FOULING OF SHIPS' BOTTOMS 



209 



By analyzing the data in this table regarding the extent of fouling we find that 

 87 per cent of all ships were fouled to some extent, and accordingly only 13 per cent 

 were clean. A more detailed analysis of these proportions is given in Figure 20. 

 By referring to this figure it will be seen that while 13 per cent were clean, 39 per 

 cent were lightly fouled, 27 per cent moderately fouled, and 21 per cent heavily 

 fouled. 



TOTAL NUMBER OF 

 SHIPS EXAMINED 



NUMBER OFSHIPS 

 HEAVILY FOULED 



NUMBER OFSHIPS 

 MODERATELY FOULED 



NUMBER OFSHIPS 

 LIGHTLY FOULED 



NUMBER OFSHIPS 

 NOT FOULED 



,250 



1 100%) 



,52 



(21%) 



-67 



(27%) 



, 98 



(39%) 



i 3 3 



(13%) 



Fig. 20. — Total number of ships examined and relative number in each of the four groups classified according to the amount 



of fouling on each vessel 



Table 2. — Total amount of fouling, by weight 





Date exam- 

 ined 









Num- 

 ber of 





Amount of 

 fouling per area 



Total amount 



Ship 



Length 



Width 



Draft 



areas 

 meas- 

 ured 



Size of areas measured 



Metric 



United 

 States 



Proteus 



Sept. 28, 1922 



Nov. 7,1922 

 Dec. 17,1922 

 Nov. 21, 1922 

 May 18,1923 

 Mar. 1,1924 



Feet 

 552.0 



Feet 

 62 



Feet 

 27.7 



4 



1 meter wide, water line 



to keel. 

 do 



60 kilograms.. 



5 kilograms 



2 kilograms 



3 kilograms 



2.5 kilograms.. 

 3 grams 



Kilos 

 8, 000. 0 



415.0 

 5, 954. 0 

 10, 612. 5 

 9, 987. 0 

 12.0 

 28.2 

 2.8 



Tons 

 8. 82 



.46 

 6. 55 

 11. 67 

 10.98 

 .013 

 .310 

 .003 



Fish Hawk ... 



147.0 



27 



11.0 



2 



Wyoming 



562.0 



93 



28.5 



4 



1 square meter _.. 



West Virginia.. 

 Leviathan 



624.0 

 906.9 



97 

 100 



30.5 

 23.7 



3 

 4 





Do 



906.9 



100 



23.7 



4 





America... 



Feb. 24,1923 

 Dec. 19,1923 



668.0 



74 



22.8 



5 





10 grams 



Do.... 



668.0 



74 



22.8 



5 



do 



1 gram 

















The exact amount of fouling on individual ships has been difficult to determine 

 because of complicating conditions at the time of dry docking. A fairly accurate 

 determination was made, however, for each of the eight ships listed in Table 2. The 

 amount of fouling on each was determined by calculations based upon accurate 

 measurements of the total amounts on limited areas, the sizes of which are indicated 

 for each vessel in the above table. The total amount of fouling on the entire ship 

 was then calculated on the basis of a knowledge of the length, width, and draft of 

 the ship and calculation of its wetted surface. It will be seen by reference to this 

 table that fouling was very severe on ships like the Proteus, a collier in the naval 

 transport service; while a passenger ship like the America had only a very small 

 amount of fouling. None of the vessels listed in this table indicates the maximum 

 amount of fouling occasionally found on ships. This has been estimated by reliable 

 authorities to exceed 500 tons per vessel occasionally, but fortunately few ships 

 are now permitted to become so foul before redocking, regardless of time intervals. 



