ECONOMICAL CARGO SHIPS—SOME MODEL EXPERIMENTS. 55 
Pror. Epwarp M. Brace, Member:—A paper like this requires a good deal of study 
to get the meat out of it, but I have had a chance to look into the matter quite closely, 
and I think perhaps a few general conclusions may be of interest to this meeting. 
One of the outstanding results of this investigation, to my mind, is this—it shows 
that for the speed at which cargo ships are ordinarily operated, say from.5 to.6 speed-length 
ratio, that the length of the run should never be less than 42 per cent of the length of 
the ship, and a very favorable length of entrance is 28 per cent. If you use an entrance 
of less than 25 per cent, the resistance increases very rapidly. This favorable condition 
is shown in Fig. 11, Plate 23, by the curve marked EW, which was obtained from a model 
with a parallel middle body of about 31 per cent. The run was about 42 or 43 per cent. 
and the entrance some 26 or 27 per cent. You will notice that it is the best curve over 
quite a considerable range of speed-length ratio from .55 to .65. 
One rather curious fact is shown by the other curves. You notice that DW crops 
down below EW at the lower speeds. DW was obtained from a model which had about 
25 percent parallel middle body, and alonger entrance than EW. That curious fact seems 
to hold, that for the rather low speeds you want a fairly long entrance, and as the speed 
increases to speed-length ratios of .5 or .6, the entrance grows shorter, and above that 
value the entrance gets longer again, for the best results. 
Of course it may be said it is not always possible to get in a run of 42 per cent; that 
it calls for such a fine run, particularly if you have the machinery aft; that you will not 
be able to get breadth enough for the engine bed. That may be so; but I wonder if it is 
always taken into account, if a certain type of machinery calls for a full after body, 
that machinery must be capable of developing 10 per cent more power; and should not 
that fact be considered in striking a ya ee between the advantages and disadvantages 
of that arrangement? 
Take two vessels of 30 per cent ae middle body, and in one place your parallel 
middle body at midships, and in the other shift it to the position I have indicated. There 
is easily a difference of 10 per cent in the power required. The one with the parallel 
middle body symmetrical with midships will drive 10 per cent harder than the ship with 
the longer run, and any type of machinery which calls for the full after body must have 
charged up against it the fact that this after body will require 10 or 12 per cent more 
power than the easier after body. 
Many more points may be brought out here. In Fig. 9, Plate 23, we have the re- 
sults given in terms of ¢ and p, and you will notice in almost every case the curves marked 
with values in the neighborhood of 1 drive harder. I think nearly so per cent of the 
models that come to the tank at Michigan to be tested have the entrance and the run of 
about the same length. The fact that the run should be longer than the entrance does 
not seem to have penetrated into all the shipyards and to have reached those people 
who have the designing of the lines in their charge, and I am wondering to what extent 
the results which are presented here get into the shipyards anyway. What measures do 
those in charge of the shipyards take to see that such results as these are available to 
their draughtsmen and designers? In how many shipyards can you find the complete 
transactions of this Society, to say nothing of the foreign societies which have contributed 
to this question for the last fifteen years? Shipyards are willing to spend thousands of 
dollars on recreational features for organized labor, but when it comes to spending five 
hundred dollars for the good of the draughtsmen, that is different. Five hundred dollars, 
I think, would buy all the transactions that are necessary, and I believe that would be 
