246 H. von Schertel 
described in the preceding subsection and there can also be introduced an additional simpli- 
fied gyroscope control. A trial boat equipped with this new system is at present undergoing 
tests conducted by the Supramar company, and has, so far, been successful. 
Undoubtedly boats with fully-submerged foils will have a large field of application in 
the future in less protected sea areas and as long-distance ferry boats on open sea. But 
their range of operation will always be restricted by their faster competitor, the airplane, to 
which preference will be given in all cases where its travelling time between two points, 
including airport feeder service time, is considerably shorter. 
PRESENT TYPES OF COMMERCIAL PASSENGER BOATS 
In the second part of the paper we will deal with commercial application of hydrofoil 
boats. We shall first regard the type of passenger boats which are at present in operation. 
It is known that the first hydrofoil design which was used in scheduled commercial passen- 
ger services was the Schertel-Sachsenberg type. The reason for the advanced technical 
stage of this system lies in its structural simplicity and the reliability of the surface- 
piercing foils used in this type. Another reason for the perfection of these boats is the fact _ 
that they are the result of organized development efforts which began with the author’s 
experiments in the thirties and which were continued through the following years without 
interruption. Design and construction have always been accompanied by extensive theo- 
retical and experimental research as well as by trials with full-scaled craft. With the con- 
struction of 16 different types and a total of nearly 60 hydrofoil boats to this date, of which 
26 are passenger ferries, experience has accumulated to such an extent that Supramar’s 
engineering staff is in the position to go ahead with the design of larger and faster economi- 
cal passenger craft. 
The predecessors of the present commercial boats were built during World War II. Out 
of the six types which were designed for speeds up to 60 knots we shall mention the 80-ton 
type VS 8 launched in 1943. This craft deserves attention because it was the largest hydro- 
foil boat ever constructed and has not been surpassed even today. It was designed as a 
high-speed long-range cargo carrier for operation between Sicily and Africa. The 105-foot- 
long hull was constructed in light metal alloy. A maximum speed of 40 knots was obtained 
using a twin arrangement of Mercedes-Benz Diesel engines with a combined output of 
3600 hp. Although the corresponding ratio of 45 hp/ton is considered to be marginal for 
satisfactory operation, the boat was nevertheless able to run at 37 knots against seawaves 
up to 6 feet in height and 150 feet in length. 
To date two prototypes find application in established passenger lines, the PT 20 
(a 27-ton boat for 75 passengers) and the PT 50 (a 60-ton boat for 140 passengers). The 
first PT 20 was built in 1955in the Rodriquez Shipyard at Messina. This craft (Fig. 11) 
turned out to be the first of a series of very successful boats, 19 of which have been built 
or are nearing completion. 
The light-metal alloy materials used in building the PT 20 hulls are Al-Mg and 
Al-Mg-Si. Watertight compartments are provided below the passenger decks and in other 
parts of the hull. Several of these compartments are filled with foam-type plastic which 
makes these boats practically unsinkable. 
The engines installed in the PT 20 are supercharged 1350 Daimler-Benz Diesel engines 
of the type MB 820 Db. The reversible gear, placed between the engine and drive shaft, 
represents a special type developed by Zahnradfabrik Friedrichshafen. A 110-hp auxiliary 
