Fig. 21.—Section of cloth hemmed, and reinforcing strips sewn on.
The bottom planes. The cloth on the bottom planes is made up of two sections, divided by the space in the centre of the lower plane which the operator occupies. These sections are made and reinforced in exactly the same manner as that for the top plane just described but are one foot less than half as long.
The cloth is tacked over the front horizontal beam and then stretched tightly over the curved ribs and fastened with tacks at the ends. Fasten the corners of the cloth first and smooth it out before driving the tacks in the ribs. Ordinary brass headed upholsterer’s nails are used but they should not be long enough to pass all the way through the ribs.
A strip of felt 3/8 of an inch wide and four feet long is laid on the cloth directly over each rib so that it comes between the head of the tack and the cloth. This precaution may seem unnecessary to some, but it greatly reduces the liability of having the cloth tear when under pressure. The tacks along the ribs are spaced about 4 inches apart A heavy weight held against the under side of the rib by an assistant, when the tacks are driven in will provide a firm foundation to hammer against.
A very good method of fastening the cloth to the ribs is to sew a pocket on the under side of the surface and into which the ribs may be slipped.
The rear ends of the ribs may be fitted with metal tips by tapering the end down until it is round and measures 1/2 inch in diameter. A 1/2 inch brass ferrule such as that used on file handles is then forced on.
The rudder planes are covered on both sides. The fabric is stretched tightly over the frame and then tacked along the edges. The edges should be turned under before tacking so that there is no possibility of the cloth tearing out.
The cloth at the ends of the planes should be securely fastened to the struts by means of tacks. This will relieve the ribs of some of the strain and correct a tendency for them to pull in towards the centre.