6 Titans. 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 



V=/ ^ \ [XII] 



SjCTrR^y- CttR? 



275r "^ 375 



6. Another Formula for V When We Know the Value 

 Pj, FOR A Particular Velocity Fj, with a Given Ship 

 with a Given Motor and Propellers: — 



From [IX] we have 



p V2 p 



— = — or P=—' V'^ 



Substituting this vakie of P in [VIII] we have 



whence 



y. = ^ 5507,^7/' [XIV] 



/161/P, 22\ 

 \ V,r ^ 15/ ' 



The utihty of this formula may be shown by substituting 

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

 to be 650 lbs. when yi=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)_(15)^ [60] 



/161/650 22\ 



Ii5x8:i + isr^o 



whence 7=13.3 nearly. 



.V.'.^l^... 



