Abstract: This invention provides for a new design of recreational water boards that are significantly more stable than traditional boards in the class of standup paddle boards, windsurfing boards, and surf boards. Higher stability is achieved by shifting the primary buoyancy of the board to the “rail hulls” located on each side of the board deck creating a tunnel-hull effect. This provides a unique ability to make the board more stable for the average or beginner rider. This new design is intended to be a multipurpose platform allowing the rider to use as a standup paddle board, windsurf board, and surf board. In addition because the design is very stable it can be configured with a removable seat to allow the rider to paddle while seated. The increased stability provided by the tunnel hull effect also eliminates the need for a fixed rudder or fin to generate directional stability.

Abstract: A lightweight, small size, high sensitivity gauge for indirectly measuring displacement or absolute gap width by measuring axial strain in an orthogonal direction to the displacement/gap width. The gap gauge includes a preferably titanium base having a central tension bar with springs connecting opposite ends of the tension bar to a pair of end connector bars, and an elongated bow spring connected to the end connector bars with a middle section bowed away from the base to define a gap. The bow spring is capable of producing an axial strain in the base proportional to a displacement of the middle section in a direction orthogonal to the base. And a strain sensor, such as a Fabry-Perot interferometer strain sensor, is connected to measure the axial strain in the base, so that the displacement of the middle section may be indirectly determined from the measurement of the axial strain in the base.