The large plane is 4½” in the widest place and is 20” long. It is the shape of Fig. 242 in outline, the straight side being to the rear. The outline of the plane is a steel or brass spring wire 1/16” diameter and is spliced at the center of the long sides, being soldered at this point. The ends of the wire lap over an inch or more. There are but two ribs which are 5½” from the outer ends. The ribs have a slight curve upward, most of it being near the free edge of the plane, Fig. 243. The ends of the ribs are bent at a right angle and are soldered to the outside framework of wire. The cover of the plane is made of prepared silk and is made ¼” larger all around than the size of the outline of the wire frame. A ¼” hem is then turned which gives strength to the edge. The cover is now over cast with needle and thread to the framework, stretching fairly tight. [Illustration: FIG. 243.] The framework of the large plane is not secured directly to the wooden framework of the model, but is soldered to wire loops that in turn lie flat on top of the spines of the frame, Fig. 242, _a_, _a_. This gives opportunity to tie with string so as to try out the model. If it is too far forward, it can be slipped back and vice versa; when the correct position is located, it is permanently wired to the wooden framework. The fore plane is attached by means of rubber string. This is known as the Mann monoplane, and is a commercial product. The propellers will be further discussed in the next chapter. CHAPTER XVI. PROPELLERS, MOTORS, GEARS, AND WINDING DEVICES. There are four kinds of propellers: 1. Propellers carved out of solid and laminated blocks. 2. Metal propellers with curved or twisted surfaces. 3. Built up propellers. In this type a small block is used as a hub, and the wood or metal fans are projected out from this. The fans are attached on the diagonal. 4. Propellers made of pressed wood veneer. These are excellent, but require more skill and more apparatus to make. [Illustration: FIGS. 244-251.]