92 EXPERIMENTS ON THE FROUDE. 
thought necessary to reproduce them here. Instead there is given a trans- 
formation of the curves for A in Fig. 5, Plate 39, in which the values for 
(1—s)? A 
are plotted on the real slips for abscisse. The transformation is as follows: 
1000 P | 
A= ds V2 , (3) 
but 
V.= pr (I1—S) +101.33 (4) 
in which p is the pitch in feet as before stated, r represents the number of 
revolutions per minute and 101.33 is the factor for reducing knots per hour 
to feet per minute. From equations (3) and (4) 
Sas te. 
IOI. X 1000 P 
(1—s)"A= me ae (5) 
The curves in Fig. 4, Plate 38, can be used to determine the real slip 
of the propeller when working astern of the ship, so that the wake may be 
estimated as will be explained later. 
TESTS OF I9QIO. 
The work of our first summer was first to install, adjust and rate our 
machinery and instruments and to learn our limitations, and secondly to 
make tests with the propeller already mentioned for which the dimensions 
are given on page 87. 
From the drawings of the Manning it appeared that the propeller was 
set with its hub 5 inches from the stern-post. Our normal setting of the 
propeller was correspondingly one inch from the stern-post. Tests were 
made also with the propeller-hub, successively 3 inches, 6 inches, 18 inches 
and 30 inches abaft the stern-post. In order to avoid interference from the 
rudder all tests with the three last conditions were made with twin rudders 
so set as not to interfere with the flow of water to or from the propellers 
when the boat was on a straight course. 
The results of these investigations are given by Figs. 6, 7, 8, 9 and 10 
on Plates 40 to 44. The abscisse are the speeds of the boat in knots per 
hour reduced from the time required to run over the measured course, 
as given by thetime pen on the tape or strip of paper from the recording 
device. The revolutions per minute and the thrust were also derived 
directly from that record. 
