88 NOTES FROM THE MODEL BASIN. 
signed propeller would never work, it does not seem necessary to replot the curves on the 
basis of thrust instead of slip. If it were done, the efficiency for the cast propeller would 
at all parts of the curve lie below that for the smooth propelier. 
In testing the model of the Neptune in the wind tunnel, the model was suspended as 
shown in the photographs accompanying the paper. With the air in the wind tunnel flowing 
at varying measured velocities, the actual total resistance of the model was measured. From 
this measured resistance was deducted the resistance of the suspension gear and also the 
estimated frictional resistance of the wetted surface, this latter being estimated in exactly 
the same manner as the frictional resistance of water for a ship, the only difference being 
the use of a smaller coefficient for air than for water. Having obtained the net air resist- 
ance of the model in pounds, it was extended to the ship by assuming it to vary as the square 
of the linear dimension and as the square of the speed. This resistance multiplied by the 
speed of advance of the ship in the water gives the additional horse-power required to over- 
come the air resistance. 
It was thought that it might be possible to compute the air resistance of the model by 
use of a formula :— 
FIGS Vie 
in which R is resistance in pounds, K the resistance in pounds of a square foot of surface 
set at right angles to the flow of air, S the total projected area of the ship above the water 
line, and V the speed. The constant K for air is about .0033 pound per square foot. It was 
found, owing to interference caused by one projection masking another, that no apparently 
very consistent ratio between the resistance so computed and that actually obtained could 
be found. 
Tur PreswEeNT:—Does any one else wish to discuss the paper? If not, we will tender © 
to the writer of the paper, Naval Constructor McEntee, the thanks of the Society for this 
interesting paper, to which I am sure he is entitled. 
We have now reached the end of the program of papers for to-day, and the address 
by Mr. W. H. Ewertz on the submarine will not take place until half past three o’clock. 
We will now take a recess until 3.30 o'clock. 
Tuurspay, 3.30 P.M. 
Tue Present :—I have the pleasure of announcing that Mr. E. H. Ewertz is ready 
to make his address and show his lantern slides on the submarine. 
Mr. Ewertz then proceeded to deliver the address on submarines. 
THE PRESIDENT :—I am quite sure you will all agree with me that Mr. Ewartz is en- 
titled to our very sincere thanks for the illustrated lecture on submarines which he has 
given us. All in favor of rendering a vote of thanks to Mr. Ewertz say “Aye”; contrary- 
minded, “No.” It is carried. 
The program for the day is over, and you will be kind enough to come here to-morrow 
at 10 o’clock, and we will start with the second day’s proceedings. 
The meeting then adjourned. 
