306 H. R. Chaplin 
First of all, I should like to emphasize how important it is that we should not progress 
too far with detailed experimental and theoretical work into the optimum form for resistance 
and propulsion alone. It may well be that many of the configurations so studied will prove 
quite unacceptable from the point of view of stability or seaworthiness. In my opinion, a 
broad, less detailed, study is first required into all aspects of design to determine the 
ranges of the principal dimensions which are likely to prove suitable for a balanced design. 
Second, I would like to support Mr. Rosenthal’s plea for some comments upon stability 
for the various configurations which have been discussed. This obviously is of prime 
importance in operation over waves as well as over calm water, and I would like the 
author’s comments on whether passive stability may be adequate in some cases, or whether 
active stabilizing will always be necessary. 
Harvey R. Chaplin 
I will not reply at great length to the various comments, but will touch just a couple of 
the specific questions. About the optimum plan form for waves, certainly we don’t have the 
answers on this yet but there is a program at the Netherlands Ship Model Basin underway 
now which will give answers having some bearing on this question and other programs within 
the United States too which are touching on this question. The plan form on which most of 
the recent air curtain research has been concentrated has been the plan form of the model 
which the photograph has shown, which is not too far distant from the ship forms and may 
not be totally unsuitable from the standpoint of possible wave impact. The stability ques- 
tion of course, is a very important question and it would be inexcusable not to cover the 
stability if we knew what to say about it. Again on the air curtain, a good bit is known 
about the stability; we know how to stabilize the machine, how to give it some natural 
stability, and we are close to knowing an answer to the question of whether it will be pos- 
sible to have inherent stability or whether it will be necessary to have artificial stability. 
I personally feel that for the air cushion at speeds up to 100 knots it will be possible to 
have inherent stability without the black box. Beyond those two specific points, if I may 
abstract other comments en mass, they would add up to the fact that I have left an awful lot 
out and this is certainly true. I am afraid I cannot undertake to fill in very many of the gaps 
in the limited time that we have. Fortunately, some of the gaps were filled in by the com- 
menters themselves and | thank them for that. Certainly the one thing that I shouldn’t have 
left out is what was pointed out by Professor Wiegel, and this is the wave drag problem 
which bears on the person to whom the Symposium is dedicated. I certainly owe him grati- 
tude for pointing out this inexcusable oversight. As to the title of the paper, I have to take 
my excuse from the fact that, as you know, in the scheme of things, the title and abstract of 
the paper were submitted some months in advance of the paper itself and as is often the 
case, the paper at the time it was submitted was quite a bit different from the way it was 
envisioned at the time the title was submitted. 
