RESISTANCE OF BILGE KEELS. 



Table II. 

 Resistance of Bilge Keels. 



IS 



The quantities in the second and third columns of the above table are read 

 from the thrust curves for the bare hull and for the g-inch keel on Plate 19, and 

 the differences are set down in the fourth column. These differences naturally 

 show some irregularities which I have ventured to fair out. Considering that it 

 takes at least two pounds at the shaft to make it move, the fairing appears to be 

 allowable. The frictional resistance of the keels has been computed for the sev- 

 eral speeds by aid of the equation 



J?,=fS r° = o.oii X 47.84 X F'"* 



and set down in column 6. Anyone who chooses may readily recompute with 

 any other values of coefficient and exponent which he prefers; it will not change 

 the general conclusions. The ratios of the measured and the computed resistances 

 of the bilge keels give the conclusions that are to be drawn from this source. 

 A conservative conclusion from the evidence here presented may be: — 

 For a speed-length ratio of 0.7 or less the resistance of normal bilge keels 

 may be computed from friction only. At larger speed-length ratios the resistance 

 of bilge keels may be half again as much as that computed for friction only. 



