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SMITHSONIAN MISCELLANEOUS COLLECTIONS 



VOL. 62 



structor J. C. Hunsaker, in commenting on the proofs of this paper as 

 originally written. He further suggested the comparison with line 

 24, which is of peculiar interest as shown by the percentage relation 

 of these values. Investigation of the relation of the two methods as 

 per line 2^, shows that if we confine the use of the " approximate " 

 method to the " corresponding speed," as per the Law of Comparison, 

 the values as determined by Lord Rayleigh's method should be 90.25^ 

 of the values attained by the approximate method, for models one- 

 ninth the full size, and 107;^ for models one-quarter the full size, so 

 that the approximate method which is much simpler can be used with 

 a fair degree of accuracy if we put it in the form — 



Ho = .ooi76K--'"rt 

 This assumes — = .00123 and-- = 13. 



Pi 1'2 



Line 26 gives the head resistance of a plane of the maximum 

 section according to Eiffel's coefficient for flat plates normal to the 

 wind. 



Line 28 gives a fineness coefficient based on the comparison of 

 lines 25 and 26. 



Line 30 gives the value of Kpv^^ for each of the boat models. These 

 " form factors " are of interest when compared with the values of 

 the same coefficients for models of dirigibles in which the form is 

 unrestricted by requirements such as enter into the flying boat prob- 

 lem. Thus, to make the comparison more ready. Table III is com- 

 piled : 



TABLE ITT. 



It thus appears that the N-2 form, while superior in the air to the 

 other flying boat forms, may still be improved, and if the efficiency of 

 the Lebaudy form could be approached its head resistance might be 

 reduced to 68y'g of the present value. 



However, when we come to consider that the total head resistance 

 of the N-2 model is only about 11 # in air at 60 m. p. h., and consider 



