In constructing model or toy aeroplanes the strips used are so slender that it is difficult to join them at the ends with brads without splitting them. If glue is used, there is danger of breaking two or more ribs, should it be necessary to remove a broken or defective rib.

An empty 22-gauge long cartridge can be formed into an elbow that will connect the framework accurately, give more strength than glue or brads, and allow a broken section to be removed without spoiling the other part of the framework. File off the end A, Fig. 1, so that the shell will form a straight tube, and file as shown in Fig. 2 with a three-cornered file. Then bend the two sections into the form shown in Fig. 3 and solder the adjacent edges. File off the rough spots and drill small holes, as shown, for the insertion of pins to hold the wood strips. Much time in the building of model aeroplanes can be saved by keeping a supply of these elbows on hand.

Fig.4 Cartridge Shells Used for Joints

Ill: Fig.4 Cartridge Shells Used for Joints

A deep rust on tools may be removed by soaking them in a strong, hot bath of potash and water for a half hour, then dipping them into a solution of 1 part muriatic acid in 2 parts cold water.