208 THE PROBLEM OF THE HULL AND ITS SCREW PROPELLER. 
Formulas for Design. 
Form 1: Data as per (1). 
(@)sol(@required ‘speed)) 2 page ane v v (Const.) 
(2) nXe.h. p. (required eff. horse-power) n Xe. h. p. ae h.p. 2Xe.h. p. (Const.) 
(3) 2 (number of propellers).......... n n n (Const.) 
(enh ps (oni propeller) my neci ete enihiips &, 10 {Db e. hep. \(Consty) 
(5) e. h. p. +E. H. P. (load fractions 
TSEC) | ohm RANT ey wikia Val. 1 Val. 2 Val.3 (Variable) 
(6) v+V (speed frac. for values of (5) ). I 2 3 (Variable) 
Ge EP A (4) a(S) ee ie I 2 3 (Variable) 
(8) eG) ie=-(G) ken Pees bas re een I 2 3 (Variable) 
(9) S (basic slip from hull character- 
TSEICS) We eat eae ah bistrot Ly ve tea SS S) S (Constant) 
(10) D (proposed diameter)........... y D D (Constant) 
(Gor) RES (Bee Ane DOA) ie eine 2 3 (Variable) 
(2.88 XE. H. P.)=+ (Dx V) for 3-bladed propellers. 
1B bag <2, UNG eID), VAN) Ne 491 XE. H. P.)+(D?X V) for 4-bladed propellers. 
(3.84 XE. H. P.)+(D?X VY) for 2-bladed propellers. 
(12) P.A.+D.A. (for (11) Fig. 8, Plate 79) 1 2 3 (Variable) 
(12) = Projected area ratio if the propeller is 3-bladed = Basic. 
(13) 4/3 (P. A.+D. A.)=(Total proj. 
area ratio for 4 blades)......... I 2 3 (Variable) 
(14) 2/3 (P. A.+D. A.) =(Total proj. 
area ratio for 2 blades)......... I 2 3 (Variable) 
(15) P. C. (propul. coef. for (12), (13) 
Covey (ls W) A) ana aed Sang rau gaat I 2 3 (Variable) 
(16) De Pa ey PsP. — Basic 
Toa ern a Myer ee esate I 2 3 (Variable) 
G@7S:) Ho Pi 921. EL, -Ps— Basic 
shaft) horse=powenren esa Aer I 2 3 (Variable) 
(18) Z,=Power factor for = +P 
(GSTS 6) Mead mame ecm Ny uSIO Tae tay Psa I 2 3 (Variable) 
(19) K=Power augment (Fig. 3)...... K K K (Constant) 
(20) He Jal, Jas Ge Sy Sls aS (UI 18 12S 
1O4p) OT 1S, HP! 102, on 
SEW OL POWER che Sia eye een epee I 2 3 (Variable) 
(i) eae =i DIS peedafor (2) sae eens I 2 3 (Variable) 
C2) eS =i (@) nes Wu ak el as Rema (1—S) (1—5S) (1—S) (Constant) 
(23) 2 = ie <i xX 101-33) = (ss: x< 
Gi) P= Pitch eee ee I 2 3. (Variable) 
(24) Zs; = Speed factor for = Fig. 6, 
(CHUTE S0/ TENURE Nc I 2 3 (Variable) 
