Length of box is immaterial. The important measurements are:
6" from tail to bridge
13" from bridge to nut
4.5" across at playing zone, or aggressive soundhole cutouts.
1.5" deep is all most human necks can accommodate, unless you are a chest player, in which case you might be able to up to 2" deep. Also, 1.5" is the standard height for chinrest hardware.
I was planning on using the same approach with a removable back, similar to my guitars. How do you install the soundpost and get it to stay in place?
I cut it to fit really really tight, and then held it in place with a drop of crazy glue on the underside of the lid. You have to be really sure where the bridge is going to go, and the soundpost goes just tail-wards of the treble foot of the bridge. You can't fit it after assembly like on a standard fiddle, because the top and back are not arched, so you have to go the non-standard, luthier-cringing, way.
Another question Diane... How precise did you have to be when determining the height of neck where it enters the box with respect to the top of the instrument. I'm thinking in terms of the bridge, which is sitting on top of a flat surface instead of the rounded surface of a typical fiddle. The curvature adds at least 1/4 inch to the thickness of the instrument, so does that mean the bottom edge of the fingerboard above the top of the fiddle has to be approx 1/4 inch less than normal? Or, do you allow yourself the freedom of adjusting the bridge height?
Dave, on that instrument there is very little clearance between fingerboard and top at that neck join. On a standard fiddle is it not quite 1/4". I was able to use a fairly standard bridge, but I got a "tall" one so I had plenty of carving room to get the size I needed. So yes, I was able to compensate for the lack of belly height by lowering the neck relative to the body.
This was a while ago and my recall about these sorts of things gets fuzzy pretty quickly.
Great building pics Diane! The hint with 8° inclination is super, it helped me a lot for my first violins. I didn't use the dowel, instead I reinforced the sides lengthwise (I used wooden rulers from beech). The back (1/5") itself seems to fulfill the same function as the dowel.
I'm happy this group exists, thanks for all the interesting hints.