Fig. 23.
Fig. 24. and Fig. 25.
Fig. 26.
The writer, when exhibiting at Olympia this year, distributed 500 of these paper models, and the almost uncanny way in which they righted themselves when started from all sorts of impossible positions greatly interested the visitors. In fact, numbers of persons spent considerable time and ingenuity in trying to force the little glider to turn over or dive, but quite without success.
In order to test the turning capacity of this design, a rudder should be fixed to the tail, and the model launched at a moderate speed, when it will be found that it turns quickly and without any pendulum motion, and without any perceptible tilt. And although the writer’s experiments with the paper model and with many larger ones on the same plan have run into thousands, none of the models have ever been induced to come down in any other position but on their feet. The largest model, which measured 6 ft. 6 in. in length, was launched both upside down and with its head pointing vertically to earth from a height of 30 ft., and in each case righted before it reached the ground and landed on its skids.
As a further lifting surface, a very simple expedient offers itself in the shape of a duct built on the box-kite principle. The diamond-shaped box has been proved over and over again to be a very efficient lifting device, but it has not yet been tried on an aeroplane (Fig. 27). It is also a great stabilizer, since the air entering into the diamond-shaped opening is collected and compressed into the top angle there, and the whole box is thus practically suspended from its apex line in absolute stability. The lifting efficiency of such a box—or rather the top portion of the box, for the bottom part is not needed on our machine—is considerably greater than the value of the entering edge, and if run the whole length of the machine it forms a triangular girder of great strength, giving rigidity to the whole structure. The lifting efficiency is doubled by allowing the centre third of the girder to be open, as the dead air from the front part escapes, and the back part forms a new entering edge.
