Making Double Back Ukulele

Currently this is only an idea for a ukulele construction. I do not mean the back wood is laminated but rather two parallel curved back plates are separated, say, at a 0.5-10mm distance. I wonder if this makes sense at all or that would result in a significant improvement to the tone/projection of a ukulele. Perhaps someone has experimented it with ukulele before. The argument is this: The sound of the instrument when played is slightly dampened when the instrument is touching the player's body. The double layer would have one layer touching the player's body while the inner back layer is free to vibrate and bounce energy (air pressure) forward to the ukulele top.

Weighing the proposition

The sound of an acoustic instrument, be that the tone, projection or sustain depends on many many factors. I asked myself if the benefit of producing louder sound, if any using double back construction, outweighs the additional materials and works needed and hence results in a slightly heavier product. The contemplation of building one has been on my mind for sometimes now. If people out there have done this before please share your thoughts with us here. For comparison, we need to build two similar ukuleles using a similar wood combination, except one with double back. Even two similar ukuleles could produce two different sounds. But I shall be looking at projection among others.

The Making: Ukulele fingerboard using CNC router

A ukulele fretboard (also known as fingerboard) is usually specified by it's scale length, the width at the nut (0th fret position) and the width at the 12th fret position. For a standard tenor ukulele they are 431.8mm, 35.7mm and 46.0mm respectively. A typical fretboard normally has 18 or 19 fret slots for inserting the corresponding fret wire. The position of each slot (d) as measured from the nut is calculated using the following formula:


d = s - (s/(2^(n/12)))

where s is the scale length, and n is the fret number. Note that the 12th fret position is half of that scale length. We could easily customize a slightly different scale lengths for a similar body design.

The top surface of the ukulele fretboard may have a radius as normally found in many acoustic and electric guitars. The radius facilitates a more comfortable bar fingering when playing the instrument as it follows natural human fingers in a relax situation. However the radius fretboard renders additional work on the part of the builder.

Other normal features include fret markers, side binding to hide the slot's end, and other optional adornments.
The overall thickness of the fretboard varies between 4mm to 6mm. It is popularly constructed from woods that are stable and strong such as ebony or rosewood. Other woods such as maple may also be used for the construction of a fretboard.

Constructing a complete fretboard is a bit tedious process.
Starting from a fretboard blank, people have successfully employed CNC router to help construct the fretboard. The product will be more precise and reproducible. The method we are employing here is to write CNC codes namely the g-code thus avoiding the use of CAD/CAM software for the design and g-code generation. To ease the development, rather than doing it as a continuous process, we break the process into several small tasks. Each task may be applied independently. For example, fret radius may be used for fretboard that is already been previously slotted (with a fret saw). This will help in the construction as each module may require a tool change with different type and size of router cutting bit.