In addition to good cutting tools, a good half-inch chisel is most important. A concave chisel will be found handy in carving propellers. Some of the best propellers have been whittled out with an ordinary penknife, and sometimes a dull one at that, so that after all a good penknife is the most essential tool of all. With this little handful of tools, you will find you can build up the most delicate models. The world has been ransacked for material which will give the greatest possible strength for its weight. The use of aluminum is, of course, familiar. The search has also brought out the comparatively unknown metal, "magnalium," which, although a trifle heavier, is believed to be much more desirable on account of its greater strength. In a search for strong, light wood the builders of aeroplanes have searched the tropics. One of their discoveries has been balsic wood, which is of a feather weight. It is exceedingly soft and easily worked, but has the drawback of being rather pithy and easily split. A severe jar is likely to discover some weak point. It will be found valuable, however, for the shorter members of the model. Some model builders use balsic wood as a filling for hollow sticks. The wood may be strengthened by covering with cloth glued firmly about it. It is also used as a filling for thin aluminum tubing. In all the search for materials nothing has been found to compare with bamboo for lightness and strength. A number of successful model aeroplanes have been built this year in which the central sticks and frames are built entirely of bamboo. Bamboo is especially valuable in constructing the smaller members. It can be bent either by the dry-heat process, described elsewhere, or by steaming. Bear in mind that the strongest part of the stick lies just beneath the hard glazed outer surface. The only drawback of bamboo is a tendency to split at the ends. The extreme lightness of the material on the other hand makes it possible to make rigid joints by glueing and winding with fine thread touched with glue. [Illustration: Working drawing of the Flemming Williams model] [Illustration: An imported Flemming Williams model. English record 2600 feet.] The lighter woods, whitewood and poplar, are much used by model builders. They are easy to work, especially whitewood, because of its freedom from knots and cross grains. Some builders prefer ash on account of its strength. Beech has rather less strength, some fifteen per cent, while spruce is little more than half as strong as ash. The quality of the wood varies considerably according to its nearness to the bark of the tree. The wood used for model aeroplanes should be well seasoned; a year is not too long.