106 NON-ROLLING PASSENGER LINERS. 



teresting to compare them with, or to state them in terms of the specific loading 

 permitted by the underwriters. Take a concrete case of the transport Henderson, 

 of 10,000 tons displacement, 488 feet length, with maximum beam of 48 feet and 

 draught of 19 feet 9 inches — the allowable load per running foot for the section 

 where the stabilizer is located is 14.5 tons. The load due to the weight of the sta- 

 bilizer plus the maximum gyroscopic stabilizing moments, figured as load upon the 

 vessel, is at maximum only 10 tons, and with average stabilizing moments about 6 

 tons per running foot. In other words, the stabilizer loads are much less than nor- 

 mal cargo loads. Some of the vessels carrying heavy machinery to France were 

 loaded as high as 28 tons per running foot. The foregoing makes clear, in a very 

 practical way, the relation these forces bear to the vessel's ordinary loads. 



Another definite advantage secured by the stabilizer is the elimination of the 

 bilge keels. Dealing only as they do with "V" square, they can never be of service 

 other than in the heaviest rolling — at all other times they are a positive menace. 

 The well-known drag of bilge keels in perfectly calm weather is not only ever pres- 

 ent but represents positive losses, even in excess of those calculated. This has now 

 been positively observed in the case of a large 20-knot ship, the performance with 

 and without bilge keels for the same shaft revolutions, loading and trim being 

 known. Moreover, a ship is never trimmed very accurately longitudinally, giving 

 the bilge keels a frontal attack component with the attendant eddies, consuming ad- 

 ditional power of no small magnitude. Fig. 10, Plate 45, gives diagrams illustrat- 

 ing this point. 



In rough weather the bilge keels afford an extra opportunity for the waves to 

 lay hold of the vessel in rolling. Recently it has been definitely determined that the 

 power required by bilge keels under the condition of pitching, even in a moderate 

 sea, increases the propelling power to a point much beyond what had been supposed. 

 In the case of a 10,000-ton vessel with standard keels, even with moderate pitching, 

 an increased propelling power of about 9 per cent has been observed. In a sta- 

 bilized ship it is possible to eliminate bilge keels. There should be no hesitancy in 

 omitting keels, as an exceptionally large and successful fast passenger ship has 

 been operated without bilge keels for years. 



A reduction in stresses of the propelling machinery of a stabilized ship repre- 

 sents another important gain, especially in the case of twin-screw vessels where the 

 windward propeller is held very much more satisfactorily to its duty — not only 

 saving power but preventing the racking strains due to overspeeding when the screws 

 are "rolled out." The efficiency of a propeller falls off abruptly as its blades even 

 approach the surface, especially where the dip of the waves allows the slightest 

 aeration of the water. For efficiency a propeller requires to be kept down in stiff 

 water. 



Prevention of deterioration in cargo applies especially to ships carrying live 

 stock. Figures have been furnished by a concern transporting horses during the war 

 showing that, in a heavy storm during a single trip, their losses per trip often 



