DESIGN AND CONSTRUCTION OF PASSENGER STEAMERS. 295 



consumption would be from 4 to 8 per cent greater. The latter would also reduce the weight 

 of boilers, auxiliaries and fuel to a slightly less extent. 



On page 278 reference is made to tests of model propellers behind model hulls. I agree 

 with the author that these tests are important and valuable, and it is hoped that additional data 

 of this nature may be presented before the Society. Such experiments alone, however, are 

 not complete unless the test results of the models are compared with the trial results of the 

 vessel. It is suggested that, where possible, a comparison with the trial data be included. 

 Certainly the model results of propellers will be more convincing if they are shown to agree 

 closely with the trial data. 



Also, on page 278, the author refers to the desirability of more economical power plants. 

 In this respect, some American shipowners do not seem to appreciate fully the large economic 

 advantages of geared turbines and high superheat. If we compare a geared-turbine instal- 

 lation using steam superheated to 200 degrees with a well-designed triple-expansion engine 

 installation using saturated steam, it will show that the weight and cost of the engine instal- 

 lation will be about 20 per cent more than the turbine installation, and that the saving in fuel 

 consumption of the latter will be about 30 per cent. Geared-turbine machinery has been in- 

 stalled on a number of important passenger vessels, both American and foreign, and its eco- 

 nomic advantages are too important to be ignored. 



In this connection it would be of especial interest if Mr. Rigg could give the machinery 

 weight, steam and fuel consumptions for the two vessels specified on page 283. It will be noted 

 that the Old North State class is equipped with old-type machinery reciprocating engines and 

 vScotch boilers, whereas the American Legion has the most advanced type — watertube boilers 

 and geared turbines. 



I may add that Diesel engines are omitted from this discussion for the reason that the 

 horse-powers under consideration are for the most part far beyond the present accomplish- 

 ments in this field. 



In the tables on pages 279 and 282, the fuel consumption given is approximately 1.0 

 pound, per shaft horse-power. While this is a fair average performance for conservative 

 estimating, it is not as good as could be obtained with the most efficient machinery. With 

 geared turbines and high superheat, a fuel consumption of 0.85 to 0.90 pound per shaft horse- 

 power should be obtained for installations up to about 30,000 shaft horse-power, and above 

 this from 0.80 to 0.85 pound should be obtained. 



Referring to the last paragraph on page 281, it seems that 10 per cent margin is rather a 

 small allowance for average sea conditions. I should think fouling alone would require more 

 than this, and that at least 20 per cent should be allowed for a vessel in close schedule. 



Mr. Rigg's views on standardization are concurred in : "I think that large economies can 

 be effected by efficient standardization in machinery and detail parts. It would seem that 

 shipbuilders would profit considerably by adopting common standards as far as possible. 

 Such cooperation has proved profitable in other industries. This society might give valuable 

 assistance by appointing a committee to cooperate with shipbuilders in adopting such 

 standards." 



In closing, I may add that the Society is fortunate in hearing such a thorough presenta- 

 tion of this subject which is of especial interest at this time. 



Mr. W. M. McFarland^ Honorary Vice-President: — I was specially impressed, from the 

 nature of my own work, with some of the very encouraging remarks of Mr. Rigg with re- 



