6 Trans. Acad. Sci. of St. Louis. 



5. Discussion of [XI]. 



Given H', C, R, and r for a Given Ship and Motor, What 

 Speed can it Attain in a Still Atmosphere? 



Solving for V we have 



H' 



275r "^ 37T 



.[XII] 



6. Another Formula for V When We Know the Value 

 Pj, FOR A Particular Velocity V^, with a Given Ship 

 WITH A Given Motor and Propellers : — 



From [IX] we have 



p 72 p 



— = — . or P=— • 72 



Substituting this value of P in [VIII] we have 



whence 



P, /161/P, , 22\,,, 

 ya = __J50TViL_ [XIV] 



The utility of this formula may be shown by substituting 

 known values for Pj, Fj, r, and H'. Thus, suppose Pj is known 

 to be 650 lbs. when Fi=15 (miles per hour), then [XIV] gives 

 for a 85.5 horse-power motor and a propeller area, A = 206 sq. ft. 



-7r(8.1)=^ 



^,,^ (550)j(15)n60] 



/161/650 22\ 

 ll5or8"l + i5r^^ 

 whence 7=13.3 nearly. 



