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Some things are so basic that you just never think about them. One of those things for me is how you know when you have a really fair curve on a guitar side/peghead shape/any kind of curve. One of the things that I learned years ago from Charles Fox was to shut your eyes, and take your fingers around a curve. They'll tell you when it's right and when it's not.

Anyway, working on a guitar tonight I was reminded of that really basic but important technique. Whether it be sides, archtop curves or whatever. Sometimes, shutting your eyes down and relying entirely on your sense of touch is a great thing.

Dave

I recently helped a builder with establishing a new shape for one of his instruments. We started with a shape coming out of g-thang and imported into CAD as DXF. I cut a test template straight from the DXF and then later converted the shape to Bézier curves and recut it.

Like you said, amazing how much you can feel the difference running 3 fingertips around the perimeter with eyes closed. The DXF you can almost feel every node you see in the drawing. Bezier is a world of difference.


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Also, turn it upside down and every which way, looking the the curve as you move the item around.

I do a lot of final heel shaping by feel and turning it and watching shadows move over it.

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You can use a batten to create a spline curve which is a more natural shape for a piece of wood to follow. Boat builders use splines (battens) to fair the lines of the hull.

I once apprenticed under a classical guitar maker in the mountains of Andalusia, he had started his instrument making career as a violin maker studying at the Stradivari school in Cremona. It was rare for the lights to be on in the workshop, most often we'd keep the shutters closed with only an angle poise lamp to illuminate the work while frequently adjusting the angle of the light to check for shadows and curves. A very common technique among violin makers.

Upside down, battens, low angle light--all great things! With CAD, Bézier curves do make a big difference too--kinda does the same thing that the battens do in the analog world. At any rate, I don't think you can limit yourself to just your eyes in daylight to get things right. Just like feeling the vibrations in the wood, the resistance to pressure that you feel when working plates--there's a lot that goes into instrument making that can maybe even better be done in the dark.

Dave