North Shore Partners

Donald P Stubblefield

Jerry D Stubblefield

An apparatus and method for reducing surface friction drag on the hull of a surface vessel by entraining air into water flowing in the boundary layer flow along the hull. The apparatus creates a reduced pressure region by diverting a first portion of the flow away from the surface of the hull. An air pocket is formed in the reduced pressure region and a second portion of the flow is directed through the air pocket by nozzles, which acts as a plunging jet and entrains air into the boundary layer.

Apparatus and method for reducing fluid drag on a submerged surface

An apparatus and method for reducing surface friction drag on the hull of a surface vessel by entraining air into water flowing in the boundary layer flow along the hull. A hemispherical protrusion creates flow separation by diverting a portion of the water flow away from the surface of the hull, which results in a reduced pressure region downstream from the protrusion. A vent located on the protrusion allow air to flow into the reduced pressure region. The air in the reduced pressure region is entrained into the water due to turbulent mixing from vortices shed on to the rear of the protrusion.

A snowboard whose base is relatively thick in the mounting zones beneath each of the rider's feet and relatively thin between the two mounting zones. Thus, with normal loading applied through the rider's feet to the snowboard, the board will bow into a reasonably good approximation of an arc having a constant radius. Consequently, the portions of the snowboard coming in contact with the surface of the snow will substantially lie on segments of a circular arc, and the back half of the snowboard will substantially follow in the track of the front half of the snowboard. This is achieved by controlling the flexural rigidity in the mounting zones and in the center section between the mounting zones. The curvature of the snowboard in response to the application of forces by its rider is a function of the Area Moment of Inertia (I) of the transverse cross-sectional areas along the snowboard's length. In turn, the Area Moment of Inertia is a function of the geometry of the transverse cross-section. The invention is principally concerned, therefore, with the appropriate selection of the geometry of the transverse cross-section of the various segments of the snowboard's body.

Snowboard body

A method of making a snowboard or ski so that the bottom surface of the snowboard or ski is capable of bowing into a desired longitudinal curvature, with a circular arc being the preferred shape, in order to enable a &ldquo;perfect&rdquo; turn to be carved. The method comprises the steps of selecting a desired longitudinal curvature of the snowboard during turns, determining the desired curvature of the snowboard at a plurality of cross-sectional portions thereof in order to achieve the desired curvature, and selecting the cross-sectional area moments of inertia at each of the plurality of cross-sections to provide the desired curvature. The thickness of the core of the snowboard is the preferred design variable. The center section of a snowboard designed in accordance with this method has smaller average area moment of inertia than one or both of the front and rear mounting zones. Snowboards designed and constructed in accordance with this method exhibit improved turning performance, particularly in sharp, tight turns.

Method of making a snowboard having improved turning performance

A snowboard is disclosed having two cambers centered, respectively, below each of the two boot mounting zones.

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Lake Oswego, OR, United States of America

Donald P Stubblefield