Shaping the Spruce Bass Bar
Prior to today's work session Ben completed graduation of the maple back as well as selected a piece of spruce comparable to that of the top for the bass bar and fitted and glued it to the top.
The bass bar supports the bass of the violin top. It is not intended to add mass but rather to provide length wise strength/stiffness to the top and support the bass side foot of the bridge. The treble side of the bridge is of course supported by the sound post. When the bass bar is finished the tap tone of the top is normally F to F#. The length of the bass bar is fitted to the individual instrument and usually will be about 40mm shorter on each end than the violin.
The rough shaped spruce bass bar as clamped and glued to the top
Here Ben begins the planing to shape the bass bar.
At this point Ben checks the rough height of the bass bar which will be planed down to about 14mm in the center.
Using dividers the bass bar is marked into 4 equal parts on each side of the center point.
On the left is a photo of Ben's notes showing the diagram of the the segments and the height he will plan to at each marked point. The bar is shaped into a beautiful symmetrical somewhat bell shaped curve with the center point being a maximum of 14mm gradually sloping downward to heights of 12.8mm, 10.2mm, 7.6mm, and at the very end 5mm.
Ben checks height measurements at each point as he shapes the bar.
Here Ben uses a finger plane to shape the downward slope at the bottom of the bar.