ECONOMICAL CARGO SHIPS. 95 



There is also an interesting point brought out in the paper, and that was in connection 

 with the size of the ships. We are all apt to be led away somewhat by the thought of the 

 large vessel being the most economical. Fig. (1, Plate 40, particularly, to which Mr. Robert- 

 son has already drawn attention, is, I think, most illuminating. It may be a common error 

 to imagine that the larger vessel will move more tons per annum, whereas that is a factor de- 

 pending entirely on speed, and it is interesting to note that a 350 or 400-foot ship' will ac- 

 tually move more cargo than the 500-foot ship at 10 knots. That is a very significant fact. 



Another point to which Mr. Robertson has referred, and on which I should like tO' say 

 a few words, is in reference to the value of the model experiments. I hope I shall not be 

 accused of special pleading. I think most of you know me well enough not to accuse me of 

 that, but I will give you a general idea of what so often happens. A shipbuilding company 

 spends one or two weeks in getting up a set of lines for a ship. The rest of the plans, in 

 the meantime, are going along, and then some time afterwards they feel they would like to 

 have a model tested to find out what power will be required to drive the ship at a certain 

 speed. Of course, that can be obtained from the model results very accurately, but it seems 

 to me that is the wrong way to go about it. I personally have tested a number of models 

 and have been able to show, as Mr. Robertson says here, that I can save 7 to 10 per cent on 

 the same displacement, for the same speed, and when I draw the attention of the shipbuilder 

 to this fact the answer is : — "Unfortunately, the work is so far ahead we cannot change it." 



Now it seems to me, if a little more time were given to model testing in the very earliest 

 stages of design, a great deal of economy could be obtained. We can supply the results of 

 what horse-power the ship will take to drive it 10 or 12 knots, but that is not all that is really 

 wanted — you want to have the best ship for the speed, and it is unfortunate, sometimes, 

 that the work has gone so far ahead that changes cannot be made. 



The final reference to concrete ships is one, perhaps, that will help supplement Mr. 

 Wig's paper this morning, and under given conditions it is rather interesting to note that 

 there still seems to be hope for the concrete ship, provided the first cost can be kept down. 



Mr. E. H. RiGGj Member: — This subject is one which has been given more attention 

 during the last few years before the technical societies than ever before. At first sight 

 this may seem curious when we reflect that they were war years, 1919 being still under the 

 influence of war conditions; on second thought this study will be found tO' be closely allied 

 to the war. Never before in our time has attention been so keenly directed to producing 

 ships quickly. Large programs of standard vessels have been adopted here and in Britain; 

 the opportunity came and a great deal of study of ship economics has been made. While 

 economy as ordinarily understood has necessarily been a secondary consideration in war-time 

 production, it still remains true that these large programs have furnished the opportunity, 

 and indeed have made necessary, detailed studies of ship economics on a large scale. Mr. 

 Robertson's contribution to the literature of this subject is most timely. The 1918 and 1919 

 published papers alone form quite a comprehensive literature and the Society is to be con- 

 gratulated on a useful paper which shows on its face a great deal of hard work. It should 

 commend itself particularly to shipowners and operators. How many times is an inquiry 

 for a ship based on some such analysis as given by Robertson in this paper or by Anderson, 

 Urwin, Baker, Kent and Donald in similar papers and read before sister societies in Britain? 



Other investigations covering the economics of still larger vessels are available, notably 

 by Sir John Biles and Lord Pirrie, also by the Canadian Royal Commission on Overseas 

 Communications. 



