WING COVERING AND PATCHING
The wings are covered with best quality Irish linen which must have a tensile strength of at least 50 lb. per inch width, undoped, and 70 lb. when doped.
The linen strips are sewed together on a sewing machine in such a way that when folded together they form a sort of bag which just slips over the wing frame. The seams then run diagonally across the wing. The bag is stretched up loosely and tacked temporarily along the leading edge. The edges are folded under a little and sewed together along the leading edge of the wing and the temporary tacks are removed. To hold the covering up to the ribs, thread is looped through from one side of the panel to the other around the ribs. The rough surfaces made by the thread along the ribs and the edges are covered over with strips of linen pasted on with dope. To make a smooth job, the edges of these strips are frayed out ⅛ in.
Three or more coats of dope are applied and rubbed down after each coating is dry. This is then covered over with one or two coats of varnish to make it more weatherproof and smooth. Varnish also prevents the dope from peeling off.
Dope shrinks the linen and makes it fit up tight to the framework.
Breaks in the fabric are patched by first removing the dope around the break with dope remover and then sticking on a patch with dope. This is applied with a rag instead of a brush in order to prevent the patch from becoming white. Ten to sixteen coats of dope are then applied over the patch, each coat being allowed to dry before the next is applied.
FAULTS IN FLIGHT, DUE TO IMPROPER ALIGNMENT AND HOW TO CORRECT THEM
An airplane pilot may experience difficulty with the flying qualities of his machine. Consequently he should know something about the conditions which are responsible for the various kinds of unsatisfactory flying qualities which are more or less characteristic of airplanes.
In the chapter on “Principles of Flight” the reader has been made acquainted with such terms as stability, instability, longitudinal stability, etc. For the purposes of rigging, however, it will be well to review these terms again.
Stability is a condition whereby an object disturbed has a natural tendency to return to its first and normal position. Example: a weight suspended by a cord.