The bass bar should be located and fitted to the inside of the bellyin a perpendicular position, relative to the belly/rib gluing surface andinclined relative to the centerline. The fixture shown properly locatesthe bass bar while it is being fitted to the belly, maintaining it perpendicularlyand provides a repeated point of departure for fitting.

After graduating the top, lay out the location of the bass bar, allowingthe bridge foot overlap of 1 to 1-1/2 mm, and the inclination with respectto the centerline. Dividing the width of the upper and lower bouts by 14and taking one 1/14th division from the centerline, outboard on the bassbar side at both bouts derives the inclination.

Locate this pointwith a pencil mark. A line drawn from the upper bout point to the lowerbout point establishes the inclination. The bar however, may not necessarily lie on this line but should be parallel to it. Importantly is the relationshipto the bridge foot and perpendicularly with the top gluing surface.

The fixture is made from a ¾" piece of plywood, approximately11" x 16". It has a violin shaped cutout the size of the inside of thelinings. This provides a clamping surface for the belly, the same as when it is glued to the ribs. A rail that locates the bass bar is made from1" stock and is attached to the top of the fixture with an approximateinclination and offset for the bridge foot relationship. It protrudes intothe cutout and shaped close to the graduated surface of the belly, withclearance on the "F" hole side so it doesn’t interfere with the belly. Four legs are fixed to each corner supporting the fixture with belly andclamps attached.

Attach the belly to the underside of the fixture, positioning the pencilmark locations for the inclination and bridge foot relative to the rail. Clamp the belly with cleats or hold it in place with spring clamps withsoft jaws to prevent marring the edges. Fitting is done by the chalk method.The belly/bass bar area is chalked. The bar is placed against the perpendicularrail and longitudinally located from the top edge of the plate, with pencilmarks at each end. From this point the bar is firmly held against the railand slid back and forth a light amount, say one or two mm, to chalk markthe high spots on the bar. Remove the high spots till a continuous chalkedsurface is evident.

To carry this thought further, one could also adapt a scheme for usingthis fixture to hold the bass bar in place while gluing. There is nothingnovel about this method…just another way to do it.