254 H. von Schertel 
1957 Messina-Taormina P20 
1957 Messina-Liparian [slands-Palermo PT 20 
1959 Venice-Trieste PT 20 
1958 Lake Garda PT 20 
1960 Naples-Capri-Ischia PT 50 
1959 Maracaibo-Cabimas (Venezuela) 3 PT 20 
1960 Stavanger-Bergen (Norway) PT 50 
1960 Stockholm-Mariehamn (Sweden-Finland) PT 50 
_ Buenos Aires-Montevideo 2 PT 50 
The most prosperous services exist between Maracaibo and Cabimas and between 
Naples and Capri. On the first mentioned line two PT 20 boats carry an average of nearly 
1700 passengers daily and over 600,000 per year over a distance of approximately 20 miles. 
The shipping company was able to amortize the two vessels within one year. On the 
Naples-Capri line, operated with a PT 50, passenger fees had to be raised on account of an 
excess of passengers. A second PT 50 has been ordered and two PT 20s have been sent 
to Naples in the meantime to assist in operations during the season. A second PT 50 was 
also requested for the Stavanger-Bergen line only two months after its inauguration. 
On many occasions Supramar boats had the opportunity to demonstrate their seariding 
qualities under very severe weather conditions. Soon after establishment of the PT 50 line 
at Naples a heavy storm caused the 500-ton ferryboats to discontinue their trips between 
Naples and Capri. The PT 50, however, maintained its service in an overloaded condition 
carrying 170 passengers instead of the regular number of 140. On another occasion a PT 20, 
passing through the Straits of Otranto was forced down by waves of an estimated height of 
13 feet but short length. It was still possible to maintain an average speed of 15 knots. In 
the Caribbean Sea another PT 20 got caught in the fringe of a hurricane and was able to 
continue her journey in half-foilborne condition in long waves averaging 16 feet in height. 
As regards maintenance, inspections are undertaken at regular intervals of about 2 to 3 
months, including cleaning of hull, bottom, and foils. In a tropical climate, where intensi- 
fied growth of barnacles affects the drag of the foils, more frequent inspection and cleaning 
is indicated. If the foils are not retractable, this work is usually carried out by aqualung 
divers. Disregarding major machinery overhaul, which is normally due after 5000 operating 
hours, the maintenance of the foils requires about 25 percent of the maintenance work of the 
entire boat. 
Strength and reliability of the foil system was several times demonstrated when boats 
ran aground and were still able to continue operation. A boat colliding with a pier caused 
considerable damage to the latter while suffering only minor deformations of the plating 
around the foil suspension point that did not interrupt service. 
PROBLEMS OF ECONOMY IN COMMERCIAL HYDROFOIL OPERATION 
Six years of experience in public passenger service with hydrofoil boats proved that 
the commercial application of this type of craft is very profitable in areas with an adequate 
passenger frequency. Similar to air transportation the comparatively high speed of hydrofoil 
boats in relation to other waterborne craft results in a high earning power. Since the 
present foilborne craft usually operate at speeds up to 3 times that of other boats, their 
potential carrying capacity is up to 3 times greater. In other words, a hydrofoil boat can be 
considered to be equal in capacity to a ship up to 3 times its size. 
