The Mudcat Café TM
Thread #60344 Message #966001
Posted By: JohnInKansas
11-Jun-03 - 04:04 PM
Thread Name: Building a mountain dulcimer
Subject: RE: Building a mountain dulcimer
Very little "bracing" is used in the typical mountain dulcimer construction. Spline strips are used to join the top and bottom to the sides. These are typically made from wood strips about 1/4 inch square in cross-section, and are cut part way through at abour 3/8 or 1/2 inch intervals to make them flexible enough to "curve-to-fit" as you glue and clamp (with those wooden clothespins) them in place.
You can see how these are applied by looking through the sound hole of most any guitar, although the strips used in dulcimers are usually somewhat smaller than in the guitar.
For the "scratch" builder, 1/4 inch "quarter round" may be available at the local lumber yard, and works quite nicely. If you really want to get "flash" about it, you can steam bend the strips to fit without the slots - but the only place I've seen this done generally was in Chinese mass-produced mandolins.
The only other "brace" commonly used in the soundbox is a peg between the two sides at the "maximum width" point (or points in a double-bout shape). In kits, its main function seems to be to assure that the sides "keep their shape" while you're getting things together, although it may help hold the shape after assembly. If you haven't done a thorough job of "relaxing" the sides to shape when you bend them, they may tend to "unlax" later and "cup" slightly, and the peg helps prevent this. A 5/16 or 3/8 diameter dowel, or similar square "stick" is about right. Many commercial builders omit these "cross-pegs," and it doesn't seem to change the sound when they fall out - as they've done on a couple of "kit" instruments I've observed.
If you use a separate "head" it is critical that it be securely attached to the fingerboard. You want the joint arranged so that the string tension "holds it together" instead of pulling it apart, but the size of the "glue surface" usually available should be more than sufficient in most designs if it fits well before you glue it.
The "one-piece" head and fingerboard used by a couple of manufacturers is structurally very good, but almost requires "banjo tuners" which are significantly more expensive than other kinds - unless you're willing to use a rather odd head shape.
Since the fingerboard and head carry all of the string load - any joints elsewhere that fit well and provide a reasonable "glue line" should be adequate. Everything except "the board" is pretty much "decoration" from a structural standpoint, and no added bracing is really needed.