216 THE PROBLEM OF THE HULL AND ITS SCREW PROPELLER. 
keel. As the propellers of these vessels are, to a great extent, covered by the submerged 
hull, the inference might be that they belong to type 1. 
5. What is meant by a full midship section? Isit one that is as full or fuller than 
the standard as shown on Plate 71, and is a fine midship section one that is considerable 
finer than this standard? 
6. How would Plate 76 be applied to ships of type 2? Although one of this type 
is shown in Problem 1, the method of getting the slip is not explained. 
For a comparison between the results obtained by the methods as shown in this 
paper and in Marine Engineers’ Handbook, I have taken the third ship in Problem 
1. The calculations are shown below. The first column is taken from this paper; the 
second is as calculated by the latter method. 
Sh 18), (Oa) .825 .516 PC, = .696 .606 
K.B.C. = 786 76 Bo ei = S875 3485 
Sy 8, 12s = 6 6 
Blades = 3 3 alr Se 
v = II II 
D = 16.583 16.583 BeV) as VGA ass 
Je = 14.75 14.75 e.h.p. = 1260 1260 
-hp.+E.H.P. = . 36 
a vi Aa ig e.h.p.+E.H.P 3525 361 
Zp Sa ii iy 2.89" 
AES = 6230 5900 K = 1.23 1.18 
IPI, = eA 1670 Sela SS) L@7o 1880 
IS = 83 885 = = 7614 755 
V = 14.45 14.58 Bs =plus .25 2.89* 
L.T.a = 3-09 3-97 S = 126 109 
Pisa 5010 R = 86.46 84.8 
It would appear that when a propeller is to be designed for a ship, where the effec- 
tive horse-power is not given but has to be estimated, or if the value of 2L.A.B.+H is 
not known, the original method is about as good, at least for ships of this class. For 
small single-screw steam yachts, with a large ratio of beam to length and with small 
midship-section coefficient, the method as shown in this paper would, I believe, be deci- 
dedly more accurate. 
Before closing I wish to state that the foregoing questions are asked in order to 
obtain information on the above points, as there is some doubt in my mind, also that 
Admiral Dyson deserves the thanks of the profession, not only for this very valuable 
paper but also for various previous articles that he has written. 
Mr. W. W. Situ, Member:—Admiral Dyson’s paper is of very great interest, 
and his work has been of great value to shipbuilders. At the Federal Shipbuilding 
Company we have been using Admiral Dyson’s methods of propeller design and have 
found certain difficulties which I desire to point out. 
