New model development

I have, in the past, made stringed instruments entirely 'freehand', without bending forms, soleras, side moulds or other tooling. Building in this way allows a lot of design freedom but isn't particularly suited to the production of a model series. So most builders use some simple tooling when building a series of similiar instruments. In this note, I'll illustrate how I produce the moulds and forms for a new model, a Nunes style concert ukulele. This model isn't meant to be a historically accurate reproduction. Instead i'm borrowing some of the design clues, particularly the body shape and size, from Leo Nunes but hope to give it my own sound and feel.

After developing a full sized paper design/drawing of a new instrument, a body outline template is made in thin plywood, heavy cardstock or other suitable material. The template will be used during production of the forms and whenever building an instrument so it should be accurate and durable. It is useful to write basic instrument measurements such as sound hole size and location, body depth, scale length, side length, bridge location and other information on the template for convenient future access.

Before i build the first model of a new instrument, I produce a side bending form, a solera and body moulds. For an instrument the size of a Nunes concert, these can all be produced from a single 1" x 8" x 6' board of poplar, aspen, clear pine or other similiar wood. I'm using aspen because nice, straight and clear boards are available inexpensively at my local Lowes store.

For this instrument, i cut 4 lengths of aspen long enough to accomodate the body lenth of the concert plus a couple three inches. After sanding flat in the drum sander, these 4 pieces are assembled using a few small judiciously placed pieces of double sided carpet tape into a single block of wood.

The body outline is traced on to the block of wood using the template, and the block is sawn to shape on the bandsaw.



The pieces are then separated with a flat knife and the tape removed.



I cut small spacers of aspen on the bandsaw then assemble, glue and clamp the body mould pieces. The bending form pieces are assembled, glued and clamped. Be sure to align all pieces squarely.



In the Spanish style of building, the instrument is constructed on a dished workboard, or solera. The solera is assembled from aspen, glued and clamped. When dry, it is reinforced with cross braces glued to the bottom. Any required dishing is carved in the area of the lower bout.




The body mould parts are keyed to the solera with dowel holes. Here you can see the holes being drilled using the drill press. These dowels allow the builder to accurately assemble and easily disassemble the mould as necessary. Next, the upper bout of the mould will be cut to provide room for passage of the neck.



Holes for the insertion of small clamps are drilled in the side bending form. I use forms like this with a special purpose electric heating blanket and stainless steel slats to bend sides.




Here you can see a Honduras mahogany soundboard for the Nunes concert that i've just profiled on the bandsaw.


My forms and moulds are ready. I'm going to build the first one in the series using some nice slightly figured old growth Honduras mahogany. The soundboard is profiled, it has been inlayed with a Paua abalone rosette, and it has been graduated. In this photo you can see it face down on the solera on a piece of waxed paper, ready for bracing.



Clamping fan braces to a soundboard has always been a little tricky because commonly available clamps aren't very effective. When i make the solera, i install pronged T nuts to accept 1/4" threaded rods. The T-nuts make it easy to quickly attach and remove a clamping deck to the solera. In this photo, you can see the deck on the solera, and the fan braces held firmly against the sound board while the glue dries by bamboo skewers, available at most grocery stores.



Here you can see the body mould attached to the solera, the neck glued to the soundboard, and the sides fitted and glued to the foot of the neck and the tailblock. It is ready for back and top linings.



I this photo you can see the top linings. A section is held in place with bamboo skewers while the glue dries.



Fast forwarding just a bit ... the back linings have been glued, the back profiled, graduated, braced, fitted to the sides and glued. When the glue is dry, i'll remove the instrument from the solera and cut the ledges for the top purfling and body binding.

More soon ...