) throw dangerous
stresses upon the controlling surfaces, which are of rather flimsy
construction; and (3) cause the cables to fray round the pulleys quicker
than would otherwise be the case.

Now, after having tensioned the cables sufficiently to take out the
snatch, place the levers in their neutral positions, and move them to
and fro about 1/8 inch either side of such positions. If the adjustment
is correct, it should be possible to see the controlling surfaces move.
If they do not move, then the control cables are too slack.

FLYING POSITION.--Before rigging an aeroplane or making any adjustments
it is necessary to place it in what is known as its "flying position."
I may add that it would be better termed its "rigging position."

In the case of an aeroplane fitted with a stationary engi