Ships – Hull or hull adjunct employing fluid dynamic forces to...
Reexamination Certificate
1999-08-04
2001-08-21
Sotelo, Jesus D. (Department: 3617)
Ships
Hull or hull adjunct employing fluid dynamic forces to...
Reexamination Certificate
active
06276293
ABSTRACT:
The present invention relates generally to hydrofoil structure mounted on marine craft through which hydrodynamic forces are generated during propulsion within a body of water.
BACKGROUND OF THE INVENTION
Marine craft such as high-speed racing boats undergo travel with respect to a body of water which involves both straight runs and 180 degree maneuvering turns. Such turns induce sideway skidding of boats provided with submerged hydrodynamic devices as well as a water surface piercing strut or skidplate through which skid opposing side forces are produced in an effort to avoid sideway skidding experienced at side slip angles of 35° to 45° resulting from centrifugal force produced during typical turning maneuvers. Large drag forces are imposed on the skidplates as well as the rudders by such maneuver activity, to reduce propeller thrust causing significant speed loss as the craft comes out of a turn.
Typical skidplates heretofore utilized had symmetric profiles on opposite sides thereof so as to avoid generation of side force during straight course run. To minimize drag resistance, the typical profiles of such skidplates were in the form of thin flat plates having a wedge formation at its leading edge. Although the use of camber section foils for such skidplates was considered, it was deemed unsuitable because of the large lift coefficient involved during straight line run at a zero angle of attack associated with generation of an undesirably large side force. Accordingly, it is an important object of the present invention to provide a skidplate having profile sections which perform like a camber foil to produce side force only when needed during turn maneuver, and yet perform like a symmetric foil during straight course run without reliance on corrective action of control devices.
SUMMARY OF THE INVENTION
In accordance with the present invention, a skidplate having a symmetric wedge formation at its leading edge, is provided with a non-symmetric arrangement of different profile surface sections extending rearwardly from the wedge formation on opposite foil sides of the skidplate to produce a skid-opposing side force only from one of the foil sides during establishment of a fully ventilated cavity enclosing only the other foil side of the skidplate, such cavity being formed by a water streamline extending from the wedge formation during turn maneuvering travel. Smaller ventilated cavities of equal size are formed on both foil sides of the skidplate by water streamlines produced during straight line travel of the skidplate, so that the profile surface sections on both foil sides of the skidplate then act like symmetric foils to avoid generation of any side force. The different surface profiles of both foil sides of the skidplate include surface sections spaced apart by a maximum amount equal to or greater than the width established by the wedge formation at the leading edge. Such profile surface arrangement is responsible for more efficient generation of lift force generated during skidplate travel, as compared to flat surface sides of conventional skidplates heretofore utilized.
REFERENCES:
patent: 3915106 (1975-10-01), De Witt
patent: 5551369 (1996-09-01), Shen
patent: 450880 (1913-04-01), None
Peterson Frank B.
Shen Young T.
Shuster Jacob
Sotelo Jesus D.
The United States of America as represented by the Secretary of
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