Instructables
Picture of DIY Bass Uke
Being and enthusiast of DIY musical instruments, I have postposed this instructable until having a day off.

What is a Bass Uke?
Merely a copy of the bestseller Kala UBASS, which is a short scale bass guitar in the body of an ukulele. The main component of this special bass is the string material. The strings are based in the silicon strings used by the Ashbory, later evolved to polyurethane strings when Kala launched their Kala UBASS; and Aquila has its own version of these strings called Thundergut.
The idea came to me after seeing a 3/4 classical guitar at a local shop. After comparing side by side with a Kala UBASS, I discovered to my surprise that the scale length (distance between the frets) was the same, so I had a donor to begin my DIY Bass Uke.


Note than this instrument is not a real ukelele, neither the UBASS. When Kala introduced the UBASS, they used an uke body shape because they are a ukulele brand, thus only for marketing reasons.

Materials:
- 3/4 classical or steel string guitar
- Aquila Thundergut set of strings
- Bass guitar tuners

Tools:
- Screwdrivers
- Electric drill and wood drill-bits
- Small rat file

 
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Step 1: Select a good donor instrument

Picture of Select a good donor instrument
IMG_1467.jpg
I found a cheap guitar at 35EUR which had the same scale length of the Kala UBASS, so it was the perfect donor guitar.

Other guitars may work, but the thing is that you must go for a guitar with a suitable string length for the polyurethane strings, or it will not work.

The proper string length is around 560 mm.

hey, where do you get a 20" scale length guitar? I'm wanting to build a ubass and can't find anything that short, even the 3/4 length acoustics are longer. Thanks for any help you can offer!

olivergon (author)  SirCooksalot12 hours ago
The guitar is a classic guitar but 3/4.
THe scale length has not to be exactly the same, but approximately.

Here`s my version. I used a 20' scale length guitar. Thanks for the tips. I have only a problem with the "E String". Its rumbling too much when you play with punch. I will try to file the ramp like you did, or change the strings. I will also put a piezo pickup. I tested with a normal piezo for guitars and could see it works with these strings.

ubass-bassuke-ukulele-bass-custom-n-kala-21376-MLB20209226389_122014-F.jpg

would it be possible to do using steel or nylon bass strings instead?

olivergon (author)  ivebeentotheyear30002 months ago

No, because they are made for longer scale length instruments
qwerty1558 months ago

Hi. Great project! I'm looking forward to getting down to it.

One potentially stupid question... Where you've attached the strings on the bridge: have you drilled holes through the body, fed the strings through and the attached the washer so that it's on the inside of the guitar body? Is that right?

olivergon (author)  qwerty1558 months ago
Yes, thats right!
The original UBASS has the same method for ataching the strings, but it has a lid at the back so you can access the holes from the inside of the instrument.
Groovy instructible mate. I have 3/4 guitar which I was given, it's just sitting around with a broken machine head and a very slightly warped bridge (don't ask how it happened, it was like that before I got it) it's pretty useless as a guitar now, but produces a surprisingly deep tone quite nicely. This might be just the solution for it, I'd love a mini bass I can travel with.
jdlomr9 months ago
Would this conversion work on a full size guitar?? Cause I got a classical guitar laying around with a lot of bass boom but it's 66cm which misses the ubass mark by around 10cm. Will that affect it?
olivergon (author)  jdlomr9 months ago
The problem with a standard classic guitar is the string length which is far too long for the polyurethane strings.
That is the reason for using a 3/4 guitar, having the right fretboard scale.
ragtimelil9 months ago

I butchered the bridge, but otherwise it wasn't as hard as I thought. I'm waiting for the strings to settle so I can actually play it! Thanks for the instructions!

UBass.jpg
smorrise made it!10 months ago

I just finished my own thanks to your guidance. Sounds pretty good. I used a 1/2 size classical guitar. I did install a cheap $15 pickup w/tuner. I cut off the under saddle pickup and soldered on a piezo disc and stuck it to the soundboard inside.

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jaymethunt1 year ago
So, I've been waiting for your video to post comparing the two... I'm looking to do this project so I can play with a soprano and a tenor uke duo and make it a trio.

What were your final thoughts on this?
olivergon (author)  jaymethunt1 year ago
Well, you must consider that this is a bass sounding instrument, not a ukulele at all except for the size. If you want to play professionally I would suggest you to use a UBASS because you will need amplification. If you consider all the work and parts, it would be easier to get a second hand UBASS for the same price and you will end up with a more quality instrument.
How does the finished product sound? And do you know the exact length of the strings?
olivergon (author)  kylerahtjen1 year ago
I don´t hace the strings to measure them, but they are commercial strings from Aquila so if your buy them , you should not have any problem.
olivergon (author)  kylerahtjen1 year ago
It sounds like a UBASS, which is similar to an upright bass when plugged in to an amp, but just louder.
hi and thank you so much! I have a little question :)
the exact length scale must be 56cm? because I have searched at the local stores and the lenght of the 3/4 guitar around here is 58cm, is there any problem with that?
thanks :D
Yeah, I've got some pahoehoe strings, and I've got some bass tuners but as soon as the string wraps round once or twice, it risks flying off. Broken one tuner already because I tried to widen it with some pliers, fun fun fun
mkreidler1 year ago
How loud is this? The U Bass is usually sold as an acoustic electric, would adding an acoustic guitar sound hole pickup work on this?
olivergon (author)  mkreidler1 year ago
Yes, adding a piezo or surface mounting pickup could work, but not an acoustic sound hole pickup since these are intended for steel strings. The UBASS strings are plastic so a magnetic pickup could not make any sound from them.
I'm making my own out of a 1/2 size guitar, only problem I'm finding is the tuning pegs.
olivergon (author)  TheUkulelePanda1 year ago
The tuning pegs I used were standar electric bass guitar, but I had to make the string hole wider since the UBASS strings have a bigger diameter.
Now that is groovy. I cant wait to hear how it sounds. Great instructable chum.
Agreed!
I would love to hear it, it looks great!
Shreddi1 year ago
Do you need guitar with truss rod to deal with stress of bass strings? I don't think some nylon string guitars have them. Just wondering, thanks much for this.
olivergon (author)  Shreddi1 year ago
There is no need for a truss rod since these polyurethane strings are very low tension.
dchall81 year ago
Is there an advantage of playing a bass ukelele over a bass guitar? I'm not much of a musician but I can play patterns with my electric bass. I played the 32-note bluegrass/gospel background pattern (which amounts to about half the bluegrass music ever written) 3 nights a week for 6 months or so, and I can keep up with the basic, 4-beat country dance music. Just wondering if the bass uke plays the same pattern in different keys?
olivergon (author)  dchall81 year ago
The main advantage is the size of these bass ukes, which make them easy to transport. On the other hand, the sound is more like a double bass than like the electric bass.
Do the uke frets match the bass frets? Could I simply tune it in the bass guitar keys? I'd love to have an acoustic bass guitar.
olivergon (author)  dchall81 year ago
The normal ukulele scale length depends of the size: soprano, concert, tenor and baritone. Neither of them has the UBASS scale length.
The problem with the guitar is that the strings are not able to sound an octave lower. For the bass sound you need special strings that are very thick, so you can´t put them straight away in a guitar. If you read the step by step, you might see all the changes that have to be done to a guitar to become an acoustic short-scale bass guitar, or now-a-days called bass uke.