National Geographic : 1957 Apr
Rome* Italy Naples' Hydrofoil Ferry "Flies" the Strait of Messina BY GILBERT GROSVENOR Chairman of the Board of Trustees of the National Geographic Society ON a recent trip to Sicily my wife and I enjoyed a "flight" in a new hydrofoil ferry, Arrow of the Sun, a winged boat that crosses between island and Italian main land at nearly 50 miles an hour. Photographing the sleek vessel awakened memories. Nearly 40 years before, on a windy day on the Bras d'Or Lakes in Nova Scotia, I had photographed the pioneer hydro foil boat of my father-in-law, Alexander Graham Bell (page 496).* Ever since boats have been known, their designers have struggled with the resistance of a hull deeply immersed in water. The higher the hull rides in the water, the less the drag. Therefore, if by some means the boat can be lifted clear of the sea's sucking em brace, the gain in speed is spectacular. In 1919 Bell's boat, the HD-4, raced over Baddeck Bay at more than 70 miles an hour when riding on her Venetian-blind-type hydro foils. Thirty-eight years later, HD-4's run of 70.86 miles per hour still stands, so far as is known, for this type of boat, although a jet-engined hydroplane has all but tripled it. Naval architect Leopoldo Rodriquez, builder of Arrow of the Sun, kindly invited us to make one of the first crossings on the new ferry, which can carry 75 passengers. As we got under way, the boat rode on her hull like any ordinary craft. As our speed increased, she rose higher and higher, and in less than half a minute we were "foilborne." Page 492 + Arrow of the Sun Starts Like a Boat; Speeding Up, She Flies Clear of the Sea En route to Messina, in Sicily, the 75-passenger Arrow leaves Villa San Giovanni, on the toe of the Italian boot. Getting under way (above), the ferry floats on her hull; within 30 seconds she rises and flies on her foils at 43 knots (below). Two V-shaped foils, shaped in cross section like an airplane wing, create lift by deflecting water flow ing around their surfaces. © National Geographic Society Kodachromes by Luis Marden, National Geographic Staff Palermo* MessinaVilla San Giovanni Reggio Calabria Sicily We headed across the rough water of the strait. Riding high on our hydrofoils, we sliced through the chop with no pitching or rolling. We felt only the slight recurrent bumps of the wave tops. That is the second big advantage of hydro foil vessels: they travel so smoothly that no one becomes seasick, and they can navigate at high speed in seas that keep ordinary craft in harbor. We made the run from Villa San Giovanni to Messina harbor, 4.4 miles, in 5.5 minutes. In regular service Arrow crosses between Reggio Calabria and Messina, 8.1 miles, in 10.3 minutes. Ordinary ferries take 50 min utes for the same trip. Hydrofoils Act Like Airplane Wings Hydrofoil designers use aeronautical terms and speak of "flying" their boats. This is legitimate language: a hydrofoil flies through the water as an airfoil flies through air, pro ducing lift by deflecting the flow of water. There is one big difference between an air plane and a hydrofoil boat. The hydrofoils fly through a medium 800 times as dense as air. This means that comparable amounts of lift can be obtained with very much smaller foils than those used in aircraft. Hydrofoil craft, of course, have some dis advantages. In a following sea, the speed of the wave may exceed that of the foils, allow ing the foils to stall and the boat to "crash," or drop down on the water. To avoid this, the boats may tack like sailing vessels. They are in addition somewhat vulnerable to floating debris, which might smash the foils projecting below the surface. Maneuvering alongside piers or other vessels grows more complicated because of the jutting foils. But the advantages of the design are so attractive that hydrofoils have captured men's * See "Alexander Graham Bell Museum: Tribute to Genius," by The Honourable Jean Lesage, NATIONAL GEOGRAPHIC MAGAZINE, August, 1956.