NOTES FROM THE MODEL BASIN. 
By Navar Construcror Wititiam McEntes, U. S. Navy, MemBer. 
[Read at the twenty-fourth general meeting of the Society of Naval Architects and Marine Engineers, held in 
New York, November 16 and 17, 1916.] 
During the last year at the United States Experimental Model Basin the press 
of routine work has been such as to prevent any original investigations which would 
require the use of the basin for any great time. There has been opportunity, how- 
ever, to continue experiments relating to the part played by the frictional resistance 
of water in the resistance and propulsion of ships. 
The results of the tests reported in my paper, “Variation in Frictional Resist- 
ance of Ships with Condition of Wetted Surface,” read before the Society last year, 
indicated the importance of the condition of wetted surface as affecting the resistance 
of aship. Asa natural extension of this investigation, an attempt has been made to 
ascertain the corresponding effect of surface condition on the efficiency of propellers. 
The results as given in the present paper indicate that this is a matter of equal 
importance as affecting the economical operation of ships. 
Propellers used for naval work have customarily, especially on high-speed ves- 
sels, been carefully finished by machining the rear surface of the blades to a true 
helicoidal surface and finishing by hand the leading face so as to make the entire 
surface smooth and polished. In doing this, however, it seems that the object was as 
much to get blades which would have uniformity of pitch and balance as to get a 
smooth frictional surface. For merchant vessels propellers are commonly made with 
blades of cast iron or cast steel, and no finish is given except trimming off the rough 
places with a chisel or rough file. 
To ascertain what may be expected from the difference in naval and merchant 
practice, four 16-inch propellers, made as closely as possible to the dimensions shown 
in Fig. 1, Plate 62, were tested at a uniform speed of 5 knots. 
Two propellers were of bronze, one of cast iron, and one of cast steel, and all 
were models of a propeller which has given excellent results in actual service on a 
battleship. The appearance of these models is shown in Figs. 2 to 5, Plates 63 to 66. 
Propeller No. 285 was already on hand. It was machined to a true helicoidal 
surface on the rear face of the blades, and finished by hand to a true surface of 
convex section on the leading face. The accuracy of finish was the same as that of 
the series of propeller models heretofore tested from time to time at the model basin. 
The three cast propellers were supplied through the courtesy of Mr. William Gate- 
wood, naval architect of the Newport News Shipbuilding and Dry Dock Company. 
They were made from a separate pattern and were cast as nearly as possible to the 
finished dimensions of model No. 285. 
The results of the tests are shown in Fig. 7, Plate 68, from which it will be seen’ 
