Using Geometry to Approximate Body Shape

[Alan Peterson]

I'm betraying my favoritism of classic Gretsch models by my postings, I realize, but here's where I could use some help: I need a way to apply geometry to analyze and trace the curve of the old Tennessean model ... much in the same way violins can be realized by a series of curves and circles (http://zhurnal.lib.ru/m/muratow_s_w/violin_design.shtml)

Nothing is leaping out at me as being completely obvious; i.e., an arc VS an ellipse, and my attempts at laying a grid over an image of a Tennessean has not resulted in an accurate template at all (thanks to lens distortion).

I could use some guidance in finding a site or a tutorial in which I can get a rudimentary grasp of this technique, no matter how basic. Thanks.

[Dave Stewart]

If you can find a good full front image (shot square on to minimise distortion) and a cad program (I use Turbocad), you can paste the image & probably discover the various arcs/centers involved using a line drawing in an overlapping layer. I just use the line drawing and the drawing tools (bezier curves etc) to recreate & fair the outline ... not really concerned with the math of it.
If you've cropped the image exactly, then enlarged it to fit within a drawn box of known dimensions (eg body length & lower bout width), then your tracings will be to scale & yield accurate dimensions.

[Pat Foster]

I've gotten pretty good results with a camera by stepping back from the target and zooming in, with best results somewhat shy of full zoom, like 2/3 or 3/4 of full zoom.
Also, it helps to place the camera so that it's aimed dead center of the target, the guitar body in this case, with the line of sight perpendicular to the top on both axes. Then I do what Dave suggests.

Hope that helps.

Pat