Hydrodynamics of High-Speed Hydrofoils 143 
which can only be achieved at full-scale, and under these conditions it is very difficult to 
get really systematic measurements under completely controlled conditions. There are very 
few facilities available which can run at sufficient speed to get the correct cavitation num- 
ber and a reasonable approximation to the Froude and Reynolds numbers. We have, in fact, 
been doing some work in the rotating-beam channel at the Admiralty Research Laboratory 
because we can run at large scale and very high speeds, up to 100 knots. There are avail- 
able in the world quite a number of seaplane tanks which are going into disuse at the 
moment and I would suggest that these are ideal facilities for this type of work, particu- 
larly as a lot of them have the ability to make tests in simple wave systems, which is a 
very vital part of the whole problem. I suggest that more use might be made of these facil- 
ities by our various governments for hydrofoil craft experiments. 
Marshall P. Tulin 
I am very happy to hear Mr. Burt’s comment on the effects of interactions on inception 
based upon his own experience and presumably on experimental measurements of cavitation 
inception. With regard to facilities, he has an admirable point with regard to the utilization 
of seaplane tanks where they exist. As I mentioned in my talk, the Hydrodynamics Division 
of the former National Advisory Committee for Aeronautics, now the National Aeronautics 
and Space Administration (NASA), carried out most valuable research on supercavitating 
hydrofoils and other related problems very pertinent to the development of hydrofoil craft; 
we all hope in the United States that those fine facilities which are no longer being used 
for seaplane research will continue to be put to use for high-speed hydrofoil and other 
marine testing. 
Glen J. Wennagel (Dynamic Developments, Inc., Babylon, New York) 
Mr. Burt talked on the further use of existing high-speed towing tanks and certainly 
these should be used. In fact, with the decrease in interest in high-speed seaplanes in 
recent years, perhaps hydrofoils have given these tanks a new lease on life. However, it 
is not always easy to test in the existing towing tank facilities. Sometimes they are far 
away and scheduling difficulties exist. Also, they are expensive. We went, about a year 
ago, to facilities like the Whirling tank and the Pendulum in order to have something rela- 
tively cheap in our own back yard, where we could use relatively inexpensive small models, 
make changes quickly and put ourselves in the right ball park on a hydrofoil or strut design. 
Then we would look forward to using some of the high-speed tanks, such as those at 
Langley Field, Virginia, after a foil design has been optimized. Let me give you an idea 
of the dollars and cents involved here. The whirling tank is worth about 100,000 dollars. 
You can use that amount of money up rather quickly in testing with larger scale models. To 
get the accuracies we wanted, a single model tested at Langley Field was worth about 
12,000 dollars. You do not have to build many of those to use up the cost of a smaller 
facility. 
P. Kaplan (Technical Research Group, Inc., Syosset, New York) 
I have some questions as to the validity of the simple gust-load formula for the g load- 
ing of a hydrofoil system. The numbers appear to be too pessimistic, at least from my quick 
judgement of them, and we must remember the fact that the real hydrofoil craft is a coupled 
