Marking out Curves

Copyright © 1999 Howard Coleman (text and software).

In guitar making, accurately drawn curves may be needed for:

• The braces that hold the required amount of arch in the top and back.
• Curved templates to enable the maker to measure accurately the amount of camber on a fingerboard.
• Jigs to make dished work boards of the right radius to support the top and back during construction.

What is the best way to mark them out? One way is to use a piece of string or wire with a pencil attached to the end but, for a 25-foot radius, this can be cumbersome and subject to variable amounts of stretching. Another way is to take a straight rod and bend it the right amount. The trouble with this is that the curve it gives is not circular - most of the bending occurs toward the middle. One solution is to go back to the old geometry lessons from your schooldays and, putting the right formula in a spreadsheet, plot the positions of all the points along any curve you want. From there you can make templates so that you will never need to mark out another piece of wood that way again.

Or, rather than doing all that geometry and computing, why not use my spreadsheet? Here are some different versions. This diagram should explain how to use it.

• Curves spreadsheet for Excel 97
• Curves spreadsheet for Excel 5.0/95
• Curves spreadsheet for Excel 4.0

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Last revised: November 01, 1999.