168 RECENT ADVANCE IN OIL BURNING. 
of any ship I have any record of. I was anxious for Commander McEntee, when he 
was at the tank, to take the model with the model screws, run her through the ranges 
we have been running through in actual trial, and see if we could not get some cavita- 
tion data from the tank, but his time was too fully occupied for him to take it in hand.” 
At another point:—‘‘In designing propellers for a shipbuilding company you ask 
your client what minimum speed under full load he expects to make. The answer 
is: ‘That does not make any difference. The guarantee is on the trial conditions.’ 
The screw you need for the light-trial condition is not the screw you need for deep-load 
conditions. I can give you a screw for trial conditions that will show a very high 
efficiency, but when you load the ship down and go to sea that screw will go to pieces the 
first time you strike heavy weather or the ship’s bottom gets foul—any adverse. condi- 
tions at all will knock it to pieces.” 
At another point :—‘‘Many people have an idea that, because a tugboat has a very 
full, big-shaped blade, it is just because it isa tugboat. Notso. It is because it must 
put so much effective horse-power through that screw on a very small diameter, its 
diameter being limited by the draught of the tug, and it drives you into the broad, fan- 
tail blade. You cannot get away from it. 
