are also considerably heavier, and where the saving of
weight is essential, the difference is largely in favor of
spruce. This will be seen in the following table:

Weight Tensile Compressive
per cubic ft. Strength Strength
Wood in lbs. lbs. per sq. in. lbs. per sq in.
Hickory 53 12,000 8,500
Oak 50 12,000 9,000
Ash 38 12,000 6,000
Walnut 38 8,000 6,000
Spruce 25 8,000 5,000
Pine 25 5,000 4,500


Considering the marked saving in weight spruce has
a greater percentage of tensile strength than any of the
other woods. It is also easier to find in long, straight-
grained pieces free from knots, and it is this kind only
that should be used in flying machine construction.

You will next need some spools or hanks of No. 6
linen shoe thread, metal sockets, a supply of strong
piano wire, a quantity of closely-woven silk or cotton
cloth, glue, turnbuckles, varnish, etc.

Names of the Various Parts.

The long strips, four in number, which form the front
and rear edges of the upper and lower frames, are called