Materials.—­The materials needed for the gliders to be described are moderately stout paper—­cream-laid notepaper is somewhat heavy for the purpose—­and a little sealing wax or thin sheet metal for weighting.

[Illustration:  Fig. 126.—­Paper glider:  Model “A.”]

[Illustration:  Fig. 127.—­How to launch Model “A.”]

Model “A.”—­Double a piece of paper 8 inches long and 2-1/2 inches wide, and cut out, through both folds, the shape shown in Fig. 126.  Flatten the piece and fold the “head” inwards four times on the side away from the direction in which the paper was folded before being cut out.  Flatten the folds and fix to the centre a little clip formed by doubling a piece of thin metal 3/16 by 1/2 inch.  Make certain that the wings are quite flat, and then, holding the glider between thumb and first finger, as shown in Fig. 127, push it off gently.  If the balance is right, it will fly quite a long way with an undulating motion.  If too heavy in front, it will dive; if too light, it will rise suddenly and slip backwards to the ground.  The clip or the amount of paper in the head must be modified accordingly.  This type is extraordinarily efficient if the dimensions, weighting, and shape are correct, and one of the easiest possible to make.

Model “B.”—­The next model (Fig. 128), suggesting by its shape the Langley steam-driven aeroplane, has two sets of wings tandem.  Double a piece of paper and cut out of both folds simultaneously a figure of the shape indicated by the solid lines in the diagram.  The portion A is square, and forms the head weight; B indicates the front planes, C the rear planes.  Bend the upper fold of each pair into the positions B1, C1, marked by dotted lines.  Their front edges make less than a right angle with the keel, to ensure the wings slanting slightly upwards towards the front when expanded.

The model is now turned over, and the other wings are folded exactly on top of their respective fellows.  Then the halves of the head are folded twice inwards, to bring the paper into as compact a form as possible.  It remains to open out the wings at right angles to the keel, and then raise their tips slightly so that the two planes of a pair shall make what is called a “dihedral” angle with one another.

[Illustration:  Fig. 128.—­Details of paper gliders:  Model “B” above, Model “C” below.]

Before launching, look at your model endways and make sure that the rear planes are exactly in line with those in front.  It is essential that they should be so for straight flight.  Then grip the keel at its centre between finger and thumb and launch gently.  Mark how your glider behaves.  If it plunges persistently, trim off a very little of the head.  If, on the contrary, it settles almost vertically, weight must be added in front.  The position of the weight is soon found by sliding a metal clip along the keel until a good result is obtained.