Design Aspects, del Gesu

Now I hope that apart from the differences, notably the corners, you can see the striking similarities in the outline of the two instruments. The Montagnana is about 5mm longer than the del Gesu, but the proportions are almost identical. The biggest difference is that the del Gesu is a little wider across the c-bouts. The upper corners are also located higher up on the violin.

I base all my violin drawings on the mold length. Add the rib thickness, and the overhang, and multiply by 2 and you have the lengths and widths. I can't imagine that they ever drew it up from the outside edge. That just happens, and can be adjusted later if you have to. First the del Gesu:

It is a small instrument, and the small overhangs, and thin edges make it seem smaller. No, I haven't ever seen it. I've never seen anything. In contrast to other del Gesus, the edgework is not dug in. He decided to leave the whole edge a mm or so thinner, and then he didn't have to dig it in. Makes sense to me. I always see del Gesu instruments as having a lot of recurve. They certainly don't have the straight to the edge arch like a Guadagnini does. Taking the cross arch templates you can figure out where the catenary curve that forms the framework for the arching starts. Put a few dots on the drawing and blend them in. That's where it all starts.

The long arch for the back is simple enough. Two arches from each end that don't make it to the other end. This leaves an area that gradually gets shallower to the middle. That is how the center of the back gets thicker. The belly long arch is different. I can be a straight catenary, a cross catenary, or made similar to the back, with the center deepened. Guadagnini used the straight catenary. Stradivarius a cross catenary, and del Gesu looks to me like he used the third method. The problem with that one, is that relatively long, slightly curved center area is weaker from the thinning, than a thicker back would be; the full length long arch is not there. There again, the weaker arch lets the belly move more easily, for more sound. It can be made thicker, and still get movement, but make it too thin and it will warp. That area is basically supported by the bass bar and sound post.

I start with a triangle that defines the corners. The base of the triangle is always a ratio of the length. A common one is .618, the golden ratio. That's what this one, and the Montagnana use. Then the apex: this one is 2.25 times the length. Montagnana uses 2.75 times the length. The locations on the centerline for the bout centers and the corners are all ratios as well. This one uses .8 lower bout, .6 lower corner, .333 upper corner, and the c bout is 3/8's down from the upper corner to the lower one. The upper bout is .53 down to the upper bout from the top. The widths are ratios as well. The lower bout is tan 30, the upper .8 of that, and the c bout is about half of the lower.

For the f holes a triangle is built. The base of both of them is the lower bout centerline. The apex of this one I couldn't figure out what it was. I drew it up using the dimensions given. When I drew up the Montagnana I had my answer, it is .63 up from the bottom. That is the sine of the angle that has .809 as its tangent. That is 1/2 of the inverse of .618, and .809 is used on everything on the Montagnana. The lower eyes are set .618 down. The uppers are usually set to be somewhat below the narrow part of the c bouts, and wide enough apart to get the bass bar in the right place. A circle drawn from the lower eye crosses the centerline at the stop, and goes through the upper eye.

It's a working drawing, so it isn't pretty, but it shows me just about everything I need to build the body, at least get me started on a mold. I have to finish up archings, and neck and string angles yet. Next, the Montagnana.