GEM Research in the U.S. 303 
Illinois. He delivers babies and dabbles in aerodynamics on the side. So, with that as a 
background, these are abstracts from the letter I received from him yesterday: “Since I saw 
you in January 1960 at the IAS meeting, considerable work on Ground Effect Machines has 
obviously been done all over the world. We too have been busy. We now have what we con- 
sider to be the world’s best Ground Effect Machine from the standpoint of control, hill 
climbing, stability and all around utility. We have a 200-hp, four-passenger flying machine 
in the chassis stage and have gotten well along in testing it. We get 12-inch altitude at 
1600 Ibs. gross weight, climb a 10-degree slope and go 50 mph over land or water. I feel 
that with all the theory and experimentation, we lead the world and challenge all comers in 
this category of small personal Ground Effect Vehicles.” 
R. A. Shaw (Ministry of Aviation, London) 
It seems to me that you are mostly ship men here and therefore at a disadvantage in 
assessing the possibilities of what we call hovercraft in England and what you call ground 
effect machines in America. (What you call them on the continent, I have not yet discovered.) 
You are at a disadvantage because you look at them and you think, Reynolds’ number, 
Froude’s number — must explain it all this way.. It isn’t really very helpful in working out an 
understanding of hovercraft or ground effect machines because, perhaps fortunately for 
everyone, the Froude number is not very important as far as ground effect machines are con- 
cerned, at least you soon get out of the regime in which it is important. Perhaps the particu- 
lar case in which it will continue to be important is when your machine enters shallow water 
and does the transition from water to land. Apart from this, as ship people I feel that you 
are at a disadvantage because the problems of ground effect machines are largely the prob- 
lems which have been studied by the aircraft industry in the past. Hovercraft certainly 
stand astride the two fields but a proper appreciation of ground effect machines and their 
future, I think, is easier for the aircraft people who rather rub their hands and say “jolly 
good, this is easy stuff,” by comparison with the ship people who say “what a troublesome 
problem.” It isn’t really easy stuff because there are a lot of very curious things in it. 
What I wanted to bring home to you was that you couldn’t assess it simply by ship stand- 
ards. There are many subtleties in ground effect machines, and to give you an example, in a 
machine like the SRN-1, the British hovercraft, there was more power lost between the fan 
and the ducts than was used in the lifting and propulsion of the machine. This is just part 
of the problem of design, how to use your power effectively and efficiently in a novel way. 
People haven’t got habits of thinking about hovercraft so they don’t naturally choose a good 
solution. We have got to go through that process of finding good solutions and that’s why 
people like Dr. Bertleson, who are following the example of the Wright Brothers and starting 
at the beginning, are just as likely at this stage to hit on a good solution as well-informed 
gentlemen at national establishments. In fact, we are in the pioneering stage and have to 
assess our progress in terms of that stage; it is 1904 as Col. Wosser said. But despite the 
fact that it is only 1904, or perhaps to be precise 1905, we are in England at the moment, 
building a 25-ton hovercraft capable of cruising at about 70 knots and carrying about 50 or 
60 people several hundred miles. This is being achieved within a few years of the concept 
taking hold and within a year or 18 months of our first demonstration. By contrast, in the 
hydrofoil business, hydrofoils have been talked about for a generation and although they are 
now at the 80-ton stage, it has taken a generation to get there. With a background of air- 
craft experience it does look possible to get into the ground effect business in a matter of 
five years. I want to redress any influence which Mr. Chaplin’s final statement might have 
on this audience in thinking that unless you got into the 600-foot or 10,000-ton class, 
ground effect machines have no place, by reinforcing what Col. Wosser said and that is you 
must not consider them in relation to conventional forms of transport on conventional routes. 
