| The top of this AAc-1 is made from Sitka spruce. The timber
is book matched from AAA grade stock and shown here jointed and cut to
shape. |
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In order to achieve a consistent arching. Isolines are transferred
to the top before carving begins. The isolines refer to points of equal height
above the rib. Holes can then be drilled to the requires depth useing a
pillar drill. The waste can then be removed leaving a smooth arch. For a
more in depth look at this process see Carving
the Back
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| The top rough carved. The pencil lines show the thickness of
the top as anticipated when carving begins. The note in the picture
serves as a reminder that the top is at this point still to stiff. This
has been established using tap tones and manual flexing as the carving
progresses.
glitter patterns are also sometimes used to shape the modes of
vibration of the top. They provide a visual record of the manner in which
the top vibrates at differing frequencies. |
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Here the main ring mode of vibration of the top is shown to
be at 238 hz
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| Cutting the F holes in the top frees the plate to vibrate in
a different fashion.
Adding the braces to the top will once again change both the shape of
the mode and its frequency.
The mode of vibration now incorporates the the f holes and the braces.
Here it is found at 228 hz.
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| At this stage the top is ready to be glued to
the ribs. Doing so once again changes the manner in which the top
vibrates. The final tuning of the top is carried out by scraping the
re-curve around the edge of the top and also on the back. Every maker has
different approaches to tuning the plates. Most develop an almost
instinctive feel to the process. It is this process that allows the
instrument maker to maximize the potential of the top and back. |
