Please excuse any mispelling or mistake, I'm french and was taught english a long time ago ...
Step 1: Materials
- 8" tambourine (should cost about $15)
- a block of hard wood (1"1/2 x 2" approximately). I used sapelli, any harwood is fine.
- threaded rod (1/4", 2 ft.)
- aluminium tube (your threaded rod should fit in)
- 1/4" nuts + washers
- a metal piece with holes to make tailpiece. I used a piece of an old construction game called "Mecano".
- 2" of hard wood cleat (1/4" thick)
- plastic guitar saddle
Step 2: Making the neck longer
THE SOLUTION : making the neck longer.
I used a block of hard wood and shaped in to fit the neck heel one side and the tambourine the other side. I used a dremel, various fillers ans sandpaper.
When doing this, you should have in mind that the neck is slightly tilted back on a ukulele, this helps getting appropriate action and intonation. Measure this on the kit you use and try to shape the wood block in consequence.
This piece of wood makes the neck 1" longer. It could be more, since the more the bridge is centered, the best the ukulele sounds.
Advice : you must take care of the wood grain. It's always better to have the grain of the block perpendicular to the tambourine. the piece of sapelli I found was too short to do this.
Since the neck is attached with a nut, the problem is cosmetic, but if you can get a piece of wood allowing this, it will look better and will be more durable.
Step 3: Attaching the neck to the tambourine
I drilled the heel and the hardwood and put two gudgeons to prevent the neck from rotating around the threaded rod.
The aluminium tube is cut to the exact internal size of the tambourine. Use washers everywhere it's possible (better look and finish and preventing loose fixation). Finish by nuts on the threaded rod.
Step 4: Glueing the fretboard
This is how I did.
Finish the neck with sandpaper to get a smooth feeling.
Step 5: Making the bridge
The guitar saddle is cut to length and its side glued on the bridge.
On this peculiar prototype, the bridge is about 1/2" or less. Best height is obtained by trial.
I've tried several possibilities and it appeared that 3 legs bridges work best... At your convenience...
You can find 4 strings banjo bridges on the net, also.
Make slots to hold the strings using a thin filler. Be very careful at this point. Slots should fit the strings exactly for a better sound.
Step 6: Making the tailpiece...
Attach the strings with small knots.
Step 7: Finishing the neck
pegs are mounted in the headstock and nut is put at the end of the fretboard. Don't glue it, string tension is enough to hold it in place.
Step 8: Finished !
Use an electronic tuner to place the bridge correctly (BTW bridge is not glued, strings tension holds it in place). Once done, use a fine pencil to mark the place of the bridge (for further use :)
I've mounted Worth CM strings instead of the awful black strings supplied with the kit.
And this is how the banjo uke sounds like :
The recording is quiet bad, and I'm just an average player, but hope this will give an idea of the uke sound.
Optionnaly, if you want to play your banjo ukulele through an amplifier or P.A when gigging for instance, you can get a piezo transducer jammed between the skin and the central "leg" of the bridge. It works very well when plugged in a D.I box or a mint box buffer (http://www.scotthelmke.com/Mint-box-buffer.html)