RECENT ADVANCE IN OIL BURNING. 167 
Rear ApMmiIRAL Dyson:—I think the majority of you gentlemen are thoroughly 
conversant with the work that I have been doing on the screw propeller for a good many 
years. I have presented to you in various publications from time to time what I thought 
were advances; sometimes they were advances and sometimes later on I had to take 
them back. What I am presenting to you today is my last step, which to my mind 
is very nearly the final step towards results by which the design of screw propellers can 
be brought down to a practical designing basis. The future may open up other steps; 
I do not know. The paper, as I have prepared it, is such that I can only read extracts 
from parts of it. 
Rear Admiral Dyson then abstracted the paper, and during the same said:— 
“T want you gentlemen to understand that in most work on screw propellers we 
find rules for obtaining what they claim will be the successful screw propellers, but we 
do not find any rules whatever telling us what the successful screw propeller will perform 
when the ship is heavily loaded, and in conditions of load that become abnormal. 
“In my work I was driven into the abnormal conditions, on account of having to 
handle submarines, towboats, and now and then I would get hold of merchant ships which 
vary very much from the trial condition down to the seagoing, heavily loaded condition. 
It is a very easy problem to design a propeller for the submarine when you design for 
the surface condition only, but when you realize that the submarine has to run sub- 
merged at times, you must get a close estimate of the actual revolutions which will occur 
under this overload condition to prevent overloading your motor. If you get your pitch 
too high, when you put the full load on the motors, the motors overheat and burn out very 
shortly, and so I was driven to investigate the unsafe range, while the ordinary inves- 
tigator in propellers investigates only in the safe range.”’ 
In connection with a portion of the report reading, ‘‘It has been shown how vessels 
can be divided into three general types,’’ Admiral Dyson said:—‘‘I know with regular 
merchant ships which have a high value of K, when they pass over the slip of the first 
order, and into slips of the second order, they get into cavitation at once. There is 
heavy increase in K, and also loss due to cavitation.” 
In connection with the portion of the paper on page 197 reading: ‘“‘It has been 
stated that with vessels of types 1 and 3. . . gradually pass over from curve 1 to curve 
2..., Admiral Dyson said :— 
‘‘We had a very illuminating example of that in one of the destroyers which we 
tried during the war—a Fore River destroyer. The starboard propeller at full speed 
made between thirty and forty more revolutions per minute than the port propeller. 
No one could understand what caused the difference. The ship was docked and her 
struts examined. The two struts had come from different foundries, and on measur- 
ing them up the starboard strut was found to be twice as thick as the port strut. That 
strut was taken out and reduced to the same dimensions as the port strut. At the 
next trial the propellers ran evenly as to revolutions, there was no loss in efficiency, 
and we got the same speed with the same power the second time as was obtained the 
first time.” 
In connection with the reference to vessel I, Commander Dyson said:—‘‘I was 
very anxious for Commander McEntee to take the model of this ship and run it in the 
tank. ‘The engines were designed for something like 7,500 horse-power and were driven 
up to 9,300 horse-power; the resultant indicated horse-power curves and revolution 
curves were very peculiar and show the best example of cavitation through a long range 
