Creating the Form and Templates

The next step is to use the outline that I have drawn to create the form and templates.  The form is constructed by gluing plywood to a maple veneer on both sides.  The veneer is primarily for appearance, and I have used a bookmatched flamed maple veneer that was leftover in the shop, which gives the form a striking appearance.  The wood form blank also received a coat of epoxy for protection.  Each of the two templates is made by gluing two sheets of Formica together for stability.  

The wood blank and the two Formica blanks are fastened together using double sided tape, the Mylar drawing of the outline is fastened to the top sheet of Formica using spray glue, holes are drilled for locator pins, and the rough outline is cut with a bandsaw:

The thickness of wood form has been tapered from 18mm on the lower bout side to 16mm on the upper bout side.  This later allows the installation of the linings to establish the rib taper by placing the lower edge of the linings flush with the surface of the form. 

So that the centerline of the mold remains perpendicular to a flat surface for purposes of cutting and sanding the outline (and thus, the edges of the mold remain perpendicular despite the 2mm taper), the mold and templates are attached to a tapered bottom block.

You can clearly see this taper, bottom block, and the “sandwich” of the form and templates here:

 

The purpose of using two templates (one for the C-bouts and one for the upper and lower bouts) is to ensure that the rib corners come out correctly.  Once the outline is sawn and sanded, the top Formica template is removed, and the C-bouts of the remaining template are scribed 3.6mm from the edge, which marks the edge of the mold outline and blocks for the C-bouts.  Then, one Formica template and the wood mold are cut and sanded to this line:

Then, the C-Bout template is removed from the form, the other template is again fastened to the form, and the upper and lower bouts are cut and sanded along the inside line of the outline, which is 3.6mm in from the edge.

This leaves three things: (1) a Formica template of the upper and lower bout outline, with the overhang for the C-bouts remaining; (2) a Formica template of the C-bout outline, with the overhand for the upper and lower bouts remaining; and (3) the wood mold, cut to the outline all around.

Thus, when put together, the two Formica templates form the outline of the instrument, 3.6mm from the form outline (which includes the 1.1mm rib thickness and the 2.5mm overhang):

The corners of the two Formica templates are then trimmed such that the end of the corner on the upper and lower bout template marks the end of the rib point, and the end of the corner on the c-bout template marks the end of the plate corner (note that this is not as accurate as I would like it to be in this, my first, attempt and will need to be adjusted somewhat later).

The final steps are to cut spaces for the blocks and drill clamping holes in the wood form and to give the wood form another coat of epoxy for protection.  Here is the finished form: