Day 19 The bass bar
Today violin maker Derek Roberts makes the bass bar and fits it to the inside of the front plate.
The bass bar is a reinforcing strut which is fixed inside the front of the violin and lies under the line of the G string. It strengthens the front plate and helps transmit low frequency vibrations from the string to the body of the instrument.
The bass bar is made from quarter sawn spruce. It has been roughly prepared to the correct dimensions. Now it has to be accurately fitted to the internal curvature of the front plate. Left, Derek is marking the curve on the bass bar.
Small pieces of wood have been glued temporarily to the inside of the plate, to ensure that the bass bar is always correctly positioned while it's being fitted. They will be removed after the bass bar has been glued in.
Derek uses a technique called chalk fitting. Here he applies chalk to the inside of the plate along the line where the bass bar will be fitted.
Then he places the bass bar in its correct position, rubbing it against the plate. The bass bar will pick up chalk from all the points where it is making contact with the plate.
Only part of the bass bar is making contact. Wood must be removed from the bar where the chalk has marked it, so that it will eventually make contact down its whole length.
Derek uses a chisel to remove the chalked wood, and a scraper to make fine adjustments. Then he repeats the process of fitting to the plate and checking for chalk marks.
Eventually the whole of the bass bar picks up chalk, showing that it is making a good fit. Derek cleans off the chalk from the front plate before glueing.
Finally the bass bar is glued in place and cramped up.
In the next stage Derek closes the box.
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