Problems of Commercial Hydrofoils 263 
Near the end of the section titled “Present Types of Commercial Passenger Boats” 
Baron Von Schertel listed particulars of the PT 20 and PT 50 Supramar craft. While the 
figures quoted leave no doubt as to the economical performance of such craft in calm 
weather, i.e., their relatively low horsepower for a given speed, it should be noted that the 
maximum speeds quoted are not really high in comparison with modern planing forms and 
the range, in particular, is very limited. 
Now there can be little doubt, I think, that higher speeds will be achieved with the 
larger craft which the Supramar Company are contemplating, but one is left to wonder 
whether they will have the range for open sea voyages as claimed, or the ability to operate 
in heavy sea conditions. 
After listing the existing services the paper states that the craft have demonstrated 
their sea-riding qualities and then goes on to quote three occasions upon which a craft was 
forced down by the waves. In other words it is at least admitted that this type of craft is 
limited by the sea condition. Unfortunately the paper does not say at what speed the craft 
were able to proceed in waves, nor is there any proof of the heights of waves quoted —as 
much as 16 feet in one case. One of the most difficult quantities to estimate, without the 
use of apparatus only now coming into use, is the height and length of waves. I venture to 
suggest that the heights quoted in the paper are heavily exaggerated. 
To emphasize the point I would like to quote an extract from a recent report of David 
P. Brown, President of the Board of Managers of the American Bureau of Shipping: 
“After months of study of plans and design criteria as well as inspection during con- 
struction, the first of several hydrofoil passenger craft is about to be submitted to the 
committee for classification. Requests to class this type of craft were considered favorably 
by the technical committee last autumn, subject to appropriate limitations as to the area of 
operation and indication in the classification symbols that the craft is of special design 
and not comparable to a normal vessel in respect of scantlings and certain machinery 
details. Hydrofoil launches are now being built for use in Lake Maracaibo and in the 
Caribbean.” 
In conclusion may [| repeat the plea | made in the discussion on Mr. Oakley’s paper for 
more research into the seaworthiness of this type of craft. 
H. Von Schertel 
Mr. Newton expressed the view that hydrofoil boats can get into sea conditions in 
which they have to come down onto the sea. The behavior of hydrofoil boats in a seaway 
depends, of course, on the length of the waves, and on the direction of travel of the craft 
relative to the waves. Our experience over more than 10 years shows that the hydrofoil 
craft can run in almost any sea condition, occasionally, of course, with reduced speed (as 
is the case with any type of boat) and in a half-foilborne condition. - Also I would like to 
add that in this condition hydrofoil boats have proved to have superior sea-riding qualities 
over planing boats, owing to the damping action of the foils. This fact has also been 
stressed by Mr. Hook. Conceming speed in waves, comparison runs which have been made 
between our commercial boats and several Navy craft showed that the higher the waves 
encountered the more the difference in speed was in favor of the hydrofoil boat. 
