you want curves?

 Picture a large orange or a grapefruit. Now imagine drawing the outline of a guitar body on the surface of the fruit. Now imagine cutting the outline and peeling away the guitar body top. If it holds its shape it will approximate the spherical nature of some guitar archings- often with a radius over twenty feet. Others, like mine aren't actually based on a radius, but on a curve more like the boatbuilder's 'fair curve', or a violin's arching.

The sides of this instrument taper by about 15mm from maximum height at the widest point of the lower bout. This reduction in depth has to accommodate the curve of the back, so the blocks and the outline have quite a subtle and complex path to follow as they make their way around the instrument.

You can see from the angle above that at the narrow waist, the sides need to get higher as they head inwards. It takes a little care.

After the sides are pretty much shaped, the bottom kerfings can be glued in. They are complex too because their journey involves some curving down as well as in and out.

little arches

The back plate here is getting its final scraping to bring it to my desired thickness. This process was pretty much done before jointing, but a further millimetre or so was removed, first with a toothed blade in a small plane, then with the scraper.

Here the concave workboard for supporting the belly while attaching its struts is in the first stages of being carved. First a template of the desired long arch was made, then a plane was used to create that arch on the plywood. The next shot shows the development of the shape with a small flat plane working mainly at right angles to the centre line to create the cross arched profiles. For the back, the maximum convexity of the plate is only about 3mm. The belly and the back each have their own workboard. A template was made for a major cross arch as well as the long one, just to make sure the shapes were true...the rest was done by feel.

 Some luthiers use a developed radius as the basis of the curved back and belly and there is a lot to be said for the thinking behind that, but I've found great pleasure in looking at and making arches for years now, and I've never found a pure geometric shape to look or perform as well as more complex and perhaps more organic curves and combinations of form.....so my arches will look a little less rigid, and a bit more like a hung chain than the surface section of a sphere. The centre of effort on the plate will have an unequal relationship to the various edges, so in my thinking, it should neither be central nor uniform in all directions.

The centre strip that reinforces the spine is of spruce here, with the grain going across the back. Here it is being cut away to fit the cross braces that will run at right angles to the centreline.