SHIP TYPES IN SHALLOW WATER. 85 
The next two sets of curves, Plates 32 and 33, are for vessels of a rather 
broad and comparatively fine type. 
It is often of interest to know at about what speed the first “hump” 
is likely to occur for a given depth of water. The speed-length ratios at 
which this maximum resistance may be expected, have been plotted on a 
depth-length ratio base in Plate 34. In this case the total resistance of the 
model has been taken. Other published results have been added for com- 
parison, and from these, which are mostly for torpedo boat destroyers and 
vessels of a somewhat similar type it appears as if the “hump’”’ for a given 
depth of water occurs at slightly higher speeds in the fuller forms. 
Observations of the wave formation at the critical speeds confirm those 
already given by previous writers. At or near these speeds the vessel tends 
to form a train of waves at the stern which extends for some distance from 
each side of the ship and at right angles to the same. After passing this 
point the normal type of bow and stern wave gradually reappears. 
It is possible, therefore, with the limited dimensions of the tank, that 
the sides may have some influence upon the results at these speeds. As, 
however, the first critical speed, especially at the smaller depth-length ratios, 
would be practically impossible of attainment in the types given, any slight 
error involved does not have much weight. 
The writer regrets that lack of time has prevented a fuller investigation 
and perhaps a more detailed analysis of the results; but so far as the above 
information goes, it is hoped that it may throw some further light upon the 
somewhat obscure effect of shallow water upon the resistance of vessels. 
DISCUSSION. 
VICE-PRESIDENT McFarLAND:—Gentlemen, you have heard the paper by 
Professor Sadler on “The Resistance of Some Merchant Ship Types in Shallow 
Water.”” Discussion is now open. It is always desirable to have a discussion, if 
possible. . 
Pror. C. H. PEaBopy, Member of Council:— I agree with the Chairman that 
a discussion is very important when we can have one, and that this paper is well 
worthy of a discussion, but at the same time I am almost inclined to believe that 
discussion is impossible. Here a very important piece of work has been done and 
the results are given to us. We have no hesitancy in accepting the results, and 
having said as much as that, I do not think we can say much more. 
