44 J. D. van Manen 
For ignoring the hard chine planing craft in my discussion | apologize; it would have 
been of interest to make a comparison of this type with the hydrofoil and the GEM. How- 
ever, I have made a rough comparison of lift over drag based on Mr. Rader’s figures. For 
this I took the liberty of interpreting horsepower per ton as shp over displacement and 
applied an assumed propulsive coefficient of 0.5 to get at ehp and drag. This gave L/D 
values as follows: 7.8, 7.2, 6.6, 6.1. These are about in the low hydrofoil range but prob- 
ably exceed what hovering GEMs may be expected to attain. 
With regard to Mr. Newton’s comments concerning control, motions, and performance in 
a seaway for all these craft, I must agree these matters are critical. I support his plea for 
more research in this area. The strength of ground effect craft resting on the water is of 
great importance. Since the weight available for structure in these craft is not great, sophis- 
ticated structures similar to those of aircraft will have to be used. Even with the advanced 
technology of the aircraft industry this problem promises to be formidable. 
Mr. Newton quoted an appropriate piece of poetry regarding the ability of the water 
beetle to stay afloat as long as he did not stop to think about it. I wish to respond in kind 
with a verse which has a similar theme but which bears on a situation we find ourselves 
faced with in this delightful country, namely the quantities of delicious food we encounter: 
“Kat all kind nature doth bestow 
It will amalgamate below; 
But if you once begin to doubt 
The gastric juice will find it out.” 
