In addition to determining what type of construction and what form of surface would give the greatest “lift” with the smallest “drift,” these whirling-table tests supplied data as to how much greater the actual resistance of the wing with its necessary guy-posts and guy-wires was than the theoretical resistance, found by extrapolation from the results obtained in the tests of rigid [p190] curved surfaces formed of wood. The first of this series of tests, the results of which are given below, was made November 30, 1898, on the superposed wing shown in Plate [37], Figs. 1 and 2. It should be noted, however, that when this test was made the wing was not provided with the stiffening strips or the vertical partitions.
Weight of wing = 1000 grammes; weight of guy-posts, etc., = 475 grammes; distance of mean center of gravity of guy-posts, etc., from pivots of balance arm = one-half distance of CP of wing from pivots of balance arm; the wing, therefore, had a lever arm of two to one with reference to weight of guy-posts, etc., so that the equivalent weight of guy-posts, etc., = 237 grammes. This gives 1237 grammes of equivalent load on the wing = 2.73 pounds. Area of wing = 21.85 square feet. Therefore load on wing = 0.125 pounds per square foot.
| Angle of chord. | Revolutions of turn-table. | Velocity of center of wing (ft. per min.) | Velocity (ft. per second). | Drift (grammes). |
| 2.0° | 10.75 | 1086 | 18.1 | 255 |
| 3.0° | 10.0 | 1010 | 16.85 | 255 |
| 5.0° | 9.5 | 960 | 16.0 | 255 |
| 10.0° | 7.75 | 783 | 13.0 | 255 |
| Angle of chord. | Drift (pounds). | Foot-pounds per sec. RV. | Calculated soaring speed carrying 0.5 pounds per sq. ft. (ft. per sec.). | |
| 2.0° | 0.561 | 10.15 | 36.2 | |
| 3.0° | 0.561 | 9.47 | 33.7 | |
| 5.0° | 0.561 | 8.98 | 32.0 | |
| 10.0° | 0.561 | 7.3 | 26.0 |
The very interesting phenomenon was noted in this test that the “drift” or resistance of the wing seemed to remain unchanged at soaring speed at different angles of elevation. It is hardly probable that this result is accurate, for the “balance arm” undoubtedly twisted under the action of the wing, and this caused it to strain on its pivots, and thus, to a certain extent, falsify the record as to drift.
A test of a single-tier wing at different angles of elevation was made on December 6, 1898. This wing was nearly the same as those used in actual flights of Aerodromes Nos. 5 and 6 in May and November, 1896, the wing being of the same width fore and aft, but somewhat shorter. The actual wing was a little too long to permit its being used on the whirling-table in the limited space of the shop.
Weight of wing = 420 grammes; weight of guy-posts, etc., = 320 grammes; equivalent weight of guy-posts, etc., = 150 grammes applied on the wing. Therefore, total load on wing = 570 grammes. Area of wing = 11.2 square feet; equivalent load on wing = 0.112 pounds per square foot.
| Angle of chord. | Revolutions of turn-table. | Velocity of center of wing (ft. per min.) | Velocity (ft. per second). | Drift (grammes). |
| 2.0° | 11.6 | 1195 | 19.9 | 210 |
| 3.0° | 9.75 | 1005 | 16.7 | 157 |
| 5.0° | 8.25 | 850 | 14.2 | 133 |
| 10.0° | 6.75 | 695 | 11.6 | 129 |
| 12.5° | 6.0 | 618 | 10.3 | 129 |
| Angle of chord. | Drift (pounds). | Foot-pounds per sec. RV. | Calculated soaring speed carrying 0.5 pounds per sq. ft. (ft. per sec.). | |
| 2.0° | 0.462 | 9.2 | 42.1 | |
| 3.0° | 0.345 | 5.77 | 35.3 | |
| 5.0° | 0.293 | 4.16 | 30.0 | |
| 10.0° | 0.284 | 3.29 | 24.5 | |
| 12.5° | 0.284 | 2.92 | 21.8 |
In this test it is to be noted that the “drift,” or resistance, while considerably greater at soaring speed for 2 degrees than for 5 degrees, remains practically the same between 5 degrees and 1212 degrees. Comparing it with the preceding test with the superposed wing, it is seen that at soaring speed at an angle of 10 degrees, the single-tier wing having a load of 0.112 pounds per [p191] square foot, has only 129 grammes drift, while the superposed one, while supporting 0.125 pounds per square foot, has 255 grammes drift. Moreover, the soaring speed of the single-tier wing is only 11.6 feet per second, while the superposed one requires a speed of 13 feet per second.
As the superposed wing tested on November 30 was so weak structurally that it could not be made to keep its proper shape without adding an excessive number of guy-wires, it was decided that it was not adapted for use on the aerodrome, but before abandoning it the partitions and strips were added and it was again tested on the whirling-table on March 1, 1899, with the following results:
Weight of wing = 905 grammes; weight of guy-posts, etc., = 320 grammes; equivalent weight of guy-posts, etc., = 150 grammes applied at CP of the wing; equivalent load on the wing = 1055 grammes = 2.321 pounds; area of wing = 21.85 square feet; equivalent load on wing = 0.1062 pounds per square foot.