Another trial was made the same day with the same aerodrome, under similar conditions, except that the angle of inclination (α) was reduced to 7°. It now, with all the other circumstances of launching like those immediately before, behaved entirely differently, plunging head downward into the water at a distance of 30 feet. Once more it was shown beyond dispute that the wings must somehow be made even stiffer.

December 8. Another trial was undertaken with No. 5, the CG being 10 cm. in front of the CP at rest. The root angle of the wings was 18°, tip angle 27°, elevation of midrod 1 in 24. The other changes made since the previous trial consisted chiefly in the increased weight due to the longer and stronger frames and shafts that were made to carry 100 cm. propellers. The flight obtained was so short that it was as unsatisfactory as before.

The aerodrome rose in the air after leaving the launching apparatus, and then slid back into the water in the plane of its own wings. On the first trial, it struck the boat, and was slightly injured; on the second, with root angle of [p101] wings 10°, tip angle 20°, the flight partook of the same character, but the machine struck the water clear of the boat.

The fact that with the CG 10 cm. in advance of the calculated CP the aerodrome steadily rose in front, seems to indicate that the rule used at that time for calculating the CP (see Chapter II [◊]) was not very accurate. This rule was based upon the assumption that the tail, having an area equal to one-third the entire sustaining surface, supported one-third the total weight (expressed by the formula CP = 2CPwm + CPtm3, where CPwm and CPtm represent respectively the CP of the wings and tail in motion), and that the CP of each surface was one-fifth its width in front of the center of figure.

December 12. Four days later, the tail had been moved back 21 cm., thus carrying the CG back 7 cm., but the vertical rudder (weighing 105 grammes), for which there was now no room, was taken off, which in a measure counteracted this change.

A trial was then made with the wings set at an initial angle of 8° at the root and 20° at the tip. The aerodrome was released with the engines working under a steam pressure of 90 pounds, and soared off horizontally for some distance, when suddenly it swerved to the right as though something on that side had given out, and turning quite through 180° headed toward the boat, striking the water about 76 feet away. The time of the flight was 4 seconds.

It was found upon the recovery of the machine that one of the propellers had been twisted through 90°, so that the two were no longer symmetrical. The turning may have been due to this twist or to unequal influence of the wind upon the two wings; for when I applied the sand test to the wings after returning them to Washington, it was found that they deflected so much that the grains would not lie upon them, which, to a great extent, explains the failure to secure a better flight.

Thus the end of another year had been reached, and what might be called a real flight had not yet been secured. The only progress that seemed to have been made was that the aerodromes were not quite so unmanageable and erratic in their flights as at the beginning of the year, and that it had been demonstrated, at least to the writer’s satisfaction, that the power was sufficient for the work to be done. The launching device had been so perfected that it worked satisfactorily, but the problem of balancing seemed as far from solution as before.

1895

While, for convenience in narrating the progress of the work with the aerodromes, each year has been treated as a unit, it is, of course, understood that the work itself shows no especial difference between the closing of one year and the beginning of another. Changes which had important effects were introduced [p102] at various times, but were, of course, made as they suggested themselves without any reference to time or season. But while it was customary to make, from time to time, a résumé of the progress of the work, yet at the closing of the calendar year it was the custom to make a more complete digest of just what had been accomplished during the year.