6 ‘Trans. Acad. Sci. of St. Louis. 
5. Discussion or [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’ 3 
8(C7R?)? CaP? 
275r 375 
OP ae [XI] 
6. ANOTHER FoRMULA FOR V WHEN WE KNow THE VALUE 
P,, FOR A PaRTICULAR VELOCITY V,, WITH A GIVEN SHIP 
WITH A GIVEN Motror AND PROPELLERS :— 
From [IX] we have 
Substituting this value of P in [VIII] we have 
oe Oe 
H = 5 va( vet 15) ge ae [XIII] 
whence , 
7 io eRe, [XIV] 
(18, 4 22 22) p 
Vir 
The utility of this formula may be shown by substituting 
known values for P,, V,,7, and H’. Thus, suppose P, is known 
to be 650 Ibs. when V,=15 (miles per hour), then [XIV] gives 
for a 85.5 horse-power motor and a propeller area, A= 206 sq. ft. 
== 7 (8.1)? 
(550) (15)? [60] 
( 167/650 , 22 
3 
15X81" 15 
| ) 650 
whence V =13.3 nearly. 
