IN A SINGLE-SCREW CARGO SHIP. 169 



A very curious thing is that the model with the corner cut off actually shows less resist- 

 ance than the shipshape form for quite a range of speeds in each case. The difference in 

 resistance, howe\er, amounts to only about 1 per cent below and about 2 per cent above the 

 resistance of the shipshape model. Now, when putting the two facts together, the box-shaped 

 model has a resistance approximately of 3 to 3.5 per cent above the shipshape. The bilge 

 keels added to the shipshape model would account for 2.5 to 3 per cent in resistance, so that 

 the box-shaped model and the shipshape model would be practically identical in resistance. 



There is one other important point in regard to these model tests for the finer models. 

 Professor Sadler has given us the curve of sectional areas and the curve of load-water 

 plane — the outline of the load-water plane, for each model — and you will notice, as a basis 

 for the tests, that a certain model tested at the British National Tank was used, but there is 

 some departure in the outline of the load-water plane. 



I compared the results of Professor Sadler's tests with the results published of these 

 British tests, and I was very much astonished to find the result of this slight difference in 

 the outline of the load-water plane fonvard. The resistance was actually increased for the 

 Sadler models by about 20 per cent. That happens in these finer models where hollow water 

 lines are necessary. In the full model, I may say that it does not occur, and the full model 

 shows up wonderfully well. 



In regard to Commander McEntee's paper, I have only had time to glance at it, but it 

 well deserves the most careful study. I have, however, made a comparison between Pro- 

 fessor Sadler's full model and Mr. McEntee's model. Mr. McEntee's model is 0.789, I 

 think, in prismatic coefficient. Professor Sadler's model was 0.801 prismatic coefficient, but 

 there is a slight difference in the way the prismatic coefficient w^as taken — the aperture is 

 included in Mr. McEntee's figures, so that the two models are practically identical. If we 

 reduce the square box-shaped model of Professor Sadler to the dimensions of Mr. McEntee's 

 ships, having the same displacement and the same draught ratio, we find that the minimum 

 resistance, taking a cross curve on Mr. McEntee's four models, shows 1,880 shaft horse- 

 power at 11 knots and Professor Sadler's model YIC shows 1,930 with a square bilge, assum- 

 ing the same propulsive efficiency. That shows that there has been a loss of 50 horse-power 

 only in the square bilge model, over the best results of these four models — as a matter of 

 fact, the very best comes between Mr. McEntee's model No. 2133 and model No. 2134, and 

 falls almost exactly on model No. 2023, which, by the way, is a model based on results pub- 

 lished by the British National Tank. 



There is one question I would like to ask Mr. McEntee, and that is in regard to the 

 slip. He has not defined it sufficiently clear for me to know just what he means. There 

 is the apparent slip and the true slip. Do these slips refer to the effective slip measured with- 

 out correction for wake, or do' they refer to the face slip measured with and without the 

 wake correction? 



I wish, personally, to thank the gentlemen who have presented these papers. 



The President : — We have some written discussions on these papers which will ap- 

 pear in the proceedings. Time does not perm.it us to have them presented in full at this 

 period. 



Professor W. Hovgaard, Member (Communicated) : — I consider Professor Sadler's 

 and Mr. Yamamato's experiments very important and interesting. I have long been under 



