THE PROBLEM OF THE HULL AND ITS SCREW PROPELLER. 217 
First, the method is rather difficult to comprehend and use by the average engineer. 
Second, it is somewhat difficult to follow cause and effect in the design. 
The present method appears to be somewhat simpler than the one we have been 
using. Mr. McEntee has already called attention to some of the points which I have 
noted, but I will give the shipbuilders’ point of view in regard to these. It is appre- 
ciated that propeller designs and investigations are intricate problems involving many 
variables; but, if it were possible, it would be advantageous, first, to simplify the method, 
and second, to connect it more directly with basic science, so that cause and effect in 
the design can be followed and kept track of better by the designer. 
Admiral Taylor’s method is based directly on the scientific investigation, and the 
cause and effect can easily be followed. However, Admiral Taylor’s curves and data 
are not connected with actual performance closely enough, and their value is greatly 
reduced by not having a connecting link between theory and practice. For Admiral 
Taylor’s method more accurate data as to wake and thrust deduction factors would 
be valuable. 
The great advantage of Admiral Dyson’s method is that it is based on actual results 
of the performance of vessels, and therefore gives thoroughly practical results. It is 
needless to say that any method which does not give such results cannot be used with 
assurance. It would appear that both Admiral Taylor’s and Admiral Dyson’s methods 
have distinct advantages. If the advantages of both could be combined, I think it 
would give an ideal basis for designing and investigating propellers. 
THE CHAIRMAN:—Is there any further discussion? Has Mr. Wetherbee any 
remarks he desires to make on this subject? 
Mr. Cuartes P. WETHERBEE, Member of Council:—I have nothing to say except 
to add my testimony to those who have spoken of our great appreciation of what Admiral 
Dyson has done in the investigation of propellers. I do not think I can make any 
comments that would be worth taking the time of the Society. 
THE CHAIRMAN :—I may say, in view of the many inquiries which have been made 
of Admiral Dyson, that he may find it more desirable to make some of his replies in the 
form of a written discussion after he has had opportunity to see exactly what the com- 
ments that have been offered mean. It is difficult to follow them in a verbal discus- 
sion like this. 
REAR ADMIRAL Dyson:—It appears from Commander McEntee’s remarks that 
his only criticism of the results of my years of labor is that they are limited in their range, 
that while they will produce correct results for the actual ship, a propeller correspond- 
ing to the model propellers used by him in the model tank cannot be produced by the use 
of the charts of design. He states that he has attempted to produce such propellers 
and the resultant propellers have had blades of extremely narrow form; in fact, so narrow 
as not to be practical. 
The answer to this criticism of Commander McEntee’s is a very simple one. Com- 
mander McEntee does not know how to handle the charts to obtain the model propeller. 
He evidently entered them with the same load fraction, ope. , and the same speed 
fraction, a as were used in designing the original propellers for the ship. This would 
V 
