COMPARATIVE TESTS OF BILGE KEELS AND A GYRO-STABILIZER 
ON A MODEL OF THE U. 8. AIRCRAFT CARRIER LANGLEY. 
By CoMMANDER WILLIAM McENTEE, CONSTRUCTION Corps, U.S. N., MEMBER. 
[Read at the twenty-eighth general meeting of the Society of Naval Architects and Marine Engineers, held in New 
York, November 11 and 12, 1920.] 
1. In recent rolling experiments carried out at the U. S. Experimental Model 
Basin on a model of the Langley, the results obtained are believed to be of sufficient 
interest to naval architects to warrant making them the subject of a paper for this 
Society. Incidentally there is shown one of the purposes for which the wave- 
making equipment at the Model Basin is employed. 
2. The experiments had for their object a comparison of the quenching powers 
of bilge keels and of a gyro-stabilizer so far as may be determined by model tests. 
As the Langley is being refitted to carry aeroplanes which are both to fly from 
and to land on her deck, it appears that the prevention of excessive rolling is a 
matter of greater importance than for other vessels. As an incident to the tests the 
increase of the towing resistance of the model when rolling was measured and the 
corresponding increase in effective horse-power required for the ship estimated with 
interesting results. 
3. For use in the tests a small gyro-stabilizer shown on Plate 39 was obtained 
from the Sperry Gyroscope Co. This was an exhibition stabilizer on hand, and, as it 
was not designed especially to suit the model, it was larger than necessary. Also 
the speed of the precession motor was not well adapted to the period of the model 
to give most efficient results. The designed stabilizing moment of the twin gyros 
when running at 7,000 revolutions per minute is 57.4 pound-feet, but during the 
tests the speed was cut down as far as possible to about 2,300 revolutions per minute, 
reducing the stabilizing moment to about 20 pound-feet, which was still considerably 
larger than necessary to quench heavy rolling rapidly. 
4. The dimensions of the Langley are:—Length, 520 feet ;beam, 65 feet; draught, 
16 feet; and 11,000 tons displacement. The model to 1/26th scale was first fitted 
with bilge keels, representing to scale, keels 15 inches deep by 180 feet in length and 
rolled in still water to obtain its declining angle curve. The bilge keels were then 
removed and another declining angle curve obtained. The results are shown on 
Plate 32, from which the quenching power of the bilge keels may be seen. Thus 
without bilge keels to reduce the angle of heel from 11 degrees to 3 degrees required 
about fifty-four swings as compared with eight swings with bilge keels. In making 
these tests a gyroscopic roll recorder was used so that, after the model had been 
inclined by hand and released, a continuous record was obtained showing how the 
rolling died out in the two cases. Typical curves are shown in Plate 33. In plotting 
angles of heel on Plate 32, the swing numbers correspond to successive hollows and 
