214 



BULLETIN OF THE BUREAU OF FISHERIES 



Although the author is not aware of any detailed studies on the effect of fouling, 

 as regards increased resistance and consequent increased fuel consumption in ships 

 in actual operation that are moderately or heavily fouled, recent investigations by the 

 Navy Department show a considerable increase in fuel consumption for boats only 

 eight weeks out of dry dock and on which only small amounts of fouling could possibly 

 have accumulated, as the trials were made early in spring in the cold waters near Bos- 

 ton Harbor. The results of tests with a new submarine off Provincetown, Mass., 

 are given in Figure 22, from which it can be seen that the speed attained with a low 

 propeller action was decreased from 9.85 to 9.25 knots; and at high energy input 

 (1,050 kw.) this was reduced from 15 to 14.5 knots. If there is so great a reduction in 



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Fig. 22. — XJ. S. Submarine S-84. Standardization trials, measured mile. Provincetown, Mass., May 16-18, 1923. Vessel 



out of dock 56 days for run with foul bottom. Motor efficiency disregarded as virtually constant. with foul 



bottom; with clean bottom 



speed when the amount of fouling is barely noticeable, the proportionate decrease in 

 the speed of vessels heavily fouled must be very great indeed. 



These results are in accord with the observations of McEntee, quoted above, who 

 tested the resistance of recently submerged plates, with no discernible fouling, and 

 yet found a very noticeable increase in resistance, which for the plates used in his 

 experiments he calculated at an increase of almost 2 per cent per day. 



That similar results are obtained by actual tests with ships is seen from the state- 

 ment by Sir Archibald Denny, published as part of the discussions that follow the 

 McEntee paper. Denny states that "at their shipyard on the river Leven, a tribu- 

 tary to the Clyde, they have found an increase in resistance at the rate of nearly 



