212 THE PROBLEM OF THE HULL AND ITS SCREW PROPELLER. 
Use D, in obtaining the pitch, and then proceeding to the apparent slip, use 
the uncorrected value of I. H. P.,’ or S.H..P,'. Use this slip in obtaining the 
revolutions for the propeller with diameter D,, then corrected revolutions equal— 
R, (corrected) = R,;'X (2) : 
When the basis of design is engine power instead of effective, the power must 
be reduced as follows: 
I. H. P.,'=engine power. 
Form 2: “Broad Tip.” 
(Diameter possiblens es aEmanar D D D (Constant) 
(2) D,=Assumeddiameter>D........ I 2 3 (Variable) 
(CON DME D)) Mav aM isla elias Soe AM vale ahaa f6 ar I 2 3. (Variable) 
CA) WD eID) EN MTN CY A Ne MING i eee a I 2 3 (Variable) 
(5) e. h. p,.=e. h. p. (actual X (D,+D)?. I 2 3 (Variable) 
Use D, and e. h. p., in designing the full diameter propeller. Calling the speed 
of ship v, then by the regular method of design, using e. h. p., for v, the derived 
power for the full diameter propeller required for the speed v will be I. H. P.z, and 
the actual power required for the reduced diameter propeller will be— 
D 2 
Te 1a eh a et, We ey 
BL Py BL Papo 
The actual revolutions will be— 
i 
R,=Ri, (estimated revs., full diam.) X (2) : 
Where the engine power forms the basis of the design, this power should be 
multiplied by(2:)’ for the power to use in obtaining the full diameter screw. 
Such broad tip propellers have one peculiarity, so far as can be ascertained, 
and that is encountered when they are used on submarines having slips of the first 
order: 
When running on the surface, the revolution correcter is (2) as given above. 
When running submerged and plotting below curve B, Fig. 7, this factor changes 
D3 
to (2). 
The paper as submitted embraces the results of many years of study by the 
author so far as what may be considered orthodox forms of hulls with orthodox 
propeller conditions are concerned. The questions of small diameter propellers 
CONCLUSION. 
