ON A MODEL OF THE U.S. AIRCRAFT CARRIER LANGLEY. 89 
It will be seen on Plate 36 that the stabilizer was capable of controlling the roll 
with the largest wave that the wave maker could produce. In the case of the wave 
produced by the 6-inch eccentricity, the stabilized roll was 5 degrees as compared 
with 21% degrees for the larger wave, corresponding to a 7-inch eccentricity. This 
was due to lack of proper adjustment of the control gyro. The control gyro was 
adjusted after rolling in the smaller wave and in the larger wave the roll was reduced 
to 2.5 degrees. 
8. The estimated stabilizing moment of the gyro-stabilizer as run during the 
experiments was 20 pound-feet. This was the minimum stabilizing moment 
which could be obtained because the gyro-motors could not be run at any ‘ower 
speed. To compare the estimated stabilizing moment with a known impressed 
moment, additional tests were made in which the stabilizer was operated against 
a rolling moment produced by a weight moving harmonically from side to side in 
the model through a distance of 8 inches. This weight was actuated by an electric 
motor placed in the model which was without bilge keels and was free to roll in 
still water. By controlling the speed of the motor it was possible to make the har- 
monic rolling moment agree with the natural period of the model. By varying the 
weight it was possible to increase or decrease the rolling moment. The result of 
this investigation is shown on Plate 37. From this it is seen that, with a maximum 
rolling moment of 31.33 pound-feet, the gyro-stabilizer reduced the roll from 37.5 
degrees to 3 degrees. 
It is to be noted, also, that it required several rolls before the angle was so 
reduced. When the rolling moment was increased to 39.33 pound-feet the roll 
was reduced by the gyro-stabilizer from 46 degrees to 5 degrees though taking a 
somewhat greater number of rolls todoso. When still further increase in the rolling 
moment was made to 47.33 pound-feet, the capacity of the gyro-stabilizer was 
clearly insufficient to cope with the same, the roll being reduced from 42 degrees 
to 34 degrees only. It is apparent from these data and from the action of the gyro- 
stabilizer when opposed to the rolling moments of waves, that the moments required 
to produce a given angle of roll in still water are considerably greater than the mo- 
ment of synchronous waves when causing a similar roll. It is also clear that the 
gyro-stabilizer is capable of controlling a maximum harmonic rolling moment of at 
least 50 per cent greater than the stabilizing moment exerted by the gyro. Though 
the disturbing moment may temporarily exceed the stabilizing moment, it apparently 
does not act for sufficient time to cause much increment in the arc of roll. This 
appears to confirm certain claims advanced for the so-called ‘‘Active Gyro- 
Stabilizer.”’ 
9. Asa final test an investigation was made of the increase of towing resistance 
of the model when caused to roll by an harmonic rolling moment applied to the 
model while being towed in smooth water. The results obtained, as reduced to 
effective horse-power curves for the ship, are shown on Plate 38. From these it 
appears that at a speed of 15 knots the effective horse-power would be increased 
from 3,000 to 3,300 when the ship is rolling through an arc of 25 degrees, and to 
3,600 when rolling through an arc of 45 degrees, corresponding to an increase in 
