THE LAWS OF FLUID RESISTANCE. 



115 



We see then, that with this ship the eddy-making resist- 

 ance is about eight per cent, of the surface-friction, at all 

 speeds. We see further that at eight knots the wave- 

 making resistance is practically nil, that at eleven knots it 

 is only twelve per cent, of the whole resistance at that 

 speed, and that at thirteen knots, which is the maximum 

 speed of the ship, it is seventeen per cent, of the whole. As 

 we go further up in the scale of speed the wave-making 

 resistance mounts up very largely, and at nineteen knots is 

 fully sixty per cent, of the whole resistance. 



FIG. 18. Speed in knots per hour. 



The curve of resistance here given may be taken as a fair 

 sample of those of ships of good build. It maybe said gene- 

 rally that the eddy-making resistance is a comparatively 

 small amount, and that it bears at all speeds nearly a con- 

 stant proportion to the surface-friction. The wave-making 

 resistance, on the contrary, always increases with increase 

 of speed at a more rapid rate than the surface-friction, 

 being generally nil at a very low speed, and becoming, at 

 very high speeds, more than half of the whole resistance. 

 Large ships, however, do not often attain, under steam, 



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