THE RESISTANCE OF SOME MERCHANT SHIP TYPES IN 
SHALLOW WATER. 
By ProFEssoR HERBERT C. SADLER, MEMBER OF COUNCIL. 
[Read at the eighteenth general meeting of the Society of Naval Architects and Marine Engineers, held in 
New York, November 16 and 17, 1911.] 
The effect of shallow water upon the resistance of vessels has been the 
subject of a certain amount of investigation and in a general way the in- 
fluence of depth of water upon the speed of a vessel is familiar to most 
members of the profession. 
In general, however, the published results refer to vessels of the warship 
type and more especially to destroyers, scouts and cruisers. 
During the past two years, when occasion permitted, a number of 
models of various merchant ship types have been tested in water of varying 
depth, in the ‘‘Tank”’ at the University of Michigan; and although it cannot 
be claimed that the whole field has been covered, the following results may 
prove of some interest and value. 
The characteristics of each form are given with the curves and it may 
be noticed that they range from fine to full types. Some of the broader 
types of from five to six beamsto the length, and one with V-shaped sections, 
have also been added. 
In each case the curves represent the residuary resistance in pounds 
per ton of displacement; and although perhaps the total resistance might 
have been used with sufficient accuracy for general purposes, it was thought 
advisable to adopt the above system so as to conform with the usual practice 
of the experimental tank. 
The false bottom was fixed at definite depths and all models were tested 
at these depths of water. As many of the models represented actual vessels 
and were not of the same length, they were loaded in each case to their 
respective load-draughts; hence the depth-length or depth-draught ratio 
varied in most cases. The values of the ratios are given on each curve. 
In connection with the above it may be of interest to note that the vari- 
ous “humps’’ in the resistance curves occurred at practically the same 
speed irrespective of the length of the model, which indicates that the speed 
at which the maximum resistance occurs is a function of depth of water 
rather than size of ship. , 
