Looking at their largest versions, these huge craft, weighing 265 tons and powered by four Rolls-Royce modern engines, could in reality carry over fifty motor vehicles and more than 400 travellers at sixty five knots. At this rate of speed the uk channel voyage by operators such as
Hoverspeed was reduced to a measly 35 minutes. In the peak of the late 1960s and early seventies, the various Hovercraft ferry service providers (with companies such as Hoverspeed and Hoverlloyd), were carrying as high as 30% of all of the uk channel travellers. Small hovercraft for sale didn't appear for some 40 years. Such was the charm of this especially English technical marvel that one of the hovercraft appeared in films.
He theorized that, if perhaps air were instead directed beneath the hull via a narrow slot running entirely around the periphery, the air could circulate toward the middle of the hull, forming an external phenomenon that would successfully confine the cushion. This system is recognized as peripheral jet. Once air has built up beneaththe craft to a pressure equaling the craft weight, incoming air has nowhere to go but outward and experiences a sharp change of velocity on striking the surface. The momentum of the peripheral jet air keeps the air cushion pressure and the ground clearance much higher than it might be if air were moved straight into a plenum chamber.
To assess his theory, Cockerell created a piece of equipment consisting of a blower that fed air into an inverted coffee can by means of a hole in the bottom. The can was suspended over the weighing container of kitchen weighing scales, and air blown into the can forced the pan down against the mass of a variety of weights. In this way the forces involved were roughly gauged. By fixing a second can within the first and pushinh air downwards through the area in between the two, he was ready to show that in excess of thrice the number of weights may be lifted with this arrangement, in contrast with the plenum chamber effect of an individual can.
Meanwhile air travel improved, and pilots fast found out that their aircraft developed better lift if they were flying pretty close to the surface of dry land or sea. It was quickly determined that the superior lift was available due to the fact that wing and ground jointly created a funnel effect, magnifying the air pressure. The total amount of additional pressure was found to be dependent on the design of the wing and its height above ground. The outcome was most potent if the distance was in between a half and one-third of the average front to back width of the wing. Practical use was developed for the ground effect in nineteen twenty nine by a German flying ship, which often realized a substantial gain in efficiency during an Atlantic journey when it flew close to the surface of the sea. Second world war naval survey airplanes additionally utilized the effect to lengthen their flight length.
