TO PROPELLERS OF OCEAN-GOING MERCHANT VESSELS. 89 
fective horse-power by the Taylor method and by calculation from the propeller data. There 
was quite some difference between these, which would be accounted for if the draught dur- 
ing the trial (which is not known) was less than 29 feet. 
Problem 13, Plate 27.—For the same reason as mentioned in Problem 4, this ship was 
run from Ambrose Light Ship to Fire Island Light Ship and return. Unfortunately, the 
only effective horse-power curve available was for a draught of 28 feet 2 inches. Assuming 
the effective horse-power to vary as a means of the ratios of the displacements and the dis- 
placements to the two-third power, we have: 
Displacement aty2OehtiZpimyane telomere rare erate ring in ors 16,900 
DisplacementyateZ 4 ehtan Ot) seein tae irae rien 14,250 
(C14 2501 NG O00) 27 renin dst ra nein oa Ninn Ge CPM a Mee tien pate set fa 0.894 
AAS OK ENG QOOMS ahets ihead Auten sate cea aaete ce ymin a ateda ease areal wae 844 
INU Aiea les ances, Misi reae aay BRA en MRE SUR aD Eh Ce IER MARTE 869 
E. h. p. (28 ft. 2 in. draught) at 11.64 knots = 1,860. 
E.h. p. (24 ft. draught) at 11.64 knots = 1,860 & 0.869 = 1,615. 
The above powers included the resistance of the rudder and bilge keels but not the propeller 
bosses which is estimated at 80, making a total effective horse-power of 1,695. This vessel 
was fitted with Diesel engines, the mechanical efficiency of which was about 75 per cent. 
The angle of the bosses with the horizontal plane was about 20 degrees. 
Problem 14, Plate 28.—This ship is the Great Northern, the trial-trip data of which 
were published in the Journal of the American Society of Naval Engineers. The values of 
effective horse-power, which were obtained by multiplying the shaft horse-power by the pro- 
pulsive coefficients as shown on the trial curves, are probably that for the bare hull, as the 
propulsive coefficients are quite low and as the propellers are apparently out of cavitation. 
The revolutions were calculated using the shaft horse-power from the trial data, and com- 
pared with the actual revolutions. Calculations were then made for the effective horse- 
power. The difference between the calculated effective horse-power and those obtained by 
multiplying the shaft horse-power by the propulsive coefficients could be taken as the power 
required for the appendages. 
CONCLUSION. 
In the foregoing are represented almost every type of seagoing merchant ships. Prob- 
lems 1 to 7 are single-screw ships and, with the exception of Problem 5, have full lines, the 
block coefficients being over 0.77. Problem 13 is a full-bodied cargo ship with twin screws. 
Problems 8, 9 and 10 are of the slow cargo and passenger type or moderate-speed freighter, 
fitted with twin screws. Problem 11 is a moderate-speed cargo and passenger ship, while 
Problems 12 and 14 represent high-speed passenger vessels. The vessel in Problem 5 was 
built for the coast trade between New York and Norfolk. When loaded to her deep draught 
(about 22 feet) her underwater body was similar to a moderate-speed cargo and passenger 
vessel with single screw. At the draught at which the trial was run (16 feet 11 inches), the 
underwater body was more like a sound or river steamer with a full midship section. 
The writer regrets that he had to include in this paper examples where either very accu- 
rate or full information was not obtainable, but was obliged to do so because of the lack of 
more complete data. 
