ACTIVE TYPE OF STABILIZING GYRO. 205 



to quite a comfortable percentage of the undamped rolling. But what are 

 we to say of other sea conditions which are much more aggravated; and 

 which, owing to their being more usual, are more important. It has been 

 shown in this art that if the tanks are placed high and are suppUed with 

 water representing a sufficiently great percentage of the displacement of 

 the ship the damping is good when the sea is synchronous, or approaches 

 synchronism. But who is to guarantee the continuance of the synchronous 

 condition? Certainly it does not exist on the high seas as we have found 

 them. 



Let us examine more minutely what happens when the sea is not 

 sychronous. Let us consider the instances only shghtly removed from 

 synchronism. We find that the tanks have already practically failed to 

 perform any useful function whatever and this approach or the percentage 

 of the departure where they fail grows smaller and smaller as the seas grow 

 heavier. Many curves have been analyzed with the tanks placed high, 

 if not higher, and with the damping effect placed practically upon the con- 

 ditions of the Ypiranga and Corcovado, where these tanks are placed at the 

 highest point relative to the center of oscillation so far recorded. Upon an 

 examination of these curves shown in Figs. 4 to 7, Plate 80, we discover that 

 a departure of about 13 per cent in a comparatively calm sea, and of only 

 about 9 per cent in a heavy sea, is sufficient to practically nuUify the use- 

 fulness of the tanks. 



A careful planimeter analysis of these curves which take into considera- 

 tion the sum of all rolling motions of the boat over a given time, show that 

 where the nattu-al roll is given as 100 in each case, and under identical 

 conditions, the rolling with all tanks in service amounts in Fig. 4 to 80; 

 in Fig. 5 to 73, and in Fig. 6 to 68; whereas Fig. 7 shows that under full 

 operation of the two damping tanks the area is 73.2. And in this latter 

 case the departure of the wave impulse from true synchronism has only 

 been gl per cent. We can by no means consider any such performance as 

 stabiUzing the ship, nor in any sense of the word fulfilling the object before 

 us; nor can it be considered as justifying the large burden in weight and 

 the great amount of valuable space occupied amidships, in the position where 

 space is most available and valuable for other purposes. 



Again referring to the recorded action of these tanks, I do not think 

 any of us would consider the performance shown in Figs. 4 to 7, Plate 80, 

 as coming imder the head of extinguished roUing or justifying the large 

 expenditure of funds or of the boat's carrying capacity as stated. 



It is sufficient to say that experience has demonstrated that damping 

 tanks are disadvantageous, if not positively dangerous, when out of syn- 



