Castagneto and Maioli 



Fig. 2 - Lift coefficient at shock-free entry- 

 conditions versus / /c and t /c. 



The same results can be very closely approximated (the error is no more 

 than 0.5% for the ratios of t /c normally used) by 



'L/ 



k/-^U.k/-^I, 



(6) 



K f and K ^ being as shown in Table 3. 



In the practical design of naval propellers, an average value oi k ^^ = 0.75 

 may be assumed for all cases, if preferred, thanks to the very low values of the 

 thickness ratio used. 



From a former work (4), a value of k^ = 1.55 for Karman-Treffts profiles 

 with NASA-65 mean line has been derived. This value is very far from those 

 listed above, which refer, in general, to the foils by now normally used in naval 

 construction, and, in particular, to those employed in the design of the blade 



1024 



