Note that if the leading edges of the front wings are bent slightly downwards the glider may fly much better than before.

A good specimen of this type is so stable that if launched upside down it will right itself immediately and make a normal flight.

Model “C.”—­This is cut out of doubled paper according to the solid lines of Fig. 128.  The three sets of planes are bent back in the manner already described, but the front planes are given a somewhat steeper angle than the others.  This type is very stable and very fairly efficient.

General Remarks.—­Always pick up a glider by the keel or middle, not by one of the wings, as a very little distortion will give trouble.

The merits of a glider depend on length, and on straightness of flight; so in competition the launching height should be limited by a string stretched across the room, say 6 feet above the floor.  If the room be too short for a glider to finish its flight, the elevation at which it strikes the wall is the measure of its efficiency.

Out-of-door flights are impracticable with these very frail models when there is the slightest breeze blowing.  On a perfectly calm day, however, much better fun can be got out of doors than in, owing to the greater space available.  A good glider launched from a second-floor window facing a large lawn should travel many yards before coming to grass.

Large gliders of the types detailed above can be made of very stout paper stiffened with slips of cane or bamboo; but the time they demand in construction might perhaps be more profitably spent on a power-driven aeroplane such as forms the subject of the next chapter.

XXV.  A SELF-LAUNCHING MODEL AEROPLANE.  By V. E. Johnson, M.A.

This article deals not with a scale model—­a small copy of some full-sized machine—­but with one designed for actual flight; with one not specially intended to create records either of length or duration, but which, although small details must perforce be omitted, does along its main lines approximate to the “real thing.”

Partly for this reason, and partly because it proves a far more interesting machine, we choose a model able to rise from the ground under its own power and make a good flight after rising, assuming the instructions which we give to have been carefully carried out.  It is perhaps hardly necessary to add that such a machine can always be launched by hand when desired.

Before entering into special details we may note some broad principles which must be taken into account if success is to attend our efforts.