A conventional sail is typically flexible and used by boats and/or small recreational land vehicles to provide forward movement. Conventional airfoils are typically made from a rigid material and are used by vehicles predominantly to reduce drag.
U.S. patent application Ser. No. 12/023,622 entitled Truck Streamlining and Ser. No. 12/384,875 entitled One-Piece Aerodynamic Truck Bed Enclosure are exemplary of conventional airfoils.
Many large trucks employ single wheels with oversized tires on both the tractor and trailer/bluff in lieu of a dual wheel configuration. While more expensive, the oversized tires are more fuel efficient than multiple thinner tires. Additionally, many trucks employ a “skirt” affixed under the trailer. The purpose of this “skirt” is to keep air that has been deflected by the tractor from having to again be deflected by the rear wheels of the trailer. Thus, recent innovation for large trucks tends to revolve around increasing fuel economy/efficiency.
Conventional airfoils are predominantly configured to reduce drag and thus increase fuel efficiency. A by-product for some airfoils is that they produce some lift as well, which also adds to fuel efficiency. But conventional airfoils are constructed of relatively rigid materials. On a low vehicle such as a car or pickup truck adding a relatively rigid airfoil does not present a problem. However, on larger vehicles such as semi-trucks, box trucks, busses and recreational vehicles, the added height of the airfoil poses a potential problem when driving under an overpass or street sign, etc. Since conventional air foils are made from relatively rigid materials, adding such an air foil to a truck or bus could also pose a safety risk.
It would thus be advantageous to create a sail that could be attached to a vehicle that provides lift like an air foil but is flexible to minimize the additional dangers associated with driving under overpasses or other height related obstacles.
It would also be advantageous to provide controls for adjusting the amount of lift provided by the sail.