412 



HYDKAULICS AND ITS APPLICATIONS 



displacement 3,980 tons, the wetted area is 18,660 feet. The following 

 are experimental results : 





Taking /= '00917, determine the percentage resistance due to frictions 

 and to eddy and wave-making resistances, at 4, 8, and 12 knots. Also, 

 assuming 42 per cent, of energy developed in the engines to be utilised 

 in propulsion, determine the I.H.P. at these speeds. 



Answer. 



(13) In the Greyhound the length of entrance and of run are each 

 75 feet; in the Merkara they are each 144 feet. Determine the 

 " limiting " speed in each case. 



(Greyhound, T03 +/~T50 = 12'63 knots. 



Answer. 



(Merkara, 1'03 J 288 = 17'5 knots. 



Note how these values bear out the abnormal increase in wave-making 

 resistance at the limiting speed as determined in the preceding examples. 

 In the Merkara the wave-making resistance at 19 knots was found to be 

 over 60 per cent, of the total. 



(14) Experiments on a 20-feet model are carried out to determine the 

 probable horse-power required in a ship 600 feet long when doing 24 knots. 

 Determine the corresponding speed of the model, and, assuming the value 

 of / for the ship to be '00910 and that for the model to be '00935, 



