Kaplan, Sargent and Goodman 
DISCUSSION 
D.S. Blacklock 
Hydrofin 
West Chtltington, Sussex, U.K. 
Mr. Christopher Hook, the inventor of the hydrofin had to 
leave two days ago for England, but he has two friends in this gather- 
ing, Professor Weinblum and Dr. Saint-Denis and I think another 
gentleman was to have come here, Dr. Todd. They all helped Mr. 
Hook in 1951 after he had shown the Red Bug hydrofoil at New York 
Boat Show. Hook believes in trying to learn through the seat of his 
pants : ever since 1944 when he converted a scrap cockpit he has been 
risking his life on hydrofoils with stability devices, and for this he 
deserves a great deal of credit. It is now thirty years since his 3-ft 
hydrofin was tested in the sea near Simonstown Naval Base but with 
the growing importance of Oceanology there is still time for the su- 
periority of his design to be recognised and for large-scale construct- 
ion to be undertaken by France, America and ourselves. 
The paper which we have just been listening to could be entitl- 
ed ''Out of the test-tank and into the computer'’. I wonder whether we 
are better off. Perhaps what we tend to do is to be so dazzled that we 
fail to notice the paramount criterion, parameter or coefficient, viz. 
"low-g stability''. The other eleven factors discovered by the authors 
(or nine factors for their hydrofoil) are irrelevant. What we are try- 
ing to design is a stabilising homeostatic device, something that is 
stable in spite of speed. If now we invert the criterion of stability we 
have one of the two components of a sensible unit for costing sea- 
transport, K/G for ''knots over g-rating'’. What we hope to provide is 
a service, say ton-miles, where one ton provides space for three 
passengers, but people pay not only for a service to get across the 
Channel, la Manche, but also for speed, and speed in rough weather, 
and comfort in rough weather. Garbage IN, garbage OUT and we can- 
not afford to build surface-skimmers on bad criteria. Criteria and 
costing are very important, if you are trying to be commercial. Yet 
another criterion is the smallness of the craft. 
This brings to mind the fact that although the Tucumcari gun- 
boat which has just returned from Vietnam is a wonderful device and 
the films are absolutely superlative, it was so costly and big that there 
is no commercial hydrofoil in the United States at the present time 
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